Micro-supercapacitor Device Research Articles

Sputtered thin film deposited laser induced graphene based novel micro-supercapacitor device for energy storage application

Pioneering flexible micro-supercapacitors, designed for exceptional energy and power density, transcend conventional storage limitations. Interdigitated electrodes (IDEs) based on laser-induced graphene (LIG), augmented with metal-oxide modifiers, harness synergies with layered graphene to achieve superior capacitance. This study presents a novel one-step process for sputtered plasma deposition of HfO2, resulting in enhanced supercapacitance performance. Introducing LIG-HfO2 micro-supercapacitor (MSC) devices with varied oxygen flow rates further boosts supercapacitance performance by introducing oxygen functional groups. FESEM investigations demonstrate uniform coating of HfO2 on LIG fibers through sputtering. Specific capacitance measurements reveal 6.4 mF/cm2 at 5 mV/s and 4.5 mF/cm2 at a current density of 0.04 mA/cm2. The LIG-HfO2 devices exhibit outstanding supercapacitor performance, boasting at least a fourfold increase over pristine LIG. Moreover, stability testing indicates a high retention rate of 97% over 5000 cycles, ensuring practical real-time applications.

High-voltage (> 3 V) energy storage device based on sputter-grown TiCrN microelectrodes towards miniaturized applications

In this work, we report sputter-grown micro-patterns of titanium chromium-based bimetallic nitride (TiCrN) over Si/SiO2 substrate. The highly stable TiCrN-micro pattern is tested electrochemically and used to construct an efficient microsupercapacitor (MSC) device. To achieve a stable and high-voltage window, a non-aqueous gel polymer electrolyte (GPE) of TEABF4/EC/PC/PVDF is optimized. At room temperature, the GPE exhibits high ionic conductivity of ~10.58 mS cm−1 with exceptional mechanical stability. A symmetric supercapacitor based on TiCrN sandwich structure (TiCrN-SS) is fabricated with TEABF4 GPE for practical application. The TiCrN-SS device works on a high voltage of 3.1 V and exhibits good electrochemical properties. The device shows a high energy density of 1.9 μWh cm−2 (5.9 Wh kg−1) at a power density of 109 μW cm−2 (0.34 kW kg−1). To utilize the excellent performance of TiCrN-SS as a miniaturized power source, an on-chip MSC is subsequently fabricated by patterning planar interdigitated TiCrN-microelectrodes. The constructed on-chip TiCrN microsupercapacitor (TiCrN-MSC) works on a wide voltage window of 0–3.1 V while maintaining an optimum areal capacitance of ~500 μF cm−2 at 0.07 mA cm−2 current density. The device exhibits an areal energy density of ~0.7 μWh cm−2 with an optimum 169.02 μW cm−2 power density. This remarkable electrochemical performance and exceptionally wide voltage window of TiCrN-based MSC makes it a potential candidate for direct use as a miniaturized power source in microelectronic devices.

Centrifugal-Gravity-Enforced Deposition of MXene Electrodes for High-Performance and Ultrastable Microsupercapacitors.

Two-dimensional (2D) transition metal carbides, known as MXenes, have captured much attention for their excellent electrical conductivity and electrochemical capability. However, the susceptibility of MXenes to oxidation, particularly Ti3C2Tx transforming into titanium dioxide upon exposure to ambient air, hinders their utilization for extended operational life cycles. This work introduces a simple and straightforward method for producing ultrathin MXene electrode films tailored for energy storage applications, employing centrifugal-gravity force. Our approach significantly suppresses the oxidation phenomenon that arises in MXene materials and also effectively prevents the recrystallization of potentially residual LiF during the film formation. Additionally, the utilization of this MXene electrode in an all-solid-state microsupercapacitor (MSC) with an interdigitated pattern demonstrates an exceptionally improved and stable electrochemical performance. This includes a high volumetric capacitance of approximately 467 F cm-3, an energy density of around 65 mWh cm-3, and impressive long-term cycle stability, retaining about 94% capacity after 10 000 cycles. Moreover, a downsized MSC device exhibits remarkable mechanical durability, retaining over 98% capacity even when folded and sustaining stability over extended periods. Therefore, we believe that this study provides valuable insights for advancing highly integrated energy storage devices, ensuring exceptional electrochemical efficiency and prolonged functionality in diverse environments, whether ambient or humid.

Hybrid bimetallic phosphonates as cathode materials for miniaturized in-plane asymmetric supercapacitor device

The utilization of wearable electronic devices facilitates the development of smart and flexible technology as a superior energy storage device that minimizes the dimension of wearable devices. The simple vacuum filtration method was employed to fabricate the micro-supercapacitor device (MSC) using the as-synthesized bimetallic nickel cobalt phosphonate (NiCoNPO) on the PVDF membrane as substrate. Novel microporous bimetallic metal phosphonates (NiCoNPO, Ni2CoNPO, NiCo2NPO) have been synthesized in a hydrothermal reaction condition by varying the molar ratio (Ni1:Co1; Ni2:Co1; Ni1:Co2) of metal sources without any employment of templating agent. Among these, NiCoNPO exhibits the remarkable specific capacitance of 2308 F g−1 at 1 mV s−1 and long-term cyclic stability up to the 5000th cycle with 99.6 % capacity retention in the three-electrode system. In addition, the electrode material demonstrates an exceptional capacitance of 574 F g−1 with stability (87.6 % retention) in a two-electrode system. Also, it displays excellent performance as a flexible MSC device with an areal capacitance of 123.5 mF cm−2. Notably, the MSC demonstrates long-term stability up to the 5000th cycle with a capacity retention of 85.6 %, suggesting the electrode material has excellent mechanical flexibility and superior electrochemical performance.

Dual design of electrodes and electrolytes ensures flexible symmetric micro-supercapacitors with high energy density

Benefiting from the dual design of electrodes and electrolytes, a flexible symmetric micro-supercapacitor device has been assembled to achieve a high areal energy density.

Phosphorus-Doped Nickel Oxide Micro-Supercapacitor: Unleashing the Power of Energy Storage for Miniaturized Electronic Devices.

For an uninterrupted self-powered network, the requirement of miniaturized energy storage device is of utmost importance. This study explores the potential utilization of phosphorus-doped nickel oxide (P-NiO) to design highly efficient durable micro-supercapacitors. The introduction of P as a dopant serves to enhance the electrical conductivity of bare NiO, leading to 11-fold augmentation in volumetric capacitance to 841.92 Fcm-3 followed by significant enhancement of energy and power density from 6.71 to 42.096 mWhcm-3 and 0.47 to 1.046 Wcm-3, respectively. Theoretical calculations used to determine the adsorption energy of OH- ions, revealing higher in case of bare NiO (1.52eV) as compared to phosphorus-doped NiO (0.64eV) leading to high electrochemical energy storage performance. The as-designed micro-supercapacitor (MSC) device demonstrates a facile integration with the photovoltaic system for renewable energy storage and smooth transfer to external loads for enlightening the blue LED for ≈1min. The choice of P-NiO/Ni not only contributes to cost reduction but also ensures minimal lattice mismatch at the interface facilitating high durability up to 15 K cycles along with capacitive retention of ≈100% and coulombic efficiency of 93%. Thus, the heterostructure unveils the possibilities of exploring miniaturized energy storage devices for portable electronics.

Fabrication of Flexible Films for Supercapacitors Using Halloysite Nano-Clay Incorporated Poly(lactic acid).

In the past few years, significant research efforts have been directed toward improving the electrochemical capabilities of supercapacitors by advancing electrode materials. The present work signifies the development of poly(lactic acid)/alloysite nano-clay as an electrode material for supercapacitors. Physico-chemical characterizations were analyzed by Fourier transform infrared spectroscopy, wide-angle X-ray diffraction, and a universal testing machine. Cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic charge-discharge techniques were employed to evaluate electrochemical characteristics. The optimized poly(lactic acid)/halloysite nano-clay film revealed the highest specific capacitance of 205.5 F g-1 at 0.05 A g-1 current density and showed 14.6 Wh kg-1 energy density at 72 W kg-1 power density. Capacitance retention of 98.48% was achieved after 1000 cycles. The microsupercapacitor device presented a specific capacitance of 197.7 mF g-1 at a current density of 0.45 mA g-1 with 10.8 mWh kg-1 energy density at 549 mW kg-1 power density.

Development of novel PVA-TEOS-MnO2 and its PANI incorporated flexible membrane electrodes and evaluation of their supercapacitor performance

The properties of tetraethyl orthosilicate (TEOS) crosslinked poly (vinyl alcohol) (PVA) membranes were altered by introducing MnO2 nanoparticles through the chemical oxidation of KMnO4. The resulting PVA-TEOS-MnO2-4 membrane was modified by in-situ polymerization of aniline monomer in the membrane matrix, and obtained the PVA-TEOS-MnO2-PANI nanocomposite flexible membrane electrode. After performing the physicochemical studies, the flexible membrane electrodes were subjected to cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy. The PVA-TEOS-MnO2-PANI electrode membrane exhibited specific capacitance as high as 550.23 F g−1 at a current density of 0.1 A g−1. The specific capacitance and energy density of PVA-TEOS-MnO2-PANI were found to be higher than PVA-TEOS-MnO2-4 and its cycle-life stability was retained more than 90 % of its initial capacitance even after 1000 cycles. Based on the results, it is concluded that the PVA-TEOS-MnO2-PANI nanocomposite flexible membrane electrode could be a potential candidate for the development of flexible supercapacitor devices on large-scale applications. We further fabricated a micro-supercapacitor device and measured its specific capacitance, energy density and power density at a current density of 5.0 mA g−1, and were respectively found to be 59 F g−1, 7.42 Wh kg−1, and 65.89 W kg−1. In addition, the process of fabrication used in this study offers a simple method for the mass production of flexible and light-weight micro-supercapacitor devices.

Novel microporous manganese phosphonate-derived metal oxides as prospective cathode materials for superior flexible asymmetric micro-supercapacitor device

Developing high-power supercapacitors is tremendously relevant to the current energy demand and implementation of renewable energy storage. The template-free microporous organic-inorganic hybrid material manganese phosphonate (MnPIm) and their derivatives heteroatom doped manganese oxides (NP/MnO2500, NP/MnO2700, NP/MnO2900) are synthesized under hydrothermal condition and following the pyrolysis at different temperatures. Due to heteroatoms doped on material, a significant synergistic effect enhances the electrochemical performance in supercapacitor applications. The unique globular morphology with a hollow structure of materials possesses a high surface area, leading to extraordinary specific capacitance. Among these, NP/MnO2700 electrode material displays the superior specific capacitance value of 1362 F g−1 at 1 mV s−1 in three-electrode assembly with 99.6 % retention of its initial capacitance up to the 2000th cycle. It demonstrates the exceptional specific capacitance of 263 F g−1 in two electrode asymmetric device with an energy density of 72.6 Wh kg−1 at the power density of 1306 W kg−1. The NP/MnO2700 material is used to fabricate a flexible asymmetric micro-supercapacitor device (MSC) with an areal capacitance of 32.8 mF cm−2. The energy density of MSC is estimated to be 18.2 μWh cm−2 at the power density value of 65.6 μW cm−2 with 84.2 % retention up to the 5000th cycle.

Tailoring ion dynamics in energy storage conductors for ultra-stable, high-performance solid-state microsupercapacitor array

All-solid-state electrochemical energy storage (EES) devices with prolonged lifetime, operational stability, and mechanical flexibility can be a promising route to powering up wearable electronics. However, conventional EES devices have been often hindered by a gradual decrease in energy capacity due to low ionic conducting electrolytes, non-suitable electrode materials, or poor electrode/electrolyte interfaces. Herein, we propose a harmonization of the molecular-level tailoring of ionic gel polymer electrolyte (IGPE) and graphene-based electrodes, significantly improving and sustaining the electrochemical performance (11.9 μWh cm−2) of EES microsupercapacitor (MSC) devices. Our optimized MSC device based on ethyl-3-methylimidazolium bis(fluorosulfonyl)imide (EMIM-FSI) and interdigitated reduced-graphene oxide (rGO) electrode array maintains 99 % of the initial electrochemical capacity even after 20,000 cycles, also demonstrating the excellent mechanical flexibility (bending radius up to 4 mm) and environmental stability (>30 days) of the MSC-based array. Molecular-level simulation and spectroscopic atomic analysis revealed noticeably lower residual ionic liquid (IL) molecules of EMIM-FSI, compared to EMIM-trifluoromethyl FSI, between the graphene-based layers of electrodes during the charge/discharge cycles. Therefore, our optimization strategy and findings will pave the way to accomplish next-generation of all-solid-state EES devices with ultra-high operational stability, powering wearable electronics.

PEDOT:PSS/regenerated cellulose composite microelectrode for high-performance micro-supercapacitor

Ecofriendly electronic and energy storage devices are critical for addressing the issues regarding the limited energy resources and environmental pollution. Conductive micropatterns on biodegradable substrates are key components for the development of green energy storage devices. In this study, we report a facile strategy for constructing highly conductive and flexible poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) micropatterns on regenerated cellulose (RC) substrates via a simple vacuum-assisted filtration with a 3D printed shadow mask and dimethyl sulfoxide (DMSO) post-treatment. Theshadow maskwas effectively used in a vacuum filtration process to create various PEDOT:PSS micropatterns on RC substrates (PEDOT:PSS/RCs). The RC substrates present the advantages of being both synthetic and natural polymers such as high uniformity, good solution-processability, mechanical property, and biodegradability. The PEDOT:PSS patterns on the RC substrates show a sheet resistance of 4.2 Ω/cm2, an electrical conductivity of 327 S/cm, good adhesion stability and excellent bending durability. Furthermore, the PEDOT:PSS micropatterns on the RC substrates were successfully used for fabricating a solid-state micro-supercapacitor (MSC) device. The MSC sandwich structure based on PEDOT:PSS/RCs has a good specific capacitance of 65.55 mF/cm2 and an excellent cycling stability over 4000 cycles.

Stable carbon encapsulated titanium carbide MXene aqueous ink for fabricating high-performance supercapacitors

• A simple method to synthesize phenolic carbon encapsulated Ti 3 C 2 T x (Ti 3 C 2 T x @C) inks • Ti 3 C 2 T x @C exhibited superior oxidation resistance even after 100 days of aging • Ti 3 C 2 T x @C exhibited a specific capacitance of 736 F g –1 in a three-electrode system • A flexible interdigitated micro supercapacitor (MSC) was printed using Ti 3 C 2 T x @C inks • Ti 3 C 2 T x @C MSC device displayed high cycling stability (83% after 10,000 cycles) Ti-based MXenes have shown great promise in electrochemical applications, including (photo)electrocatalysis and energy storage. However, their practical application has been hindered by their rapid oxidation in the presence of water and O 2 . In this work, we propose a method to solve the problem through a one-step hydrothermal treatment of MXene (Ti 3 C 2 T x , where T x is –OH or –F) in the presence of agarose. The hydrothermal treatment results in the in situ capping of the phenolic carbon layer on the Ti 3 C 2 T x to form Ti 3 C 2 T x @C, which improves its chemical stability by protecting the Ti atoms from oxidation with water and O 2 , and thus enhances its electrochemical performance by avoiding re-stacking of the Ti 3 C 2 T x @C sheets. The as-prepared Ti 3 C 2 T x @C exhibits high oxidation resistance with >95% performance when stored in an aqueous medium for at least 100 days. Ti 3 C 2 T x @C provides a specific capacitance of 736 F g –1 in 1 M H 2 SO 4 electrolyte over a voltage window of 0.5 V. Having excellent water dispersibility and high electrochemical activity, Ti 3 C 2 T x @C is ideal for the preparation of stable MXene inks for the fabrication of high-performance interdigitated electrodes through inkjet printing. The flexible micro-supercapacitor constructed from Ti 3 C 2 T x @C ink exhibits excellent cyclic stability up to 10,000 charge-discharge cycles without a significant decrease in specific capacitance.

Tuning the Laser‐Induced Processing of 3D Porous Graphenic Nanostructures by Boron‐Doped Diamond Particles for Flexible Microsupercapacitors

AbstractCarbon (sp3)‐on‐carbon (sp2) materials have the potential to revolutionize fields such as energy storage and microelectronics. However, the rational engineering and printing of carbon‐on‐carbon materials on flexible substrates remains a challenge in wearable electronics technology. This study demonstrates the scalable fabrication of flexible laser‐induced graphene (LIG)‐boron doped diamond nanowall (BDNW) hybrid nanostructures for microsupercapacitors. Direct laser writing on polyimide film is tuned by the presence of BDNW powder where an appreciable absorbance of the BDNWs at the CO2 laser wavelength enhances the local film temperature. The thermal shock due to laser irradiation produces graphitized and amorphous carbon at the diamond grain boundaries which increases the thermal and charge transfer capacity between the LIG–diamond interfaces. The samples are further treated with O2 plasma to tune the wettability or to improve the microsupercapacitor device performance. The outstanding electrical characteristics of graphene, exceptional electrochemical stability of diamond, and essential contributions of oxygen‐containing groups result in a remarkable charge storage capacity (18 mF cm−2 @ 10 mV s−1) and cyclic stability (98% retention after 10 000 cycles) outperforming most state‐of‐the‐art LIG‐based supercapacitors. Furthermore, despite extreme mechanical stress, these microsupercapacitors maintain their outstanding electrochemical properties, thus holding promise for high‐power, flexible/wearable electronics.

All-3D-printed solid-state microsupercapacitors

Recently, miniaturized electrochemical energy storage units have gained tremendous attention in the fields of microelectronic electronics systems, with the advent of the era of “internet of things”. Shape configurable energy storage devices can be implemented on arbitrarily designable electronics system through 3D printing on the designated surfaces of device systems. In this study, we have developed a methodology of fabricating an all-3D-printed solid-state energy storage device by sequentially printing 3D-printable highly viscous fluids for metallic current collector, electrode and electrolyte layers. The Ni metallic current collector that can be operated stably at a high voltage condition of 3 V, is formed by a combinatorial approach of using 3D printing and 3D laser sintering processes. An intact physical interaction is interpreted comprehensively for the particles residing inside the printed particulate layer and the photons irradiated from a green laser source, based on an in-depth comparative investigation of experimental data and electromagnetic simulation result. A graphene nanoplatelet-based electrode fluid and an ionic liquid-based UV curable electrolyte fluid are printed successively on top of 3D-structured current collectors. It is demonstrated that the all-3D-printed microsupercapacitor device delivers the energy density and power density of 25.4 to 8.5 μWh•cm−2 and 150 to 6,483 μW•cm−2, respectively, even approaching the state-of-the-art level for flat-type conventional devices.

In-Plane Flexible Microsystems Integrated with High-Performance Microsupercapacitors and Photodetectors

The rapid development of wearable and portable electronics has resulted in an urgent desire for lightweight, flexible microsystems integrated with energy storage devices and other in-plane devices. An approach is proposed herein to develop an in-plane flexible microsystem on graphite paper containing an all-solid-state microsupercapacitor and a photoconductor-type photodetector based on perovskite film, where a simple, low-cost, and scalable strategy involving laser etching, electrochemical exfoliation, and electrochemical deposition can be used to fabricate the all-solid-state microsupercapacitor. The as-fabricated microsupercapacitor device exhibits high capacitance and reliable stability under testing through 100,000 cycles of dynamic bending. In the integrated microsystem, the microsupercapacitor is used to drive the photoconductive detector. It turns out that the designed integrated system exhibits a stable photocurrent response comparable to a detector driven by an external power source. This work paves the way for the fabrication of integrated microsystems where sensor systems are driven by integrated energy storage devices, applicable to future wearable and portable electronics.

Development of Waste Red-Mud Nanoparticle Decorated Laser-Induced Graphene Flexible Sueprcapacitor

Environmental benign, inexpensive, flexible, smart energy storage micro-supercapacitors, with high energy and power densities and long-term cyclic stability are appealing for next generation energy storage devices. Conventionally, highly conducting carbon-based nanomaterials with high-surface areas are extensively used as supercapacitor electrode and the introduction of metal oxides (or conducting polymers) induces pseudocapacitance and can further enhances the specific capacitance and energy density. Red mud (RM), an aluminum industry waste by-product which is a rich source of hematite phase Fe2O3. RM is environmentally hazardous due to its alkalinity and is produced at an annual rate of ~ 110 million tonnes each year, much of which is not well utilized, and left to lie in large lakes; thus, methods of finding value-added applications for RM are well sought after. In this study, we used mechanical milling to produce uniform spherical RM nanoparticles and utilized these in a flexible micro-supercapacitor device. The as-synthesized nanoparticles were decorated over a laser induced porous 3D graphene (LIG) on a polyimide substrate. The composite electrode material was characterized using transmission electron microscopy (TEM), field effect scanning electron microscopy (FESEM), X-ray photo electron spectroscopy (XPS), Raman spectroscopy and cyclic voltammetry (CV). A solid-state ionic liquid based polymer gel electrolyte was produced using a mixture of ionic liquids {[EMI][TFSI] and [EMIM][BF4]} and a PVDF polymer. Inkjet printing technique was employed to produce the silver current collector and the as fabricated inter-digitated micro-supercapacitor device (Figure 1a) exhibited an areal capacitance of 203 mF cm-2 with a higher potential window of 2.7 V, high energy density of 0.018 mW h/cm2 at 0.66 mW/ cm2 power density. RM decoration increased the energy density of the device by 3.7 fold compared with pristine LIG device (Figure 1b). Rapid lateral ion flow in the planar architecture, presence of metal oxides (mostly hematite), higher electrochemically active surface area, better charge transfer kinetics were shown to yield improvements in the energy-density and the electrochemical performance of the device. An in-depth electrochemical study also revealed that the charge storage mechanism was governed by diffusion driven pseudocapacitance. The device exhibited good robustness and could resist bending and flexing and the prototype device exhibited to power a white-light LED (Figure 1c). Overall, this work demonstrates that RM may be used as a low-cost pseudocapacitive element in supercapacitor electrodes and aid in reducing the environmental impact of the aluminium production cycle by recycling this abundant waste product. Figure 1

Atomic layer deposition of titanium oxide and nitride on vertically aligned carbon nanotubes for energy dense 3D microsupercapacitors

This work demonstrates the use of ALD coatings in a full-cell 3D microsupercapacitor (MSC) device for the first time. The novel device design described herein has potential to be exploited for rapid and scalable manufacturing of on-chip MSCs integrated with other electronic devices in standard semiconductor fabs or foundries. In this study, atomic layer deposition (ALD) was used to deposit conformal pseudocapacitive coatings of titanium oxide (TiO2) and titanium nitride (TiN) onto CVD-grown vertically aligned carbon nanotubes (VACNTs) to increase the area-specific capacitance (by 240× and 74× at 0.1 Vs−1 versus the as-deposited VACNT electrode and full-cell VACNT device, respectively) and thus energy density for microscale energy storage applications. The study indicated that combining TiO2 and TiN ALD layers resulted in a multilayered composite coating rich in oxygen vacancies with enhanced capacitance relative to a single TiO2 or TiN layer due to a dynamic surface chemistry that developed during charge-discharge cycling. A key component of this multilayered coating was the formation of titanium oxynitride (TiON) which we attributed to the improved performance. Further, we demonstrated that controlling the thickness and stoichiometric ratio of the TiN-TiO2 composite coating was key to enabling functionality and optimizing the symmetric 3D MSC device performance.

Self-assembly of graphene-based planar micro-supercapacitor with selective laser etching-induced superhydrophobic/superhydrophilic pattern

Facile production of graphene-based in-plane interdigital electrode is critical for microscale supercapacitors but remains a great challenge (time consuming, expensive equipment needed, etc). The preparation of fine interdigital electrode planar micro-supercapacitors (MSCs) by selective laser etching of ceramic substrate is proposed, which provides an alternative method for rapid fabrication of planar MSCs. The formation of self-assembled electrode of graphene ink via the laser etching-induced heterogeneous surface wettability was firstly investigated, and then an all-solid-state MSCs microdevice was obtained by adding a polyvinyl alcohol–sulfuric acid gel electrolyte to the interdigital electrode region. The results of cyclic voltammetry test showed that the micro-supercapacitor device could offer an area capacitance of 5.5 mF cm−2 at a potential scan rate of 5 mV s−1 and the capacitance retention of 88.5% after 4500 cycles.

Nanoporous gold–Nitrogen–doped carbon nano-onions all-solid-state micro-supercapacitor

The faster growth of the microelectronics industry and consumer’s demand for tiny, portable electronic devices increases the necessity of micro-scale energy storage units. Micro-supercapacitors have potential to support tiny micro-electronic devices by replacing or complimenting batteries and electrolytic capacitors. Nanoporous gold (NPG)–Nitrogen doped carbon nano-onions (NCNO) based micro-supercapacitor is an attempt to develop an energy storage unit that is compatible with microelectronic devices. A simple two-step process of thermal evaporation followed by dealloying and electrophoretic deposition were used for NPG growth and NPG–NCNO electrode preparation. The process is economical and easily scalable Nanoporous gold (NPG) is an attractive material for current collector due to its three-dimensional interconnected pores with high electrical conductivity and high surface area for NCNO loading. NPG–NCNO micro-supercapacitor device shows an areal capacitance 1.16 mF cm−2. The maximum energy density and power density obtained from NPG–NCNO micro-supercapacitor were 0.16 μWh cm−2 and 24.87 μW cm−2 at the scan rate of 10 mVs−1 and 200 mVs−1 respectively.

Capacitive properties of novel N-alkyl substituted poly(3,6-dithienyl-9H-carbazole)s as redox electrode materials and their symmetric micro-supercapacitor applications

Herein, we present a comparative study about charge storage performances of novel N-alkyl substituted poly(3,6-dithienylcarbazole)-based electrodes for supercapacitor applications. The poly(3,6-dithienylcarbazole) derivatives, poly(9-butyl-3,6-di(thien-2-yl)-9H-carbazole) (PTCB), poly(9-hexyl-3,6-di(thien-2-yl)-9H-carbazole) (PTCH) and poly(9-octyl-3,6-di(thien-2-yl)-9H-carbazole) (PTCO), were electrochemically synthesized for the first time on a metal substrate and directly used as electrode materials in supercapacitor applications. The capacitive performances of PTCB, PTCH and PTCO polymeric films were studied by using cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance spectroscopy techniques in both three-electrode and real two-electrode micro-supercapacitor device configurations. PTCB, PTCH and PTCO redox-active materials achieved high gravimetric specific capacitances of 147.7, 218.7 and 509.8 F g−1, respectively, at a current density of 2.5 mA cm−2 in three-electrode cell configurations. Assembled symmetric devices reached maximum specific capacitances of 70.4 (for PTCB), 96 (for PTCH) and 185.5 F g−1 (for PTCO). Devices also delivered energy densities of 20.3, 26 and 55 W h kg-1 and power densities of 750, 755 and 760 W kg−1 with good rate capabilities. Moreover, micro-supercapacitor devices exhibited good long-term cycling stability performances and retained 83.7%, 86.5% and 89.4% of their initial capacitances after 10 000 charge/discharge cycles. The electrochemical performance tests reveal that PTCB, PTCH and PTCO redox-active materials have promising potential to meet requirements of a practical electrochemical energy storage applications.