Flexible Solid‐State Supercapacitors with Enhanced Performance from Hierarchically Graphene Nanocomposite Electrodes and Ionic Liquid Incorporated Gel Polymer Electrolyte

Abstract

High energy density, durability, and flexibility of supercapacitors are required urgently for the next generation of wearable and portable electronic devices. Herein, a novel strategy is introduced to boost the energy density of flexible soild-state supercapacitors via rational design of hierarchically graphene nanocomposite (GNC) electrode material and employing an ionic liquid gel polymer electrolyte. The hierarchical graphene nanocomposite consisting of graphene and polyaniline-derived carbon is synthesized as an electrode material via a scalable process. The meso/microporous graphene nanocomposites exhibit a high specific capacitance of 176 F g −1 at 0.5 A g −1 in the ionic liquid 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIBF 4 ) with a wide voltage window of 3.5 V, good rate capability of 80.7% in the range of 0.5-10 A g −1 and excellent stability over 10 000 cycles, which is attributed to the superior conductivity (7246 S m −1 ), and quite large specific surface area (2416 m 2 g −1 ) as well as hierarchical meso/micropores distribution of the electrode materials. Furthermore, flexible solid-state supercapacitor devices based on the GNC electrodes and gel polymer electrolyte film are assembled, which offer high specific capacitance of 180 F g −1 at 1 A g −1 , large energy density of 75 Wh Kg −1 , and remarkable flexible performance under consecutive bending conditions.

All‐Solid‐State Fiber Supercapacitors with Ultrahigh Volumetric Energy Density and Outstanding Flexibility

“…[1][2][3][4][5][6][7][8] However, one of the key challenges of the FSCs in the light of their practical applications is to increase their volumetric energy density to the value approaching to or even exceeding those of microbatteries without sacrificing the power density, cycle life, and other performance para meters. [16][17][18][19][20][21][22][23][24][25] Therefore, increasing the voltage window would be an effective approach to achieve highefficiency FSCs.To this end, enormous efforts have been devoted to the fabrication of asymmetric FSCs (AFSCs) which make full utilization of the operational windows of both the positive and negative electrode materials. [16][17][18][19][20][21][22][23][24][25] Therefore, increasing the voltage window would be an effective approach to achieve highefficiency FSCs.…”

“…[9][10][11][12][13][14][15] Both the energy and power density of a SC is strongly dependent on the operating voltage, that is, V 2 (E = 1/2 CV 2 and P = V 2 /4R ESR , where C is the capacitance of the device, V is the operating voltage, and R ESR is the equivalent series resistance). [25][26][27][28][29][30][31][32] Nevertheless, the intrinsic characteristic voltage of water splitting (1.23 V) means that an aqueous electrolyte is limited to a potential domain of around 1 V, thus constraining the operating voltage to a maxi mum of 1.8-2.0 V, [28][29][30][31][32][33] which is indeed lower than that of Fiber supercapacitors (FSCs) represent a promising class of energy storage devices that can complement or even replace microbatteries in miniaturized portable and wearable electronics. [25][26][27][28][29][30][31][32] Nevertheless, the intrinsic characteristic voltage of water splitting (1.23 V) means that an aqueous electrolyte is limited to a potential domain of around 1 V, thus constraining the operating voltage to a maxi mum of 1.8-2.0 V, [28][29][30][31][32][33] which is indeed lower than that of Fiber supercapacitors (FSCs) represent a promising class of energy storage devices that can complement or even replace microbatteries in miniaturized portable and wearable electronics.…”

Extent of Pseudocapacitance in High‐Surface Area Vanadium Nitrides

“…This indicates that pseudocapacitance is the dominant charge‐storage mechanism in nitrides. This high pseudocapacitance observed for the vanadium nitride is most likely due to its electroactive nature, which allows for multiple oxidation state changes during electrochemical cycling . This explains why the areal specific capacitances (see Table ) are much higher than that for activated carbons (11 μF cm −2 ), the material in commercial supercapacitor devices ,.…”

Stretchable Supercapacitors as Emergent Energy Storage Units for Health Monitoring Bioelectronics

“…[42,76] For example, a highly stretchable H 3 PO 4 /PVA polymer electrolyte coupled with electrode of conductive polymer, namely polypyrrole, was reported, which showed an excellent fracture strain at 410% elongation and a high conductivity of 3.4 × 10 −3 S cm −1 . [85][86][87] Advances in hydrogel engineering also offer the opportunity to develop versatile gel electrolytes with additional features such as healability, biocompatibility, and transparency, [88][89][90][91][92] which can be valuable in some health monitoring context. Thereafter, various polymer matrixes have been utilized, including PMMA, PAA, PEO, PAM, and PVDF, [66,[78][79][80] and electrolytic salts such as KOH, LiCl, and LiClO 4 have also shown utility as the ion source.…”