We demonstrate a facile approach to fabrication of a self-standing plastic crystal composite electrolyte for a lithium-ion battery, wherein UV (ultraviolet)-cured ethoxylated trimethylolpropane triacrylate (ETPTA) networks are incorporated into a plastic crystal electrolyte (PCE, 1M lithium bis-trifluoromethanesulphonimide (LiTFSI) in succinonitrile (SN)). An ETPTA monomer having trifunctional groups is successfully crosslinked within a very short UV-exposure time of 20s without using any solvent, leading to the formation of a self-standing, transparent, and non-sticky plastic crystal composite electrolyte (X-PCCE). Owing to the introduction of the UV-cured ETPTA networks, the X-PCCE is capable of providing unprecedentedly robust mechanical strength even at a high concentration of PCE (i.e., ETPTA/PCE=15/85%, w/w), along with affording high ionic conductivity. In contrast, a conventional plastic crystal composite electrolyte (F-PCCE) comprising polyvinylidenefluoride-co-hexafluoropropylene (PVdF-HFP) and PCE is difficult to be fabricated as a self-standing film and easily deformed by weak external stress. Notably, the X-PCCE shows significant improvement in electrochemical stability and interfacial resistance toward lithium metal electrodes. Ionic conductivities of the X-PCCE and the F-PCCE are examined as a function of temperature and discussed under consideration of the interaction between SN, LiTFSI, and polymers in the plastic crystal composite electrolytes.