Tungsten doping reinforced structural stability of single-crystal nickel-rich LiNi0.9Co0.1O2 cathodes†

Single-crystal LiNi_0.9Co_0.1O₂ (NC9010) cathode materials exhibit enhanced intergranular fracture resistance and cycling performance compared to polycrystalline materials, but they are still challenged by irreversible phase transitions, side reactions, and intragranular cracking. Herein, tungsten (W)-doped single-crystal NC9010 cathode materials with enhanced structural stability are prepared via a simple tungstic acid mixing with subsequent calcination. The W doping can not only reduce the surface residual alkali of particles, but also enhance the binding force between transition metal and oxygen due to the strong W–O bond, thereby enhancing lattice oxygen stability and inhibiting the formation and expansion of intragranular cracks. Impressively, the 0.6 mol% W-doped single-crystal NC9010 exhibits minimal structural changes along with high Li⁺ diffusion. As a result, the 0.6 mol% W doped sample exhibits a high initial specific capacity of 198.3 mA h g⁻¹, remarkable capacity retention of 78.9%, and low median voltage degradation of 131 mV after 200 cycles at 100 mA g⁻¹ in the voltage window ranging from 2.7 V to 4.5 V. This work demonstrates that W doping is a promising strategy to reinforce the structural stability and cycling lifespan of Ni-rich single-crystal layered oxide cathode materials for high energy density lithium-ion batteries under high cut-off voltage.