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

• 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.

ABSTRACTTo 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.

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