Solid state polymer electrolyte is a promising candidate for the next generation of all-solid-state lithium ion batteries due to its advantages of light weight, high stability to electrodes, non-flammable, sufficient mechanical strength to prevent lithium dendrite growth, and low cost. Here, through a facile and cost-effective route, two dimensional boron nitride (BN) is applied as an efficient additive in a polymer/salt hybrid electrolyte, which brings about high ionic conductivity, improved mechanical strength and intimate interfacial contact between the electrolyte and electrodes. A 1% BN addition into polymer/salt hybrid electrolyte membrane exhibits a high conductivity of 1.82 × 10−3 S/cm at room temperature. Indentation test shows the BN modified hybrid electrolyte possesses an enhanced hardness (4.99 MPa) and Young's modulus (0.133 GPa). The 1% BN modified hybrid electrolyte is demonstrated to effectively suppress the lithium dendrite growth during repeated striping and plating of lithium. As a result, the battery of lithium metal anode paired with LiFePO4 cathode and using the as-fabricated 1% BN enhanced polymer/salt hybrid electrolyte exhibits improved cycling performance with high Coulombic efficiency (over 98%).