84 results on '"Jenel Vatamanu"'
Search Results
2. All-temperature zinc batteries with high-entropy aqueous electrolyte
- Author
-
Chongyin Yang, Jiale Xia, Chunyu Cui, Travis P. Pollard, Jenel Vatamanu, Antonio Faraone, Joseph A. Dura, Madhusudan Tyagi, Alex Kattan, Elijah Thimsen, Jijian Xu, Wentao Song, Enyuan Hu, Xiao Ji, Singyuk Hou, Xiyue Zhang, Michael S. Ding, Sooyeon Hwang, Dong Su, Yang Ren, Xiao-Qing Yang, Howard Wang, Oleg Borodin, and Chunsheng Wang
- Subjects
Urban Studies ,Global and Planetary Change ,Ecology ,Renewable Energy, Sustainability and the Environment ,Geography, Planning and Development ,Management, Monitoring, Policy and Law ,Nature and Landscape Conservation ,Food Science - Published
- 2023
3. Inhibiting manganese (II) from catalyzing electrolyte decomposition in lithium-ion batteries
- Author
-
Jenel Vatamanu, Cun Wang, Lidan Xing, Kang Xu, Jiawei Chen, Mingzhu Liu, Jiakun Chen, Xuehuan Luo, and Weishan Li
- Subjects
Chemistry ,Inorganic chemistry ,Energy Engineering and Power Technology ,chemistry.chemical_element ,Manganese ,Electrolyte ,Decomposition ,Ion ,Catalysis ,Fuel Technology ,Electrochemistry ,Lithium ,Thermal stability ,Graphite ,Energy (miscellaneous) - Abstract
A once overlooked source of electrolyte degradation incurred by dissolved manganese (II) species in lithium-ion batteries has been identified recently. In order to deactivate the catalytic activity of such manganese (II) ion, 1-aza-12-crown-4-ether (A12C4) with cavity size well matched manganese (II) ion is used in this work as electrolyte additive. Theoretical and experimental results show that stable complex forms between A12C4 and manganese (II) ions in the electrolyte, which does not affect the solvation of Li ions. The strong binding effect of A12C4 additive reduces the charge density of manganese (II) ion and inhibits its destruction of the PF6− structure in the electrolyte, leading to greatly improved thermal stability of manganese (II) ions-containing electrolyte. In addition to bulk electrolyte, A12C4 additive also shows capability in preventing Mn2+ from degrading SEI on graphite surface. Such bulk and interphasial stability introduced by A12C4 leads to significantly improved cycling performance of LIBs.
- Published
- 2022
4. Hydrolysis of LiPF6-Containing Electrolyte at High Voltage
- Author
-
Mingzhu Liu, Kang Xu, Weishan Li, Jenel Vatamanu, Lidan Xing, and Xinli Chen
- Subjects
Hydrolysis ,Fuel Technology ,Materials science ,Renewable Energy, Sustainability and the Environment ,Chemistry (miscellaneous) ,Inorganic chemistry ,Materials Chemistry ,Energy Engineering and Power Technology ,High voltage ,Electrolyte - Published
- 2021
5. Fluorinated interphase enables reversible aqueous zinc battery chemistries
- Author
-
Singyuk Hou, Karen J. Gaskell, Michael Ding, Oleg Borodin, Lin Ma, Bao Zhang, Travis P. Pollard, Qin Li, Long Chen, Longsheng Cao, Jenel Vatamanu, Tao Deng, Kang Xu, Xiao-Qing Yang, Matt Hourwitz, Chunsheng Wang, Dan Li, John T. Fourkas, Enyuan Hu, and Chongyin Yang
- Subjects
Battery (electricity) ,Aqueous solution ,Materials science ,Standard hydrogen electrode ,Biomedical Engineering ,chemistry.chemical_element ,Bioengineering ,02 engineering and technology ,Zinc ,Electrolyte ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,Atomic and Molecular Physics, and Optics ,0104 chemical sciences ,Anode ,chemistry ,Chemical engineering ,Plating ,General Materials Science ,Electrical and Electronic Engineering ,0210 nano-technology ,Faraday efficiency - Abstract
Metallic zinc is an ideal anode due to its high theoretical capacity (820 mAh g−1), low redox potential (−0.762 V versus the standard hydrogen electrode), high abundance and low toxicity. When used in aqueous electrolyte, it also brings intrinsic safety, but suffers from severe irreversibility. This is best exemplified by low coulombic efficiency, dendrite growth and water consumption. This is thought to be due to severe hydrogen evolution during zinc plating and stripping, hitherto making the in-situ formation of a solid–electrolyte interphase (SEI) impossible. Here, we report an aqueous zinc battery in which a dilute and acidic aqueous electrolyte with an alkylammonium salt additive assists the formation of a robust, Zn2+-conducting and waterproof SEI. The presence of this SEI enables excellent performance: dendrite-free zinc plating/stripping at 99.9% coulombic efficiency in a Ti||Zn asymmetric cell for 1,000 cycles; steady charge–discharge in a Zn||Zn symmetric cell for 6,000 cycles (6,000 h); and high energy densities (136 Wh kg−1 in a Zn||VOPO4 full battery with 88.7% retention for >6,000 cycles, 325 Wh kg−1 in a Zn||O2 full battery for >300 cycles and 218 Wh kg−1 in a Zn||MnO2 full battery with 88.5% retention for 1,000 cycles) using limited zinc. The SEI-forming electrolyte also allows the reversible operation of an anode-free pouch cell of Ti||ZnxVOPO4 at 100% depth of discharge for 100 cycles, thus establishing aqueous zinc batteries as viable cell systems for practical applications. A solid–electrolyte interphase that is permeable to Zn(ii) ions but waterproof is formed using an aqueous electrolyte composition. Cycling performances in an anode-free aqueous pouch cell show promise for intrinsically safe energy storage applications.
- Published
- 2021
6. Averaged Configurations from Molecular Dynamics Simulations.
- Author
-
K. Gillis, Jenel Vatamanu, M. S. Gulam Razul, and Peter G. Kusalik
- Published
- 2006
- Full Text
- View/download PDF
7. Highly reversible Zn metal anode enabled by sustainable hydroxyl chemistry
- Author
-
Lin Ma, Jenel Vatamanu, Nathan T. Hahn, Travis P. Pollard, Oleg Borodin, Valeri Petkov, Marshall A. Schroeder, Yang Ren, Michael S. Ding, Chao Luo, Jan L. Allen, Chunsheng Wang, and Kang Xu
- Subjects
Multidisciplinary - Abstract
Rechargeable Zn metal batteries (RZMBs) may provide a more sustainable and lower-cost alternative to established battery technologies in meeting energy storage applications of the future. However, the most promising electrolytes for RZMBs are generally aqueous and require high concentrations of salt(s) to bring efficiencies toward commercially viable levels and mitigate water-originated parasitic reactions including hydrogen evolution and corrosion. Electrolytes based on nonaqueous solvents are promising for avoiding these issues, but full cell performance demonstrations with solvents other than water have been very limited. To address these challenges, we investigated MeOH as an alternative electrolyte solvent. These MeOH-based electrolytes exhibited exceptional Zn reversibility over a wide temperature range, with a Coulombic efficiency > 99.5% at 50% Zn utilization without cell short-circuit behavior for > 1,800 h. More important, this remarkable performance translates well to Zn || metal-free organic cathode full cells, supporting < 6% capacity decay after > 800 cycles at −40 °C.
- Published
- 2022
8. Modeling Methods of Ionic Liquids at Charged Electrode Surfaces
- Author
-
Jenel Vatamanu, Lidan Xing, and Dmitry Bedrov
- Published
- 2022
9. A 63 m Superconcentrated Aqueous Electrolyte for High-Energy Li-Ion Batteries
- Author
-
Lin Ma, Steve Greenbaum, Oleg Borodin, Kang Xu, Mounesha N. Garaga, Jenel Vatamanu, Singyuk Hou, Chunyu Cui, Ji Chen, Qin Li, Xiao Ji, Jiaxun Zhang, Chunsheng Wang, Michael S. Ding, Travis P. Pollard, Chongyin Yang, Hung-Sui Lee, and Long Chen
- Subjects
High energy ,Materials science ,Renewable Energy, Sustainability and the Environment ,Energy Engineering and Power Technology ,02 engineering and technology ,Aqueous electrolyte ,Electrolyte ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Electrochemistry ,01 natural sciences ,0104 chemical sciences ,Anode ,Ion ,Fuel Technology ,Chemical engineering ,Chemistry (miscellaneous) ,Materials Chemistry ,0210 nano-technology - Abstract
A water-in-salt electrolyte (WiSE) offers an electrochemical stability window much wider than typical aqueous electrolytes but still falls short in accommodating high-energy anode materials, mainly...
- Published
- 2020
10. Probing Electric Double-Layer Composition via in Situ Vibrational Spectroscopy and Molecular Simulations
- Author
-
Jenel Vatamanu, Oleg Borodin, Christina H M van Oversteeg, Jonathan H. Raberg, Stephen J. Harris, Tanja Cuk, and Axel Ramos
- Subjects
Materials science ,Passivation ,Solvation ,Infrared spectroscopy ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Electrochemistry ,01 natural sciences ,0104 chemical sciences ,Ion ,Molecular dynamics ,Solvation shell ,Chemical physics ,Electrode ,General Materials Science ,Physical and Theoretical Chemistry ,0210 nano-technology - Abstract
At an electrode, ions and solvent accumulate to screen charge, leading to a nanometer-scale electric double layer (EDL). The EDL guides electrode passivation in batteries, while in (super)capacitors, it determines charge storage capacity. Despite its importance, quantification of the nanometer-scale and potential-dependent EDL remains a challenging problem. Here, we directly probe changes in the EDL composition with potential using in situ vibrational spectroscopy and molecular dynamics simulations for a Li-ion battery electrolyte (LiClO4 in dimethyl carbonate). The accumulation rate of Li+ ions at the negative surface and ClO4- ions at the positive surface from vibrational spectroscopy compares well to that predicted by simulations using a polarizable APPLE&P force field. The ion solvation shell structure and ion-pairing within the EDL differs significantly from the bulk, especially at the negative electrode, suggesting that the common rationalization of interfacial electrochemical processes in terms of bulk ion solvation should be applied with caution.
- Published
- 2019
11. Capacitance with Different Electrode Surface Topology
- Author
-
Dmitry Bedrov and Jenel Vatamanu
- Published
- 2021
12. Fluorinated interphase enables reversible aqueous zinc battery chemistries
- Author
-
Longsheng, Cao, Dan, Li, Travis, Pollard, Tao, Deng, Bao, Zhang, Chongyin, Yang, Long, Chen, Jenel, Vatamanu, Enyuan, Hu, Matt J, Hourwitz, Lin, Ma, Michael, Ding, Qin, Li, Singyuk, Hou, Karen, Gaskell, John T, Fourkas, Xiao-Qing, Yang, Kang, Xu, Oleg, Borodin, and Chunsheng, Wang
- Abstract
Metallic zinc is an ideal anode due to its high theoretical capacity (820 mAh g
- Published
- 2020
13. Hybrid Aqueous/Non-aqueous Electrolyte for Safe and High-Energy Li-Ion Batteries
- Author
-
Wei Sun, Chunsheng Wang, Jenel Vatamanu, Xiulin Fan, Oleg Borodin, Tao Gao, Steve Greenbaum, Yujia Liang, Kang Xu, Nico Eidson, Fei Wang, Michael S. Ding, and Mallory Gobet
- Subjects
Battery (electricity) ,Materials science ,Aqueous solution ,02 engineering and technology ,Electrolyte ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Electrochemistry ,01 natural sciences ,Cathode ,0104 chemical sciences ,law.invention ,Anode ,Ion ,General Energy ,Chemical engineering ,law ,0210 nano-technology ,Electrochemical window - Abstract
Summary Recent breakthroughs in aqueous electrolytes made highly safe 3.0 V class aqueous Li-ion batteries possible. However, the formed solid-electrolyte interphase therein still cannot effectively support the desired energy-dense anode and cathode materials. In this work, we report a new class of electrolytes, by hybridizing aqueous with non-aqueous solvents, that inherits the non-flammability and non-toxicity characteristics from aqueous and better electrochemical stability from non-aqueous systems. The secondary interphasial ingredient (alkylcarbonate) introduced by non-aqueous component helps to expand the electrochemical window of the hybridized electrolyte to 4.1 V, which supports the operation of a 3.2 V aqueous Li-ion battery based on Li 4 Ti 5 O 12 and LiNi 0.5 Mn 1.5 O 4 to deliver a high energy density of 165 Wh/kg for >1,000 cycles. The understanding of how a better interphase could be tailored by regulating the inner-Helmholtz interfacial structures of the hybridized electrolyte provides important guidelines for designing future electrolytes and interphases for new battery chemistries.
- Published
- 2018
14. The nanoscale structure of the electrolyte–metal oxide interface
- Author
-
Christopher J. Takacs, Hans-Georg Steinrück, Oleg Borodin, Chuntian Cao, Oleg Konovalov, Yuchi Tsao, Michael F. Toney, and Jenel Vatamanu
- Subjects
Materials science ,Renewable Energy, Sustainability and the Environment ,Open-circuit voltage ,Oxide ,02 engineering and technology ,Electrolyte ,Lithium hexafluorophosphate ,021001 nanoscience & nanotechnology ,01 natural sciences ,Pollution ,X-ray reflectivity ,chemistry.chemical_compound ,Molecular dynamics ,Adsorption ,Nuclear Energy and Engineering ,chemistry ,Chemical physics ,0103 physical sciences ,Environmental Chemistry ,010306 general physics ,0210 nano-technology ,Ethylene carbonate - Abstract
Electrolyte ordering near solid surfaces is of vital importance in diverse fields, ranging from physical chemistry, to energy storage, and heterogeneous catalysis. However, experimental determination of the structure of the electrode–electrolyte interface and electric double layer is challenging due to limited experimental approaches. In this work we show a detailed picture of the electrode–electrolyte interface relevant to Li-ion batteries. Specifically, we probe the atomic-scale interfacial structure of a non-aqueous liquid electrolyte solution of ethylene carbonate (EC) and dimethyl carbonate (DMC) containing lithium hexafluorophosphate (LiPF6) salt via surface sensitive Angstrom resolution X-ray reflectivity (XRR). We complement our experimental results with molecular dynamics (MD) simulations, and find good agreement between the experiment and simulation derived density profiles. The surface at open circuit voltage (OCV) induces layering of electrolyte molecules near the interface, which decays towards the bulk, and we conclude that both EC and DMC molecules in the first interfacial layer tend to adsorb parallel to the surface. With increasing salt-concentration, the layering periodicity and the degree of order increase. We discuss implications of our results to Li-ion batteries, with focus on the relation between interfacial structure and ion transport in and out of the electrode.
- Published
- 2018
15. (Battery Division Postdoctoral Associate Research Award Address Sponsored by MTI Corporation and the Jiang Family Foundation) Tailoring Bulk and Interfacial Electrolyte Properties to Design Electrochemical Interphases and Enable Highly Reversible Zn Anode
- Author
-
Kang Xu, Marshall A. Schroeder, Jenel Vatamanu, Lin Ma, Travis P. Pollard, Oleg Borodin, Michael Ding, Arthur v. Cresce, Chunsheng Wang, Janet Ho, and Glenn Pastel
- Subjects
Battery (electricity) ,Engineering ,business.industry ,Foundation (engineering) ,Electrolyte ,Division (mathematics) ,business ,Electrochemistry ,Engineering physics ,Anode - Published
- 2021
16. Modeling Insight into Battery Electrolyte Electrochemical Stability and Interfacial Structure
- Author
-
Arthur v. Cresce, Xiaoming Ren, Kang Xu, Oleg Borodin, Jenel Vatamanu, and Jaroslaw Knap
- Subjects
Chemistry ,Inorganic chemistry ,02 engineering and technology ,General Medicine ,General Chemistry ,Electrolyte ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Electrochemistry ,01 natural sciences ,Electrochemical energy conversion ,0104 chemical sciences ,law.invention ,Ion ,Capacitor ,Chemical engineering ,law ,Electrode ,Interphase ,0210 nano-technology ,Voltage - Abstract
Electroactive interfaces distinguish electrochemistry from chemistry and enable electrochemical energy devices like batteries, fuel cells, and electric double layer capacitors. In batteries, electrolytes should be either thermodynamically stable at the electrode interfaces or kinetically stable by forming an electronically insulating but ionically conducting interphase. In addition to a traditional optimization of electrolytes by adding cosolvents and sacrificial additives to preferentially reduce or oxidize at the electrode surfaces, knowledge of the local electrolyte composition and structure within the double layer as a function of voltage constitutes the basis of manipulating an interphase and expanding the operating windows of electrochemical devices. In this work, we focus on how the molecular-scale insight into the solvent and ion partitioning in the electrolyte double layer as a function of applied potential could predict changes in electrolyte stability and its initial oxidation and reduction reactions. In molecular dynamics (MD) simulations, highly concentrated lithium aqueous and nonaqueous electrolytes were found to exclude the solvent molecules from directly interacting with the positive electrode surface, which provides an additional mechanism for extending the electrolyte oxidation stability in addition to the well-established simple elimination of "free" solvent at high salt concentrations. We demonstrate that depending on their chemical structures, the anions could be designed to preferentially adsorb or desorb from the positive electrode with increasing electrode potential. This provides additional leverage to dictate the order of anion oxidation and to effectively select a sacrificial anion for decomposition. The opposite electrosorption behaviors of bis(trifluoromethane)sulfonimide (TFSI) and trifluoromethanesulfonate (OTF) as predicted by MD simulation in highly concentrated aqueous electrolytes were confirmed by surface enhanced infrared spectroscopy. The proton transfer (H-transfer) reactions between solvent molecules on the cathode surface coupled with solvent oxidation were found to be ubiquitous for common Li-ion electrolyte components and dependent on the local molecular environment. Quantum chemistry (QC) calculations on the representative clusters showed that the majority of solvents such as carbonates, phosphates, sulfones, and ethers have significantly lower oxidation potential when oxidation is coupled with H-transfer, while without H-transfer their oxidation potentials reside well beyond battery operating potentials. Thus, screening of the solvent oxidation limits without considering H-transfer reactions is unlikely to be relevant, except for solvents containing unsaturated functionalities (such as C═C) that oxidize without H-transfer. On the anode, the F-transfer reaction and LiF formation during anion and fluorinated solvent reduction could be enhanced or diminished depending on salt and solvent partitioning in the double layer, again giving an additional tool to manipulate the order of reductive decompositions and interphase chemistry. Combined with experimental efforts, modeling results highlight the promise of interphasial compositional control by either bringing the desired components closer to the electrode surface to facilitate redox reaction or expelling them so that they are kinetically shielded from the potential of the electrode.
- Published
- 2017
17. (Invited) Molecular Modeling of Lithium and Zinc Electrolytes
- Author
-
Chunsheng Wang, Lin Ma, Jenel Vatamanu, Oleg Borodin, Kang Xu, Marshall A. Schroeder, and Travis P. Pollard
- Subjects
Aqueous solution ,Materials science ,Born–Oppenheimer approximation ,chemistry.chemical_element ,Electrolyte ,Electrochemistry ,Quantum chemistry ,Ion ,symbols.namesake ,Molecular dynamics ,chemistry ,Chemical physics ,symbols ,Lithium - Abstract
In this presentation I will update on the recent progress towards obtaining fundamental understanding and improving three classes of electrolytes: 1) aqueous and hybrid electrolytes for lithium ion batteries including superconcentrated electrolytes; 2) non-aqueous electrolytes and their interaction with the electrodes for high energy density lithium ion batteries; 3) electrolytes for zinc metal batteries. Accurate molecular dynamics (MD) simulations of these electrolytes using many-body polarizable force field will be used to establish a correlation between the ion transport mechanisms, electrolyte structure and transference number. Reactive modeling will focus on the competitive solvent and salt reduction at the passivated electrochemical interfaces using Born Oppenheimer Molecular Dynamics (BOMD) simulations using DFT functionals. These BOMD simulations included critical factors needed to realistically represent electrolyte reactivity at electrodes such as explicit description of the substrate – electrolyte interactions; accurate representation of electrolyte structure, ion pairing and aggregation near an electrode; and collection of sufficient statistics from multiple unique simulations that were initiated with differing initial configurations. Electrolyte reduction at the passivated interfaces from these simulations will be contrasted with other solvents ranging from ethers with mixed salts or carbonates and results from the representative quantum chemistry (QC) calculations performed on the small model electrolyte clusters to estimate oxidation and reduction.
- Published
- 2021
18. 4.0 V Aqueous Li-Ion Batteries
- Author
-
Wei Sun, Marshall A. Schroeder, Xiulin Fan, Oleg Borodin, Michael S. Ding, Nico Eidson, Tingting Qing, Kang Xu, Chunsheng Wang, Jenel Vatamanu, Chongyin Yang, Arthur v. Cresce, and Ji Chen
- Subjects
Aqueous solution ,Materials science ,Inorganic chemistry ,02 engineering and technology ,engineering.material ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Cathode ,0104 chemical sciences ,Cathodic protection ,law.invention ,Anode ,Metal ,General Energy ,Coating ,law ,visual_art ,engineering ,visual_art.visual_art_medium ,Interphase ,Graphite ,0210 nano-technology - Abstract
Summary Although recent efforts have expanded the stability window of aqueous electrolytes from 1.23 V to >3 V, intrinsically safe aqueous batteries still deliver lower energy densities (200 Wh/kg) compared with state-of-the-art Li-ion batteries (∼400 Wh/kg). The essential origin for this gap comes from their cathodic stability limit, excluding the use of the most ideal anode materials (graphite, Li metal). Here, we resolved this "cathodic challenge" by adopting an "inhomogeneous additive" approach, in which a fluorinated additive immiscible with aqueous electrolyte can be applied on anode surfaces as an interphase precursor coating. The strong hydrophobicity of the precursor minimizes the competitive water reduction during interphase formation, while its own reductive decomposition forms a unique composite interphase consisting of both organic and inorganic fluorides. Such effective protection allows these high-capacity/low-potential anode materials to couple with different cathode materials, leading to 4.0 V aqueous Li-ion batteries with high efficiency and reversibility.
- Published
- 2017
19. On the application of constant electrode potential simulation techniques in atomistic modelling of electric double layers
- Author
-
Dmitry Bedrov, Oleg Borodin, and Jenel Vatamanu
- Subjects
Chemistry ,General Chemical Engineering ,Molecular simulation ,02 engineering and technology ,General Chemistry ,Electrolyte ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,0104 chemical sciences ,Computational physics ,Computational chemistry ,Simple (abstract algebra) ,Modeling and Simulation ,Electrode ,General Materials Science ,0210 nano-technology ,Constant (mathematics) ,Information Systems ,Electrode potential - Abstract
This paper presents a brief overview of molecular simulation techniques utilised to simulate the electrode/electrolyte interfaces. We introduce a simple scheme to perform classical molecular dynami...
- Published
- 2017
20. Charge storage at the nanoscale: understanding the trends from the molecular scale perspective
- Author
-
Dmitry Bedrov, Gleb Yushin, Oleg Borodin, Jenel Vatamanu, and Marco Olguin
- Subjects
Supercapacitor ,Materials science ,Renewable Energy, Sustainability and the Environment ,Nanotechnology ,02 engineering and technology ,General Chemistry ,Surface finish ,Electrolyte ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,law.invention ,Ion ,Capacitor ,Adsorption ,law ,Specific surface area ,Electrode ,General Materials Science ,0210 nano-technology - Abstract
Supercapacitors or electrical double layer (EDL) capacitors store charge via rearrangement of ions in electrolytes and their adsorption on electrode surfaces. They are actively researched for multiple applications requiring longer cycling life, broader operational temperature ranges, and higher power density compared to batteries. Recent developments in nanostructured carbon-based electrodes with a high specific surface area have demonstrated the potential to significantly increase the energy density of supercapacitors. Molecular modeling of electrolytes near charged electrode surfaces has provided key insights into the fundamental aspects of charge storage at the nanoscale, including an understanding of the mechanisms of ion adsorption and dynamics at flat surfaces and inside nanopores, and the influence of curvature, roughness, and electronic structure of electrode surfaces. Here we review these molecular modeling findings for EDL capacitors, dual ion batteries and pseudo-capacitors together with available experimental observations and put this analysis into the perspective of future developments in this field. Current research trends and future directions are discussed.
- Published
- 2017
21. Utilizing Averaged Configuations from Molecular Dynamics Simulation Trajectories.
- Author
-
Peter G. Kusalik, K. Gillis, and Jenel Vatamanu
- Published
- 2007
- Full Text
- View/download PDF
22. Overlooked electrolyte destabilization by manganese (II) in lithium-ion batteries
- Author
-
Weishan Li, Zhi Chen, Lidan Xing, Cun Wang, Jenel Vatamanu, Guangyuan Lan, and Kang Xu
- Subjects
0301 basic medicine ,Science ,Inorganic chemistry ,General Physics and Astronomy ,chemistry.chemical_element ,02 engineering and technology ,Manganese ,Electrolyte ,Article ,General Biochemistry, Genetics and Molecular Biology ,law.invention ,Catalysis ,Batteries ,03 medical and health sciences ,chemistry.chemical_compound ,law ,Hexafluorophosphate ,Electrochemistry ,lcsh:Science ,Dissolution ,Multidisciplinary ,General Chemistry ,021001 nanoscience & nanotechnology ,Cathode ,Anode ,030104 developmental biology ,chemistry ,lcsh:Q ,Lithium ,0210 nano-technology - Abstract
Transition-metal dissolution from cathode materials, manganese in particular, has been held responsible for severe capacity fading in lithium-ion batteries, with the deposition of the transition-metal cations on anode surface, in elemental form or as chelated-complexes, as the main contributor for such degradations. In this work we demonstrate with diverse experiments and calculations that, besides interfacial manganese species on anode, manganese(II) in bulk electrolyte also significantly destabilizes electrolyte components with its unique solvation-sheath structure, where the decompositions of carbonate molecules and hexafluorophosphate anion are catalyzed via their interactions with manganese(II). The manganese(II)-species eventually deposited on anode surface resists reduction to its elemental form because of its lower electrophilicity than carbonate molecule or anion, whose destabilization leads to sustained consumption. The reveal understanding of the once-overlooked role of manganese-dissolution in electrolytes provides fresh insight into the failure mechanism of manganese-based cathode chemistries, which serves as better guideline to electrolyte design for future batteries., Mn dissolution is dominantly responsible for capacity fading of most Mn-rich cathodes. Here the authors reveal that soluble Mn2+ species significantly destabilizes solvent and anion via its unique solvation sheath structure, providing insight into the failure mechanism of related cathode chemistries.
- Published
- 2019
23. (Invited) Insight into Aqueous and Non-Aqueous Electrolyte Structure, Transport and Interfacial Properties from Molecular Modeling
- Author
-
Ji Chen, Marshall A. Schroeder, Jenel Vatamanu, Lin Ma, Oleg Borodin, Chunsheng Wang, Travis P. Pollard, and Kang Xu
- Subjects
Aqueous solution ,Materials science ,Molecular model ,Chemical engineering ,Aqueous electrolyte - Abstract
Insight into Aqueous and Non-Aqueous Electrolyte Structure, Transport and Interfacial Properties from Molecular Modeling A molecular scale insight into ion transport and decomposition is important for understanding deficiencies of the currently used aqueous and non-aqueous electrolytes. In this presentation I will summarize progress made towards improving molecular scale understanding of the structure and electrochemistry for a wide range of aqueous and non-aqueous electrolytes. Modeling of non-aqueous electrolytes will focus on the competitive solvent and salt reduction at the passivated electrochemical interfaces using Born Oppenheimer Molecular Dynamics (BOMD) simulations using DFT functionals. These BOMD simulations included critical factors needed to realistically represent electrolyte reactivity at electrodes such as explicit description of the substrate – electrolyte interactions; accurate representation of electrolyte structure, ion pairing and aggregation near an electrode; and collection of sufficient statistics from multiple unique simulations that were initiated with differing initial configurations. For example, 20 BOMD simulations starting from different initial conditions using 2.0M LiPF6 in THF tetrahydrofuran/2-methyl tetrahydrofuran showed no solvent decomposition nor HF formation while only LiF formation was observed as a result of LiPF6 salt decomposition.1 The most frequently observed reduction events included a PF6 − coordinated to Li+ cations from the electrolyte and LiF surface that lead to anion defluorination and formation of 3LiF and PF3 gas. The solvent separated LiPF6 and did not actively participate in reduction. When surface defects in LiF were present near a high population of PF6 − the anions there was a preference for the LiPF6 reduction and repair the SEI without ether solvent decomposition. Interestingly, a number of fast diffusion events for F- from the electrolyte | LiF interface to the LiF-lithium metal interface was observed that would be expected to occur during Li stripping indicating that F- re-arrangement in the thin LiF passivation films should be also considered. 1 Electrolyte reduction at the passivated interfaces from these simulations will be contrasted with other solvents ranging from ethers with mixed salts or carbonates and results from the representative quantum chemistry (QC) calculations performed on the small model electrolyte clusters to estimate oxidation and reduction. In the second part of the presentation the non-reactive molecular dynamics (MD) using APPLE&P polarizable force field to examine bulk and interfacial properties of the lithium and zinc aqueous electrolytes and electrochemical interfaces with the focus on the transport mechanism and relative contribution to charge flux from the anions and cations.2 Combined together information from these modeling scales suggests numerous strategies for stabilizing the electrolyte – electrode interfaces for numerous aggressive high energy density cathodes combined coupled with graphite and metal anodes. References Chen, J.; Li, Q.; Pollard, T. P.; Fan, X.; Borodin, O.; Wang, C., Electrolyte design for Li metal-free Li batteries. Materials Today 2020. Borodin, O.; Self, J.; Persson, K. A.; Wang, C.; Xu, K., Uncharted Waters: Super-Concentrated Electrolytes. Joule 2020, 4 (1), 69-100.
- Published
- 2020
24. Importance of Ion Packing on the Dynamics of Ionic Liquids during Micropore Charging
- Author
-
Dmitry Bedrov, Oleg Borodin, Yadong He, Rui Qiao, Bobby G. Sumpter, Jingsong Huang, and Jenel Vatamanu
- Subjects
Physics::Biological Physics ,Quantitative Biology::Biomolecules ,Chemistry ,Relaxation (NMR) ,Analytical chemistry ,02 engineering and technology ,Microporous material ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Physics::Geophysics ,0104 chemical sciences ,Ion ,Quantitative Biology::Subcellular Processes ,chemistry.chemical_compound ,Physics::Plasma Physics ,Chemical physics ,Ionic liquid ,General Materials Science ,Physical and Theoretical Chemistry ,Diffusion (business) ,0210 nano-technology ,Layer (electronics) ,Single layer - Abstract
Molecular simulations of the diffusion of EMIM(+) and TFSI(-) ions in slit-shaped micropores under conditions similar to those during charging show that in pores that accommodate only a single layer of ions, ions diffuse increasingly faster as the pore becomes charged (with diffusion coefficients even reaching ∼5 × 10(-9) m(2)/s), unless the pore becomes very highly charged. In pores wide enough to fit more than one layer of ions, ion diffusion is slower than in the bulk and changes modestly as the pore becomes charged. Analysis of these results revealed that the fast (or slow) diffusion of ions inside a micropore during charging is correlated most strongly with the dense (or loose) ion packing inside the pore. The molecular details of the ions and the precise width of the pores modify these trends weakly, except when the pore is so narrow that the ion conformation relaxation is strongly constrained by the pore walls.
- Published
- 2015
25. Improving Electrochemical Stability and Low‐Temperature Performance with Water/Acetonitrile Hybrid Electrolytes
- Author
-
Lidan Xing, Jenel Vatamanu, Weishan Li, Xiongcong Guan, Xiang Liu, Huiyang Chen, Oleg Borodin, Kang Xu, and Jiawei Chen
- Subjects
Imagination ,Thesaurus (information retrieval) ,Chemical substance ,Materials science ,Renewable Energy, Sustainability and the Environment ,media_common.quotation_subject ,Electrolyte ,Electrochemistry ,Search engine ,chemistry.chemical_compound ,Chemical engineering ,chemistry ,General Materials Science ,Acetonitrile ,Science, technology and society ,media_common - Published
- 2019
26. Non-Faradaic Energy Storage by Room Temperature Ionic Liquids in Nanoporous Electrodes
- Author
-
Dmitry Bedrov, Jenel Vatamanu, and Mihaela Vatamanu
- Subjects
Supercapacitor ,Materials science ,Nanostructure ,Nanoporous ,General Engineering ,General Physics and Astronomy ,Ionic bonding ,Nanotechnology ,Electrolyte ,Capacitance ,chemistry.chemical_compound ,chemistry ,Chemical engineering ,Electrode ,Ionic liquid ,General Materials Science - Abstract
The enhancement of non-Faradaic charge and energy density stored by ionic electrolytes in nanostructured electrodes is an intriguing issue of great practical importance for energy storage in electric double layer capacitors. On the basis of extensive molecular dynamics simulations of various carbon-based nanoporous electrodes and room temperature ionic liquid (RTIL) electrolytes, we identify atomistic mechanisms and correlations between electrode/electrolyte structures that lead to capacitance enhancement. In the symmetric electrode setup with nanopores having atomically smooth walls, most RTILs showed up to 50% capacitance increase compared to infinitely wide pore. Extensive simulations using asymmetric electrodes and pores with atomically rough surfaces demonstrated that tuning of electrode nanostructure could lead to further substantial capacitance enhancement. Therefore, the capacitance in nanoporous electrodes can be increased due to a combination of two effects: (i) the screening of ionic interactions by nanopore walls upon electrolyte nanoconfinement, and (ii) the optimization of nanopore structure (volume, surface roughness) to take into account the asymmetry between cation and anion chemical structures.
- Published
- 2015
27. Ionic liquids at charged surfaces: Insight from molecular simulations
- Author
-
Zongzhi Hu, Dmitry Bedrov, and Jenel Vatamanu
- Subjects
Supercapacitor ,Materials science ,Nanotechnology ,Electrolyte ,Condensed Matter Physics ,Energy storage ,Electronic, Optical and Magnetic Materials ,Molecular dynamics ,chemistry.chemical_compound ,Molecular level ,chemistry ,Ionic liquid ,Materials Chemistry ,Ceramics and Composites - Abstract
Understanding of molecular level structure and mechanisms of the formation of electric double layers in realistic ionic liquid-based electrolytes on charged electrode surfaces is one of scientifically and technologically key areas that have attracted a lot of attention over the last decade. Extensive experimental, theoretical, and modeling studies have been dedicated to this challenging topic in order to establish fundamental correlations between the details of molecular structure of electrolyte and the properties of the electric double layers (EDL) forming on various electrodes. While great progress has been made in advancing our understanding of EDL properties and their influence on the performance of supercapacitors, batteries, and other energy storage devices, there are still a number of challenges and controversies that have not been resolved. In this manuscript, we demonstrate how atomistic molecular dynamics simulations provide a powerful tool for dealing with these challenges and can facilitate the design of novel materials for advancing energy storage technologies.
- Published
- 2015
- Full Text
- View/download PDF
28. A comparative study of alkylimidazolium room temperature ionic liquids with FSI and TFSI anions near charged electrodes
- Author
-
Oleg Borodin, Jenel Vatamanu, Dmitry Bedrov, and Zongzhi Hu
- Subjects
chemistry.chemical_classification ,Differential capacitance ,General Chemical Engineering ,Inorganic chemistry ,Analytical chemistry ,Ion ,chemistry.chemical_compound ,Molecular dynamics ,chemistry ,Ionic liquid ,Electrode ,Electrochemistry ,Graphite ,Alkyl ,Electrode potential - Abstract
Electric double layer (EDL) structure and capacitance generated by the two series of room temperature ionic liquids containing alkylimidazolium C n mim (n = 2,4,6,8) cations and bis(fluorosulfonyl) imide (FSO 2 ) 2 N − , (FSI) or bis(trifluoromethylsulfonyl) imide (CF 3 SO 2 ) 2 N − (TFSI) anions were studied on flat (basal plane graphite) and atomically corrugated (prismatic plane graphite) charged electrode surfaces using atomistic molecular dynamics simulations. On atomically flat surface, generated EDLs in all systems produced a weakly changing differential capacitance (DC) as a function of electrode potential. However, on atomically rough surfaces, ionic liquids with FSI and TFSI anions show substantially different EDL structures and DC dependence. Unlike [C n mim][TFSI], which generated a camel-shape DC regardless of the cation alkyl tail length, the [C n mim][FSI] showed a transition from a bell-shape to a camel-shape DC upon increase of the cation alkyl tail length. Analysis of contributions from rearrangement and reorientation of cations and anions indicated that the ability of the FSI anion to respond to changes in electrode potential is the primary driving force for such behavior.
- Published
- 2014
29. Ramifications of Water-in-Salt Interfacial Structure at Charged Electrodes for Electrolyte Electrochemical Stability
- Author
-
Jenel Vatamanu and Oleg Borodin
- Subjects
Supercapacitor ,Aqueous solution ,Passivation ,Chemistry ,Inorganic chemistry ,Oxygen evolution ,02 engineering and technology ,Electrolyte ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Electrochemistry ,01 natural sciences ,0104 chemical sciences ,Molecular dynamics ,Electrode ,General Materials Science ,Physical and Theoretical Chemistry ,0210 nano-technology - Abstract
Development of safe aqueous batteries and supercapacitors critically relies on expanding the electrolyte electrochemical stability window. A novel mechanism responsible for widening the electrochemical stability window of water-in-salt electrolytes (WiSEs) compared to conventional salt-in-water electrolytes is suggested based on molecular dynamics (MD) simulations of the electrolyte–electrode interface. Water exclusion from the interfacial layer at the positive electrode provided additional kinetic protection that delayed the onset of the oxygen evolution reactions. The interfacial structure of a WiSE at negative electrodes near the potential of zero charge clarified why the recently discovered passivation layers formed in WiSEs are robust. The onset of water accumulation at potentials below 1.5 V vs Li/Li+ leads to formation of water-rich nanodomains at the negative electrode, limiting the robustness of the WiSE. Unexpectedly, the bis(trifluoromethanesulfonyl)imide anion adsorbed and trifluoromethanesulf...
- Published
- 2017
30. On anodic stability and decomposition mechanism of sulfolane in high-voltage lithium ion battery
- Author
-
Hebing Zhou, Weishan Li, Wenqiang Tu, Lidan Xing, Yating Wang, Liu Qifeng, Wenna Huang, Jenel Vatamanu, and Rong-Hua Zeng
- Subjects
Reaction mechanism ,General Chemical Engineering ,Inorganic chemistry ,Analytical chemistry ,chemistry.chemical_element ,Electrolyte ,Decomposition ,Lithium-ion battery ,Anode ,chemistry.chemical_compound ,chemistry ,Electrode ,Electrochemistry ,Lithium ,Sulfolane - Abstract
In this work, we investigated the anodic stability and decomposition mechanism of sulfolane (SL). The anodic stability of SL-based electrolyte with different lithium salts on Pt and LiNi0.5Mn1.5O4 electrodes was found to decrease as follows: LiPF6/SL > LiBF4/SL > LiClO4/SL. The oxidation potential of 1M LiPF6/SL electrolyte on both Pt and electrodes is about 5.0V vs Li/Li+. The presence of PF6- and another SL solvent dramatically alters the decomposition mechanism of SL. Oxidation decomposition of SL-SL cluster is the most favorable reaction in LiPF6/SL electrolyte. The dimer products with S-O-R group were detected by IR spectra on the charged LiNi0.5Mn1.5O4 electrode surface and in the electrolyte near the electrode surface, and were found to increase the interfacial reaction resistance of the LiNi0.5Mn1.5O4 electrode.
- Published
- 2014
31. Concentrated electrolytes: decrypting electrolyte properties and reassessing Al corrosion mechanisms
- Author
-
Dennis W. McOwen, Paul D. Boyle, Oleg Borodin, Daniel M. Seo, Wesley A. Henderson, and Jenel Vatamanu
- Subjects
Renewable Energy, Sustainability and the Environment ,Chemistry ,Inorganic chemistry ,chemistry.chemical_element ,Electrolyte ,Conductivity ,Pollution ,Solvent ,Crystallinity ,chemistry.chemical_compound ,Nuclear Energy and Engineering ,Phase (matter) ,Environmental Chemistry ,Ionic conductivity ,Lithium ,Ethylene carbonate - Abstract
Highly concentrated electrolytes containing carbonate solvents with lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) have been investigated to determine the influence of eliminating bulk solvent (i.e., uncoordinated to a Li+ cation) on electrolyte properties. The phase behavior of ethylene carbonate (EC)–LiTFSI mixtures indicates that two crystalline solvates form—(EC)3:LiTFSI and (EC)1:LiTFSI. Crystal structures for these were determined to obtain insight into the ion and solvent coordination. Between these compositions, however, a crystallinity gap exists. A Raman spectroscopic analysis of the EC solvent bands for the 3–1 and 2–1 EC–LiTFSI liquid electrolytes indicates that ∼86 and 95%, respectively, of the solvent is coordinated to the Li+ cations. This extensive coordination results in significantly improved anodic oxidation and thermal stabilities as compared with more dilute (i.e., 1 M) electrolytes. Further, while dilute EC–LiTFSI electrolytes extensively corrode the Al current collector at high potential, the concentrated electrolytes do not. A new mechanism for electrolyte corrosion of Al in Li-ion batteries is proposed to explain this. Although the ionic conductivity of concentrated EC–LiTFSI electrolytes is somewhat low relative to the current state-of-the-art electrolyte formulations used in commercial Li-ion batteries, using an EC–diethyl carbonate (DEC) mixed solvent instead of pure EC markedly improves the conductivity.
- Published
- 2014
32. (Invited) Molecular Scale Modeling of Structure, Transport and Electrochemistry of Aqueous and Non-Aqueous Electrolytes
- Author
-
Jenel Vatamanu, Travis P. Pollard, and Oleg Borodin
- Subjects
Molecular dynamics ,Materials science ,Aqueous solution ,Chemical engineering ,law ,Electrode ,Density functional theory ,Electrolyte ,Electrochemistry ,Quantum chemistry ,Cathode ,law.invention - Abstract
A molecular scale insight into ion transport and decomposition is important for understanding deficiencies of the currently used aqueous and non-aqueous electrolytes. In this presentation I will summarize progress made towards improving molecular scale understanding of the structure and electrochemistry for a wide range of aqueous and non-aqueous electrolytes. Because no one simulation technique is capable of efficiently capturing all transport and electrochemical properties at interfaces, we will utilize a combination of multiple modeling methods: a) density functional theory (DFT) studies of the solvent reactions on cathode surfaces and at the solid electrolyte interphase (SEI) covering lithium metal; b) representative quantum chemistry (QC) calculations performed on the representative small model electrolyte clusters to estimate oxidation and reduction; c) molecular dynamics (MD) using APPLE&P polarizable force field to examine bulk and interfacial properties of electrolytes and electrochemical interfaces; d) new generation of the force fields for accurately capturing electrolyte transport properties and transference number. Combined together information from these modeling scales suggests numerous strategies for stabilizing the electrolyte – electrode interfaces for numerous aggressive high energy density cathodes combined coupled with graphite and metal anodes.
- Published
- 2019
33. Hybrid Aqueous/Non-aqueous Electrolyte for Safe and High-Energy Li-Ion Batteries
- Author
-
Fei Wang, Oleg Borodin, Michael S. Ding, Mallory Gobet, Jenel Vatamanu, Xiulin Fan, Tao Gao, Nico Eidson, Yujia Liang, Wei Sun, Steve Greenbaum, Kang Xu, and Chunsheng Wang
- Subjects
General Energy - Published
- 2018
34. Increasing Energy Storage in Electrochemical Capacitors with Ionic Liquid Electrolytes and Nanostructured Carbon Electrodes
- Author
-
Yury Gogotsi, Dmitry Bedrov, Carlos R. Perez, Jenel Vatamanu, and Zongzhi Hu
- Subjects
Supercapacitor ,Materials science ,Nanoporous ,Nanotechnology ,Electrolyte ,Electrochemistry ,Capacitance ,chemistry.chemical_compound ,Chemical engineering ,chemistry ,Electrode ,Ionic liquid ,Surface roughness ,General Materials Science ,Physical and Theoretical Chemistry - Abstract
The potential pathways to increase the energy storage in electric double-layer (EDL) supercapacitors using room-temperature ionic liquid electrolytes and carbon-based nanostructured electrodes are explored by molecular dynamics simulations. A systematic comparison of capacitances obtained on nanoparticles of various shape and dimensions showed that when the electrode curvature and the length scale of the surface roughness are comparable to ion dimensions, a noticeable improvement in the capacitive storage is observed. The nanoconfinement of the electrolyte in conductive electrode pores further enhances the capacitance due to mismatch in ion–electrode surface interactions and strong electrostatic screening. We show that nanoporous structures made of arrays of conductive carbon chains represent a synergy of all three favorable factors (that is, high curvature, atomic scale roughness, and nanoconfinement) and can generate non-Faradic capacitance ranging from 260 to 350 F/g, which significantly exceeds the pe...
- Published
- 2013
35. Electrode/Electrolyte Interface in Sulfolane-Based Electrolytes for Li Ion Batteries: A Molecular Dynamics Simulation Study
- Author
-
Dmitry Bedrov, Oleg Borodin, Jenel Vatamanu, Lidan Xing, and Grant D. Smith
- Subjects
Double layer (biology) ,Inorganic chemistry ,Electrolyte ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Ion ,Sulfone ,chemistry.chemical_compound ,General Energy ,chemistry ,Electrode ,Graphite ,Sulfolane ,Physical and Theoretical Chemistry ,Dimethyl carbonate - Abstract
The double layer composition and structure of the mixed-solvent electrolyte tetramethylene sulfone/dimethyl carbonate (TMS/DMC) doped with LiPF6 near the graphite surface have been investigated usi...
- Published
- 2012
36. Capacitive Energy Storage: Current and Future Challenges
- Author
-
Jenel Vatamanu and Dmitry Bedrov
- Subjects
Supercapacitor ,Nanostructure ,Materials science ,Field (physics) ,Nanoporous ,Scale (chemistry) ,General Materials Science ,Nanotechnology ,Physical and Theoretical Chemistry ,Current (fluid) ,Energy (signal processing) ,Power density - Abstract
Capacitive energy storage devices are receiving increasing experimental and theoretical attention due to their enormous potential for energy applications. Current research in this field is focused on the improvement of both the energy and the power density of supercapacitors by optimizing the nanostructure of porous electrodes and the chemical structure/composition of the electrolytes. However, the understanding of the underlying correlations and the mechanisms of electric double layer formation near charged surfaces and inside nanoporous electrodes is complicated by the complex interplay of several molecular scale phenomena. This Perspective presents several aspects regarding the experimental and theoretical research in the field, discusses the current atomistic and molecular scale understanding of the mechanisms of energy and charge storage, and provides a brief outlook to the future developments and applications of these devices.
- Published
- 2016
37. Nanopatterning of Electrode Surfaces as a Potential Route to Improve the Energy Density of Electric Double-Layer Capacitors: Insight from Molecular Simulations
- Author
-
Dmitry Bedrov, Lidan Xing, Grant D. Smith, and Jenel Vatamanu
- Subjects
Supercapacitor ,Differential capacitance ,business.industry ,Chemistry ,Nanotechnology ,Electrolyte ,Capacitance ,Energy storage ,law.invention ,Capacitor ,Molecular dynamics ,law ,Electrode ,Optoelectronics ,General Materials Science ,Physical and Theoretical Chemistry ,business - Abstract
Electrostatic double-layer capacitors (EDLCs) with room-temperature ionic liquids (RTILs) as electrolytes are among the most promising energy storage technologies. Utilizing atomistic molecular dynamics simulations, we demonstrate that the capacitance and energy density stored within the electric double layers (EDLs) formed at the electrode-RTIL electrolyte interface can be significantly improved by tuning the nanopatterning of the electrode surface. Significantly increased values and complex dependence of differential capacitance on applied potential were observed for surface patterns having dimensions similar to the ions' dimensions. Electrode surfaces patterned with rough edges promote ion separation in the EDL at lower potentials and therefore result in increased capacitance. The observed trends, which are not accounted for by the current basic EDL theories, provide a potentially new route for optimizing electrode structure for specific electrolytes.
- Published
- 2012
38. Molecular Dynamics Simulation Study of the Interfacial Structure and Differential Capacitance of Alkylimidazolium Bis(trifluoromethanesulfonyl)imide [Cnmim][TFSI] Ionic Liquids at Graphite Electrodes
- Author
-
Grant D. Smith, Dmitry Bedrov, Oleg Borodin, and Jenel Vatamanu
- Subjects
Differential capacitance ,Chemistry ,Inorganic chemistry ,Analytical chemistry ,Electrolyte ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Ion ,chemistry.chemical_compound ,Molecular dynamics ,General Energy ,Electrode ,Ionic liquid ,Graphite ,Physical and Theoretical Chemistry ,Electrode potential - Abstract
The dependence on electrode potential of the interfacial structure and differential capacitance (DC) for 1-alkyl-3-methyimidazolium bis(trifluoromethanesulfonyl)imide ([Cnmim][TFSI], n = 2, 4, 6, and 8) ionic liquids (IL) near basal (flat) and prismatic edge face (rough) graphite electrodes was investigated here with atomistic simulations. Overall camel-shaped DCs were observed for both surfaces. The prismatic graphite generated systematically larger capacitances than the atomically flat basal face. Although on the flat electrodes the DC is almost constant at electrode potential bellow saturation (i.e., roughly within ±2 V), on the prismatic edge face the DC showed large amplitude changes between minima and maxima. This trend in DC was explained from the dependence versus potential of the structure and composition of the interfacial electrolyte layer; specifically, faster counterions accumulation and ion segregation in the interfacial layer are observed for atomically corrugated electrode surfaces as comp...
- Published
- 2012
39. Molecular Dynamics Simulation Studies of the Structure of a Mixed Carbonate/LiPF6 Electrolyte near Graphite Surface as a Function of Electrode Potential
- Author
-
Oleg Borodin, Jenel Vatamanu, and Grant D. Smith
- Subjects
Standard hydrogen electrode ,Inorganic chemistry ,Electrolyte ,Half-cell ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,chemistry.chemical_compound ,General Energy ,chemistry ,Standard electrode potential ,Electrode ,Physical and Theoretical Chemistry ,Dimethyl carbonate ,Ethylene carbonate ,Electrode potential - Abstract
Molecular dynamics (MD) simulations of an electrolyte comprised of ethylene carbonate (EC), dimethyl carbonate (DMC), and LiPF6 salt near the basal face of graphite electrodes have been performed as a function of electrode potential. Upon charging of the electrodes, the less polar DMC molecule is partially replaced in the interfacial electrolyte layer by the more polar EC. At negative potentials, the carbonyl groups from the carbonate molecules are repelled from the surface, while at positive potentials, we find a substantial enrichment of the surface with carbonyl groups. PF6– rapidly accumulates at the positive electrode with increasing potential and vacates the negative electrode with increasing negative potential. In contrast, Li+ concentration in the interfacial layer is found to be only weakly dependent on potential except at very large negative potentials. Hence, both composition of the electrolyte at the electrode surface and solvent environment around Li+ are observed to vary dramatically with th...
- Published
- 2011
40. On the Influence of Surface Topography on the Electric Double Layer Structure and Differential Capacitance of Graphite/Ionic Liquid Interfaces
- Author
-
Liulei Cao, Dmitry Bedrov, Oleg Borodin, Grant D. Smith, and Jenel Vatamanu
- Subjects
Supercapacitor ,Materials science ,Differential capacitance ,Analytical chemistry ,Electrolyte ,Characterization (materials science) ,chemistry.chemical_compound ,chemistry ,Chemical physics ,Electrode ,Ionic liquid ,General Materials Science ,Graphite ,Physical and Theoretical Chemistry ,Electrode potential - Abstract
Molecular simulations reveal that the shape of differential capacitance (DC) versus the electrode potential can change qualitatively with the structure of the electrode surface. Whereas the atomically flat basal plane of graphite in contact with a room-temperature ionic liquid generates camel-shaped DC, the atomically corrugated prismatic face of graphite with the same electrolyte exhibits bell-shaped behavior and much larger DCs at low double-layer potentials. The observed bell-shaped and camel-shaped DC behavior was correlated with the structural changes occurring in the double layer as a function of applied potential. Therefore, the surface topography clearly influences DC behavior, suggesting that attention should be paid to the electrode surface topography characterization in the studies of DC to ensure reproducibility and unambiguous interpretation of experimental results. Furthermore, our results suggest that controlling the electrode roughness/structure could be a route to improving the energy den...
- Published
- 2011
41. Molecular Simulations of the Electric Double Layer Structure, Differential Capacitance, and Charging Kinetics for N-Methyl-N-propylpyrrolidinium Bis(fluorosulfonyl)imide at Graphite Electrodes
- Author
-
Oleg Borodin, Grant D. Smith, and Jenel Vatamanu
- Subjects
Differential capacitance ,Kinetics ,Analytical chemistry ,Surfaces, Coatings and Films ,Ion ,chemistry.chemical_compound ,Molecular dynamics ,chemistry ,Electrode ,Ionic liquid ,Materials Chemistry ,Physical and Theoretical Chemistry ,Imide ,Graphite electrode - Abstract
Molecular dynamics simulations were performed on N-methyl-N-propylpyrrolidinium bis(fluorosulfonyl)imide (pyr(13)FSI) room temperature ionic liquid (RTIL) confined between graphite electrodes as a function of applied potential at 393 and 453 K using an accurate force field developed in this work. The electric double layer (EDL) structure and differential capacitance (DC) of pyr(13)FSI was compared with the results of the previous study of a similar RTIL pyr(13)bis(trifluoromethanesulfonyl)imide (pyr(13)TFSI) with a significantly larger anion [ Vatamanu, J.; Borodin, O.; Smith, G. D. J. Am. Chem. Soc. 2010, 132, 14825]. Intriguingly, the smaller size of the FSI anion compared to TFSI did not result in a significant increase of the DC on the positive electrode. Instead, a 30% higher DC was observed on the negative electrode for pyr(13)FSI compared to pyr(13)TFSI. The larger DC observed on the negative electrode for pyr(13)FSI compared to pyr(13)TFSI was associated with two structural features of the EDL: (a) a closer approach of FSI compared to TFSI to the electrode surface and (b) a faster rate (vs potential decrease) of anion desorption from the electrode surface for FSI compared to TFSI. Additionally, the limiting behavior of DC at large applied potentials was investigated. Finally, we show that constant potential simulations indicate time scales of hundreds of picoseconds required for electrode charge/discharge and EDL formation.
- Published
- 2011
42. (Invited) Bulk and Interfacial Behavior of Ionic Liquids from Molecular Dynamics Simulations
- Author
-
Jenel Vatamanu, Grant D. Smith, and Oleg Borodin
- Subjects
Supercapacitor ,Molecular dynamics ,chemistry.chemical_compound ,Materials science ,chemistry ,Chemical engineering ,Vapor pressure ,Ionic liquid ,chemistry.chemical_element ,Lithium ,Electrochemistry ,Dissolution ,Flammability - Abstract
Results of molecular dynamics simulations using many-body polarizable APPLE&P force field are presented for 34 ionic liquids covering a broad range of cations and anions. A relation between ionic liquid transport properties (ion self-diffusion coefficient and conductivity), thermodynamic properties (molar volume and heat of vaporization) and cation-anion binding energies are presented. Development of the nonpolarizable united atom force field for alkylpyrrolidinium and tetraalkyl ammonium-based ionic liquids is reported. The nonpolarizable force field yielded higher activation energy for ion transport as a function of temperature and slightly lower heat of vaporization. Interfacial properties of N-methyl-N-propylpyrrolidinium bis(trifluoromethane)sulfonyl imide near a graphite electrode and in nanopores have been studied as a function temperature and electrode potential.
- Published
- 2010
43. The 1-ethyl-3-methylimidazolium bis(trifluoro-methylsulfonyl)-imide ionic liquid nanodroplets on solid surfaces and in electric field: A molecular dynamics simulation study
- Author
-
Dengpan Dong, Dmitry Bedrov, Jenel Vatamanu, and Xiaoyu Wei
- Subjects
Materials science ,Field (physics) ,General Physics and Astronomy ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Electrostatics ,01 natural sciences ,0104 chemical sciences ,Contact angle ,chemistry.chemical_compound ,symbols.namesake ,Molecular dynamics ,chemistry ,Chemical physics ,Electric field ,Ionic liquid ,symbols ,Wetting ,Physical and Theoretical Chemistry ,van der Waals force ,0210 nano-technology - Abstract
Atomistic molecular dynamics simulations were conducted to study the wetting states of 1-ethyl-3-methylimidazolium bis(trifluoro-methylsulfonyl)-imide ionic liquid (IL) nanodroplets on surfaces with different strengths of van der Waals (VDW) interactions and in the presence of an electric field. By adjusting the depth of Lennard-Jones potential, the van der Waals interaction between the solid surface and ionic liquid was systematically varied. The shape of the droplets was analyzed to extract the corresponding contact angle utilized to characterize wetting states of the nanodroplets. The explored range of surface-IL interactions allowed contact angles ranging from complete IL spreading on the surface to poor wettability. The effect of the external electrical field was explored by adding point charges to the surface atoms. Systems with two charge densities (±0.002 e/atom and ±0.004 e/atom) that correspond to 1.36 V/nm and 2.72 V/nm electric fields were investigated. Asymmetrical wetting states were observed for both cases. At 1.36 V/nm electric field, contributions of IL-surface VDW interactions and Coulombic interactions to the wetting state were competitive. At 2.72 V/nm field, electrostatic interactions dominate the interaction between the nanodroplet and surface, leading to enhanced wettability on all surfaces.
- Published
- 2018
44. (Invited) Recent Progress in Understanding Battery Electrolyte Electrochemical Stability and Its Relationship with Electrolyte Structural Properties
- Author
-
Oleg Borodin, Jenel Vatamanu, Marco Olguin, Travis Pollard, Claire Eisner, Kenneth Leiter, and Jaroslaw Knap
- Abstract
Designing compatible electrochemical interfaces is paramount for enabling energy storage devices from batteries to electric double layer capacitors as electrolytes should be either electrochemically stable at the electrode and current collectors surfaces or form a stable electronically insulating but ionically conducting solid electrolyte interphase (SEI). Electrical double layer capacitors with narrow pores cannot rely on the SEI to extend their operating window placing more stringent requirements on electrolyte intrinsic electrochemical stability compared to batteries. In this presentation I will discuss a molecular scale insight into the initial mechanisms of battery electrolyte electrochemical degradation on the active and non-active electrodes obtained from a coordinated density functional theory (DFT) study and non-reactive molecular dynamics (MD) simulations of bulk and interfacial properties of electrolytes and the relationship between them. In the first part of the presentation, I will focus on understanding of electrolyte oxidation reactions on active and non-active electrodes. While HOMO screening for redox shuttle molecules was previously successful for quantitatively predicting trends, such screening is often not sufficient for traditional battery electrolyte solvents including cycling and linear carbonates, phosphates and sulfones.(1) Instead, quantum chemistry calculations have shown that the majority of battery solvents with the exception of the solvents with unsaturated functionalities such C=C double bonds do not undergo direct oxidation within typical operating range, instead their oxidation is coupled with the H-transfer to another solvent or oxygen of the electrode surface. Analogously, on the anode the F-transfer and LiF formation during anion and semi-fluorinated solvent reduction occurs at higher potentials compared to direct reduction of isolated anions and solvents.(2) Local ion and solvent environment influences both oxidation and reduction stability and initial decomposition reactions of electrolytes making electrolyte electrochemical stability dependent on the salt concentration and ion and solvent partitioning with the double layer that is in turn is dependent on the applied potential. Highly concentrated aqueous and non-aqueous electrolytes were found in MD simulations to exclude the solvent molecules from directly interacting with the positive electrode surface providing an additional mechanism for extending the electrolyte oxidation stability in addition to the widely discussed elimination of the “free” solvent from the electrolytes by increasing salt concentration.(3) In this presentation, I will give multiple examples on how changes in the double layer partitioning could be beneficial or detrimental to improving the electrode – electrolyte compatibility with aqueous and non-aqueous electrolytes. (4) References Borodin, O.; Olguin, M.; Spear, C. E.; Leiter, K.; Knap, J., Towards High Throughput Screening of Electrochemical Stability of Battery Electrolytes. Nanotechnology 2015, 26, 354003. Borodin, O.; Olguin, M.; Spear, C.; Leiter, K.; Knap, J.; Yushin, G.; Childs, A.; Xu, K., Challenges with Quantum Chemistry-Based Screening of Electrochemical Stability of Lithium Battery Electrolytes. ECS Transactions 2015, 69, 113-123. Vatamanu, J.; Borodin, O., Ramifications of Water-in-Salt Interfacial Structure at Charged Electrodes for Electrolyte Electrochemical Stability. J. Phys. Chem. Lett. 2017, 8, 4362-4367. Borodin, O. ; Ren, X.; Vatamanu, J.; Cresce, A. von Wald; Knap, J.; Xu, K. "A Modeling Insight into Battery Electrolyte Electrochemical Stability and Interfacial Structure" Acc. Chem. Res. 2017 (ASAP)
- Published
- 2018
45. Correction: The nanoscale structure of the electrolyte–metal oxide interface
- Author
-
Hans-Georg Steinrück, Jenel Vatamanu, Oleg Konovalov, Michael F. Toney, Chuntian Cao, Christopher J. Takacs, Oleg Borodin, and Yuchi Tsao
- Subjects
Materials science ,Renewable Energy, Sustainability and the Environment ,Interface (Java) ,Oxide ,Hardware_PERFORMANCEANDRELIABILITY ,Electrolyte ,Pollution ,Metal ,chemistry.chemical_compound ,Nuclear Energy and Engineering ,chemistry ,Chemical engineering ,visual_art ,Hardware_INTEGRATEDCIRCUITS ,visual_art.visual_art_medium ,Environmental Chemistry ,Nanoscopic scale ,Hardware_LOGICDESIGN - Abstract
Correction for ‘The nanoscale structure of the electrolyte–metal oxide interface’ by Hans-Georg Steinrück et al., Energy Environ. Sci., 2018, DOI: 10.1039/c7ee02724a.
- Published
- 2018
46. On the Atomistic Nature of Capacitance Enhancement Generated by Ionic Liquid Electrolyte Confined in Subnanometer Pores
- Author
-
Lidan Xing, Dmitry Bedrov, Oleg Borodin, and Jenel Vatamanu
- Subjects
chemistry.chemical_classification ,Differential capacitance ,Analytical chemistry ,Electrolyte ,Capacitance ,Nanopore ,Molecular dynamics ,chemistry.chemical_compound ,chemistry ,Chemical physics ,Electrode ,Ionic liquid ,General Materials Science ,Physical and Theoretical Chemistry ,Counterion - Abstract
The capacitance enhancement experimentally observed in electrodes with complex morphology of random subnanometer wide pores is an intriguing phenomena, yet the mechanisms for such enhancement are not completely understood. Our atomistic molecular dynamics simulations demonstrate that in subnanometer slit-geometry nanopores, a factor of 2 capacitance enhancement (compared to a flat electrode) is possible for the 1-ethyl-3-methylimidazolium (EMIM)-bis(trifluoro-methylsulfonyl)imide (TFSI) ionic liquid electrolyte. This capacitance enhancement is a result of a fast charge separation inside the nanopore due to abrupt expulsion of co-ions from the pore while maintaining an elevated counterion density due to strong screening of electrostatic repulsive interactions by the conductive pore. Importantly, we find that the capacitance enhancement can be very asymmetric. For the negatively charged 7.5 Å wide pore, the integral capacitance is 100% larger than on a flat surface; however, on the positive electrode, almost no enhancement is observed. Detailed analysis of structure and composition of electrolyte inside nanopores shows that the capacitance enhancement and the shape of differential capacitance strongly depend on the details of the ion chemical structure and a delicate balance of ion-surface and ion-ion interactions.
- Published
- 2015
47. Discrimination in racemates of small chiral molecules
- Author
-
N. M. Cann, Jenel Vatamanu, and E. Cressman
- Subjects
Quantitative Biology::Biomolecules ,Chemistry ,media_common.quotation_subject ,Monte Carlo method ,Intermolecular force ,Biophysics ,Radial distribution ,Condensed Matter Physics ,Integral equation ,Asymmetry ,Computational chemistry ,Molecule ,Physics::Chemical Physics ,Physical and Theoretical Chemistry ,Enantiomer ,Selectivity ,Molecular Biology ,media_common - Abstract
A comparison of similar chiral molecules provides information about the impact of molecular characteristics on selectivity. In this article, the intermolecular structure in racemic fluids is the basis for comparing the molecules: the radial distribution between atoms on identical molecules is compared with the corresponding distribution for atoms from a mirror-image pair. A difference in these distributions signals an enantiomeric imbalance in the local distribution of molecules. The structure in the racemic fluids is explored using Monte Carlo (MC) simulations and the integral equation theory of Chandler, Silbey and Ladanyi (CSL) [1982, Molec. Phys., 46, 1335]. Racemic fluids are examined for several categories of chiral molecules. First, symmetrically shaped molecules have been considered in order to isolate local excesses attributable to energetic contributions. Second, racemates of hard chiral molecules have been examined. Here, enantiomeric imbalances can only originate from asymmetry in the molecula...
- Published
- 2003
48. Structure and Transport of 'Water-in-Salt' Electrolytes from Molecular Dynamics Simulations
- Author
-
Oleg Borodin, Liumin Suo, Marco Olguin, Arthur v. Cresce, Jenel Vatamanu, Fei Wang, Xiaoming Ren, Joseph A. Dura, Antonio Faraone, Mallory Gobet, Stephen Munoz, Steven Greenbaum, Chunsheng Wang, and Kang Xu
- Abstract
Currently used lithium ion batteries for portable electronics utilize flammable and often toxic non-aqueous electrolytes in order to achieve high energy densities. They also require a low humidity manufacturing environment resulting in an increased cost. Aqueous electrolytes have recently emerged as potential intrinsically nonflammable alternatives after their electrochemical stability window was expanded beyond 3.0 V by employing a new class of “Water-in-Salt” electrolytes. In such super-concentrated electrolyte, the decomposition of salt anion occurs preferentially on the anode before hydrogen evolution takes place, creating a kinetic protection against electrochemical decomposition via a dense solid electrolyte interphase (SEI). In this presentation, results from classical molecular dynamics (MD) simulations using a polarizable APPLE&P force field are analyzed in order to examine in detail the ion transport mechanism in bis(trifluoromethane sulfonyl)imide (LiTFSI-water) “Water-in-Salt” electrolytes (WiSE) for safe, green and low cost aqueous lithium ion batteries. They are complemented by Born Oppenheimer MD simulations of smaller systems that yield similar structural features. Simulations revealed an unusually low activation energy and fast ion transport for highly concentrated solutions even at low temperatures that is quite different from the dramatic increase of the activation energy for conductivity found in traditional battery electrolytes. A high conductivity and lithium transference number in WiSE is attributed to the formation of fast ion transporting pathways that are connected to the unexpected structure of WiSE electrolytes, which was confirmed by small angle neutron scattering experiments (SANS). The ability of MD simulations to describe dynamics of ion and solvent in WiSE electrolytes was further validated via pfg-NMR and conductivity measurements, while IR spectroscopy measurements provide a comprehensive picture of the salt electrolyte aggregation that is coupled with ion transport. The connection between the double layer structure of WiSE electrolytes and its electrochemical stability will be briefly discussed.
- Published
- 2017
49. A Molecular Dynamics Study of Concentrated Aqueous Solutions of Lithium Salts at Charged Electrodes
- Author
-
Jenel Vatamanu and Oleg Borodin
- Abstract
Li-ion batteries (LiBs) are widely used in very diverse set of applications from portable electronics, to electric vehicle transportation. Hence, improving LiBs’ power and energy while not compromising safety, remains a hot research topic. Organic solvents permit higher operating voltages; however, they have the disadvantage of being volatile and flammable. Aqueous solvents, on the other hand, are inexpensive and non-flammable but they are typically stable only at low voltages ( In this presentation we explore an intriguing supposition that the electrochemical stability of these systems can be correlated with the electrolyte structure near surface. Using classical molecular dynamics simulations we investigate the electrolyte partition near the electrode, as a function of the applied potential. The studied system consisted of a highly concentrated solution of two salts LiTFSI and LiCF3SO3in water that was recently shown to have one wide electrochemical stability.(2) The electrolyte structuring near the electrode was found to be strongly dependent on the applied potential. Specifically, at the positively charged electrode water is displaced from the surface by the voluminous anions, while at the negatively charged electrode a large accumulation of water is observed in the interfacial layer. Interestingly, the water is displaced rapidly from the negative surface as the potential increases from -2V to 0V, and surprisingly elevated densities of F groups were found next to surface at -1V. In such concentrated electrolytes, the Li ions are only partly coordinated with water (2-2.6 water molecules per Li). The partly desolvated Li+ can drag the TFSI anion near the negative electrode. In agreement with this observation, our simulations confirmed the presence of F groups in the proximity of the interfacial Li+ at the negative electrode. The presence of Li+and F next to the negative charged surface can trigger electrochemical reactions that kinetically passivate the negative electrode surface. References 1. L. Suo, O. Borodin, T. Gao, M. Olguin, J. Ho, X. Fan, C. Luo, C. Wang and K. Xu, Science, 350, 938 (2015). 2. L. Suo, O. Borodin, W. Sun, X. Fan, C. Yang, F. Wang, T. Gao, Z. Ma, M. Schroeder, A. von Cresce, S. M. Russell, M. Armand, A. Angell, K. Xu and C. Wang, Angew. Chem. Int. Ed, 55, 7136 (2016). 3. F. Wang, Y. Lin, L. Suo, X. Fan, T. Gao, C. Yang, F. Han, Y. Qi, K. Xu and C. Wang, Energy Environ. Sci.,, 9, 3666 (2016). 4. Y. Yamada, K. Usui, K. Sodeyama, S. Ko, Y. Tateyama and A. Yamada, Nature Energy, 1, 16129 (2016). Figure 1
- Published
- 2017
50. Racemic fluids of hard molecules
- Author
-
Jenel Vatamanu and N. M. Cann
- Subjects
Bond length ,Correlation function ,Chemistry ,Quantum mechanics ,General Physics and Astronomy ,Interaction site ,Molecule ,Thermodynamics ,Statistical mechanics ,Physical and Theoretical Chemistry ,Integral equation ,Liquid theory - Abstract
The structure in four racemic fluids is explored using two integral equation theories: the reference interaction site method (RISM) [D. Chandler and H. C. Andersen, J. Chem. Phys. 57, 1930 (1972)] and the diagrammatically correct theory of Chandler, Silbey, and Ladanyi (CSL) [D. Chandler, R. Silbey, and B. M. Ladanyi, Mol. Phys. 46, 1335 (1982)]. Discrimination is measured by comparison of site pair distributions for sites on identical molecules with the corresponding distributions for sites on mirror-image molecules. We find that discrimination is largest for distributions between the smallest sites in the molecules. Between racemates, those consisting of more asymmetrical chiral molecules (i.e., with a bigger range of site sizes and bond lengths) show the largest discrimination. The indirect correlation function is shown to be nondiscriminating in racemates. Further, exact relationships between like–like and like–unlike differences in the other pair functions have been obtained. From these, the importan...
- Published
- 2001
Catalog
Discovery Service for Jio Institute Digital Library
For full access to our library's resources, please sign in.