Photopolymerization Kinetics and Improved Performances of Polyacrylate-Type Semi-interpenetrating Solid Polymer Electrolytes

Abstract

Abstract Crosslinking solid polymer electrolytes (SPEs) are expected to expedite the extensive application of lithium metal batteries (LMBs) by enabling appropriate ionic conductivity and good compatibility with the cathode. However, researchers tend to focus more on the performance of SPEs themselves, rather than delving deeply into the mechanisms by which the kinetic characteristics of random polymerization reactions influence SPE properties. In this work, semi-interpenetrating (semi-IPN) SPEs are fabricated by crosslinking poly(ethylene glycol) methacrylate (PEGMA) and poly(ethylene glycol) diacrylate (PEGDA) blended with lithium perchlorate under UV irradiation in the presence of 2-hydroxy-2-methylpropiophenone as the photoinitiator. By varying the number average molecular weights (Mn) of PEGMA (Mn = 300, 475, or 950 g mol–1) and PEGDA (Mn = 200, 400, 600, or 1000 g mol–1), respectively, a series of networks composed of acrylates with different glycol chain lengths are facilely obtained. Photopolymerization kinetics and gelation times of the semi-IPN systems are characterized by photo-differential scanning calorimetry and photo-rheology technology, respectively. The results show that the glycol chain length of the linear PEGMA segment shuttling in the polymer backbone plays a pivotal role in influencing the chemical dynamic features of the synthetic process, which are also confirmed by mechanical and electrochemical property measurements additionally. Furthermore, the cells assembled by the optimal semi-IPN SPEs achieve enhanced specific capacity and cyclability in solid-state LMBs, highlighting the practical significance of research on polymerization kinetics in guiding the design of state-of-the-art SPEs.