Stabilization of the K0.43V2O5 cathode by Ca ions substituted engineering strategy for high performance potassium ion batteries

• Addition of Ca ions to the potassium layer creates vacancies at the K site. • Strong interaction between Ca 2+ and O 2– suppresses the irreversible phase transition. • The Ca-KVO has superior discharge capacity of 96.61 mAh g −1 at 10 mA g −1 . • The Ca-KVO has favorable capacity retention of 96.4% after 2000 cycles at 1 A g −1 . Potassium ion batteries (PIBs) have emerged as a powerful energy stockage device because of their ample potassium resources and inexpensive. Layered potassium vanadate K 0.43 V 2 O 5 has superior electrochemical properties as cathode material for PIBs. However, the K 0.43 V 2 O 5 still faces problems such as poor structural stability and multiplication performance. In this study, Ca 2+ ions were introduced into K 0.43 V 2 O 5 (denoted as Ca-KVO) and vacancies were created at the K site, thereby improving its electrochemical performance. Ex-situ XRD and HRTEM indicated that the strong interaction between Ca 2+ ions and O 2– ions significantly improved the structural stability of Ca-KVO. And the presence of vacancies also increases the diffusion rate of potassium ions. Specifically, it provides a favorable reversible capacity of 96.61 mAh g −1 at 10 mA g −1 as well as holds 96.4 % of the specific capacity after 2000 cycles at 1 A g −1 . Furthermore, the Ca-KVO//Graphite full cell achieves a favorable discharge capacity of 94.46 mAh g −1 . Moreover, its energy density reaches 191.3 Wh kg −1 in 20.25 W kg −1 ，which shows that Ca-KVO can be applied well to PIBs. This study shows that calcium doping is an effective strategy, which is expected to provide new ideas for the exploration of high-performance PIBs.