Microsized Silicon/Carbon Composite Anodes through In Situ Polymerization of Phenolic Resin onto Silicon Microparticles for High-Performance Lithium-Ion Batteries

Silicon (Si) has been gradually explored as a next-generation anode material to replace traditional graphite anodes in lithium-ion batteries (LIBs) due to its high specific capacity (3579 mAh g–1 at room temperature). In terms of cost and tap density, silicon microparticles (SiMPs) are more advantageous than silicon nanoparticles (SiNPs) in high energy density LIBs, but they are also plagued by the more serious volume effect. Here, we design a silicon/carbon (Si/C) composite anode through the in situ polymerization of phenolic resin (PF) onto SiMPs, and after pyrolysis, SiMPs are tightly coated with pyrolytic carbon layers. When applied in LIBs, the composite anodes (μSi@PF) exhibit excellent cycling performance (1283 mAh g–1 after 400 cycles at 2 A g–1) and rate performance (a reversible capacity of about 1000 mAh g–1 at 8 A g–1). The full cell with lithium iron phosphate cathodes and μSi@PF anodes can maintain 87.7% capacity retention after 100 cycles. The great electrochemical performance can be ascribed to the rational structure design of μSi@PF in which PF pyrolytic carbon as a shell around SiMPs can accommodate the volume change of SiMPs during cycling and reduce the internal impedance. This is the first attempt to construct Si/C composites by in situ polymerizing PF resin onto SiMPs, and the great performance of Si/C anode provides a reference for the practical application of SiMPs.