Non‐aqueous zinc‐ion battery (ZIB) comprising a zinc vanadate@textured carbon (ZnV2O4@TC) composite cathode and Zn‐anode demonstrates an improved Zn(II)‐ion storage response, in terms of cyclability (230 mAh g−1 after 200 cycles, 84.9 % retention) and rate capability compared to pristine ZnV2O4 (175 mAh g−1 after 200 cycles, 45.4 % retention). TC reduces the aggregation of ZnV2O4 nanoparticles, allows abundant interaction with electrolyte, affords short ion diffusion pathways, serves as electrically conducting interconnects, and buffers the volume alterations thus imparting rapid kinetics and improved cycling stability. This performance is even better by the inclusion of a ZIF‐8 metal‐organic framework (MOF) layer at the separator, facing the cathode. ZIF‐8 due to its nanoporous structure encompassing Zn−N based polyhedral clusters, efficiently confines Zn(II) ions at cathode during discharge and allows their facile diffusion through its open channels during charge thus maximizing Zn(II) ion storage capacity and reversibility and its highly crystalline robust structure also enhances the ZIB durability. This achievement is in line with the development of cost‐effective, easily implementable non‐aqueous ZIB that avoids the issues associated with aqueous electrolyte of limited potential stability window, corrosion of current collectors over time, and cell degradation and also offers long term stability and capacity.
Vanadium based oxides are immensely suitable for zinc-ion-batteries (ZIBs) due to their layered and stable crystal structures. In this study, Mn doped V 3 O 7 •H 2 O nanobelts were synthesized and used as cathodes in ZIBs for the very first time and the doped oxide exhibited an enhanced capacity of 258 mAh g −1 compared to its undoped counterpart (208 mAh g −1 ) at the same current density of 40 mA g −1 . Mn:V 3 O 7 •H 2 O outperforms the V 3 O 7 •H 2 O due to the superior bulk electrical conductivity as well as higher nanoscale current carrying capability imparted by a high proportion of mixed valent states of Mn 3+ , Mn 2+ , V 5+ , and V 4+ and the smaller crystallite size that affords short diffusion lengths for Zn 2+ ions. The Mn:V 3 O 7 •H 2 O cathode is coupled with a Zn 2+ ion conducting polyacrylamide gel electrolyte and a Zn flakes/activated carbon (Zn Fs/C) composite anode to yield a unique separator free Mn:V 3 O 7 •H 2 O/Zn 2+ -PAM gel/Zn-Fs/C battery. The cell exhibits a capacity of ∼205 mAh g −1 (at 40 mA g −1 ) and retains 99% of its original capacity after 3500 cycles. The Zn 2+ -PAM gel shows a high ionic conductivity in the range of 5.9 to 28.2 S cm −1 , over a wide temperature span of 0 to 70 °C, and a wide electrochemical potential stability window of −0.5 to +2.3 V, thus rendering it suitable for low temperature applications as well. The gel also inhibits dendritic growth of Zn over the Zn-Fs/C anode through regulated flow of Zn 2+ ions during charging, prevents cathode dissolution, and improves cycle life via preservation of structural integrity of the Mn:V 3 O 7 •H 2 O cathode after 200 charge− discharge cycles. This is a highly scalable cell configuration and opens up opportunities to produce long lasting batteries completely free of costly separators with a semisolid free-standing electrolyte and a robust doped oxide.
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