Ultrasonically Dispersed Sodium Powders As Electrode Additives for Improved Cycling of Sodium Ion Batteries

Abstract

Solid electrolyte interphase (SEI) growth on the anode surface remains a major challenge to sodium ion batteries. Excessive SEI buildup in the formation cycles or later cycles would consume electrolyte, deplete available alkaline ions, and increase cell polarization. These issues with SEI growth become more prominent in full cells in which cathodes store limited amount of alkaline ions that are available for electrochemistry. The reduction in the amount of available alkaline ions upon cycling often results in low capacity and poor capacity retention in full cells. To compensate the Na loss from SEI formation, we developed a sodium powder based presodiation technique that could potentially be applied to both anode and cathode materials with minimal modification to conventional battery making process. The synthesis of sodium powders is accomplished via ultrasonic dispersion of molten sodium in mineral oil. When suspended in hexane, the sodium powders can be easily applied onto electrodes as presodiation additives. Reduction in the 1st cycle loss and enhancement in reversible capacity have been observed in this study.