Display omitted •A solid electrolyte membrane (HSE) was fabricated via a solution casting method.•The HSEs consist of LALZO/h-BN composite filler and PVDF-HFP matrix.•The HSE with an optimal h-BN amount showed improved electrochemical properties.•The ASSB assembled with the HSE membrane showed superior battery performance. Hybrid solid electrolytes (HSEs) have received intensive attentions for all-solid-state lithium-based batteries (ASSBs) because of their high ionic conductivity, high mechanical strength, improved electrochemical stability, and effective lithium dendrite suppression capability. In this study, free-standing HSE membranes were fabricated using a poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) matrix and Li6.28Al0.24La3Zr2O12 (LALZO)/hexagonal-BN (h-BN) composite ceramic fillers with different amounts of h-BN. The optimal proportion of h-BN (10 wt%) in the HSE membrane reduces the crystallinity of PVDF-HFP matrix, increases the proportion of the electroactive β phase, and enhances the mechanical strength of the HSE membrane. Furthermore, the PVDF-HFP/LALZO/h-BN 10% HSE membrane exhibited improved electrochemical properties, for example, a lithium-ion transference number of 0.63 at 55 °C, ionic conductivity of 1.1 × 10-4 S cm−1 at 25 °C, electrochemical stability window of ~5.0 V vs. Li/Li+, and effective lithium dendrite suppression capability. The ASSB consisting of a LiFePO4 cathode, PVDF-HFP/LALZO/h-BN 10% HSE, and Li metal anode delivered improved battery performance with an average capacity of 131 mAh g−1 at 0.2C, > 99% coulombic efficiency, and a capacity retention of 92% after 100 cycles.