Mikito Ueda, Hideki Hayashi and Toshiaki Ohtsuka
Graduate School of Engineering, Hokkaido University, Sapporo 060-8628
To develop a sodium electrorefining process for the recycling of used sodium-sulfur secondary battery, a non-aqueous electrolytic melt was investigated to pursue an efficient solvent and electrolyte for the process. Propylene carbonate containing NaPF6 was selected, since it has a wide potential window for electrochemical stability and a weak reactivity with metallic sodium. From the impedance measurement of propylene carbonate containing NaPF6, the maximum electric conductivity of 75 mS cm-1 was found at concentration of 1 M NaPF6 at 338 K. The cathodic deposition of metallic sodium on a glassy carbon electrode and the anodic dissolution of metallic sodium occurred in the electrolytic melt. Sodium and a small amount of phosphorus were detected in the electrodeposit by ICP-AES analysis.
sodium-sulfur secondary battery, electrorefining, recycle
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