Simple Construction of Multistage Stable Silicon-Graphite Hybrid Granules for Lithium-Ion Batteries

Because of its high specific capacity, the silicon-graphite composite (SGC) is regarded as a promising anode for new-generation lithium-ion batteries. However, the frequently employed two-section preparation process, including the modification of silicon seed and followed mixture with graphite, cannot ensure the uniform dispersion of silicon in the graphite matrix, resulting in a stress concentration of aggregated silicon domains and cracks in composite electrodes during cycling. Herein, inspired by powder engineering, the two independent sections are integrated to construct multistage stable silicon-graphite hybrid granules (SGHGs) through wet granulation and carbonization. This method assembles silicon nanoparticles (Si NPs) and graphite and improves compatibility between them, addressing the issue of severe stress concentration caused by uncombined residue of Si NPs. The optimal SGHG prepared with 20% pitch content exhibits a highly reversible specific capacity of 560.0 mAh g(-1) at a current density of 200 mA g(-1) and a considerable stability retention of 86.1% after 1000 cycles at 1 A g(-1). Moreover, as a practical application, the full cell delivers an outstanding capacity retention of 85.7% after 400 cycles at 2 C. The multistage stable structure constructed by simple wet granulation and carbonization provides theoretical guidance for the preparation of commercial SGC anodes.

Automated summary

Due to its high specific capacity, silicon-graphite composite is considered a promising anode for new-generation lithium-ion batteries. However, the commonly used two-section preparation process often results in non-uniform dispersion of silicon in the graphite matrix, leading to stress concentration and cracks in the composite electrodes. In this study, a multistage stable silicon-graphite hybrid granule (SGHG) was constructed through wet granulation and carbonization, addressing the issue of stress concentration caused by uncombined residue of silicon nanoparticles. The optimized SGHG exhibited a highly reversible specific capacity of 560.0 mAh g(-1) and a stability retention of 86.1% after 1000 cycles at 1 A g(-1), showing its potential as a commercial anode material.