Improvement of the Electrode–Electrolyte Interface Using Crosslinked Carbonate-Based Copolymers for Solid-State Lithium-Ion Batteries

To enhance the stability and capacity of discharge in a solid-state battery system, we created a design that uses the same carbonate-based copolymer for a solid polymer electrolyte (SPE) and a polymer binder in a cathode. Here, we report on the crosslinked copolymer at different mol% of the allyl side group and the obtained crosslinked copolymer at 4.0 mol% (CP1) and 7.7 mol% (CP2) of the allyl side group, which were characterized by using NMR, TG/DTA, DSC, and a tensile test. The results show that CP1 and CP2 had better mechanical and thermal properties than the carbonate polymer. The superior thermal resistance behavior and good mechanical properties of the crosslinked carbonate-based copolymer were confirmed and were promising under high temperatures and longer cycles than the original copolymer electrolyte at the same salt concentration of 80 mol%. The results reveal that the addition of a crosslinked carbonate-based copolymer for the binder increased the discharge capacity by as much as 140 mAh g−1 because of the reduced resistance, which was confirmed by electrochemical impedance spectroscopy (EIS), while the PVDF binder at 100% of the cathode provided a change of only 107 mAh g−1. This research shows that using the same polymer for a binder and an SPE as a homogenous system can potentially improve a battery’s performance.