The Weakened Super-Exchange Interaction Realizes the Direct Regeneration of Spent Lithium-lon Battery Cathodes.

Abstract

The direct regeneration of cathodes is an effective technique to address resource waste and environmental pollution caused by spent lithium-ion batteries (LIBs). However, Li+ migration within the rock-salt phase of degraded LiNi0.5Co0.2Mn0.3O2 cathodes follows an energetically unfavorable 2-transition metal (2-TM) transport pathway (tetrahedral sites between face-sharing octahedra), creating a kinetic barrier that fundamentally limits direct regeneration. A Na-based molten salt pretreatment is applied to introduce Na atoms into the unoccupied tetrahedral sites of the rock-salt phase, which alters the electronic state distribution of bridged oxygen anions and reduces super-exchange interactions between TM atoms in adjacent layers, thereby triggering a phase transformation from rock-salt to targeted layered structure. Consequently, the Li+ migration pathway shifts from a high-energy 2-TM route to a more favorable low-barrier 1-TM route, enabling efficient lithiation and complete restoration of the cathode. The regenerated materials exhibit high structural uniformity and excellent electrochemical performance, achieving 78% capacity retention after 500 cycles. This study provides an insightful perspective on direct LIB recycling by regulating super-exchange interactions within the degraded cathode structures.