Multi-synergistic regulation of hard carbon via a green bioengineering strategy to achieve high-capacity sodium-ion storage†

Abstract

Biomass-derived hard carbon (HC) is the most promising anode material for commercial sodium-ion batteries (SIBs). However, the commercialization of HC still faces technical issues related to its insufficient reversible capacity and low initial coulombic efficiency. Although some techniques have been developed to circumvent these issues, they suffer from drawbacks such as complex preparation processes, environmental unfriendliness, and high processing costs. Herein, an ecofriendly bioengineering strategy based on the microstructure and composition regulation of bamboo as an HC source has been reported. The designed biomass-derived HC anode has a high reversible capacity (428.21 mA h g⁻¹) and outstanding initial Coulomb efficiency (90.72%) at 30 mA g⁻¹ superior to that of previously reported plant-based HC electrodes. Self-growing Coriolus versicolor (CV), a bothersome fungus, was ingeniously used to regulate the lignin content of the bamboo precursor generating abundant closed pores and increasing porosity, and the removed lignin can be converted into CV carbon fibers in a green manner. Moreover, CV carbon fibers with their hyperbranched structure provide a natural interpenetrative path for fast ion diffusion and electron transport as well as rich sodium-ion storage sites, thereby boosting their electrochemical performance. Note that the ash content in bamboo could be decreased via this natural bioengineering process without using common acid/base treatments. This study provides a cost-effective and green approach to synchronously modulate the microstructure and composition of biomass toward high-performance biomass-derived SIB anodes.