Upcycling Spent LiCoO₂ with O2-O3 Intergrowth for Enhanced High-Voltage Stability and Cycling Performance

Direct regeneration is regarded as a next-generation recycling strategy for spent lithium-ion batteries (LIBs) owing to high element recovery and low energy consumption. However, limited by pristine design from 5-8 years ago, the simple recovery for spent LiCoO₂ (LCO) hardly induced the suitable electrochemical abilities for modern energy-storage systems. Moreover, commercial LCO with conventional O3 phase inherently suffers from poor high‑voltage stability. Herein, using the fading traits of spent LCO as upcycling springboards, they are successfully regenerated toward fresh LCO with O2-O3 intergrown architecture through lattice reconstruction and ion‑exchange‑induced phase transformation. The O2‑phase content is precisely controlled by tailoring Li‑deficiency level of SLCO. Assisted by intertwined lattice dislocations, O2 and O3 phases are coherently interlocked, effectively alleviating lattice expansion and oxygen release. Meanwhile, the lowered energy band (1.359 eV) and diffusion energy barrier (0.375 eV) play important roles for energy-storage abilities. The optimized material delivers a capacity of 223.3 mAh g^-1 at 0.1 C and retains 90.6% after 100 cycles at 1.0 C, outperforming commercial LCO. With a modified electrolyte, a capacity retention of 73.6% is achieved after 500 cycles at 5C. This work highlights the advantages of O2-O3 intergrown LCO and provides a promising upcycling route toward high‑performance cathodes.