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

Sodium-ion\nbatteries (SIBs) are regarded as cost-effective alternatives\nor competitors to lithium-ion batteries for large-scale electric energy\nstorage applications. However, their development has been hindered\nby the high cost of hard carbon (HC) anodes and poor electrochemical\nperformance. To enhance the sodium storage capacity and rate performance\nof HC, this study accelerated the electrochemical performance of coconut-shell-derived\nHC anodes for SIBs through N/O codoping using ball milling and pyrolysis.\nExperimental results demonstrate that the simultaneous introduction\nof N and O generates a synergistic effect, increasing the surface\noxygen-containing functional groups, defects, and interlayer spacing\nof coconut-shell-derived HC through the codoping of light elements.\nThe excellent strategy has increased the slope capacity and platform\ncapacity of HC, and the synergistic modification of N/O has increased\nits reversible specific capacity from 272 to 343 mA h g<sup>–1</sup> (30 mA g<sup>–1</sup>), with a retention rate of approximately\n92.1% after 100 cycles. In addition, it also exhibits an excellent\nrate performance, reaching 178 mA h g<sup>–1</sup> at 1500\nmA g<sup>–1</sup>. In summary, this study presents an effective\nstrategy for modifying biomass-derived HC.