High-energy, Long-cycle-life Secondary Battery with Electrochemically Pre-doped Silicon Anode

Electrochemical pre-doping of a silicon electrode was investigated to create a new class of rechargeable battery with higher energy density. The electrochemical reaction during pre-doping formed a high-quality solid electrolyte interface (SEI) on the surface of silicon particles, which improved the charge and discharge cycle life with a small irreversible capacity. The surface composition of the pre-doped silicon particles was characterized using transmission electron microscopy (TEM), solid state magic-angle-spinning (MAS) nuclear magnetic resonance (NMR) and X-ray diffraction analysis (XRD). Pressurization promoted SEI growth and lithium binding with silicon to form Li₁₅Si₄ accompanied by the reductive reaction product of Li₂CO₃ originated from electrolyte. The Li₁₅Si₄ was highly stable when the silicon anode was used in a full cell, thus resulting in a silicon anode with a long cycle life.