All-solid-state, flexible, symmetric, and asymmetric microsupercapacitors are fabricated by a simple method in a scalable fashion from laser-induced graphene on commercial polyimide films, followed by electrodeposition of pseudocapacitive materials on the interdigitated in-plane architectures. These microsupercapacitors demonstrate comparable energy density to commercial lithium thin-film batteries, yet exhibit more than two orders of magnitude higher power density with good mechanical flexibility.

The mechanism of self-discharge (SDC) in active electrolyte enhanced supercapacitors was investigated, and two strategies were devised to suppress the SDC process.

MoO(3) nanoplates were prepared as anode material for aqueous supercapacitors. They can deliver a high energy density of 45 W h kg(-1) at 450 W kg(-1) and even maintain 29 W h kg(-1) at 2 kW kg(-1) in 0.5 M Li(2)SO(4) aqueous electrolyte. These results present a new direction to explore non-carbon anode materials.

SCs and MSCs has been hindered by several issues. In particular, the synthesis, postreaction treatment, and instability of GO present processing challenges for widespread application. [ 14,22 ] In addition, the complex fabrication required for GO-based electrodes limits the cost potential and versatility of devices, particularly for MSCs with interdigitated structures. [ 4,23 ] Chemical vapor deposition has also been used to prepare graphene directly, but has limited scalability and often requires harsh synthetic conditions. [24][25][26][27][28][29] Laser scribing was recently developed to prepare porous graphene networks from polyimide. [ 30,31 ] This technology simplifi es the fabrication processes of MSCs compared to the photolithography approach, but still suffers from several limitations, such as limited compatibility with other substrates beyond polyimide and low energy storage ability. [ 4 ] Inkjet printing offers a desirable suite of advantages, including additive, non-contact, digital fabrication with high spatial resolution. Moreover, inkjet printing is an industrially mature technology, facilitating rapid transfer of technology from prototyping to manufacturing. The process and substrate compatibility achieved by this method, along with its commercial relevance, make the fabrication of microsupercapacitors by inkjet printing highly advantageous. However, challenges remain in the development of suitable graphene-based inks combining process compatibility and desirable electrical performance. Consequently, the development of a facile and scalable method for the fabrication of graphene electrodes for high-performance SCs and MSCs remains an outstanding challenge.Recent reports have demonstrated liquid-phase exfoliation of graphite for the production of stable graphene dispersions using the polymer ethyl cellulose in common, low-cost solvents such as ethanol and terpineol. [32][33][34][35] The graphene/ethyl cellulose (G/EC) system is suitable for applications in scalable fl exible electronics, with demonstrated processing ease and compatibility with a range of desirable substrates, as well as excellent electrical conductivity and mechanical fl exibility. Moreover, this system can be tailored for a range of additive manufacturing technologies including inkjet, gravure, and screen printing. [ 32,36 ] Herein, we extend this promising processing platform to electrochemical energy storage applications, realizing high-performance solid-state SCs. The suitability of the G/EC material for all-solid-state SC applications is fi rst evaluated using blade-coated and spin-coated thin-fi lm electrodes in sandwich-structured devices. In this confi guration, the high-conductivity, binder-free electrode mitigates the need for a separate current collector, simplifying the device fabrication process and eliminating potentially weak interfaces to enable Advances in thin-fi lm energy storage technologies are required to power the emerging fi eld of printed and portable electronics, with applications spanning biomedical and en...

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Solid materials with special atomic and electronic structures are deemed desirable platforms for establishing clear relationships between surface/interface structure characteristics and electrochemical activity. In this work, nickel boride (Ni x B) and nickel boride/graphene (Ni x B/G) are chosen as positive materials of supercapacitors. The Ni x B/G displays higher specific capacitance (1822 F g–1) than that of Ni x B (1334 F g–1) at 1 A g–1, and it still maintains 1179 F g–1 at 20 A g–1, suggesting the high rate performance. The asymmetric supercapacitor device (Ni x B/G//activated carbon) also delivered a very high energy density of 50.4 Wh kg–1, and the excellent electrochemical performance is ascribed to the synergistic effect of Ni x B, Ni­(BO2)2, and graphene that fully enhances the diffusion of OH– and the electron transport. During the cycles, the prepared ultrafine Ni x B nanoparticles will be gradually in situ converted into β-Ni­(OH)2 which has a smaller particle size than that prepared by other methods. This will enhance the utilization of Ni­(OH)2 and decrease the ion diffusion distance. The electron deficient state of B in Ni­(BO2)2 amorphous shell will make it easy to accept extra electrons, enhancing the adsorption of OH– at the shell surface. Moreover, Ni­(BO2)2 makes strong adhesion between Ni x B (or β-Ni­(OH)2) and graphene and protects the core structure in a stable state, extending the cycle life. The above properties of Ni x B/G endow the electrode good capacitive performance.

An electrochemical supercapacitor with a polymeric active electrolyte was designed and fabricated in this work. A water-soluble conducting polymer, sulfonated polyaniline (SPAni), was used in the supercapacitor as the active electrolyte and a semipermeable membrane was employed as the separator of the device. It was found that SPAni in the electrolyte can provide pseudocapacitance via its reversible electrochemical redox reaction. Owing to the good stability of SPAni, the supercapacitor has a long cycling life.Moreover, the migration of SPAni between the two electrodes was blocked by the semipermeable membrane separator, thus self-discharge caused by the shuttle effect of SPAni was suppressed. The research in this paper demonstrates the possibility of using a polymer as the active electrolyte in a supercapacitor and has paved a new way to achieve active electrolyte enhanced supercapacitors with high capacitance and good energy retention.

Polyaniline/graphene hydrogel composites with a macroscopically phase-separated structure are prepared. The composites show high specific capacitance and excellent rate performance. Further investigation demonstrates that polyaniline inside the graphene hydrogel has low rate performance, thus a phase-separated structure, in which polyaniline is mainly outside the graphene hydrogel matrix, can enhance the rate performance of the composites.