Review on Cathode Materials for Sodium‐ and Potassium‐Ion Batteries: Structural Design with Electrochemical Properties

Abstract As a promising candidates for next‐generation secondary battery system, sodium‐ion (Na‐ion) batteries and potassium‐ion (K‐ion) batteries are recently attracting considerable attention because of their cost‐effectiveness and similar reaction mechanism to that of lithium‐ion batteries. However, the major challenges for their practical application are sluggish ionic kinetic with excessive volume change of the cathode material, caused by larger ionic radius than Li + ion. The current demand for high energy density is not satisfactory with the electrochemical properties of the cathode materials for Na‐ion and K‐ion batteries studied so far, but extensive studies have been conducted to achieve large reversible capacity, high power capacity, and long life in recent years. This review provides comprehensive information on the cathode material studies reported to date for Na‐ion and K‐ion batteries, with a particular focus on the various strategies of each cathode material to achieve high electrochemical properties. In this regard, diverse electrochemical properties of cathode materials for Na‐ion and K‐ion batteries are compared with current Li‐ion battery systems, and future research directions are discussed along with related challenges and prospects.