Phase-engineered cathode for super-stable potassium storage

The large radius of potassium ions inevitably destabilizes the crystal structure of the cathode material in potassium-ion batteries, leading to capacity degradation. Here, authors demonstrate that phase-engineered amorphous vanadium oxide alleviates large volume variation and improves electrochemical behaviour. The crystal phase structure of cathode material plays an important role in the cell performance. During cycling, the cathode material experiences immense stress due to phase transformation, resulting in capacity degradation. Here, we show phase-engineered VO2 as an improved potassium-ion battery cathode; specifically, the amorphous VO2 exhibits superior K storage ability, while the crystalline M phase VO2 cannot even store K+ ions stably. In contrast to other crystal phases, amorphous VO2 exhibits alleviated volume variation and improved electrochemical performance, leading to a maximum capacity of 111 mAh g(-1) delivered at 20 mA g(-1) and over 8 months of operation with good coulombic efficiency at 100 mA g(-1). The capacity retention reaches 80% after 8500 cycles at 500 mA g(-1). This work illustrates the effectiveness and superiority of phase engineering and provides meaningful insights into material optimization for rechargeable batteries.

Automated summary

The authors demonstrate that phase-engineered amorphous vanadium oxide can alleviate large volume variation and improve electrochemical behavior in potassium-ion batteries, leading to superior K storage ability and improved performance.