Micro-Sized Bimodal Meso-/Microporous Si Anode from Modified Al-Si Melt for Lithium-Ion Batteries

Abstract

Although silicon anode has been widely considered as candidate anode materials for the next generation of high-energy-density lithium-ion batteries, the large volumetric change (~300%) during lithiation and delithiation process causes its cycle performance to decay rapidly. Numerous studies have shown that porous silicon can mitigate the volume expansion of silicon anodes and improve its cycle stability. Herein, we combine the melt modification and fast solidification process to synthesize a micro-sized hierarchical porous Si with bimodal mesopores and micropores structure (µSPSi). The theoretical simulation results show that µSPSi has less expansion stress during the lithiation process under the action of synergistic stress-buffering effect. Consequently, the synthesized µSPSi anode with carbon deposition (µSPSi@C) delivers a high ICE of 82.2% and 75.2% capacity retention after 500 cycles, which is much better than that of porous Si with unimodal pore structure. Meanwhile, the 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.