A micro-sized bimodal meso/microporous Si anode made from a modified Al–Si melt for use in lithium-ion batteries

Abstract

Although silicon anodes have been widely considered as candidate anode materials for the next generation of high energy density lithium-ion batteries, the large volumetric change (∼300%) that occurs during the lithiation and delithiation processes causes the cycling performance to decay rapidly. Numerous studies have shown that porous silicon can mitigate the volume expansion of silicon anodes and improve the cycling stability. Herein, we combine a melt modification and fast solidification process to synthesize a micro-sized hierarchical porous Si material with a bimodal mesoporous and microporous structure (µSPSi). The theoretical simulation results show that µSPSi experiences less expansion stress during the lithiation process due to a synergistic stress-buffering effect. Consequently, the synthesized µSPSi anode with internal carbon deposits (µSPSi@C) delivers a high ICE of 82.2% and 75.2% capacity retention after 500 cycles, much better than other porous Si anodes with unimodal porous structures. Meanwhile, a LiCoO₂‖µSPSi@C full cell exhibits a capacity of 153 mAh g⁻¹ after 70 cycles, retaining 91.6% capacity. This work shows a novel design approach for the synthesis of porous Si for high energy density lithium-ion batteries.