Stabilizing lattice oxygen in dual-doped LiCoO₂ for enhanced cycling stability and rate capability at 4.6 V

Elevating the charging voltage of lithium cobalt oxide (LCO) materials can effectively enhance the theoretical specific capacity and energy density of lithium-ion batteries, thereby meeting the growing energy storage demands of mobile electronic devices and electric vehicles. However, during charging and discharging at high voltages, LCO undergoes irreversible phase transitions and lattice oxygen release, leading to structural degradation and capacity fading. Additionally, the structural degradation under high-voltage and sluggish Li⁺ diffusion limit it fast-charging performance and extreme-temperature operation. Here, a novel co-doping strategy using Lanthanum (La) and Gadolinium (Gd), which significantly enhances the cycling stability at high voltages and improves high-rate capability. The highly electropositive La and Gd elements in LCO can enhance the effective charge of oxygen, thereby improving the stability of the oxygen framework and inhibiting oxygen loss. The co-doping of La and Gd ions into cobalt sites effectively suppresses detrimental phase transitions and microcrack formation, while simultaneously expanding the interlayer spacing to enhance ionic conductivity. Therefore, when subjected to cycling tests at a 2C rate under a high cut-off voltage of 4.6 V, the La/Gd co-doped LCO (LG-LCO) cathode material retained 77.12 % of its initial capacity after 300 cycles, demonstrating excellent electrochemical performance across a broad temperature range (-20 to 45 °C). This feasible rare-earth co-doping strategy offers a promising research direction for developing advanced high-voltage cathode materials.