Efficient construction of hard carbon through hydrothermal carbon coating engineering toward enhanced sodium-ion storage performance

Abstract

The strategy of coating porous carbon offers a promising pathway for constructing closedpore architectures in hard carbon (HC) anodes. However, the coating efficiency is strongly governed by the pyrolysis behavior of the coating agent. Conventional pyrolytic treatment of glucose produces substantial volatile by-products, leading to severe mass loss and necessitating glucose dosages exceeding twice the mass of PC to achieve effective coating, which limits practical applicability. In this study, a hydrothermal carbon-coating strategy is proposed to address this challenge. During hydrothermal pretreatment, glucose molecules diffuse into the surface and pore channels of PC, where they undergo in situ polymerization to form polyfuranderived carbon coatings. This transformation markedly mitigates mass loss during subsequent carbonization, enabling effective coating using glucose and PC at a 1:1 mass ratio. Moreover, the carbon formed within the pore network generates internal diffusion channels that accelerate Na + transport and facilitate electrochemical storage. The resulting HC exhibits a high reversible capacity of 323 mAh g -1 at 0.05 A g -1 , and maintains 175 mAh g -1 at 5 A g -1 , demonstrating both enhanced capacity and superior rate performance. This work provides an efficient and scalable strategy for coating engineering in biomass-derived HC, offering valuable insights for the development of high-performance sodium-ion battery anodes.