Energy storage belongs to the central topics in power supply chains, especially when intermittent renewables, such as wind and sun, take the lead among various energy sources. As electrochemical batteries offer short response time, high energy and power density, along with high efficiency, they became one of the most promising energy storage techniques. Currently lithium batteries are the first choice when portable electronics, electric vehicles and grid energy storage are concerned. However, due to limited reserves of raw materials various alternatives are considered. Among them solid state sodium metal batteries recently attracted vivid interest in the scientific community due to utilization of abundant raw materials, high energy density and increased safety.
A key factor determining performance and safety of the sodium metal electrochemical cell are the interfaces between the solid state electrolyte and the electrodes, as it is where charge transfer, a limiting step for operation of an electrochemical cell, occurs. In this work we aim to verify a hypothesis that wettability of a solid state electrolyte by metallic sodium is one of critical factors governing plating and striping behavior of sodium metal electrode. Four alloying additives were selected and tested as agents affecting contact angle: silicon, antimony, tin and indium, and two ceramic solid electrolytes were applied: β-Al₂O₃ and NaSICON Na₃Zr₂Si₂PO₁₂.
Contact angle between each of the molten alloys and two of the electrolytes were measured under argon atmosphere using static sessile drop technique. Charge transfer resistance of the electrode/electrolyte interface was measured for symmetrical Na/solid electrolyte/Na cells using electrochemical impedance technique. Critical current density was measured using galvanostatic method. Correlation between contact angle and electrochemical performance is discussed in this work.

Energy storage,Sodium metal batteries,Ceramic solid electrolytes,Wettability