Nondisassembly Repair of Degraded LiFePO₄ Cells via Lithium Restoration from the Solid Electrolyte Interphase

The disposal of degraded batteries will be a severe challenge with the expanding market demand for lithium iron phosphate (LiFePO₄ or LFP) batteries. However, due to a lack of economic and technical viability, conventional metal extraction and material regeneration are hindered from practical application. Herein, we propose a nondisassembly repair strategy for degraded cells through a lithium restoration method based on deep discharge, which can elevate the anodic potential to result in the selective oxidative decomposition and thinning of the solid electrolyte interphase (SEI) on the graphite anode. The decomposed SEI acts as a lithium source to compensate for the Li loss and eliminate Li-Fe antisite defects for degraded LFP. Through this design, the repaired pouch cells show improved kinetic characteristics, significant capacity restoration, and an extended lifespan. This proposed repair scheme relying on SEI rejuvenation is of great significance for extending the service life and promoting the secondary use of degraded cells.