Failure analysis and design principles of silicon-based lithium-ion batteries using micron-sized porous silicon/carbon composite

Significant progress has been made toward overcoming fundamental challenges in developing a silicon (Si) anode for lithium-ion batteries (LIBs). However, much less work has been reported on design and failure analysis of these batteries for practical applications. In this work, we analyzed the main factors that affect the performance of a Si anode and the energy density of pouch cells using micron-sized, nanoporous Si coated by pitch-derived carbon (p-Si/C). The volumetric energy density of the Si anode depends heavily on these factors, such as the loading of p-Si/C in the anode, the calendering density of the anode, the first-cycle coulombic efficiency, and the capacity density of the anode. The effects of other factors on the cycling performance were also revealed by postmortem analysis of cycled anodes. We found that a stable p-Si/C electrode structure is critical to avoid the disintegration of the anode structural integrity and lithium plating and enable long-term cycling. Moreover, prelithiation of Si anodes increases energy density, while the degree of prelithiation is another factor to balance with the cycle life of Si-based full cells. We propose pathways and strategies for adoption of micron-sized p-Si/C anodes in LIBs for their practical applications.