Porosity and tortuosity dynamics and their impact on lithium-ion battery performance with different separator structures
Agnesia Permatasari, Magnus So, Van Lap Nguyen, Takeru Yano, Gen Inoue
Abstract
Research on lithium-ion batteries (Li-ion batteries) has demonstrated that the structure and properties of the separator are critical factors influencing both battery performance and safety. This study investigates three distinct separator structures: foam, non-woven fabric, and uniaxially stretched. The focus is on the interaction between separator structure, thickness, and external conditions to identify key characteristics affecting performance. The foam separator exhibited superior performance, characterized by a more uniform porosity distribution compared to the other structures. This uniformity is crucial for optimizing ion transport and minimizing Li + concentration gradients, thus improving battery performance. Even at elevated C-rates, the foam separator generated less heat, an essential advantage for maintaining thermal stability during high charge/discharge cycles. Additionally, the study identified a significant challenge under high-pressure conditions, which resulted in a reduced separator thickness (13 μm). Under these conditions, battery capacity became immeasurable at a C-rate of 5. Although the foam separator showed promising features, its limitations under specific operational conditions suggest a need for further optimization. Nevertheless, the findings of this research provide important insights into the role of separator design in addressing challenges related to capacity, thermal stability, and operational limitations in lithium-ion batteries.