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Highly Concentrated NaN(SO2F)2/3-Methylsulfolane Electrolyte Solution Showing High Na-Ion Transference Number under Anion-Blocking Condition (Supporting Information)

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posted on 14.09.2021, 06:52 by Ryoichi TATARA, Yukihiro OKAMOTO, Yosuke UGATA, Kazuhide UENO, Masayoshi WATANABE, Kaoru DOKKO
The performance of a sodium-ion (Na) battery is significantly influenced by its electrolyte characteristics. In particular, the transport properties of the electrolyte have considerable effects on the discharge rate capability. During discharging of a Na battery at high current densities, a concentration gradient of Na salt develops because both cations and anions are mobile in the liquid electrolyte. Concentration polarization can be suppressed by increasing the Na+ transference number (tNa+) of the electrolyte. This study demonstrates that highly concentrated NaN(SO2F)2 dissolved in 3-methylsulfolane (MSL) exhibits a high tNa+ value of >0.6 under anion-blocking conditions. Raman spectroscopy revealed that Na+ ions formed complexes with MSL and anions in the electrolyte. Na+ ions exchange ligands dynamically and move faster than the ligands, resulting in a high tNa+. The high tNa+ enables a high-rate discharge of the Na battery, despite the low ionic conductivity of the highly concentrated electrolyte.

Funding

Electrolyte design for high-speed alkali metal ion hopping conduction and high speed electrochemical reaction

Japan Society for the Promotion of Science

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Interface Ionics : Fabrication of model systems and their fundamental ion dynamics

Japan Society for the Promotion of Science

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Electric double layer in nanospace: Statistical analysis of experimental data and statistical analysis of calculated data

Japan Society for the Promotion of Science

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Ministry of Education, Culture, Sports, Science and Technology JPMXP0112101003

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Manuscript title

Highly Concentrated NaN(SO2F)2/3-Methylsulfolane Electrolyte Solution Showing High Na-Ion Transference Number under Anion-Blocking Condition