Hollow sphere structured Co3V2O8 as a half-conversion anode material with ultra-high pseudocapacitance effect for potassium ion batteries

New electrode materials with high capacity and cycling stability are desirable for potassium ion batteries. Herein, we synthesize a hollow sphere structured Co3V2O8 (HS-Co3V2O8) and use it as a new anode material with a reversible capacity of 409 mA h g(-1) and great rate performance. After 100 cycles, the electrode still retains a high reversible capacity of 252 mA h g(-1) at 100 mA g(-1) with a capacity retention of 82%. It can also deliver a capacity of 267.2 mA h g(-1) at 400 mA g(-1). The hollow porous structure alleviates the volume change in the potassiation and depotassiation processes and hence enhances the cycling stability. The mechanism of potassium ion storage in this HS-Co3V2O8 electrode is determined as a half-conversion reaction combined with pseudocapacitive adsorption by means of ex situ XRD, HRTEM and ex situ XPS analyses. The half-conversion reaction mechanism also brings merits for this material to have superior electrochemical properties.

Automated summary

In this study, a hollow sphere structured Co3V2O8 was synthesized and used as a new anode material for potassium ion batteries, demonstrating high reversible capacity, great rate performance, and good cycling stability. The hollow porous structure helps alleviate volume change during the charging and discharging processes, while a half-conversion reaction mechanism combined with pseudocapacitive adsorption contributes to the superior electrochemical properties of the material.