Acidic aqueous solutions such as sulfuric acid (H2SO4) or phosphoric acid (H3PO4) for supercapacitors.
Gel polymer electrolytes like poly(ethylene oxide) (PEO).
Solid polymer electrolytes such as polyvinylidene fluoride (PVDF) and its copolymers.
Composite polymer electrolytes which may include inorganic fillers in a polymer matrix like PEO or PVDF3.
These electrolytes are chosen based on their compatibility with the specific conducting polymers and metal oxides.
here are some references.
De, Bibekananda, Soma Banerjee, Tanvi Pal, Kapil Dev Verma, Alekha Tyagi, P. K. Manna, and Kamal K. Kar. "Transition metal oxide/electronically conducting polymer composites as electrode materials for supercapacitors." Handbook of Nanocomposite Supercapacitor Materials II: Performance (2020): 353-385.
Teo, Li Ping, Mohd Hamdi Buraidah, and Abdul Kariem Arof. "Development on solid polymer electrolytes for electrochemical devices." Molecules 26, no. 21 (2021): 6499.
Khan, Shahab, Ishfaq Ullah, Mudassir Ur Rahman, Hamayun Khan, Abdul Bari Shah, Raed H. Althomali, and Mohammed M. Rahman. "Inorganic-polymer composite electrolytes: basics, fabrications, challenges and future perspectives." Reviews in Inorganic Chemistry 0 (2024).