Improved Electrode Materials Research Articles

Synthesis, fabrication, and performance evaluation of lanthanum doped nickel cobalt ferrite electrode for supercapacitors in energy storage applications

The escalating demand for high-quality energy storage devices has become a paramount concern in the contemporary scenario. Despite the potential of supercapacitors for high-quality energy storage, developing sustainable and improved electrode materials remains a challenge. This work investigates the synthesis and characterization of a novel optimally lanthanum-doped nickel cobalt ferrite, for its potential application in supercapacitors. The synthesized nano ferrite is utilized in a two-electrode system as a symmetrical supercapacitor device. The obtained morphological and electrochemical results of both two and three-electrode systems confirm their suitability for effective deployment in supercapacitor electrodes. A high specific capacitance of 706 F/g and energy density of 152.9 Wh/g is obtained for the fabricated device with a retention capacity of 86 % even after 10,000 cycles. The electrochemical results are also validated using an electrical method. The exploration of this lanthanum-doped nano ferrite is expected to be a suitable candidate for the fabrication of supercapacitor electrodes for augmented energy storage performance.

Chemo-mechanical failure mechanisms of the silicon anode in solid-state batteries.

Silicon is a promising anode material due to its high theoretical specific capacity, low lithiation potential and low lithium dendrite risk. Yet, the electrochemical performance of silicon anodes in solid-state batteries is still poor (for example, low actual specific capacity and fast capacity decay), hindering practical applications. Here the chemo-mechanical failure mechanisms of composite Si/Li6PS5Cl and solid-electrolyte-free silicon anodes are revealed by combining structural and chemical characterizations with theoretical simulations. The growth of the solid electrolyte interphase at the Si|Li6PS5Cl interface causes severe resistance increase in composite anodes, explaining their fast capacity decay. Solid-electrolyte-free silicon anodes show sufficient ionic and electronic conductivities, enabling a high specific capacity. However, microscale void formation during delithiation causes larger mechanical stress at the two-dimensional interfaces of these anodes than in composite anodes. Understanding these chemo-mechanical failure mechanisms of different anode architectures and the role of interphase formation helps to provide guidelines for the design of improved electrode materials.

(Invited) Challenges and Opportunities of Alkaline Water Electrolysis

Alkaline water electrolysis has been operated on 100+ MW scale in the 20th century powered by hydropower. Because of this history, the technology is often regarded as a mature technology with limited improvement potential that is less suitable for flexible operation. As a result most research efforts in the field of water electrolysis focus on other technologies such as PEM, solid oxide and AEM electrolysis. This is a pity, since alkaline electrolysis is very well positioned to be deployed on large-scale for the production of green hydrogen in the coming decades. Main reason is that in contrast to the other technologies, alkaline technology does not depend on scarce and/or expensive noble or rare earth metals. Also, the use of a diaphragm instead of a membrane makes the technology more robust.Yet, to enable the large-scale deployment of alkaline electrolysis for production of green hydrogen from renewable electricity certain technical challenges need to be overcome. These include safety challenges associated with rare scenarios where hydrogen and oxygen can mix, flexibility limitations associated with gas crossover limiting the minimum load of the plant, and durability challenges resulting from frequent shutdowns of electrolyzers. In principle all these challenges can be overcome by rigorous plant design and the selection of suitable diaphragm and electrode materials, but they do require research efforts.Next to that, there is room to significantly drive down the costs of green hydrogen produced by alkaline electrolyzers. Traditionally, alkaline electrolyzers have been operated at low current densities of 0.2-0.4 A cm-2. This was related to the high ohmic drop associated with the use of thick diaphragms and non-zero-gap cell designs. Presently, advanced alkaline electrolyzers are under development that can operate at significantly higher current densities (~1 A cm-2) through the use of thinner diaphragms, zero-gap cell designs and improved electrode materials. Operation at these increased current densities increases the output of alkaline electrolyzers and in this way can effectively reduce the costs and footprint of water electrolysis plants. Yet, the use of thinner diaphragms and advanced electrodes also creates new challenges, since they can lead to increased gas crossover and vulnerability to impurities and reverse currents that occur upon the shutdown of electrolyzers.In this presentation the fundamentals of alkaline water electrolysis will be discussed. These include overpotentials and durability of electrode coatings, the role of electrolyte impurities, ohmic resistance, gas crossover through the diaphragm, the influence of operating temperature and pressure, the effect of bubbles, and the influence stray currents resulting from the manifold design. These fundamentals will be translated into a potential design for the perfect alkaline electrolyzer.Figure:alkaline electrolyzers operational in Norway in 1931. Source: Norsk Industriarbeidermuseum Figure 1

Carbon-Shielded Selenium-Rich Trimetallic Selenides as Advanced Electrode Material for Durable Li-Ion Batteries and Supercapacitors.

In order to achieve a sustainable future, researchers must continue to research improved electrode materials. Considering the high electronic conductivity, versatile redox activity, and enhanced energy storage performance, nanostructures have been employed as a novel electrode material for high-performance lithium-ion batteries (LIBs) and supercapacitors. Herein, carbon-coated selenium-rich trimetallic selenide (Cu2 NiSnSe4 @C) nanoparticles (NPs) as an efficient electrode material in energy storage devices are prepared. The prepared core-shell Cu2 NiSnSe4 @C NPs electrode is employed as ananode material for LIBs, which demonstrated a high reversible specific capacity of 988.46mA h g-1 over 100 cycles at 0.1 A g-1 with good rate capability. Additionally, the core-shell Cu2 NiSnSe4 @C NPs electrode exhibited an outstanding capacity of 202.5mA h g-1 at 5 A g-1 even after 10 000 cycles. Exploiting the synergistic characteristics, the core-shell Cu2 NiSnSe4 @C NPs material is also investigated as a battery-type electrode for hybrid supercapacitors. The assembled hybrid supercapacitor with Cu2 NiSnSe4 @C NPs and activated carbon showed excellent rate capability including high power (5597.77W kg-1 ) and energy (64.26Wh kg-1 ) densities. Considering the simple synthesis and enhanced energy storage properties, carbon-coated selenium-rich trimetallic selenide can be used as a durable electrode material for practical energy storage devices.

An in-plane supercapacitor obtained by facile template method with high performance Mn–Co sulfide-based oxide electrode

Designing in-plane supercapacitors with high electrode materials selectivity is an indispensable approach to improve electrochemical performance. In this work, a facile template method was employed to fabricate in-plane supercapacitors. This template method could select any electrochemical active materials as electrode materials of in-plane supercapacitors. Hence, a high electrochemical performance material Mn–Co LDO-2S with optimized metal-sulfur bonds proportion and abundant sulfur vacancies was employed as electrode material of symmetrical in-plane supercapacitor (SPS). SPS exhibits excellent electrochemical performance finally, and has considerable area energy density 55.0 μWh cm−2 with an area power density of 0.7 mW cm−2. As a result, introducing sulfur atoms and sulfur vacancies are efficient approaches to improve electrode materials’ electrochemical performance, and template method that proposed in this work is a promising approach to widen selectivity of in-plane supercapacitors’ electrode materials.

Correlating wavelength dependence in LiMn2O4 cathode photo-accelerated fast charging with deformations in local structure

The growth in electrified transportation has benefited from the massive worldwide research efforts used to discover and improve electrode materials and electrolytes. Nevertheless, lithium-ion batteries still suffer from a slow-charging limitation. Recently, it has been demonstrated that white light illumination of LiMn2O4 provokes faster charging, improving the kinetics of delithiation without the use of nanostructured active materials. In this work, we probe the mechanism of photo-accelerated fast charging and show that Mn d-d electronic transitions occurring under red light illumination are largely responsible for the increased charging rate. It is further demonstrated through X-ray absorption spectroscopy methods that LiMn2O4 Mn–Mn bond distances shorten after d-electron excitation. The shrinkage in the crystal volume beneficially contributes to delithiation kinetics by lowering the resistance to lithium-ion conduction. Advanced materials that can absorb light to modulate their structure may provide us with a new mechanistic pathway to pursue for increasing charge transfer rates.

Hard Carbon Particle Size and Mass Loading Influence on Sodium Ion Battery Rate Performance

Sodium ion batteries (SIBs) are considered one of the most promising next generation electrochemical energy storage systems. Owing to their potential lower cost, superior sustainability and improved safety compared to the current lithium-based technology, SIBs have the potential to dominate the future stationary energy storage and niche electric vehicle application markets1. However, to meet the requirements for practical implementation, research on improved electrode materials is necessary to further increase the cell’s energy and power density2.Primary particle size, morphology and the resulting electrode microstructure play a critical role in the rate performance and cycle life of the cell. Understanding and optimising electrode microstructure and design is therefore of vital importance in the scale-up and commercialisation of any new active material chemistry. The electrode tortuosity is a critical parameter determining the reduction of transport properties (i.e. conductivity and diffusivity) due to electrode microstructural hinderance.In this work, the effect of mass loading and particle size on the tortuosity is investigated for both positive (layered oxide) and negative (hard carbon) electrodes, aiming at understanding its effect on the cell’s rate performance. Tortuosity is obtained by using two different methods, specifically, (i) fitting electrochemical impedance spectroscopy (EIS) data by using a transmission line model (TLM) under blocking conditions to a symmetrical cell3; and (ii) simulating diffusive flow on binarized scanning electron microscopy (SEM) images using the TauFactor MATLAB application4.The data obtained indicate a relatively small effect of hard carbon particle size on rate performance when considering d50 particle sizes of 9μm and 5μm. On the other hand, mass loading significantly influences the rate performance and is subsequently mirrored by a linear increase in ionic resistance Rion (see figure 1). Despite the increase in Rion, the effect of on tortuosity remains largely independent of mass loading for the electrodes tested. References (1) Hasa, I.; Mariyappan, S.; Saurel, D.; Adelhelm, P.; Koposov, A. Y.; Masquelier, C.; Croguennec, L.; Casas-Cabanas, M. Challenges of Today for Na-Based Batteries of the Future: From Materials to Cell Metrics. J. Power Sources 2021, 482, 228872. https://doi.org/10.1016/j.jpowsour.2020.228872. (2) Vaalma, C.; Buchholz, D.; Weil, M.; Passerini, S. A Cost and Resource Analysis of Sodium-Ion Batteries. Nat. Rev. Mater. 2018, 3, 18013. https://doi.org/10.1038/natrevmats.2018.13 https://www.nature.com/articles/natrevmats201813#supplementary-information. (3) Landesfeind, J.; Hattendorff, J.; Ehrl, A.; Wall, W. A.; Gasteiger, H. A. Tortuosity Determination of Battery Electrodes and Separators by Impedance Spectroscopy. J. Electrochem. Soc. 2016, 163 (7), 1373–1387. https://doi.org/10.1149/2.1141607jes. (4) Cooper, S. J.; Bertei, A.; Shearing, P. R.; Kilner, J. A.; Brandon, N. P. TauFactor: An Open-Source Application for Calculating Tortuosity Factors from Tomographic Data. SoftwareX 2016, 5, 203–210. https://doi.org/10.1016/J.SOFTX.2016.09.002. Figure 1

Developing New Quinone Based Electrodes for Electrochemical Carbon Capture

The need for cost-effective carbon capture technology is rapidly increasing. To limit the global temperature increase to 1.5 degrees within the next century, the level of CO2 mitigation needs to be increased drastically [1]. Current technology, i.e., amine scrubbing, provides several challenges which limit their deployment: high regeneration energy, high operational costs and degradation at high temperatures [2]. An electrochemical approach avoids large energy losses and can selectively uptake CO2 by utilizing redox-active organic molecules. To compete with conventional chemical scrubbing, the electrochemical cell needs high power density, high CO2 uptake and long cycle stability. Redox-active molecules such as quinone-based molecules have been utilized in this area however suffer from low cycling stability due to organic molecules leaking into the electrolyte [3,4]. Quinone-polymer electrodes have shown a high efficiency for CO2 capture however are prone to quinone degradation and low active-material mass [5]. Here we present our work on a new class of quinone-based electrodes for electrochemical CO2 capture, and explore their electrochemistry in the presence and absence of CO2 and quantify their CO2 uptake capacities. This work paves the way for the design and discovery of improved electrode materials for electrochemical CO2 capture. The Intergovernmental Panel on Climate Change (2018), Global Warming of 1.5 degrees. Available at: https://www.ipcc.ch/sr15/ (Accessed: 10 December 2021)Rahimi, M., Zucchelli, F., Puccini, M. and Alan Hatton, T., 2020. Improved CO2 Capture Performance of Electrochemically Mediated Amine Regeneration Processes with Ionic Surfactant Additives. ACS Applied Energy Materials, 3(11), pp.10823-10830.Apaydin, D., Głowacki, E., Portenkirchner, E. and Sariciftci, N., 2014. Direct Electrochemical Capture and Release of Carbon Dioxide Using an Industrial Organic Pigment: Quinacridone. Angewandte Chemie International Edition, 53(26), pp.6819-6822.Ranjan, R., Olson, J., Singh, P., Lorance, E., Buttry, D. and Gould, I., 2015. Reversible Electrochemical Trapping of Carbon Dioxide Using 4,4′-Bipyridine That Does Not Require Thermal Activation. The Journal of Physical Chemistry Letters, 6(24), pp.4943-4946.Voskian, S and Hatton, T., 2019. Faradaic Electro-swing Reactive Adsorption for CO2 Capture. Energy and Environmental Science, 12(12), pp.3530-3547

Recent Research of NiCo2O4/Carbon Composites for Supercapacitors

Supercapacitors have played an important role in electrochemical energy storage. Recently, researchers have found many effective methods to improve electrode materials with more robust performances through the increasing volume of scientific publications in this field. Though nickel cobaltite (NiCo2O4), as a promising electrode material, has substantially demonstrated potential properties for supercapacitors, its composites usually show much better performances than the pristine NiCo2O4. The combination of carbon-based materials and NiCo2O4 has been implemented recently due to the dual mechanisms for energy storage and the unique advantages of carbon materials. In this paper, we review the recent research on the hybrids of NiCo2O4 and carbon nanomaterials for supercapacitors. Typically, we focused on the reports related to the composites containing graphene (or reduced graphene oxide), carbon nanotubes, and amorphous carbon, as well as the major synthesis routes and electrochemical performances. Finally, the prospect for the future work is also discussed.

Soluble tetraaminophthalocyanines indium functionalized graphene platforms for rapid and ultra-sensitive determination of rutin in Tartary buckwheat tea

Herein, a soluble tetramine phthalocyanine indium-decorated reduced graphene oxide (rGO-InTAPc) nanocomposite was prepared via non-covalent functionalization and used to construct a novel electrochemical sensor for sensitive determination of rutin in Tartary buckwheat tea. The rGO-InTAPc as an improved electrode material can significantly increase the electroactive surface area and electron transfer capacity. Moreover, the electrochemical response can be dramatically expanded by the enrichment effect of rutin through the adsorption of π-π stacking. Under optimized conditions, the rGO-InTAPc sensor displayed a linear dependence for rutin concentration ranging from 0.005 to 100 μM with a detection limit of 2.0 nM ( S/N = 3). The proposed sensor with excellent selectivity and reproducibility was quantitatively validated in commercially available Tartary buckwheat tea with rutin level ranging of 9.06–13.87 mg/g, which results were highly consistent with these of HPLC. This strategy of rutin detection will address a long-standing analytical challenge to establishing facile and sensitive methods for quality monitoring in tea drinks. • A soluble phthalocyanine-graphene nanocomposite (rGO-InTAPc) was prepared. • This nanocomposite was used as a novel sensing material for rutin monitoring. • rGO-InTAPc can increase surface area and electron transfer capacity of electrode. • π-π stacking between rGO-InTAPc and rutin can achieve highly sensitive detection. • Sensitive rGO-InTAPc sensor was quantitatively validated in Tartary buckwheat tea.

Enhancing the performance of carbon electrodes in supercapacitors through medium-temperature fluoroalkylation

Medium-temperature fluoroalkylation of microporous activated carbons (ACs) with 1,1,1,2-tetrafluoroethane is presented. Supercapacitor (SC) electrodes based on the fluoroalkylated ACs showed enhanced specific capacitance and high specific energy in electrolytes, either aqueous potassium hydroxide solution or tetraethylammonium tetrafluoroborate-acetonitrile solution. We found the largest increase in the specific capacitance, up to 89 F g–1, and in the specific energy, up to 7.5 Wh kg–1, at the voltage of 1.5 V. The specific capacitance of the SC electrode based on the sample prepared at 350 °C increases by a factor of ~ 2–3 × for certain scan rates in the organic electrolyte. The fluoroalkylated ACs have good electrochemical stability in the tested model systems. We associate the registered enhanced SC parameters with an increase in the total fluorine content and high specific surface areas of the carbon electrode materials. The surface “isolated fluorine” formed during fluoroalkylation at 300–400 °C ensures the production of improved electrode materials for SC applications. Fluoroalkylation is a simple and cost-effective method of improving the specific capacitance of carbon-based SC electrodes.

Nanostructured nickel-cobalt oxide and sulfide for applications in supercapacitors and green energy production using waste water

Abstract With the advancement in technology, the demand for green energy production and storage is increasing year by year. To meet the increasing demand for green energy, there has been continuous research in a bid to find better materials and efficient ways to store energy. Supercapacitors continue to show a promising green energy storage capacity with their modified and improved electrode materials, which show better electrochemical properties. Transition metals such as Fe, Mo, Ni, etc. based materials have shown great potential for electrode materials in supercapacitors, electrocatalysts for water splitting, and urea oxidation reaction (UOR). In this work, nanostructured nickel‑cobalt oxide and nickel‑cobalt sulfide were synthesized using a facile hydrothermal method for their applications in a supercapacitor, water splitting, and urea oxidation reaction. It was observed that the properties of nickel‑cobalt oxide improved significantly after converting it to nickel‑cobalt sulfide. The energy storage capacity of nickel‑cobalt sulfide was significantly enhanced compared to nickel‑cobalt oxide. Additionally, nickel‑cobalt sulfide showed an overpotential of 282 mV, while nickel‑cobalt oxide displayed an overpotential of 379 mV to generate a current density of 10 mA/cm2, towards oxygen evolution reaction. After the introduction of 0.33 M urea, the potential for oxidation of urea for both nickel‑cobalt oxide and nickel‑cobalt sulfide was reduced significantly.

Lithium Ions Batteries Electrodes Materials, Design, Outlook and Future Perspectives

With the rapid growth of lithium-ion batteries (LIBs) industry and market, it is important to develop LIBs with higher capacities, stability and lifespan. However, challenges like low conductivity, solid electrolyte interface formation and electrode cracking now are in the way, which are closely related to electrode deficiency. Hence, to obtain better performance, the main orientation is to improve electrode materials’ morphological structure. Better porosity, stability and conductivity of anode and cathode materials tangibly improve the performance of LIBs including coulombic efficiency, safety and cyclic lifespan. This review paper will combine current challenges, commonly used and emerging electrode materials together with battery testing methods and their market trend to provide a big picture about LIBs

Sensitive acetaminophen electrochemical sensor with amplified signal strategy via non-covalent functionalization of soluble tetrahydroxyphthalocyanine and graphene

A new amplified signal strategy for acetaminophen (AC) electrochemical sensor was explored by soluble zinc tetrahydroxyphthalocyanine-reduced graphene oxide nanocomposite as an improved electrode material via non-covalent functionalization. The electrochemical signal of AC was amplified by the remarkably increased electroactive surface area of the nanocomposite-modified glassy carbon electrode. Moreover, the synergistic enrichment effect can be achieved by the adsorption of π-π stacking and hydrogen bonding of hydroxyl groups. The prominent electrocatalytic effect toward AC oxidation were examined systematically on the proposed sensor and a sensitive and selective electroanalytical method for AC was developed. Under optimized conditions, the electrochemical response of the sensor exhibited a linear dependence on the concentration of AC ranging from 0.03 to 100 μM and 100 to 800 μM with a detection limit of 10 nM (S/N = 3). The proposed sensor with excellent selectivity, reproducibility and long-term stability for AC sensing was successfully applied for AC determination in drug formulation and human urine samples.

Anisotropic Growth of Al‐Intercalated Vanadate by Tuning Surface Hydrophilicity for High‐Rate Zn‐Ion Storage

Aqueous zinc‐ion battery (ZIB) cathodes with high rate performance are still lacking due to the sluggish kinetics of Zn2+ insertion. Herein, preferential 2D spreading surface is constructed on conductive carbon paper (C‐paper) supports by disclosing hierarchical porous structures. The unique surface hydrophilicity enables anisotropic growth of layered Al‐intercalated vanadate nanobelts with high‐aspect ratios. As a cathode of ZIB, the preintercalated vanadate nanobelts with a large interlayer spacing (1.38 nm) exhibit high specific capacities and excellent rate performance (534 and 221 mA h g−1 at 1 and 20 A g−1, respectively). Moreover, chemically resistant HfO2 layers are applied by atomic layer deposition to prevent effectively the cathode from degradation, leading to an outstanding cycling stability (88% retention at 1000 cycle). The anisotropic growth of 2D electrode materials by tuning the surface hydrophilicity provides an effective pathway for designing improved electrode materials for various energy storage technologies.

Surfactant decorated polypyrrole-carbon materials composites electrodes for supercapacitor

The current effort discuss the fabrication of improve electrode materials for supercapacitor comprise of surfactant doped polypyrrole‑carbon materials composites integrated with graphene, amine functionalized multiwalled carbon nanotubes and hybrid carbon assembly. The spectroscopic characterizations demonstrate the establishment of a well-built state of charge swap complex among surfactant doped polypyrrole and carbon materials that disclose the occurrence of polymer‑carbon phases and promote well-built polarization. The electrodes are assembled in the three electrode cell configuration with graphite sheet current collector. The composite SDBSDPPy-HC holds a specific capacitance of 1086 F g−1 at scan rate 5 mV s−1 in 6 M KOH electrolyte solution. SDBSDPPy-HC exhibit only 10% losses in specific capacitance over 2500 cycles i.e. 90% preservation of specific capacitance at a current density 1 A g−1.

Honeycomb-like open-edged reduced-graphene-oxide-enclosed transition metal oxides (NiO/Co3O4) as improved electrode materials for high-performance supercapacitor

• Honeycomb reduced graphene oxide (HOrGO) serves as an efficient conductive network. • The HOrGO/TMOs (NiO/Co 3 O 4 ) hybrids were synthesized via microwave-assisted method. • The micron-sized (~100 μm) open edges of HOrGO NSs hold the NiO/Co 3 O 4 nanoparticles. • The HOrGO/TMOs hybrids deliver specific capacitance 910 F/g at scan rate 20 mV/s. • The HOrGO/TMOs hybrids exhibited high retention with stabile performance. Honeycomb-like open edges reduced graphene oxide nanosheets (HOrGO NSs) filled with transition metal oxides (TMOs) as NiO/Co 3 O 4 nanoparticles (NPs) has been synthesized by a simple and cost-effective microwave irradiation method. The microwave irradiation assisted synthesized HOrGO filled with NiO/Co 3 O 4 NPs (HOrGO/TMOs) hybrids exhibits high specific capacitance with improved cycling stability as excellent electrode materials for supercapacitors (SCs). The HOrGO NSs contains high surface area (~570 m 2 g −1 ) due to highly exfoliated nanostructure comprising open edges enriched morphology. In HOrGO/TMOs hybrids, the several micron-sized (~100 μm) open edges of HOrGO NSs holds the NiO/Co 3 O 4 NPs with finely separated thin few-layer graphene NSs. The structural/ morphological analysis of synthesized HOrGO NSs and HOrGO/TMOs hybrids were extensively characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), Raman spectra, thermogravimetric analysis (TGA) and Brunauer-Emmett-Teller (BET) surface area. The HOrGO/TMOs hybrids deliver high specific capacitance of 910 F g −1 and high robust cycling stability with capacitance retention as 89.9% after continuous 2000 cycles. The proposed mechanism explain the microwave irradiation assisted formation of HOrGO/TMOs hybrids and provides a general and low-cost approach to synthesized high quality graphene hybrids materials for SCs application.

Synthesis of mesoporous Co(OH)2 nanostructure film via electrochemical deposition using lyotropic liquid crystal template as improved electrode materials for supercapacitors application

Here we report synthesis of mesoporous structure containing two different phases of Co(OH)2 by different routes. The β-Co(OH)2 film and mesoporous α-Co(OH)2 powder synthesized using electrochemical deposition and chemical reduction methods, respectively using lyotropic liquid crystal (LLC) templates. These synthesized mesoporous β-Co(OH)2 film and α-Co(OH)2 powder were utilized as electrode materials for supercapacitors (SCs)application. The surface structure/morphology of these synthesized materials were analyzed by scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDS), transmission electron microscope (TEM), wide/low-angle X-ray diffraction (XRD) and Raman spectroscopy. The as-synthesized mesoporous β-Co(OH)2 film and mesoporous α-Co(OH)2 powder contain particles size in the range of 270–300 nm and 70–90 nm, respectively. For application as electrode in SCs, mesoporous β-Co(OH)2 film on FTO reveals enhanced electrochemical performance as compared to mesoporous α-Co(OH)2 powder in 1 M KOH electrolyte as high specific capacitance with a significant tremendous long-term cyclic stability. The specific capacitance of mesoporous β-Co(OH)2 film was 605 F/g at scan rate 10 mV/s and superior cyclic stability as capacitance retention of 94.4% over 2000 cycles. Uniform and homogeneous Co(OH)2 nanoparticles inside film enhance the electrochemical performance for SCs due to easy penetration and access of KOH electrolyte inside mesoporous structure. The reported synthesis method provides a suitable and fast approach to synthesize other kind of metal hydroxide mesoporous structure for electrode purpose for different energy storage devices.

Sulfur-doped Bi2Se3 Monolayer as Potential electrode Materials for Mg-ion batteries

Magnesium-ion batteries (MIBs) are a front-runner among the alternative battery technologies suggested to substitute the state-of the-art lithium-ion batteries (LIBs). Searching for proper electrode materials for MIBs is critical for the development of MIBs. Using density functional theory (DFT) calculations, Bi2Se3 monolayers with sulfur-doping as potential electrode materials for MIBs were investigated in this work. The effect of S doping on adsorption and diffusion behaviors of Mg ions was mainly studied. The results showed that Mg atoms first prefer to occupy the H sites of both perfect and S-doped Bi2Se3 surfaces. Doping of S atom reduces the corresponding adsorption energy and diffusion barrier of Mg on the surface. The present results give expectation of excellent battery performance by S doping and it is one way to improve electrode materials for the fast charging/discharging of MIBs.

Multiple Active Sites: Lithium Storage Mechanism of Cu-TCNQ as an Anode Material for Lithium-Ion Batteries.

Recently, carboxylate metal-organic framework (MOF) materials were reported to perform well as anode materials for lithium-ion batteries (LIBs); however, the presumed lithium storage mechanism of MOFs is controversial. To gain insight into the mechanism of MOFs as anode materials for LIBs, a self-supported Cu-TCNQ (TCNQ: 7,7,8,8-tetracyanoquinodimethane) film was fabricated via an in situ redox routine, and directly used as electrode for LIBs. The first discharge and charge specific capacities of the self-supported Cu-TCNQ electrode are 373.4 and 219.4 mAh g-1 , respectively. After 500 cycles, the reversible specific capacity of Cu-TCNQ reaches 280.9 mAh g-1 at a current density of 100 mA g-1 . Mutually validated data reveal that the high capacity is ascribed to the multiple-electron redox conversion of both metal ions and ligands, as well as the reversible insertion and desertion of Li+ ions into the benzene rings of ligands. This work raises the expectation for MOFs as electrode materials of LIBs by utilizing multiple active sites and provides new clues for designing improved electrode materials for LIBs.