Upcycling Spent Ni‐Rich Cathodes via Interfacial Interlocking and Bonding for Prolonged Cycling

Abstract Captured by considerable economic and environmental value, direct regeneration of spent Ni‐rich NCM (SNCM) has received plenty of attention. However, similar to commercial NCM, the as‐regenerated sample also suffers from surface instability. Although the coating manner is beneficial for solving the issues above, NCM‐based composites are still limited by serious interfacial instability. Herein, for upcycling SNCM, a Li ₄ SiO ₄ coating layer is in situ built, along with the successful establishment of interfacial physical interlocking and chemical TM─O─Si bonds. Supported by detailed theoretical calculation and simulation, the introduced coating layer induced the lowering of Li‐ion diffusion energy barrier from 0.34 to 0.21 eV, whilst weakening structural strains. Moreover, the bulk structure is successfully recovered, where the content of Li/Ni mixing is obviously lowered, accompanied by enhanced structural ordering. Importantly, the as‐optimized sample exhibited low and uniform internal strains, displaying high mechanical strengths with an average Young's modulus (927.0 MPa). After 100 loops, its capacity retention can reach up to ≈91% at 1C. Assisted by kinetic analysis and ex situ investigation, the rapid charge transfer and minor side reactions are revealed. Given this, this work is expected to provide effective strategies for in situ interfacial enhancements, for upcycling SNCM toward prolonged cycling stability.