K ⁺ Vacancies and Fluorine Substitution Synergistically Regulate KTiOPO ₄ Anode for All‐Climate and Long‐Life Potassium‐Ion Batteries

Abstract

Abstract Although Ti‐based polyanion anode materials with robust structures exhibit advantages such as high reversibility and high Coulombic efficiency for alkali metal‐ion storage; however, their practical application is restricted by drawbacks including limited storage sites, low capacity, and intrinsically poor electronic conductivity. Herein, we propose a strategy of fluorine substitution combined with carbon coating of KTiOPO 4 (KTPF/C), along with the introduction of K + vacancies to activate additional potassium storage sites. The resulting KTPF/C material demonstrates a high capacity of 204.7 mAh g −1 , corresponding to the reversible storage of 1.27 K + ions. The synergistic effect of K + vacancies and fluorine substitution not only lowers the operating voltage but also results in a more disordered structure, thereby reducing the volume change during potassiation/depotassiation to 7.3%. This enables an ultralong cycle life exceeding 20,000 cycles with an extremely low capacity fade rate of 0.011‰ per cycle. Moreover, the cooperation of K + vacancies and carbon coating facilitates the transport of K + and electrons, allowing the material to maintain excellent rate performance of 125.1 mAh g −1 at 5 A g −1 . Practical full‐cell testing further confirms the material's outstanding cycling stability, high power density, and all‐climate applicability over a wide temperature range from −40 to 60 °C.