Molecular tailoring of biomass precursor to regulate hard carbon microstructure for sodium ion batteries

Abstract

Hard carbon (HC), produced through high-temperature pyrolysis of biomass materials, has been considered as one of the most practical anodes in sodium ion batteries. And oxygen pre-treatment prior to pyrolysis is commonly used to change carbon layer growth and its microstructure, leading to improved electrochemical performance. However, existing pre-treatment methods are uncontrollable and require high temperatures, failing in precise regulating the structure of precursor and derived HC. In addition, excessive oxygen introduced during precursor pre-treatment remains after carbonization, leading to lower initial coulombic efficiency (ICE). Herein, a molecular tailoring strategy is proposed to successfully control the precursor structure, avoiding oxygen remaining on the HC surface and increasing the number of closed pores in HC. Thus, the prepared HC exhibits a high ICE of 90 % and reversible capacity of 337.3 mAh/g. This work provides a new path for precisely regulating the HC microstructure at the molecular level to construct HC anodes for high-performance sodium-ion batteries.