Polyanion-Type Cathode Material KVPO₄F for Potassium-Ion Batteries: A Review

Abstract

As a promising energy storage technology, potassium ion batteries (PIBs) have attracted significant research interest due to their cost-effectiveness and high operating voltage. Among various cathode materials for PIBs, polyanion-type compounds have been widely studied owing to their structural stability and favorable ionic conductivity. In particular, potassium vanadium phosphate fluoride (KVPO4F, KVPF) exhibits a robust three-dimensional framework structure and delivers a high discharge voltage. However, its practical application is hindered by intrinsic limitations such as low electronic conductivity, structural defects, and the tendency of high operating voltages to induce oxidative decomposition of the electrolyte, which collectively impair rate performance and cycling stability. This review provides a systematic overview of the development and classification of polyanion-type cathode materials for PIBs, with a focus on the structural features and inherent challenges of KVPF. It further discusses the influence of the crystal structure of KVPF on potassium storage mechanisms and ion diffusion pathways. To address these performance limitations, this paper comprehensively summarizes the improvement strategies and related progress in recent research. Finally, based on current research progress, this review offers critical insights and future perspectives for the development of KVPF cathode materials.