Regulating impurity Al toward high level dopant–induced structural stabilization in upgraded regeneration of LiNi0.6Co0.2Mn0.2O2 cathodes

High level endogenous Al impurities in S–NCM622 are directly doped into NCM. • The regeneration process does not require additional agents. • The molten–salt strategy enabled rapid Li replenishment and Al incorporation. • Al doping stabilizes lattice oxygen and reinforces the layered structure. • The R–NCM622–Al sample exhibits outstanding electrochemical performance. Direct regeneration of severely damaged LiNi 1-x-y Co x Mn y O 2 (NCM) cathodes are commonly limited by the intrinsic instability and high chemical consumption. Meanwhile endogenous Al remaining during the regeneration process can be directly utilized as effective dopants for NCM regeneration. Yet, current endogenous Al doping strategies commonly lack efficient control over the Al doping pathway and exhibit unsatisfactory charge–discharge performance of regenerated NCM. Herein, we propose an one step thermal diffusion driving endogenous Al doping strategy for the upgraded regeneration of severely degraded LiNi 0.6 Co 0.2 Mn 0.2 O 2 (NCM622). The regenerated Al–doped NCM622 exhibits enhanced structural stability, thus showing excellent cycling stability. Specifically, it delivers a high initial discharge capacity of 183.9 mAh g −1 , along with an ultralow capacity fading rate of 0.0577% per cycle over 300 cycles. Such excellent performance is attributed to as high as 2 wt% Al doping, which significantly suppresses lattice oxygen diffusion and enhances the structural robustness. This work provides a practical and scalable strategy for the advanced regeneration of severely degraded NCM by utilizing endogenous Al impurities, offering a new perspective for overcoming the challenges of regenerated NCM cathodes. An upgraded regeneration strategy utilizing endogenous Al doping is developed for S–NCM622, in which thermally diffused into the lattice assisted by a eutectic molten salt, enabling concurrent lithium replenishment, Al doping and structural restoration to achieve high performance NCM622. Download: Download high-res image (472KB) Download: Download full-size image