Li-SOCl2 batteries: Current status, practical challenges, and future perspectives

As a high-energy-density primary battery, the Li-SOCl2 battery offers significant advantages over other primary systems, including a high operating voltage, wide temperature tolerance, and low self-discharge rate. However, owing to the irreversible electrochemical reaction mechanism, despite its energy density of up to 700 Wh kg−1 at the cell level, this battery system has remained confined to the category of primary batteries, thereby limiting its use in cyclic applications. Recent advances in electrochemical technologies have enabled the reversible redox chemistry of Li-SOCl2 batteries, transforming them into rechargeable systems. This article provides a systematic overview of the technical evolution, reaction mechanisms, safety constraints, engineering countermeasures, and electrochemical performance enhancement of Li-SOCl2 primary batteries since their introduction. First, the modification methods for the lithium anode, carbon cathode, electrolyte, and electrocatalyst in Li-SOCl2 primary batteries are discussed, along with their mechanisms for improving electrochemical performance. We then review the SOCl2-based rechargeable Li metal batteries (LMBs) that evolved from the Li-SOCl2 primary batteries. With their higher energy density, these systems have become promising candidates to replace traditional Li-ion batteries (LIBs). This review focuses on the construction of key components, such as the positive electrode carrier, novel alloy anode, and electrolyte, as well as their impact on electrochemical performance in rechargeable batteries. Finally, we summarize current research progress and propose future directions for SOCl2-based LMBs aimed at enhancing overall electrochemical performance. These insights provide a theoretical foundation for the development of next-generation high-energy-density energy-storage technologies.