The effect of thermal treatment temperature on the crystal structure and electrochemical performance of the coconut shell-based hard carbon

The demand for energy has been increased, and the supply of lithium-ion batteries (LIBs) can not meet the demand for energy storage. Sodium-ion batteries (SIBs) have become ideal alternative products because of their low cost and the similar charge and discharge mechanism with LIBs. Meanwhile, the hard carbon anode materials have made tremendous progress, and the hard carbon materials which have the advantages of rich resources, low cost, and high-safety have been widely studied. Herein, carbonized coconut shell was used as raw material for the preparation of hard carbon, and the relationship between thermal treatment temperature and the crystal structure and electrochemical performance was investigated. It is found that the hard carbon prepared at 1300 °C has the best specific capacity. At the current density of 100 mA/g, it can reach 224.36 mAh/g after 100 cycles. The hard carbon material prepared at 1200 °C has the best rate performance, which can reach 54.5 mAh/g at the current density of 2 A/g.