Surface reconstruction strategy enables rapid upcycling highly degraded layered cathode

The direct recycling of lithium ion battery (LIB) is a potential solution to the accumulation of used LIBs. The key to the regeneration of spent cathodes is to perform Li⁺ replenishment, and the ability to diffuse Li⁺ into the spent cathode, especially for the highly degraded state LiNi_0.5Co_0.2Mn_0.3O₂ (S-NCM), during regeneration is critical, where the spinel/rock salt phases generated during cycling block the layered channels for Li⁺ diffusion. Herein, the rock salt phase is partially transformed into a layered structure through surface structure modulation, which unclogs the diffusion channels for external Li⁺ into the cathode, thereby lowering the energy barrier for Li⁺ diffusion and effectively facilitating the repairing process. The method reduces thermal drive time (350 °C for 2 h and 600 °C for 2 h) and energy consumption compared to the conventional eutectic salt method (700–900 °C for 5–20 h). The regenerated NCM (R-NCM) exhibits a single-crystal structure and shows an impressive reversible specific capacity of 170.3 mAh g⁻¹ and excellent cycling and high-rate performance. It provides a discharge specific capacity of 136.9 mAh g⁻¹ at 5 C and a capacity retention of 82.3 % after 200 cycles. This work establishes the foundation for low-energy regeneration of highly degraded layered cathodes.