Silicon Nanoparticles Encapsulated within Multifunctional Double Carbon Matrices as Anodes for High-Performance Lithium-Ion Batteries

Abstract

Significant volume expansion and limited electrical conductivity pose substantial challenges to the practical application of silicon (Si). Herein, silicon nanoparticles are incorporated into a dual-carbon matrix co-doped with nitrogen and sulfur (N/S co-doped Si/G/C) using a method that combines ball milling and carbonization. The Si nanoparticles are uniformly distributed between graphite layers and encapsulated by an amorphous carbon layer co-doped with N/S generated from the pyrolysis of pitch and thiourea. This N/S co-doped three-dimensional dual-carbon structure not only effectively mitigates the volume expansion of silicon but also significantly enhances the material's ionic and electronic conductivity. Even at a current density of 1 A g⁻¹, the capacity remains at 625.87 mAh g⁻¹ after 500 cycles, demonstrating exceptional cycling stability. When assembled into a full battery with LiFePO₄, the battery retains a capacity of 158.9 mAh g⁻¹ after 200 cycles, corresponding to a retention of 95.6%. In addition, the method is simple to operate, highly adaptable and versatile in function, and does not involve any toxic or harmful chemical substances, providing a new idea for the industrial production of silicon–carbon anode materials.