Approaching the capacity limit of lithium cobalt oxide in lithium ion batteries via lanthanum and aluminium doping

Lithium cobalt oxides (LiCoO₂) possess a high theoretical specific capacity of 274 mAh g^–1. However, cycling LiCoO₂-based batteries to voltages greater than 4.35 V versus Li/Li⁺ causes significant structural instability and severe capacity fade. Consequently, commercial LiCoO₂ exhibits a maximum capacity of only ~165 mAh g^–1. Here, we develop a doping technique to tackle this long-standing issue of instability and thus increase the capacity of LiCoO₂. La and Al are concurrently doped into Co-containing precursors, followed by high-temperature calcination with lithium carbonate. The dopants are found to reside in the crystal lattice of LiCoO₂, where La works as a pillar to increase the c axis distance and Al as a positively charged centre, facilitating Li⁺ diffusion, stabilizing the structure and suppressing the phase transition during cycling, even at a high cut-off voltage of 4.5 V. This doped LiCoO₂ displays an exceptionally high capacity of 190 mAh g^–1, cyclability with 96% capacity retention over 50 cycles and significantly enhanced rate capability.