LiPF6 and lithium difluoro(oxalato)borate/ethylene carbonate + dimethyl carbonate + ethyl(methyl)carbonate electrolyte for Li4Ti5O12 anode

Lithium difluoro(oxalato)borate (LiDFOB) has been investigated as lithium salt for non-aqueous electrolytes for Li4Ti5O12 anode in lithium-ion batteries. The electrolytes based on LiDFOB and carbonates are systematically investigated for LiFePO4/Li4Ti5O12 cells, by scanning electron microscopy (SEM) analysis, inductively coupled plasma (ICP) analysis and various electrochemical tests, such as cyclic voltammetry (CV), linear sweep voltammetry (LSV), electrochemical impedance spectroscopy (EIS), and charge-discharge test. The results show that at 25 °C and 60 °C, the stability and Al collector corrosion-protection ability of LiDFOB-based electrolyte are superior to LiPF6-based electrolyte; The Li4Ti5O12/Li half-cells used LiDFOB or LiPF6 as electrolyte salt have simple redox peaks, and their first charge-discharge curves have stable plateau. The differential of rate capability between LiDFOB battery and LiPF6 battery with LiFePO4/Li4Ti5O12 electrodes are not significant at 25 °C. LiDFOB battery exhibits better cycle performance than LiPF6 battery, which is particularly remarkable at 60 °C. The stability of the Li4Ti5O12 material in LiDFOB-based electrolyte is much better than that in LiPF6-based electrolyte at 60 °C.

► Suitability between LiDFOB and Li4Ti5O12 is presented.
► LiDFOB-based electrolyte shows highly interface stability to Li4Ti5O12.
► LiDFOB-based cells exhibit fairly well capacity retention after cycle at 60 °C.
► Internal resistance of LiDFOB cells increases slowly when it works at 60 °C.