Electrochemical scissoring of disordered silicon-carbon composites for high-performance lithium storage

Abstract

Practically adapted physical integration of silicon and carbon predominates as a viable solution to realize high energy density batteries, however, the composite structure is vulnerable to fracture. Here we report a molecular-level mixed silicon-carbon composite anode through thermal pyrolysis of silane and subsequent mechanical mill, entailed by electrochemical dissociation and reclustering of such disordered silicon-carbon bonds during the cycles. Lithium insertion induces heterolytic fission of the bonds into sub-nanometre silicon particles segregated by redox-active carbon framework validated by microscopy analysis and reactive molecular dynamics simulation. The embedded structure with a high packing density of silicon prevents detrimental electrochemical coalescence and direct contact to a liquid electrolyte to stabilize the interfaces, while three-dimensional (3D) carbon framework buffers large volume expansion of silicon to enable an extended full battery cycling.