The cost of sodium‑zinc molten salt batteries for grid-scale energy storage

Decarbonising power grids requires affordable storage to accommodate surplus wind and solar electricity over periods of hours to days. Batteries made from abundant elements offer a scalable solution. High-temperature molten salt devices such as sodium‑nickel-chloride (Na-NiCl 2 ) batteries are commercial, but their cost remains a barrier. Replacing nickel with cheaper zinc could enable the needed savings, but the techno-economic potential of sodium–zinc (Na–Zn) batteries remains untested. We present the first cost and performance assessment of a solid-electrolyte Na-ZnCl 2 battery. Using a bottom-up engineering model and Monte Carlo uncertainty analysis, we find a baseline 240-cell module achieves project-level capital costs of 246–273 USD per kWh capacity, and a levelised cost of storage (LCOS) of 164–195 USD per MWh delivered, if 2030 performance targets are met. These values undercut 2024 prices for stationary lithium-ion systems, and increasing cell capacity to 1.1 kWh or enlarging modules to 15,360 cells lowers LCOS by up to 30%, competitive with leading 4-hour lithium-ion forecasts. Sensitivity analysis shows manufacturing scale and inactive-material reduction outweigh raw-material price in driving cost, challenging the view that cheap zinc alone guarantees competitiveness. Our results provide a clear R&D roadmap and position sodium‑zinc batteries as a mineral-lean complement to lithium-ion for reliable, long-duration, grid-scale energy storage. • First techno-economic study of sodium–zinc chloride battery modules • Baseline module achieves 164–195 USD/MWh lifetime cost, beating 2024 lithium-ion. • Increasing module or cell size could reduce costs by 7–14%, matching 2030 Li-ion. • Manufacturing scale and design, not zinc price, dominates cost drivers. • We map an R&D path to mineral-lean, long-duration storage for clean grids.