Delineating the relationship between separator parameters and practical lithium metal batteries characteristics

Abstract

Lithium metal batteries (LMBs), composed of lithium anodes and high-nickel-content LiNixMnyCozO2 (x + y + z = 1), are considered the pinnacle of next-generation batteries. Despite the importance of evaluating LMB in practical conditions, there is a lack of clear standards for LMB separators, which critically affects battery per-formance and energy density. Here, we investigated the effects of separator thickness on the cell performance and energy density of a practical LMB by using various-thickness polyethylene (PE) separators. As the separator thickness decreases the volumetric energy density increases and LMB performance improves. We also showed that pore closure in separators is a major roadblock hindering the long-term operation of LMBs. Therefore, we establish the ideal LMB separator design, which is a thin and robust separator having pore closure suppression functionality for ensuring long-term stable high-energy-density LMBs.