Electrodes For Micro-supercapacitors Research Articles

Tuning Deposition Conditions for VN Thin Films Electrodes for Microsupercapacitors: Influence of the Thickness

Vanadium nitride is a highly promising material for micro-pseudocapacitors when used as a bifunctional thin film, i.e. an electrode material and a current collector, owing to its remarkable electrical and electrochemical properties. However, the specific limitations associated with high-rate cycling remain unclear. In this study, we evaluate how the characteristic time associated with charge/discharge of vanadium nitride films is modified with the film thicknesses using electrochemical impedance spectroscopy and cyclic voltammetry measurements coupled to a semi-empirical model commonly utilized to assess the high-rate behaviour of battery electrodes. Both methodologies are in good agreement and revealed that rate capability of this bi-functional material is limited by the VN electrical conductivity. To confirm this finding, VN thin films were sputtered on platinum current collectors, leading to a six-fold reduction in the characteristic time associated with charge/discharge of the current collectors/electrode material. This underscores the importance of using current collectors even for highly conductive electrode materials.

Highly Nanoporous Nickel Foam as Current Collectors in 3D All-Solid-State Microsupercapacitors.

This study reports a streamlined method for producing a highly nanoporous current collector with a substantial specific surface area, serving as an electrode for microsupercapacitors (MSCs). Initially, commercial Ni foams are patterned into an interdigitated structure by laser cutting. Subsequently, the Ni foams are infused with NiO nanopowders through dip coating, sintering, and reduction in an H2 atmosphere, followed by the growth of MnO2 through a redox reaction. The incorporation of NiO within this three-dimensional Ni current collector results in notable porosity within the range of approximately 200-600 nm. Such a 3D, highly nanoporous electrode dramatically increases the specific surface area by 30 times and substantially boosts the amount of active material deposition, surpassing those of commercially available Ni foams. Performance evaluations of this highly nanoporous electrode in a 1 M KOH solution demonstrate an areal capacity of 19.3 F/cm2, retaining more than 95% capacitance at 5 mA/cm2, and exhibiting an energy density of 671 μW h/cm2, 25 times greater than commercial Ni foams. Moreover, in the realm of solid-state applications for MSCs, the remarkably high porous electrode achieves a commendable areal capacity of 7.22 F/cm2 and an energy density of 263.9 μW h/cm2, rendering it exceptionally suitable for use in MSC applications.

Ultra-Wide Interlayered WxMo2xSy Alloy Electrode Patterning through High-Precision Controllable Photonic-Synthesis.

Ultra-thin 2D materials have great potential as electrodes for micro-supercapacitors (MSCs) because of their facile ion transport channels. Here, a high-precision controllable photonic-synthesis strategy that provided 1inch wafer-scale ultra-thin film arrays of alloyed WxMo2xSy with sulfur vacancies and expanded interlayer (13.2Å, twice of 2H MoS2) is reported. This strategy regulates the nucleation and growth of transition metal dichalcogenides (TMDs) on the picosecond or even femtosecond scale, which induces Mo-W alloying, interlayer expansion, and sulfur loss. Therefore, the diffusion barrier of WxMo2xSy is reduced, with charge transfer and ion diffusion enhancing. The as-prepared symmetric MSCs with the size of 100×100µm2 achieve ultrahigh specific capacitance (242.57mFcm-2 and 242567.83Fcm-3), and energy density (21.56Whcm-3 with power density of 485.13Wcm3). The established synthesis strategy fits numerous materials, which provides a universal method for the flexible synthesis of electrodes in microenergy devices.

Unlocking Maximum Synergy: Screen-Printing Fabrication of Heterostructured Microsupercapacitor Stacks.

A cost-effective and scalable approach for the fabrication of heterostructured microsupercapacitors (MSCs) employing screen-printing followed by sequential electrochemical and microspray deposition techniques has been demonstrated. The microsupercapacitor electrode (MSC) that composed of stacked layers of mesoporous carbon, polyaniline (PANI), and MXene hold significant promise for wearable electronics. By adjusting the deposition and spray cycles, the MSC can be readily coated with PANI and MXene. The sequentially stacked two layers of MXene and PANI on the mesoporous carbon spheres (PMPM-MSC) yielded a specific capacitance of 1003 mF cm-2 at 0.5mA cm-2, surpassing the performance of PANI/mesoporous carbon electrode by 1.6 times (771 mF cm-2). After 10,000 cycles of charge and discharge, PMPM-MSCs retained more than 86% of their initial capacitance. In-situ Raman spectroscopy confirmedthe synergistic effects between MXene and PANI within the heterostructured stacked PMPM-MSC electrodes, including enhanced electronic conductivity and improved electrolyte ion dissociation, which aligned with the electrochemical measurement results, such as fast charge/discharge rates and reduced internal and mass transport resistance. This study demonstrates the potential of screen-printed heterostructured MSC stacks with maximum electrochemical synergy for portable and wearable energy storage devices.

Metal telluride nanosheets by scalable solid lithiation and exfoliation.

Transition metal tellurides (TMTs) have been ideal materials for exploring exotic properties in condensed-matter physics, chemistry and materials science1-3. Although TMT nanosheets have been produced by top-down exfoliation, their scale is below the gram level and requires a long processing time, restricting their effective application from laboratory to market4-8. We report the fast and scalable synthesis of a wide variety of MTe2 (M = Nb, Mo, W, Ta, Ti) nanosheets by the solid lithiation of bulk MTe2 within 10 min and their subsequent hydrolysis within seconds. Using NbTe2 as a representative, we produced more than a hundred grams (108 g) of NbTe2 nanosheets with 3.2 nm mean thickness, 6.2 µm mean lateral size and a high yield (>80%). Several interesting quantum phenomena, such as quantum oscillations and giant magnetoresistance, were observed that are generally restricted to highly crystalline MTe2 nanosheets. The TMT nanosheets also perform well as electrocatalysts for lithium-oxygen batteries and electrodes for microsupercapacitors (MSCs). Moreover, this synthesis method is efficient for preparing alloyed telluride, selenide and sulfide nanosheets. Our work opens new opportunities for the universal and scalable synthesis of TMT nanosheets for exploring new quantum phenomena, potential applications and commercialization.

The production of electrodes for microsupercapacitors based on MoS2-modified reduced graphene aerogels by 3D printing

Micro-supercapacitors (MSCs) are of interest because of their high power density and excellent cycling performance, offering a broad array of potential applications. However, preparing electrodes for the MSCs with an extremely high areal capacitance and energy density remains a challenge. We constructed MSC electrodes with an ultra-high area capacitance and a high energy density, using reduced graphene oxide aerogel (GA) and MoS2 as the active materials, combined with 3D printing and surface modification. Using 3D printing, we obtained electrodes with a stable macrostructure and a GA-crosslinked micropore structure. We also used a solution method to load the surface of the printed electrode with molybdenum disulfide nanosheets, further improving the electrochemical performance. The surface capacitance of the electrode reached 3.99 F cm−2, the power density was 194 W cm−2, and the energy density was 1 997 mWh cm−2, confirming its excellent electrochemical performance and cycling stability. This work provides a simple and efficient method for preparing MSC electrodes with a high areal capacitance and energy density, making them ideal for portable electronic devices.

Laser-machined micro-supercapacitors: from microstructure engineering to smart integrated systems.

With the rapid development of portable and wearable electronic devices, there is an increasing demand for miniaturized and lightweight energy storage devices. Micro-supercapacitors (MSCs), as a kind of energy storage device with high power density, a fast charge/discharge rate, and a long service life, have attracted wide attention in the field of energy storage in recent years. The performance of MSCs is mainly related to the electrodes, so there is a need to explore more efficient methods to prepare electrodes for MSCs. The process is cumbersome and time-consuming using traditional fabrication methods, and the development of laser micro-nano technology provides an efficient, high-precision, low-cost, and convenient method for fabricating supercapacitor electrodes, which can achieve finer mask-less nanofabrication. This work reviews the basics of laser fabrication of MSCs, including the laser system, the structure of MSCs, and the performance evaluation of MSCs. The application of laser micro-nanofabrication technology to MSCs and the integration of MSCs are analyzed. Finally, the challenges and prospects for the development of laser micro-nano technology for manufacturing supercapacitors are summarized.

Untethered Magnetic Soft Robot with Ultra-Flexible Wirelessly Rechargeable Micro-Supercapacitor as an Onboard Power Source.

Soft robotics has developed rapidly in recent years as an emergent research topic, offering new avenues for various industrial and biomedical settings. Despite these advancements, its applicability is limited to locomotion and actuation due to the lack of an adequate charge storage system that can support the robot's sensory system in challenging conditions. Herein, an ultra-flexible, lightweight (≈50 milligrams), and wirelessly rechargeable micro-supercapacitor as an onboard power source for miniaturized soft robots, capable of powering a range of sensory is proposed. The simple and scalable direct laser combustion technique is utilized to fabricate the robust graphene-like carbon micro-supercapacitor (GLC-MSC) electrode. The GLC-MSC demonstrates superior areal capacitance (8.76mFcm-2 ), and maintains its original capacitance even under extreme actuation frequency (1-30Hz). As proof of conceptthe authors fabricate a fully integrated magnetic-soft robotthat shows outstanding locomotion aptitude and charged wirelessly (up to 2.4V within 25s), making it an ideal onboard power source for soft robotics.

Graphene/SiC composite porous electrodes for high-performance micro-supercapacitors

Micro-supercapacitor (MSC) electrodes prepared by chemical vapor deposition (CVD) possess high potential as on-chip integrated micro-power sources for future microdevices. In this study, porous graphene/SiC composite films are grown using laser CVD. A double-layer specific capacitance up to 219.3 mF/cm2 is achieved at 10 mV/s, which is 26 times higher than those of the electrodes prepared by CVD with the same energy storage mechanism reported in literatures. After 20000 charge-discharge cycles at room temperature (20 °C) and variable temperatures (0–60 °C), the electrode exhibits robust cycling stability with 99.9% and 109.6% capacitance retention, respectively. Subsequently, it is revealed that the abundance of graphene on the SiC porous skeleton plays a key role in promoting the capacitance enhancement. The strong structure of SiC as well as the strong adhesion between graphene and SiC guarantee the excellent cycling stability. Evidently, the preparation of graphene/SiC porous composite films as MSC electrodes is a highly promising route for fabricating high-performance and reliable on-chip power sources for future miniaturized devices.

Laser direct synthesis of Co/CoO modified graphene for high-performance microsupercapacitors

Graphene/CoO nanocomposites have excellent electrochemical performance and are extensively applied to microsupercapacitors (MSCs). Herein, we propose a simple and efficient method for laser direct writing on a graphene oxide/Co(CH3COO)2 precursor to process graphene/Co/CoO nanocomposite interdigital electrodes for MSCs. This work investigates the structural defects, crystal structure, sheet resistance, elemental composition, and bond characteristics of graphene/Co/CoO nanocomposites synthesized at different laser writing speeds. The specific capacitance, power density, and energy density of the prepared MSC based on PVA/H3PO4 electrolyte and graphene/Co/CoO interdigital electrodes reach 420.23 mF cm−2 (48.31 F cm−3), 1.97 mW cm−2 (226.43 mW cm−3), and 58.37 μWh cm−2 (6.71 mWh cm−3), respectively. Moreover, the Coulombic efficiency and capacitance retention rate of the prepared MSC after 10,000 cycles are 97.97% and 86.56%, respectively. The charge storage of the prepared MSC is mainly achieved through diffusion-controlled intercalation reactions. In addition, the prepared MSC shows good mechanical flexibility.

Self-assembled ultrathin carbon black/carbon nanotube films as electrodes for microsupercapacitors

Self-assembled ultrathin carbon black/carbon nanotube films as electrodes for microsupercapacitors

Laser-induced graphene electrodes scribed onto novel carbon black-doped polyethersulfone membranes for flexible high-performance microsupercapacitors

A facile and expandable methodology was successfully developed to fabricate laser-induced graphene from novel pristine aminated polyethersulfone (amPES) membranes. The as-prepared materials were applied as flexible electrodes for microsupercapacitors. The doping of amPES membranes with various weight percentages of carbon black (CB) microparticles was then performed to improve their energy storage performance. The lasing process allowed the formation of sulfur- and nitrogen-codoped graphene electrodes. The effect of electrolyte on the electrochemical performance of as-prepared electrodes was investigated and the specific capacitance was significantly enhanced in 0.5 M HClO4. Remarkably, the highest areal capacitance of 47.3 mF·cm−2 was achieved at a current density of 0.25 mA·cm−2. This capacitance is approximately 12.3 times higher than the average value for commonly used polyimide membranes. Furthermore, the energy and power densities were as high as 9.46 µWh·cm−2 and 0.3 mW·cm−2 at 0.25 mA·cm−2, respectively. The galvanostatic charge–discharge experiments confirmed the excellent performance and stability of amPES membranes during 5,000 cycles, where more than 100% of capacitance retention was achieved and the coulombic efficiency was improved up to 96.67%. Consequently, the fabricated CB-doped PES membranes offer several advantages including low carbon fingerprint, cost-effectiveness, high electrochemical performance and potential applications in wearable electronic systems.

Biomass‐Derived Inks with Tailored Pteridine Derivatives for Sustainable Printed Micro‐Supercapacitors

AbstractUsing biological redox compounds holds great potential in designing sustainable energy storage systems, but it is essential for structure optimization of biological redox centers and in‐depth studies regarding their underlying energy storage mechanisms. Herein, a molecular simplification strategy is proposed to tailor the redox unit of pteridine derivatives, an essential component of ubiquitous electron transfer proteins in nature. The tailored pteridine derivatives can be combined with biomass holey graphene (BHG) to fabricate an ink with a micrometer‐scale resolution for printing flexible electrodes for micro‐supercapacitor (MSCs). The reversible tautomerism of pteridine derivatives from alloxazinic to isoalloxazinic structure is first unveiled in supercapacitors. Through molecular tailoring, printed MSC electrodes using pteridine derivatives/BHG ink demonstrate excellent charge storage, outstanding areal capacitance (95.3 mF cm−2 at 0.1 mA cm−2), energy density (16.3 µWh cm−2), power density (208 µW cm−2), long‐term cycling performance (90.5% retention after 10 000 cycles), easy integration, and exceptional flexibility (maintaining capacitance at various bending states). The non‐covalent interaction of tailored pteridine molecules with redox centers and biomass porous graphene suggests a mature screen‐printing technology for fabricating a sustainable energy storage system with a rational MSC configuration.

Sustainable Approach for the Development of TiO2-Based 3D Electrodes for Microsupercapacitors

This study reports a sustainable approach for developing electrodes for microsupercapacitors. This approach includes the synthesis of TiO2 nanoparticles via a green sol–gel method and the deposition of thin films of that electrochemically active material on three-dimensional (3D) Si substrates with a high area enlargement factor (AEF) via a simple, fast, and inexpensive spin-coating pathway. The thickness of the film was first optimized via its deposition over two-dimensional (2D) substrates to achieve high capacitances to provide high energy density but also to deliver a good rate capability to ensure the power density required for a supercapacitor device. A film thickness of ~120 nm realizes the best compromise between the electronic/ionic conductivity and capacitance in a supercapacitor device. Such layers of TiO2 were successfully coated onto 3D microstructured substrates with different architectures, such as trenches and pillars, and different aspect ratios. The spin-coating-based route developed here has been established to be superior as, on the one hand, a conformal deposition can be achieved over high AEF subtracts, and on the other hand, the 3D electrodes present higher surface capacitances than those obtained using other deposition techniques. The rate capability and appreciable cyclability ensure a reliable supercapacitor behavior.

Direct mask-free fabrication of patterned hierarchical graphene electrode for on-chip micro-supercapacitors

• Functionalized membrane with customized pattern is prepared by fast laser carving. • Selective permeable membrane complemented with vacuum filtration is used to develop intact interdigital thin film. • Macroscopic assembly based on size effect rationally guide the structural design and precise fabrication of flexible electrode with expected high performances. • Flexible high-performance on-chip micro-supercapacitors with planar arbitrary shape are fabricated. Graphene-based electrodes with rational structural design have shown extraordinary prospect for enhanced electrical double-layer capacitance of micro-supercapacitors (MSCs). Herein, a facile fabrication method for flexible planar MSCs based on hierarchical graphene was demonstrated by using a laser-treated membrane for electrode patterning, complemented with hierarchical electrode configuration taking full advantages of size-determined functional graphene. The in-plane interdigital shape of MSCs was defined through vacuum filtration with the assistance of the functionalized polypropylene (PP) membrane. The hierarchical graphene films were built by macroscopic assembly based on size effect of different lateral sized graphene sheets (rGO-LSL). The sample of MSCs based on rGO-LSL (MSCs-LSL) exhibited excellent volumetric capacitance of 6.7 F cm −3 and high energy density of 0.37 mWh cm −3 . The MSCs-LSL presented superb flexibility and cycling stability with no capacitance deteroriated after 2000 cycles. This newly developed fabrication strategy is of good scalability and designability to manufacture flexible electrode for MSCs with customized shapes, while the construction of hierarchical graphene can enlighten the structural design of analogous two-dimensional materials for potential advanced electronics. A facile mask-free filtration approach is developed for the fabrication of patterned onchip micro-supercapacitors based on hierarchical graphene. The use of the functionalized membrane complemented with macroscopic assembly based on size effect provides the control over the planar configuration of micro-supercapacitors, and rationally guide the structural design of flexible electrode with expected high performances.

An efficient cobalt-nickel phosphate positive electrode for high-performance hybrid microsupercapacitors

Flexible energy storage devices play significant role in wearable and portable electronics. Herein, a cobalt-nickel phosphate (CoNiP2O7) composite was synthesized on conductive carbon nanotubes (CNTs) substrate by facile one-step electrochemical deposition method, forming a binder-free CoNiP2O7@CNTs positive electrode for microsupercapacitors (MSCs). Combined with a CNTs substrate on the opposite side of interdigitated electrodes, a CoNiP2O7@CNTs//CNTs hybrid MSC device was assembled. It displayed good electrochemical performance with a largest areal capacitance of 20.9 mF·cm−2 at 0.08 mA·cm−2 and an energy density of 2.9 μWh·cm−2. To construct a self-powered solar cell energy storage system, the proposed MSC device was utilized for energy storage and further provided power for red light-emitting diode (LED), forming natural energy collection-conversion-storage-utilization system. The results of this study offer a simple design route for flexible energy storage devices.

MXene decorated 3D-printed carbon black-based electrodes for solid-state micro-supercapacitors

Three-dimensional (3D) printing offers a unique approach to fabricating free-standing and complex structured electrodes for high-performance micro-supercapacitors (MSCs).

Paper-based laser-induced graphene for sustainable and flexible microsupercapacitor applications

Laser-induced graphene (LIG) is as a promising material for flexible microsupercapacitors (MSCs) due to its simple and cost-effective processing. However, LIG-MSC research and production has been centered on non-sustainable polymeric substrates, such as polyimide. In this work, it is presented a cost-effective, reproducible, and robust approach for the preparation of LIG structures via a one-step laser direct writing on chromatography paper. The developed strategy relies on soaking the paper in a 0.1 M sodium tetraborate solution (borax) prior to the laser processing. Borax acts as a fire-retardant agent, thus allowing the laser processing of sensitive substrates that other way would be easily destroyed under the high-energy beam. LIG on paper exhibiting low sheet resistance (30 Ω sq−1) and improved electrode/electrolyte interface was obtained by the proposed method. When used as microsupercapacitor electrodes, this laser-induced graphene resulted in specific capacitances of 4.6 mF cm−2 (0.015 mA cm−2). Furthermore, the devices exhibit excellent cycling stability (> 10,000 cycles at 0.5 mA cm−2) and good mechanical properties. By connecting the devices in series and parallel, it was also possible to control the voltage and energy delivered by the system. Thus, paper-based LIG-MSC can be used as energy storage devices for flexible, low-cost, and portable electronics. Additionally, due to their flexible design and architecture, they can be easily adapted to other circuits and applications with different power requirements.Graphical

Water Peel-Off Transfer of Electronically Enhanced, Paper-Based Laser-Induced Graphene for Wearable Electronics.

Laser-induced graphene (LIG) has gained preponderance in recent years, as a very attractive material for the fabrication and patterning of graphitic structures and electrodes, for multiple applications in electronics. Typically, polymeric substrates, such as polyimide, have been used as precursor materials, but other organic, more sustainable, and accessible precursor materials have emerged as viable alternatives, including cellulose substrates. However, these substrates have lacked the conductive and chemical properties achieved by conventional LIG precursor substrates and have not been translated into fully flexible, wearable scenarios. In this work, we expand the conductive properties of paper-based LIG, by boosting the graphitization potential of paper, through the introduction of external aromatic moieties and meticulous control of laser fluence. Colored wax printing over the paper substrates introduces aromatic chemical structures, allowing for the synthesis of LIG chemical structures with sheet resistances as low as 5 Ω·sq-1, translating to an apparent conductivity as high as 28.2 S·cm-1. Regarding chemical properties, ID/IG ratios of 0.28 showcase low defect densities of LIG chemical structures and improve on previous reports on paper-based LIG, where sheet resistance has been limited to values around 30 Ω·sq-1, with more defect dense and less crystalline chemical structures. With these improved properties, a simple transfer methodology was developed, based on a water-induced peel-off process that efficiently separates patterned LIG structures from the native paper substrates to conformable, flexible substrates, harnessing the multifunctional capabilities of LIG toward multiple applications in wearable electronics. Proof-of concept electrodes for electrochemical sensors, strain sensors, and in-plane microsupercapacitors were patterned, transferred, and characterized, using paper as a high-value LIG precursor for multiples scenarios in wearable technologies, for improved sustainability and accessibility of such applications.

Ni film decorated on Au-Ag alloy line to enhance graphene/cobalt hydroxide electrodes for micro-supercapacitors

A nanocomposite of graphene, cobalt hydroxide and nickel can conveniently be synthesized on gold-silver alloy lines. Using a two-step electrodeposition method, the scaly morphology is pre-deposited on a Ni film, followed by the interconnecting corrugated graphene/cobalt hydroxide composite nanomaterial. Due to the pre-deposited Ni film, the area capacity of the graphene/cobalt hydroxide/Ni electrode is 1.6-times of the graphene/cobalt hydroxide electrode. The kinetic analysis of the graphene/cobalt hydroxide/Ni electrode displays diffusion and non-diffusion contributions of 38% and 62% at 10 mV s−1, respectively. X-ray photoelectron spectroscopy exhibits the oxidation of Co2+ to Co3+ dedicated to the OH- ion insertion. Furthermore, graphene/cobalt hydroxide/Ni//activated carbon flexible micro-supercapacitor (MSC) was assembled by gel KOH-PVA electrolyte, graphene/cobalt hydroxide/Ni (positive electrode), and activated carbon (negative electrode), which manifests maximum volumetric energy of 18.6 mWh cm−3. Moreover, MSC retains over 94% capacitance after 10,000 cycles. After 1,000 continuous bending/unbending cycles at a 180° bending angle with the frequency of 100 mHz, the capacitance retention of MSC is still maintained at 97% of the initial value. The results show outstanding flexibility and mechanical stability of MSC based on graphene/cobalt hydroxide/Ni electrode and confirm that further chemical and physical optimization may lead to the development of quasi-solid-state hybrid MSCs.