Modulating the cathode interface in sodium-beta alumina-based semi-solid-state sodium cells using liquid-organic electrolytes

Abstract

Solid-state sodium batteries using solid electrolytes have attracted attention as sustainable and powerful electrochemical energy storage systems. Even though the sodium-beta alumina solid electrolyte shows excellent properties, the limited interface contact with both electrodes has limited its wide utilization in room-temperature cell systems. However, interface modifiers can reduce the interfacial resistance, enabling good electrochemical performance. In this paper, we test four different liquid-organic electrolytes (LOE) to modulate the cathode interface. The effect of 1 M NaClO₄ in propylene carbonate on the cell performance and the oxidic solid electrolyte was further investigated. We show that the LOE displacement, not the interphases, is the main reason for the impedance growth using a three-electrode cell, a setup rarely employed in solid-state batteries. The realized semi-solid-state sodium cells with modulated cathode interface achieve an area-specific resistance as low as 63 Ω cm² and a high capacity retention of 99.8% after 100 cycles at 1.0C and 30 °C. Hence, the presented approach is a simple and cost-effective way to enhance the cathode interface in sodium-beta alumina-based cells.