Polyvinylpyrrolidone-Intercalated Mn 0.07 VO x toward High Rate and Long-Life Aqueous Zinc-Ion Batteries.

Aqueous zinc-ion batteries (AZIBs) are expected to be an attractive alternative in advanced energy storage devices due to large abundance and dependable security. Nevertheless, the undesirable energy density and operating voltage still hinder the development of AZIBs, which is intimately associated with the fundamental properties of the cathode. In this work, polyvinylpyrrolidone (PVP) intercalated Mn 0.07 VO x (PVP-MnVO) with a large interlayer spacing of 13.5 Å (against 12.5 Å for MnVO) synthesized by a facile hydrothermal method is adopted for the cathode in AZIBs. The experimental results demonstrate that PVP-MnVO with expanded interlayer spacing provides beneficial channels for the rapid diffusion of Zn 2+ , resulting in a high discharge capacity of 402 mAh g -1 at 0.1 A g -1 , superior to that of MnVO (275 mAh g -1 at 0.1 A g -1 ). Meanwhile, the PVP molecule remains in the layer structure as a binder/pillar, which can maintain its structural integrity well during the charging/discharging process. Consequently, PVP-MnVO cathode exhibits superior rate capability and cycling stability (89% retention after 4300 cycles at 10 A g -1 ) compared to that of MnVO (≈51% retention over 500 cycles at 2 A g -1 ). This work proposes a new approach to optimize the performance of vanadium-based electrode materials in AZIBs.