Mercerization-enhanced cellulose-II cotton fiber-based low-temperature hard carbon for sodium-ion batteries

Abstract

Hard carbons from cellulose are highly regarded as promising anode options for sodium-ion batteries (SIBs). However, a high carbonization temperature (>1300 °C) is usually required to obtain high-performance hard carbons, which leads to high-energy consumption and high cost. Moreover, hard carbons generally have poor rate capability and unsatisfactory cyclability which restrict their commercial applications. Herein, a low-temperature (900 °C) approach for the preparation of high-quality hard carbons for SIBs from waste cotton fibers is reported. It involves a mercerization pretreatment to convert cellulose-I cotton fibers into cellulose-II structure and dissolve the amorphous cellulose to form highly crystalline cellulose. This pretreatment process benefits forming abundant pseudo-graphitic structures at a low carbonization temperature of 900 °C. Consequently, the mercerized cotton fibers-based carbons (MCFC) exhibit excellent sodium storage properties, possessing a high capacity (316 mAh g−1 at 0.1 A g−1), high-rate capability (210 mAh g−1 at 10 A g−1), and long-term cyclability (83.2 % retention after 3000 cycles). This mercerization approach coupled with waste cotton fibers provides a sustainable pathway for the preparation of high-quality hard carbons for SIBs.