AlCl3-NaCl-ZnCl2 Secondary Electrolyte in Next-Generation ZEBRA (Na-ZnCl2) Battery

Abstract

first_pagesettingsOrder Article Reprints Open AccessArticle AlCl3-NaCl-ZnCl2 Secondary Electrolyte in Next-Generation ZEBRA (Na-ZnCl2) Battery by Sumit Kumar 1,*,†ORCID,Wenjin Ding 1,*,†ORCID,Ralf Hoffmann 1,Louis Sieuw 2,Meike V. F. Heinz 2ORCID,Norbert Weber 3 andAlexander Bonk 1ORCID 1 Institute of Engineering Thermodynamics, German Aerospace Center (DLR), 70569 Stuttgart, Germany 2 Empa, Swiss Federal Laboratories for Materials Science and Technology, 8600 Dübendorf, Switzerland 3 Helmholtz-Zentrum Dresden-Rossendorf (HZDR), 01328 Dresden, Germany * Authors to whom correspondence should be addressed. † These authors contributed equally to this work. Batteries 2023, 9(8), 401; https://doi.org/10.3390/batteries9080401 Received: 30 June 2023 / Revised: 26 July 2023 / Accepted: 29 July 2023 / Published: 1 August 2023 (This article belongs to the Special Issue High Performance Sodium Rechargeable Batteries and Beyond) Download Browse Figures Versions Notes Abstract Increasing demand to store intermittent renewable electricity from, e.g., photovoltaic and wind energy, has led to much research and development in large-scale stationary energy storage, for example, ZEBRA batteries (Na-NiCl2 solid electrolyte batteries). Replacing Ni with abundant and low-cost Zn makes the ZEBRA battery more cost-effective. However, few studies were performed on this next-generation ZEBRA (Na-ZnCl2) battery system, particularly on its AlCl3-NaCl-ZnCl2 secondary electrolyte. Its properties such as phase diagrams and vapor pressures are vital for the cell design and optimization. In our previous work, a simulation-assisted method for molten salt electrolyte selection has shown its successful application in development of molten salt batteries. The same method is used here to in-depth study the AlCl3-NaCl-ZnCl2 salt electrolyte in terms of its phase diagrams and vapor pressures via FactSageTM and thermo-analytical techniques (Differential Scanning Calorimetry (DSC) and OptiMeltTM), and their effects on battery performance such as operation safety and charging/discharging reaction mechanism. The DSC and OptiMelt results show that the experimental data such as melting temperatures and phase changes agree well with the simulated phase diagrams. Moreover, the FactSageTM simulation shows that the salt vapor pressure increases significantly with increasing temperature and molar fraction of AlCl3. The obtained phase diagrams and vapor pressures will be used in the secondary electrolyte selection, cell design and battery operation.