Long cycle life and high rate aqueous zinc-ion batteries enabled by polypyrrole bridging ammonium vanadium bronze nanosheet cathodes

Aqueous zinc-ion batteries are considered promising large grid energy storage systems because of their low cost and high safety. However, the limited cycle life associated capacity fading in cathode materials , especially at high charge-discharge rates, hampers the practical applications of aqueous zinc-ion batteries. Here we report that ammonium vanadium bronze nanosheets bridged by polypyrrole (NVO@PPy) as cathodes significantly enhance the cycle life and rate performances of aqueous zinc-ion batteries. At a high charge-discharge rate of 28 C (10 A g −1 ), the discharge capacity gradually increases with the number of cycles and reaches the maximum value of 195 mAh g −1 over 290 cycles, and the reversible capacity maintains 58% (108.8 mAh g −1 ) even after 2000 cycles. The fast charging-discharging and stable cycling performances are attributed to the high electronic/ionic conductivity of NVO@PPy and the stabilizing effect of PPy on interlayer ammonium. The zinc ion storage mechanism of the NVO@PPy is jointly contributed by intercalation/deintercalation and pseudocapacitance behaviour, the latter not only provides extra capacity but also facilitates fast charge-discharge capability.