Stimulative formation of truncated octahedral LiMn2O4 by Cr and Al co-doping for use in durable cycling Li-ion batteries

Abstract

The rational design of the unique morphology of particles has been considered as the key to improving the structural stability of spinel LiMn₂O₄ cathode materials for Li-ion batteries. Herein, a facile solid-state combustion process, combined with a Cr and Al co-doping approach, is proposed to prepare various LiCr_0.01Al_xMn_1.99−xO₄ (x ≤ 0.10) cathode materials with a good crystallinity. Cr and Al co-doping facilitates the formation of a single crystal truncated octahedral morphology. This endows the as-prepared LiCr_0.01Al_xMn_1.99−xO₄ with abundant {111} planes for Mn dissolution reduction and a few {100} and {110} planes for Li⁺ ion fast diffusion channels. Moreover, the introduction of Cr and Al elements with a stable electronic configuration further boosts the structural stability of the spinel LiMn₂O₄ owing to the relatively robust Al–O and Cr–O bonds compared with the Mn–O bond. Owing to these advantages, the optimal LiCr_0.01Al_0.05Mn_1.94O₄ delivers a good electrochemical performance with a high first discharge capacity of 118.5 mA h g⁻¹ and a capacity retention of 70.8% after 1000 cycles at 1 C. Even at relatively high current rates of 15 and 20 C, a durable and prolonged cycling performance of up to 3000 cycles can be achieved. In addition, a high-temperature capacity retention of 72.1% is also maintained after 200 cycles at 5 C under 55 °C. This work provides potential candidates for developing long-life Li-ion batteries with a simultaneously high capacity.