Flexible all-gel-based supercapacitors

Flexible energy storage devices are important sources of power for flexible electronics such as role up screens and wearable electronics. Most of the flexible energy storage devices are based on using either carbon nanomaterials or using composite electrodes (carbon nanomaterials with conductive polymers). The main drawbacks of these approaches are: the cost, fabrication time consuming and difficulty of synthesizing proper carbon nanomaterials. An alternative promising approach is using the 3D nanostructured conductive polymer hydrogel, which exhibits good electrochemical performance and good mechanical properties. 3D nanostructured hydrogel has a porous nanostructured network, which has many advantages such as providing short pathways for electron transport and increasing the electrode-electrolyte penetration depth via pores. In addition, the porous structure can contribute to release chain’s strains due to the volume change during the charge-discharge processes. For energy storage devices that work under periodically critical engineering stresses, these hydrogels may suffer from micro cracks, which lead to degraded electrochemical performance over time, so increasing the flexibility of 3D nanostructured hydrogel is very important for flexible energy storage devices. In this thesis, we propose a new idea of synthesizing hybrid gel electrodes that are composed of 3D nanostructured hydrogel and small percentages of nonconductive gel (PANI+PEO). The conductive hydrogel was contributed to provide good electrochemical performance, and the nonconductive gel was used as a plasticizer to increase the flexibility of the hybrid gel electrodes. Adding small percentage of the plasticizer polymer in a controllable manner has kept high electrochemical performance, and greatly enhanced the mechanical properties of the flexible gel electrodes. In order to approve our idea, we designed three gel supercapacitors based on the differences in the PEO content in the hybrid gel electrodes, and then we performed a wide comparison among them in terms of electrochemical performance and the mechanical behavior.