Self-supporting composite airgel electrode assembly having a very high energy density supercapacitor flexible all-solid
With wearable electronic and portable electronic devices such as flexible displays, electronic skin, clothing and other smart appearance and development, safety, reliability and flexibility of energy storage devices such as put forward higher requirements. Super capacitor is a new energy storage device between traditional capacitors and batteries to store energy Faraday oxidation reduction reaction in a fast desorption of the electrode material and the electrolyte ions or the interface completely reversible. Because of their high capacitance value with a battery elusive, high power density, long cycle life and low maintenance cost advantages attracted wide attention and research. Despite super capacitor has many advantages, however, the energy density ( 100Wh / Kg), and therefore restricts its wide application. The energy density of the formula E = 1 / 2CV2, can improve the energy density (E) by increasing the ratio of the capacitance (C) and the working voltage of the electrolytic solution supercapacitor electrodes (V). Recently, Professor Shaoqin Sarah Gong University of Wisconsin-Madison (corresponding author) and Doctoral Qifeng Zheng (first author) using the above strategy, the preparation of a self-supporting composite airgel electrode, and the development of an ion liquid / solid polymer electrolyte, the assembled whole with very high energy density of a flexible solid super capacitor (Q.Zheng, A.Kvit, Z.Cai, Z.Ma, S.Gong, a freestanding cellulose nanofibril-reduced grapheneoxide- molybdenum oxynitride aerogel film electrode for all-solid-statesupercapacitors with ultrahigh energy density, J Mater Chem a (2017) the electrode has many advantages: 1, the aspect ratio is high, a large specific surface dimension (CNF, of MoO3) and two-dimensional (GO) composite material, an electrode material is easy to form a self-supporting; 2, the airgel of graphite oxide (GO) by reduction with hydrazine hydrate in situ steam graphene (of RGO) process, CNF withMoO3 effectively prevent aggregation of RGO, give full play to the role storage graphene; 3, during reduction, MoO3 is partially reduced and the introduction of a small amount of nitrogen-doped material is formed pseudocapacitance MoOxNy, significantly improved the conductive electrode properties, electrochemical stability, and specific capacitance; 4, three-dimensional porous electrode can be supported more electroactive material thereby increasing the total capacity and the through-hole structure greatly facilitated the movement of ions or charge on the surface of electrode active material. The electrode exhibits ultrahigh gravimetric capacitance (680 F / g) and the area ratio of the capacitance (1700 mF / cm2) in 1.0 M sulfuric acid electrolyte; also in an ionic liquid electrolyte ultrahigh gravimetric capacitance (518 F / g) and the area ratio of the capacitance (1295 mF / cm2). The assembly of the electrode and the solid electrolyte based ionic liquid / polymer (PVDF-P407- [BMPY] [NTf2] Ionogel Electrolyte) symmetrical flexible all-solid super capacitor, its working voltage up to 3.6 volts, much higher than conventional the PVA / H2SO4 solid electrolyte. The super capacitor exhibits 262 F / g specific capacitance of the mass, and after the charge-discharge cycle test of 2000 times, but increase the capacitance value to 106% of the initial value. Meanwhile, the device exhibits very superior flexibility, it is folded in a different angle during the test, it was found cyclic voltammograms changed little. Remarkably, the all-solid flexible ultracapacitor energy density to the 114 Wh / kg (18.8 Wh / L), is the highest value of all solid super capacitor has been reported in the literature, and can be achieved with a lithium ion battery comparable degree (FIG. 2). The system operated by a clever design of materials and simple preparation process, targeted to solve problems supercapacitor. Three-dimensional porous structure of the airgel supercapacitors problem in ion transport, nitrogen-doped MoO3 solve pseudo capacitance material conductive and circulatory problems, an ionic liquid electrolyte solve the problem of the operating voltage, the self-supporting porous electrodes and a polymer flexible solid-state electrolyte to solve the problem. The study has important reference value to the research and development of flexible energy storage device of a high energy density, high power density.