Sodium carboxymethyl cellulose as a potential binder for hard-carbon negative electrodes in sodium-ion batteries

• A hard-carbon with CMC demonstrated good cyclability than that with PVdF.
• Effects of FEC additive depend on the combination with CMC and PVdF binders.
• The FEC is essential as electrolyte additive to improve the cyclability for the PVdF.
• Uniform coverage of hard-carbon by CMC promotes suitable electrochemical performance.

For a non-aqueous sodium-ion battery, a hard-carbon negative electrode with sodium carboxymethyl cellulose (CMC) binder demonstrates the superior reversibility and cycleability in NaPF6 propylene carbonate solution at room temperature to that with ordinary poly(vinylidene difluoride) (PVdF) binder. Furthermore, effects of monofluoroethylene carbonate (FEC) additive remarkably depend on the combination with binders, CMC and PVdF. Surface analyses reveal considerable differences in surface and passivation chemistry which depends on the binders and FEC additive used for the hard-carbon negative electrodes.