Multi-doping induces truncated octahedral structure formation in lithium manganate cathode material

The surface anisotropy of spinel LiMn 2 O 4 crystals exerts a profound influence on the electrochemical performance of the material. The truncated octahedral structure consists of various crystal facets such as {1   1   0}and {1   1   1}. Among them, {1   1   0} facets are conducive for the lithium-ion diffusion, although it will worsen manganese dissolution. In contrast, densely arranged {1   1   1} surfaces can reduce manganese dissolving but hinder lithium-ion diffusion. To balance ion diffusion and manganese dissolution, the ratio of {1   1   0} and {1   1   1} planes is regulated using the Mg/Al/Ti multi-doping approach. The percentage of {1   1   0} facets exposed is effectively increased by Mg/Al co-doping, and the exposure of the truncated facets improves the lithium-ion diffusion coefficient from 7.17 × 10 -12 to 1.02 × 10 -11 cm 2 s −1 , while also increasing the manganese dissolution from 1.15 % to 1.67 %. The addition of Ti reduces the proportion of truncated surfaces and mitigates manganese dissolution (1.39 %). The lithium-ion diffusion coefficient is maintained at 9.17 × 10 -12 cm 2 s −1 , and Mg/Al/Ti co-doping maintained a discharge specific capacity of 94.0 mAh/g after 500 cycles with a degradation rate of 0.062 % per cycle. Surface optimization and reconfiguration of regulated electrode materials can provide new possibilities for the development of lithium-ion batteries.