Ball-Milling-Assisted N/O Codoping for Enhanced Sodium Storage Performance of Coconut-Shell-Derived Hard Carbon Anodes in Sodium-Ion Batteries

Sodium-ion batteries (SIBs) are regarded as cost-effective alternatives or competitors to lithium-ion batteries for large-scale electric energy storage applications. However, their development has been hindered by the high cost of hard carbon (HC) anodes and poor electrochemical performance. To enhance the sodium storage capacity and rate performance of HC, this study accelerated the electrochemical performance of coconut-shell-derived HC anodes for SIBs through N/O codoping using ball milling and pyrolysis. Experimental results demonstrate that the simultaneous introduction of N and O generates a synergistic effect, increasing the surface oxygen-containing functional groups, defects, and interlayer spacing of coconut-shell-derived HC through the codoping of light elements. The excellent strategy has increased the slope capacity and platform capacity of HC, and the synergistic modification of N/O has increased its reversible specific capacity from 272 to 343 mA h g^–1 (30 mA g^–1), with a retention rate of approximately 92.1% after 100 cycles. In addition, it also exhibits an excellent rate performance, reaching 178 mA h g^–1 at 1500 mA g^–1. In summary, this study presents an effective strategy for modifying biomass-derived HC.