Molten Salt Batteries for Grid Storage

Abstract

Increasing share of the intermittent renewable energy resources from PV and wind energy in the energy system has led to much progress in research and development in large scale batteries like molten salt batteries (MSBs) [1-6, 8] for grid storage. Compared to other batteries like Li-ion batteries, MSBs (e.g., ZEBRA (Na-NiCl2) battery [2, 3] and liquid metal battery [4, 5]) operate at higher temperatures (generally above 200°C) by using molten salts and liquid metals as active materials, and have the advantages, e.g., longer lifetime, lower costs, larger cell storage capacity. For the commercial ZEBRA battery, replacing Ni with abundant and low-cost Zn makes it more cost effective and could also reduce the operating temperature [6]. In the ongoing EU H2020 SOLSTICE project [7], two kinds of Na-ZnCl2 batteries are investigated. One uses the commercial ZEBRA concept [2, 3], i.e., a solid electrolyte is used in the battery, while another does not use the solid electrolyte to further improve its cost-effectivity and make it possible to have a MWh-scale storage capacity for each cell [8]. In this talk, the research and development of Na-ZnCl2 battery in this project, particularly on molten salt electrolytes, will be presented after a brief overview on the molten salt batteries. References [1] https://www.flashbattery.tech/en/molten-salt-batteries-operation-and-limits/, Molten-salt batteries: Pros and Cons of a 40-year-old “Innovation” (access on 2nd of March, 2023) [2] J. Sudworth, The sodium/nickel chloride (ZEBRA) battery, J. Power Sour., 100 (2001) 149. [3] G. Graeber, et al. Rational cathode design for high-power sodium-metal chloride batteries, Adv. Funct. Mater. 31 (2021) 2106367. [4] H. Kim, et al. Liquid metal batteries: Past, present, and future, Chem. Rev. 113 (2013) 2075. [5] H. Zhou, W. Ding, T. Bauer, et al., A sodium liquid metal battery based on the multi-cationic electrolyte for grid energy storage, Ener. Stor. Mater. 50 (2022) 572–579. [6] X. Lu, et al. A novel low-cost sodium–zinc chloride battery. Energy Environ. Sci. 6 (2013) 1837. [7] EU H2020 SOLSTICE project: https://www.solstice-battery.eu/ [8] J. Xu, et al. Na-Zn liquid metal battery. Journal of Power Sources, 2016, 332 274.