High modulus carbon fiber based composite structural supercapacitors towards reducing internal resistance and improving multifunctional performance

Carbon fibers (CFs) based composite structural supercapacitors (CSSs) are promising multifunctional energy storage composites which can simultaneously realize load bearing and electricity storage. The device power is still low due to the high internal resistance of CSS. Herein, the CFs, electrolytes, monofunctional devices and multifunctional composite devices were investigated to show the attribution of the internal resistances. Both the normally used T300 CF and high modulus M55J CF fabrics were utilized. The electric in-plane and through-the-thickness resistances of CF fabric electrodes were characterized, respectively. The internal resistance of the monofunctional supercapacitor devices which were assembled using liquid electrolyte were evaluated considering the effects of CF sizing. The bicontinuous structural electrolytes (BSEs) composed of epoxy (EP) and ionic liquid (IL) were prepared as the multifunctional matrix of the CSSs. The chemical structure, thermal stability and ionic conductivity of the BSEs were assessed. The activated carbon (AC) loaded CFs and BSEs were used to fabricate the CSSs. Both the tensile and charge/discharge properties of the M55J CF CSSs were higher than those of the T300 CF CSSs. This work could provide new insights into the resistance attribution of CSS and how to simultaneously improve both mechanical and electrochemical performances of CSSs.