Mn-containing heteropolyvanadate nanoparticles as a high-performance cathode material for aqueous zinc-ion batteries

As the key material in aqueous zinc-ion batteries (ZIBs), the cathode material can mitigate the large coulombic interaction force generated after Zn2+ (de)intercalation and provide fast reaction kinetics, so exploring the suitable cathode material is the first key issue for ZIBs to face the market. Currently, many reports have been published about polyoxometalates (POMs) with multi-electron transfer capability because their polyanionic three-dimensional skeleton acts as an electron/ion sponge, which is structurally stable during redox processes and facilitates the fast migration of Zn2+. However, nanosized heteropolyvanadates (hetero-POVs) have not yet been reported for use as cathodes in ZIBs. Herein, we first propose the dehydrated nanosized hetero-POVs K7MnV13O38 (KMVO NPs-200) as a host material to store Zn2+, which provides a discharge specific capacity of about 150 mAh g-1 at 0.1 A g-1 and satisfactory long-term life retaining over 91.2 % capacity at 1.0 A g-1 after 1000 cycles. The fast kinetics of KMVO NPs-200 were verified by pseudocapacitive analysis, galvanostatic intermittent titration technique and electrochemical impedance spectroscopy. Furthermore, the ex-situ measurements revealed that the heteropolyanion [MnV13O38]7- is a stable skeleton and the V centers in KMVO NPs200 are the main active sites. This work enriches the hetero-POVs cathode chemistry of ZIBs.