Nanoreactor-Structured Defective MoS2: Suppressing Intercalation-Induced Phase Transitions and Enhancing Reversibility for Potassium-Ion Batteries

• A nanoreactor-structured MoSSe@NC heterostructure was constructed via defect engineering and carbon intercalation, simultaneously achieving phase transition suppression and enhanced ion transport. • Selenium-induced lattice disorder and carbon layer confinement synergistically inhibit the 1T–2H phase transition and buffer structural strain during cycling. • The designed heterostructure exhibits high capacity, excellent rate performance, and long-term cycling stability, offering a generalizable strategy for high-performance potassium-ion battery anodes. • Mechanistic insights reveal a distinctive adsorption-conversion pathway, where sulfur vacancies act as preferential K+ adsorption sites, suppressing parasitic phase transitions and ensuring structural reversibility.