Sawtooth- or Pyramidal-patterned Si Negative Electrode Fabricated by Micro-Electro-Mechanical Systems for Li-Ion Secondary Battery

摘要

Si has been an attractive negative electrode material for high energy density Li-ion secondary battery owing to its largest theoretical capacity of 4200 mAh/g. However, the volume change caused by a large degree of lithiation and delithiation results in the formation of severe cracks and the exfoliation of active Si from current collector, which ultimately deteriorates the battery performance. Therefore, the cycle-life of active Si material should be improved to apply it to secondary batteries. In this study, we attempted to improve the performance of Si film electrode by fabricating it with sawtooth and pyramidal patterns via the microelectromechanical systems process. In addition, the effect of Si electrode morphology on its charge/discharge behavior was investigated. The capacity changes of the electrodes during 50 cycles were measured. The remaining Si on the current collector and its surface morphology were observed afterward to correlate with the electrochemical behavior. The experimental results show that the pyramidal Si electrode exhibited better cycle retention than any other electrodes by relaxing the stress and mitigating the exfoliation. This study shows that the structural modification may benefit the cycle-life of Si film electrode.