Excellent stability of spinel LiMn₂O₄-based cathode materials for lithium-ion batteries

Highlights: • Fast ionic conductor La-Mn-Sr-O is introduced as modification coating for LiMn₂O₄. • The interactions between La-Mn-Sr-O coating and LiMn₂O₄ are demonstrated. • The suppression of Mn dissolution and high conductivity of La-Mn-Sr-O coating. • La-Mn-Sr-O coating LiMn2O4 shows excellent electrochemical performances. - ABSTRACT: To improve the cycle performance of LiMn₂O₄ under high rates at elevated temperature, La-Sr-Mn-O (LSM) solid electrolyte layer is introduced as a coating layer to suppress manganese dissolution. The spinel LiMn₂O₄ was coated with La-Sr-Mn-O via sol-gel method. The structure and morphology were investigated by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM) and electron diffraction spectroscopy (EDS). The results show LSM thin layer closely coats on the surface of spinel LiMn₂O₄ with particle size of 400∼800 nm. The electrochemical results reveal the as-prepared LSM-coated sample exhabits an cycle stabiltiy under high rates at elevated temperature. The specific discharge capacity is 129.9 mAh g⁻¹ at 0.1 C and exhibits 90.6% capacity retention after 500 cycles at 1 C rate. When cycling at 55 °C, the composite shows 93.6% capacity retention after 130 cycles. The LSM coating suppresses the dissolution of Mn and reduces the impedances, enhancing the kinetrics of lithium-ion diffusion through the surface layer and the charge transfer reaction. This study may provide new insight into restraining the capacity fading of LiMn₂O₄ electrodes and show their promising large-scale commercialization of high-power lithium ion batteries