Conversion-type electrode materials hold significant promise for potassium-ion batteries (PIBs) due to their high theoretical capacities, yet their practical deployment is hindered by sluggish kinetics and irreversible structural degradation. To overcome these limitations, we propose a rationally engineered nanoreactor architecture that stabilizes defect-rich MoS ₂ via interlayer incorporation of a carbon monolayer, followed by encapsulation within a nitrogen-doped carbon shell, forming a MoSSe@NC heterostructure. This tailored structure synergistically accelerates both K ⁺ diffusion kinetics and electron transfer, enabling unprecedented rate performance (107 mAh g ⁻¹ at 10 A g ⁻¹ ) and ultralong cyclability (86.5% capacity retention after 1200 cycles at 3 A g ⁻¹ ). Mechanistic insights reveal a distinctive “adsorption-conversion” pathway, where sulfur vacancies on exposed S–Mo–S basal planes act as preferential K ⁺ adsorption sites, effectively suppressing parasitic phase transitions during intercalation. In situ X-ray diffraction and transmission electron microscopy corroborate the structural reversibility of the conversion reaction, with the carbon matrix dynamically accommodating strain while preserving electrode integrity. This work not only advances the understanding of defect-driven interfacial chemistry in conversion-type materials but also provides a versatile strategy for designing high-performance anodes in next-generation PIBs through heterostructure engineering.

With the rapid development of recycling and secondary utilization of end-of-life battery materials, it is crucial to clarify the impact of full-lifecycle degradation on the thermal safety limits of lithium-ion batteries. This study focuses on a 16 Ah NCM613|graphite pouch battery. First, it analyzes the evolution of capacity decay, thickness expansion, and internal resistance during cycling at room temperature (25 °C) and high temperature (45 °C). Furthermore, an adiabatic accelerated calorimeter (ARC) is employed to investigate the influence of different states of health (SOH) levels (95% and 85%) on the battery’s thermal runaway characteristics. The findings indicate that, macroscopically, batteries in all states follow similar voltage–temperature failure pathways, with mass loss rates confined to a narrow range of approximately 16%, emphasizing the low catastrophic potential of mid-nickel chemistry. However, the microscopic kinetic mechanisms exhibit significant anisotropy: although thickness and internal resistance display no apparent abrupt increase during the late stage of room temperature aging, the capacity exhibits a highly nonlinear plunge behavior. The severe internal lithium plating side reaction triggered by this phenomenon causes the self-heating onset temperature to drop rapidly from 130.0 °C in the fresh state to 79.7 °C. Concurrently, the activation energy of the exothermic side reaction, fitted using a simplified Arrhenius equation, exhibits a non-monotonic variation with aging progress. In the early stages of aging at 95% SOH, due to high temperatures promoting more significant growth of the interfacial film or moderate film formation at room temperature enhancing interfacial thermal stability, the activation energies for both aged batteries increase, and the energy barrier at high temperatures is slightly higher than at room temperature; however, during the deep aging stage at 85% SOH, due to the degradation of active material components and the emergence of lithium plating characteristics, the energy barrier significantly decreases, with high-temperature-aged batteries exhibiting a greater reduction, highlighting the cumulative negative impact of prolonged high-temperature exposure on thermal safety. The research provides a core scientific basis for establishing a battery safety early warning and dynamic health management system covering the entire lifecycle.