Stabilizing bulk and interface of single-crystal LiNi0.90Co0.05Mn0.05O2 via Y3+ doping for long-life Li-ion batteries

High-nickel layered oxides are promising cathode materials for high-energy-density lithium-ion batteries but suffer from severe structural degradation and interfacial instability during cycling. Herein, we propose a Y 3+ doping strategy to stabilize the LiNi 0.90 Co 0.05 Mn 0.05 O 2 (NCM90) cathode. The Y 3+ -modified single-crystal material (Y-SC-N9) delivers a high discharge capacity (199.23 mAh/g) and significantly improved cycling stability, with a capacity retention of 86.01% after 100 cycles at a high voltage of 4.5 V, far exceeding the pristine sample (55.91% at 4.3 V). It also exhibits superior rate performance (176.29 mAh/g at 10C). Comprehensive characterizations reveal that Y 3+ doping constructs an “Y 3+ -O 2− -Ni 4+ ” electron cloud coupling system, which enhances the covalent character of transition metal-oxygen bonds, thereby suppressing the harmful H2-H3 phase transition and lattice oxygen release. Furthermore, Y 3+ -doping mitigates microcrack formation and promotes a more robust cathode-electrolyte interface. This work demonstrates that Y 3+ doping is an effective approach to enhancing the structural and interfacial stability of ultra-high‑nickel cathodes for advanced batteries.