Despite the fact that solid-state electrolytes have attracted broad research interests, the limited ion transfer and high interface impedance restrain their application in high-performance batteries with high cyclic stability and power density. Here, a new quasi-solid-state polymer electrolyte containing lightweight semiconducting hydrogenated borophene (HB) nanosheets, ionic liquids, and poly (ethylene oxide) is reported. The cyclic overpotential of the Li-Li symmetrical battery is about 65 mV lower than that of HB-free quasi-solid-state electrolyte, demonstrating the lower interface impedance. The interaction between lithium-ion and ethylene-oxide chains decreases owing to the existence of HB nanosheets and ionic liquids, which facilitates lithium-ion diffusion. The lithium bis(trifluoromethanesulfonyl)imide molecule surface adsorption at the HB nanosheets enhances the dissociation of lithium ions, and thus the matched lithium iron phosphate/Li full cell delivers the acceptable rate performance up to 5C. This work provides a new filler candidate to enhance the ionic conductivity of quasi-solid-state electrolytes that may facilitate to construct the high-performance HB nanosheets and ionic liquids-based lithium metal batteries.