A symmetric supercapacitor constructed using two dimensional siloxene sheets in an ionic liquid electrolyte exhibits high areal capacitance and energy density.

The design and development of self-charging supercapacitor power cells are rapidly gaining interest due to their ability to convert and store energy in an integrated device. Here, we have demonstrated the fabrication of a self-charging supercapacitor using siloxene sheets as electrodes and siloxene-based polymeric piezofiber separator immobilized with an ionogel electrolyte. The self-charging properties of the fabricated device subjected to various levels of compressive forces showed their ability to self-charge up to a maximum of 207 mV. The mechanism of self-charging process in the fabricated device is discussed via "piezoelectrochemical effect" with the aid of piezoelectrochemical spectroscopy measurements. These studies revealed the direct evidence of the piezoelectrochemical phenomenon involved in the energy conversion and storage process in the fabricated device. This study can provide insight towards understanding the energy conversion process in self-charging supercapacitors, which is of significance considering the state of the art of piezoelectric driven self-charging supercapacitors.

Wire type supercapacitors fabricated using titanium carbide sheets derived from Ti2AlC provide a high energy density of 210 nW h cm−1.

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compartments, namely, (i) energy harvesting and (ii) energy storage in which the former generates the energy while the latter is used to store the generated energy. [6,7] Renewable energy sources such as solar, wind, hydropower, mechanical energy (piezoelectric/triboelectric nanogenerator), and electrochemical energy (fuel cells) are used as energy harvesting system, whereas batteries and supercapacitors are used as energy storing system in the design of selfcharging power system. [8][9][10][11][12] Renewable power source based self-charging power system such as coupling of the solar cell/ photovoltaics with the electrochemical energy storage are commercialized for making use of the photon energy into useful energy. [13,14] Hitherto, the utilization of biomechanical energy for the selfcharging system is still in research level, and further efforts are needed to be undertaken for practical applications. The concept of self-charging and/or self-powered system for harvesting and storing mechanical and/or biomechanical energy becomes plausible after the research findings of Wang and co-workers for the first time when they designed a self-powered system using nanogenerator (NG) and supercapacitor in 2012. [2] Up to date two different types of self-charging power cells have been reported such as (i) external powering and (ii) internally integrating the system. [8,[15][16][17] In the former case, the mechanical energy harvester is externally connected to the energy storage device using a rectifier, whereas the latter uses an all-in-one integrated system which will be beneficial for several applications in portable and wearable devices due to their miniaturized size. [18,19] The pulsating alternating current output of nanogenerator is the major concern for the practical application of NG based self-charging power cells (SCPCs) due to their low energy conversion efficiency. [7,20] Therefore, the design and development of high-performance self-charging power cell with high energy conversion efficiency are highly essential. In this scenario, integrated self-charging supercapacitor power cell (SCSPC) utilizing supercapacitor as energy storage device attracts much attention compared to batteries mainly due to the fast charging rates of a capacitive type electrode; it can scavenge/store the piezo-electrochemically generated Self-charging supercapacitor power cell (SCSPC) received much attention for harvesting and storing energy in an integrated device, which paves the way for developing maintenance free autonomous power systems for various electronic devices. In this work, a new type of SCSPC device is fabricated comprising 2D molybdenum di-selenide (MoSe 2 ) as an energy storing electrode with polyvinylidene fluoride-co-hexafluoropropylene/ tetraethylammonium tetrafluoroborate (PVDF-co-HFP/TEABF 4 ) ion gelled polyvinylidene fluoride/sodium niobate (PVDF/NaNbO 3 ) as the piezopolymer electrolyte. The fabricated SCSPC delivers a specific capacitance of 18.93 mF cm −2 with a specific energy of 37.90 mJ cm −2 at a specific power...