Binder-free Electrode Materials Research Articles

Synergistic effect of co-sputtered tungsten-titanium nitride as electrode material for efficient hybrid supercapacitors

The dawn of bimetallic transition metal nitrides has attracted considerable interest as battery grade electrode material for potential energy storage applications. In addition, it is essential to investigate binder-free processes to improve the performance of the fabricated electrodes. In this study, binder-free tungsten‑titanium nitrides (W-TiN) are deposited through RF/DC magnetron co-sputtering onto the conducting nickel foam (NF). SEM, EDX and X-ray diffraction are exploited to investigate surface morphology, elemental composition, and structural properties of sputtered materials. The W-TiN electrodes are characterized through electrochemical investigation in half-cell configuration. The tested W-TiN electrode is further utilized with activated carbon (AC) electrode to develop hybrid supercapacitor device W-TiN//AC. The hybrid device revealed a maximum energy density (Es) of 88.8 Wh/kg and power density (Ps) 1700 W /kg. To further understand the mechanism of hybrid devices, the capacitive and diffusive contributions are computed using linear and quadradic models. This study provides a new direction to integrate co-sputtered binder-free electrode materials and devices for large scale production of advanced hybrid energy storage devices.

Rational design of the binder-free polythiophene nanofibers deposited nickel foam for the high-performance aqueous asymmetric supercapacitor

Development of the binder-free electrode materials and employing in the supercapacitor is the essential footstep for high energy storage. The present study highlights the cost-effective synthesis strategy for the binder-free growth of the amorphous polythiophene nanofibers over the nickel foam substrate. The presence of functional bonds like CC, C-H, and C-S has confirmed the deposition of the polythiophene nanofibers on the nickel foam, while elemental mapping analysis detected the uniform distribution of Carbon and Sulfur elements over nanofibers. The surface structure of the polythiophene is transformed from nanofibers to a wire-like structure as the result of the monomer concentration variation. The optimized polythiophene film exhibited the highest areal capacitance of 1263.2 mF/cm2 at 2 mA/cm2 with 90.03% capacitance retention after 5000 cycles. Moreover, the aqueous asymmetric device (PTh//AC) is fabricated which delivered 31.5 F/g at 10 mA/cm2. The highest specific energy of PTh//AC device was 6.3 Wh/kg. Also, it showed good retention capability with 82.3% retention. Based on these results, the present investigation provides the performance metrics of the polythiophene nanofibers and highlights the potential utilization of the polythiophene-based supercapacitor in practical energy storage systems.

N, O-codoped porous carbon fiber cloth synthesized by molecular dispersed CaCl2·6H2O in situ activation for high performance supercapacitors

In this study, a nitrogen/oxygen co-doped carbon fiber cloth with a hierarchical porous structure was synthesized by one-step carbonization and in situ activation method and acted as binder-free electrode materials for supercapacitors. Cotton fiber cloth served as the carbon precursor, while molecular dispersed CaCl2·6H2O and urea functioned as activator and N dopant, respectively. The influence of molar concentration of CaCl2·6H2O and urea on the microstructure and capacitive performance of the resulting products were investigated. CaCl2·6H2O has an expansion effect on pores, resulting in reduction of micropores. Hence, the specific surface area of the resulting porous carbon increased first and then decreased with the increase of CaCl2·6H2O concentration. In addition, the erosion of NH3 and CO2 (produced by the decomposition of urea) at high temperature on the surface of the samples promoted the formation of porous structure. Urea plays the dual role of doping and activation agent. The morphology and structure analysis shown that the activated samples exhibited hierarchical pore structure, large specific surface area, and high heteroatom content. The optimal sample NAC-20 exhibited good capacitive performance, including high specific capacitance of 260.9 F g−1 at 0.1 A g−1 and good rate performance. Moreover, the symmetric supercapacitor exhibited a maximum energy density and power density of 16.2 Wh kg−1 and 19.0 kW kg−1, respectively, in 6 M KOH electrolyte. In this work, a green, low-cost molten salt activation method was proposed to synthesis biomass derived porous carbon materials for energy storage devices.

Fabrication of Nd2S3 based rGO nanohybrid via hydrothermal route and evaluation of capacitive features toward supercapacitor application

The two-dimensional metal sulphide acts as potent electrodes for supercapacitors; instead, they require further cycle stability and performance rate improvements before they can be used in real-world applications. Improved supercapacitor efficacy can be achieved by developing binder-free and hierarchical carbon nanohybrid electrode materials. Herein, we report the fabrication of a binder-free Nd2S3-based rGO nanohybrid electrode via the hydrothermal route for energy-saving equipment. Several analytical tools were used to determine the physiochemical features of the all-synthesized electrode materials. Several electrochemical tests, such as cyclic voltammetry and galvanostatic charge–discharge (GCD), were utilized to determine the pseudocapacitive nature of fabricated materials. The Cs from GCD of Nd2S3/reduced GO nanohybrid (782.46 F g−1) was greater than Nd2S3 (332.69 F g−1) and reduced GO (470.18 F g−1). Furthermore, the Nd2S3/reduced GO electrode shows excellent cyclic stability with a rate capability of 90 % over 5000th cycles. It facilitates the perfect connection for fast electrolyte ion diffusion between the electrolyte and electrode surface. Incorporating rGO into rare earth metal sulphide significantly enhances the capacitive characteristics of the electrode due to providing a larger surface area and enriching active zones. These findings suggest that supercapacitors may be constructed using binder-free Nd2S3/reduced GO electrodes, resulting in better electrochemical characteristics.

Enhanced performances of NiCoSe2 electrode coated with Ag nanoparticles by magnetron sputtering for the applications of asymmetric supercapacitors

In this work, a binder-free energy-storage electrode material of Ag nanoparticles coated nickel cobalt selenide (NiCoSe2) on Ni foam (NF) was first proposed. Wherein, NiCoSe2 was synthesized by one-step hydrothermal method using ascorbic acid as reductant, and the coating of Ag nanoparticles on NiCoSe2 were performed by magnetron sputtering method. The specific surface area was greatly increased due to the deposited Ag nanoparticles, and in this way the impedance of the electrode decreased, and the electrochemical properties were enhanced. When the magnetron sputtering time is 10 s, Ag/NiCoSe2 electrode exhibits the most excellent performances. However, further increase of sputtering time may result in the over cover on NiCoSe2, with great deterioration in electrochemical behavior. Single NiCoSe2 electrode possesses an area capacitance of 1600.7 mF cm−2 at a current density of 2 mA cm−2, while Ag/NiCoSe2 electrode could reach up to 2280 mF cm−2. The asymmetric supercapacitor (ASC) assembled by Ag/NiCoSe2 and activated carbon (AC) electrodes shows a high energy density of 0.171 mWh cm−2 as well as a power density of 17.340 mW cm−2, and the cyclic stability remains at 90.1% after 4000 cycles, which is superior to 83.7% of the NiCoSe2 single electrode.

Urchin-like structure and nanowire arrays of NiCo2O4/NiCoSe2 as a binder-free electrode material for high-performance supercapacitor

Hybrid structures targeted at high-performance electrochemical applications circumvent great challenges. Nanostructures with high porosity facilitating electrolyte penetration and providing fast ion and electron transfer are suitable candidates for constructing hybrid structured electrode materials. Here in, an architecture composed of nanowires and urchin-like structures of NiCo2O4 covered by NiCoSe2 nanosheets is successfully constructed on Ni foam through hydrothermal treatment in association with electrodeposition. The fabricated NiCo2O4/NiCoSe2 hybrid electrode demonstrates areal capacitance of 12.09 F cm-2 at current density of 5 mA cm-2, surpassing that of pristine NiCo2O4. Furthermore, the electrode evidences cycling stability with 87.6% capacitance retention over 3000 cycles. An asymmetric hybrid supercapacitor, assembled by the NiCo2O4/NiCoSe2 as a positive electrode and activated carbon as a negative electrode, represents areal capacitance of 3.07 F cm-2 at 5 mA cm−2. The as-fabricated device with excellent cycling stability (90.9% capacitance retention over 2000 cycles) delivers an energy density of 66.13 Wh kg-1 at a power density of 233 W kg-1. Our results convey a promising synthesis method of the core-shell structure of NiCo2O4/NiCoSe2 nanowire arrays for application in supercapacitors.

Synergy unleashed: NiMoO4/WO3/NF nanoflowers elevate for supercapacitor performance

Nickel molybdate oxide (NiMoO4) and tungsten trioxide (WO3) are becoming progressively more commonly suitable as electrode materials for supercapacitors owing to their chemical stability, peculiar layered structure, and significant capacitance. Unfortunately, most of the published works based on NiMoO4 and WO3-based electrodes show lower electrochemical performance due to their poor conductivity and fast capacitance fading. Here, we reveal methods to build hierarchical nanoflowers formed from NiMoO4/WO3/NF for the very first time, which enhances the supercapacitor's electrochemical performance. The potential benefits of the NiMoO4/WO3/NF suitable to be a binder-free electrode material for supercapacitor utilization seem very fascinating. In comparison to the pristine NiMoO4/NF (263.75 F g−1) and WO3/NF (197.91 F g−1) materials, the NiMoO4/WO3/NF nanocomposite exhibits remarkable precise capacitance of 429.46 F g−1 at 1 A g−1, exceptional reliability alongside over 89.9 % the capacitance preservation after 10000 cycles, and low charge transfer resistance. NiMoO4/WO3/NF nanocomposite exhibits outstanding electrochemical performance and is mainly allocated to the beneficial synergistic effect of its peculiar structure, which may offer additional routes for the movement of electrons and maximize the efficiency of the utilization of the electrode material. The findings imply that these kinds of nanocomposite electrodes have a lot of promise for application in energy storage.

Graphene nanoflake-self stabilized dispersion polymerized PANI hybrids as efficient, binder-free electrode materials for high-performance flexible symmetric supercapacitors

In this study, we prepared hybrid electrodes of self-stabilized dispersion polymerized (SSDP) polyaniline (PANI) and graphene nanoflakes by a facile solution intercalation approach. Unlike the conventional electrode preparation methods, the SSDP PANI dispersion was prepared by adopting the secondary doping method. The preparation of hybrid electrodes by a unique combination of these methods eliminates the use of binders and imparts excellent electrochemical properties to these electrodes due to synergistic effects. The optimized electrode (PG 2:1) demonstrates a specific capacitance of 454.9 F g−1 at a current density of 0.5 A g–1 and the symmetric supercapacitor using this electrode, achieved an energy density of 33.2 Wh kg−1 at a power density of 1 kW kg−1. Furthermore, even at a high-power density of 10 kW kg−1, the device delivers an energy density of 25.4 Wh kg−1. Interestingly, the symmetric supercapacitor retains 89.2 % of its initial capacitance even after 10,000 continuous charge–discharge cycles at a current density of 5 A g–1. The performance of these devices was also tested for different bending angles and was found to exhibit excellent stability. The superior performance of this hybrid electrode offers significant potential for the development of efficient binder-free flexible supercapacitors for portable and wearable devices.

Fabrication of binder-free mixed sulphide/PANI nanocomposite based electrode for supercapacitor application

In a pursuit to satisfy the rising energy demand, researchers to create novel, environmentally safe electrode materials for several energy storage devices. The electrochemical performance could be compromised as a result of the polymer binders employed in the electrode coating procedure. Binder-free electrode materials accelerate electron transport pathways by providing enough room to accommodate the active material's large volume changes during charging and discharging. Lower electronegativity of sulphur compared to oxygen provides increased flexibility in the structure of transition metal sulphides which makes them stand out as the promising candidates in the search for innovative electrode materials. Likewise, although PANI possess high conductivity and specific capacitance, it's ineffective to be used in the purest form for practical applications owing to its inability to retain the capacitance when it undergoes multiple charging/discharging cycles. In this work, we describe the development of binder-free Cu-Mn mixed sulphide and its nanocomposite with PANI on carbon fibre paper (CP) substrates. Characterization techniques such as XPS, FE-SEM along with elemental mapping helped in understanding the successful formation of the nanocomposite. In contrast to pure PANI and Cu-Mn mixed sulphide at the same current density in a neutral 1 M Na2SO4 electrolyte, the composite of Cu-Mn mixed sulphide and PANI demonstrated an enhanced areal capacitance of 550.95 mF cm−2 at 1 mA cm−2. Incorporating PANI with Cu-Mn mixed sulphides has not only improved their capacitance but also reduced the rate at which pristine PANI's capacitance degrades when subjected to a greater number of charge/discharge cycles which is reflected in the enhanced capacity retention property of the nanocomposite, wherein the composite maintained 99.02% of its original capacitance at a current density of 10 mA cm−2 than of pure PANI on CP substrates.

Engineering of binder-free cobalt carbonate hydroxide hydrate nanostructure for high-performance hybrid supercapacitors

Cobalt-based binder-free electrode materials, such as Co(CO3)0.5(OH)⋅0.11H2O nanowires (Co@Urea) and Co(OH)F microcrystals (Co@NH4F), were synthesized on a nickel foam substrate by a traditional hydrothermal method using urea and ammonium fluoride (NH4F) as the complexing reagents. The nanowire structure of the Co@Urea electrode promoted efficient charge transfer and high electrochemical active centers. The Co@Urea electrode exhibited a large specific capacity (693.0 C g−1 at 1 A g−1), better rate performance (50.8 % after 20 A g−1), and exceptional cyclic durability (84.0 % capacity retention after 10,000 cycles) compared to Co@NH4F electrode in a three-electrode configuration. A hybrid supercapacitor device was fabricated with Co@Urea as the cathode and activated charcoal as the anode, exhibiting high specific energy and specific power of 53.8 Wh kg−1 and 799.9 W kg−1, respectively. Furthermore, this hybrid device shows excellent long-term stability with 88.2 % capacity retention after 10,000 cycles at a current density of 40 A g−1. This study proposes developing binder-free cobalt-based compounds for electrochemical energy storage applications.

Preparation of flexible and binder-free lignin-based carbon nanofiber electrode materials by electrospinning in aqueous system

Abstract Lignin, as a widely distributed, renewable and environmentally friendly source of carbon, could been utilized for carbon nanofibers to not only maximize the usage of resources, but also expand the energy-related opportunities. In this research, flexible lignin-based carbon nanofibers are prepared by electrospinning lignin nanofibers in a new green aqueous solution of lignin and polyvinyl alcohol (PVA), which is then characterized by physical and chemical characterizations. The results reveal that optimal carbonization temperature of 800 °C shows great improvements on the structural properties of lignin-based carbon nanofibers, which can be applied as binder-free electric double layer capacitor (EDLC) electrodes with good flexibility. The 2032 type button battery has a superior electrochemical performance with a large specific capacitance of 217.2 F g−1 at a 0.2 A g−1 current density, and remarkable cyclic stability of 94.9 % capacitance retention even after 10,000 charge and discharge cycles, due to the abundance of mesoporous volume and large microporous surface area of lignin-based carbon nanofiber electrodes carbonized in 800 °C.

Synergistic coupling of MnS/Ni3S2 and Co(OH)2 nanosheets as binder-free electrode materials for asymmetric supercapacitors with enhanced performance

The fabrication of electrode materials with a high specific capacitance is essential for the development of enhanced performance supercapacitors. A novel binder-free electrode material, composed of MnS/Ni3S2 and Co(OH)2, was synthesized on nickel foam by hydrothermal, sulfuration, and electrodeposition techniques. The MnS/Ni3S2 exhibited a unique flower-like structure, resulting in a high specific capacitance of 1780 F g−1 at 1 A/g. By optimizing the synthesis conditions through several characterization and electrochemical tests, the MnS/Ni3S2@Co(OH)2 composite was obtained, which displayed an ultrahigh specific capacitance of 2495 F g−1 at 1 A/g and a capacitance retention rate of 86.1% after 5000 cycles at 10 A/g in three-electrode system. The synergistic coupling of MnS/Ni3S2 and Co(OH)2, along with the conductive nickel foam substrate, donated towards the excellent electrochemical performance. Furthermore, the MnS/Ni3S2@Co(OH)2//AC asymmetric supercapacitor (ASC) device was constructed with MnS/Ni3S2@Co(OH)2 as positive electrode, activated carbon (AC) as negative electrode and 1 M KOH solution as electrolyte, demonstrated a high energy density of 68.6 Wh kg−1 at 750 W kg−1 and excellent cycle stability with 91.2% capacitance retention after 10,000 cycles at 15 A/g. The outstanding electrochemical properties observed in both the pre-electrodeposition and post-electrodeposition samples indicate the effectiveness of reasonable design and construction of composite as a pathway for producing electrode materials with exceptional performance.

Hydrothermally modified tin(II) sulfide binder-free battery grade electrode for supercapattery

In the initiative of diminishing the current research gap related to the limited electrochemical performance of supercapacitor, various hybrid supercapacitor combinations were introduced. However, the energy storage capacity and power are still limited. Thus, a new type of hybrid device known as supercapattery was introduced by combining a battery grade electrode with capacitive type electrode to improve the energy and power densities. In the midst of material exploration on battery grade materials suited for supercapattery, transition metal sulfides have grabbed intense attention for their excellent electrochemical properties and conductivity. Herein, a novel tin (II) sulfide (SnS) binder free electrode materials were synthesized through hydrothermal method as a battery grade material for supercapattery. In this work, the electrodes were fabricated by differing metal precursor to reducing agent ratios (1:2,1:4, and 1:6) followed by fine tuning the physio-chemical characteristics of SnS by differing hydrothermal temperature. The synthesized materials were structurally characterized using X-ray diffraction analysis. The surface morphology and particle size were investigated through field emission scanning electron microscopy (FESEM) and high-resolution transmission electron microscopy (HRTEM). The SnS fabricated using ratio 1:4 at 150 °C exhibited fascinating specific capacity/specific capacitance (325.20Cg−1/668.45Fg−1) with 89.73% rate capability. The SnS was then combined with activated carbon (AC) to produce supercapattery. The fabricated supercapattery demonstrated fascinating stability of 98.61% over 15,000 cycles with maximum energy and power density of 8.77 Wh kg-1 and 3,095.20 W kg−1, respectively.

A sequential template electrodeposition anodization and in situ aniline electropolymerization-based facile electrochemical synthesis strategy

Herein, we propose a facile continuous electrochemical synthesis strategy to build 3D hierarchical hybrid conductive networks based on sequential template electrodeposition-anodization and in-situ aniline electropolymerization. It was implemented in a tin system to prepare a 3D tin skeleton with micron-scale features using the hydrogen bubble dynamic template method, followed by electrochemical anodization to achieve nanoscale modulation. This well-designed 3D hierarchical metal oxide framework was used for the in-situ electropolymerization of aniline, preserving the hierarchical morphological features while establishing large conductive networks for ultrafast electron transport and enhancing the structural stability of tin dendrites. Regulation of the hierarchical morphologies promotes material surface reactivity, increases the electrochemically active sites, and improves the ion diffusion kinetics, thus solving the “dead surface” problem in the energy storage process. Such multifaceted synergistic strategies of structural modulation and functional hybridization have opened up new ways to design efficient binder-free hybrid electrode materials.

Preparation of sustainable and binder-free electrode materials for high energy asymmetric supercapacitor applications: A cleaner alternative

Herein, we demonstrate a pioneering method for repurposing one of the most abundant and noxious weeds (Parthenium hysterophorus or PH) derived ultrahigh surface area carbon as capacitive electrode and design high performance asymmetric supercapacitor with leveraging ternary metal oxides (TMO) (Ni–Co–Mn–O or TMO-1 and Ni–Co–Zn–O or TMO-2) as binder-free pseudocapacitive positive electrodes to improve the performance and efficiency of supercapacitors. Furthermore, the ternary metal oxides (TMO-1 and TMO-2) were synthesized using a one-pot hydrothermal method, followed by annealing. In a three-electrode configuration, both TMO-1 and TMO-2 exhibited remarkable capacitances. At a current density of 0.5 A/g, a total stored charge of 557.23 C/g and 628.22 C/g was obtained for the TMO-1 and TMO-2, respectively. The asymmetric construction using PH-900-K as the negative electrode and TMO-1 or TMO-2 as the positive electrode demonstrated a maximum energy density of 49.29 Wh/kg for the TMO-1//PH-900-K configuration. While the TMO-2//PH-900-K configuration exhibited a maximum energy density of 70.86 Wh/kg.

Fabricating process-electrochemical property correlation of laser-scribed graphene and smartphone-based electrochemical platform for portable and sensitive biosensing

Laser-scribed graphene (LSG), a promising electrode material has attracted special research interest in recent years. Here, the fabricating process-electrochemical property correlation of laser-scribed graphene (LSG) devices was discussed emphatically and a pertinent optimization was performed to achieve better electroanalytical performance. Experiment results indicated that the laser scribing technique possessed great process latitude and reducing laser power and scribing speed facilitated fabricating high-quality graphene electrodes. Benefiting from its binder-free 3D porous network structure and high active/geometric area ratio, the optimized LSG electrode was superior to the screen-printed carbon electrode (SPCE) on electrochemical performance in the [Fe(CN)6]3-/4- redox system. Integrating the LSG electrode with a homemade hand-held detector, a portable electrochemical sensing platform with smartphone readout was developed. It realized a specific detection of H2O2 (linear range: 0.02–3.4 mM, sensitivity: 24.56 μA mM−1 cm−2), glucose (linear range: 0.04–4.0 mM, sensitivity: 16.35 μA mM−1 cm−2) by directly decorating biological enzymes without artificial redox mediator and featured a satisfactory comprehensive performance. The constructed immunosensor for tumor necrosis factor-α exhibited a wide linear range (2–500 pg mL−1) and a 4.3-fold enhancement in sensitivity compared with that of SPCE. With satisfactory selectivity, reproducibility, and sensitivity, the developed smartphone-based electrochemical sensing platform held great promise in accurate detection on the spot. This work also provided a significant reference for tailoring binder-free carbonaceous electrode materials toward the desired application.

Non-stationary electrochemical synthesis of flexible binder-free hybrid electrode materials for supercapacitors

The rapid development of flexible energy storage devices, such as supercapacitors, requires the creation of appropriate electrode materials with high capacitance and cycling stability. In this work, we propose a new method for the synthesis of hybrid electrode materials by depositing transition metal oxides on carbon fabrics using non-stationary electrolysis. An amorphous deposit with inclusions of Mo4O11, MoO3, MoO2, Mo8O23, Mo9O26, V2O5, and MnO2 nanocrystals was obtained on the carbon surface. The hybrid was used as a binder-free electrode and had a capacitance of 498 mF∙cm–2 in 2 M KOH electrolyte at a current density of 4 mA∙cm–2. This value is comparable to or even higher than the values reported for similar materials. A long-term test of the two-electrode system showed a capacitance retention of 62% over 10,000 cycles. The power density and energy density of the hybrid electrode are 15∙10–4 W∙cm–2 and 6∙10–7 Wh∙cm–2, respectively. The synthesized metal oxide/carbon hybrids are promising electrode materials for symmetrical supercapacitors with alkaline electrolytes.

Heterogeneous nucleation and growth of interlaced CuO nanosheets on porous nickel foams as binder-free electrode material

The monoclinic CuO has a natural tendency to grow into sheet-like structures from alkaline solutions without the need for any specialized reaction conditions or structural directing agents. We demonstrate this growth habit of CuO by heterogeneously nucleating it onto Ni foam substrate from just the ammonical solutions of Cu salts. The growth kinetics were found to be fast and, dense, interlaced thin films with an average sheet width of 20 nm can be grown by simply controlling the degree of supersaturation of the solution. Strongly adhered films with thicknesses up-to 5 μm were deposited from three different Cu salt solutions. Due to faster growth kinetics, growth time has little effect on both the film and nanosheet thickness. Detailed structural and compositional characterizations of the CuO nanosheets were made using FESEM, HRTEM, SAED, XRD and, XPS. The utility of the grown CuO nanosheets is demonstrated as a ready to use electrode for electrochemical supercapacitors. Specific capacitance in excess of 498 F/g was calculated from the Galvanostatic charge–discharge measurements collected at a current density of 0.5 A/g.

Novel porous CoS1.097@carbon nanofibers as flexible and binder-free anode material for sodium-ion batteries

Transition metal sulfides (TMSs) have received numerous attention as anode materials for sodium-ion batteries because of the high theoretical capacity. So far, the Na-storage performance of TMSs is still unsatisfactory due to the structural degeneration that induced by the volume change upon redox process. Herein, a novel flexible and binder-free anode material of porous CoS1.097@carbon nanofibers was facilely constructed by means of the electrospinning, carbonization and sulfidation processes. The porous CoS1.097@carbon nanofibers display unique structure with CoS1.097 nanoparticles confined into porous N-doped carbon nanofibers, and can provide sufficient active sites, high electrical conductivity, reduced ion diffusion distance, abundant ion migration pathways, desirable voids for alleviating the volume variation, and rigid structural stability for efficient Na-storage. In consequence, the flexible and binder-free electrode material delivers high initial discharge capacity, enhanced rate capability and long-term cycling life. Besides, intrinsic diffusion and electrochemical storage behavior of Na+ ions were emphatically disclosed. This work paves a facile route for the synthesis of flexible and binder-free TMSs-based anode materials, promoting the practical application of wearable sodium-ion batteries.

Facile Synthesis of Battery-Type CuMn2O4 Nanosheet Arrays on Ni Foam as an Efficient Binder-Free Electrode Material for High-Rate Supercapacitors.

The development of battery-type electrode materials with hierarchical nanostructures has recently gained considerable attention in high-rate hybrid supercapacitors. For the first time, in the present study novel hierarchical CuMn2O4 nanosheet arrays (NSAs) nanostructures are developed using a one-step hydrothermal route on a nickel foam substrate and utilized as an enhanced battery-type electrode material for supercapacitors without the need of binders or conducting polymer additives. X-ray diffraction, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) techniques are used to study the phase, structural, and morphological characteristics of the CuMn2O4 electrode. SEM and TEM studies show that CuMn2O4 exhibits a nanosheet array morphology. According to the electrochemical data, CuMn2O4 NSAs give a Faradic battery-type redox activity that differs from the behavior of carbon-related materials (such as activated carbon, reduced graphene oxide, graphene, etc.). The battery-type CuMn2O4 NSAs electrode showed an excellent specific capacity of 125.56 mA h g-1 at 1 A g-1 with a remarkable rate capability of 84.1%, superb cycling stability of 92.15% over 5000 cycles, good mechanical stability and flexibility, and low internal resistance at the interface of electrode and electrolyte. Due to their excellent electrochemical properties, high-performance CuMn2O4 NSAs-like structures are prospective battery-type electrodes for high-rate supercapacitors.