Non-graphitic carbon as sodium-ion battery anode materials with improved ratio of plateau to sloping capacities prepared from lignite-based organic maceral

Abstract

Herein, huminite concentrate is obtained from lignite with high yield of 68.9 % by density gradient separation, subsequently converted to non-graphitic carbon (HM-H) by carbonization at 1400 °C for 2 h. Huminite concentrate possesses relatively high oxygen content and considerable amount of aromatic component, with modest yield of volatile matter during pyrolysis, resulting in optimized carbon phase distribution and enhanced electrical conductivity of HM-H. Compared with HM prepared by direct carbonization of lignite, HM-H has slightly higher contents of pseudo-graphitic and graphite-like carbons, and lower content of highly disordered one. Notably, HM-H exhibits remarkably improved electrical conductivity (1773 S m−1) than HM (1406 S m−1). Compared with HM anode for SIBs, HM-H one delivers higher plateau capacity (170.1 mAh g−1) meanwhile lower sloping capacity (91.8 mAh g−1), with significantly improved rate and cycling performances. Full cell assorted with NaFe1/3Ni1/3Mn1/3O2 cathode and HM-H anode demonstrates higher energy density of 210.5 Wh kg−1 than its counterpart (193.8 Wh kg−1) at 20 mA g−1, with superior rate performance (208.6 mAh g−1 at 200 mA g−1) and a capacity retention ratio of 89.7 % after 100 cycles. This work provides a facile and effective strategy for preparing non-graphitic carbon as high-performance anode materials for SIBs.