K₂Ti₂O₅@C Microspheres with Enhanced K⁺ Intercalation Pseudocapacitance Ensuring Fast Potassium Storage and Long‐Term Cycling Stability

Abstract

Abstract Benefiting from the natural abundance and low standard redox potential of potassium, potassium‐ion batteries (PIBs) are regarded as one of the most promising alternatives to lithium‐ion batteries for low‐cost energy storage. However, most PIB electrode materials suffer from sluggish thermodynamic kinetics and dramatic volume expansion during K + (de)intercalation. Herein, it is reported on carbon‐coated K 2 Ti 2 O 5 microspheres (S‐KTO@C) synthesized through a facile spray drying method. Taking advantage of both the porous microstructure and carbon coating, S‐KTO@C shows excellent rate capability and cycling stability as an anode material for PIBs. Furthermore, the intimate integration of carbon coating through chemical vapor deposition technology significantly enhances the K + intercalation pseudocapacitive behavior. As a proof of concept, a potassium‐ion hybrid capacitor is constructed with the S‐KTO@C (battery‐type anode material) and the activated carbon (capacitor‐type cathode material). The assembled device shows a high energy density, high power density, and excellent capacity retention. This work can pave the way for the development of high‐performance potassium‐based energy storage devices.