Large Volumetric Capacitance Research Articles

Interfacially Ordered NiCoMoS Nanosheets Arrays on Hierarchical Ti3C2Tx MXene for High-Energy-Density Fiber-Shaped Supercapacitors with Accelerated Pseudocapacitive Kinetics.

Balancing electrochemical activity and structural reversibility of fibrous electrodes with accelerated Faradaic charge transfer kinetics and pseudocapacitive storage are highly crucial for fiber-shaped supercapacitors (FSCs). Herein, we report novel core-shell hierarchical fibers for high-performance FSCs, in which the ordered NiCoMoS nanosheets arrays are chemically anchored on Ti3C2Tx fibers. Beneficial from architecting stable polymetallic sulfide arrays and conductive networks, the NiCoMoS-Ti3C2Tx fiber maintains fast charge transfer, low diffusion and OH- adsorption barrier, and stabilized multi-electronic reaction kinetics of polymetallic sulfide. Consequently, the NiCoMoS-Ti3C2Tx fiber exhibits a large volumetric capacitance (2472.3 F cm-3) and reversible cycling performance (20,000 cycles). In addition, the solid-state symmetric FSCs deliver a high energy density of 50.6 mWh cm-3 and bending stability, which can significantly power electronic devices and offer sensitive detection for dopamine.

Interfacially Ordered NiCoMoS Nanosheets Arrays on Hierarchical Ti3C2Tx MXene for High‐energy‐density Fiber‐Shaped Supercapacitors with Accelerated Pseudocapacitive Kinetics

Balancing electrochemical activity and structural reversibility of fibrous electrodes with accelerated Faradaic charge transfer kinetics and pseudocapacitive storage are highly crucial for fiber‐shaped supercapacitors (FSCs). Herein, we report novel core‐shell hierarchical fibers for high‐performance FSCs, in which the ordered NiCoMoS nanosheets arrays are chemically anchored on Ti3C2Tx fiber. Beneficial from architecting stable polymetallic sulfide arrays and conductive networks, the NiCoMoS‐Ti3C2Tx fiber maintains fast charge transfer, low diffusion and OH‐ adsorption barrier, and stabilized multi‐electronic reaction kinetics of polymetallic sulfide. Consequently, the NiCoMoS‐Ti3C2Tx fiber exhibits a large volumetric capacitance (2472.3 F cm‐3) and reversible cycling performance (20,000 cycles). In addition, the solid‐state symmetric FSCs deliver a high energy density of 50.6 mWh cm‐3 and bending stability, which can significantly power electronic devices and offer sensitive detection for dopamine.

Hysteresis in Organic Electrochemical Transistors: Relation to the Electrochemical Properties of the Semiconductor

The ability to bridge ionic and electronic transport coupled with large volumetric capacitance renders organic electrochemical transistors (OECTs) ideal candidates for bioelectronic applications. Adopting ionic-liquid-based solid electrolytes extends their applicability and facilitates large-area printable productions. However, OETCs employing solid electrolytes tend to show a pronounced hysteresis in the transfer curve. A detailed understanding of the hysteresis is crucial for their accurate characterizations and reliable applications. Here, we demonstrated fully photopatternable poly(3,4-ethylenedioxythiophene):tosylate (PEDOT:Tos)- based OECTs incorporating the ionic liquid [EMIM][EtSO4] in a solid electrolyte (SE). The PEDOT:Tos films deposited through vapor phase polymerization (VPP) were annealed for different durations after the polymerization step. Upon rinsing with ethanol and the deposition of the SE, the OECTs made of these films showed impressive bias stress stability under prolonged operation cycles, a high switching ratio, a low threshold voltage, and a high transconductance. Furthermore, by taking transfer measurements with different sweep rates, we revealed two distinct regimes of hysteresis: kinetic hysteresis and non-kinetic hysteresis. We observed pronounced changes in these regimes after annealing. Finally, impedance spectroscopy exhibited that the PEDOT:Tos turned from a Faradaic to a non-Faradaic response through annealing, explaining the observed hysteresis changes in both regimes.

Faradaic-active N-doped reduced graphene as electrode for supercapacitor with high-volumetric performances

The rich porosity of carbon based materials results in low packing density (ρ) thus causing low volumetric capacitances (<200 F/cm3) of the corresponding supercapacitor. Developing a functional carbon material with large packing density while maintaining moderate gravimetric capacitance (Cg) would be an effective way to realize the enhancement of volumetric performances of carbon-based supercapacitor. Herein, we presented a strategy to get a high-volumetric supercapacitor performances by constructing a nitrogen doped reduced graphene (N-rG) via a template induced assembly and nitriding method, in which the graphene oxide (GO) was firstly assembled by induction of MgO to form the composite of GO/MgO, which was then mixed with carbon nitride and carbonized to get the final nitrogen doped reduced graphene (N-rG). The developed N-rG owns surface area of 283 m2/g, nanosheet morphology, large packing density (1.64–1.69 g/cm3), rich redox heteroatoms including nitrogen (8.2–8.9 atom%) and oxygen functionalities (4.7–20.4 atom%). Due to these features, the resultant N-rG16 fabricated with mass ratio of GO/MgO (1:6) exhibits a typical pseudocapacitive behavior, large volumetric capacitance of 272 F/cm3@1.0 A/g and 200 F/cm3@20 A/g, showing an excellent rate capability with capacitance retention of 73.5 %. The N-rG16 based symmetric supercapacitor delivers a high specific energy density of 33.6 Wh/L@1352 W/L and long cycling stability with near 99 % retention of the initial capacitance after 10,000 cycles test showing a great potential for packed energy storage devices. Moreover, the developed N-rG with rich heteroatoms may also find wide applications in many other fields such as sorption, catalysis and so on.

Chemical reduction-induced fabrication of graphene hybrid fibers for energy-dense wire-shaped supercapacitors

The emerging one-dimensional wire-shaped supercapacitors (SCs) with structural advantages of low mass/volume structural advantages hold great interests in wearable electronic engineering. Although graphene fiber (GF) has full of vigor and tremendous potentiality as promising linear electrode for wire-shaped SCs, simultaneously achieving its facile fabrication process and satisfactory electrochemical performance still remains challenging to date. Herein, two novel types of graphene hybrid fibers, namely ferroferric oxide dots (FODs)@GF and N-doped carbon polyhedrons (NCPs)@GF, have been proposed via a simple and efficient chemical reduction-induced fabrication. Synergistically coupling the electroactive units (FODs and NCPs) with conductive graphene nanosheets endows the fiber-shaped architecture with boosted electrochemical activity, high flexibility and structural integrity. The resultant [email protected] and [email protected] hybrid fibers as linear electrodes both exhibit excellent electrochemical behaviors, including large volumetric specific capacitance, good rate capability, as well as favorable electrochemical kinetics in ionic liquid electrolyte. Based on such two linear electrodes and ionogel electrolyte, a high-performance wire-shaped SC is effectively assembled with ultrahigh volumetric energy density (26.9 mW·h·cm−3), volumetric power density (4900 mW·cm−3) and strong durability over 10,000 cycles under straight/bending states. Furthermore, the assembled wire-shaped SC with excellent flexibility and weavability acts as efficient energy storage device for the application in wearable electronics.

Electrochemically Exfoliated Chlorine‐Doped Graphene for Flexible All‐Solid‐State Micro‐Supercapacitors with High Volumetric Energy Density

AbstractGraphene‐constructed micro‐supercapacitors (MSCs) have received considerable attention recently, as part of the prospective wearable and portable electronics, owing to their distinctive merits of well‐tunable power output, robust mechanical flexibility, and long cyclability. In the current work, the focus is on the fabrication of high‐quality and solution‐processible chlorine‐doped graphene (Cl‐G) nanosheets through a handy yet eco‐friendly electrochemical exfoliation process. The Cl‐G is characteristic of the large lateral size of ≈10 µm, abundant nanopores with sizes of as small as 2 nm, as well as numerous steps from the rugged surface. Arising from the rich chemical functionalities and structure defects, the all‐solid‐state MSC built by using Cl‐G via a facile mask‐assisted method delivers a large reversible capacity and ultrasteady charge/discharge performance, with the capacitance being maintained at 98.1% even after 250 000 cycles. The Cl‐G‐MSC with EMIMBF4/PVDF‐HFP as the electrolyte displays a large volumetric capacitance up to 160 F cm−3 at the scan rate of 5 mV s−1 and high volumetric energy density of 97.9 mW h cm−3 at the power density of 3.4 W cm−3. The device can also output a high voltage up to 3.5 V and robust capability with 94.8% of capacitance retention upon 10 000 cycles.

Regulating zinc electroplating chemistry to achieve high energy coaxial fiber Zn ion supercapacitor for self-powered textile-based monitoring system

Coaxial fiber-shaped Zn-ion hybrid supercapacitors (CFZHSCs) with high power/energy density, long cycle life, splendid mechanical stability, and high safety are promising electrochemical energy storage devices for flexible and wearable electronics. However, the poor electrochemical performance of Zn anode severely restricts their practical application. To address this challenge, a highly reversible fiber-shaped Zn anode with controlled deposition morphology is developed based on theoretical calculation guided design of highly zincophilic 3D metal-organic-frameworks derived carbon with N- and OH-containing functional groups (N,O-MOFC) scaffold, by regulating electroplating chemistry of the initial nucleation and crystal growth time of zinc metal. Benefitting from fast ion diffusion ability of the hierarchically nanostructured 3D Zn/N,O-MOFC anode on the carbon nanotube fiber (CNTF), the assembled CFZHSCs device achieves a large volumetric specific capacitance of 128.06 F cm−3 and a high volumetric energy density of 57.63 mWh cm−3, surpassing the state-of-the-art FZHSCs device. More impressively, the efficient rechargeable capability of the fiber-shaped Zn anode also enables an adequately stable CFZHSCs device with the capacitance retention of 99.20% after 10,000 charge/discharge cycles and remarkable mechanical flexibility. As a conceptual demonstration of system integration, the as-fabricated CFZHSCs device is integrated with triboelectric nanogenerator (TENG) yarn to achieve the self-powered textile-based monitoring systems to stably detect temperature variation.

Synergistic Effect of Multi‐Walled Carbon Nanotubes and Ladder‐Type Conjugated Polymers on the Performance of N‐Type Organic Electrochemical Transistors

AbstractOrganic electrochemical transistors (OECTs) have the potential to revolutionize the field of organic bioelectronics. To date, most of the reported OECTs include p‐type (semi‐)conducting polymers as the channel material, while n‐type OECTs are yet at an early stage of development, with the best performing electron‐transporting materials still suffering from low transconductance, low electron mobility, and slow response time. Here, the high electrical conductivity of multi‐walled carbon nanotubes (MWCNTs) and the large volumetric capacitance of the ladder‐type π‐conjugated redox polymer poly(benzimidazobenzophenanthroline) (BBL) are leveraged to develop n‐type OECTs with record‐high performance. It is demonstrated that the use of MWCNTs enhances the electron mobility by more than one order of magnitude, yielding fast transistor transient response (down to 15 ms) and high μC* (electron mobility × volumetric capacitance) of about 1 F cm−1 V−1 s−1. This enables the development of complementary inverters with a voltage gain of &gt;16 and a large worst‐case noise margin at a supply voltage of &lt;0.6 V, while consuming less than 1 µW of power.

Ultralong and Millimeter-Thick Graphene Oxide Supercapacitors with High Volumetric Capacitance

The fabrication of a high energy density supercapacitor with electrodes bearing ultrahigh aspect ratio active materials is still a big challenge. Here, we successfully developed ultralong and millimeter-thick supercapacitors, which enable practical applications due to the large electrochemical volumetric capacitance overcoming the limits of previous carbon-based materials. The gel graphene oxide fibers (GOFs) with an ultrahigh aspect ratio of over 20,000,000 were completely reduced at room temperature and biscrolled with a conductive Korean traditional paper used as the matrix material for the supercapacitors without any post-treatment. The average cell capacitance value of the yarn-type supercapacitors containing 80 reduced GOFs is maximized at a scan rate of 100 mV/s. The capacitance measured at a scan rate of 1000 mV/s is over 75% of that measured at 100 mV/s.

Improving the volumetric specific capacitance of flexible polyaniline electrode: solution casting method and effect of reduced graphene oxide sheets

High volumetric specific capacitance is essential for flexible supercapacitors. In this paper, a flexible composite electrode with ultrahigh volumetric specific capacitance and good rate performance is designed and prepared. The film electrode is composed of non-porous compact polyaniline as the matrix and a small amount of reduced graphene oxide sheets as the conductive filler. The film is prepared by a newly developed solution casting method, where the casting solution is obtained by self-assembly of polyaniline and graphene oxide in a blended solution. A systematical investigation on the effect of reduced graphene oxide sheets reveals that they serve as both the conductive filler and the diffusion barrier. With the optimized reduced graphene oxide content, a large volumetric specific capacitance of 1354 F cm−3 at 2.4 A cm−3 is achieved, and good rate performance is also obtained because of the good ionic conductivity of polyaniline. This work provides a high-performance electrode for flexible supercapacitors, and the solution casting method is also valuable in fabricating other organic electrode materials.

Facile fabrication of flexible rGO/MXene hybrid fiber-like electrode with high volumetric capacitance

Graphene fibers or fiber-like graphene materials have been successfully adopted as electrodes for flexible and wearable supercapacitors. However, they normally exhibit relatively low volumetric capacitance, which will seriously hinder their wide applications in smart textile as power supply. Here, a facile confined hydrothermal strategy to fabricate fiber-like reduced graphene oxide (rGO)/MXene hybrids is designed through ingenious assemble of two functional two dimensional materials of graphene and MXene nanosheets. Owing to the synergistic interactions between two layers, the hybrid rGO/M − 5 exhibits a large volumetric capacitance of 345 F cm−3 with the gravimetric capacitance of 195 F g−1 at 0.1 A g−1 with only 5 wt% MXene layers. A volumetric energy density of 30.7 mWh cm−3 with power density of 70.7 mW cm−3 could be delivered. After 7500 cycles at a current density of 0.5 A g−1, about 125% of its initial capacitance value is retained, demonstrating excellent electrochemical stability. More importantly, due to the suppressed oxidation process of MXene sheets in the hybrid, rGO/MXene could retain 95% of its original capacitance after one month.

Ultrathin carbon layer-encapsulated TiN nanotubes array with enhanced capacitance and electrochemical stability for supercapacitors

Although titanium nitride (TiN) is promising as electrode material in supercapacitors due to the high conductivity, there are drawbacks such as the brittleness, low capacitance, and chemical stability. Herein, three-dimensional (3D) carbon-encapsulated mesoporous titanium nitride nanotubes (TiN/C NTs) arrays with carbon doping are prepared by one-step nitridation of anodic TiO2 NTs with organic electrolyte as the carbon source. In TiN/C NTs, 3D carbon matrix not only serves as a protective layer and mechanical support to mitigate electrochemical oxidation and structural collapse, but also provides a conductive network to facilitate electron transfer. The capacitance retention of the TiN NTs electrodes increases from 72.5 to 92.2% for 4000 cycles after carbon encapsulating. Moreover, the carbon doping increases the active charge storage sites of the TiN NTs. The TiN/C NTs electrode exhibits a large volumetric capacitance of 121 F cm−3 (0.83 A cm−3), which is one time larger than that of the pure TiN NTs (69 F cm−3). The symmetrical all-solid-state device assembled with two TiN/C NTs electrodes and polyvinyl alcohol electrolyte shows a large volumetric capacitance of 8.3 F cm−3. This finding provides a good potential application in flexible supercapacitor.

Camphor wood waste-derived microporous carbons as high-performance electrode materials for supercapacitors

Sustainable biomass-derived porous carbons demonstrate excellent capacitive properties owing to their heteroatom-rich nature and distinct textural feature. Herein, a series of nitrogen-/phosphorus-/oxygen-containing microporous carbons (CWW-N/P/O-MPCs) have been successfully fabricated by etching in H2O2 solution, pre-treatment of camphor wood wastes with KOH solution and subsequent carbonization. As an electrode material for supercapacitors, the typical microporous carbon (CWW-N/P/O-MPCs-0.5) exhibits a remarkably high specific capacitance of 245 F g−1 at 0.5 A g−1, corresponding to an impressively large volumetric capacitance of 208 F m−3, and excellent long-term stability over 10,000 cycles. The excellent electrochemical performance can be ascribed to the optimal combination of heteroatom groups and ultrafine micropores.

Microfluidic-spinning construction of black-phosphorus-hybrid microfibres for non-woven fabrics toward a high energy density flexible supercapacitor

Flexible supercapacitors have recently attracted intense interest. However, achieving high energy density via practical materials and synthetic techniques is a major challenge. Here, we develop a hetero-structured material made of black phosphorous that is chemically bridged with carbon nanotubes. Using a microfluidic-spinning technique, the hybrid black phosphorous–carbon nanotubes are further assembled into non-woven fibre fabrics that deliver high performance as supercapacitor electrodes. The flexible supercapacitor exhibits high energy density (96.5 mW h cm−3), large volumetric capacitance (308.7 F cm−3), long cycle stability and durability upon deformation. The key to performance lies in the open two-dimensional structure of the black phosphorous/carbon nanotubes, plentiful channels (pores <1 nm), enhanced conduction, and mechanical stability as well as fast ion transport and ion flooding. Benefiting from this design, high-energy flexible supercapacitors can power various electronics (e.g., light emitting diodes, smart watches and displays). Such designs may guide the development of next-generation wearable electronics.

Hierarchical double-shelled poly(3,4-ethylenedioxythiophene) and MnO2 decorated Ni nanotube arrays for durable and enhanced energy storage in supercapacitors

As an attractive supercapacitor material, MnO2 greatly suffers poor conductivity and unsatisfied stability. In this work, double-shelled poly(3,4-ethylenedioxythiophene) (PEDOT) and MnO2 decorated Ni nanotube arrays (NTAs) are successfully synthesized by a simple electrodeposition strategy, endowing the hybrid with remarkably improved conductivity and prolonged durability. As a self-supported electrode, the resulting PEDOT@MnO2@NiNTAs exhibits outstanding electrochemical properties, including high mass capacitance (based on MnO2 mass, 442.85 F g−1 at 2.5 A g−1) and excellent cycling stability (80.37% capacitance retention after 15000 cycles). Furthermore, when assembling an asymmetric supercapacitor with the PEDOT@MnO2@NiNTAs and activated carbon (AC), the device affords a voltage window up to 1.7 V and delivers a large volumetric capacitance (1.47 F cm−3 at 4 mA cm−3) and high energy density (0.59 mWh cm−3 at power density of 84.96 mW cm−3), indicating its great potential in practical supercapacitor applications.

Acid-Assisted Exfoliation toward Metallic Sub-nanopore TaS2 Monolayer with High Volumetric Capacitance.

Conductive porous structures are favorable as active electrode materials for energy storage by boosting the active sites and specific surface area but have been rarely achieved in transition metal dichalcogenides. Here, we developed acid-assisted exfoliation for the first time, to successfully exfoliate TaS2 into very large-sized conductive monolayers with controllable in-plane sub-nanopores. By inducing both interlayer lattice expansion and basal in-plane etching, hydrogen ion, previously regarded disastrous in charged system, was creatively utilized as an efficient and easily accessible assistant in simultaneous exfoliation and controllable structural modification. Benefiting from pore size (∼0.95 nm) matching well with electrolyte ion size, coexistence of ultrahigh conductivity and fast ion transport was achieved in metallic large-sized monolayers. Notably, the as-produced TaS2-based electrode delivers large volumetric capacitance (508 F/cm3 at scan rate of 10 mV/s) and high energy density (58.5 Wh/L) when fabricated into a micro-supercapacitor. We anticipate acid-assisted exfoliation to be a promising strategy in constructing 2D nanomaterials with novel structure for wide energy applications.

Flexible Black-Phosphorus Nanoflake/Carbon Nanotube Composite Paper for High-Performance All-Solid-State Supercapacitors.

We proposed a simple route for fabrication of the flexible BP nanoflake/carbon nanotube (CNT) composite paper as flexible electrodes in all-solid-state supercapacitors. The highly conductive CNTs not only play a role as active materials but also increase conductivity of the hybrid electrode, enhance electrolyte shuttling and prevent the restacking between BP nanoflakes. The fabricated flexible all-solid-state supercapacitor (ASSP) device at the mass proportion of BP/CNTs 1:4 was found to deliver the highest volumetric capacitance of up to 41.1 F/cm3 at 0.005 V/s, superior to the ASSP based on the bare graphene or BP. The BP/CNTs (1:4) device delivers a rapid charging/discharging up to 500 V/s, which exhibits the characteristic of a high power density of 821.62 W/cm3, while having outstanding mechanical flexibility and high cycling stability over 10 000 cycles (91.5% capacitance retained). Moreover the BP/CNTs (1:4) ASSP device still retains large volumetric capacitance (35.7 F/cm3 at the scan rate of 0.005 V/s) even after 11 months. In addition, the ASSP of BP/CNTs (1:4) exhibits high energy density of 5.71 mWh/cm3 and high power density of 821.62 W/cm3. As indicated in our work, the strategy of assembling stacked-layer composites films will open up novel possibility for realizing BP and CNTs in new-concept thin-film energy storage devices.

A robust free-standing MoS2/poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) film for supercapacitor applications

Two-dimensional molybdenum disulfide (MoS2) is a promising energy storage material due to its high surface area and unique electronic structure. Free-standing flexible MoS2-based electrode is of importance for use in flexible energy storage devices, whereas there are limited reports available. In this work we developed a robust hybrid film, MoS2 incorporated with highly conductive poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate). This free-standing film possesses excellent mechanical properties with a fracture strength of 18.0MPa and a Young’s modulus of 2.0GPa. It can deliver a large volumetric capacitance of 141.4Fcm−3, a high volumetric energy density of 4.9mWhcm−3, and a capacitance retention rate of 98.6% after 5000 charge/discharge cycles. This film has demonstrated its application in an all-solid-state bendable supercapacitor as well.

All-solid-state flexible microsupercapacitor based on two-dimensional titanium carbide

MXenes, serving as a novel family of two-dimensional (2D) metal carbides, have attracted great research interest as one of the promising electrode materials due to the unique properties. However, to our best knowledge, the 2D titanium carbide (one kind of MXene) used in constructing microsupercapacitors (MSCs) has not yet been reported to date. To this end, we firstly produce the MXene films on various kinds of substrates including polyethylene terephthalate (PET), silicon oxide film and titanium plate through vacuum-filtrating and subsequent controlled transferring. On this basis, flexible all-solid-state symmetric MSCs on PET substrate based on MXene films are fabricated by micro-fabrication process using polyvinyl alcohol (PVA)/H2SO4 as gel electrolyte. The results show that the as-made MSC has an ultrahigh rate performance with the scan rate of up to 1000Vs−1 as well as an ultrafast frequency response (τ0=0.5ms). In addition, the MSC delivers a large volumetric capacitance of 1.44Fcm−3, a high volumetric energy density (0.2mWhcm−3) at the current density of 0.288Acm−3 and a good cycling stability. Our research results presented here may pave the way for a new potential application of MXene in micro-power suppliers and micro-energy storage devices.

Densely-packed graphene/conducting polymer nanoparticle papers for high-volumetric-performance flexible all-solid-state supercapacitors

Graphene-based all-solid-state supercapacitors (ASSSCs) are one of the most ideal candidates for high-performance flexible power sources. The achievement of high volumetric energy density is highly desired for practical application of this type of ASSSCs. Here, we present a facile method to boost volumetric performances of graphene-based flexible ASSSCs through incorporation of ultrafine polyaniline-poly(4-styrenesulfonate) (PANI-PSS) nanoparticles in reduced graphene oxide (rGO) papers. A compact structure is obtained via intimate contact and π–π interaction between PANI-PSS nanoparticles and rGO sheets. The hybrid paper electrode with the film thickness of 13.5μm, shows an extremely high volumetric specific capacitance of 272F/cm3 (0.37A/cm3 in a three-electrode cell). The assembled ASSSCs show a large volumetric specific capacitance of 217F/cm3 (0.37A/cm3 in a two-electrode cell), high volumetric energy and power density, excellent capacitance stability, small leakage current as well as low self-discharge characteristics, revealing the usefulness of this robust hybrid paper for high-performance flexible energy storage devices.