Core-shell alloy catalysts with controllable amorphous-skin for lithium-sulfur batteries via recycling spent ternary Li-ion batteries

Lithium‑sulfur batteries have attracted considerable attention owing to their exceptionally high theoretical capacity and low material cost. However, the sluggish redox kinetics of polysulfides and the associated shuttle effect continue to pose significant barriers to their practical application. The integration of alloy-based catalysts into sulfur cathodes has shown promise in mitigating the polysulfide shuttle effect and enhancing redox reaction kinetics. Nevertheless, in-depth investigation into the surface structure of such catalysts remains limited. In this work, we report a core–shell heterostructure catalyst composed of low-entropy NiCoMn (NCM) alloy nanoparticles as the core and a thickness-controllable phosphated amorphous surface layer as the shell, which functions as a highly efficient electrocatalyst for lithium‑sulfur batteries. The NCM alloy nanoparticles, derived from spent ternary lithium-ion batteries, are first immobilized on a nitrogen-doped porous carbon (NC) support. Subsequent phosphating treatment induces the formation of a nanoscale-layer-thick amorphous skin, yielding the P x -NCM-NC (x represents the phosphating time) catalyst. Owing to its core–shell heterostructure, the catalyst can efficiently modulate the electronic structure, facilitate electron transfer, promote polysulfide conversion, and enhance reaction kinetics. Experimental results demonstrate that P 30 -NCM-NC, with a suitable amorphous skin thickness, exhibits outstanding electrochemical performance, delivering an initial discharge capacity of 1109 mAh g −1 at 0.3C. This study provides new insights into the upcycling and sustainable reuse of valuable metals from spent battery. Furthermore, it introduces an “amorphous skin” engineering approach for enhancing catalytic activity in lithium‑sulfur battery systems.