Improved Cycle Life and Li-Ion Transport Parameters at Low Temperature in Boron and Tin Co-Doped Ni-Rich NMC Cathodes

Abstract

Ni rich layered oxides (LiNixMnyCo1-x-yO2 (x≥0.6)) are promising cathodes for high energy lithium‐ion batteries but suffer from rapid performance decay caused by cation disorder, structural degradation, and interfacial instability, particularly under non‐ambient operating conditions. Here, low level boron doping and synergistic tin–boron (2.5%) in LiNi0.9Mn0.05Co0.05O2 (NMC955) exhibit enhanced the structural resilience and structural robustness and lithium‐ion transport across −5, 25, and 45 °C. Structural and spectroscopic analyses confirm successful dopant incorporation into the layered α-NaFeO₂ structure, increasing lattice parameters and improving ordering while maintaining particle morphology. Sn–B co-doping improves rate performance and temperature resilience, delivering 150 mA h g⁻¹ at 500 mA g⁻¹ at 25 °C and achieving a 25% higher capacity than the pristine material at −5 °C under the same current density. Reduced charge‐transfer resistance (8.79 vs. 10.34 Ω), increased exchange current densities (up to 3.6 A m−2 at 45 °C), and higher lithium diffusion coefficients demonstrate accelerated interfacial and bulk transport, particularly under sub‐ambient conditions. Long‐term cycling shows improved durability, with capacity retention increasing from 78% to 88.7%. Post‐mortem XPS and XAS confirm suppressed cathode–electrolyte interphase degradation, reduced transition‐metal fluorination, and stabilised transition‐metal oxidation states after 200 cycles. These results identify cooperative Sn–B stabilisation as an effective and scalable strategy to overcome kinetic and structural limitations in Ni‐rich cathodes.