Essence of electrochemical prelithiation of the silicon anode: from the interface to the bulk phase

Abstract

When Si anode is implemented in lithium-ion cells, prelithiation is a prerequisite for improving the Si anode's electrochemical performance. In this situation, there is a great need to deeply understand the mechanisms related to prelithiation. Herein, the essence of electrochemical prelithiation of Si anode is revealed through combined studies of full cells against a NCM523 cathode. After 100 cycles against the NCM523 cathode, SEI formation makes up for 924.2 mA h g⁻¹ of the capacity loss for the Si anode without prelithiation. After prelithiation, the lithium consumption from SEI growth is significantly reduced by 61.4%. More importantly, prelithiation plays a significant role in stabilizing the bulk phase of the Si anode, which is realized by the mitigated volume change with the prestored Li and the construction of a stable mosaic nanostructure by LiF and lithium silicate doping. For the full cell after 100 electrochemical cycles, the 858.5 mA h g⁻¹ theoretical specific capacity of the trapped Li within the Si particles without prelithiation was reduced down to 414.9 mA h g⁻¹ after prelithiation. These results shed new light on the prominent roles of prelithiation on the interface and the bulk Si phase, which is of key importance for optimizing Si-based anodes.