Electrode Preparation Process Research Articles

In‐situ Construction of Self‐Healing Polyelectrolyte/Polyzwitterion Coacervate Framework for High‐Performance Silicon Anodes

AbstractSilicon is considered as a promising candidate for anode materials due to its ultrahigh theoretical capacity and natural abundance. However, the commercialization is severely hampered by the large strain and short cycle life. Herein, we have synthesized a reversible polyelectrolyte/polyzwitterion coacervate framework to achieve high‐performance silicon anodes with high initial Coulombic efficiency (ICE) and stable cyclability. Such coacervate framework is formed via in‐situ free radical polymerization of zwitterionic 2‐methacryloyloxy ethyl phosphorylcholine (MPC) with polyacrylic acid (pAA) during heating the slurry. The resulting pAA/pMPC coacervate framework presents excellent adhesion, thermal stability, and negligible swelling in the electrolyte. Comparing with pAA, pAA/pMPC0.1 coacervate framework binder exhibits superior performance during charge/discharge. The ICE is improved from 84.41 %, to 87.61 %. After 250 cycles, the specific capacity of pAA/pMPC0.1 silicon anode is 1678 mAh g−1 with a retention of 78 % while the pAA silicon anode completely failed after less than 200 cycles. Such improvement is ascribed to the structural integrity of the electrode endowed by the self‐healing ability of pAA/pMPC coacervate framework. This work not only offers a feasible method to in‐situ construct coacervate framework with self‐healing capability to achieve high‐performance silicon anodes but also a compatible electrode preparation process for other high‐capacity materials.

In situ growth of an active catalytic layer on commercial stainless steel via a hydrothermal-assisted corrosion process for efficient oxygen evolution reaction

Schematic diagrams of the preparation process of corrosion electrodes and the formation mechanism.

Fibre-based stretchable electrodes for flexible metamaterial electronics: A review

Abstract Flexible electronics researchers have been conducting studies to explore the response of flexible stretchable electrodes to strain. The regulation of strain response in current flexible stretchable electrodes relies primarily on altering the material system, interfacial adhesion, or electrode structure. However, modifying the material system or interfacial adhesion can negatively disrupt the stretchable electrode preparation process, making commercialization a significant challenge. Additionally, the material system may be inadequate in extreme environments such as high temperatures. Hence a systematic structural design approach is crucial for effective response modulation of stretchable electrodes. One potential solution is the design of fibre structures from the micro to macro scale. This article focuses on discussing how the response of stretchable electrodes can be modulated by fibres in different states. The discussion includes fibres on elastic films, fibres directly constituting fibrous membranes at the microscopic level, and fibres constituting metamaterials at the fine level. The modulation can be achieved by altering the orientation of the fibres, the geometrical structure of the fibres themselves, and the geometrical structure formed between the fibres. Additionally, the article analyses the current situation of stretchable electrodes in extreme environments such as high temperatures. It also reviews the development of ceramic fibre membranes that can be stretched in high-temperature environments. The authors further discuss how the stretchability of ceramic fibre membranes can be improved through the structuring of ceramic fibre membranes with metamaterials. Ultimately, the goal is to realize stretchable electrodes that can be used in extreme environments such as high temperatures.

Bimetallic Pd‐Sn Catalytic Electrodes from Deep Eutectic Solvents for Selective Nitrate Reduction Toward Nitrogen

AbstractNitrate is one of the most widespread water contaminants globally. Nitrate levels in groundwater and surface water can rise to unhealthy levels as a result of nitrogen fertilizer runoff from lawns and farms. This research aims to selectively convert nitrate to gaseous nitrogen using Palladium‐Tin (Pd‐Sn) bimetallic electrodes electrodeposited on stainless‐steel (SS). Inductively coupled plasma optical emission spectrometry, scanning electron microscope, and X‐ray diffraction are used to analyze the composition, surface morphology, and crystal structure of the electrodes. The XRD analysis reveals that the Pd‐Sn/SS electrode has a crystalline nature when a Pd molar ratio >0.5 while an amorphous phase is detected over a Pd molar ratio (≤0.5). The electrochemical nitrate reduction is carried out in a 0.1 M HClO4 / 8 mM NaNO3 solution for 5 h using electrodes prepared in deep eutectic solvent (DES) system. The Pd0.93Sn0.07/SS electrode shows the best catalytic performance in terms of high nitrate conversion of 97%, N2 selectivity of 88%, and N2 yield of 86% compared to counter electrodes. These findings demonstrate a considerable impact of the electrode preparation process on nitrogen conversion, selectivity, and yield.

Optimization and continuous-flow operation of electrochemically mediated selective formate separation by polyvinyl ferrocene/graphene oxide electrodes

Electrochemical carbon dioxide (CO2) reduction is a promising route to convert intermittent renewable energy into fuels and valuable chemical products. Separation of CO2 reduction products by ion-selective electrochemical technology may play a decisive role in the pursuit of commercially viable CO2 reduction processes. Selective separation of formate, one of the main CO2 reduction products, is assessed in the present study in an electrochemical flow cell with symmetric redox-active polyvinyl ferrocene (PVF) functionalized graphene oxide (GO) electrodes. First, experimental parameters such as the PVF/GO ratio, sonication time, and ultrasonic amplitude, were optimized in the electrode preparation process to improve the formate adsorption efficiency on a lab scale (1 × 2 cm electrodes) under static conditions. The electrochemical and morphological characteristics of the electrodes were investigated by cyclic voltammetry and scanning electron microscopy. To demonstrate continuous-flow operation, an electrosorption flow cell (8 × 8 cm) providing inline measurements was constructed. The flow cell results showed selectivity at > 5.5 toward the removal of formate from an electrolyte containing perchlorate at an excess of 30 times the normal value. The performance of the electrosorption cell was also tested using a mixture of methanol, ethanol, formate, and acetaldehyde produced in a CO2 reduction electrolyzer. In this demonstration, formate separation was achieved with a selectivity of > 4.0. The results suggest that the optimized design of the electrochemical cell and operation conditions of the flow platform pave the way for scaling up selective formate separation with PVF/GO electrodes.

In-situ generated Co2P nanoparticle-embedded porous carbon membrane as an advanced hybrid electrode for high-areal-capacitance supercapacitors

Hybridizing powdery carbons with transition metal phosphides (TMPs) can effectively address the issues of sluggish kinetics and volume expansion associated with TMPs in supercapacitors (SCs). However, the practical use of powdery TMPs/carbon materials in SCs is limited by tedious electrode preparation process, unfavorable performance, and inferior cycling stability. Herein, we develop carbon membrane-based hybrid electrodes (Co2P@CTF) by the direct carbonization of Co-containing tofu (TF) aerogel prepared by coagulating soybean proteins using Co2+ ions. During carbonization, the cross-linked protein frameworks were transformed into a porous, mechanically strong, and conductive carbon matrix, whereas the Co species were in situ self-phosphorized to be highly dispersed carbon-coated Co2P nanoparticles without using external phosphorus sources. The best Co2P@CTF electrode (Co2P@CTF-1000) demonstrates a high areal capacitance (Ca) of 2.44 F cm−2 at 1.0 mA cm−2. Moreover, a symmetric SC assembled with Co2P@CTF-1000 deliveries a Ca of 1.33 F cm−2 at 1.0 mA cm−2, achieves an energy density of 90 μWh cm−2 at a power density of 699.4 μW cm−2, and retains a 104.8% capacitance with a nearly unit coulomb efficiency at 10 mA cm−2 after 50000 cycles. This study offers an effective strategy towards carbon membrane-supported TMPs hybrid electrodes based on the direct self-phosphorization mechanism for the practical applications in SCs.

Overlithiation lithium-rich Mn-based oxide as cathode pre-lithiation agent towards high-energy-density batteries

Huge active Li+ loss in the initial cycle owing to the formation of solid electrolyte interface (SEI) layer of anode restrict the enhancement of high-energy–density lithium-ion batteries (LIBs). Here, a method by reducing surface oxygen vacancies of lithium-rich manganese-based oxide (LRMO) to obtain huge number of irreversibly active Li+ for the application of cathode pre-lithiation, which is highly adaptive to electrode preparation process with excellent air stability, is proposed. Through modulating different lithium ratios, Li2-x(Mn2/3Ni1/3)xO2 (x = 0.67, LR-2) with fewer oxygen vacancies is synthesized. By simply adjusting cell voltage, it exhibits different electrochemical properties to match the requirements of different LIB cathode. When used as an agent to a LiFePO4 cathode, LR-2 can further enhance the capacity of cells, due to its “donor” lithium-ion capacity (244.1 mAh/g) and exceptional cyclic performance. By coupling with LiNi0.5Mn1.5O4, LR-2 provides high lithium compensation efficiency (320.0 mAh/g), while also releasing reversible capacities of 98.5 mAh/g, achieving a balance between pre-lithiation capacities and reversible discharge capacities. As a consequence, the LiNi0.5Mn1.5O4|graphite full cell containing LR-2 exhibits a reversible capacity of 123.3 mAh/g, 47% greater than the counterpart without LR-2, and significantly better cyclic performance. This study introduces a novel approach to design cathode pre-lithiation agent with Li-rich oxides for high-energy–density LIBs.

A scalable slurry process to fabricate CuZr amorphous alloy with hybrid lithiophilic oxides for lithium metal anode

The lithium metal is the most promising candidate anode for the next-generation lithium batteries, its wide-scale application will be accelerated if its electrode preparation process is feasible and compatible with the current electrode preparation approach used in the battery industry. Here the powder form of CuZr metallic glass was applied for lithium metal anode application, which was one-step chemically dealloying treated in the hydrofluoric acid solution prior to usage. The as-prepared CuZr powder (CuZr-D*) displays enlarged specific surface area with hybrid lithiophilic CuxO/ZrO2 oxides decorated on the surface, which is capable to induce homogenous nucleation, promote fast reaction kinetics, and improve the reversible lithium plating/stripping process. Moreover, the CuZr in powder form makes it easily accessible with the slurry-based electrode preparation process currently applied in battery industry. As a result, the CuZr-D* based electrode demonstrates good symmetric cell performance of 1500 h at 1.0 mA cm−2/1.0 mAh cm−2, high coulombic efficiency of 97.5% after 200 cycles at 0.5 mA cm−2/1.0 mAh cm−2, cyclic stability and rate capability of full cells. This work supports the potential feasibility of amorphous alloy powder for lithium metal battery application.

Aqueous Supramolecular Binder for High-Performance Lithium-Sulfur Batteries.

Developing an advanced electrode structure is highly important for obtaining lithium sulfur (Li-S) batteries with long life, low cost, and environmental friendliness. Some bottlenecks, such as large volume deformation and environmental pollution caused by the electrode preparation process, are still hindering the practical application of Li-S batteries. In this work, a new water-soluble, green, and environmentally friendly supramolecular binder (HUG) is successfully synthesized by modifying natural biopolymer (guar gum, GG) with HDI-UPy (cyanate containing pyrimidine groups). HUG can effectively resist electrode bulk deformation through a the unique three-dimensional nanonet-structure formed via covalent bonds and multiple hydrogen bonds. In addition, abundant polar groups of HUG have good adsorption properties for polysulfide and can inhibit the shuttle movement of polysulfide ions. Therefore, Li-S cell with HUG exhibits a high reversible capacity of 640 mAh g-1 after 200 cycles at 1C with a Coulombic efficiency of 99%.

Rational design of hierarchically nanostructured NiTe@CoxSy composites for hybrid supercapacitors with impressive rate capability and robust cycling durableness

The hierarchically nanostructured NiTe@CoxSy composites are constructed on a foamed nickel substrate by a two-step electrode preparation process. Structural characterization shows the dense growing of CoxSy nanosheets around NiTe nanorods forms a hierarchical nanostructure which possesses synergetic effects from both compositional and structural complementarity, more pathways for ion/electrolyte transport, richer redox active sites, and better conductivity. Thanks to the rational design of this hierarchical structure, NiTe@CoxSy delivers a high areal capacitance of 7.7F cm−2 at 3 mA cm−2 and achieves the improved capacitance retention of 97.9% after 10,000 cycles. Of particular importance is the successful fabrication of NiTe@CoxSy//activated carbon hybrid supercapacitors. This hybrid device has a wide operating voltage window, high areal energy density of 0.48 mWh cm−2 at 2.55 mW cm−2, impressive rate capability of 62.3% even after a 20-fold increase of the current density, and a 115.1% of initial capacitance retention after 15,000 cycles. Meanwhile, two tandem such hybrid devices can easily drive a pair of mini fans or light up a heart-like pattern assembled by 10 red LEDs. These experimental results not only demonstrate that the hierarchically nanostructured NiTe@CoxSy composites can serve as a prospective candidate electrode; but also develop a novel strategy about how to achieve high-performance stockpile equipment by rationale designing a desirable nanostructures.

In Situ Preparation of High-Performance Silicon-Based Integrated Electrodes Using Cross-Linked Cyclodextrins.

The strategy of material modification for improving the stability of silicon electrodes is laborious and costly, while the conventional binders cannot withstand the repeated massive volume variability of silicon-based materials. Hence, there is a demand to settle the silicon-based materials' problems with green and straightforward solutions. This paper presents a high-performance silicon anode with a binder obtained by in situ thermal cross-linking of citric acid (CA) and β-cyclodextrin (β-CD) during the electrode preparation process. The Si electrode with a binder synthesized by the one-pot method shows excellent cycling performance. It maintains a specific capacity of 1696 mAh·g-1 after 200 cycles at a high current of 0.5 C. Furthermore, the carbonylation of β-CD to carbonyl-β-CD (c-β-CD) introduced better water solubility, and the c-β-CD can generate multidimensional connections with CA and Si, which significantly enhances the specific capacity to 1941 mAh·g-1 at 0.5 C. The results demonstrate that the prepared integrated electrode facilitates the formation of a stable and controllable solid electrolyte interface layer of Si and accommodates Si's repeated giant volume variations.

3D printed smart glove with pyramidal MXene/Ecoflex composite-based toroidal triboelectric nanogenerators for wearable human-machine interaction applications

Self-powered sensors based on triboelectric nanogenerators (TENGs) have shown great advantages in human-machine interactions. However, the complex preparation process and high cost of conventional electrodes hinder their practical implementation. In this study, we develop a wearable self-powered toroidal triboelectric sensor (STTS) with a pyramidal structure for self-powered human-machine interactions based on an extremely simplified design strategy. 3D printing technology is employed to fabricate pyramidal arrays on MXene/Ecoflex nanocomposites, thus providing a comfortable space between the finger skin and the negatively charged layer to overcome the space requirements in traditional triboelectric-based sensors. Furthermore, the developed pyramidal structure of the nanocomposite and flexible conductive fabric electrodes assembled with 3D-printed gloves based on the flexible TPU material maintained the wearability of the sensing system. The flexible and simplified single-electrode design strategy of the STTS can be easily worn on the human hand for comfortable and natural interaction with machines and devices. The high peak-to-peak voltage (19.91 V), high sensitivity (0.088 VkPa−1), and wide pressure detection range (0–120 kPa) enable the generation of high-quality output signals for the accurate detection of various finger movements exhibiting great potential for use in human-machine interaction applications in next-generation artificial intelligence and interactive devices.

Cross-linking chemistry enables robust conductive polymeric network for high-performance silicon microparticle anodes in lithium-ion batteries

Low-cost silicon microparticles (SiMPs) are more promising anode materials towards practical implementation due to their higher volumetric energy density and less side reactions than Si nanoparticles. However, SiMPs always suffer from extremely dramatic mechanical fracture caused by volume expansion during cycling, and hence a far inferior cycle stability to Si nanoparticles. Herein, a highly cross-linked 3D conductive polymeric network, consisting of amino-functionalized long single-wall carbon nanotubes (SCNT–NH2–L) and poly(acrylic acid)/sodium carboxymethyl cellulose, has been prepared via esterification and amidation reactions during electrode preparation process. Benefiting from limiting effect and stress-dissipation provided by the unique network, it can keep complete electrode structure and ensure good electrical connection between broken Si particles during cycling. Meanwhile, the newly formed ester groups in the network can greatly enhance the reaction kinetics of silicon for superior Li+ storage. As a result, the as-prepared SiMPs anode delivers an ultrahigh initial discharge capacity of 3861.4 mAh g−1 at 100 mA g−1 and a superior cycle stability with high capacity retention of 74.3% from 20th to 200th cycle at 2000 mA g−1. Our work provides a novel but simple stress-dissipation strategy to enable the stable operation of silicon microparticle in lithium-ion batteries.

An Experimental Investigation on Polarization Process of a PZT-52 Tube Actuator with Interdigitated Electrodes.

The manipulator is the key component of the micromanipulator. Using the axial expansion and contraction properties, the piezoelectric tube can drive the manipulator to achieve micro-motion positioning. It is widely used in scanning probe microscopy, fiber stretching and beam scanning. The piezoceramic tube actuator used to have continuous electrodes inside and outside. It is polarized along the radial direction. There are relatively high polarization voltages, but poor axial mechanical properties. A new tubular actuator is presented in this paper by combining interdigitated electrodes and piezoceramic tubes. The preparation, polarization and mesoscopic mechanical properties were investigated. Using Lead Zirconate Titanate (PZT-52) as a substrate, the preparation process of interdigitated electrodes by screen printing was studied. For initial polarization voltage determination, the local characteristic model of the actuator was extracted and the electric field was analyzed by a finite element method. By measuring the actuator’s axial displacement, we measured the actuator’s polarization effect. Various voltages, times and temperatures were evaluated to determine how polarization affects the actuator’s displacement. Optimal polarization conditions are 800 V, 60 min and 150 °C, with a maximum displacement of 0.88 μm generated by a PZT-52 tube actuator with interdigitated electrodes. PZT-52 tube actuators with a continuous electrode cannot be polarized under these conditions. The maximum displacement is 0.47 μm after polarization at 4 kV. Based on the results, the new actuator has a more convenient polarization process and a greater axial displacement from an application standpoint. It provides technical guidance for the preparation and polarization of the piezoceramic tube actuator. There is potential for piezoelectric tubular actuators to be used in a broader range of applications.

Improved iridium/iridium oxide pH electrode through supercritical treatment

• Supercritical conditions promoted hydration and redox reactions. • Supercritical treatment optimized the structure of IROF on Ir/IrOx pH electrode. • Treated electrodes have fast pH response, good linearity, and high stability. pH measurement has received extensive attention from researchers in numerous fields including medical diagnostics agriculture, food industry, marine, and chemical engineering. Owing to their electrode stability, drift degree, and preparation process, iridium/iridium oxide electrodes are considered as the most promising candidate for pH detection under these conditions. In this study, iridium/iridium oxide electrodes were fabricated by thermal cycling oxidation method. The relationship between the electrode structure and performance was investigated and discussed. To study the influence of supercritical treatment, the as-prepared electrodes were treated at 35 MPa and 400 °C for 3 h. After examining their pH response, the supercritically treated electrodes exhibit better performance than the untreated iridium/iridium oxide electrodes. The structural changes of the treated electrodes were investigated by Raman spectroscopy, X-ray photoelectron spectroscopy, cyclic voltammograms and scanning electron microscopy. The results revealed the important changes in the iridium oxide film of the electrode after supercritical treatment, such as its morphology, chemical bond, valence state, and defects, which collaborated to achieve its improved performance.

Scalable Dry-Pressed Electrodes Based on Holey Graphene.

ConspectusHoley graphene (hG) is a structural derivative of graphene with arrays of through-thickness holes of a few to tens of nanometers in diameter, randomly distributed across the nanosheet surfaces. In most bulk preparation methods, the holes on hG sheets are preferentially generated from the pre-existing defects on graphene. Therefore, contrary to intuitive belief, hG is not necessarily more defective than the intact graphene. Instead, it retains essential parent properties, including high electrical conductivity, high surface area, mechanical robustness, and chemical inertness. Furthermore, the added holey structural motif imparts unique properties that are not present in unmodified graphene, making hG advantageous in numerous applications such as sensing, membranes, reinforcements, and electrochemical energy storage. In particular, the presence of holes enhances the mass transport through the nanosheet plane and thus significantly reduces tortuosity. This difference is a key advantage for using hG in energy storage applications where the transport of ions through the thickness becomes more hindered as the electrode thickness increases to meet practical energy density requirements.An unexpected discovery is that the holes of the hG sheets enable the dry hG powder to be directly compressed into robust monoliths. hG not only can be pressed into monoliths by itself but also can host other electrochemically active materials as a compressible matrix. This important yet unique property, which is not available for other carbon materials including intact graphene, significantly broadens the application horizon in energy storage applications. With the dry compressibility, electrodes with ultrahigh mass loading and thus ultrahigh areal capacity may be conveniently fabricated without toxic solvents or parasitic binders, which are required in conventional slurry-based approaches for electrode fabrication. The dry-press electrode preparation process can be completed within minutes regardless of mass loading. In comparison, high-mass-loading electrodes for advanced battery chemistries using conventional fabrication methods often need stringent and time-consuming process control. hG can also be combined with electrochemically active battery materials while maintaining dry compressibility. This has allowed the unprecedented, convenient manipulation of a wide variety of thick electrode compositions and architectures, which provides not only outstanding performance but also new physical insights for various battery chemistries.In this Account, we first present some basic observations on the dry compressibility of hG as well as the mechanistic investigations from atomistic modeling rationalizing this unique property. We then showcase the applications of neat and composite dry-pressed hG electrodes for various energy storage platforms including supercapacitors, lithium (Li) ion batteries, Li-O2 batteries, and Li-S/Se batteries. The preparation and performance of thick electrodes with practical mass loadings and unique electrode architecture manipulation, both enabled by the dry compressibility of hG, are highlighted and discussed.

Emerging carbon-based flexible anodes for potassium-ion batteries: Progress and opportunities

In recent years, carbon-based flexible anodes for potassium-ion batteries are increasingly investigated owing to the low reduction potential and abundant reserve of K and the simple preparation process of flexible electrodes. In this review, three main problems on pristine carbon-based flexible anodes are summarized: excessive volume change, repeated SEI growth, and low affinity with K+, which thus leads to severe capacity fade, sluggish K+ diffusion dynamics, and limited active sites. In this regard, the recent progress on the various modification strategies is introduced in detail, which are categorized as heteroatom-doping, coupling with metal and chalcogenide nanoparticles, and coupling with other carbonaceous materials. It is found that the doping of heteroatoms can bring the five enhancement effects of increasing active sites, improving electrical conductivity, expediting K+ diffusion, strengthening structural stability, and enlarging interlayer spacing. The coupling of metal and chalcogenide nanoparticles can largely offset the weakness of the scarcity of K+ storage sites and the poor wettability of pristine carbon-based flexible electrodes. The alloy nanoparticles consisting of the electrochemically active and inactive metals can concurrently gain a stable structure and high capacity in comparison to mono-metal nanoparticles. The coupling of the carbonaceous materials with different characteristics can coordinate the advantages of the nanostructure from graphite carbon, the defects and vacancies from amorphous carbon, and the independent structure from support carbon. Finally, the emerging challenges and opportunities for the development of carbon-based flexible anodes are presented.

Flexible self-supporting electrode for high removal performance of arsenic by capacitive deionization

Capacitive deionization (CDI) technology has promising applications for the removal of arsenic from micro polluted water. The selection of electrode materials and the fabrication of electrodes are the core parts of the CDI technology. In this paper, the structure of graphene was modulated by inserting carbon quantum dots to form three-dimensional (3-D) rGO/NCDs electrode material and electrospinning method was applied to fabricate monolithic mesh self-supporting electrodes with excellent electrochemical and structure properties. In the experiments of arsenic removal, the rGO/NCDs electrode achieved an electrosorption capacity of 15.07 mg g−1 at 1.0 V, increasing by 29.5% compared with that of rGO electrode. In addition, the model fitting analysis of the experimental data showed that arsenic removal was consistent with pseudo-first-order kinetic model and Langmuir adsorption isotherm. The thermodynamic model suggested that electrosorption was a spontaneous exothermic process. The intraparticle diffusion model further revealed the diffusion mechanism of arsenic removal by CDI electrodes. In conclusion, the prepared flexible self-supporting rGO/NCDs electrode with high electrosorption capacity provided a new idea for the electrode preparation process and further promoted the large-scale application of CDI technology.

Facile synthesis of CoMn2O4@CoMn2S4 core-shell nanoclusters@nanosheets as advanced hybrid capacitor electrode materials

In this work, a novel CoMn2O4@CoMn2S4 core-shell nanocluster@nanosheet was successfully grown onto Ni foam via a hydrothermal reaction, which omitted the addition of a binder and conductive additive and the need for a complicated electrode preparation process. CoMn2S4 nanosheets as "shells" were found to be uniformly distributed on the surface of CoMn2O4 nanoclusters as "cores" to form a typical core-shell structure. These structures possess a high specific surface area and abundant active sites, which not only shorten the transmission path for electrons and ions, but also prevent collapse of the structure, thus improving its cycling stability. The specific capacity of CoMn2O4@CoMn2S4 is 1542.0 C g−1 at a current density of 1 A g−1, which is 3.1 times higher than that obtained for CoMn2O4. Moreover, CoMn2O4@CoMn2S4 shows excellent electrochemical cycling performance, and the specific capacity retention rate for CoMn2O4@CoMn2S4 reaches 95.81% after 5000 cycles at a current density of 20 A g−1. The specific energy of the CoMn2O4@CoMn2S4 reaches 44.30 Wh kg−1 at a specific power of 774.98 W kg−1. Therefore, the CoMn2O4@CoMn2S4//AC device shows excellent practical application capability.

A novel 3D MnNi2O4@MnNi2S4 core-shell nano array for ultra-high capacity electrode material for supercapacitors

In this work, a novel 3D MnNi2O4@MnNi2S4 core-shell nano array was successfully grown on nickel foam (NF) via in-situ growth method, which omitted the addition of binder and conductive additive and the complicated electrode preparation process. The MnNi2O4@MnNi2S4 possesses a unique nanorod@nanosheet core-shell structure, which can provide abundant active sites near the electrode interface for rapid electrochemical reaction, so the MnNi2O4@MnNi2S4 electrode materials exhibit high specific capacitance and excellent electrochemical properties. It is worth noting that the specific capacitance of the MnNi2O4@MnNi2S4 reaches 3578.57 F g−1 at the current density of 1 A g−1, and 1009.52 F g−1 at the current density of 20 A g−1. When the current density is 15 A g−1, the specific capacitance retention rate reaches 93.1% after 5000 cycles, showing good cycling performance. Moreover, the MnNi2O4@MnNi2S4//AC asymmetric device also exihibits low leakage current and excellent self-discharge characteristics. So, the MnNi2O4@MnNi2S4 is an excellent electrode material for supercapacitors.