Yolk-shell design for stabilized and scalable Li-ion battery silicon anodes

摘要

Silicon has been recognized as one of the most promising anode material for next generation high capacity Li-ion batteries. To replace the currently used graphite anodes, two major challenges need to be resolved. First, Si anodes undergo significant volume expansion and contraction during Li insertion/extraction. This volume change (～300% for Si) can result in pulverization of the initial particle morphology and causes the loss of electrical contact between active materials and the electrode framework. Second, due to the low electrochemical potential of Li insertion/extraction (<0.5 V vs Li~+/Li), the anode surface becomes covered by a solid-electrolyte interphase (SEI) film, which forms due to the reductive decomposition of the organic electrolyte. In traditional Si anodes, the SEI will rupture due to the volume change during cycling, causing the electrode surface to be cyclically exposed to the electrolyte. This results in continual formation of very thick SEI films, which causes the electrolyte to be continually consumed during cycling. The formation of SEI is further complicated by particle fracture, since fracture creates new active surfaces for SEI growth. The excessive growth of SEI causes low Coulombic efficiency, higher resistance to ionic transport, and low electronic conductivity. Here, we design a "yolk-shell" structure for a stabilized and