Abstract:

An antifreezing soybean protein-based gel electrolyte was prepared by thermally induced polymerization using soybean protein(SPI), acrylamide(AAm) and ZnCl₂ as raw materials. The effect of temperature on its ionic conductivity and mechanical property was investigated, and the mechanism was then analyzed. The results showed that the gel electrolyte had excellent frost resistance, and the introduction of ZnCl₂ leaded to the formation of numerous Zn²⁺ solvation structures, which broke the hydrogen bonds among water molecules and reduced the freezing point of gel electrolyte. The synergistic effect of gel matrix and salt ions gave the gel electrolyte high compression resilience and fatigue resistance. The analysis of low-temperature ionic conductivity showed that when the ZnCl₂ concentration exceeded 5 mol/kg, the ionic conductivity of gel electrolyte was still 3.65×10^-3 S/cm at -30℃. The analysis of mechanical properties at low temperatures showed that the gel electrolyte could keep structural integrity after 100 compression cycles of 80% strain at -30℃, the stress retention remained more than 85% and the plastic deformation maintained 15%. At the same time, the gel electrolyte-based electrochemical capacitors assembled by gel electrolyte exhibited satisfied low-temperature resistance, which could work normally at -30℃ and maintain capacitance retention of 83.2%. The capacitance retention reached 92% after 10 000 cycles of charge and discharge at -30℃.

Key words: gel electrolyte, antifreezing performance, compression resilience, fatigue resistance, capacitance retention