Improvement on the storage performance of LiMn2O4 with the mixed additives of ethanolamine and heptamethyldisilazane

Abstract

The commercial LiMn2O4 are added into the LiPF6-based electrolyte without or with the mixed additives of ethanolamine and heptamethyldisilazane to be exposed in air at 60°C for 2–6h, and the effect of different electrolytes on the storage behavior of LiMn2O4 materials and LiMn2O4/Li cells at elevated temperature is investigated comparatively for the first time by FTIR, SEM, TEM, XRD and charge–discharge measurements. The results show that the electrochemical performances of LiMn2O4 exposed in the LiPF6-based electrolyte become worse gradually with the storage time increasing. However, when the mixture of ethanolamine and heptamethyldisilazane as electrolyte additives is added into the LiPF6-based electrolyte, it can stabilize the original morphology and spinel structure of LiMn2O4 greatly and improve the storage performance of the material and LiMn2O4/Li cells effectively. As the commercial LiMn2O4 is exposed in the LiPF6-based electrolyte with additives for 4h at 60°C, the initial discharge capacity of 97.7mAhg−1 at 0.1C and the capacity retention of 89.14% at 1C rate after 150 cycles are much better than that LiMn2O4 exposed in the LiPF6-based electrolyte under the same conditions. Furthermore, the LiMn2O4/Li cells using the LiPF6-based electrolyte with additives exhibit higher initial discharge capacity before storage and higher capacity retention after storage at 60°C for a week compared to the cells without additives in the LiPF6-based electrolyte.