High-performance PMMA based solvent-free solid transparent polymer electrolyte modified by succinonitrile for electrochromic devices

Abstract

To address the issues of the gel polymer electrolytes caused by solvents, like Propylene Carbonate (pc) and Ethylene Carbonate (ec), regarding cycling stability and safety, we prepared solvent-free PMMA-based solid polymer electrolytes using succinonitrile as a plasticizer (SN-PMMA) through the blade coating method. The mechanism of SN additives on dissociation of LiClO₄ and electrochemical properties was characterized using Fourier transform infrared spectroscopy, electrochemical impedance spectroscopy, and other structural investigation methods. The results indicated that SN is distributed uniformly in the PMMA matrix with high additive concentrations, and the nitrile group, which possesses strong polarity, effectively promoted the dissociation of lithium salt. The solvent-free SN-PMMA exhibits excellent ionic conductivity of 0.58 mS cm^-1 and good thermal stability. The solid Electrochromic devices (ECDs) prepared with SN-PMMA and WO₃ via thermal laminating process maintain 90.8 % modulation amplitude after 500 cycles, as well as good electrochromic performance, where the optical modulation amplitude is 62.1 % at λ = 633 nm, the coloring efficiency is 53.77 cm² C^-1, and the response time is 23.8 s/38.1 s for bleaching/coloration, respectively. These findings confirm the feasibility of using SN as a substitute for traditional solvents and provide a new pathway for developing solid-state polymer electrolytes with enhanced safety and superior electrochemical performance.