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High-energy lithium-sulfur (Li-S) batteries still suffer from poor rate capability and short cycle life caused by the polysulfides shuttle and insulating nature of S (and the discharge product, Li2S). Selenium disulfide (SeS2), with a theoretical specific capacity of 1342 mAh g-1, is a promising cathode material as it has better conductivity compared to sulfur. The electrochemical reaction kinetics of CNFs-S/SeS2 composites (denoted as CNFs/S1-xSex, where x ≤ 0.1) are expected to be remarkably improved because of the better conductivity of SeS2 compared to sulfur. Here, a high-performance composite cathode material of CNFs/S1-xSex for novel Li-S batteries is reported. The CNFs/S1-xSex composites combine the higher conductivity and higher density of SeS2 with high specific capacity of sulfur. The CNFs/S1-xSex electrode shows good initial discharge capacity of ~1050 mAh g-1 at 0.05 C rate with high mass loading of materials (~6-7 mg cm-2 of composites) and > 97% initial coulombic efficiency. The CNFs/S1-xSex electrode shows more than 600 mAh g-1 specific capacity after 50 charge-discharge cycles at 0.5C rate, much higher compared to the CNFs/S cathodes.

This study reports a high-performance tin (Sn)-coated vertically aligned carbon nanofiber array anode for lithium-ion batteries. The array electrodes have been prepared by coaxial sputter-coating of tin (Sn) shells on vertically aligned carbon nanofiber (VACNF) cores. The robust brush-like highly conductive VACNFs effectively connect high-capacity Sn shells for lithium-ion storage. A high specific capacity of 815 mAh g-1 of Sn was obtained at C/20 rate, reaching toward the maximum value of Sn. However, the electrode shows poor cycling performance with conventional LiPF6 based organic electrolyte. The addition of fluoroethylene carbonate (FEC) improve the performance significantly and the Sn-coated VACNFs anode shows stable cycling performance. The Sn-coated VACNF array anodes exhibit outstanding capacity retention in the half-cell tests with electrolyte containing 10 wt.% FEC and could deliver a reversible capacity of 480 mAh g-1 after 50 cycles at C/3 rate.

Lithium-ion conducting solid polymer electrolytes (SPEs) are promising materials to replace flammable liquid electrolytes to solve the safety and performance issues in conventional rechargeable lithium batteries [1]. Poly(ethylene oxide) (PEO) has been studied extensively as baseline materials for SPEs. It is well known that pure PEO crystallizes at room temperature, hampering lithium ion migration and resulting in low ionic conductivity. This drawback hinders PEO based SPEs applied in real battery configuration that usually requires ionic conductivity greater than 10-4 S cm-1 at 25 ℃. In general, suppression of polymer crystallinity is favorable for SPEs to enhance the ionic conductivity [2]. Here, we synthesized a semi-interpenetrating polymer network (s-IPN) from the mixture of poly(propylene carbonate) (PPC), poly(ethylene glycol) methylether acrylate (PEGMEA), poly(ethylene glycol) diacrylate (PEGDA), and lithium bis(trifluoromethane) sulfonimidate (LiTFSI) salt using one-pot thermal curing method. The amorphous PPC performs as film forming agent, whereas the crosslinked network with PEG pendants provides lithium conducting channel. The s-IPN architecture inhibits the phase segregation of two different polymers. Curing temperature, crosslinker PEGDA content and salt concentration were optimized carefully to attain a flexible film with ionic conductivity reaching 5×10-6 S cm-1 at ambient temperature. The ionic conductivity and working potential window were correlated with the thermal and physical properties of the s-IPN electrolytes. Differential scanning calorimetry measurements have shown a decrease in the crystallinity of the s-IPN electrolytes. The electrolyte with higher salt concentration has lower ionic conductivity, consistent with higher glass transition temperature of PEG chain. The ionic conductivity was further enhanced by incorporating lithium ion conductive ceramic powder, lithium lanthanum zirconate (LLZO) as a filler into the s-IPN matrix, even though LLZO aggregation occurred during film forming. The optimized s-IPN has potential as a baseline material for future solid-state electrolyte designs. Acknowledgements We gratefully acknowledge the financial support from the NASA MIRO Program #NNX15AP44A and the National Science Foundation under Award #162-6449. References [1] Kang Xu. Electrolytes and Interphases in Li-Ion Batteries and Beyond. Chem. Rev. 2014, 114, 11503–11618 [2] Yu Wang, Wei-Hong Zhong. Development of Electrolytes towards Achieving Safe and High-Performance Energy-Storage Devices: A Review. CHEMELECTROCHEM 2015, 2, 22–36

Lithium sulfide (Li2S) is one of the most attractive cathode materials for high energy density lithium batteries as it has a high theoretical capacity of 1166 mA h g-1. However, Li2S suffers from poor rate performance and short cycle life due to its insulating nature and polysulfide shuttle during cycling. In this work, we report a facile and viable approach to address these issues. We propose a method to synthesize a Li2S based nanocomposite cathode material by dissolving Li2S as the active material, polyvinylpyrrolidone (PVP) as the carbon precursor, and graphene oxide (GO) as a matrix to enhance the conductivity, followed by a co-precipitation and high-temperature carbonization process. The Li2S/rGO cathode yields an exceptionally high initial capacity of 817 mAh g-1 based on Li2S mass at C/20 rate and also shows a good cycling performance. The carbon-coated Li2S/rGO cathode demonstrates the capability of robust core-shell nanostructures for different rates and improved capacity retention, revealing carbon coated Li2S/rGO composites as an outstanding system for high-performance lithium-sulfur batteries.

Vanadium Pentoxide (V2O5) has been identified as a potential cathode material owning to its high specific capacity, theoretically, 441 mAh g-1 for 3Li+ ions insertion/extraction. However, the intrinsic drawbacks of V2O5, i.e. structural instability and poor electronic and ionic conductivity, greatly inhibit its application as a cathode. Here, we report a cetyltrimethylammonium bromide (CTAB)-assisted hydrothermal reaction to synthesize V2O5 nanoclusters. Unique aggregated fiber structure was obtained after annealing. To achieve a porous structure and increase the conductivity, nitrogen-doped Graphene (NG) suspended in ethylene glycol was added to the reaction mixture. The obtained spherical V2O5 nanoparticles and NG sheets were randomly dispersed in the matrix of the V2O5 spheres. As a cathode material for lithium-ion batteries, the V2O5/NG hybrids demonstrate better rate performance compared to the bundle-like V2O5 fibers, delivering higher specific capacity of ~ 300 and 150 mAh g-1 at a rate of C/10 and 5C, respectively. The enhanced performance in lithium storage are attributed to the synergistic effect of the nanostructured V2O5/NG composites.

Replacing liquid electrolytes with solid-state Li-ion conductors is one way to achieve safe rechargeable batteries with high energy density. Semi-interpenetrating polymer network (s-IPN) was synthesized from the mixture of poly(propylene carbonate), poly(ethylene glycol) methyl ether acrylate, poly(ethylene glycol) diacrylate (PEGDA), and lithium bis(trifluoromethane)sulfonamide salt via one-pot thermal curing method. The crosslinker PEGDA content and salt concentration were optimized and the best result was abtained at a molar ratio of EO:Li ∼ 14:1. The electrolyte with higher salt concentration had lower ionic conductivity, consistent with higher glass transition temperature of poly(ethylene glycol) chain. Differential scanning calorimetry has shown a low degree of crystallinity when lithium lanthanum zirconate doped tantalum (LLZTO) was added to the s- IPN electrolyte which corresponds to an increase in ionic conductivity, 4.5 x 10-4 S/cm at 40°C. The resulting composite polymer electrolyte (CPE) showed high electrochemical stability up to 5.5 V. Lithium plating and stripping at 0.1 mA/cm2 at room temperature revealed a stable Li/electrolyte interface and no dendrite formation. Cycling performance of a full solid-state cell made with the CPE using LiFePO4 as the cathode will be discussed. Figure 1

First-principles computational studies were used to calculate discharge curves for lithium in RuO2 and to understand the molecular mechanism of lithium sorption into crystalline bulk RuO2. These studies were complemented by experiments to provide new insights into the molecular mechanisms for the first and subsequent discharges of RuO2 anodes in lithium ion batteries. RuO2 nanoplates show slow fading of capacity over multiple cycles, retaining 76% of their original capacity after 20 cycles. The calculated discharge curves for lithium in RuO2 lattice show qualitative agreement with experimental discharge curves for RuO2 nanoplates. The molecular level analysis shows that an intercalation mechanism is operational until a 1:1 Li:Ru ratio is reached, which is followed by a conversion mechanism into Ru metal and Li2O. Furthermore, in agreement with experiment, the computations predict superstoichiometric capacity of RuO2, i.e., accommodation of lithium well beyond the stoichiometric limit of 4:1 Li:Ru ratio, a...

Synthesis and understanding of metal oxide nanomaterials with improved electrochemical properties can play a big role in the development of high capacity electrochemical cells for application in lithium-ion batteries (LIBs). Metal oxide nanostructured materials have shown exceptional storage capabilities through conversion reaction. But, excess reversible capacity is usually observed in these systems. To understand the origin of the excess capacity, we have prepared nanostructured ruthenium oxide (RuO2) directly on stainless steel current collectors using low pressure chemical vapor deposition. The crystal structure of the as-prepared materials were examined by powder X-ray diffraction and indexed to the rutile structure. Field emission scanning electron microscopy revealed 3D pyramidal shape architectures that self-assembled into columns creating high surface area. Galvanostatic charge-discharge measurements were performed versus Li/Li+ in the range of 4.0 to 0.1 V. We have observed a reversible capacity of 1150 mAh/g which is equivalent to 5.70 Li per mol of RuO2. The expected capacity of RuO2 is 806 mAh/g which is approximately 4 Li per mol of RuO2 based on this equation: RuO2 + Li + 4e- ↔ Ru0 + 2Li2O. The excess capacity is approximately 435 mAh/g. The origin of the excess capacity was investigated using cyclic voltammetry, which was performed at two different range of voltage.

RuO2 has been studied for a long time as a model electrode for lithium ion battery, however, little is known about their cycle life at high capacity. Using a simple low-pressure chemical vapor deposition process, hierarchical columnar RuO2 nanoplates were directly deposited on stainless steel current collectors. Powder X-ray diffraction revealed the existence of the rutile form of RuO2 (P42/mnm, a = 4.499 A, c = 3.111 A), with a (110) preferred orientation for the as-deposited materials. The electrodes showed significant cycle life improvement versus Li/Li+ at high capacity (932 mAh g–1). This capacity is higher than expected for the conversion reaction (806 mAh g–1) of RuO2. Galvanostatic discharge–charge experiments were performed in the range of 4.0 to 0.1 V versus Li/Li+ at a constant current density of ∼806 mA g–1. These self-supported electrodes have shown 94% reversibility for the first 30 cycles and 81% after 60 cycles, which indicate good kinetics and excellent capacity retention. This significan...

The present rechargeable lithium-ion battery systems commonly use small amount of electrolytes based on suitable lithium salts (generally LiPF6) and organic solvents (generally alkylcarbonates, such as EC, DMC), which represent a major concern for device safety due to the flammable and volatile nature of these organic liquids. The use of these organic carbonates electrolytes allows the realization of high-performance batteries, but due to its flammability, their use also poses serious safety risks and strongly reduces the battery operative temperature range. Therefore, alternative electrolytes have been proposed and tested in the last decade [1]. Ionic liquids doped with a lithium salt are alternative electrolytes for lithium-ion batteries that offer some advantages compared to organic carbonates based liquid electrolytes. Ionic liquids display a low vapor pressure which leads to nonflammability. The main drawback of ionic liquid-based electrolytes is the low lithium-ion conductivity due to relatively high viscosity of ionic liquids. A lot of research has been devoted to developing ionic liquids with low viscosity. However, so far, these ionic liquids could be obtained only at the expense of lower thermal and/or electrochemical stability. In recent years, mixtures of organic carbonates-based electrolytes and ionic liquids have been proposed as a solution to overcome the lithium-ion transport limitations of ionic liquid-based electrolytes while improving safety due to a lower flammability than that of organic carbonates electrolytes [1, 2]. Herein, we report the results of physical-chemical and electrochemical investigations performed on mixed electrolytes based on an ionic liquid, 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide (BMP-TFSI), and organic electrolytes (LiTFSI in EC/DMC) with nanostructured silicon-anode for lithium-ion batteries. The ionic conductivity, lithium-ion transference number, viscosity and electrochemical stability windows of all different ionic liquid content mixtures were investigated and compared with carbonates-based electrolyte. The specific capacity and cycling stability of the nanostructured silicon-anode were investigated at different C-rates at room temperature. A reversible capacity of 3480 mAh g-1 (of Si) at C/10 and 1600 mAh g-1 at 5C is obtained with cells having electrolyte mixture with a composition of 1:1. This study indicates that safety and electrochemical performance of the Si-anode for Li-ion battery can be improved by using mixed ionic liquid and carbonates-based electrolytes. [1] A. Guerfi, M. Dontigny, P. Charest, M. Petitclerc, M. Lagacé, A. Vijh, K. Zaghib, J. Power Sources 195 (2010) 845-852. [2] R.-S. Kühnel and A. Balducci, J. Phys. Chem. C 118 (2014) 5742-5748.

Lithium-sulfur (Li-S) batteries have attracted considerable attention as one of the most promising next-generation energy storage system owing to the high theoretical specific capacity (1675 mAh g-1), low cost, natural abundance and environmentally benign nature of sulfur. However, the poor electrical conductivity of elemental S results in low utilization of S specific capacity, and hence, insufficient specific energy of Li-S batteries. Development of Li-S batteries is hindered by sluggish kinetics resulting from the intrinsic poor conductivity of sulfur and capacity degradation due to solubility of polysulfides intermediate. One strategy to overcome with these issues is to use of titanium disulfide (TiS2) as an additive to sulfur electrodes as it is a good electrical conductor and electrochemically active and also has the ability to adsorb polysulfide. Herein, we investigated TiS2 as additive with sulfur using hierarchical architectures of carbon as effective hosts for S/TiS2. By a facile one-step melting diffusion method, we synthesized S/TiS2@carbon nanofibers (CNFs) composites in which TiS2 was uniformly distributed over the S-CNFs. The hierarchical S/TiS2@CNFs (TiS2, 20 wt%) electrodes shows good initial discharge capacity of 1085 mAh g−1 at 0.05 C rate with high mass loading of material (~6-6.5 mg/cm2 of composite) and ~99% initial coulombic efficiency. The composite electrode shows stable cycling performance for more than 100 charge-discharge cycles with specific capacity of ~750 mAh g-1 at a rate of C/3 and coulombic efficiency over 99%. Thus, in the presence of TiS2 additive, long cycle life and improved sulfur utilization of Li-S cells under high current rate (C/3) are demonstrated with high sulfur mass-loading.

Lithium phosphorus oxynitride (Lipon) thin films have been deposited by a plasma-enhanced metalorganic chemical vapor deposition method. Lipon thin films were deposited on approximately 0.2 μm thick Au-coated alumina substrates in a N 2 –H 2 –Ar plasma at 13.56 MHz, a power of 150 W, and at 180 °C using triethyl phosphate [(CH 2 CH 3 ) 3 PO 4 ] and lithium tert -butoxide [(LiOC(CH 3 ) 3 ] precursors. Lipon growth rates ranged from 10 to 42 nm/min and thicknesses varied from 1 to 2.5 μm. X-ray powder diffraction showed that the films were amorphous, and X-ray photoelectron spectroscopy (XPS) revealed approximately 4 at.% N in the films. The ionic conductivity of Lipon was measured by electrochemical impedance spectroscopy to be approximately 1.02 μS/cm, which is consistent with the ionic conductivity of Lipon deposited by radio frequency magnetron sputtering of Li 3 PO 4 targets in either mixed Ar–N 2 or pure N 2 atmosphere. Attempts to deposit Lipon in a N 2 –O 2 –Ar plasma resulted in the growth of Li 3 PO 4 thin films. The XPS analysis shows no C and N atom peaks. Due to the high impedance of these films, reliable conductivity measurements could not be obtained for films grown in N 2 –O 2 –Ar plasma.

Manganese oxide (MnO) nanoparticle clusters embedded in a carbon matrix were deposited using one-step chemical vapor synthesis method for application in lithium ion battery. High resolution transmission electron microscope (HRTEM) and x-ray diffraction show the nanoparticles are polycrystalline with particle size ranging from 5 to 20 nm. EDAX, HRTEM, and X-ray photoelectron spectroscopy (XPS) revealed the presence of carbon in the sample matrix. Galvanostatic discharge-charge (GDC) experiments were performed on the clusters between 3.0 and 0.05 V vs. Li/Li+ at C/2, C/3 and C/5 rates. During the first discharge at C/3 rate, a semi-plateau is observed at ~1.0 V which is corroborated by cyclic voltammetry (CV) and delivered ~100 mAh/g. Then a plateau at 0.5 V yields ~500 mAh/g. An additional 200 mAh/g is obtained from the slopping region from 0.5 to 0.1 V, which the due to the pseudo-capacitance. The initial reversible capacity is ~800 mAh/g at C/3. The first charge curve has two plateaus at ~1.3 V and ~1.5 V corresponds to the oxidation of Mn0 to Mn+2 and Mn+2 to Mn+3/+4, respectively. All subsequent curves show similar pattern. The capacity increases as the cycle number increases for both the discharge and charge. Ex-situ analyses of four identical samples cycled in the CV were carried in the at different cut-off voltages of 0.92 V and 0.28 V during reduction and 1.31 V and 2.13 V during oxidation. Interestingly, all four samples were still polycrystalline. XRD and HRTEM showed that the sample that was stopped 0.28 V (reduction) has the smallest particle size whereas the sample stopped at 2.13 V (oxidation) has the bigger grain size. The (111) reflection of the MnO nanoclusters was always present irrespective of the voltage cut-off. The (200) and (220) reflections of the (MnO) vanished during reduction and reemerged during oxidation and increased in intensity as the voltage increased. HRTEM revealed that carbon was present throughout the GDC and played a key role in the cyclibility of the MnO clusters by improving electronic conductivity. Figure 1

Electrochemical pseudo-capacitor materials that can deliver high power and store high capacity energy for applications that required faster rate performance than traditional energy storage battery are needed. Amorphous Nb2O5 has been evaluated as a pseudo-capacitor. Amorphous thin film (550 nm) was synthesized by RF magnetron sputtering. The morphology of the Nb2O5 nanoparticle thin films was smooth as evaluating in field emission scanning electron microscope (FE-SEM) with nanoparticle size ranged between 5 and 15 nm. A cross-sectional FE-SEM image shows thickness was approximately 550 nm with excellent adhesion to the SS substrates. XPS revealed that the as-deposited materials are Nb2O5. To understand the electrochemical redox reactions, cyclic voltammetry (CV) and galvanostatic discharge-charge (GDC) experiments were performed at different rates. The CVs were performed at scan rates of 0.1, 1, 2, and 5 mV/s. For example, for the scan rate at 1 mV/s a sharp peak current is observed at ~0.85 V during the first cycle which has been assigned to the formation of the solid electrolyte interface (SEI) and reduction of Nb+5 to Nb+4. As the cathodic sweep continues to zero volt no conversion reaction took place. The anodic sweep shows two broad and weak peak currents at ~0.7 and ~1.5 V. During the second cycle, the peak current at ~0.85 V disappeared which is typical of irreversibility and loss of capacity in the first cycle. All subsequent cycles were smooth with quasi rectangular CV curves which indicated the pseudo-capacitive characteristics of amorphous Nb2O5. This is opposite to sharp peak currents typically observed in CV that are characteristics of battery electrodes. Ex-situ XPS were performed on the sample stopped at 1.0 V during the reverse potential sweep and 1.84 V during the forward potential sweep. A very thick SEI layer was observed when the sample was stopped and analyzed at 1.0 V. NbOx was observed after fifteen minutes of sputtering at 1 KeV Ar+ and Nb+4/+5 after 90 min of sputtering. The SEI is composed of carbonates (Li2CO3), aliphatic carbon species, and fluorides (LiF). The capacity observed during the first cycle was 436 mAh/g at C/3 rate. After 100 cycles, the coulumbic efficiency was maintained at 100% and the capacity retention was 160 mAh/g. The materials responded very well to different cycling rates. Figure 1

Nanostructured pyramidal shape ruthenium oxide (Ru+4O2) was studied electrochemically using cyclic voltammetry (CV) and cyclic charge-discharge (CCD) experiments at five different cut-off voltages (1.5, 1.0, 0.80, 0.4, and 0.1 V) versus Li/Li+. CCD experiments performed at cut off voltages of 1.5 V and 1.0 V showed a plateau at approximately 2.1 V that corresponds to 100 and 350 mAh g-1, respectively, with no significant formation of solid electrolyte interface (SEI). CV experiments performed in the same voltage range showed a reduction and an oxidation peak at 2.1 and 2.5 V, respectively, that corroborated the CCD experiments. At cut off voltages below 1.0 V, the CV showed two peaks current at 1.0 V (Ru0/Li2O) and 0.6 V (SEI) during the first forward potential sweep. The SEI disappeared during the second cycle and beyond. On the other hand, during the reverse potential sweep two peak currents are observed at 1.2 V and 2.7 V. The latter represents the oxidation of Ru0 to Ru+4 and the former is assigned to the decomposition of the SEI. The CCD experiments revealed a total capacity of approximately 1200 mAh g-1 (~6 Li+ per mol of Ru+4O2). However, the expected capacity is 806 mAh g-1 (4 Li+ per mol of Ru+4O2) as described by the conversion reaction of lithium with Ru+4O2 (Ru+4O2 + 4Li++4e- Ru0 + 2Li2O). Therefore, there is an excess capacity of ~600 mAh g-1. To understand the source of the excess capacity, CCD experiments were performed in the range of 2.0 to 0.1 V vs. Li/Li+ which revealed that the material is behaving as a pseudo-capacitor. The calculated capacity in this range is only 90 mAh g-1. This value is too small to account for the excess capacity. Figure 1

Residual stresses and texture in La2/3Sr1/3MnO3 (LSMO) thin films have been investigated. The films were deposited on (1 0 0) LaAlO3 (LAO) and (1 0 0) MgO single crystals by liquid delivery-metal organic chemical vapor deposition (LD-MOCVD). X-ray diffraction (XRD) pole figures showed (0 0 1)LSMO//(0 0 1)LAO and (0 0 1)LSMO//(0 0 1)MgO preferred orientation. Residual stresses were calculated using a modified sin2ψ method, crystallite group method (CGM), assuming a biaxial stress state. Compressive stresses on the order of 224 and 1150 MPa were obtained for LSMO films deposited on LAO (LSMO/LAO) and MgO (LSMO/MgO), respectively.

Thin films of tungsten oxide were grown by organometallic chemical vapor deposition (OMCVD) using tetra(allyl)tungsten, W(η3-C3H5)4. X-Ray diffraction (XRD) analyses showed amorphous films at substrate temperatures (Ts) 350°C. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) revealed grain sizes in the range 20–40 nm. In situ electrochemical reduction of WO3.2/ITO (2.0 M HCl) produced a faint blue color in less than 1 s. The maximum coloration efficiency (CE) was found to be 22 cm2/mC at 630 nm. The density of the films decreases from 4.53 to 4.29 g/cm3 after annealing. An optical bandgap (Eg) of ∼3.2 eV was estimated for both as-deposited and annealed films.

Battery energy storage has become a critical component of civil and military operations because of the rapidly growing demands in consumer electronics, electric vehicles and the power-consuming systems carried by soldiers on the battlefield. Currently utilized batteries are flammable and suffer from an insufficient high specific energy, which poses major safety issues creating a tactical burden for the soldiers. The use of solid state batteries may offer enhanced safety and increased energy density. Previous modeling studies of the superionic lithium-rich anti-perovskites conductors focused on Li3OX (X = Cl, Br) structures and reported a variety of the charge transport mechanisms ranging from the low-barrier three-atom hop mechanism involving vacancies, Li hops to the nearest neighbor, Li interstitial dumbbells, and diffusion of the Li+ interstitials in LiCl-deficient Li3OCl that outnumber vacancies by 2–3 orders of magnitude as predicted by the shell model. It is, however, quite challenging to completely remove protons from these anti-perovskite conductors during synthesis, highlighting the importance of understanding the influence of protons on conductivity and electrochemical properties for these superionic lithium-rich anti-perovskite conductors.(1, 2) Born-Oppenheimer molecular dynamics (BOMD) simulations of Li2+xOH1-xCl (0≤x≤1) solid electrolytes were performed in order to gain insights into the mechanism of lithium transport and the influence of H concentration, complementing previous modeling studies of H-free antiperovskites. The simulation cell was comprised of 320 atoms. Density Functional Theory (DFT) calculations were performed with the QUICKSTEP module of the CP2K code, which implements the dual Gaussian and Plane Waves (GPW) method. The gamma point supercell approach was used in combination with 3-dimensioanl Periodic Boundary Conditions (PBC). Calculations were performed using the spin-polarized Perdew-Burke-Ernzerhof (PBE) exchange correlation functional with Grimme’s D3 dispersion correction. BOMD simulations predicted a significant enhancement of the lithium diffusion with the increased fraction of protons in agreement with experimental data. The lithium transport mechanism was found to be closely coupled with the rotation of a relatively short OH-group within the protonated electrolytes. Moreover, lithium jump events were found to be highly-correlated. Figure 1a shows a snapshot of the simulation box. In order to gain further insight into the transport mechanics, the motion of the fastest lithium cations in Li2.5OH0.5Cl solid electrolyte are highlighted with different colors. Overlap between trajectories of the fastest lithium cations shown by red arrows is indicative of the highly-correlated fashion of the lithium jumps.(2) We will also discuss changes of band gaps and band alignments that were calculated using DFT hybrid functionals as markers for electrochemical stability. We anticipate that our findings will reduce the existing confusions and show new avenues for tuning solid electrolyte compositions for further improved Li-ion conductivities. Different aspects of this work were supported by NASA Minority University Research and Education Project (MUREP; NASA grant NNX15AP44A and interagency agreement NND16AA29I with ARL for modeling) and ARPA-E (grant DE-AR0000779). References 1. Y. Li, W. Zhou, S. Xin, S. Li, J. Zhu, X. Lü, Z. Cui, Q. Jia, J. Zhou, Y. Zhao and J. B. Goodenough, Angew. Chem. Int. Ed., 55, 9965 (2016). 2. A.-Y. Song, Y. Xiao, K. Turcheniuk, A. Ramanujapuram, J. Benson, A. Magasinski, M. Oguin, L. Meda, O. Borodin and G. Yushin, (submitted)(2017). Figure 1. A snapshot from MD simulations of Li2.5(OH)0.5Cl (a). Trajectories of the fastest Li+ cations during 10 ps BOMD run of Li2.5OH0.5Cl SSE using different colors to denote distinct Li+ (b). Red arrows show overlap between the Li+ trajectories that is indicative of the Li+ correlated motion for the fastest moving Li+. Figure 1

Room temperature ionic liquids (RTILs) have attracted significant attention due to their potential applications for batteries, super-capacitors, actuators, dye sensitized solar cells and thermoelectrochemical cells. RTILs doped with lithium, sodium, magnesium and zinc salts are of primary interest for battery and hybrid capacitor applications. This presentation will focus on insights into structural and transport properties of the alkylpyrrolidinium-based ionic liquids doped with lithium, sodium, magnesium or zinc bis(trifluoromethansulfonyl)imide (TFSI) salts obtained from molecular dynamics (MD) simulations that utilized the many-body polarizable force field (APPLE&P). After validating the ability of the developed force field to predict ionic conductivity of RTILs doped with Li, Na, Mg and Zn salts, a detailed picture of the metal coordination will be presented. The Li and Na cations were coordinated by 4.7-4.8 oxygen atoms from TFSI anions, while Zn and Mg cations were coordinated by approximately six oxygen atoms from TFSI. In addition to being primarily coordinated by TFSI oxygens, Na cations are also coordinated by fluorine and nitrogen atoms from TFSI to a larger extent than other metal cations. The representative solvates from MD simulations performed at 450 K are shown in Figure 1. The cation-TFSI bidentate vs. monodentate binding motifs and the propensity of salts to form large aggregates were analyzed as a function of temperature. Ionic conductivity, viscosity and self-diffusion coefficients from MD simulations agreed well with experimental data, where available. The cation-TFSI residence times followed the order Na< Li < Mg < Zn. Much longer cation-anion residence times for Zn and Mg compared to those of Na and Li were characteristic of the much slower dissolvation for the doubly charged cations and are expected to result in higher interfacial impedance. This research was partially supported by NASA Minority University Research and Education Project (MUREP; NASA grant NNX15AP44A and interagency agreement NND16AA29I with ARL for modeling). Figure 1. Representative metal solvates at 450 K and MD simulation box. Figure 1

Nanostructured pyramidal shape ruthenium oxide (Ru+4O2) was studied electrochemically using cyclic voltammetry (CV) and cyclic charge-discharge (CCD) experiments. The experiments were performed at five different cut-off voltages (4.0 to 1.5, 1.0, 0.80, 0.4, and 0.1 V) versus Li/Li+. CCD experiments performed from 4.0 to 1.5 V and 4.0 to 1.0 V showed a plateau at approximately 2.1 V that corresponds to 100 and 350 mAh g-1, respectively, with no significant formation of solid electrolyte interface (SEI). Insertion and de-insertion of lithium ions in the crystalline lattice of Ru+4O2 were determined to be the dominant mechanism. CV experiments performed in the same voltage range showed a reduction and an oxidation peak at 2.1 and 2.5 V, respectively, that corroborated the CCD experiments. When the cut off voltage was set below 0.80 V, the CV showed two peak currents at ~1.0 V (Ru0/Li2O) and ~0.6 V (SEI) during the first forward potential sweep. The SEI disappeared during the second cycle and beyond. On the other hand, during the reverse potential sweep two peak currents are observed at ~1.2 V and ~2.7 V. The latter represents the oxidation of Ru0 to Ru+4 and the peak at 1.2 V is assigned to the decomposition of the SEI. The CCD experiment revealed a total capacity of approximately 1200 mAh g-1 (~6 Li+ per mol of Ru+4O2), which was determined in the voltage range from 4.0 to 0.1 V. However, the expected capacity is 806 mAh g-1 (4 Li+ per mol of Ru+4O2) as described by the conversion reaction of lithium with Ru+4O2 (Ru+4O2 + 4Li++4e- Ru0 + 2Li2O). Therefore, there is an excess capacity of ~600 mAh g-1. To understand the source of the excess capacity, CCD experiments were performed in the range of 2.0 to 0.1 V vs. Li/Li+ which revealed that the material is behaving as a capacitor. CV experiments performed in the same voltage range supported the CCD experiments. The calculated storage capacity in this range is only 90 mAh g-1. This value is too small to explain the amount of excess capacity observed in this material. The most possible scenario for the excess capacity is pseudo-capacitive and interfacial storage.

Nanostructure transition metal oxides (MO-type M = Fe, Co, Ni, Cu, . . . ) with rock-salt structure are promising anode materials for lithium ion batteries. These types of materials can store two to three times the capacity of graphite anode (372 mAh g-1) which is the state-of-the-art technology. Here we focus on the growth of Nickel oxide (NiO) prepared by chemical vapor deposition (CVD) directly on current collectors and understanding of the origin of the excess capacity. The synthesis of the NiO nanoplates by CVD directly on the current collectors is ideal for studying the electrochemical properties because they are no interferences from additives. In addition, the direct growth of the materials onto current collectors provides faster mass and electron transport due to the improvement in conductivity across the interfaces and through the materials due to its nanosize. The microstructural characteristics of the as-prepared NiO nanoplates were examined by high resolution transmission electron microscopy which showed that they were arranged randomly on the current collector. Selected area electron diffraction showed that the NiO is polycrystalline with the face-centered cubic crystal structure. The X-ray photoelectron spectroscopy showed that the as-prepared materials are pure NiO. We studied the galvanostatic discharge-charge of the NiO electrode. During the first discharge process from 3.0 V to 0.1 V, a plateau at approximately 0.70 V followed by a gradual decrease to 0.1 V, is observed. This is due to the reduction of Ni2+ to Ni0 and the formation of Li containing organic and solid electrolyte interface (SEI). The first discharge corresponds to approximately 1100 mAh/g which is equivalent to 3 mol of Li per mol of NiO which is more than the expected capacity of according to the conversion reaction: NiIIO + Li0 +2e- ß à LiI 2O + Ni0 (718 mAh/g). The excess capacity of the NiO nanoplates and the cyclic voltammetry will be discussed.

The supercapacitors have emerged as an important energy storage device as they can deliver a high specific power, long cycle life, and much higher charge-discharge rates than a battery. In particular, solid-state supercapacitors have gained worldwide attention as an emerging candidate for smart and efficient energy storage devices due to the increasing demand for miniaturized electronics. Electric double layer capacitors (EDLCs) are the most widely studied class of supercapacitors which physically stores charge by forming an electric double layer at the interfaces between the high surface area carbon electrode and the electrolyte. The conventional EDLCs using high surface area activated carbon electrodes and non-aqueous liquid electrolytes represent the current state of the art. The most common cause of failure of such devices is related to the electrolyte leakage. Most of the past work on EDLCs have been carried out using the liquid electrolytes (aqueous, organic and pure ionic liquid). The gel polymer electrolytes with high ionic mobility and good dimensional/mechanical stability, offer a viable substitute for the liquid electrolytes and they are being used for flexible and solid-state electrochemical energy storage devices. Here, we report the electrochemical performance of high surface area activated carbon based EDLCs using 1-ethyl-3-methylimidazolium dicyanamide (EMImDCA) ionic liquid and its poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP) gel counterpart as electrolytes. The gel electrolyte films were prepared by immobilizing the EMImDCA ionic liquid in PVdF-HFP copolymer matrix by solution casting method. The activated carbon electrodes were prepared by mixing the activated carbon powder with conductive additive (Super C65) and PVdF-HFP binder in a ratio of 8:1:1 (w/w/w), and then the mixture was drop-casted onto a flexible thin graphite sheet which serves as current collector. The solid-state EDLC cells were fabricated by sandwiching the gel electrolyte film between two identical activated carbon electrodes whereas EDLC cells with pure IL were fabricated by using fiberglass separator soaked with IL. The EDLC cells show highly capacitive behavior as evident from the cyclic voltammogram of the cells measured at a scan rate of 20 mV s-1 which is rectangular in shape (Fig 1a). However, gel electrolyte based solid-state cell shows slightly higher resistance, obvious from slight deviation from rectangular shape at both turning potential. Typical galvanostatic charge-discharge characteristic of the EDLC cells at current density of 5 mA cm-2is shown in Fig. 1b. The linear discharge characteristics of the cell further confirms the capacitive behavior of the cells due to formation of an electric double layer at the interfaces. The EDLC cell with pure IL shows specific capacitance of ~98 F g-1 whereas IL-gel based EDLC cell shows specific capacitance of ~86 F g-1, derived from charge-discharge curves at 5 mA cm-2. A comparative performance of the EDLC cells was carried our using the impedance spectroscopy, cyclic voltammetry, and galvanostatic charge-discharge techniques. This paper discusses the results of these comparative studies with pure IL and its PVdF-HFP gel electrolytes. Figure 1

Thin films of La0.67Sr0.33MnO3 (LSMO) have been deposited using liquid-delivery metal-organic chemical vapor deposition (MOCVD). X-ray diffraction (XRD) 2θ/θ scans showed that all the films has a cubic structure. Studies of the in-plane crystallographic orientations (pole figure) revealed an (0 0 1) preferred growth structure on LAO, a weak (1 1 0) texture on Y-ZrO2 (YSZ), a random texture on sapphire (SAP) and silicon (Si). Our attention is focused on residual strain and its deviations from linearity for ɛϕψ vs. sin2ϕ plots. The strain evolution from 0

Crystalline and amorphous thin films of tungsten(VI) oxide can be prepared by chemical vapor deposition using a variety of volatile precursors below 500 °C. Deposition parameters for preparation of WO3 films from tungsten hexacarbonyl [W(CO)6], tungsten hexafluoride (WF6), tungsten ethoxides [W(OEt)x, x = 5, 6] and tetra(allyl)tungsten [W(η3-C3H5)4] are summarized. The electrochromic behavior of these films is comparable with that observed for WO3 films prepared by evaporation, sputtering and electrodeposition. © 1998 John Wiley & Sons, Ltd.

A combination of a.c. susceptometry and Fe57 Mossbauer spectroscopy measurements confirm valence trapped 3D-ferrimagnetically ordered ground states for the title compounds save (A) that orders antiferromagnetically with a very broad maximum in X′m centered at - 50K. Their ground state magnetic behavior is contrasted with the previously demonstrated ferromagnetism of Bu4N{FeIICrIII(ox3} and φ4P{MnIICrIII(ox3)}.

Nanostructure transition metal oxides (MO-type M = Fe, Co, Ni, Cu, . . . ) with rock-salt structure are promising anode materials to be used in lithium ion batteries, when compared to conventional graphite anodes due to their superior Li- ions storage capability. NiO nanostructures were successfully grown onto stainless steel 304 substrates using a low pressure chemical vapor deposition process at 600°C and characterize their morphology-dependent electrochemical behavior at room temperature. Structure and elemental analysis of the NiO nanostructures were confirmed using X-ray diffraction and EDS. Oxidation states and elemental analysis was confirmed with XPS analysis. The electrochemical performances of the NiO electrode were studied using cyclic voltammetry (CV) and galvanostatic charge/discharge (GCD) techniques in LiPF6 with in 1:1:1: EC, DMC, and DC electrolyte in the voltage range of 0.1 - 4.0 V at a constant current of 0.1 mA vs Li/Li+. Solid electrolyte interface (SEI) appeared at the first cycle and disappeared in the subsequent cycles, however two oxidation peaks were observed at 1.63 V and 2.23 V which have been assigned to the depletion of the electrolyte and oxidation of Ni+2, respectively. NiO nanostructures have shown a first-cycle capacity of about 782 mAh/g, which is more than the expected theoretical capacity of 718 mAh/g after the conversion reaction. The origin of the excess capacity is due to the Pseudo-capacitive nature of the materials at low voltages and interfacial charge storage. A loss in capacity in the second discharge is observed which is due to loss of materials. The electrochemical properties of the as synthesized NiO nanostructures were investigated to determine their suitability as anode materials for lithium-ion batteries.

By carefully manipulating and controlling the growth conditions, Ruthenium (Ru) and ruthenium oxide (RuO2) two-dimensional (2-D) nanostructure were self-assembled into a stack of plates on indium tin oxide coated glass substrate. The nanoplates were grown in a horizontal hot-wall metalorganic chemical vapor deposition (MOCVD) from ruthenocene. Each nanoplate has a thickness in the range of 25 - 60 nm and the average area is 1000 x 300 nm2. Each stack of nanoplates is approximately 1.2 m in height. A continuous layer of Ru and RuO2 thin film, which may serve as the growth template, is observed on the bottom of the nanoplate stacks. Field-emission scanning electron microscopy reveals that each stack of nanoplates was grown vertically aligned on the substrate and exhibited elongated shape. Structural properties which were examined by X-ray diffraction show that the nanoplates are polycrystalline.

Lithium phosphorus oxynitride (Lipon) thin films have been deposited by a plasmaenhanced metalorganic chemical vapor deposition (PE-MOCVD) method using triethyl phosphate [(CH2CH3)3PO4] and lithium tert-butoxide [(LiOC(CH3)3] precursors. Growth rates were between 100 and 415 Å/min, and thicknesses ranged from 1 to 2.5 μm. X-ray powder diffraction showed that the films were amorphous, and X-ray photoelectron spectroscopy revealed approximately 6.9 at.% carbon in the films. The ionic conductivity of Lipon was measured using electrochemical impedance spectroscopy (EIS) and approximately 1.02 μS/cm was obtained, which is consistent with the ionic conductivity of Lipon deposited by radio frequency magnetron sputtering of Li3PO4 targets. An all-solid-state thin-film lithium microbattery such as Li/Lipon/LiCoO2/Au/substrate was successfully fabricated with Lipon deposited by PE-MOCVD. The battery has a capacity of ca. 22 μAh/cm2μm.

Thin films of La0.67Sr0.33MnO3 (LSMO) were prepared at 670 °C on LaAlO3 (LAO) and SrTiO3 (STO) substrates by liquid-delivery metalorganic chemical vapor deposition. X-ray diffraction analysis 2¸/¸ and pole figure scans showed that the films are epitaxial with (001)LSMO//(001)LAO and (001)LSMO//(001)STO. The crystal structure of LSMO/LAO was indexed as face-centered cubic with a double cell and LSMO/STO as simple cubic. Electron microscopy revealed square facets and elongated grain features. Films heat-treated between 700 and 800 °C on LAO resulted in a structural change, while those on STO showed an increase in texture.

Lithium-ion batteries have application in wide range of portable devices like cell phones, portable computers, camcorders, I-pods, peristaltic pumps, heart assist devices, oil and gas pipeline robots, seismic survey sensors, tactical communication radios and thermal imaging equipment, and satellite power sources.1,2 They are now projected to automotive industry for electric vehicles (EV’s) and hybrid electric vehicles.3 The common electrode materials of conventional lithium ion batteries are graphite (anode), and LiCoO2 or LiFePO4 (cathode). They have certain limitations such as low capacities, safety issues and cost which hinder their applications.2 RuO2 plays an important role in the family of metal oxides because of its interesting properties such as metallic conductivity, high chemical and thermal stability, catalytic activities, electrochemical redox properties, and field emitting behavior.4 It is one of the most successful electrode material for supercapacitors because of its wide potential window of highly reversible redox reactions, remarkably high specific capacitance, and a very long cycle life.5 In this material, conversion reaction using nanoparticles is also possible and high capacity of 1130 mAh g-1, corresponds to the storage of 5.6 moles of Li ions per mole of RuO2 and high coulombic efficiency (98%) has been observed.6But the material can withstand up to only three cycles due to a large volume expansion. We have improved the cycle life performance of RuO2 by directly depositing the material on stainless steel current collectors via low pressure chemical vapor deposition. RuO2 nano-architectures were characterized by powder x-ray diffraction and field emission scanning electron microscope. Galvanostatic charge-discharge experiments were performed versus lithium metal in the voltage range 4 - 0.1V. As deposited RuO2 nano-architectures were cycled well over 20 cycles at high capacity beyond the theoretical limit of 806 mAh g-1(Fig. 1). The origin of the extra capacity will be discussed. Acknowledgements:This work was supported by NSF PREM Award Number DMR-0934111 and NSF-EPSCoR Cooperative Agreement No EPS-1003897 References: [1]. J.-M. Tarascon, M. Armand. Nature 2001, 414, 359-367. [2]. A. Manthiram. J. Phys. Chem. Lett. 2011, 2, 176–184. [3]. J.-M. Tarascon, N. Recham, M. Armand, J.-N. Chotard, P. Barpanda, W. Walker, L. Dupont. Chem. Mater. 2010, 22, 724–739. [4]. X. Wang, R. G. Gordon. Cryst. Growth Des. 2013, 13, 1316−1321 and references therein. [5]. V. D. Patake, C. D. Lokhande, O.-S. Joo. Applied Surface Science 2009, 255, 4192–4196. [6] P. Balaya, H. Li, L. Kienle, J. Maier. Adv. Funct. Mater. 2003, 13, 621-625.

The electrochemical properties of oxygen-deficient tungsten oxide (W18O49) nanowires were investigated. The nanowires were prepared via a simple thermal evaporation method. The as-deposited nanowires were 60–90 nm in diameter and several micrometers long as measured by field-emission scanning electron microscopy. The crystal structure was indexed to the monoclinic W18O49 phase. The electrochemical properties of the nanowires and WO3 bulk particles were examined by cyclic voltammetry between 2 and 4 V vs Li/Li+. We found that the nanowires cycle better than the bulk particles.

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Adherent, polycrystalline films containing mixtures of SrRuO3, Sr2gRuO4 and RuO2 were deposited on silicon and alumina substrates by hot wall chemical vapor deposition from bis(2, 4-dimethylpentadienyl) ruthenium and Sr(thd)2 between 650 and 700°C. The as-deposited mixed phase films, which contained polycrystalline phases of RuO2 and amorphous phases of the mixed oxide exhibited resistivities between 6.5 and 20 mΩcm. Rims were annealed at 1000°C under oxygen/argon ambient. The annealed films exhibited higher resistivities than their as-deposited counterparts and a substrate dependence of phases present was observed. The decrease in conductivity upon annealing for films on both substrates is attributed to the formation of volatile ruthenium oxides. The higher conductivity of post-annealed samples on alumina (compared to samples prepared and annealed on Si) is attributed to Sr uptake by the substrate and thus a suppression of Sr2RuO4 formation.

Thin films of polycrystalline RuO2 were deposited from bis(2,4-dimethylpentadienyl) ruthenium, (η5-2, 4-Me2C5H5)2Ru (1) and ruthenocene (2) on quartz and silicon substrates between 200 and 500°C under Ar/O2 or O2. Films deposited from 1 were more adherent than those grown from 2 under the same conditions, however, none of the films were particularly adherent when O2 was used as a carrier gas. SEM revealed a columnar structure for both precursors with grain size ranging from 0.15 – 1 5μ. Crystallinity increased after annealing the films to 800°C. Resistivity decreased as the annealing temperature increased.