Clay-Mineral-Coated Separators for Lithium-Ion Batteries: Exploring the Relationships between Clay Mineral Morphology and Separator Performance.

Polyolefin separators comprising polyethylene and polypropylene have long been used in commercial Li-ion batteries because of their electrochemical stability, robust mechanical properties, uniform pore structure, and cost-effectiveness. However, conventional separators have limitations in withstanding harsh environmental conditions, such as elevated temperatures, owing to their poor mechanical durability. Moreover, with the development of advanced Li rechargeable batteries, these separators are required to overcome new challenges such as preventing the migration of polysulfide intermediates in Li-S batteries and inhibiting the formation of Li dendrites in Li metal batteries. Natural clay minerals have emerged as a viable solution to these issues owing to their porous structure, high mechanical strength, and abundant polysulfide-capturing Lewis acid sites. However, the manner in which the structural characteristics of minerals influence the separator performance has not been extensively assessed, thereby impeding the development of separators for future high-performance Li batteries. This review comprehensively outlines various clay minerals and their effects on the parameters and performance metrics of battery separators. Based on this review, a design guide is proposed for mineral-based separators that could potentially be integrated into next-generation Li batteries with high energy density and long-term stability.