Low-Strain KVPO4F@C as Hyperstable Anode for Potassium-Ion Batteries

Abstract

Potassium-ion batteries with carbon-based materials and alloy materials as anodes possess pronounced potassium storage and cycling abilities, yet they suffer from harsh synthetic processes, low initial Coulombic efficiency, and limited structure stability. Herein, we first put forward potassium vanadium fluorophosphate (KVPO4F) as a highly stable anode material for potassium-ion batteries (PIBs). KVPO4F@C composite is successfully synthesized through hydrothermal method followed by a low-temperature roasting process. An amorphous carbon film is homogeneously wrapped on the surface of the KVPO4F particles to improve electronic conductivity. As the anode for PIBs, the KVPO4F@C presents a super-high discharge capacity of 242.32 mAh g−1 and a superior cycle stability over 120 cycles at 100 mA·g−1 with 93.1% capacity retention. Additionally, it maintains 92.9% of its initial capacity of 100 mA·g−1 at 1000 mA·g−1 after cycling 2100 times, which indicates an excellent long cycling performance. The in situ X-ray Diffraction and ex situ Transmission Electron Microscopy tests prove the minimal volume variation and stable structure of KVPO4F@C. The designed KVPO4F@C provides facilitative electronic conductivity and stable structure, successfully innovating an ultra-stable and high-performance anode material for potassium-ion batteries and other energy storage application fields.