Effect of ball-milling reaction between ethanol and Si on the electrochemical performance of silicon anodes for Lithium-ion batteries

The substantial volume expansion of silicon results in electrode structure collapse and rapid capacity degradation, posing a major obstacle to its large-scale commercial application. In this study, a high-performance silicon anode was developed using a cost-effective and efficient wet ball milling process, with anhydrous ethanol as the milling solvent. The reaction between ethanol and silicon during ball milling, and its impact on the silicon's structure, composition, and electrochemical performance, was systematically investigated. The results show that the ball milling reaction between ethanol and silicon in situ forms a SiO x layer and Si-OH/Si-O-CH 2 CH 3 groups on the silicon surface. Prolonged ball milling not only leads to the thickening of the SiO x layer, which hinders Li + diffusion, but also causes the transformation of Si-OH groups into Si-O-CH 2 CH 3 groups. This reduces the binding sites with polyacrylic acid (PAA), weakens the mechanical strength of the silicon anode, and results in significant volume changes and rapid capacity degradation. As a result, at 0.5 A g −1 , the Si-72h anode achieves an initial coulombic efficiency (ICE) of 90.21 %, and after 100 cycles, it maintains a high reversible specific capacity of 2072.5 mAh g −1 with a capacity retention of 75.13 %. At 1 A g −1 , after 300 cycles, it still retains a specific capacity of 1308.4 mAh g −1 with a capacity retention of 48.46 %, which is approximately 5 times the specific capacity of the Si-24h anode (254.0 mAh g −1 ) and 10 times that of the Si-120h anode (132.3 mAh g −1 ). Even at 4 A g −1 , after 1000 cycles, the anode still maintains a specific capacity of 1100.0 mAh g −1 , with a Coulombic efficiency exceeding 99.93 %. At a current density of 0.5C, the LiFePO 4 ||Si-72h full cell exhibited a capacity retention of 94.93 % after 100 cycles. This work offers valuable insights into the wet ball milling process for preparing high-performance silicon anode materials, facilitating their large-scale practical application.