No abstract

During the operation of an NH 4 + -ion battery electrode of a bi-layered V 2 O 5 , the charge carrier of NH 4 + migrates through the electrode's lattice in a fashion akin to monkey-bar walking, very different from spherical metal ions. Computation studies reveal that there is a charge transfer from the VO layers to the NH 4 + ions via a robust H bonding, where such H bonding has been revealed by characterization. Interestingly, the results point to a correlation between the H bonding and some rarely seen strong pseudocapacitance.

The sluggish ion diffusion and electrolyte freezing with volumetric changes limit the low-T performance of rechargeable batteries. Herein, we report a high-rate aqueous proton battery (APB) operated at and below -78 o C via a 62 wt% (9.5 m) H 3 PO 4 electrolyte. The APB is a rocking-chair battery that operates with protons commuting between a Prussian blue cathode and a MoO 3 anode. At -78 o C, the APB full cells exhibit stable cycle life for 450 cycles, high round-trip efficiency of 85%, and appreciable power performance. The APB delivers 30% of its room-temperature capacity even at -88 o C. The proton storage mechanism is investigated by ex situ synchrotron XRD, XAS, and XPS. The APB pouch cells demonstrate nil capacity fading at -78 o C, which offers a safe and reliable candidate for high-latitude applications.

To date, tremendous efforts of the battery community are devoted to batteries that employ Li + , Na + , and K + as charge carriers and nonaqueous electrolytes. However, aqueous batteries hold great promise for stationary energy storage due to their inherent low cost and high safety. Among metal batteries that use aqueous electrolytes, zinc metal batteries are the focus of attention. In this study, iron as an anode candidate in aqueous batteries is investigated because iron is undoubtedly the most earth-abundant and cost-effective metal anode. Reversible iron plating/stripping in a FeSO 4 electrolyte is demonstrated on the anode side and reversible topotactic (de)insertion of Fe 2+ in a Prussian blue analogue cathode is showcased. Furthermore, it is revealed that LiFePO 4 can pair up with the iron metal anode in a hybrid cell, delivering stable performance as well.

Sulfur represents one of the most promising cathode materials for next-generation batteries; however, the widely observed polysulfide dissolution/shuttling phenomenon in metal-sulfur redox chemistries has severely restricted their applications. Here it is demonstrated that when pairing the sulfur electrode with the iron metal anode, the inherent insolubility of iron sulfides renders the shuttling-free nature of the Fe-S electrochemical reactions. Consequently, the sulfur electrode exhibits promising performance for Fe 2+ storage, where a high capacity of ~1050 mAh g -1 , low polarization of ~0.16 V as well as stable cycling of 150 cycles have been realized. The Fe-S redox mechanism was further revealed as an intriguing stepwise conversion of S 8 ↔ FeS 2 ↔ Fe 3 S 4 ↔ FeS, where a low volume expansion of ~32.6% and all-solid-state phase transitions facilitate the reaction reversibility. This study suggests an alternative direction to exploit sulfur electrodes in rechargeable transition metalsulfur batteries.The pressing need for renewable energy storage entails the development of cost-effective and sustainable battery technologies. [1] Along this line, batteries that employ earth-abundant elements such Recently, our group investigated a Fe-metal battery, where a Prussian blue cathode undertakes reversible Fe 2+ (de)insertion reactions. [38] In this work, we further demonstrate Fe-S battery chemistry Received: ((will be filled in by the editorial staff))Revised: ((will be filled in by the editorial staff))

A great challenge for all aqueous batteries, including Zn-metal batteries, is the parasitic hydrogen evolution reaction on the low-potential anode. Herein, we report the formula of a highly concentrated aqueous electrolyte that mitigates hydrogen evolution by transforming water molecules more inert. The electrolyte comprises primarily ZnCl 2 and LiCl as an additive, both of which are inexpensive salts. The O-H covalent bonds in water get strengthened in a chemical environment that has fewer hydrogen bonding interactions and a greater number of Zn-Cl superhalides, as suggested by integrated characterization and simulation. As a result, the average Coulombic efficiency of zincmetal anode is raised to an unprecedented >99.7% at 1 mA cm −2 . In the new electrolyte, the plating/stripping processes leave the zinc-metal anode dendrite-free, and the zinc-metal anode delivers stable plating/stripping cycles for 4000 hours with an areal capacity of 4 mAh cm −2 at 2 mA cm −2 . Furthermore, the high Coulombic efficiency of zinc-metal anode in the ZnCl 2 -LiCl mixture electrolyte is demonstrated in full cells with a limited anode. The V 2 O 5 •H 2 O||Zn full cell with an N/P mass ratio of 1.2 delivers a stable life of more than 2500 cycles, and the LiMn 2 O 4 ||Zn hybrid cell with an N/P mass ratio of 0.6 exhibits 1500 cycles in its stable life.

The elemental sulfur electrode with Cu2+ as the charge carrier gives a four‐electron sulfur electrode reaction through the sequential conversion of S↔CuS↔Cu2S. The Cu‐S redox‐ion electrode delivers a high specific capacity of 3044 mAh g−1 based on the sulfur mass or 609 mAh g−1 based on the mass of Cu2S, the completely discharged product, and displays an unprecedently high potential of sulfur/metal sulfide reduction at 0.5 V vs. SHE. The Cu‐S electrode also exhibits an extremely low extent of polarization of 0.05 V and an outstanding cycle number of 1200 cycles retaining 72 % of the initial capacity at 12.5 A g−1. The remarkable utility of this Cu‐S cathode is further demonstrated in a hybrid cell that employs an Zn metal anode and an anion‐exchange membrane as the separator, which yields an average cell discharge voltage of 1.15 V, the half‐cell specific energy of 547 Wh kg−1 based on the mass of the Cu2S/carbon composite cathode, and stable cycling over 110 cycles.

Tremendous effort has been devoted to lithium‐sulfur batteries, where flooded electrolytes have been employed ubiquitously. The use of lean electrolytes albeit indispensable for practical applications often causes low capacity and fast capacity fading of the sulfur cathode; thus, the electrolyte/sulfur active mass ratios below 5 µL/mg have been rarely reported. Herein, we demonstrate that ZnS coating transforms sulfur cathode materials electrolyte‐philic, which tremendously promotes the performance in lean electrolytes. The ZnS‐coated Li2S@graphene cathode delivers an initial discharge capacity of 944 mAh/g at an E/S ratio of 2 µL/mg at the active mass loading of 5.0 mg Li2S/cm2, corresponding to an impressive specific energy of 500 Wh/kg based on the mass of cathode, electrolyte, and the assumed minimal mass of lithium metal anode. Density functional theory calculations reveal strong binding between ZnS crystals and electrolyte solvent molecules, explaining the better wetting properties. We also demonstrate the reversible cycling of a hybrid cathode of ZnS‐coated Li2S@graphene mixed with VS2 as an additive at an E/AM (active mass) ratio of 1.1 µL/mg, equivalent to the specific energy of 432 Wh/kg on the basis of the mass of electrodes and electrolyte.