Phosphorus/sulfur co-doped hard carbon with a well-designed porous bowl-like structure and enhanced initial coulombic efficiency for high-performance sodium storage

Abstract

Hard carbon with high specific capacity and cost-effective characteristics has emerged as a critical material in the study of sodium-ion batteries (SIBs) anodes. However, their unsatisfactory initial coulombic efficiency (ICE) and ineluctable structural deformation during long-cycling work seriously hinder their application in practice. Here, phosphorus/sulfur co-doped hard carbon with a porous bowl-like structure (denoted as P/S-HCB) is developed to achieve high performance. The experimental data show that the doping of S increased the interlayer spacing of graphite in the surface/subsurface region, the doping of P promoted the formation of C-S-P and P-O bonds, which can contribute to abundant structural defects and redox reaction sites that not only improves structural stability but also contributes to the capacitive process under high rate. The as-fabricated P/S-HCB electrode demonstrates outstanding Na-ion storage performance regarding high ICE of 88.71%, the high-reversibility capacity of about 450 mA h g−1 after 140 cycles at 0.2 A g−1, extraordinary rate capability of 216.3 mA h g−1 at 10 A g−1, and long-term cycling stability of 276 mA h g−1 after 3000 cycles at 10 A g−1. These results show a novel approach to developing advanced hard carbon materials for sodium storage.