W and Al co-doping strategy enables bandgap engineering and oxygen stability in Ni-rich layered oxide cathode materials for high-voltage lithium-ion batteries

Recently, research on high-voltage challenges of Ni-rich layered oxide (LiNi x Co y Mn z O 2 , x + y + z = 1, where x ≥ 0.6) cathodes has become a focal point for achieving high-energy-density lithium-ion batteries due to their severe structural and electrochemical degradation under high-voltage operation. This study presents a dual-doping strategy by incorporating tungsten (W 6+ ) and aluminum (Al 3+ ) to enhance the stability and performance of LiNi 0.65 Co 0.15 Mn 0.20 O 2 (NCM) cathodes. Multiscale characterization, combining in situ XRD, electron microscopy (SEM/FIB-SEM/TEM), and surface analysis (XPS/EPR), revealed that W Al co-doping effectively suppresses cation disorder, stabilizes lattice oxygen, and inhibits microcrack propagation. Moreover, density functional theory calculations further elucidate the stabilization mechanisms, indicating that W 6+ and Al 3+ synergistically reduce the bandgap, enhance electronic conductivity, and strengthen metal-oxygen bonds. As a result, the optimized W/Al co-doping cathode (1.5W-0.5Al) delivers outstanding electrochemical performance, exhibiting a high capacity of 205.95 mAh g −1 at 0.1C and remarkable rate capability (148.2 mAh g −1 at 15C). The material demonstrates exceptional cycling stability, maintaining 122.17 mAh g −1 after 500 cycles at 1C (2.5–4.5 V), while achieving over 1000 stable cycles at 15C. This work establishes an effective dual-doping approach for developing high-voltage Ni-rich cathodes, providing both fundamental insights and practical solutions for next-generation energy storage systems.