Conclusion In summary, a soft matter solid electrolyte with remarkably high ambient temperature ionic conductivity, wide electrochem-ical window and flexible mechanical strength was successfully prepared by in-situ thermal polymerization for lithium ion batter-ies. The plastic crystal electrolytes 92.5% [LiTFSI–SN]-7.5%TMPTMAexhibited well cross-linked three-dimensional framework andexcellent electrochemical properties. The in-situ thermal polymer-ization greatly simplified the assembly process of the polymerlithium ion batteries. The addition of polymer not only improved itsmechanical strength but also had no obviously detrimental effect in terms of loss of ionic conductivity. The exceptional electro-chemical stability of LiFePO4as the cathode material makes the polymer electrolytes containing plastic crystal extremely promising for application in lithium ion batteries. We strongly believe that the combination of enhanced mechanical and electrical prop-erties renders the polymer electrolytes containing plastic crystal a potential candidate as an electrolyte of Li-ion polymer batteries.