Enhancing surface‐to‐bulk stability of layered Co‐free Ni‐rich cathodes for long‐life Li‐ion batteries

Abstract

AbstractLayered Co‐free Ni‐rich cathodes are the most cost‐effective for high‐energy‐density Li‐ion batteries (LIBs), yet the structural instability and interfacial side reactions seriously hamper their commercial applications versus the Co‐contained counterpart. Herein, a synchronous Ge‐doping and Li4GeO4‐coating of the Co‐free Ni‐rich cathodes have been realized to tackle these limitations during high‐temperature lithiation of the corresponding hydroxide precursors. The nonmagnetic Ge4+ doping effectively relieves the magnetic frustration and the lattice oxygen loss with reduced cation mixing and gas emission. The Li‐ion conductive and anti‐erosive Li4GeO4 coatings contribute to enhance the surface chemistry stability and Li‐ion migration interface kinetics. Consequently, the resulting Co‐free Ni‐rich cathodes delivers a high reversable capacity of 223.3 mAh g−1 at 0.1 C and maintains 127.5 mAh g−1 even at 10C within 2.7–4.4 V. More impressively, it displays high‐capacity retention of 90.5% in coin‐type half‐cell after 150 cycles and 80.5% in pouch‐type full‐cell after 500 cycles at 3C, demonstrating a long‐term cycle life.