Investigate the effect of electrolyte and additives on the electrochemical performance of commercial hard carbon materials based Na-ion batteries

Electrolytes play an important role in the battery components it determines the electrochemical window or the working potential region of the battery according to the LUMO and HOMO energy levels and reflects its thermodynamic stability when contacting with the electrode materials. The choice of the electrolyte affects significantly the specific energy, safety, cycle life, storage performance, or operating conditions of batteries. Besides, the electrolytes could be perfectly improved its performance within the addition of some essential additives, which also help to increase the performance of the battery. In this study, the effects of NaPF6, NaClO4, NaOTf, NaFSI, and NaTFSI salts on the hard carbon anode performance were investigated in the carbonate ester solvents including EC:DMC:PC (1:1:1) of 1 M salt concentration without and with additives FEC, VC, and Py13. The compatibility hard carbon electrode-electrolyte systems were investigated for their electrochemical performance by using Galvanostatic cycling with potential limitation, Cyclic voltammetry, and electrochemical impedance spectroscopy in coin-cell type. Among the studied electrolytes, the electrolyte EC:DMC:PC (1:1:1) + 1 M NaOTf exhibited the best electrochemical performance. The specific capacity was above 246 mAh/g after 100 cycles and the Coulombic efficiency higher than 99.6%.