Experimental investigation of overcharge caused sodium plating of hard carbon anodes for sodium-ion batteries

Sodium-ion batteries are strong candidates for secondary batteries for near-space vehicles. Although there aren’t many reports, the monitoring, failure, and mechanism of sodium plating in hard carbon anodes provide guidelines for the use and management of sodium-ion batteries. For this, a trustworthy understanding of the sodium plating behavior of hard carbons is provided by setting a series of sodium precipitation gradients, using differential capacity curves, combined with scanning electron microscopy (SEM) and galvanostatic intermittent titration technique (GITT). The results show that sodium clusters appear on the surface of the hard carbon at a current density of 20 mA/g for 12.5 h. The sodium clusters are converted into sodium-metal by continuing to sodiate for 2.5 h and the voltage of desodiation of the sodium-metal can be detected by the differential capacity curves. The battery’s cycling performance is not impacted by the sodium clusters because of their low formation energy; however, the sodium-metal causes an increase in the battery’s interfacial impedance and charge transfer impedance, which accelerates the degradation of the battery’s cycling performance.