Multi-layered yolk-shell design containing carbon bridge connection for alloying anodes in lithium-ion batteries

Designing a material structure that supports high-capacity and long cycle life in silicon (Si) anodes has been a long-standing challenge for advancing lithium-ion batteries. Yolk-shell design has been considered a most promising design for alleviating the volume expansion feature of Si. However, the significant void between the Si core and the outer shell limits electrical contact and the complete utilization of the Si core and deteriorates the battery performance upon cycling. In this study, we synthesized a bridged multi-layered yolk-shell (MYS) structure design via thermal decomposition of SiH4 and carbon oxidation in the air atmosphere. This MYS design features a void space to accommodate the volume expansion of the Si core. It includes a carbon bridge (CB) that connects the Si core and outmost shell containing SiOx /Si/SiOx which improves the electrical contact and lithiation kinetics of the Si core and addresses fundamental issues of low contact between core and shell. As a result, the CB-MYS structure exhibits a high specific capacity of 2,802.2 mAh g-1, an initial Coulombic efficiency of 90.0%, and maintains structural integrity and stable cycling performance. Hence, we believe the CB-MYS structure is a promising engineering design to enhance the performance of high-capacity alloy anodes for next-generation lithium-ion batteries.