Abstract
While major efforts are paid to increase the specific energy and power of energy storage devices to meet the demand of transport systems, an alternative approach is to turn the structural components of the systems into energy storage devices. For example, an all electric airplane powered by structural supercapacitors or batteries with a relatively low specific energy would fly the same range as one powered by a conventional storage device with a very high specific energy.
Structural supercapacitors were fabricated according to the schematic shown in Fig. 1. The graphite reinforcement (fiber) is attached with carbon nanofiber and mediators (redox molecules). The matrix is an ionic conducting polymer or adhesive polymer electrolyte. One of the main issues for structural supercapacitor is the low ionic conductivity of adhesive polymer electrolyte as separator and as matrix in reinforcement/electrode. The presence of mediators can increases the ionic conductivity in the electrode area up to 10
-2
S/cm. A new method for preparing epoxy adhesive based dual functional polymer electrolyte was adopted. The ionic conductivity of PVDF/LiTFS/epoxy electrolyte can reach to 3x10
-3
S/cm. All-solid-state structural supercapacitors with PVDF/LiTFS /epoxy electrolyte and the conventional supercapacitors with a high conductivity liquid electrolyte (0.1 S/cm) are fabricated and tested. They have similar size and weight. The cyclic voltammetry (CV) curves show that the all-solid-state structural supercapcitors with two electrolytes have a similar specific charge capacity of ~4 mAh/g (Fig. 2 and Fig. 3). Also, the in-plane elastic constant is 1-2 GPa and the in-plane ultimate strength of the all-solid-state structural supercapacitor with PVDF/LiTFS /epoxy electrolyte is 20 MPa. The electrochemical properties and the strength of the structural supercapacitor as functions of the composition of the adhesive electrolyte and the composition of the electrode material are evaluated experimentally.
Figure 1