Shell Electrode Research Articles

A facile one-step route to synthesize of novel porous reduced graphene oxide@nickel sulfide (rGO@Ni3S2) core shell nanostructures for high-performance supercapacitor electrodes

In the last decade, there has been significant interest in the use of supercapacitors with high power density and cycle stability in a wide range of applications. Graphene-based hybrid electrodes are considered a very promising option for supercapacitors owing to the synergistic effects they exhibit. In this study, we provide a novel and efficient method for synthesising a core-shell nanocomposite consisting of reduced graphene oxide (rGO) wrapped around nickel sulphide (Ni3S2) using a one-step hydrothermal process. The resulting rGO@Ni3S2 composite exhibits excellent performance as a supercapacitor electrode while also being cost-effective. As a promising supercapacitor electrode, a relatively high specific capacitance of 1052.5 Fg−1 at current density of 1 Ag−1 in 1 mol.L−1 KOH aqueous solution, along with good cycling stability (with a 94.5 % retention rate after 10,000 cycles) were demonstrated for the rGO@Ni3S2 core shell composite electrode. In addition, excellent electrochemical performances were also demonstrated for the asymmetric supercapacitor (ASC) by using rGO@Ni3S2 as the cathode and activated carbon, respectively. The fabricated ASC showed with a high energy density of 61.9 Whkg−1 at the power density of 585.7 W kg−1. Such high performance of rGO@Ni3S2 core shell electrode can enrich the prospects for future practical applications in energy storage.

Study on the performance of biochar prepared from walnut shell and traditional graphene electrode plate in the treatment of domestic sewage in microbial fuel cells.

As a new pollutant treatment technology, microbial fuel cell (MFC) has a broad prospect. In this article, the devices assembled using walnut shells are named biochar-microbial fuel cell (B-MFC), and the devices assembled using graphene are named graphene-microbial fuel cell (G-MFC). Under the condition of an external resistance of 1,000 Ω, the B-MFC with biochar as the electrode plate can generate a voltage of up to 75.26 mV. The maximum power density is 76.61 mW/m2, and the total internal resistance is 3,117.09 Ω. The removal efficiency of B-MFC for ammonia nitrogen (NH3-N), chemical oxygen demand (COD), total nitrogen (TN), and total phosphorus (TP) was higher than that of G-MFC. The results of microbial analysis showed that there was more operational taxonomic unit (OTU) on the walnut shell biochar electrode plate. The final analysis of the two electrode materials using BET specific surface area testing method (BET) and scanning electron microscope (SEM) showed that the pore size of walnut shell biochar was smaller, the specific surface area was larger, and the pore distribution was smoother. The results show that using walnut shells to make electrode plates is an optional waste recycling method and an electrode plate with excellent development prospects.

Introducing Ce into the interface of NiCo LDH@PBAs to build multi core–shell electrode with superior stability of supercapacitor

Core-shell electrodes have been used in many fields, however, the poor conductivity caused by the weak interfacial interaction limits the practical application of the composites. Herein, a novel multi core–shell material (NiCo-Ce@PBAs) used as electrode in supercapacitor is prepared using Ce as bridge to connect the core (NiCo LDH) and shell (NiCo PBAs). Benefiting from the gradient orbital coupling of 2p-4f-π derived from O-Ce-C≡N unit sites in NiCo-Ce@PBAs, the composite shows enhanced covalency and determines to delocalize the electronic expansion in the interaction. Besides, the redox pair of Ce3+-Ce4+ also makes great contribution to expedite the charge transfer as well as enhancing the binding energies of metals in core and shell. Overall, the optimized core–shell electrodes show excellent electrochemical performance with high area-specific capacitance of 1847 F g−1 at 1 A g−1, which is much higher than that of LDH-based electrodes ever reported. In addition, the electrode is found better cyclic performance than the others (95.7 % even after 10,000 cycles), which is due to the fact that the special 4f empty orbits can store partial electrons, thus decreasing the polarization phenomenon. It also shows great practical application when using commercial activated carbon as cathode. This work illustrates a new strategy to construct core–shell electrodes with strong interfacial interaction as well as revealing the important role of orbital theory in the design of multi core–shell electrodes.

Influence of concentration-dependent material properties on the fracture and debonding of electrode particles with core–shell structure

Core–shell electrode particle designs offer a route to improved lithium-ion battery performance. However, they are susceptible to mechanical damage such as fracture and debonding, which can significantly reduce their lifetime. Using a coupled finite element model, we explore the impacts of diffusion-induced stresses on the failure mechanisms of an exemplar system with an NMC811 core and an NMC111 shell. In particular, we systematically compare the implications of assuming constant material properties against using Li concentration-dependent diffusion coefficient and partial molar volume. With constant material properties, our results show that smaller cores with thinner shells avoid debonding and fracture regimes. When factoring in a concentration-dependent partial molar volume, the maximum values of tensile hoop stress in the shell are found to be significantly lower than those predicted with constant properties, reducing the likelihood of fracture. Furthermore, with a concentration-dependent diffusion coefficient, significant barriers to full electrode utilisation are observed due to reduced lithium mobility at high states of lithiation. This provides a possible explanation for the reduced accessible capacity observed in experiments. Shell thickness is found to be the dominant factor in precluding structural integrity once the concentration dependency is accounted for. These findings shed new light on the performance and effective design of core–shell electrode particles.

Nanoengineered, Pd-doped Co@C nanoparticles as an effective electrocatalyst for OER in alkaline seawater electrolysis

Water electrolysis is considered one of the major sources of green hydrogen as the fuel of the future. However, due to limited freshwater resources, more interest has been geared toward seawater electrolysis for hydrogen production. The development of effective and selective electrocatalysts from earth-abundant elements for oxygen evolution reaction (OER) as the bottleneck for seawater electrolysis is highly desirable. This work introduces novel Pd-doped Co nanoparticles encapsulated in graphite carbon shell electrode (Pd-doped CoNPs@C shell) as a highly active OER electrocatalyst towards alkaline seawater oxidation, which outperforms the state-of-the-art catalyst, RuO2. Significantly, Pd-doped CoNPs@C shell electrode exhibiting low OER overpotential of ≈213, ≈372, and ≈ 429 mV at 10, 50, and 100 mA/cm2, respectively together with a small Tafel slope of ≈ 120 mV/dec than pure Co@C and Pd@C electrode in alkaline seawater media. The high catalytic activity at the aforementioned current density reveals decent selectivity, thus obviating the evolution of chloride reaction (CER), i.e., ∼490 mV, as competitive to the OER. Results indicated that Pd-doped Co nanoparticles encapsulated in graphite carbon shell (Pd-doped CoNPs@C electrode) could be a very promising candidate for seawater electrolysis.

Bifunctional CuO@CoV layered double hydroxide (LDH) core–shell heterostructure for electrochemical energy storage and electrocatalysis

The state-of-the-art designing and development of materials is an inevitable prior step for an effective solution regarding energy resources. In the context of supercapacitors (SCs) and electrocatalysis, it remains a challenge to fabricate electrode materials with high specific capacitance, high conductivity and lower overpotential. Here, a core–shell structure is prepared via a facile two-step electrodeposition method using CuO core and electrodeposited binary CoV LDH as the shell and used as a SC electrode and an electrocatalyst. For comparison, the CuO and Cu@CoV LDH electrodes are also prepared using a similar method. The CuO@CoV LDH core–shell electrode exhibits an areal capacitance of 206 mF cm−2 accompanied by an excellent stability of 88 % over 5000 cycles at a current density of 10 mA cm−2. This areal capacitance is far better than that obtained for CuO (49 mF cm−2) and Cu@CoV LDH (58 mF cm−2) electrodes. The symmetric device is fabricated using core–shell heterostructure demonstrating an energy density of 62.8 mWh cm−2 and power density of 985 mW cm−2. Moreover, the CuO@CoV LDH core–shell structure demonstrates an excellent oxygen evolution reaction (OER) catalytic activity with an overpotential of 329 mV and a Tafel slope of 65 mV dec-1. This study opens a new route for the fabrication of CuO@CoV LDH core–shell structure via facile electrodeposition method for the electrochemical energy storage and catalytic activity.

Corrosion-engineered NiMnFe(OH)x@NiMn/TP core–shell electrode for anion exchange membrane water electrolyzers

Exploring cost-effective and highly efficient electrodes is crucial for realizing future renewable energy systems for anion exchange membrane water electrolyzers (AEMWE). There are two half-reactions that occur during water electrolysis, and the development of an effective electrode for the sluggish oxygen evolution reaction (OER) is considered as a key aspect of the half-reaction. In this study, a ternary metal hydroxides electrode was fabricated using a two-step (electrodeposition and corrosion engineering) process. The hydrogen bubble templating electrodeposition enabled the control of the morphology from a dense film to a porous coral-like electrode. Furthermore, Fe was introduced to the electrode to form a core–shell structure via corrosion engineering. The OER catalytic activities of the electrodes were compared in a half-cell, and the results indicated that the optimized electrode required values of 322 mV at 50 mA cm−2. Additionally, stability test was conducted at 100 mA cm−2 for 12 h, and the results indicated that the variation ratio was observed at 1.90 mV h−1. The optimized NiMnFe(OH)x@NiMn/TP was utilized into a membrane electrode assembly (MEA) as an anode, and the catalytic activity of the anode was tested in a single-cell of AEMWE, and it exhibited a current density of 1.5 A cm−2 at 2.02 Vcell and maintained its performance for more than 50 h.

Weavable yarn-shaped moisture-induced electric generator

Moisture-induced electric generation has emerged as a promising powering solution for next-generation wearable electronics since moisture is ubiquitous in the atmosphere. However, the practical applications of current film-shaped generators are limited by the challenge of wearable comfort and large-scale integration into wearables. Herein, we reported a strategy to prepare flexible and high-performance core-shell yarn-shaped moisture-induced electric generator (YMEG) via employing metal wire as the core electrode, polymer-salt solution-treated electrospun nanofiber mats as the active layer, and deposited sliver as the shell electrode. Through the moisture induced interaction between active layer and electrode, the obtained best performance of YMEG with length of 2 cm can produce a highly stable voltage of ∼0.8 V and a current density of 14.3 μA/cm2, reaching the state-of-the-art level among the reported one-dimensional fiber/yarn-shaped MEGs. Furthermore, benefiting from the weavability of YMEG, a dislocation ordered stacking strategy is created for effective integration of YMEG units into fabric, and realizing the simultaneous enhancement of output voltage and current. Such integrated fabric device can work normally under deformation and show successful practical use in power electronics and sensing system, demonstrating great potential to serve as an advanced energy accessory for wearable electronics.

Oxygen-vacancy-decorated ZnO/NiO@N-doped carbon core-shell microspheres with high electrochemical performance for supercapacitor applications

In this study, ZnO/NiO@NC was prepared using polyvinylpyrrolidone (PVP) as a structural guide and carbon source, and an oxygen-vacancy-rich ZnO/NiO@N-doped carbon shell (ZnO/NiO@NC) electrode material was obtained by annealing under an N2 atmosphere. When the current density of the galvanostatic charge–discharge (GCD) was set to 0.5 A/g, the ZnO/NiO@NC electrode exhibited maximum specific capacitance (860.00 F/g), longer charge/discharge time, and a lower impedance compared with other materials. Its specific capacity was maintained above 80%, indicating that the active material had superior stability owing to encapsulation by the carbon shell. The excellent electrochemical performance is attributed to the formation of an effective p-n heterostructure between ZnO and NiO as the basic skeleton, surface oxygen vacancies, and the rich mesoporous structure after high-temperature reduction calcination. Furthermore, the excellent electrical conductivity of the N-doped carbon shell further improves the electrochemical performance of the material.

Hierarchical 2D MnO2@1D mesoporous NiTiO3 core-shell hybrid structures for high-performance supercapattery electrodes: Theoretical and experimental investigations

Novel hybrid core–shell electrodes of 2D and 1D nanomaterials have the ability to effectively address the relatively lower specific energy of supercapacitors. Herein, we report the utilization of the core–shell structure of hierarchical 2D Manganese Dioxide (MnO2) nanoflakes and 1D Nickel Titanate (NiTiO3) (NTO) mesoporous rods as an efficient supercapacitor electrode providing an enormous surface area and more pathways for OH– ions diffusion. The two-step-chemically processed hybrid porous core–shell hetero-architecture of MnO2@NTO delivers a specific capacitance of 1054.7 F/g, specific power of 11879.87 W/kg, and specific energy of 36.23 Wh/kg. Furthermore, 85.3 % retention in capacitance is perceived after 5000 cycles without degradation in the surface morphological features. Complementary first principles density functional theory (DFT) calculations reveal synergistic interaction of MnO2 with NTO in the MnO2@NTO heterostructure, which improves the electrical conductivity.

Classification and Application Research of Lithium Electronic Batteries

In recent years, the damaging effects of burning fossil fuels on the environment and petrol has started to decline, the demand for sustainable energy has risen sharply, and lithium electronic batteries have become a hot spot today due to their high specific capacity, high self-discharge rate, long life and high safety performance. Since lithium metal is an active metal, its preparation and preservation have high requirements on the environment. This paper discusses the development history, working principle, classification and practical application of lithium electronic batteries in real life. The two types of lithium batteries are called lithium metal batteries and lithium ion batteries, respectively. The battery of lithium electronic battery is composed of positive electrode, diaphragm, organic electrolyte, battery shell and negative electrode. Rechargeable battery is also called “lithium ion". Its working principle is to cycle lithium ion back and forth between positive and negative electrodes, and to add and reuse lithium ion alternately and continuously between positive and negative electrodes during charge and discharge. There are basically three categories of lithium-ion battery electrolyte: liquid, solid and molten salt. At present, lithium iron phosphate or frequently used nickel-manganese-cobalt ternary materials are employed as the cathode of standard goods., and negative electrode is mainly graphite and other carbon materials. A better study could result from a deeper understanding of lithium-ion batteries, providing a wealth of theoretical knowledge for in-depth research.

Development of three-dimensional flexible binder-free core-dual shell electrodes via atomic layer deposition of synergistic metal oxide nanocomposites for lithium-ion batteries

The development of three-dimensional (3D) electrode in lithium-ion battery aims to satisfy emerging applications in pursuit of high energy density and power density. Herein, a tunable core-dual shell 3D electrode is demonstrated by atomic layer deposition (ALD) of nanocomposite metal oxides on the surface of TiO2 nanorod (NR), hydrothermally grown on the carbon cloth (CC) without binders. The growth of one-dimensional TiO2 NR on CC mainly constructs the stable 3D framework in the electrode, which ensures a higher surface area to facilitate the electrolyte access and electrochemical reaction. The influence of nanocomposite metal oxides composed of ZnO and TiO2 as the dual shell of TiO2 NR on 3D electrode performance is systemically explored by a series of different ALD cycles. As a proof of concept, the enhancement of 51% and 40%, respectively, in the reversible capacity after 100 charge-discharge cycles and high rate performance at 3 A g−1 can be achieved in the 3D electrode with ALD growth of dual shell in comparison with the uncoated baseline. Such improvements mainly result from the synergistic effect of nanocomposite metal oxides with optimally individual thickness, enabling to further optimize the electrochemical performance and structural stability of 3D electrodes upon cycling.

Enhanced Electrochemical Performance in Ge/GeO2 Nanotubes Anode Derived from C/Ge Nanofibers

Hollow discontinuous Ge/GeO2 nanotubes are successfully prepared after the facile oxidization process in air, which are derived from the C/Ge core–shell nanofibers. Electrospinning and chemical vapor deposition techniques are used to fabricate the carbon nanofiber templates and the Ge shell electrode, respectively. Compared with the C/Ge nanocomposites, the Ge/GeO2 nanotube anode demonstrates improved electrochemical performance due to the enlarged surface area and enough space, which can effectively retard the Ge electrode large volume change during repeated cycling. Full‐battery Ge/GeO2||LiCoO2 is also configured and displays good Li‐ion storage ability.

Preparation of TiO2-graphitized carbon composite photocatalyst and their degradation properties for tetracycline antibiotics

To enhance the adsorption capacity to tetracycline antibiotics and the activity of TiO2 for photocatalysis and optical applications, modified graphitized carbon (GC) was fabricated by peanut shell and waste electrode graphite materials. Then graphitized carbon-doped TiO2 (TiO2-GC) was synthesized using the impregnation method. Characterization of structure and morphological were confirmed that the crystal structure of the TiO2 film on the GC was pure anatase phase. FTIR and XPS peaks clearly indicated the formation of the Ti-C-O valence bond, and the UV–vis DRS showed that the bandgap of TiO2 decreased to 2.67 eV. Electrochemical properties indicated the excellent photoelectric properties and the recombination rate of photogenerated electron-hole pairs became lower in the composite photocatalyst. The results of the photocatalytic degradation of tetracycline hydrochloride experiment showed that the composite photocatalyst had high adsorption and degradation ability for tetracycline (catalysts amount 0.7 g/L, 94.64% with visible lamp irradiation for 2 h) and the photodegradation process accorded with the first-order kinetic equation. TiO2-GC remained stable in five consecutive cycles, which proved its reusability. Furthermore, its excellent cost-effectiveness and strong photon absorption property, which makes it a promising candidate for tetracycline antibiotics effluent treatment in practical applications.

Improved the coconut shell biochar properties for bio-electricity generation of microbial fuel cells from synthetic wastewater

A microbial fuel cell (MFC) is a green device that utilizes chemical energy in organic materials to generate electricity. The low-cost electrode used in this study was made from agricultural waste, coconut shells. The electrochemical properties were improved by combining oxidizing agents and microwave heating processes. The modified coconut shell electrode outperformed virgin biochar by 30.89-fold (230.13±10.11 m<sup>2</sup>/g). The maximum open-circuit voltage, current density, and power density are respectively 995.00±5.00 mV, 841.67±14.43 mA/m<sup>2</sup>, and 283.42±9.67 mW/m<sup>2</sup>. This study demonstrated that modified coconut shell biochar could be used as a low-cost alternative electrode for electricity generation.

Funnel-shaped hierarchical NiMoO4@Co3S4 core-shell nanostructure for enhanced supercapacitor performance

Morphological matching plays a significant role in improving electrochemical properties of core-shell nanostructured as supercapacitor electrode. In this work, a hierarchical, vertically aligned funnel-shaped NiMoO4@Co3S4 core-shell nanostructure was designed by morphological matching for enhanced supercapacitor performance. The core electrode made of densely interconnected NiMoO4 nanosheets were prepared on nickel foam by hydrothermal synthesis, and the shell electrode made of loosely interconnected Co3S4 nanosheets with good conductivity were grown by electrochemical deposition to form a nanosheet-on-nanosheet core-shell nanostructure for improving the electrolyte penetration and storage, facilitating the charge transfer and diffusion. Consequently, the ultrathin nanosheets NiMoO4@Co3S4 core-shell electrode exhibits a remarkable specific capacitance as high as 359.31 mAh g−1 at current density 0.5 A g−1 (2589.6 F g−1 at current density 0.5 A g−1), and capacitance retention of 82.9% after 10,000 charge-discharge cycles. As positive electrode of NiMoO4@Co3S4 and negative electrode of activated carbon, a hybrid supercapacitor with an energy density of 33.37 W h kg−1 and a power density of 387.50 W kg−1 at current density 0.5 A g−1 was assembled. The excellent performance demonstrates that morphological matching is significant to construct core-shell nanostructure of supercapacitor electrode.

Size-and-thickness-dependent fracture patterns of hollow core–shell electrodes during lithiation

Conventional materials for lithium-based rechargeable batteries are reaching their limit. Material failure is also a huge barrier to fully exploit the potential. Novel design of nanomaterials provides possible solutions for these problems. However, the mechanism of material failure during lithiation/delithiation cycling is still not well understood. Here we develop a concurrently coupled chemo-mechanical model based on peridynamics to study the fracture-pattern formation of hollow core–shell structures during lithiation. We show that the geometric parameters of the nanostructures may profoundly influence the behaviors of dynamic fracture, i.e., different coating thicknesses and sizes of the nanotubes lead the cracks to branch in different directions, making them grow into different patterns. We investigate the stress state to explore the reason for the differentiation. A phase diagram for fracture patterns is constructed to have a systematic view. The results in this work provide a basis of designing the nanostructures of the electrode materials in the future.

Nickel cobalt sulfide coated iron nickel selenide hierarchical nanosheet arrays toward high-performance supercapacitors

Tailoring the electronic structure of nanomaterials by constructing core–shell heterostruture is a compelling strategy to design novel electrode materials with modified physiochemical properties for supercapacitors with improved performance. Herein, for the first time, we in situ fabricate iron nickel selenide (FeNiSe2)@nickel cobalt sulfide (Ni4.5Co4.5S8) core–shell nanosheet arrays on carbon cloth by an electrodeposition approach and a selenization treatment. This three-dimensional hierarchcial porous framework formed by plentiful interconnected nanosheets can expose numerous redox active sites with varied oxidation states and provide a conductive and porous skeleton for rapid ion/electrolyte ions transport. Benefiting from its modulated electronic structure and synergetic effect of metal-like FeNiSe2 and Ni4.5Co4.5S8, the as-synthesized FeNiSe2@Ni4.5Co4.5S8 electrode displays a large specific capacity of 236.9 mAh g−1 at 1 A g−1, remarkable rate capability with 80.6% capacity retention at 20 A g−1, and stable cyclic performance, which are superior to those of pure FeNiSe2 and Ni4.5Co4.5S8 electrodes. Besides, the assembled FeNiSe2@Ni4.5Co4.5S8//porous carbon hybrid supercapacitor device offers an energy density of 69.0 Wh kg−1 at 799.2 W kg−1, and exceptional cycling stability with 91.2% capacity retention after 10,000 cycles. This work offers a synthetic strategy to explore core–shell electrode materials with tunable architecture and morphology for high-performance energy storage devices.

Self-Assembly of Ni-Doped Co-MOF Spherical Shell Electrode for a High-Performance Supercapacitor

Self-Assembly of Ni-Doped Co-MOF Spherical Shell Electrode for a High-Performance Supercapacitor

Core-shell structured Li-Fe electrode for high energy and stable thermal battery.

The thermal battery, a key source for powering defensive power systems, employs Li alloy-based anodes. However, the alloying increases the reduction potential of Li which lowers the overall working voltage and energy output. To overcome these issues, Li alloy must be replaced with pure Li. Utilizing pure Li requires a structure that can hold liquefied Li because the working temperature for the thermal battery exceeds the melting point of Li. The liquefied Li can leak out of the anode, causing short-circuit. A Li–Fe electrode (LiFE) in which Fe powder holds liquefied Li has been developed. In LiFE, higher Li content can lead to higher energy output but increases the risk of Li leakage. Thus, Li content in the LiFE has been limited. Here, we demonstrate a novel core–shell electrode structure to achieve a higher energy output. The proposed core–shell LiFE incorporates a high Li content core and a low Li content shell; high energy comes from the core and the shell prevents the Li from leakage. The fabricated core–shell structured electrode demonstrates the high energy of 9074 W s, an increase by 1.66 times compared to the low Li content LiFE with the conventionally used Li content (5509 W s).