3D printed solid-state composite electrodes and electrolytes for high-energy-density flexible microsupercapacitors

Although flexible microsupercapacitors (MSCs) have attracted significant attention for wearable electronics, their energy storage performance and energy density need to be improved for widespread applications. In this study, flexible MSCs displaying enhanced areal capacitance and energy density with high active material loading were fabricated; to realize this, three-dimensional (3D) printing was utilized to deposit an electrochemically stable ionic liquid (IL)-based solid-state ionogel electrolyte and a 3D interconnected large mesoporous carbon (3DMC)-based composite electrode. The ionogel consisting of 1-ethyl-3-methylimidazolium bis(trifluoromethyl sulfonyl)imide ([EMI][TFSI]) and polyvinylidene fluoride-co-hexafluoropropylene (P(VDF-HFP)) was employed to increase an operating potential range of the MSCs. The 3DMC composite electrode, which consists of 3DMC, single-walled carbon nanotubes (SWCNTs), P(VDF-HFP), and [EMI][TFSI], was successfully printed to facilitate ion transport of the ionogel and to customize 3D structures. 3D printed MSCs exhibited outstanding super-capacitive energy storage performance, including very high specific capacitance of 110.4 mF cm2, energy density of 60.6 mu Wh cm2, power density of 0.89 mW cm2, and outstanding mechanical durability of 97% capacitance retention after 1000 successive 90 degrees bending/releasing cycles. These results provide a promising strategy for fabricating flexible MSCs based on composite electrolytes and electrodes for superior supercapacitive energy storage performance.