Low-temperature pre-oxidation and high-temperature activation modulate brewer’s spent grains-based hard carbon microcrystalline structure to enhance sodium storage properties
Jiawen Huangfu, Huimin Cao, Yuebin Xi, Qingwei Li, H. Wang, Shoujuan Wang, Fangong Kong
Abstract
Hard carbon materials are among the most promising materials for sodium-ion batteries. Influenced by sodium storage mechanisms such as intercalation and pore filling, the carbon layer spacing and closed-pore structure significantly affect the electrochemical performance of sodium-ion batteries. However, how to regulate the hard carbon structure through a simple method remains a huge challenge at present. In this work, we prepared hard carbon (OMHC-350–1400) with a large carbon layer spacing and abundant closed-pore structure through a strategy combining low-temperature pre-oxidation and high-temperature carbonization. Thanks to the introduction of a large amount of oxygen elements (from 14.49 % to 22.61 %) by pre-oxidation treatment, the carbon layer spacing of hard carbon widened from 0.366 nm to 0.384 nm, and a large number of closed pores were generated simultaneously. This provides abundant active sites for sodium ion storage. Compared with the hard carbon obtained without pre-oxidation treatment, the discharge capacity of OMHC - 350–1400 at 25 mAh g⁻¹ increased from 263.68 mAh g⁻¹ to 343.52 mAh g⁻¹ , the initial Coulombic efficiency (ICE) increased from 60.3 % to 72.6 %, and it showed a high capacity of 211.44 mAh g⁻¹ in the low-voltage discharge platform, with obvious advantages in electrochemical performance. This work aims to provide some references for the preparation of high-performance bio-based hard carbon.