Low-cost  modification of graphite by coating with amphoteric oxides based on sol-gel method to increase its initial coulombic efficiency and high-rate performance and its mechanism of operation

Commercial LIBs use a graphite-based carbon anode (negative mass). During the initial lithiation cycles, a solid electrolyte interphase (SEI) forms on the graphite anode surface due to electrochemical instability of the electrolyte to lithiated graphite ^[1-6]. Ideally, the SEI inhibits further reduction of the electrolyte, allows Li ion conduction and is electrically insulating. However, in fact, the fragile and nonuniform SEI film will crack caused by surface defects and anisotropic rough edges and will be formed again and again during charging and discharging. This will consume the limited supply of Li ions continuously in a full battery and therefore result in capacity fading.

As the coulombic efficiency CE of anode materials for commercial Li-ion batteries needs to be increased for the long run, we developed a low-cost treatment to modify graphite by coating amphoteric oxide based on a sol-gel method to increase its first coulombic efficiency and high-rate performance by preventing extra SEI film formation. We optimized the process according to structure analysis and electrochemical test. Our aim is to find a general way to increase coulombic efficiency for anode materials.

Our research is aimed at a convenient coating way based on sol-gel method for graphite anode to increase its first CE and cycle performance and then find a general way for other anode materials. Meanwhile, to find out the effects and mechanisms of various coating treatment, we will use in situ investigation methods such as Fourier-Transform infrared spectroscopy (FTIR) and Raman spectroscopy to analyze the composition of electrode surface while cycling.

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