Hard Carbon Microsphere with Built-In Electron Transport Channels as a High-Performance Anode for Sodium-Ion Batteries

Abstract

Hard carbon is one of the most promising candidate materials as the anode for sodium-ion batteries (SIBs). In this work, we developed an effective strategy to homogenize highly conductive carbon nanotubes (CNTs) into a hard carbon microsphere (e-HC) to construct electron transport channels to improve the performance of hard carbon. The material featured a wrinkled hard carbon microsphere with built-in electron transport channels. Although the optimization made no significant changes in the particle size and the graphitization state for the hard carbon, the electrochemical performance was greatly improved in comparison with the pure hard carbon material without CNTs (HC). The increase in the electric and ionic conductivity was identified. The electrochemical measurements showed that the e-HC electrode delivered a reversible capacity of 335.6 mAh g-1 at 0.05 mA g-1, which was higher than that of the HC electrode (304.1 mAh g-1 at 0.05 mA g-1). The as-synthesized e-HC material exhibited a higher rate performance and a better cycle life than the HC material. The correlated mechanism for the enhancement was proposed in this study. The e-HC material can be used as a feasible anode for SIBs.

Recent Progress in Hard Carbon Anodes for Sodium‐Ion Batteries

“…PH5 exhibits a better capacity and cyclability, which has the potential to improve the energy aspect of the full battery. Zhang et al [ 105 ] constructed electron transport orbitals by homogenizing carbon nanotubes (CNT) into hard carbon microspheres, improved the conductivity and increased the reversible capacity from 304.1 to 335.6 mAh g −1 compared to a pure hard carbon anode, while significantly improving its rate performance and cycling stability (maintained up to 93.5% after 100 cycles at 1 A g −1 ). Xie et al [ 106 ] synthesized soft and hard carbon composites from biomass and petroleum wastes, and obtained a good reversible capacity of 282 mAh g −1 with an ICE of up to 80% at a current density of 30 mA g −1 , which exhibited a higher specific capacity compared to pure hard carbon and soft carbon.…”