Precarbonization Facilitated Closed Pores Formation and Surface Graphitization on Bamboo-Derived Hard Carbon to Improve Sodium Storage Performance

Hard carbon (HC) was considered as a promising anode candidate for Na-ion batteries, due to its ability of efficient Na-ion storage. Bamboo-derived HC has the advantages of sustainability, environmental benefits and low cost, which are crucial for advancing the commercialization of SIBs technology. Precarbonization has been reported as a method to improve the electrochemical performance of HC anodes derived from various precursors, while the underlying mechanism behind why precarbonization improved the electrochemical performance of bamboo-derived HC has not been studied in detail. Herein, the effect of precarbonization on electrochemical behavior, bulk and surface structure, and surface composition was comprehensively explored. The results revealed that the improved reversible capacity was attributed to the increased closed pores for extra Na-ion storage, increased surface N content and decreased oxygen content for Na-ion absorption/desorption; the improved cycling stability was ascribed to the reduced surface oxygen and C-O content leading to suppressed side reactions, while the improved surface graphitization degree contributed to rate capability enhancement. This work clarified the role of precarbonization in improving the hard carbon anode for Na-ion batteries, which will be helpful to the commercialization of hard carbon materials.