The role of carbonization temperature and amorphous components for the design and optimization of wood-based hard carbon thick electrodes in lithium-ion batteries

Abstract

Recently, wood-based hard carbon thick electrodes (WHCTEs) have achieved widespread attentions due to their 3-D transport network and high areal capacity. However, the roles of components in woods, especially the lignin and hemicellulose in influencing physical properties, microstructure, and lithium storage performance of WHCTEs remains unclear, which limits the design and application of WHCTEs. Herein, the effects of the carbonization process and components on the structural derivation and lithium storage properties of WHCTEs were investigated by varying the carbonization temperature and removing the amorphous components. Birch wood was carbonized at 800, 1000, and 1200 °C (CW-800, CW-1000, and CW-1200), respectively. Samples removed amorphous components were also carbonized at 800 °C (DE-800). The XRD results proved that appropriately increasing the carbonization temperature and removing amorphous components improved the graphitization degree. The HRTEM results confirmed that higher carbonization temperature facilitated the formation of closed pores. As the carbonization temperature increased, the mesoporous structure collapsed drastically; while DE-800 formed a mesoporous structure of 2–20 nm, thus presenting a superior rate performance and cycling stability. However, due to its low mass loading, the remaining capacity and the monolithic capacity only reached 1.61 mAh cm⁻²/0.77 mAh; while by the virtue of high post-carbonization density, CW-800 still maintained an areal capacity/monolithic capacity of 3.93 mAh cm⁻²/2.98 mAh after 100 cycles. It can be concluded that WHCTEs with amorphous components are promising to exhibit superior comprehensive performance. This work can provide some references for the design of WHCTEs and promote its practical applications.