Coral-Like Porous Silicon/Graphite Composites for Lithium-Ion Batteries

Nanosilicon/graphite composites have high specific capacity in lithium-ion batteries (LIBs). However, there exist low initial Coulombic efficiency (ICE) and low tap density problems caused by the high specific surface area (SSA) of nanosilicon. Therefore, the porous structural design of silicon has become another choice. This work reports the facile preparation of micrometer-sized porous silicon by a single-roller rapid solidification technique followed by acid etching. Coral-like porous silicon (CPSi-1) with appropriate skeleton size, SSA, and porosity has been synthesized. CPSi-1 exhibits an initial discharge/charge specific capacity of 3389.4/2904.7 mAh g(-1), and the reversible specific capacity of 705 mAh g(-1) is retained after 100 cycles at a current density of 1 A g(-1). The CPSi-1@graphite/carbon composites (CPSi@G/C-1), prepared by a simple liquid-phase solidification method with obtained CPSi-1, graphite (G), and asphalt, exhibit an initial reversible specific capacity of 709.3 mAh g(-1) and a capacity retention of 86.7% after 100 cycles at 0.2 A g(-1). The CPSi@G/C-1||Li(Ni0.6Co0.2Mn0.2)O-2 (NCM622) coin-type full-cell shows a reversible specific capacity of 101.1 mAh g(-1) after 100 cycles at 0.5 C with an average CE of 99.2%. This work provides a facile and scalable industrial production technology for micrometer-sized porous silicon and porous silicon/graphite composites.