A new class of highly thin, deformable, and safety-reinforced plastic crystal polymer electrolytes (N-PCPEs) is demonstrated as an innovative solid electrolyte for potential use in high-performance flexible lithium-ion batteries with aesthetic versatility and robust safety. The unusual N-PCPEs are fabricated by combining a plastic crystal polymer electrolyte with a porous polyethylene terephthalate (PET) nonwoven. Herein, the three-dimensional reticulated plastic crystal polymer electrolyte matrix is formed directly inside the PET nonwoven skeleton via in-situ UV-crosslinking of ethoxylated trimethylolpropane triacrylate (ETPTA) monomer, under co-presence of plastic crystal electrolyte. The PET nonwoven is incorporated as a compliant skeleton to enhance mechanical/dimensional strength of N-PCPE. Owing to this structural uniqueness, the N-PCPE shows significant improvements in the film thickness and deformability with maintaining advantageous features (such as high ionic conductivity and thermal stability) of the PCE. Based on structural/physicochemical characterization of N-PCPE, its potential application as a solid electrolyte for flexible lithium-ion batteries is explored by scrutinizing the electrochemical performance of cells. The high ionic conductance of N-PCPE, along with its excellent deformability, plays a viable role in improving cell performance (particularly at high current densities and also mechanically deformed states). Notably, the cell assembled with N-PCPE exhibits stable electrochemical performance even under a severely wrinkled state, without suffering from internal short-circuit failures between electrodes.