Development of all-solid-state mediator-enhanced supercapacitors with polyvinylidene fluoride/lithium trifluoromethanesulfonate separators

All-solid-state supercapacitors (SCs) were fabricated using a polyvinylidene fluoride (PVDF)/lithium trifluoromethanesulfonate (LiTFS) membrane as the separator and poly(ethylene oxide) (PEO)/lithium perchlorate (LiClO4) as the polymer electrolyte in the porous carbon electrodes. Two types of mediators, NaI/I2 and K3Fe(CN)6/K4Fe(CN)6, were added into the PEO/LiClO4 polymer electrolyte that was used to fabricate the electrodes. The voltage window in which the SCs operated was 2.5–3 V. The results of electrochemical measurements, including cyclic voltammetry and galvanostatic charge/discharge, indicated that NaI/I2-containing and K3Fe(CN)6/K4Fe(CN)6-containing SCs yielded high specific capacitances of 209.0 and 138.8 F g−1, respectively. In addition to high specific capacitances for the two mediator-containing SCs, both SCs delivered high specific energies (49.1 Wh kg−1 at 1.6 kW kg−1 for the NaI/I2-containing SC and 33.6 Wh kg−1 at 1.3 kW kg−1 for the K3Fe(CN)6/K4Fe(CN)6-containing SC) due to the wide voltage window and fast redox reactions between mediators.

► All-solid-state mediator supercapacitors are fabricated.
► The conductivity of the PVDF/LiClO4 membrane is as high as 1.741 × 10−2 S cm−1.
► The specific capacitance of the NaI/I2 containing supercapacitor is 209.0 F g−1.
► Specific energy and power are determined by electrochemical measurements.