Boron-doped porous micro-sized silicon for high-performance lithium-ion battery anodes: beyond conductivity enhancement

Abstract

Compared to nanostructured Si, micro-sized Si anodes attract considerable research interest due to their superior volumetric energy density, diminished side reactions, and lower production costs. Nevertheless, the pronounced volume expansion and sluggish kinetics during (de)lithiation processes inevitably reduce initial Coulombic efficiency (ICE) and accelerate capacity degradation. To overcome these issues, we synthesize a B-doped porous micro-sized Si (B-pSi) hierarchical structure through in-situ B doping during the alloying of Si and introduction of porous structure during the dealloying process. B doping enhances conductivity and expands Si lattice spacing, while the hierarchical porous structure buffers volume change and maintains low specific surface area for high ICE. Benefiting from the synergistic effects of doping and porous structure, the resulting B-pSi anode achieves a high discharge specific capacity of 3279.12 mAh g⁻¹ with an ultra-high ICE of 86.6 % at 0.2 A g⁻¹, good rate capability (1099.4 mAh g⁻¹ at 4 A g⁻¹) and excellent cyclability (766.6 mAh g⁻¹ after 300 cycles at 4 A g⁻¹ with a high capacity retention of 80 %), far superior to those of pSi and pristine micro-sized Si anodes. With the B-pSi as anode additive, the LiFePO₄||B-pSi/graphite full cells demonstrate high capacity, good rate capability and achieve 90 % capacity retention after 100 cycles at 0.5 C, demonstrating practical viability in high-performance lithium-ion batteries. This study provides scientific insights for designing high-performance micro-sized Si-based anodes.