Rational Design of Porous Structured Nickel Manganese Sulfides Hexagonal Sheets-in-Cage Structures as an Advanced Electrode Material for High-Performance Electrochemical Capacitors

The design of hierarchical electrodes comprising multiple components with a high electrical conductivity and a large specific surface area has been recognized as a feasible strategy to remarkably boost pseudocapacitors. Herein, we delineate hexagonal sheets-in-cage shaped nickel–manganese sulfides (Ni-Mn-S) with nanosized open spaces for supercapacitor applications to realize faster redox reactions and a lower charge-transfer resistance with a markedly enhanced specific capacitance. The hybrid was facilely prepared through a two-step hydrothermal method. Benefiting from the synergistic effect between Ni and Mn active sites with the improvement of both ionic and electric conductivity, the resulting Ni-Mn-S hybrid displays a high specific capacitance of 1664 F g⁻¹ at a current density of 1 A g⁻¹ and a capacitance of 785 F g⁻¹ is maintained at a current density of 50 A g⁻¹, revealing an outstanding capacity and rate performance. The asymmetric supercapacitor device assembled with the Ni-Mn-S hexagonal sheets-in-cage as the positive electrode delivers a maximum energy density of 40.4 Wh kg⁻¹ at a power density of 750 W kg⁻¹. Impressively, the cycling retention of the as-fabricated device after 10 000 cycles at a current density of 10 A g⁻¹ reaches 85.5 %. Thus, this hybrid with superior capacitive performance holds great potential as an effective charge-storage material.     

泡沫状二维复合材料的合成及超级电容器性能

利用蔗糖和乙醇作为碳源,以氯化镍高温还原形成的镍颗粒作为模板,制备了泡沫状石墨烯多孔材料。 继而以其作为载体,通过浸渍和高温热解法制备了泡沫状MoS₂/石墨烯二维复合材料。 通过扫描电子显微镜(SEM)、透射电子显微镜(TEM)、拉曼光谱、X射线衍射(XRD)等技术手段研究了复合材料的形貌、组成和结构。 循环伏安、恒流充放电和循环寿命测试均表明,该材料具有良好的超级电容器性能,质量比电容达203.5 F/g,面积比电容达280 mF/cm²,5000次恒流充放电循环后的电容保持率约80%。     

Improving the performance of all-solid-state supercapacitors by modifying ionic liquid gel electrolytes with graphene nanosheets prepared by arc-discharge

Ionic liquid gel polymers have widely been used as the electrolytes in all-solid-state supercapacitors, but they suffer from low ionic conductivity and poor electrochemical performance. Arc discharge is a fast, low-cost and scalable method to prepare multi-layered graphene nanosheets, and as-made graphene nanosheets （denoted as ad-GNSs） with few defects, high electrical conductivity and high thermal stability should be favorable conductive additive materials. Here, a novel ionic liquid gel polymer electrolyte based on an ionic liquid （EM1MNTF2） and an copolymer （P（VDF-HFP）） was modified by the addition of ad-GNSs as an ionic conducting promoter. This modified gel electrolyte shows excellent thermal stability up to 400 ℃ and a wide electrochemical window of 3 V. An all-solid-state supercapacitor based on commercial activated carbon was fabricated using this modified ionic liquid gel polymer electrolyte, which shows obviously improved electrochemical behaviors compared with those of the corresponding all-solid-state supercapacitor using pure ionic liquid gel polymer electrolyte. Specially, smaller internal resistance, higher specific capacitance, better rate performance and cycling stability are achieved. These results indicate that the ionic liquid gel polymers modified by ad-GNSs would be promising and suitable gel electrolytes for high performance all-solid-state electrochemical devices.     

Sub-nanopores-containing N,O-codoped porous carbon from molecular-scale networked polymer hydrogel for solid-state supercapacitor

A template-free carbonization-activation route is developed to fabricate sub-nanopore-containing porous carbon by using a novel polypyrrole(PPy) hydrogel as a precursor.This design of PPy hydrogel precursor containing molecular-scale grids(diameter～2.0 nm) allows for homogeneous N,O-codoping into the porous carbon scaffold during the pyrolysis process.A subsequent activation step produces activated porous carbons(APCs) with tailored pore structures,which renders the APCs abundant subnanopores on their surface to increase the specific capacitance as extra capacitance sites.Coupled with large specific surface area and abundant heteroatoms,the optimized APC4/1 displays excellent specific capacitance of 379 F/g for liquid-state supercapacitor and 230 F/g for solid-state supercapacitor.The solid-state supercapacitor shows a high energy density of 22.99 Wh/kg at power density of 420 W/kg,which is higher than most reported porous carbon materials and satisfy the urgent requirements of elementary power source for electric vehicles.Moreover,this method can be easily modified to fabricate sub-nanopore-containing porous carbons with preferred structures and compositions for many applications.     

Oxidant aggregate-induced porosity in vapour-deposited polymer films and correlated impact on electrochemical properties

ABSTRACT

Persistently doped conjugated polymers are integral for energy storage, flexible electronics, and biosensors due to their unique ability to interact with both ionic and electronic currents. To maximise the performance of devices across these fields, research has focused on controlling material properties to optimise conductivities of both types of charge carriers. The challenge lies in improving ionic transport, which is typically the rate-limiting step in redox processes, without sacrificing electronic conductivity or desirable mechanical properties. Here we report on control of nanostructure in vapour deposited conducting polymer films and correlate changes in film structure with resulting electrochemical properties. Structural control is enabled by exploiting the growth of oxidant nanoaggregates during the reactive vapour deposition process. Relative to dense films, porous films exhibit faster response times in electrochemical testing. Scan rate analysis confirms a transition away from diffusion-limited charging kinetics and demonstrates the important role that porosity can play in ion transport through electroactive polymers. Advantageously, continuous polymer networks remain evident in nanostructured films, ensuring that high electronic conductivities are maintained along with high porosity. We find that such enhanced properties are retained even as polymer thickness increases ten-fold. The films reported herein may serve as robust electrodes in flexible electrochemical devices.     

Semiconducting properties of polypyrrole films in aqueous solution

The influence of the nature of the anions on the conductivity of polypyrrole films in aqueous solution was investigated by photocurrent spectroscopy combined with electrochemical impedance spectroscopy in dependence on the potential. As demonstrated, the conductivity of polypyrrole films at negative potentials can vary from a semiconducting to an ionic conducting state, depending on the size of the charge-compensating counter-anion incorporated during the electropolymerization. The reduced polypyrrole shows semiconducting properties when small anions are inserted, releasing the polymer matrix during the reduction process. The polymer can than be considered as a two-layer system, consisting of a semiconducting layer and a porous layer. Measurements at different thickness of polypyrrole films have shown that the position of the semiconducting layer is in the electrode/polymer interface. The ohmic resistance of the semiconducting layer is in the range 1–5 kΩ, the capacitance approaches a value of 100–500 nF and the flatband potential is −0.62 V_SCE. If large anions are incorporated, cation insertion takes place during reduction, the electrolyte content in the polymer then is relatively high and the polymer's behaviour is similar to that of an ionic conductor. The results are presented and discussed together with the example of methylsulfonate as a relatively small anion and polystyrenesulfonate as a large anion. Received: 28 July 1998 / Accepted: 22 February 1999     

Highly Stretchable and Conductive Hybrid Fibers for High-performance Fibrous Electrodes and All-solid-state Supercapacitors

The development of lightweight, flexible, and stretchable energy storage systems is essential for state-of-the-art electronic devices.We propose a new and broad strategy to fabricate a stretchable and conductive GO/CNTs-TPU fiber electrode by direct wet spinning, from which a flexible fibrous supercapacitor is fabricated. The fibrous electrode exhibits a high strength of 11.68 MPa, high conductivity of 342 S/cm, and high specific capacitances(21.8 mF/cm, 36.45 F/cm~3, and 95 F/g). The specific capacitance of the assembled all-solid-state hybrid fiber-shaped supercapacitor reaches 14.3 F/cm~3. After 5000 charge-discharge cycles, 97% of the capacitance of the hybrid supercapacitor is maintained. These high-strength electrochemical electrode materials could be potential candidates for applications in practical and large-scale energy storage systems and textile clothes.     

Flexible Three‐Dimensional Graphene Hydrogels with Superior Conductivity and Excellent Electrochemical Performance for Supercapacitor Electrodes

Three‐dimensional porous graphene hydrogels have been prepared by a green and facile but very efficient approach using glucose as an assistant. Based on a one‐step hydrothermal reaction with optimal experimental conditions such as the reaction time and temperature, the graphene hydrogels exhibit a superior electrical conductivity (95.3 S/m) and can be used as supercapacitor electrode without any binder or conducting additives but showing a high specific capacitance of 384.6 F/g at a current density of 1 A/g. The results show that addition of glucose can not only greatly decrease the reaction temperature but also shorten the reaction time. The superior performance of the three‐dimensional porous graphene hydrogels as electrode for supercapacitor suggests its promising potentials in the field of energy storage devices.     

Cobalt and nitrogen atoms co-doped porous carbon for advanced electrical double-layer capacitors

Electrical double-laye r capacitors are widely concerned fo r their high power density,long cycling life and high cycling efficiency.However,their wide application is limited by their low energy density.In this study,we propose a simple yet environmental friendly method to synthesize cobalt and nitrogen atoms co-doped porous carbon(CoAT-NC) material.Cobalt atoms connected with primarily pyridinic nitrogen atoms can be uniformly dispersed in the amorphous carbon matrix,which is benefit for improving electrical conductivity and density of states of the carbon material.Therefore,an enhanced perfo rmance is expected when CoAT-NC is served as electrode in a supercapacitor device.CoAT-NC displays a good gravimetric capacitance of 160 F/g at 0.5 A/g combing with outstanding capacitance retention of 90% at an extremely high current density of 100 A/g in acid electrolyte.Furthermore,a good energy density of30 Wh/kg can be obtained in the organic electrolyte.     

Electrochemical supercapacitors based on novel hybrid materials made of carbon nanotubes and polyoxometalates

We have characterized symmetric solid-state supercapacitors in swagelok cells using film electrodes made of novel hybrid materials based on multiwalled carbon nanotubes (CNT) and phosphomolybdate polyanion (Cs-PMo12) with PVA as binder. These hybrid materials were carried out by Cs-PMo12 adhesion onto previously functionalized CNT, in order to disperse both components at a molecular level and use Cs-PMo12 as energy density enhancer in supercapacitor cells. Our results show high capacitance values (up to 285 F/g at I = 200 mA/g) due to the contribution of Cs-PMo12, which was revealed on the higher energy density values compared to pure CNT electrodes. Additionally, good stability was observed during 500 charge–discharge cycles for most hybrid electrodes. These preliminary results show a new approach to enhance energy density of double layer supercapacitor cells through the introduction of Cs-PMo12, whereas from a material science point of view these materials are innovative, and open the way to search for diverse applications aside from supercapacitors (sensors, catalysts, photovoltaic cells, etc.).     

Capacitance and field-driven electron transport in electrochemically self-assembled nanoporous ZnO/dye hybrid films

Electrodeposited nanoporous ZnO/eosin Y hybrid films have been investigated in view of their potential applications in dye-sensitized solar cells and supercapacitors. Intensity-modulated photocurrent spectra were measured at different electrode potentials at films of different thicknesses. It was found that the results represent either the RC constant of the cell and surface recombination of photogenerated holes with electrons or the diffusion of photogenerated electrons and are dependent on the electron concentration in the ZnO, which is influenced by the film thickness, the electrode potential, and the light intensity. The results suggest that the porosity of the electrodeposited ZnO increases with the film thickness and the films therefore consist of two parts, a less porous part deposited in the first few minutes that exhibits field-driven electron transport and a more porous outer part where electron transport is by diffusion. The results are supported by frequency-dependent capacitance measurements, which also show that the material is suitable for supercapacitors.     

Porous carbon globules with moss-like surfaces from semi-biomass interpenetrating polymer network for efficient charge storage

The bio-nanotechnological fabrication of high-surface-area carbons has attracted widespread interest in supercapacitor applications by using readily-available natural products as raw materials or bio-templates, and is expected to refine on pore accessibility for compact energy storage. Here, a renovated design strategy of semi-biomass interpenetrating polymer network (IPN) derived carbon is demonstrated through physically knitting the biomacromolecule (sodium alginate, SA) polymeric chains into the highly crosslinked resorcinol-formaldehyde (RF) network and subsequent thermochemical conversion. Molecule-level interlacing forces in such IPN efficiently relieve the RF skeleton shrinkage when producing carbon, while the other SA network addresses the macrophase separation issue to sacrifice as an in-knitted porogen and a morphology-directing agent. As a result, porous carbon globules are equipped with moss-like surfaces and interconnected pore architecture for high accessible electrode surface (1013 m²/g), and efficient electrochemical responses are reached with the specific capacitance of 312 F/g at 1 A/g. Taking the advantage of 9 mol/kg NaClO₄ complex-solvent electrolyte, the voltage window is extended to 2.4 V, endowing the two-electrode device with the high energy delivery of 32.3 Wh/kg at 240 W/kg.     

Monolithic capillary columns based on pentaerythritol acrylates for molecular‐size‐based separations of synthetic polymers

Monolithic capillary columns based on pentaerythritol triacrylate and pentaerythritol tetraacrylate were synthesized using different compositions of polymerization mixtures and different polymerization conditions. The impact of porogen type and porogen/monomer ratio on the porosity of synthesized monoliths was investigated. Porogen type appears to be the main factor influencing the separating properties of the monolithic sorbent. Using optimal polymerization conditions (porogen type, porogen/monomer ratio, reaction temperature, time etc.) monoliths with a porous structure optimized for polymer separations can be obtained. The monolithic capillary columns containing porous sorbents with optimized porosity are capable of separating 10 to 12 polystyrene standards in one chromatographic run utilizing both size exclusion chromatography and hydrodynamic chromatography separation mechanisms.     

Ionic Liquid/Poly(ionic liquid)-based Semi-solid State Electrolytes for Lithium-ion Batteries

Ionic liquids(ILs) have appeared as the most promising electrolytes for lithium-ion batteries, owing to their unique high ionic conductivity, chemical stability and thermal stability properties. Poly(ionic liquid)s(PILs) with both IL-like characteristic and polymer structure are emerging as an alternative of traditional electrolyte. In this review, recent progresses on the applications of IL/PIL-based semi-solid state electrolytes, including gel electrolytes, ionic plastic crystal electrolytes, hybrid electrolytes and single-ion conducting electrolytes for lithium-ion batteries are discussed.     

Hybrid organic–inorganic nanocomposite materials for application in solid state electrochemical supercapacitors

Integration into a conducting polymer matrix to form a hybrid material is an effective way to harness the electrochemical activity of nanosized oxide clusters. By anchoring them into polyaniline, the reversible redox chemistry of the otherwise soluble polyoxometalate clusters can be combined with that of the conducting polymer and be put to work in energy storage applications. We present here preliminary results that show how the resulting hybrid polymer displays the combined activity of its organic and inorganic components to store and release charge in a solid state electrochemical capacitor device.     

Biomass derived nitrogen doped carbon with porous architecture as efficient electrode materials for supercapacitors

Developing porous carbon materials with low-cost, sustainable and eco-friendly natural resources is emerging as an ever important research field in the application of high-performance supercapacitor. In this paper, a simple synthetic method to fabricate nitrogen doped porous carbon(NPC) is developed via a one-pot carbonization of sodium alginate and urea. The as-prepared NPC annealed at 700℃ with mesoand macro-porous structure exhibits excellent specific capacitance(180.2 F/g at 1 A/g) and superior cycling life when serves as electrode materials for supercapacitor. Moreover, the investigation on the annealing temperature demonstrates that NPC pyrolysis at 700℃ possesses relatively high pyrrole nitrogen and pyridine nitrogen, which is favorable for enhancing supercapacitor performance. This work extends biomass derived carbon materials in energy storage applications.     

Evaluation of the main processing parameters influencing the performance of poly(vinylidene fluoride–trifluoroethylene) lithium-ion battery separators

Poly(vinylidene fluoride–trifluoroethylene) (PVDF–TrFE) membranes are evaluated for lithium-ion battery separator applications. Some of the main parameters affecting separator performance such as porosity, dehydration of lithium ions, and processing technique (Li-ion uptake versus composite formation) are investigated. The polymer characteristics, as determined by infrared spectroscopy, do not change as a function of porosity, dehydration of lithium ions in the electrolyte solution, or processing technique. The electrochemical impedance spectroscopy represented through the Nyquist plot, Bode plot, and the ionic conductivity as a function of temperature strongly depends on the aforementioned parameters. The membrane that exhibits the highest ionic conductivity is a porous membrane without dehydration of lithium ions and prepared by the uptake technique. The performance of the membrane for battery applications are, therefore, strongly influenced both by porosity and processing technique.     

石墨烯/聚3，4-乙烯二氧噻吩复合物的电化学制备及其在超级电容器中的应用

首次提出了一种在离子液体中在石墨烯表面用恒电流法聚合3,4-乙烯二氧噻吩(EDOT)单体制备石墨烯/聚3,4-乙烯二氧噻吩(石墨烯/PEDOT)复合物的方法。用原子力显微镜、扫描电镜等技术表征证明石墨烯/PEDOT复合物是由PEDOT纳米谷粒状颗粒分散在石墨烯片表面而组成的。将该复合物用作超级电容器电极材料时,在1.0 A.g-1的充放电比电流下得到的比电容值为181 F.g-1。同时,该材料还显现出较好的充放电可逆性和稳定性。     

Self-Standing Hydrogels Composed of Conducting Polymers for All-Hydrogel-State Supercapacitors

Conducting polymer hydrogels that are capable of contacting with electrolytes at the molecular level, represent an important electrode material. However, the fabrication of self-standing hydrogels merely composed of conducting polymers is still challenging owing to the absence of reliable methods. Herein, a novel and facile macromolecular interaction assisted route is reported to fabricate self-standing hydrogels consisting of polyaniline (PANi: providing high electrochemical activity) and poly(3,4-ethylenedioxythiophene) (PEDOT: enabling high electronic conductivity). Owing to the synergistic effect between them, the self-standing hydrogels possess good mechanical properties and electronic/electrochemical performances, making them an excellent potential electrode for solid-state energy storage devices. A proof-of-concept all-hydrogel-state supercapacitor is fabricated, which exhibits a high areal capacitance of 808.2 mF cm⁻², and a high energy density of 0.63 mWh cm⁻³ at high power density of 28.42 mW cm⁻³, superior to many recently reported conducting polymer hydrogels based supercapacitors. This study demonstrates a novel promising strategy to fabricate self-standing conducting polymer hydrogels.     

An overview on the recent developments in polyaniline‐based supercapacitors

With the ever‐increasing depletion of nonrenewable fossil fuel reserve, greater attention has been directed towards renewable energy storage devices. One of the most important of such devices is the supercapacitor, which exhibits high specific capacitance. Polyaniline (PAni) is a versatile conducting polymer, which has demonstrated excellent electrochemical properties along with good stability and ease of synthesis. Therefore, PAni has been extensively used in the fabrication of supercapacitors. In the last few decades, researchers have studied the effect of morphology, developed during the synthesis of PAni, on its electrochemical properties. It is known that the electrical conductivity and the electrochemical properties of PAni get influenced by the level and type of dopant used, the method of synthesis adopted, and the surface area and porosity possessed. However, it has been realized that supercapacitors based on PAni suffer from short cycle life. This led to development of PAni composites with carbon‐based materials and transition metal oxides. In this review, focus has been laid on the achieved performance levels of the recently developed PAni‐based supercapacitors. In addition, an attempt has been made to study the fundamental aspects of the conductivity and the electrochemical properties of PAni and their effect on the supercapacitor performance. Moreover, several new interesting applications of PAni‐based supercapacitors have also been included in this review.