Surface spinel reconstruction to suppress detrimental phase transition for stable LiNi_0.8Co_0.1Mn_0.1O₂ cathodes

Nickel-rich layered oxides are attractive cathode for lithium-ion batteries (LIBs) because of the high energy density and low cost. The critical problem is capacity fading caused by the highly reactive metastable phases under voltages of higher than 4.15 V. Herein, we find that facile Ar/H₂ plasma treating could produce oxygen vacancies that will readily transform into homogeneous spinel layer (~ 6 nm) on the LiNi_0.8Co_0.1Mn_0.1O₂ (NCM₈₁₁) surface after a few cycles of lithiation/delithiation procedure. Owing to the structural matching between spinel and layered structure, the diffusion of Li ions could remain fast upon cycling. Besides, the spinel layer is electrochemically inert, which guarantees surface stabilization and inhibits the detrimental phase transition from H2 to H3 at high voltages. Under the protection of the homogeneous spinel layer, the NCM₈₁₁ electrode shows superior capacity retention of 91.2% after 200 cycles at the current density of 100 mA·g⁻¹. This work proposes a novel strategy of surface reconstruction to stabilize nickel-rich layered oxide materials for LIBs.