Article
A high-voltage, low-temperature molten sodium battery enabled by metal halide catholyte chemistry

https://doi.org/10.1016/j.xcrp.2021.100489Get rights and content
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Highlights

  • Increase battery voltage 25% and decrease temperature from 300°C to 110°C

  • GaCl3-NaI-based catholyte uses I/I3 redox for 223 Wh/L theoretical energy density

  • Demonstrate stable cycling at 110°C for >8 months using polymeric seals

Summary

Despite its promise as a safe, reliable system for grid-scale electrical energy storage, traditional molten sodium (Na) battery deployment remains limited by cost-inflating high-temperature operation. Here, we describe a high-performance sodium iodide-gallium chloride (NaI-GaCl3) molten salt catholyte that enables a dramatic reduction in molten Na battery operating temperature from near 300°C to 110°C. We demonstrate stable, high-performance electrochemical cycling in a high-voltage (3.65 V) Na-NaI battery for >8 months at 110°C. Supporting this demonstration, characterization of the catholyte physical and electrochemical properties identifies critical composition, voltage, and state of charge boundaries associated with this enabling inorganic molten salt electrolyte. Symmetric and full cell testing show that the catholyte salt can support practical current densities in a low-temperature system. Collectively, these studies describe the critical catholyte properties that may lead to the realization of a new class of low-temperature molten Na batteries.

Keywords

battery
sodium
NaSICON
energy storage
grid scale
molten salt

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