Solid polymer electrolytes (SPEs) are a promising substitute, offering benefits such as improved energy density and safety compared to liquid electrolytes. However, low ionic conductivity, poor mechanical strength, weak interfacial contact, and electrode metal corrosion may still be critical problems in SPEs. Here, a composite solid polymer electrolyte (CSPE) is prepared using the standard solution casting technique, incorporating P(VDF-HFP)-PVAc-LiTFESI-EC with hydrothermally derived spherical ZrO2 as a passive ceramic filler. Notably, incorporating 5wt % ZrO2 in the SPEs leads to a notable twofold increase in ionic conductivity compared to bare SPE. This improvement is mainly attributed to ZrO2 facilitating Li+ migration channels and immobilizing free anions, likely by suppressing the crystallinity of the bare SPE and its Lewis acid-base nature. Additionally, CSPE demonstrates high mechanical strength, excellent thermal stability, a wide electrochemical window, and favorable electrolyte affinity. This promising material is well-suited for developing robust and efficient electrolytes for various applications.