Mesoporous carbon/silicon composites via template-free method for lithium-ion battery anodes

Abstract

Silicon-carbon composite anodes have exhibited outstanding electrochemical performance. The exploration of efficient, cost-effective, and high-performance synthesis methods has become a critical foundation for their commercialization. However, the complex and diverse carbon skeleton makes the exploration process difficult. Herein, mesoporous carbon/silicon composites were synthesized without a template through liquid-phase solidification, and the relationship between the energy storage performance and the carbon skeleton morphology was investigated through experimental characterization and density functional theory (DFT) calculation. The results show that the morphology of three-dimensional interconnected pores is a preferred configuration, and the size and volume of pores are critical factors influencing the electrochemical performance. The DFT calculations elucidate the structural advantages of porous carbon materials by analyzing the work function, defect formation energy, and charge density difference. The zl-C/Si sample (zinc lactate) with three-dimensional interconnected pores exhibits the optimum resistance (32.6 $\Omega$) and diffusion coefficient (3.14 × 10⁻¹² cm² s⁻¹), corresponding to the highest ion and electron diffusion rate. The as-synthesized anode delivers a high initial discharge capacity of 2303 mAh g⁻¹ when the current density is set at 0.1 A g⁻¹. Even at 1 A g⁻¹, it can still maintain a capacity of 879 mAh g⁻¹ over 100 cycles, with 93% capacity retention. This study may offer novel insights into the commercialization process of silicon-carbon anodes.