Enhanced mechanical property promote high stability of single-crystal Ni-rich cathode at 4.5 V

Abstract

Ultra-high nickel layered cathodes suffer accelerated degradation through a mechanically and chemically coupled cycle, highlighting the need to concurrently enhance durability and stability, especially at high voltages to prolong service life. This work demonstrates that tungsten near-surface doping can induce spinel nanodots, effectively improving the mechanical-chemical synergy of LiNi_0.9Co_0.05Mn_0.05O₂. Micro-compression testing of individual cycled crystalline particles is employed to reveal the quantized compression strength and modulus of materials. The modified materials exhibit a better strength of 360.2 MPa and an increased modulus of 13.7 GPa, and even after cycling the materials can maintain high strength and modulus levels of 175.3 MPa and 5 GPa respectively. More importantly, in-situ XRD indicates that the improvement of mechanical integrity is achieved by suppressing the lattice distortion. Cross-sectional SEM, TEM and XPS demonstrate that the enhanced mechanical integrity can effectively inhibit particle cracking and improve the mechanical and chemical stability. As a result, this cathode with an arranged structure delivered 75.4 % capacity retention at 4.5 V after 300 cycles, representing a 16.3 % improvement. This surface nanodots approach provides new insights into interface engineering to ameliorate degradation at high voltage, offering a pathway toward high-energy cathodes with enhanced cycling endurance.