Low Temperature Tolerant Organohydrogel Electrolytes for Flexible Solid-State Supercapacitors

Gel electrolytes are attracting growing interest in the field of flexible solid supercapacitors. So far, hydrogel electrolytes have been widely investigated, and high performance flexible supercapacitors based on these electrolytes have been realized. However, conventional hydrogel electrolytes contain massive solvent water, inevitably freeze and restrict ion transport at subzero temperatures, which fundamentally limits the utilization of supercapacitors in extreme low temperatures. A new organohydrogel electrolyte that successfully brings the advantages of outstanding flexibility and ionic conductivity at low temperatures by using H₂O/ethylene glycol as a dispersion medium is reported here. When applying the antifreezing organohydrogel electrolyte, the flexible solid supercapacitor with carbon nanotube paper electrodes (≈0.5 × 2.2 cm²) exhibits stable electrochemical performance (70.6% capacitance retained at −40 °C) and excellent cycling stability (only 11.7% capacitance decay over 5000 charge/discharge cycles at −20 °C.) at low temperatures, representing the excellent low temperature tolerance. Meanwhile, the supercapacitor devices offer remarkable flexible performance under consecutive bending conditions. It is anticipated that the low temperature tolerant organohydrogel electrolyte may be a promising gel electrolyte for the next generation of flexible solid supercapacitors for using at low temperature environments.