Li2SO4-polyacrylamide polymer electrolytes for 2.0 V solid symmetric supercapacitors

•Li2SO4-polyacrylamide (PAM) was developed as neutral polymer electrolytes.•Li2SO4-PAM enabled solid CNT-based supercapacitor has a stable 2.0 V window.•The solid cell showed excellent rate capability (~ 5 V s− 1) and cycle life (> 10,000 ×).

A neutral polymer electrolyte comprised of lithium sulfate (Li2SO4) and polyacrylamide (PAM) was developed. The Li2SO4-PAM electrolyte film shows an ionic conductivity up to 10 mS cm− 1 in 45%RH conditions. Solid double layer capacitors were demonstrated using CNT-graphite electrodes and Li2SO4-PAM solid electrolytes. The voltage window of the solid cell was about 2.0 V, identical to that of a Li2SO4 liquid cell used as baseline. The demonstrated voltage window is significantly larger than that reported for proton- or hydroxyl-conducting electrolytes, suggesting that the Li2SO4-PAM electrolyte is a promising system for high energy density supercapacitors. The solid device also demonstrated excellent rate capability (up to 5 V s− 1) and good cycle life (beyond 10,000 charge/discharge cycles).

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