Potassium iodide as a low-cost cathode material for efficient potassium-ion storage

• DOI: 10.1016/j.ensm.2021.07.025
• Publication Date: 2021-07-19T22:30:23Z
• Authors: Leqing Deng; Meiying Feng; Ruiting Wang; Yusi Yang; Xiaogang Niu; Juan Zhang; Lulu Tan; Jianwen Zhang; Yifan Chen; Liang Zeng; Yujie Zhu; Lin Guo
• Keywords: Separator (oil production)

Abstract Potassium-ion batteries (KIBs) are attractive electrochemical energy storage technologies because of their low cost and high energy density. Currently, the reported cathode candidates for KIBs are all limited to the intercalation-type materials. The working principles of these materials all involve the repeated intercalation-deintercalation of bulky K-ions in the ionically-bonded rigid frameworks, which often results in sluggish reaction kinetics, irreversible structural deformation, and poor cycling stability. Here, a low-cost conversion-type material, potassium iodide (KI), is proposed as a promising cathode candidate for KIBs. It is revealed that the depotassiation-potassiation of KI proceeds via a dissolution-precipitation reaction process involving the highly soluble KI3 intermediate, leading to the shuttle effect and capacity decay. Susequently, a simple strategy combining electrolyte modulation with separator modification is adopted to effectively enhance the electrochemical performance of KI, leading to an impressive capacity retention of 95.5% after 550 cycles. The present study may shed some light on further exploration of high-performance electrode materials based on dissolution-precipitation reaction mechanism for the emerging KIBs.