Stretchable Micro-supercapacitors Research Articles

Recent progress of stretchable MXene based micro-supercapacitors

The rapid development of wearable electronics has stimulated the urgent demand for compatible, miniaturized energy storage devices. As one of the most promising candidates, micro-supercapacitors (MSCs) have attracted significant attention, owing to their high power densities, long operation life, and fast charge/discharge rate. In comparison to conventional, rigid MSCs, deformable MSCs are attracting more and more attention for their superior tolerance to various deformations, including stretching, bending, and twisting, guaranteeing smooth operation of the wearable electronics. MXenes, a class of emerging two-dimensional transition metal carbonitrides/nitrides, have metallic conductivity, high specific surface area, good hydrophilicity, and surface chemical tunability, showing great potential as electrode material for MSCs. In this paper, the recent progress, focused on the MXene-based, stretchable MSCs with fiber-shaped, planar configuration, is systematically summarized. Moreover, the key challenges and prospects of MXene-based, stretchable MSCs for practical application are discussed, which are critical for further development of them.

Low‐Temperature Resistant Stretchable Micro‐Supercapacitor Based on 3D Printed Octet‐Truss Design (Small 23/2023)

Micro-Supercapacitors In article number 2207634, Hui Ying Yang and co-workers develop an innovative stretchable micro-supercapacitor with excellent resistance to freezing. Using digital light processing (DLP) 3D printing technology, an interdigital electrode with octet-truss lattice structure has been designed to enhance the electrochemical performance of the micro-supercapacitor. It is anticipated that the proposed design concept will be applicable for next-generation stretchable electronics.

Screen-printed water-based conductive ink on stretchable fabric for wearable micro-supercapacitor

Micro-supercapacitors (MSCs) have received a lot of attention with the rapid development of wearable, highly integrated, and flexible electronics due to their high power density and long cycle life. Among the preparation methods, screen printing is widely used due to its simplicity, low cost, integratability, and ease of industrial production. However, the conductivity, rheology, and printability of the ink are still required to be further optimized in order to improve the resolution and electrochemical properties of the printed patterns. And combining a high energy capacity and wearability of MSCs is also a big challenge. Therefore, a green and environmentally friendly water-based conductive ink is prepared herein to develop a CO-CNT-MnO2-based micro-electrode on stretchable cotton/spandex fabric by screen printing. The CO-CNT-MnO2/F-based MSCs with a forked finger structure are further assembled combined with PVA/LiCl, and high electrochemical performance of the assembled device due to the synergy of double layer capacitance and pseudocapacitor capacitance storage could be achieved as an area capacitance of 8.479 mF/cm2 at 10 mV/s and reach maximum energy density of 0.132 mWh/cm2 at power density of 0.176 mW/cm2. In addition, the assembled MSCs still have high capacitance retention under stretching/folding/bending/friction conditions. This work highlights the great potential of the new water-based conductive ink for the application of stretchable MSCs based on screen printing.

Ultrastretchable MXene Microsupercapacitors.

Stretchable microsupercapacitors represent emerging miniaturized energy-storage devices for next-generation deformable electronics. Two-dimensional (2D) transition metal carbides (MXenes) are considered attractive electrode materials due to theirmetallic conductivity, hydrophilic surfaces, and excellent processability. Here, an ultrastretchable microsupercapacitor of interdigitated MXene microelectrodes with crumpled surface textures is created. The microsupercapacitor shows a series of attractive properties including a high specific capacitance of ≈185 mF cm-2 , ultrahigh stretchability up to 800% area strain, and ≈89.7% retention of the initial capacitance after 1000 stretch-relaxation cycles. In addition to static strains, the microsupercapacitor demonstrates robust mechanical properties to retain stable charging-discharging capability under dynamic stretching at different strain rates. A self-powering circuit system utilizes four microsupercapacitor packs to power a light-emittingdiode(LED) array, which exhibits stable operations under large tensile strain and skin-attached wearable settings. The developments offer a generic design strategy to enhance the deformability of microsupercapacitors based on 2D nanomaterials.

Low-Temperature Resistant Stretchable Micro-Supercapacitor Based on 3D Printed Octet-Truss Design.

Recently, stretchable micro-supercapacitors (MSCs) that can be easily integrated into electronic devices have attracted research and industrial attentions. In this work, three-dimensional (3D) stretchable MSCs with an octet-truss electrode (OTE) design have been demonstrated by a rapid digital light processing (DLP) process. The 3D-printed electrode structure is beneficial for electrode-electrolyte interface formation and consequently increases the number of ions adsorbed on the electrode surface. The designed MSCs can achieve a high capacitance as ≈74.76 mF cm-3 under 1mA cm-3 at room temperature even under a high mechanical deformation, and can achieve 19.53 mF cm-3 under 0.1mA cm-3 at a low temperature (-30°C). Moreover, finite element analysis (FEA) reveals the OTE structure provides 8 times more contact area per unit volume at the electrode-electrolyte interface compared to the traditional interdigital electrode (IDE). This work combines structural design and 3D printing techniques, which provides new insights into highly stretchable MSCs for next-generation electronic devices.

A stretchable, high-voltage and biobased microsupercapacitor using laser induced graphene/MnOx electrodes on cotton cloth

The rapid development of wearable electronics has put forward a great demand for flexible microsupercapacitors (MSCs) that can work normally under extreme deformation, but its green, efficient and pollution-free manufacturing is still a daunting challenge. Here, natural cotton cloth is pre‑carbonized as the precursor and coated with gelatin-mediated manganese (Mn) ion ink for CO2 laser scribing. A biobased laser-induced graphene/manganese oxide (LIG/MnOx) MSC is assembled on a cardboard substrate, showing an areal capacitance of 54.97 mF/cm2 at a current density of 0.05 mA/ cm2 and an areal energy density of 7.63 μWh cm−2 at a power density of 78.93 μW cm−2. These excellent electrochemical performances are attributed to the core-shell structure of LIG/MnOx which provides balanced pseudocapacitance and double-layer capacitance behaviors as well as the stable mechanical properties. Using a simple series-parallel electrode design combined with the kirigami cutting craftwork, a highly stretchable MSC with rated voltage of 60 V is assembled, which can simultaneously light up 20 LEDs for more than 30s during 0– 200% dynamic stretching process, providing a promising power platform for wearable electronics.

Electroactive 1T-MoS2 Fluoroelastomer Ink for Intrinsically Stretchable Solid-State In-Plane Supercapacitors

Full advantage of stretchable electronic devices can be taken when utilizing an intrinsically stretchable power source. High-performance stretchable supercapacitors with a simple structure and solid-state operation are good power sources for stretchable electronics. This study suggests a new type of intrinsically stretchable, printable, electroactive ink consisting of 1T-MoS2 and a fluoroelastomer (FE). The active material (1T-MoS2/FE) is made by fluorinating the metallic-phase MoS2 (1T-MoS2) nanosheets with the FE under high-power ultrasonication. The MoS2 in the 1T-MoS2/FE has unconventional crystal structures in which the stable cubic (1T) and distorted 2H structures were mixed. The printed line of the 1T-MoS2/FE on the porous stretchable Au collector electrodes is intrinsically stretchable at more than ε = 50% and has good specific capacitance (28 mF cm-2 at 0.2 mA cm-2) and energy density (3.15 mWh cm-3). The in-plane all-solid-state stretchable supercapacitor is stretchable at ε = 40% and retains its relative capacity (C/Co) by 80%. This printable device platform potentially opens up the in-plane fabrication of stretchable micro-supercapacitor devices for wearable electronic applications.

Fully stretchable self-charging power unit with micro-supercapacitor and triboelectric nanogenerator based on oxidized single-walled carbon nanotube/polymer electrodes

A key requirement for wearable electronics is an adequate and sustainable power source. Accordingly, a self-powering unit that replaces rechargeable secondary batteries is a promising solution. However, to realize permanent, maintenance-free, and highly durable wearable electronics, stretchable self-powering units that can harvest and store energy should be developed. In this study, we developed a fully stretchable self-charging power unit that integrates a micro-supercapacitor and triboelectric nanogenerator using oxidized single-walled carbon nanotube/polymer electrodes. The fully stretchable micro-supercapacitor with oxidized single-walled carbon nanotube/polyvinylalcohol electrodes exhibited a double layer capacitance of 20 mF cm −2 at 0.1 mA cm −2 and improved mechanical flexibility and stretchability over 10,000 cycles of stretching tests. A stretchable, polydimethylsiloxane-based current collector employing silver nanoparticles embedded with oxidized single-walled carbon nanotubes enabled the fully stretchable, freestanding-triboelectric-layer based nanogenerators to produce a maximum instantaneous power density of 84.4 mW m −2 under periodic and round-trip sliding of a Nylon fabric while stretching up to 40% without significant performance degradation. Furthermore, a micro-supercapacitor of fully stretchable self-charging power unit could be successfully charged by the nanogenerator from 0 to 2.2 V in 1200 s and powered commercial digital clock for approximately 10 s. These results demonstrate that stretchable polymer composites with oxidized single-walled carbon nanotubes are suitable electrodes and active materials for fully stretchable and self-powered wearable electronics. • Ag NPs embedded with Ox-SWCNTs for current collectors of fully stretchable FTENG and MSC. • Intrinsically stretchable Ox-SWCNT/PVA/H 3 PO 4 electrode for fully stretchable MSCs. • Highly durable, fully stretchable self-charging power unit that integrates MSC and FTENG. • Simultaneous energy harvesting and storage functions of the FS-SCPU from repetitive human motion.

Natively stretchable micro-supercapacitors based on a PEDOT:PSS hydrogel

Highly stretchable (>200%) microsupercapacitors (with 93% retention of the capacitance) are prepared by a facile laser-patterning and injection method with a highly conductive PEDOT:PSS hydrogel.

High-energy all-in-one stretchable micro-supercapacitor arrays based on 3D laser-induced graphene foams decorated with mesoporous ZnP nanosheets for self-powered stretchable systems

Micro-supercapacitors are promising energy storage devices that can complement or even replace lithium-ion batteries in wearable and stretchable microelectronics. However, they often possess a relatively low energy density and limited mechanical stretchability. Here, we report an all-in-one planar micro-supercapacitor arrays (MSCAs) based on hybrid electrodes with ultrathin ZnP nanosheets anchored on 3D laser-induced graphene foams (ZnP@LIG) arranged in island-bridge device architecture. The hybrid electrodes with a large specific surface area demonstrate excellent ionic and electrical conductivities, impressive gravimetric (areal) capacitance of 1425 F g −1 (7.125 F cm −2 ) at 1 A g −1 , and long-term stability. In addition to high energy (245 m Wh cm −2 ) and power (12.50 mW kg −1 at 145 m Wh cm −2 ) densities, the MSCAs with excellent cycling stability also showcase adjustable voltage and current outputs through serial and parallel connections of MSC cells in the island-bridge design, which also allows the system to be reversibly stretched up to 100%. Meanwhile, theoretical calculations validated by UV–vis absorption spectra partially suggest that the enhanced capacitance and rate capability may result from the improved electrical conductivity and number of adsorbed charged ions (Na + in Na 2 SO 4 aqueous electrolyte and K + in PVA/KCl gel electrolyte) on the pseudocapacitive non-layered ultrathin ZnP nanosheets. The integration of the all-in-one stretchable MSCAs with a crumpled Au-based triboelectric nanogenerator and stretchable crumpled graphene-based strain sensor demonstrates a self-powered stretchable system. The coupled design principle of electronic materials and device architecture provides a promising method to develop high-performance wearable/stretchable energy storage devices and self-powered stretchable systems for future bio-integrated electronics. • We report hybrid electrodes with ZnP nanosheets anchored on 3D laser-induced graphene foams. • The hybrid electrodes exhibit excellent ionic/electrical conductivities and long-term stability. • The hybrid electrodes with stretchable structures enable stretchable micro-supercapacitor arrays (MSCAs). • The MSCAs with adjustable voltage/current outputs can be reversibly stretched to 100%. • The integration of MSCAs with TENG and sensors demonstrates a self-powered stretchable system.

Robust and durable flexible micro-supercapacitors enabled by graphene nanoscrolls

The rise of miniaturized, flexible and self-powered electronic systems has substantially stimulated the urgent demand for microscale electrochemical energy storage devices. Impressively, planar micro-supercapacitors (MSCs) are playing a crucial role because of fast ion transmission, ultra-long lifetime, and being easily integrated with microelectronic devices. Unfortunately, the robustness of film electrodes in MSCs usually cannot satisfy the structural stability of the film electrodes and the durability of the devices. Here, a novel strategy to address the problem is proposed by introducing graphene nanoscrolls with high aspect ratio as the active materials in the flexible MSCs to enhance the robustness of the film electrode because of their intertwined one-dimensional nanostructures. The as-prepared bendable MSC can maintain nearly 100% of initial capacitance when bent for 1000 cycles, and the stretchable MSC can maintain 88% of initial capacitance when stretched at a high stress ratio of 100% for 1000 cycles. This study provides an effective strategy to build up robust film electrodes for MSCs and improve the durability of the flexible MSCs.

Electrons/ions dual transport channels design: Concurrently tuning interlayer conductivity and space within re-stacked few-layered MXenes film electrodes for high-areal-capacitance stretchable micro-supercapacitor-arrays

Abstract Introduction of interlayer spacers within re-stacked few-layered MXene flakes for more free interlayer space has been proved an effective strategy to improve the acquired electrochemical performance of the assembled film electrodes. However, the expanded interlayer space will inevitably lead to the decrease of interlayer conductivity because of the loose contact between isolated few-layered MXene flakes. The contradiction hinders the maximization of the areal capacitance of the re-stacked few-layered MXene film electrodes. Herein, an “electrons/ions dual transport channels design” is achieved by inserting elaborately synthesized 1D conductive core-shell structured bacterial cellulose (BC)@polypyrrole (PPy) fibers into re-stacked few-layered MXene flakes. This design concurrently realizes the expansion of interlayer space for favoring electrolyte infiltration, and alleviation of interlayer conductivity decline to ensure interlayer electrons transport, as well as additional load of conductive polymer of high specific capacitance and enhancement of interlayer bond strength, endowing the prepared MXene/BC@PPy hybrid film electrodes with fully-excavated areal capacitance of 221.21 mF cm−2 and reinforced tensile strength of 78.9 MPa. Followed a planar electrode configuration design in the MXene/BC@PPy hybrid film electrodes and introduction of islands-bridge interconnecting structure between them, stretchable micro-supercapacitor arrays (MSCAs) of areal capacitance/energy density up to 200.47 mF cm−2/0.01 mWh cm−2 and reversible level of stretchability as much as 200% elongation were further fabricated. The demonstrated “electrons/ions dual transport channels design” provides an attractive and instructive model of structural engineering of few-layered MXenes assembled electrodes for enhanced electrochemical and mechanical performance toward high-areal-capacitance stretchable MSCAs.

A stretchable vertically stacked microsupercapacitor with kirigami-bridged island structure: MnO2/graphene/Poly(3,4-ethylenedioxythiophene) nanocomposite electrode through pen lithography

Although portable and wearable devices have recently attracted considerable attention due to the increasing demands for stretchable power sources, their high fabrication costs as well as lack of mechanical strength and integration capability limit the utilization of these devices. Herein we developed an array of 3 × 3 microsupercapacitors (MSCs) that is mechanically stretchable by attaching MnO2/graphene/poly (3,4-ethylenedioxythiophene)-based nanocomposite on a kirigami-bridged island substrate; the electrodes were simply drawn using pen lithography without following any conventional complicated processing. The structure can dissipate an external stress involved in the deformation of the electrode and delocalize any unwanted excessive strain over the entire interconnected MSCs. The results show that such a stretchable MSC array exhibits an areal specific capacitance of 23.04 mF cm−2 and can be stretched by up to 200% at 3.6 V without showing any degradation in electrochemical performance. In addition, 94% of the initial capacitance is maintained after 5600 times of continuously stretching and releasing these MSCs by the application of a tensile strain. The output voltage and capacitance can be adjusted by using parallel or series arrangements of individual MSCs. Furthermore, these MSCs can be directly applied on the human skin and can maintain their electrochemical performance with repeated body movements.

3D‐Printed Stretchable Micro‐Supercapacitor with Remarkable Areal Performance

AbstractWhile stretchable micro‐supercapacitors (MSCs) have been realized, they have suffered from limited areal electrochemical performance, thus greatly restricting their practical electronic application. Herein, a facile strategy of 3D printing and unidirectional freezing of a pseudoplastic nanocomposite gel composed of Ti3C2Tx MXene nanosheets, manganese dioxide nanowire, silver nanowires, and fullerene to construct intrinsically stretchable MSCs with thick and honeycomb‐like porous interdigitated electrodes is introduced. The unique architecture utilizes thick electrodes and a 3D porous conductive scaffold in conjunction with interacting material properties to achieve higher loading of active materials, larger interfacial area, and faster ion transport for significantly improved areal energy and power density. Moreover, the oriented cellular scaffold with fullerene‐induced slippage cell wall structure prompts the printed electrode to withstand large deformations without breaking or exhibiting obvious performance degradation. When imbued with a polymer gel electrolyte, the 3D‐printed MSC achieves an unprecedented areal capacitance of 216.2 mF cm−2 at a scan rate of 10 mV s−1, and remains stable when stretched up to 50% and after 1000 stretch/release cycles. This intrinsically stretchable MSC also exhibits high rate capability and outstanding areal energy density of 19.2 µWh cm−2 and power density of 58.3 mW cm−2, outperforming all reported stretchable MSCs.

Flexible on-chip micro-supercapacitors: Efficient power units for wearable electronics

To meet the requirements of wearable and portable electronics, flexible and light-weight on-chip micro-supercapacitors (MSCs) have attracted tremendous attention due to the good mechanical and electrochemical performances as well as easy on-chip integration with flexible functional electronic devices. In this review, the recent progresses of flexible on-chip micro-supercapacitors are summarized. Typical strategies toward flexible on-chip MSCs were first discussed, followed with the highlight of multifunctional on-chip MSCs including stretchable MSCs, self-healable MSCs, electrochromic MSCs and thermoreversible self-protection MSCs. Following these parts, wearable electronic systems integrated with flexible on-chip MSCs were discussed in detail. Finally, the challenges and future research emphasis on the flexible on-chip MSCs are put forward.

A Highly Stretchable Microsupercapacitor Using Laser‐Induced Graphene/NiO/Co3O4 Electrodes on a Biodegradable Waterborne Polyurethane Substrate

AbstractConstructing microsupercapacitors (MSCs) with an outstanding stretchability is urgent for wearable electronics, and an intrinsic biodegradability is also meaningful. Herein, laser‐induced graphene/NiO/Co3O4 (NiO/Co3O4/LIG) is in situ synthesized on a polyimide (PI) film during laser processing, then the electrodes are transferred to a biodegradable waterborne polyurethane (WPU) substrate to fabricate stretchable MSCs. Experimentally, the as‐prepared stretchable MSCs exhibit an excellent areal capacitance of 2.4 mF cm−2, high capacitance retention of 77.1% at 50% strain, and capacitance degradation of less than 19.8% after 1000 stretching cycles. These desirable properties are mainly attributed to the gradient structure of NiO/Co3O4/LIG, the synergistic effect of hybrid NiO/Co3O4 nanoparticles, and the intensive interface adhesion between the electrodes and WPU. Interestingly, the robust function of stretchable MSCs is further presented by using them to power a microsensor and assembling them with triboelectric nanogenerators to generate power from mechanical contact with skin, which makes the stretchable MSCs promising as a sustainable driving source for wearable electronics.

A Fractal-designed stretchable and transparent microsupercapacitor as a Skin-attachable energy storage device

We report on the fabrication of a fractal-designed transparent and stretchable (TS) microsupercapacitor (MSC) as a skin-attachable energy storage device for driving an integrated strain sensor (SS). The MSC is designed to have a fractal structure with long and narrow patterns to ensure high transparency and stretchability. MnO2/Carbon nanotubes (CNTs) and 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide/poly(methyl methacrylate) ([BMIM][TFSI]/PMMA) are used as electrodes and a stretchable electrolyte for the MSC, respectively. The fabricated MSC exhibits high transparency of 79% and an areal capacitance of 12.6 mF cm−2 at a current density of 5 mA cm−2. The TS MSC shows excellent mechanical stability in that it can maintain stable electrochemical performance even after 2000 repeated stretching cycles up to 30%. The TS SS is facilely prepared via spray coating of Ag nanowires (NWs) and subsequent curing of PDMS, where the transparency and the electrical resistance are controlled by adjusting the deposited volume of Ag NWs. Wrist bending and a wrist pulse are detected by the SS driven with the stored energy of the MSC. This work demonstrates the possible application of our TS MSC to future skin-attachable electronics as an integrated energy storage device.

Tailoring the surface morphology and nanoparticle distribution of laser-induced graphene/Co3O4 for high-performance flexible microsupercapacitors

Recent trends have witnessed laser induced graphene (LIG) syntheses on various materials from synthetic polymers to natural precursors. Herein, porcine skin derived gelatin was used as a medium to modify the surface morphology and nanoparticle distribution of in situ synthesized Co3O4/LIG on polyimide (PI) film. By varying the applied laser fluence, the surface morphology of LIG transitions from a 3D porous structure to a multilayered structure, Co3O4 progressively distributes from the surface to the inside of the LIG structure, and the structure changes from a sphere to a whisker-like shape. These altered attributes contribute to distinct differences in the double layer capacitance and pseudocapacitance behaviors of Co3O4/LIG, as reflected in its associated electrochemical performance. Additionally, a facile fabrication strategy including simple casting and peeling steps was used to generate stretchable microsupercapacitors (MSCs) on a waterborne polyurethane (WPU) substrate. The as-prepared stretchable MSCs present outstanding areal capacitance and excellent mechanical flexibility, whereas their electrochemical differences are significantly minimized and dominated by their inner structures.

Laser‐Induced Graphene Composites for Printed, Stretchable, and Wearable Electronics

AbstractGraphene‐based composites have received attention as part of the drive towards next‐generation electronic and energy‐storage technologies. However, current graphene synthesis methods are limited by complex, time‐consuming, toxic, costly, and/or often low‐yield procedures. The synthesis of a novel stretchable graphene‐polyurethane‐poly(3,4‐ethylenedioxythiophene):polystyrene sulfonate ink aimed at printing wearable electronics is reported. The procedure is based on low‐cost high‐yield production of high‐performance graphene ink produced by laser induction of polyimide film followed by harvesting the graphene. Screen printing is used to fabricate flexible and intrinsically stretchable micro‐supercapacitors (S‐MSCs) printed on different substrates. The resulting graphene‐based printed S‐MSCs display a remarkably high capacitive performance and attractive mechanical resiliency. High specific areal capacitance, above 23 mF cm−2, is achieved, which is the highest areal capacitance reported for highly stretchable, printed graphene supercapacitors. A repeated (200 cycles) stretchability beyond 100% is obtained while maintaining more than 85% of the S‐MSCs' original capacitance. This unique and highly scalable graphene ink synthesis method holds considerable promise for application in low‐cost graphene‐based chemical formulation, especially in the field of printed and wearable electronics toward multifunctional, energy‐storage systems capable of withstanding severe mechanical deformation while maintaining their optimal electrochemical performance.

A Janus gold nanowire electrode for stretchable micro-supercapacitors with distinct capacitances

Enokitake-like gold nanowires are used to fabricate stretchable micro-supercapacitors, showing discriminative capacitive features.