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Using molecular dynamics simulations, small-angle neutron scattering, and a variety of spectroscopic techniques, we evaluated the ion solvation and transport behaviors in aqueous electrolytes containing bis(trifluoromethanesulfonyl)imide. We discovered that, at high salt concentrations (from 10 to 21 mol/kg), a disproportion of cation solvation occurs, leading to a liquid structure of heterogeneous domains with a characteristic length scale of 1 to 2 nm. This unusual nano-heterogeneity effectively decouples cations from the Coulombic traps of anions and provides a 3D percolating lithium-water network, via which 40% of the lithium cations are liberated for fast ion transport even in concentration ranges traditionally considered too viscous. Due to such percolation networks, superconcentrated aqueous electrolytes are characterized by a high lithium-transference number (0.73), which is key to supporting an assortment of battery chemistries at high rate. The in-depth understanding of this transport mechanism establishes guiding principles to the tailored design of future superconcentrated electrolyte systems.

Lithium-ion batteries have emerged as the preferred type of rechargeable batteries, but there is a need to improve the performance of the electrolytes therein. Specifically, the challenge is to obtain electrolytes with the mechanical rigidity of solids but with liquid-like conductivities. In this study, we report a class of nanostructured gels that are able to offer this unique combination of properties. The gels are prepared by utilizing the synergistic interactions between a molecular gelator, 1,3:2,4-di-O-methyl-benzylidene-d-sorbitol (MDBS), and a nanoscale particulate material, fumed silica (FS). When MDBS and FS are combined in a liquid consisting of propylene carbonate with dissolved lithium perchlorate salt, the liquid electrolyte is converted into a free-standing gel due to the formation of a strong MDBS-FS network. The gels exhibit elastic shear moduli around 1000 kPa and yield stresses around 11 kPa-both values considerably exceed those obtainable by MDBS or FS alone in the same liquid. At the same time, the gel also exhibits electrochemical properties comparable to the parent liquid, including a high ionic conductivity (~5 × 10(-3) S/cm at room temperature) and a wide electrochemical stability window (up to 4.5 V).

Micro-sized silicon anodes can significantly increase the energy density of lithium-ion batteries with low cost. However, the large silicon volume changes during cycling cause cracks for both organic-inorganic interphases and silicon particles. The liquid electrolytes further penetrate the cracked silicon particles and reform the interphases, resulting in huge electrode swelling and quick capacity decay. Here we resolve these challenges by designing a high-voltage electrolyte that forms silicon-phobic interphases with weak bonding to lithium-silicon alloys. The designed electrolyte enables micro-sized silicon anodes (5 µm, 4.1 mAh cm−2) to achieve a Coulombic efficiency of 99.8% and capacity of 2175 mAh g−1 for >250 cycles and enable 100 mAh LiNi0.8Co0.15Al0.05O2 pouch full cells to deliver a high capacity of 172 mAh g−1 for 120 cycles with Coulombic efficiency of >99.9%. The high-voltage electrolytes that are capable of forming silicon-phobic interphases pave new ways for the commercialization of lithium-ion batteries using micro-sized silicon anodes. Micro-sized silicon are promising anode materials due to low-cost and high-energy, yet their application is hindered by inaccessible electrolytes. Here, the authors report sulfolane-based electrolytes that form silicon-phobic interphases and enable high-voltage pouch cells to achieve superior cycle life. [ABSTRACT FROM AUTHOR]

The formation of lithiophobic inorganic solid electrolyte interphase (SEI) on Li anode and cathode electrolyte interphase (CEI) on the cathode is beneficial for high‐voltage Li metal batteries. However, in most liquid electrolytes, the decomposition of organic solvents inevitably forms organic components in the SEI and CEI. In addition, organic solvents often pose substantial safety risks due to their high volatility and flammability. Herein, an organic‐solvent‐free eutectic electrolyte based on low‐melting alkali perfluorinated‐sulfonimide salts is reported. The exclusive anion reduction on Li anode surface results in an inorganic, LiF‐rich SEI with high capability to suppress Li dendrite, as evidenced by the high Li plating/stripping CE of 99.4% at 0.5 mA cm−2 and 1.0 mAh cm−2, and 200‐cycle lifespan of full LiNi0.8Co0.15Al0.05O2 (2.0 mAh cm−2) || Li (20 µm) cells at 80 °C. The proposed eutectic electrolyte is promising for ultrasafe and high‐energy Li metal batteries. [ABSTRACT FROM AUTHOR]

Rechargeable halide-ion batteries (HIBs) are good candidates for large-scale due to their appealing energy density, low cost, and dendrite-free features. However, state-of-the-art electrolytes limit the HIBs' performance and cycle life. Here, via experimental measurements and modelling approach, we demonstrate that the dissolutions in the electrolyte of transition metal and elemental halogen from the positive electrode and discharge products from the negative electrode cause the HIBs failure. To circumvent these issues, we propose the combination of fluorinated low-polarity solvents with a gelation treatment to prevent dissolutions at the interphase, thus, improving the HIBs' performance. Using this approach, we develop a quasi-solid-state Cl-ion-conducting gel polymer electrolyte. This electrolyte is tested in a single-layer pouch cell configuration with an iron oxychloride-based positive electrode and a lithium metal negative electrode at 25 °C and 125 mA g–1. The pouch delivers an initial discharge capacity of 210 mAh g–1 and a discharge capacity retention of almost 80% after 100 cycles. We also report assembly and testing of fluoride-ion and bromide-ion cells using quasi-solid-state halide-ion-conducting gel polymer electrolyte. State-of-the-art electrolytes limit the cycle life of halide-ion batteries. Here, the authors report a fluorinated low-polar gel polymer electrolyte capable of improving the stability of the electrolyte and electrode interphases to boost battery performance. [ABSTRACT FROM AUTHOR]

Electrolyte engineering is crucial for developing high‐performance lithium metal batteries (LMB). Here, we synthesized two cosolvents methyl bis(fluorosulfonyl)imide (MFSI) and 3,3,4,4‐tetrafluorotetrahydrofuran (TFF) with significantly different reduction potentials and add them into LiFSI‐DME electrolytes. The LiFSI/TFF‐DME electrolyte gave an average Li Coulombic efficiency (CE) of 99.41 % over 200 cycles, while the average Li CEs for MFSI‐based electrolyte is only 98.62 %. Additionally, the TFF‐based electrolytes exhibited a more reversible performance than the state‐of‐the‐art fluorinated 1,4‐dimethoxylbutane electrolyte in both Li||Cu half‐cell and anode‐free Cu||LiNi0.8Mn0.1Co0.1O2 full cell. More importantly, the decomposition product from bis(fluorosulfonyl)imide anion could react with ether solvent, which destroyed the SEI, thus decreasing cell performance. These key discoveries provide new insights into the rational design of electrolyte solvents and cosolvents for LMB. [ABSTRACT FROM AUTHOR]

The instability of carbonate electrolyte with metallic Li greatly limits its application in high‐voltage Li metal batteries. Here, a "salt‐in‐salt" strategy is applied to boost the LiNO3 solubility in the carbonate electrolyte with Mg(TFSI)2 carrier, which enables the inorganic‐rich solid electrolyte interphase (SEI) for excellent Li metal anode performance and also maintains the cathode stability. In the designed electrolyte, both NO3− and PF6− anions participate in the Li+‐solvent complexes, thus promoting the formation of inorganic‐rich SEI. Our designed electrolyte has achieved a superior Li CE of 99.7 %, enabling the high‐loading NCM811||Li (4.5 mAh cm−2) full cell with N/P ratio of 1.92 to achieve 84.6 % capacity retention after 200 cycles. The enhancement of LiNO3 solubility by divalent salts is universal, which will also inspire the electrolyte design for other metal batteries. [ABSTRACT FROM AUTHOR]

The capacity of transition metal oxide cathode for Li‐ion batteries can be further enhanced by increasing the charging potential. However, these high voltage cathodes suffer from fast capacity decay because the large volume change of cathode breaks the active materials and cathode‐electrolyte interphase (CEI), resulting in electrolyte penetration into broken active materials and continuous side reactions between cathode and electrolytes. Herein, a robust LiF‐rich CEI was formed by potentiostatic reduction of fluorinated electrolyte at a low potential of 1.7 V. By taking LiCoO2 as a model cathode, we demonstrate that the LiF‐rich CEI maintains the structural integrity and suppresses electrolyte penetration at a high cut‐off potential of 4.6 V. The LiCoO2 with LiF‐rich CEI exhibited a capacity of 198 mAh g−1 at 0.5C and an enhanced capacity retention of 63.5 % over 400 cycles as compared to the LiF‐free LiCoO2 with only 17.4 % of capacity retention. [ABSTRACT FROM AUTHOR]

The instability of sulfide solid electrolytes to Li anode and high‐voltage LiNi0.8Mn0.1Co0.1O2 (NMC811) cathodes limits the cyclic performance of all‐solid‐state lithium battery (ASSLB). Herein, the stability of Li6PS5Cl against Li anode is enhanced by mixing a small amount (0.32 wt%) of CuF2‐LiNO3 (CL) into Li6PS5Cl electrolyte layer to in‐situ form a mixed‐conductive‐lithiophobic and self‐healing LiF‐Li3N‐Cu solid electrolyte interphase (SEI) at Li6PS5Cl‐CL/Li interface. The critical current density (CCD) of Li6PS5Cl‐CuF2‐LiNO3 increases to 1.4 mA cm–2/1.4 mAh cm–2 at room temperature, which is much higher than that of pristine Li6PS5Cl (0.4 mA cm–2/0.4 mAh cm–2) even though mixing 0.32 wt% CL into Li6PS5Cl slightly reduces the ionic conductivity from 2.9 × 10–3 to 1.5 × 10–3 S cm–1. The compatibility of Li6PS5Cl‐CL electrolyte to single‐crystalline NMC811 (S‐NMC811) is further enhanced by adding a small amount (0.02 wt%) of AlF3 into Li6PS5Cl‐CL forming Li6PS5Cl‐CuF2‐LiNO3‐AlF3 (Li6PS5Cl‐CLA) as a cathode electrolyte and by doing Cl– on S‐NMC811 (Cl@S‐NMC811) surface. The Cl@S‐NMC811‐Li6PS5Cl‐CLA|Li6PS5Cl‐CL|Li cells with areal capacity of 2.55 mAh cm‐2 achieve a capacity retention of 69.4% after 100 cycles at 1C (1C = 200 mAh g‐1). Adding a small amount of SEI and cathode/electrolyte interphase (CEI) former into the sulfide electrolytes with minimal reduction (48.3%) of ionic conductivity is an effective method to enhance the performance of ASSLB. [ABSTRACT FROM AUTHOR]

Rechargeable Zn‐ion batteries (ZIBs) are widely regarded as promising candidates for large‐scale energy storage applications. Like most multivalent battery systems (based on Zn, Mg, Ca, etc.), further progress in ZIB development relies on the discovery and design of novel cathode hosts capable of reversible Zn2+ (de)intercalation. Herein, this work employs VPO4F as a ZIB cathode and explores ensuing intercalation mechanisms along with interfacial dynamics during cycling to quantify the water dynamics in concentrated electrolytes and/or hybrid aqueous‐non aqueous (HANEs) electrolyte(s). Like most oxide‐based cathode materials, proton (H+) intercalation dominates electrochemical activity during discharge of ZnxHyVPO4F in aqueous media due to the hydroxylated nature of the interface. Such H+ electrochemistry diminishes low‐rate and/or long‐term electrochemical performance of ZIBs which inhibits implementation for practical applications. Thus, quantification of the water dynamics in various electrolytes is demonstrated for the first time. Detailed investigations of water mobility in various concentrated electrolytes and HANEs systems enable the design of an electrolyte that enhances aqueous anodic stability and suppresses water/proton activity during discharge. Tuning Zn2+/H+ intercalation kinetics simultaneously allows for a high voltage (1.9 V) and long‐lasting aqueous zinc‐ion battery: Zn|Zn(OTf)2·nH2O‐PC|ZnxHyVPO4F. [ABSTRACT FROM AUTHOR]

Since the advent of the Li ion batteries (LIBs), the energy density has been tripled, mainly attributed to the increase of the electrode capacities. Now, the capacity of transition metal oxide cathodes is approaching the limit due to the stability limitation of the electrolytes. To further promote the energy density of LIBs, the most promising strategies are to enhance the cut-off voltage of the prevailing cathodes or explore novel high-capacity and high-voltage cathode materials, and also replacing the graphite anode with Si/Si–C or Li metal. However, the commercial ethylene carbonate (EC)-based electrolytes with relatively low anodic stability of ∼4.3 V vs. Li+/Li cannot sustain high-voltage cathodes. The bottleneck restricting the electrochemical performance in Li batteries has veered towards new electrolyte compositions catering for aggressive next-generation cathodes and Si/Si–C or Li metal anodes, since the oxidation-resistance of the electrolytes and the in situ formed cathode electrolyte interphase (CEI) layers at the high-voltage cathodes and solid electrolyte interphase (SEI) layers on anodes critically control the electrochemical performance of these high-voltage Li batteries. In this review, we present a comprehensive and in-depth overview on the recent advances, fundamental mechanisms, scientific challenges, and design strategies for the novel high-voltage electrolyte systems, especially focused on stability issues of the electrolytes, the compatibility and interactions between the electrolytes and the electrodes, and reaction mechanisms. Finally, novel insights, promising directions and potential solutions for high voltage electrolytes associated with effective SEI/CEI layers are proposed to motivate revolutionary next-generation high-voltage Li battery chemistries. [ABSTRACT FROM AUTHOR]

Aqueous Zn batteries promise high energy density but suffer from Zn dendritic growth and poor low‐temperature performance. Here, we overcome both challenges by using an eutectic 7.6 m ZnCl2 aqueous electrolyte with 0.05 m SnCl2 additive, which in situ forms a zincophilic/zincophobic Sn/Zn5(OH)8Cl2⋅H2O bilayer interphase and enables low temperature operation. Zincophilic Sn decreases Zn plating/stripping overpotential and promotes uniform Zn plating, while zincophobic Zn5(OH)8Cl2⋅H2O top‐layer suppresses Zn dendrite growth. The eutectic electrolyte has a high ionic conductivity of ≈0.8 mS cm−1 even at −70 °C due to the distortion of hydrogen bond network by solvated Zn2+ and Cl−. The eutectic electrolyte enables Zn∥Ti half‐cell a high Coulombic efficiency (CE) of >99.7 % for 200 cycles and Zn∥Zn cell steady charge/discharge for 500 h with a low overpotential of 8 mV at 3 mA cm−2. Practically, Zn∥VOPO4 batteries maintain >95 % capacity with a CE of >99.9 % for 200 cycles at −50 °C, and retain ≈30 % capacity at −70 °C of that at 20 °C. [ABSTRACT FROM AUTHOR]

Water‐in‐salt electrolytes (WISE) have largely widened the electrochemical stability window (ESW) of aqueous electrolytes by formation of passivating solid electrolyte interphase (SEI) on anode and also absorption of the hydrophobic anion‐rich double layer on cathode. However, the cathodic limiting potential of WISE is still too high for most high‐capacity anodes in aqueous sodium‐ion batteries (ASIBs), and the cost of WISE is also too high for practical application. Herein, a low‐cost 19 m (m: mol kg−1) bi‐salts WISE with a wide ESW of 2.8 V was designed, where the low‐cost 17 m NaClO4 extends the anodic limiting potential to 4.4 V, while the fluorine‐containing salt (2 m NaOTF) extends the cathodic limiting potential to 1.6 V by forming the NaF–Na2O–NaOH SEI on anode. The 19 m NaClO4–NaOTF–H2O electrolyte enables a 1.75 V Na3V2(PO4)3∥Na3V2(PO4)3 full cell to deliver an appreciable energy density of 70 Wh kg−1 at 1 C with a capacity retention of 87.5 % after 100 cycles. [ABSTRACT FROM AUTHOR]

This document is a correction notice for an article titled "High voltage electrolytes for lithium-ion batteries with micro-sized silicon anodes" published in Nature Communications. The correction addresses errors in the labeling of y-axis labels for certain figures and the caption for another figure. The original article has been corrected, and supplementary information is available online. The authors of the article are listed as Ai-Min Li, Zeyi Wang, Travis P. Pollard, Weiran Zhang, Sha Tan, Tianyu Li, Chamithri Jayawardana, Sz-Chian Liou, Jiancun Rao, Brett L. Lucht, Enyuan Hu, Xiao-Qing Yang, Oleg Borodin, and Chunsheng Wang. [Extracted from the article]

In carbonate electrolytes, the organic–inorganic solid electrolyte interphase (SEI) formed on the Li‐metal anode surface is strongly bonded to Li and experiences the same volume change as Li, thus it undergoes continuous cracking/reformation during plating/stripping cycles. Here, an inorganic‐rich SEI is designed on a Li‐metal surface to reduce its bonding energy with Li metal by dissolving 4m concentrated LiNO3 in dimethyl sulfoxide (DMSO) as an additive for a fluoroethylene‐carbonate (FEC)‐based electrolyte. Due to the aggregate structure of NO3− ions and their participation in the primary Li+ solvation sheath, abundant Li2O, Li3N, and LiNxOy grains are formed in the resulting SEI, in addition to the uniform LiF distribution from the reduction of PF6− ions. The weak bonding of the SEI (high interface energy) to Li can effectively promote Li diffusion along the SEI/Li interface and prevent Li dendrite penetration into the SEI. As a result, our designed carbonate electrolyte enables a Li anode to achieve a high Li plating/stripping Coulombic efficiency of 99.55 % (1 mA cm−2, 1.0 mAh cm−2) and the electrolyte also enables a Li||LiNi0.8Co0.1Mn0.1O2 (NMC811) full cell (2.5 mAh cm−2) to retain 75 % of its initial capacity after 200 cycles with an outstanding CE of 99.83 %. [ABSTRACT FROM AUTHOR]

The electrolytes in lithium metal batteries have to be compatible with both lithium metal anodes and high voltage cathodes, and can be regulated by manipulating the solvation structure. Herein, to enhance the electrolyte stability, lithium nitrate (LiNO3) and 1,1,2,2‐tetrafuoroethyl‐2′,2′,2′‐trifuoroethyl(HFE) are introduced into the high‐concentration sulfolane electrolyte to suppress Li dendrite growth and achieve a high Coulombic efficiency of >99 % for both the Li anode and LiNi0.8Mn0.1Co0.1O2 (NMC811) cathodes. Molecular dynamics simulations show that NO3− participates in the solvation sheath of lithium ions enabling more bis(trifluoromethanesulfonyl)imide anion (TFSI−) to coordinate with Li+ ions. Therefore, a robust LiNxOy−LiF‐rich solid electrolyte interface (SEI) is formed on the Li surface, suppressing Li dendrite growth. The LiNO3‐containing sulfolane electrolyte can also support the highly aggressive LiNi0.8Mn0.1Co0.1O2 (NMC811) cathode, delivering a discharge capacity of 190.4 mAh g−1 at 0.5 C for 200 cycles with a capacity retention rate of 99.5 %. [ABSTRACT FROM AUTHOR]

Over the past decades, Li-ion battery (LIB) has turned into one of the most important advances in the history of technology due to its extensive and in-depth impact on our life. Its omnipresence in all electric vehicles, consumer electronics and electric grids relies on the precisely tuned electrochemical dynamics and interactions among the electrolytes and the diversified anode and cathode chemistries therein. With consumers' demand for battery performance ever increasing, more and more stringent requirements are being imposed upon the established equilibria among these LIB components, and it became clear that the state-of-the-art electrolyte systems could no longer sustain the desired technological trajectory. Driven by such gap, researchers started to explore more unconventional electrolyte systems. From superconcentrated solvent-in-salt electrolytes to solid-state electrolytes, the current research realm of novel electrolyte systems has grown to unprecedented levels. In this review, we will avoid discussions on current state-of-the-art electrolytes but instead focus exclusively on unconventional electrolyte systems that represent new concepts. [ABSTRACT FROM AUTHOR]

Development of electrolytes that simultaneously have high ionic conductivity, wide electrochemical window, and lithium dendrite suppression ability is urgently required for high‐energy lithium‐metal batteries (LMBs). Herein, an electrolyte is designed by adding a countersolvent into LiFSI/DMC (lithium bis(fluorosulfonyl)amide/dimethyl carbonate) electrolytes, forming countersolvent electrolytes, in which the countersolvent is immiscible with the salt but miscible with the carbonate solvents. The solvation structure and unique properties of the countersolvent electrolyte are investigated by combining electroanalytical technology with a Molecular Dynamics simulation. Introducing the countersolvent alters the coordination shell of Li+ cations and enhances the interaction between Li+ cations and FSI− anions, which leads to the formation of a LiF‐rich solid electrolyte interphase, arising from the preferential reduction of FSI− anions. Notably, the countersolvent electrolyte suppresses Li dendrites and enables stable cycling performance of a Li||NCM622 battery at a high cut‐off voltage of 4.6 V at both 25 and 60 °C. This study provides an avenue to understand and design electrolytes for high‐energy LMBs in the future. [ABSTRACT FROM AUTHOR]

Residual Li compounds are inevitably present in the form of Li2O, LiOH, and Li2CO3 on the surface of layered cathode materials, which not only causes slurry gelation in the cathode‐coating process but also degrades liquid electrolyte in the batteries. Owing to their strong alkaline nature, the residual Li compounds can react with acidic LiPF6 to form Li3PO4 and LiF, two of the main components of robust solid electrolyte interphases. By demonstrating LiNi0.80Co0.10Mn0.10O2 (NCM811) as an example in this work, we simply dissolved a small amount of LiPF6 into the cathode‐coating slurry, finding that as the amount of LiPF6 is controlled in the 0.5–1.0 wt % range versus the mass of NCM811, the LiPF6 additive not only improves the cycling stability but also enhances rate capability of the Li/NCM811 cells. The former is because the strongly alkaline residual Li compounds react with acidic LiPF6 to form stable Li3PO4 and LiF. The latter is attributed to a reduction in the surface layer resistance on the cathode, as suggested by the results of surface chemistry and impedance analyses. Added value: Dissolving a small amount of LiPF6 into the cathode slurry effectively removes residual Li compounds, which consequently improves the cycling stability and rate capability of layered cathode materials. [ABSTRACT FROM AUTHOR]

Abstract: The effect of H2O in electrolytes and in electrode lattices on the thermodynamics and kinetics of reversible multivalent‐ion intercalation chemistry based on a model platform of layered VOPO4 has been investigated. The presence of H2O at the electrolyte/electrode interface plays a key role in assisting Zn2+ diffusion from electrolyte to the surface, while H2O in the lattice structure alters the working potential. More importantly, a dynamic equilibrium between bulk electrode and electrolyte is eventually reached for H2O transport during the charge/discharge cycles, with the water activity serving as the key parameter determining the direction of water movement and the cycling stability. [ABSTRACT FROM AUTHOR]

Abstract: Electrolytes that are able to reversibly deposit/strip Mg are crucial for rechargeable Mg batteries. The most studied complex electrolytes based on Lewis acid‐base chemistry are expensive, difficult to be synthesized, and show limited anodic stability. Conventional electrolytes using simple salts such as Mg(TFSI)2 can be readily synthesized, but Mg deposition/stripping in these simple salt electrolytes is accompanied by a large overpotential due to the formation of a surface layer on the Mg metal with a low Mg ion conductivity. Here the overpotential for Mg deposition/stripping in a simple salt, Mg(TFSI)2‐1,2‐dimethoxyethane (DME), electrolyte is significantly reduced by adding a small concentration of iodine (≤50 × 10−3 m) as an additive. Mechanism studies demonstrate that an Mg ion conductive solid MgI2 layer is formed on the surface of the Mg metal and acts as a solid electrolyte interface. With the Mg(TFSI)2‐DME‐I2 electrolyte, a very small voltage hysteresis is achieved in an Mg‐S full cell. [ABSTRACT FROM AUTHOR]

The redox chemistry of magnesium and its application in rechargeable Mg batteries has received increasing attention owing to the unique benefits of Mg metal electrodes, namely high reversibility without dendrite formation, low reduction potentials, and high specific capacities. The Mg/S couple is of particular interest owing to its high energy density and low cost. Previous reports have confirmed the feasibility of a rechargeable Mg/S battery; however, only limited cycling stability was achieved, and the complicated procedure for the preparation of the electrolytes has significantly compromised the benefits of Mg/S chemistry and hindered the development of Mg/S batteries. Herein, we report the development of the first rechargeable Mg/S battery with a MgTFSI2/MgCl2/DME electrolyte (DME=1,2-dimethoxyethane, TFSI=bis(trifluoromethanesulfonyl)imide) and realize the best cycling stability among all reported Mg/S batteries by suppressing polysulfide dissolution. Mechanistic studies show that the battery works via S0/MgS x redox processes and that the large voltage hysteresis is mainly due to the Mg anode overpotential. [ABSTRACT FROM AUTHOR]

A 2.9 V intrinsic safe aqueous LiNi0.5Mn1.5O4/Mo6S8 full cell delivers 80 W h kg−1 energy density with capacity decay of 0.075% per cycle (5 C). After the electrolyte pH value adjustment, almost full capacity of LiNi0.5Mn1.5O4 (125 mA h kg−1) is achieved, and 126 W h kg−1 energy density is provided for LiNi0.5Mn1.5O4/Mo6S8 cell, representing one of the highest voltage and energy density among all the aqueous batteries. [ABSTRACT FROM AUTHOR]

Aluminum metal is a promising anode material for next generation rechargeable batteries owing to its abundance, potentially dendrite-free deposition, and high capacity. The rechargeable aluminum/sulfur (Al/S) battery is of great interest owing to its high energy density (1340 Wh kg−1) and low cost. However, Al/S chemistry suffers poor reversibility owing to the difficulty of oxidizing AlS x. Herein, we demonstrate the first reversible Al/S battery in ionic-liquid electrolyte with an activated carbon cloth/sulfur composite cathode. Electrochemical, spectroscopic, and microscopic results suggest that sulfur undergoes a solid-state conversion reaction in the electrolyte. Kinetics analysis identifies that the slow solid-state sulfur conversion reaction causes large voltage hysteresis and limits the energy efficiency of the system. [ABSTRACT FROM AUTHOR]

A new super-concentrated aqueous electrolyte is proposed by introducing a second lithium salt. The resultant ultra-high concentration of 28 m led to more effective formation of a protective interphase on the anode along with further suppression of water activities at both anode and cathode surfaces. The improved electrochemical stability allows the use of TiO2 as the anode material, and a 2.5 V aqueous Li-ion cell based on LiMn2O4 and carbon-coated TiO2 delivered the unprecedented energy density of 100 Wh kg−1 for rechargeable aqueous Li-ion cells, along with excellent cycling stability and high coulombic efficiency. It has been demonstrated that the introduction of a second salts into the 'water-in-salt' electrolyte further pushed the energy densities of aqueous Li-ion cells closer to those of the state-of-the-art Li-ion batteries. [ABSTRACT FROM AUTHOR]

The use of sulfur in the next generation Li-ion batteries is currently precluded by its poor cycling stability caused by irreversible Li2S formation and the dissolution of soluble polysulfides in organic electrolytes that leads to parasitic cell reactions. Here, a new C/S cathode material comprising short-chain sulfur species (predominately S2) confined in carbonaceous subnanometer and the unique charge mechanism for the subnano-entrapped S2 cathodes are reported. The first charge-discharge cycle of the C/S cathode in the carbonate electrolyte forms a new type of thiocarbonate-like solid electrolyte interphase (SEI). The SEI coated C/S cathode stably delivers ≈600 mAh g−1 capacity over 4020 cycles (0.0014% loss cycle−1) at ≈100% Coulombic efficiency. Extensive X-ray photoelectron spectroscopy analysis of the discharged cathodes shows a new type of S2 species and a new carbide-like species simultaneously, and both peaks disappear upon charging. These data suggest a new sulfur redox mechanism involving a separated Li+/S2− ion couple that precludes Li2S compound formation and prevents the dissolution of soluble sulfur anions. This new charge/discharge process leads to remarkable cycling stability and reversibility. [ABSTRACT FROM AUTHOR]

A rechargeable hybrid Mg2+/Li+ battery is designed by coupling a dendrite‐free magnesium anode with an electrolyte‐compatible cathode in a mixed Mg2+/Li+ electrolyte. Due to the highly reversible lithiation/delithiation of the cathode and Mg deposition/dissolution in the electrolyte, the battery demonstrates the best overall performance among reported magnesium‐ion batteries and mixed‐ion batteries in terms of cycling stability, specific capacity, specific energy, and rate capability. [ABSTRACT FROM AUTHOR]

Rechargeable Li–S batteries are regarded as one of the most promising next‐generation energy‐storage systems. However, the inevitable formation of Li dendrites and the shuttle effect of lithium polysulfides significantly weakens electrochemical performance, preventing its practical application. Herein, a new class of localized high‐concentration electrolyte (LHCE) enabled by adding inert fluoroalkyl ether of 1H,1H,5H‐octafluoropentyl‐1,1,2,2‐tetrafluoroethyl ether into highly‐concentrated electrolytes (HCE) lithium bis(fluorosulfonyl) imide/dimethoxyether (DME) system is reported to suppress Li dendrite formation and minimize the solubility of the high‐order polysulfides in electrolytes, thus reducing the amount of electrolyte in cells. Such a unique LHCE can achieve a high coulombic efficiency of Li plating/stripping up to 99.3% and completely suppressing the shuttling effect, thus maintaining a S cathode capacity of 775 mAh g−1 for 150 cycles with a lean electrolyte of 4.56 g A−1 h−1. The LHCE reduces the solubility of lithium polysulfides, allowing the Li/S cell to achieve super performance in a lean electrolyte. This conception of using inert diluents in a highly concentrated electrolyte can accelerate commercialization of Li–S battery technology. [ABSTRACT FROM AUTHOR]

Highly Li‐ion conductive Li4(BH4)3I@SBA‐15 is synthesized by confining the LiI doped LiBH4 into mesoporous silica SBA‐15. Uniform nanoconfinement of P63mc phase Li4(BH4)3I in SBA‐15 mesopores leads to a significantly enhanced conductivity of 2.5 × 10−4 S cm−1 with a Li‐ion transference number of 0.97 at 35 °C. The super Li‐ion mobility in the interface layer with a thickness of 1.2 nm between Li4(BH4)3I and SBA‐15 is believed to be responsible for the fast Li‐ion conduction in Li4(BH4)3I@SBA‐15. Additionally, Li4(BH4)3I@SBA‐15 also exhibits a wide apparent electrochemical stability window (0 to 5 V vs Li/Li+) and a superior Li dendrite suppression capability (critical current density 2.6 mA cm−2 at 55 °C) due to the formation of stable interphases. More importantly, Li4(BH4)3I@SBA‐15‐based Li batteries using either high‐capacity sulfur cathode or high‐voltage oxide cathode show excellent electrochemical performances, making Li4(BH4)3I@SBA‐15 a very attractive electrolyte for next‐generation all‐solid‐state Li batteries. A super ionic conductor Li4(BH4)3I@SBA‐15 for all‐solid‐state Li batteries is reported. It shows a Li‐ion conductivity of 2.4 × 10−4 S cm−1 at 35 °C and exhibits excellent electrochemical stability and electrode compatibility in the potential window of 0 to 5 V, as it can work well in Li–Li4Ti5O12, Li–S, and Li–LiCoO2 all‐solid‐state cells at 55 °C. [ABSTRACT FROM AUTHOR]

Lithium/selenium‐sulfur batteries have recently received considerable attention due to their relatively high specific capacities and high electronic conductivity. Different from the traditional encapsulation strategy for suppressing the shuttle effect, an alternative approach to directly bypass polysulfide/polyselenide formation via rational solid‐electrolyte interphase (SEI) design is demonstrated. It is found that the robust SEI layer that in situ forms during charge/discharge via interplay between rational cathode design and optimal electrolytes could enable solid‐state (de)lithiation chemistry for selenium‐sulfur cathodes. Hence, Se‐doped S22.2Se/Ketjenblack cathodes can attain a high reversible capacity with minimal shuttle effects during long‐term and high rate cycling. Moreover, the underlying solid‐state (de)lithiation mechanism, as evidenced by in situ 7Li NMR and in operando synchrotron X‐ray probes, further extends the optimal sulfur confinement pore size to large mesopores and even macropores that have been long considered as inferior sulfur or selenium host materials, which play a crucial role in developing high volumetric energy density batteries. It is expected that the findings in this study will ignite more efforts to tailor the compositional/structure characteristics of the SEI layers and the related ionic transport across the interface by electrode structure, electrolyte solvent, and electrolyte additive screening. A solid‐electrolyte interphase resulting from rational cathode design and optimal electrolytes enables solid‐state lithiation chemistry for Li/S and Li/Se‐S batteries, which can directly bypass the formation of highly soluble polysulfides/polyselenides, and hence significantly improve shuttle effects and long‐term cycle stability. [ABSTRACT FROM AUTHOR]

An in-situ enabled lithium battery (or called a "Li-free" battery) is proposed by using Li-rich Li 2 CuO 2 additive to pre-plate Li metal onto Cu current collector. Conventional Cu foil is unsuitable for efficient Li cycling particularly due to poor adhesion of Li deposits to the Cu substrate and the dendritic deposition nature of Li metal. As a solution to this problem, a very thin Li metal layer is in-situ pre-plated onto the Cu surface and served as the primer layer for next Li cycling in the battery. Results show that the addition of Li 2 CuO 2 not only provides extra Li + ions for forming a very thin Li primer layer on the Cu current collector but also enhances rate capability of LiNi 0.80 Mn 0.10 Co 0.10 O 2 cathode, which is probably because the presence of CuO particles (one of Li 2 CuO 2 decomposition products) increases liquid electrolyte uphold in the cathode. [ABSTRACT FROM AUTHOR]

Abstract: Our previously investigated quaternized poly (methyl methacrylate-co-butyl acrylate-co-vinylbenzyl chloride) (QPMBV) AAEM (alkaline anion exchange membrane) showed exceptional fuel cell performance, yet the poor durability is still remained to solve. The focus of this research is to enhance the durability of QPMBV AAEM through monomer reselection and crosslinking, which increases T g by 20°C and decreases water uptake by 75%. The resulted AAEM can continuously work for 420 and 146hrs in fuel cell without significant performance decline at 50°C and 70°C, respectively. [Copyright &y& Elsevier]

Li metal, with the lowest thermodynamically achievable negative electrochemical potential and the highest specific capacity (3860 mAh g−1), is the ultimate anode choice for Li batteries. However, the highest reported Li plating/stripping Coulombic efficiency (CE) of 99.5% after extensive efforts is still too low for the Li metal-free (all the Li metal in cycling comes from cathode, without anode pre-lithiation) Li metal batteries. The low CE is attributed to both non-uniform Li plating/stripping on the lithiophobic Cu current collector and Li dendrite growth through lithiophilic organic–inorganic solid electrolyte interphase (SEI) formed in carbonate electrolytes. Here, we use a lithiophilic Bismuth graphite blend (Bi–Gr) substrate to replace lithiophobic Cu current collector to seed a uniform Li nucleation, and form a lithiophobic LiF-rich SEI rather than lithiophilic organic-rich SEI to suppress Li dendrite growth. Molecular dynamics simulations reveal the preferential reduction of anions in 2.0 M LiPF 6 in tetrahydrofuran/2-methyl tetrahydrofuran (2.0 M LiPF 6 –mixTHF) electrolyte to generate LiF-rich SEI on plated Li. Bi–Gr substrate and 2.0 M LiPF 6 –mixTHF electrolyte enable the Li anodes to achieve a record high CE of 99.83% at a high capacity of 1.0 mAh cm−2 and current of 0.5 mA cm−2. The Bi particles serve as dispersed nucleation centers that promote uniform Li deposition with strong adhesion to the substrate to avoid dead Li, while the lithiophobic LiF-rich SEI promotes lateral Li growth and suppresses the vertical Li dendrite growth even at a high current density of 3.0 mA cm−2 and high areal capacities of 3.0 mAh cm−2. The regulation of Li nucleation and growth enables the Li metal-free LiFePO 4 full cells to achieve 100 cycles at a practical areal capacity of >2.0 mAh cm−2. This manuscript highlights the benefits of simultaneous substrate design to improve Li nucleation and electrolyte design to promote lithiophobic SEI growth, enabling a promising and practical route Li metal-free Li metal batteries. [ABSTRACT FROM AUTHOR]

Abstract Sodium-ion pouch cells with up to 1000 cycles are presented by using a NaNi 1/3 Fe 1/3 Mn 1/3 O 2 cathode, a hard carbon anode, and a functional electrolyte. The functional electrolyte is composed of 1 M NaPF 6 dissolved in a 1:1 (v/v) mixed solvent of propylene carbonate (PC) and ethyl methyl carbonate (EMC) with 3–4 wt% of two or three additives, including fluoroethylene carbonate (FEC), prop-1-ene-1,3-sultone (PST), and 1,3,2-Dioxathiolane-2,2-dioxide (DTD). It is shown that the capacity retentions of the cells increase to 84.4% and 92.2% after 1000 cycles for electrolytes containing FEC-PST bi-additive and FEC-PST-DTD tri-additive, respectively, as compared with that containing FEC single additive. Using X-ray photoelectron spectroscopy, inductively coupled plasma optical, and transmission electron microscopy, post-mortem analyses on the surface of the cycled electrodes indicate that PST and DTD are beneficial to the anode by forming an organic compound rich solid electrolyte interphase (SEI), and to the cathode by forming a dense and thick cathode electrolyte interphase (CEI) that consequently prevents transition metal ions from dissolving into electrolyte. Highlights • Long cycle life of sodium-ion pouch cells is obtained by using optimized electrolyte. • Multiple additives electrolyte is for the Na x Ni 1/3 Fe 1/3 Mn 1/3 O 2 //hard carbon system. • The capacity retention of cells comes up to 92% after 1000 cycles. • SEI on the anode and CEI on the cathode are forming to protect electrodes. [ABSTRACT FROM AUTHOR]

Lithium-ion capacitors, as a hybrid electrochemical energy storage device, realize high specific energy and power density within one device, thus attracting extensive attention. Here, hierarchically porous Li 3 VO 4 /C nanocomposite is prepared by a solvo-thermal reaction, followed with a post-annealing process. This composite has macropores at the center and mesopores in the wall, thus effectively promoting electrolyte penetration and structure stability upon cycling simultaneously. Compared to mesoporous Li 3 VO 4 , the enhanced rate capability and specific capacity of hierarchically porous Li 3 VO 4 /C indicate the synergistic effect of mesopores and macropores. Inspired by these results, this composite is coupled with mesoporous carbon (CMK-3) for lithium-ion capacitors, generating a specific energy density of 105 Wh kg −1 at a power density of 188 W kg −1 . Even if the power density increases to 9.3 kW kg −1 , the energy density still remains 62 Wh kg −1 . All these results demonstrate the promising potential of hierarchically porous Li 3 VO 4 in lithium ion capacitors. [ABSTRACT FROM AUTHOR]

Solid-electrolyte interphase (SEI) is the key component that enables all advanced electrochemical devices, the best representative of which is Li-ion battery (LIB). It kinetically stabilizes electrolytes at potentials far beyond their thermodynamic stability limits, so that cell reactions could proceed reversibly. Its ad hoc chemistry and formation mechanism has been a topic under intensive investigation since the first commercialization of LIB 25 years ago. Traditionally SEI can only be formed in nonaqueous electrolytes. However, recent efforts successfully transplanted this concept into aqueous media, leading to significant expansion in the electrochemical stability window of aqueous electrolytes from 1.23 V to beyond 4.0 V. This not only made it possible to construct a series of high voltage/energy density aqueous LIBs with unprecedented safety, but also brought high flexibility and even "open configurations" that have been hitherto unavailable for any LIB chemistries. While this new class of aqueous electrolytes has been successfully demonstrated to support diversified battery chemistries, the chemistry and formation mechanism of the key component, an aqueous SEI, has remained virtually unknown. In this work, combining various spectroscopic, electrochemical and computational techniques, we rigorously examined this new interphase, and comprehensively characterized its chemical composition, microstructure and stability in battery environment. A dynamic picture obtained reveals how a dense and protective interphase forms on anode surface under competitive decompositions of salt anion, dissolved ambient gases and water molecule. By establishing basic laws governing the successful formation of an aqueous SEI, the in-depth understanding presented in this work will assist the efforts in tailor-designing better interphases that enable more energetic chemistries operating farther away from equilibria in aqueous media. [ABSTRACT FROM AUTHOR]

We demonstrate for the first time that by simply substituting ether-based electrolyte (1.0 M NaCF 3 SO 3 in diglyme) for the commonly used carbonate-based electrolyte, the cyclability of FeS 2 towards sodium storage can be significantly improved. A sodiation capacity over 600 mAh/g and a discharge energy density higher than 750 Wh/kg are obtained for FeS 2 at 20 mA/g. When tested at 60 mA/g, FeS 2 presents a sodiation capacity of 530 mAh/g and retains 450 mAh/g after 100 cycles, much better than the cycling performance of Na/FeS 2 tested in carbonate-based electrolyte. [ABSTRACT FROM AUTHOR]

Abstract: A patterned core–shell tin (Sn) nanorod anode is fabricated by pulse electrodeposition of Sn onto a self-assembled Tobacco Mosaic Virus (TMV) structured nickel current collector. Pulse electrodeposition onto the virus assembled 3D electrode surfaces produces homogenous Sn coatings with significant void space to accommodate the large volume change associated with Sn lithiation. The TMV enabled 3D Sn anodes shows high capacity retention of 560 mAh g−1 after 100 cycles with the average capacity fading rate of 0.4% per cycle. The high electronic conductivity of Sn, short diffusion length for Li-ions, and large interface between Sn nano-rods and electrolyte greatly enhance the rate performance of the TMV enabled Sn anodes. [Copyright &y& Elsevier]

A system of electrolytes using water as a solvent was successfully used to support a typical lithium-ion battery chemistry that operates at 3.7V–4.2 V using standard ultraviolet-cured acrylic-based polymers as hydrophobic barriers. The aqueous electrolyte is contained in a system of poly(ethylene glycol) acrylate polymers crosslinked to produce an electrolyte gel that has electrochemical properties similar to that of the liquid phase component. The electrolyte gels have elastic moduli in the kPa range, making them soft enough to tolerant flexing, cutting, and blunt force impacts while keeping the electrodes covered and safe from shorting. While batteries based on water-in-salt electrolyte provides intrinsic safety that is otherwise unavailable from typical non-aqueous electrolytes, acrylate-based aqueous gel electrolytes offer the potential of large-scale manufacturing owing to the relatively low volatility of the electrolyte components and the low complexity of the proposed manufacturing process. • UV-cured gel electrolytes were used to construct a 4 V lithium ion battery. • The main gel electrolyte was water-based, making the battery safe. • Gel electrolytes had conductivity ≥0.3 mS/cm. • Gel electrolytes exhibited favorable impedance characteristics. • Battery cells used graphite anodes and LiCoO 2 cathodes. [ABSTRACT FROM AUTHOR]

Aqueous zinc batteries could offer a high theoretical energy density at an economical cost. However, their broader applications are limited by low practical energy density and poor reversibility of the Zn anode. In this work, we demonstrate that a water-in-salt electrolyte based on zinc and lithium salts enables dendrite-free Zn plating/stripping at a high coulombic efficiency of nearly 100%. The electrolyte also enables Zn/LiFePO 4 full battery to achieve a high energy density of 107.5 Wh kg−1 and maintain 70% of energy density after 1000 cycle at a 3C rate. Unlabelled Image • Water-in-salt electrolyte could increase the Zn metal reversibility by promoting the columbic efficiency and suppressing the dendrite formation. • Full cell provides high energy density (107.5 Wh kg−1), volume energy density (157.8 Wh L−1) and excellent cycle performance. [ABSTRACT FROM AUTHOR]

• LLZNO nanoparticles coated LiCoO 2 cathodes are synthesized by a sol-gel method. • 3D ionic/electronic conducting networks inside the cathodes are constructed. • A reactive intermediate layer of PP13-TFSI is introduced in cathode/garnet interface. • A solid electrolyte interphase composed of LiF, Li 3 N, Li 2 S and Li 2 O is in situ formed. The garnet solid electrolyte battery confronts crucial challenges of electronic/ionic conduction inside the cathode and interfacial contact between the cathode and the electrolyte. In this report, a super ion/electron conductive LiCoO 2 (LCO) material is fabricated by partially coating nano Li 6.375 La 3 Zr 1.375 Nb 0.625 O 12 (LLZNO) electrolyte on LCO and then filling Super P carbons into the uncoated space. This configuration offers continuous ionically and electronically conducting networks inside the LCO cathode. In addition, an intermediate layer of N-Methyl-N-propylpiperidinium bis(trifluoromethanesulfonyl)imide (PP13-TFSI) is introduced in between the composite cathode and the garnet electrolyte to form a solid-state ionically conducting interphase during charge/discharge cycles. Through the above interfacial engineering, the solid garnet batteries based on LiCoO 2 run as long as 400 cycles with the capacity retention of 80.2% at 0.2 C and 60 °C. [ABSTRACT FROM AUTHOR]

Highly concentrated aqueous solutions of LiN(SO2CF3)2 (5-20 M at 25 °C) are used as an electrolyte in a CR2032-type coin cell containing either LiMn2O4 or LiNi0.8Co0.15Al0.05O2 as the cathode and Cu-leached Mo6S8 Chevrel phase as the anode separated by glass fiber fabrics. [ABSTRACT FROM AUTHOR]