Progress in the preparation of bamboo-derived hard carbon for sodium-ion batteries: Microstructure, mechanisms, and performance optimization

Hard carbon materials are considered to be the most promising anode materials for sodium-ion batteries. Bamboo-based hard carbon is widely used in the preparation of anode materials for sodium-ion batteries due to its low cost and abundant carbon source. However, the electrical properties of bamboo-based hard carbon materials prepared by direct carbonization often do not meet the demand due to the limitations of bamboo precursor components and structural properties. Therefore, adjusting and optimizing the composition and structure of bamboo precursors by modifying bamboo under specific conditions plays an important role in enhancing the sodium storage capacity and initial coulombic efficiency of hard carbon. This paper describes the structure of hard carbon, the sodium storage mechanism and the modification method of preparing hard carbon materials from bamboo, in which the modification method includes pretreatment, temperature-raising process and post-treatment, and looks forward to the development prospect of bamboo-based hard carbon anodes. Pretreatment can adjust the content of precursor cellulose, introduce new oxygen-containing groups as well as increase the porosity; modulation of the warming process can significantly optimize the pore properties of bamboo-based hard carbon and reduce the number of open pores; the post-treatment can effectively remove the residual metal ions and other impurities in the hard carbon material. The above modification methods can effectively improve the reversible specific capacity, ICE and cyclic stability of bamboo-based hard carbon. This paper provides basic guidelines and new directions for improving the electrochemical performance of bamboobased hard carbon and its application in sodium-ion batteries.