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

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 K2Ti2O5 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. Carbon‐coated K2Ti2O5 microspheres (S‐KTO@C) with enhanced K+ intercalation pseudocapacitance are synthesized and investigated as anode materials for potassium‐ion batteries. The structure design associated with carbon coating improves the rate capability and cycling stability of S‐KTO@C electrodes. Furthermore, a constructed potassium‐ion hybrid capacitor shows a high energy density, high power density, and excellent capacity retention.