Challenges and Approaches to Designing High-Energy Density Lithium-Sulfur Pouch Cells

Lithium-sulfur (Li-S) batteries are of great interest as next-generation energy storage devices in a wide variety of applications, due to their high specific capacity and the environmental abundance of sulfur. However, liquid electrolyte Li-S technology faces several challenges such as polysulfide shuttling, anode corrosion and sluggish cathode kinetics. Practical deployment of Li-S batteries requires evaluation in large-format, high energy density pouch cells. Stringent operating conditions such as high sulfur loading and operating current, low electrolyte amount, and limited anode quantity are required for high energy density pouch cells, which further curtails the electrochemical performance and cycle life. This review aims to provide an understanding of the different failure mechanisms of large-format Li-S pouch cells and formulate key design parameters of Li-S pouch cells that have high capacity, coulombic efficiency and long cycle life. Recent developments in Li-S pouch cells are then discussed, focusing on cathode and electrolyte design for polysulfide immobilization, accelerated sulfur conversion kinetics, and Li anode protection. A review of advanced characterization techniques suitable for Li-S pouch cell studies is also provided. Finally, viewpoints are offered on the remaining challenges and prospects to guide future research in scaling up Li-S technology for real-world applications.