Polyvinylidene fluoride gel‐polyethylene composite separator optimizing the interface compatibility between the separator and the electrode

The interface issue concerning lithium dendrite formation between the separator and electrode remains a significant impediment to the further advancement of lithium‐ion batteries (LIB). Due to the inadequate interface compatibility between the conventional polyolefin separator and the electrode, there is a propensity for lithium dendrite growth. In this work, the surface of the polyethylene (PE) separator is coated with polyvinylidene fluoride (PVDF) gel using a simple phase transformation method, resulting in the preparation of a composite separator consisting of PE and PVDF. The results demonstrate an enhanced interface compatibility following the introduction of the gel layer, with a polarization voltage as low as 0.14 V observed after 250 h of cycling. Additionally, the ionic conductivity of the PE/PVDF composite separator (1.77 mS cm−1) is enhanced, attributed to the incorporation of F functional group in PVDF gel, which could facilitate the formation of a rapid ion transport pathway through the interaction between F functional group and Li+. After the introduction of the gel layer, the discharge capacity of the battery after 250 cycles measures ~1.28 mAh, with a mere 27% decay in capacity. This study presents a novel concept for the design of composite separator in LIB. The gel layer is a superior strategy to optimize the interface compatibility between the conventional polyolefin separator and the electrode. In our study, the surface of the polyethylene (PE) separator is coated with polyvinylidene fluoride (PVDF) gel using a simple phase transformation method, resulting in the preparation of a composite separator consisting of PE and PVDF. The introduction of the gel layer enhances the interface compatibility between the conventional polyolefin separator and the electrode. The prepared PE/PVDF composite separator exhibits an increased lithium‐ion transference number (0.41) and enhanced ionic conductivity (1.77 mS cm−1). The cell has excellent cycle performance. After the introduction of the gel layer, the discharge capacity of the battery after 250 cycles measures ~1.28 mAh, with a mere 27% decay in capacity. At the same time, it also improves the rate performance of the cell. After 250 h of cycling, the polarization voltage is only about 0.14 V.