Enhancing Specific Energy and Cycling Stability of High‐Temperature Na‐ZnCl₂ Batteries with Foam‐Based Electrodes

Abstract Sodium–zinc chloride (Na‐ZnCl₂) batteries offer a sustainable alternative to sodium–nickel chloride (Na‐NiCl₂) batteries but face challenges with low specific energy and cycle life. This study evaluates two electrode designs: conventional particle‐based Zn/NaCl granules and newly developed foam‐based Zn/NaCl electrodes. Particle‐based electrodes, with 30% Zn utilization, cycled in tubular cells with a mass loading of 1.13 g cm −2 and an areal capacity of 150 mAh cm −2 , achieve a specific energy of 231 Wh kg⁻¹ on electrode composite level at 15 mA cm⁻ 2 but suffer from degradation in voltage efficiency due to Zn agglomeration. To address this, foam‐based Zn/NaCl electrodes are developed, enhancing Zn utilization to 66%. Cycled in planar Na‐ZnCl₂ cells, these foam‐based electrodes achieve over 200 mAh cm −2 areal capacity at a mass loading of 1.04 g cm −2 , providing a specific energy of 336 Wh kg⁻¹ at 15 mA cm⁻ 2 with stable voltage profiles. The foam‐based design stabilizes the electrode microstructure, delivering a high cumulative discharge capacity of 5.4 Ah cm⁻ 2 with stable voltage efficiency. These results represent the highest mass loadings and areal capacities reported for sodium metal chloride cells to date, demonstrating their potential for enabling cost‐effective Na‐ZnCl₂ batteries for stationary energy storage applications.