Er-doped spinel LiNi_0.5Mn_1.5O₄ as cathode for enhanced electrochemical properties in lithium-ion batteries

LiNi_0.5Mn_1.5O₄ (LNMO) material is a new generation of high-energy density lithium-ion battery (LIB) cathode material, which has attracted the attention of researchers at home and abroad. Due to the inherent side effects of LNMO materials with the electrolyte at high voltage, Mn dissolution is caused, which hinders its application. The pristine and LiNi_0.5−x/2Mn_1.5−x/2Er_xO₄ (x = 0.01, 0.03 and 0.05) were prepared by the microwave-assisted sol–gel method as cathode materials for LIBs. XRD diffraction analysis showed that the lattice parameters of LNMO samples increased after Er doping, which broadened the lithium-ion diffusion channel, and FT-IR showed that LiNi_0.5−x/2Mn_1.5−x/2Er_xO₄ (x = 0.01) (LNMO-Er0.01) had the largest disorder degree. Based on electrochemical analysis, LNMO materials doped with an adequate amount of Er was found to have superior cycle stability, high temperature, and rate performances. After 200 charge–discharge cycles, the discharge-specific capacity of LNMO-Er0.01 sample is 118.8 mAh g⁻¹, and the capacity retention rate is 93.8%. In this case, it can provide a capacity of 109.8 mAh g⁻¹ at a high current of 20 C. Furthermore, after 100 cycles at 1 C and 55 ℃, the discharge capacity of the LNMO-Er0.01 sample reached 114.0 mAh g⁻¹ with a capacity retention rate of 92.8%. In summary, the structural stability and electrochemical performance of the LNMO cathode material doped with Er³⁺ have been significantly improved.