Electrode Materials For Capacitors Research Articles

Vertically Aligned Bismuthene Nanosheets on MXene for High-Performance Capacitive Deionization.

Capacitive deionization has been considered as a promising solution to the challenge of freshwater shortage due to its high efficiency, low environmental footprint, and low energy consumption. However, developing advanced electrode materials to improve capacitive deionization performance remains a challenge. Herein, the hierarchical bismuthene nanosheets (Bi-ene NSs)@MXene heterostructure was successfully prepared by combining the Lewis acidic molten salt etching and the galvanic replacement reaction, which achieves the effective utilization of the molten salt etching byproducts (residual copper). The vertically aligned bismuthene nanosheets array evenly in situ grown on the surface of MXene, which not only facilitate ion and electron transport as well as offer abundant active sites but also provide strong interfacial interaction between bismuthene and MXene. Benefiting from the above advantages, the Bi-ene NSs@MXene heterostructure as a promising capacitive deionization electrode material exhibits high desalination capacity (88.2 mg/g at 1.2 V), fast desalination rate, and good long-term cycling performance. Moreover, the mechanisms involved were elaborated by systematical characterizations and density functional theory calculations. This work provides inspirations for the preparation of MXene-based heterostructures and their application for capacitive deionization.

BƯỚC ĐẦU NGHIÊN CỨU TỔNG HỢP NICKEL SULFIDE DÙNG LÀM VẬT LIỆU ĐIỆN CỰC CHO TỤ ĐIỆN HÓA

NiS as an electrode material for electrochemical capacitors has been synthesized by chemical and hydrothermal methods. The results show that the synthesized NiS is in amorphous form, increasing the reaction temperature or hydrothermal time tends to reduce the porosity of the materials. NiS synthesized by hydrothermal method exhibits better electrochemical properties than those synthesized by chemical method. NiS synthesized at the optimal condition of a hydrothermal temperature of 140 oC in 5h has a specific capacitance of 1592 F\g (265 mAh\g) and 1567 F\g (261 mAh\g) at a scan rate of 5 mV\s and a current density of 5 A\g, respectively. This value is about 88% of the theoretical value of NiS and is maintained after 25 continuous charge-discharge cycles at different current densities ranging from 5 to 40 A\g.

Halogenated and chalcogenated Ti2C MXenes: High capacity electrode materials for lithium-ion batteries

Inspired by the recent successful growth of Ti2C monolayers, we investigated the effects of Ti2CT2 (T = F, Cl, Br, O, S and Se) anode in lithium-ion batteries (LIBs) by first-principles calculations. The results revealed that Ti2CT2 MXenes exhibit metallic conductivity with higher structural stability and mechanical strength than Ti2C. Compared with other Ti2CT2 monolayers, Ti2CS2 monolayer display lower diffusion barrier, larger elastic modulus, lower open circuit voltage and higher storage capacity. Moreover, surface sulfuration yields the expanded interlayer spacing, which can improve Li-ion accessibility in double-layer Ti2CS2.

Covalent Organic Frameworks for Capacitive Energy Storage: Recent Progress and Technological Challenges

AbstractCovalent‐organic frameworks (COFs) are emerging organic crystalline materials with a porous framework that extends into two or three dimensions. Originating from their versatile and rigorous synthesis conditions, COFs have abundant and tunable pores, large and easily accessible surfaces, and plenty of redox‐active sites, making them promising material candidates for various energy storage applications. One important area is to serve as capacitive electrode materials in supercapacitors. This review provides a timely and comprehensive summary of the recent progress in the design and synthesis of COF‐based or COF‐derived materials for capacitive energy storage applications. The review starts with a brief introduction to COFs’ structural features and synthesis methods. Next, recently reported literature is categorized and introduced following their different energy storage mechanisms and material assembly or treatment approaches. Finally, the existing challenges and future directions for realizing practical COF‐based supercapacitors are discussed.

An innovative and efficient method for the preparation of mesocarbon microbeads and their use in the electrodes of lithium ion batteries and electric double layer capacitors

An innovative and efficient method for preparation of mesocarbon microbeads (MCMBs) was developed based on the dripping behavior and rheological properties of molten pitch during melt-spinning, where a string of beads was formed after the pitch was extruded from spinnerets and dropped into a receiving solvent (tetrohydrofuran or water). The pitch droplets were first carbonized, then activated by KOH or graphitized at 2 800 °C to prepare A-MCMBs or G-MCMBs, respectively, and these were respectively used as the electrode materials for electric double layer capacitors (EDLCs) and lithium-ion batteries (LIBs). Results showed that both MCMB-W prepared using water as the receiving solvent and MCMB-T prepared using tetrohydrofuran as the receiving solvent had a spherical shape with sizes of 1-2 μm. A-MCMB-T had a high specific surface area (1 391 m2 g−1), micropore volume (0.55 cm3 g−1) and mesopore volume (0.24 cm3 g−1), with a 30% higher specific capacitance than an activated mesophase carbon prepared under the same conditions, and its capacitance retention was significantly improved when it was used as an electrode material for EDLCs. G-MCMB-T had a high degree of graphitization (0.895) and when it was used as an electrode material for LIBs it had a high specific capacity of 353.5 mAh g−1 after 100 cycles at 100 mA g−1. This work reports a new preparation method for MCMBs, which could be used to prepare energy storage materials.

Nb2C MXenes with surface chalcogenation and halogenation as high capacity electrode materials for lithium-ion batteries

MXenes show extremely competitive potential applications in electrode materials for lithium-ion batteries (LIBs) due to their excellent specific surface area, high electrical conductivity, and compositional tunability. However, limited interlayer spacing and undesired surface functional group on MXene surface impede the Li-ions accessibility and mobility. Herein, the structural, electronic, mechanical and electrochemical properties of the representative Nb2C MXene with surface chalcogenation and halogenation resulting in the formation of Nb2CT2 ([Formula: see text], S, Se, Cl and Br) materials as anodes for LIBs were investigated using first-principles calculations based on density functional theory. The results reveal that Nb2CT2 can exhibit metallic conductivity with improved mechanical strength, which renders the enhanced rate performance and endures the repeated lattice expansion and contraction during charge/discharge process, respectively. In particular, Nb2CS2 and Nb2CCl2 render the enhanced Li-ion storage and mobility with a theoretical Li storage capacity of 613.76 mA[Formula: see text]h/g and 597.79 mA[Formula: see text]h/g and diffusion energy barrier of 0.275 eV and 0.294 eV, respectively. Moreover, chalcogenation and halogenation yield the expanded interlayer spacing, which improve the Li-ions accessibility in Nb2CT2. The results demonstrate that sulfurized and chlorinated Nb2C MXenes are the promising anode materials with high capacity, low diffusion barrier and lower open circuit voltage for next-generation LIBs.

Novel MoS2-sputtered NiCoMg MOFs for high-performance hybrid supercapacitor applications

Supercapacitors are considered one of the possible next-generation clean energy storage devices; however, their specific capacitance still needs improvement regarding electrode materials. Herein, we prepared three types of electrode materials, i.e., pure NiCoMg MOFs deposited on Ni-foam (abbreviated as P-NiCoMg), NiCoMg MOFs deposited on MoS2-sputtered Ni-foam (signified as SN-NiCoMg), and MoS2-sputtered NiCoMg MOFs deposited on Ni-foam (shortened as S-NiCoMg). SEM and XRD revealed a successful preparation of cactus-like microstructure and coexistence of MoS2 and NiCoMg MOFs in the material of interest S-NiCoMg electrode. Interestingly, the S-NiCoMg electrode showed a specific capacitance of 2000 F/g, which is 1.8 and 1.4 times higher than the P-NiCoMg and SN-NiCoMg electrodes, respectively. This indicates the efficacy of enhancing specific capacitance electrode materials using MoS2 sputtering. Further, an asymmetric supercapacitor device of S-NiCoMg electrode with activated carbon demonstrated excellent specific capacitance, energy density, and power density of 211 F/g, 107 Wh/kg, and 1350 W/kg, respectively. Dunn’s model revealed that most charge storage is diffusion controlled (i.e., 64 %, 58 %, and 53 % at 3, 5, and 10 mV/sec, respectively). Overall, S-NiCoMg electrode material demonstrated excellent potential to be used as functional, affordable, recyclable, and low-cost supercapacitors for energy storage applications.

Preparation of Carbon Dots@r-GO Nanocomposite with an Enhanced Pseudo-Capacitance.

Carbon materials with pseudocapacitive performance have attracted emerging interest in the energy storage and conversion field. Reduced graphene oxide (r-GO) with superior conductivity and electrochemical stability has been extensively investigated as an efficient capacitive electrode material. In this study, three-dimensional carbon dots (CDs)@r-GO hydrogel electrode was successfully in situ prepared by the one-pot method, where the CDs play a critical role in serving as both reduction agent and electrochemical active sites. With prolonged reaction time, the oxygen content of the CDs@r-GO nanocomposite material could be effectively reduced to ensure better electric conductivity, and the nitrogen content, which provides pseudocapacitance, was gradually increased. The representative two pairs of fast and reversible current peaks appeared in cyclic voltammetry curves, with around three times higher specific capacitance of CDs@r-GO hydrogel electrode (290 F g-1 at the current density of 1 A g-1 in 1 M H2SO4 electrolyte). This simple and mild approach is promising and it is believed it will shed more light on the preparation of high-efficiency and high-performance energy storage materials based on functional reductive CDs.

Co-precipitation reaction: A facile strategy for designing hierarchical porous carbon nanosheets for EDLCs and zinc-ion hybrid supercapacitors

Hierarchical porous carbon is a valuable electrode material for electrochemical energy storage devices by virtue of its high specific surface area, excellent conductivity, and large pore volume. Herein, a simple, convenient and cheap self-made Fe-based template strategy is innovated to prepare hierarchical porous carbon employing coal chemical byproducts anthracene as carbon precursor, which is utilized as electrode materials of electrical double layer capacitors (EDLCs) and zinc ions hybrid supercapacitors (ZHSs). Benefiting from the high specific surface area (2085.1 m2 g−1), feasible micropore content (0.28 cm3 g−1), suitable oxygen content (11.57 at%) and two-dimensional nanosheet structure, the optimal sample delivered a high specific capacitance value of 183.5 F g−1 at 0.05 A/g and excellent rate capability (109.5 F g−1 at 20 A/g) for symmetric supercapacitor. Meanwhile, the as-fabricated ZHSs exhibited remarkable specific capacitance (181.67 mAh/g at 0.05 A/g), superior energy density (145.2 Wh kg−1), high power density (14.5 kW kg−1) and splendid cycling stability (∼91.25 % after 40,000 charge/discharge cycles at 2 A g−1). This work affords a new idea for the synthesis of template carbon using a feasible and low-cost co-precipitation reaction route and has great significance for the development of high-performance electrochemical energy storage device.

Three-dimensional ternary NixCuyZnz(CO3)(OH)2 electrodes for supercapacitors: electrochemical properties and applications.

Transition metal-based binary and ternary compound arrays were directly grown on a porous Ni foam substrate using a facile one-step hydrothermal method. Transition metals are considered ideal electrode materials for faradaic capacitors because they exhibit a wide range of oxidation states enabling effective redox charge transfer. Furthermore, compounds in which two or more transition metals react can help increase the number of active sites for charge-discharge reactions and provide more valence changes for improved charge transfer. In this work, we fabricated ternary electrodes with Ni, Cu, and Zn ions, exhibiting a larger surface area and higher entropy than those made with binary compounds. The NixCuyZnz-based ternary electrode had a shorter diffusion path for the electrolyte ions owing to its larger surface area. Ternary compounds can increase the entropy of the electrode because of the reaction between atoms of different sizes, bringing about a synergistic effect for high characteristic electrochemical values. The optimized NixCuyZnz(CO3)(OH)2 compound showed a maximum specific capacity of 344 mA h g-1 at a current density of 3 A g-1, which was remarkably higher than that of the binary electrode, and a cycling stability of 84.9% after 5000 cycles. An asymmetric supercapacitor produced with this compound as the positive electrode and graphene as the negative electrode exhibited a high energy density of 36.2 W h kg-1 at a power density of 103.1 W kg-1 and a current density of 2 A g-1. The asymmetric supercapacitor fabricated using the NixCuyZnz(CO3)(OH)2 compound as the positive electrode exhibited excellent electrical properties when used in an illuminated LED device.

Gadolinium doped zinc ferrite nanoarchitecture reinforced with a carbonaceous matrix: a novel hybrid material for next-generation flexible capacitors.

Herein, nanostructured Gd-doped ZnFe2O4 (GZFO) has been synthesized via the sol-gel route and its CNT-reinforced nanohybrid was formed via an advanced ultrasonication method. The as-synthesized, hybrid electroactive materials have been supported on aluminum foil (AF) to design a flexible electrode for hybrid capacitor (HC) applications. Nanostructured material synthesis, Gd-doping, and CNT reinforcement approaches have been adopted to develop a rationally designed electrode with a high surface area, boosted electrical conductivity, and enhanced specific capacitance. Electrochemical impedance spectroscopy, galvanostatic charge/discharge, and cyclic voltammetry processes have been used to measure the electrochemical performance of the prepared ferrite material-based working electrodes in a 3M KOH solution. A nanohybrid-based working electrode (GZFO/C@AF) shows superior rate capacitive and electrochemical aptitude (specific capacitance, rate performance, and cyclic activity) than its counterpart working electrodes (ZFO@AF and GZFO@AF). The hybrid working electrode (GZFO/C@AF electrode) shows a high specific capacitance of 887 F g-1 and good retention of 94.5% for 7000 cycles (at 15 Ag-1). The maximum energy density and power density values for the GZFO/C@AF electrode are 40.025 Wh Kg-1 and 279.78 W Kg-1, respectively. Based on the findings of the electrochemical experiments, GZFO/C@AF shows promise as an electrode material for hybrid capacitors that provide energy to wearable electronic devices.

Titanium Dioxide Nanocluster Modified Lignite-Based Nanoporous Carbon for Capacitive Deionization

With the development of capacitive deionization (CDI) technology, low-cost and high-performance capacitive deionization electrode materials have received great attention. Herein nanoporous carbon (NPC) was prepared using lignite as the carbon source in this work. The as-prepared NPC has a hierarchical nanoporous structure with micro-, meso- and macro-sized pores. Its specific surface area can reach 3581 m2 g−1. Then TiO2 nanoclusters modified NPC composites were fabricated for better CDI performance due to their synergistic electrochemical behaviour and properties. The results show that the size of TiO2 nanoclusters is 3–5 nm. TiO2 nanoclusters are uniformly dispersed in the composites which retain the hierarchical nanoporous structure and possess high specific surface area up to 3703 m2 g−1. Compared with NPC, the performance of xTiO2@NPC was significantly improved. The specific capacitance of 10TiO2@NPC is 193.45 F g−1 with 95% capacity retention after 5000 cycles. Its CDI adsorption capacity is up to 11.23 mg g−1, which is 1.55 times of NPC (7.24 mg g−1). It provides promising candidate materials for low-cost, industrial CDI applications with high performance through a facile method.

Naturally occurring metal oxides from rocks as capacitive deionization electrode material for antibacterial activities

Naturally occurring metal oxides from rocks as capacitive deionization electrode material for antibacterial activities

PEDOT coating boosted NiCo-LDH nanocage on CC enable high-rate and durable pseudocapacitance reaction

Layered double hydroxide (LDH) is supposed to be ideal capacitive materials owing to its excellent theoretical specific capacitance. Nevertheless, the inherent defects of LDH such as unstable structure, and agglomerations along with poor conductivity, lead to low rate-capability and poor cycle stability. In this work, poly(3,4-ethylenedioxythiophene) (PEDOT)@nickel–cobalt LDH on carbon cloth ([email protected]/CC) was proposed as a highly capacity electrode material for supercapacitors. Herein, hollow NiCo-LDH nanocage was firstly assembled by NiCo-LDH nanosheets on CC (NiCo-LDH/CC) via an in-situ transformations of ZIF-67, subsequent by coating PEDOT network ([email protected]/CC) on NiCo-LDH/CC via an electrodeposition process. The unique hollow nanocage structure can effectively restrain agglomeration of the LDH nanosheets. Besides, the introduction of PEDOT not only remarkable improves the conductivity, but also protects those hollow LDH nanocages from destruction during the cycling process. Consequently, the [email protected]/CC electrode manifests outstanding capacitance properties of 1508F/g at 1 A/g, excellent rate capability of 71.9 % capacitance retention in 1–20 A/g, and remarkable cycling life of 90.1 % capacity retention at 20 A/g after 10,000 cycles. Moreover, a hybrid asymmetric supercapacitor (ASC) device was assembled by using [email protected]/CC// activated carbon. Such ASC reveals a prominent energy density of 77.1 Wh kg−1 under the power density of 750 W kg−1. This project provides new inspirations into the rational design of high-performance electrode material in application of energy storage.

First principles study of B7N5 as a high capacity electrode material for K-ion batteries.

Potassium-ion batteries (KIBs) are considered a promising candidate for energy storage owing to their low cost and similar "rocking chair" mechanism to lithium-ion batteries. However, there is a great lack of suitable and high working performance electrode materials for KIBs. Herein, first principles calculations based on density functional theory (DFT) are applied to evaluate the potential of the B7N5 monolayer as an anode material for KIBs. It is found that B7N5 shows negative adsorption energies for Li/Na/K on its surface. Besides, the B7N5 monolayer can effectively achieve double-layer adsorption for K atoms on both sides of the monolayer surface, while one-layer adsorption for Li and Na. Thus, B7N5 exhibits an ultra-high theoretical capacity of 1471.5 mA h g-1 for KIBs, which is almost the highest value for the anode materials reported in the literature. And the attractive capacity for KIBs is mainly contributed by the multiple empty electron orbitals of the constituting elements of B7N5 and the small distance mismatch. In addition, K atoms display high diffusivities on B7N5 with low energy barriers of 0.10 eV, and the open circuit voltages of 0.14 V for KIBs are also smaller compared with previous research. It is also shown that after adsorbing K, the semiconducting B7N5 monolayer is transformed to a metallic state with good conductivity. Furthermore, despite the large size of K+, the maximum change in the lattice constant of B7N5 is only 1.32%, indicating structural stability and ensuring good cycling stability for KIBs. The above-mentioned results suggest that B7N5 is a potential anode material for KIBs.

Spinel LiMn2O4 as a Capacitive Deionization Electrode Material with High Desalination Capacity: Experiment and Simulation.

Capacitive deionization (CDI) is a newly developed desalination technology with low energy consumption and environmental friendliness. The surface area restricts the desalination capacities of traditional carbon-based CDI electrodes while battery materials emerge as CDI electrodes with high performances due to the larger electrochemical capacities, but suffer limited production of materials. LiMn2O4 is a massively-produced lithium-ion battery material with a stable spinel structure and a high theoretical specific capacity of 148 mAh·g-1, revealing a promising candidate for CDI electrode. Herein, we employed spinel LiMn2O4 as the cathode and activated carbon as the anode in the CDI cell with an anion exchange membrane to limit the movement of cations, thus, the lithium ions released from LiMn2O4 would attract the chloride ions and trigger the desalination process of the other side of the membrane. An ultrahigh deionization capacity of 159.49 mg·g-1 was obtained at 1.0 V with an initial salinity of 20 mM. The desalination capacity of the CDI cell at 1.0 V with 10 mM initial NaCl concentration was 91.04 mg·g-1, higher than that of the system with only carbon electrodes with and without the ion exchange membrane (39.88 mg·g-1 and 7.84 mg·g-1, respectively). In addition, the desalination results and mechanisms were further verified with the simulation of COMSOL Multiphysics.

Highly redox active mesoporous Ni/Co-organic framework as a potential battery type electrode material for high energy density supercapattery

Designing potential electrochemically active metal-organic-framework (MOF) electrode materials with controllable structure and versatile nano-geometries are very pivotal to enable the forthcoming generation electrochemical energy storage systems. Among the hydrothermally synthesized materials; Nickel/MOF (NiMOF), Cobalt/MOF (CoMOF) and Nickel-Cobalt/MOF (Ni/CoMOF) with 1:1 of Ni/Co, the binary Ni/CoMOF shows excellent electrochemical performance compared to NiMOF and CoMOF, achieving a distinguished specific capacity of 594.24C g−1 at current density of 1 A g−1 in 3-electrode setup with 67.32 % remarkable rate capability at 10 A g−1 and excellent cyclic durability of 92.7 % after undergoing 5000 charge-discharge cycles. Further, Ni/CoMOF is employed as a positive active electrode material with Activated‑carbon (ActC) and reduced-graphene oxide (rGO) sequentially as negative capacitive type electrode materials to fabricate supercapattery devices. The high cyclically stable and novel Ni/CoMOF||rGO supercapattery unveils a striking specific capacity of 307.45C g−1 contrary to 222C g−1 of Ni/CoMOF||Act-C at 1 A g−1 and exhibits significantly increased energy density of 66.2 Wh kg−1 at power density of 775.13 kW kg−1. Overall, this synergy of Ni/CoMOF coupled with rGO in a hybrid configuration shows favorable energy storage features to fulfill the soaring renewable energy demands to power the digital world.

Electrochemical and Electrical Performances of High Energy Storage Polyaniline Electrode with Supercapattery Behavior.

Polyaniline (PANI), due to its highly reversible electrochemistry with superior energy storage and delivery characteristics, is considered as an electrode material in batteries, capacitors, and hybrid systems. We used a facile electrochemical synthesis for the formation of the PANI electrode using galvanostatic polymerization of aniline on the graphite electrode at the current density of 2.0 mA cm-2 from the aqueous electrolyte containing 0.25 mol dm-3 aniline and 1.0 mol dm-3 H2SO4. Electrochemical and electrical characterization suggested excellent energy storage features of the PANI electrode in a three-electrode system with specific energy up to 53 Wh kg-1 and specific power up to 7600 W kg-1. After 2000 successive charge/discharge cycles at 9.5 Ag-1, the PANI electrode retained 95% of the initial capacity, with practically unaltered Coulombic efficiency of nearly 98%, providing a good base for future studies and practical applications.

Optimization of porous carbon nanofiber/MnO2 electrode-based supercapacitor performance using γ‑cyclodextrin: Effects of graphene and MnCl2 contents

• Graphene and MnCl 2 content is optimized for supercapacitor performance of PCM(5)G(3). • PCM(5)G(3) has high surface area and active material of MnO 2 embedded in the fiber. • PCM(5)G(3) maximize the synergistic effect of the pseudocapacity and EDLC. • PCM(5)G(3) have great potential in electrochemical capacitor electrode materials. We systematically evaluate the influence of graphene and MnCl 2 contents on the structure and capacity of γ-cyclodextrin/graphene-based carbon nanofibers and MnO 2 (PCMG). The PCMG electrodes are stable long-term and had good capacitances, e.g., up to 236Fg -1 at 1mAcm -2 and 25.5Whkg -1 at 400Wkg -1 . The electrochemical performance is maximized by the synergistic effect between the pseudocapacity of MnO 2 well-embedded in the fiber and the electric double layer capacity induced by the well-developed surface pores.

Coal-derived N,O co-doped mesoporous carbon as electrode material for high performance aqueous electric-double layer capacitors and zinc-ion hybrid supercapacitors

Carbon-based materials are widely used as electrode materials for electrochemical energy storage devices. However, achieving high performance carbon materials via facile preparation process with abundant precursors is still a huge challenge. Herein, a nitrogen/oxygen co-doped mesoporous coal-derived carbon (N/O-DMCC) is synthesized with raw coal as precursor through a facile pyrolysis treatment. The treatment endows the N/O-DMCC with high surface area, mesoporous structure, as well as rich heteroatom doping content. The combination of above features enhances the electrochemical capacitance of the as-synthesized N/O-DMCC by delivering a satisfactory value of 376.5 F g−1 (i.e., 376.5 C g−1) at 0.5 A g−1, which is superior to many state-of-the art coal-derived carbon materials in literature. A symmetric electric-double layer capacitor (EDLC) and a zinc-ion hybrid supercapacitor (ZHS) based on N/O-DMCC electrode are assembled to achieve high energy densities of 23.1 Wh kg−1 (at 500 W kg−1) and 347.0 Wh kg−1 (at 175.5 W kg−1), respectively, strongly demonstrating the huge potential of coal-derived carbon materials for energy storage devices.