A Review of Sodium-Metal Chloride Batteries: Materials and Cell Design

The widespread electrification of various sectors is triggering a strong demand for new energy storage systems with low environmental impact and using abundant raw materials. Batteries employing elemental sodium could offer significant advantages, as the use of a naturally abundant element such as sodium is strategic to satisfy the increasing demand. Currently, lithium-ion batteries represent the most popular energy storage technology, owing to their tunable performance for various applications. However, where large energy storage systems are required, the use of expensive lithium-ion batteries could result disadvantageous. On the other hand, high-temperature sodium batteries represent a promising technology due to their theoretical high specific energies, high energy efficiency, long life and safety. Therefore, driven by the current market demand and the awareness of the potential that still needs to be exploited, research interest in high-temperature sodium batteries has regained great attention. This review aims to highlight the most recent developments on this topic, focusing on actual and prospective active materials used in sodium-metal chloride batteries. In particular, alternative formulations to conventional nickel cathodes and advanced ceramic electrolytes are discussed, referring to the current research challenges centered on cost reduction, lowering of the operating temperature and performance improvement. Moreover, a comprehensive overview on commercial tubular cell design and prototypal planar design is presented, highlighting advantages and limitations based on the analysis of research papers, patents and technical documents.