Swelling Kinetics and Flory–Huggins Interactions in Thermally Aged Brominated Butyl Rubber and Silicone Rubber

This is the authors' abstract. We don't add key points for this paper.

This study investigated the effects of thermo‐oxidative aging on the swelling behavior and evolution of network structure for the brominated butyl rubber (BBR) and silicone rubber (SR) in lithium battery electrolytes through dynamic swelling kinetic tests. The swelling mechanism was elucidated combined with the Flory–Rehner theory and Flory–Huggins interaction parameter under simulated battery conditions, namely high‐temperature electrolyte immersion test. The results showed that thermo‐oxidative aging induced secondary crosslinking and caused a significantly increase in the crosslink density for BBR from 2.57 × 10 4 to 3.46 × 10 4 mol/cm 3 and SR from 6.14 × 10 4 to 6.75 × 10 4 mol/cm 3 . Despite the superior transport coefficients of SR due to its flexible siloxane chains, BBR exhibited an 11.2% higher swelling ratio at 80°C owing to the diminished elastic retraction of the crosslinking network. Furthermore, ethylene carbonate‐dominated electrolytes with higher polarity reduced the swelling by 18.3%–25.7% compared with that of Diethyl carbonate/Methyl ethyl carbonate ‐dominated electrolytes. It has been tried to correlate the swelling ratios of SR and BBR with the Flory–Huggins interaction parameter to quantify solvent compatibility and establish the theoretical guidance for predicting fluid resistance of battery seals.