▎ 摘　　要

NOVELTY - Preparing cathode active material, comprises providing titanium carbide, tin salt, solvent, and sodium hypophosphite, mixing the titanium carbide, tin salt, and solvent to obtain a precursor solution, heating the precursor solution to obtain a titanium carbide/tin(IV) oxide precursor, mixing the titanium carbide/tin(IV) oxide precursor and sodium hypophosphite to obtain a mixture, and performing high-temperature phosphating treatment of the mixture, the tin(IV) oxide and sodium hypophosphite in the titanium carbide/tin(IV) oxide precursor to undergo an in-situ phosphating reaction to obtain the titanium carbide/tin phosphide composite as the cathode active material, where the particle size of tin phosphide in the titanium carbide/tin phosphide composite is 20-50 nm. USE - The cathode active material is useful in cathode of potassium ion battery (all claimed). ADVANTAGE - The potassium ion battery using the cathode active material has a longer cycle life and stronger cycle performance. DETAILED DESCRIPTION - INDEPENDENT CLAIMS are also included for: (1) cathode active material, i.e., is titanium carbide/sodium hypophosphite composite, where the particle size of tin phosphide in the composite is 20-50 nm; (2) cathode material, comprising the cathode active material, a binder, and a conductive agent; (3) cathode, comprising a current collector and a cathode film covering the current collector, where the material of the cathode film is the cathode material; and (4) potassium ion battery, comprising the cathode, potassium anode, and electrolyte, where both the cathode and the potassium anode are placed in the electrolyte.