Effects of Cr³⁺ Doping on Spinel LiMn₂O₄ Morphology and Electrochemical Performance

LiMn₂O₄, a significant cathode material for lithium-ion batteries, has garnered considerable attention due to its low cost and environmental friendliness. However, its widespread application is constrained by its rapid capacity degradation and short cycle life at elevated temperatures. To enhance the electrochemical performance of LiMn₂O₄, we employed a liquid-phase co-precipitation and calcination method to incorporate Cr³⁺ into the LiMn₂O₄ cathode material, successfully synthesizing a series of LiCr_xMn_2-xO₄ (x = 0~0.06). The prepared Cr-doped samples exhibited an excellent spinel structure and a unique truncated octahedral morphology. Additionally, the substitution of Mn³⁺ in LiMn₂O₄ by Cr³⁺, coupled with the significantly higher Cr-O bond energy compared to Mn-O bond energy, enhanced the stability of the crystal structure and inhibited the Jahn-Teller effect. Experimental results demonstrated that the optimized LiCr_0.04Mn_1.96O₄ displayed superior electrochemical performance, with a capacity retention rate of 93.24% after 500 cycles under a 0.5C current density; even at 50 °C, the capacity retention rate remained at 86.46% after 350 cycles under a 0.5C current density. The polyhedral morphology formed by Cr doping in LiMn₂O₄ offers an effective approach to achieving high-performance LiMn₂O₄ cathode materials.