A well-known strategy to achieve higher energy density in lithium-based batteries consists in using metallic lithium as the anode, however, the problematics associated are many and well-known. One solution to enhance battery safety consists in protecting lithium by using a solid electrolyte. Herein the preparation of a new solid polymer composite electrolyte, encompassing room-temperature ionic liquid (RTIL) and ceramic powder is reported. The methacrylate monomer, easily reticulated by UV-curing allows to obtain a highly crosslinked 3D structure matrix, rich in ethoxy groups, fundamental for Li+ conduction. Encompassing of RTIL and ceramic particles allows an enhancement of the ionic conductivity as well as mechanical properties, therefore highly reducing lithium dendrite formation.