In Situ Synthesis of CuCo2S4@N/S-Doped Graphene Composites with Pseudocapacitive Properties for High-Performance Lithium-Ion Batteries

Synthesis and Characterization of MnIn2S4/Single-Walled Carbon Nanotube Composites as an Anode Material for Lithium-Ion Batteries

In this study, we synthesized a transition metal sulfide (TMS) with a spinel structure, i.e., MnIn2S4 (MIS), using a two-step hydrothermal and sintering process. In the context of lithium-ion battery (LIB) applications, ternary TMSs are being considered as interesting options for anode materials. This consideration arises from their notable attributes, including high theoretical capacity, excellent cycle stability, and cost-effectiveness. However, dramatic volume changes result in the electrochemical performance being severely limited, so we introduced single-walled carbon nanotubes (SWCNTs) and prepared an MIS/SWCNT composite to enhance the structural stability and electronic conductivity. The synthesized MIS/SWCNT composite exhibits better cycle performance than bare MIS. Undergoing 100 cycles, MIS only yields a reversible capacity of 117 mAh/g at 0.1 A/g. However, the MIS/SWCNT composite exhibits a reversible capacity as high as 536 mAh/g after 100 cycles. Moreover, the MIS/SWCNT composite shows a better rate capability. The current density increases with cycling, and the SWCNT composite exhibits high reversible capacities of 232 and 102 mAh/g at 2 A/g and 5 A/g, respectively. Under the same conditions, pristine MIS can only deliver reversible capacities of 21 and 4 mAh/g. The results indicate that MIS/SWCNT composites are promising anode materials for LIBs.

Bonding iron chalcogenides in a hierarchical structure for high-stability sodium storage

Owing to price-boom and low-reserve of Lithium ion batteries (LIBs), cost-cutting and well-stocked sodium ion batteries (SIBs) attract a lot of attention, aiming to develop an effective energy storage and conversion equipment. As a typical anode for SIBs, Iron sulfide (FeS) is difficult to maintain the high theoretical capacity. Structural instability and inherent low conductivity limit the cyclic and rate performance of FeS. Herein, hierarchical architecture of FeS-FeSe₂ coated with nitrogen-doped carbon (NC) is obtained by single-step solvothermal method and two-stage high-temperature treatments. Specifically, lattice imperfections provided by heterogeneous interfaces increase the Na⁺ storage sites and fasten ion/electron transfer. Synergistic effect induced by the hierarchical architecture effectively enhances the electrochemical activity and reduces the resistance, which contributes to the transfer kinetics of Na⁺. In addition, the phenomenon that heterogeneous interfaces provide more active site and extra migration Na⁺ path is also proved by density functional theory (DFT). As an anode for SIBs, FeS-FeSe₂/NC (FSSe/C) delivers highly reversible capacity (704.5 mAh·g^-1 after 120 cycles at 0.2 A·g^-1), excellent rate performance (326.3 mAh·g^-1 at 12 A·g^-1) and long-lasting durability (492.3 mAh·g^-1 after 1000 cycles at 4 A·g^-1 with 100 % capacity retention). Notably, the full battery, assembled with FSSe/C and Na₃V₂(PO₄)₃/C (NVP/C), delivers reversible capacity of 252.1 mAh·g^-1 after 300 cycles at 1 A·g^-1. This work provides a facile method to construct a hierarchical architecture anode for high-performance SIBs.

Construction of Ti3C2Tx MXene wrapped urchin-like CuCo2S4 microspheres for high-performance asymmetric supercapacitors

Copper cobalt sulfide (CuCo₂S₄) nanomaterials are regarded as promising electrode materials for high-performance supercapacitors due to their abundant redox states and considerable theoretical capacities. However, the intrinsic poor electrical conductivity, sluggish reaction kinetics and insufficient number of electroactive sites of these materials are huge barriers to realize their practical applications. In this study, a facile two-step strategy to engineer a hierarchical 3D porous CuCo₂S₄/MXene composite electrode is presented for enhanced storage properties. This well-constructed CuCo₂S₄/MXene composite not only provides abundant active sites for the faradaic reaction, but also offers more efficient pathways for rapid electron/ion transport and restricts the volumetric expansion during the charge/discharge process. When evaluated in a 3 M KOH electrolyte, the CuCo₂S₄/MXene-3 electrode exhibits a specific capacity of 1351.6 C g^-1 at 1 A g^-1 while retaining excellent cycling stability (95.2% capacity retention at 6 A g^-1 after 10 000 cycles). Additionally, the solid-state asymmetric supercapacitor (ASC) CuCo₂S₄/MXene//AC device displays an energy density of 78.1 W h kg^-1 and a power density of 800.7 W kg^-1. Two ASC devices connected in series can illuminate a blue LED indicator for more than 20 min, demonstrating promising prospects for practical applications. These electrochemical properties indicate that the high-performance CuCo₂S₄/MXene composites are promising electrode materials for advanced asymmetric supercapacitors.

Bimetallic CuSbSe2 : A Potential Anode Material for Sodium and Lithium-Ion Batteries with High-Rate Capability and Long-Term Stability

Bimetallic transition metal chalcogenides (TMCs) materials have emerged as attractive anodes for lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs) because of the high intrinsic electronic conductivity, rich redox sites and unique reaction mechanism. In this work, we report the synthesis and electrochemical properties of a novel bimetallic TMCs material CuSbSe₂ . The as-prepared anode delivers a high reversible capacity of 545.6  mA h g^-1 for SIBs and 592.6  mA h g^-1 for LIBs at a current density of 0.2 A g^-1 , and an excellent rate capability of 425.9  mA h g^-1 at 20 A g^-1 for SIBs and 226.0  mA h g^-1 at 10 A g^-1 for LIBs without any common-used surface modification or carbonaceous compositing. In addition, ex situ X-ray diffraction (XRD) and High-resolution transmission electron microscopy (HRTEM) reveal a combined conversion-alloying reaction mechanism of LIBs and NIBs. Our findings suggest bimetallic CuSbSe₂ could be a potential anode material for both SIBs and LIBs.

Enhanced Electrochemical Performances of Mn3O4/Heteroatom-Doped Reduced Graphene Oxide Aerogels as an Anode for Sodium-Ion Batteries

Owing to their high theoretical capacity, transition-metal oxides have received a considerable amount of attention as potential anode materials in sodium-ion (Na-ion) batteries. Among them, Mn₃O₄ has gained interest due to the low cost of raw materials and the environmental compatibility. However, during the insertion/de-insertion process, Mn₃O₄ suffers from particle aggregation, poor conductivity, and low-rate capability, which, in turn, limits its practical application. To overcome these obstacles, we have successfully prepared Mn₃O₄ nanoparticles distributed on the nitrogen (N)-doped and nitrogen, sulphur (N,S)-doped reduced graphene oxide (rGO) aerogels, respectively. The highly crystalline Mn₃O₄ nanoparticles, with an average size of 15-20 nm, are homogeneously dispersed on both sides of the N-rGO and N,S-rGO aerogels. The results indicate that the N-rGO and N,S-rGO aerogels could provide an efficient ion transport channel for electrolyte ion stability in the Mn₃O₄ electrode. The Mn₃O₄/N- and Mn₃O₄/N,S-doped rGO aerogels exhibit outstanding electrochemical performances, with a reversible specific capacity of 374 and 281 mAh g^-1, respectively, after 100 cycles, with Coulombic efficiency of almost 99%. The interconnected structure of heteroatom-doped rGO with Mn₃O₄ nanoparticles is believed to facilitate fast ion diffusion and electron transfer by lowering the energy barrier, which favours the complete utilisation of the active material and improvement of the structure's stability.

Performance evaluation of Zr(CUR)/NiCo2S4/CuCo2S4 and Zr(CUR)/CuCo2S4/Ag2S composites for photocatalytic degradation of the methyl parathion pesticide using a spiral-shaped photocatalytic reactor

Zr(CUR)/NiCo₂S₄/CuCo₂S₄ and Zr(CUR)/CuCo₂S₄/Ag₂S ternary composites were synthesized as efficient photocatalysts, and well characterized through XRD, FTIR, DRS, FE-SEM, EDS, and EDS mapping techniques. The potential of a spiral-shaped photocatalytic reactor was evaluated for degradation of the methyl parathion (MP) pesticide using synthesized photocatalysts under visible light irradiation. Computational fluid dynamics (CFD) was applied for analysis of the hydrodynamics behaviour and mass transport occurring inside the reactor. The experiments were performed based on a developed CCD-RSM model, while the desirability function (DF) was used for optimization of the process. Findings showed that the highest MP degradation percentage was 98.70% at optimal operating values including 20 mg L^-1, 0.60 g L^-1, 8 and 40 min for MP concentration, catalyst dosage, pH, and reaction time, respectively. This study clearly demonstrated that high degradation efficiency can be achieved using a spiral-shaped photocatalytic reactor rather than a traditional annular reactor at same conditions. The increase in reaction rate is related to the higher average turbulence kinetic energy in the spiral-shaped reactor over the traditional reactor, which results in the increased diffusivity and improves the mass and momentum transfer.

Ternary heterostructures of 1D/2D/2D CuCo2S4/CuS/Ti3C2 MXene: Boosted amperometric sensing for chlorpyrifos

Multicomponent heterogeneous Ti₃C₂ transition metal carbide (MXene)-based materials are receiving extensive research attention due to their interesting synergistic interactions and catalytic properties. However, the morphology-controllable synthesis of heterostructures as structural stabilizers for Ti₃C₂ MXene remains a challenge owing the complicated synthesis procedure. In this work, a kind of ternary heterogeneous nanomaterials CuCo₂S₄/CuS/Ti₃C₂ MXene with a nanorod/nanoplate/nanosheet hybrid architecture is constructed through a one-step low-temperature solvothermal method. The well-designed ternary one-dimensional (1D)/two-dimensional (2D)/2D CuCo₂S₄/CuS/Ti₃C₂ MXene heteromaterials exhibit synergistic improvements in substrate-catalyzed reactions for electrochemical acetylcholinesterase (AChE) biosensor. The Michaelis-Menten constant for the Nafion/AChE/CuCo₂S₄/CuS/Ti₃C₂ MXene/GCE biosensor is 228 μM, which is smaller than ones reported in previous literatures, indicating a higher affinity of the fabricated enzyme biosensor to acetylthiocholine chloride. The biosensor exhibits a well linear relationship with chlorpyrifos concentration ranging from 2.852 × 10^-12 M to 2.852 × 10^-6 M. The multicomponent 1D/2D/2D CuCo₂S₄/CuS/Ti₃C₂ MXene heteromaterial may shine a light in more electrochemical applications.

CuCo2S4@B,N-Doped Reduced Graphene Oxide Hybrid as a Bifunctional Electrocatalyst for Oxygen Reduction and Evolution Reactions

In this report, a facile synthetic route is adopted for typically designing a hybrid electrocatalyst containing boron, nitrogen dual-doped reduced graphene oxide (B,N-rGO) and thiospinel CuCo₂S₄ (CuCo₂S₄@B,N-rGO). The electrocatalytic activity of the hybrid catalyst is tested with respect to oxygen evolution (OER) and oxygen reduction (ORR) reactions in alkali. Physicochemical characterizations confirm the unique formation of a reduced graphene oxide-non-noble-metal sulfide hybrid. Electrochemical evaluation by cyclic voltammetry (CV) and linear-sweep voltammetry (LSV) reveals that the CuCo₂S₄@B,N-rGO hybrid possesses enhanced ORR and OER activity compared to the B,N-rGO-free CuCo₂S₄ catalyst. The synthesized CuCo₂S₄@B,N-rGO hybrid demonstrates remarkable enhancement in catalytic performance with an improved onset potential (1.50 and 0.88 V) and low Tafel slope (112 and 73 mV dec^-1) for both OER and ORR processes, respectively. In addition, the catalyst exhibits a diminutive potential difference (0.81 V) between the potential corresponding to the 10 mA cm^-2 current density for OER and the half-wave potential for ORR. The superior catalytic activity and high durability of the hybrid material may be attributed to the synergistic effect arising from the metal sulfide and dual-doped reduced graphene oxide. The present study illuminates the possibility of using the dual-doped graphene oxide and metal sulfide hybrid as a competent bifunctional cathode catalyst for renewable energy application.

Asymmetric, Flexible Supercapacitor Based on Fe-Co Alloy@Sulfide with High Energy and Power Density

Electrode materials with high conductivities that are compatible with flexible substrates are important for preparing high-capacitance electrode materials and improving the energy density of flexible supercapacitors. Here, we report the design and fabrication of a new type of flexible electrode based on nanosheet architectures of a Co-Fe alloy (FeCo-A) coated with ternary metal sulfide composites (FeCo-Ss) on silver-sputtered carbon cloth. The high conductivity of the flexible substrate and the iron-cobalt alloy skeleton enables good electron transmission through the material. In particular, the outer FeCo-S layer has an average thickness of ∼30 nm, providing many active sites. This layer also inhibits the oxidation of the alloy. The electrode material is close to 20 nm thick, which limits inaccessible volumes and promotes high utilization of FeCo-alloy@FeCo-sulfide (FeCo-A-S). The additive-free FeCo-A-S electrode has a high specific capacitance of 2932.2 F g^-1 at 1.0 A g^-1 and a superior rate capability. All-solid-state supercapacitors based on these electrodes have a high power density of 8000 W kg^-1 and a high energy density of 46.1 W h kg^-1.

Highly uniform platanus fruit-like CuCo2S4 microspheres as an electrode material for high performance lithium-ion batteries and supercapacitors

Platanus fruit-like CuCo₂S₄ microspheres were fabricated by using a facile hydrothermal method followed by a sulfidation process. As a lithium storage material, they deliver an outstanding initial specific capacity of 1119.3 mA h g^-1 at 0.05 A g^-1 and a high reversibility of 954 mA h g^-1 over 200 cycles even at 1 A g^-1. In addition, when applied in supercapacitors they display a superb specific capacitance of 824 F g^-1 at 1 A g^-1, even over 10 000 cycles and they can also maintain 75% retention at 5 A g^-1 and exhibit good reversibility. Furthermore, an advanced asymmetric supercapacitor (ASC) exhibits an advantageous energy density of 36.67 W h kg^-1 when the power density increases up to 750 W kg^-1. Additionally, the assembled device can easily light a 1.5 V bulb for several minutes. The excellent performance of CuCo₂S₄ is due to the bimetallic synergistic effect and the unique platanus fruit-like microsphere architecture, which can limit the restacking of the structure and provide suitable voids. This excellent performance confirms that platanus fruit-like CuCo₂S₄ microspheres are a promising electrode material for energy storge. This work will provide a new strategy to prepare high-performance bimetallic sulfide anode materials by a facile method.

Facile Preparation of CuCo2 S4 /Cu7.2 S4 Nanocomposites as High-Performance Cathode Materials for Rechargeable Magnesium Batteries*

Rechargeable magnesium batteries (RMBs) have been considered a promising energy-storage device due to their high energy density and high safety, but they still suffer from a lack of high-rate performance and cycle performance of the cathode. Nanosized CuCo₂ S₄ /Cu_7.2 S₄ composites have been synthesized for the first time by a facile solvothermal method. Herein, the magnesium ion storage behavior when applied in the cathode for RMBs is discussed. Electrochemical results demonstrated that the CuCo₂ S₄ /Cu_7.2 S₄ composites exhibit a high initial discharge capacity of 256 mAh g^-1 at 10 mA g^-1 and 123 mAh g^-1 at 300 mA g^-1 at room temperature and an outstanding long-term cyclic stability over 300 cycles at 300 mA g^-1 . Furthermore, the electrochemical storage mechanism demonstrated that the storage process of magnesium ion in the CuCo₂ S₄ /Cu_7.2 S₄ cathode is mainly driven by strong pseudocapacitive effects.

The synthesis of alternating donor-acceptor polymers based on pyrene-4,5,9,10-tetraone and thiophene derivatives, their composites with carbon, and their lithium storage performances as anode materials

Two conjugated polymer@activated carbon composites were synthesized by the in situ polymerization of two donor-acceptor type polymers including poly[(thiophene-2,5-yl)-((pyrene-4,5,9,10-tetraone)-2,7-yl)] (PTPT) and poly[((2,3-dihydrothieno[3,4-b][1,4]dioxine)-5,7-yl)-((pyrene-4,5,9,10-tetraone)-2,7-yl)] (POTPT) on activated carbon (AC) by one-step cross-coupling reaction catalyzed by an organometallic catalyst. Cyclic voltammetry showed that both polymers exhibited ambipolar properties, low bandgaps, and low electrode potentials, which could be useful for their application as anodes in lithium-ion battery cells (LIBs). For PTPT@AC and POTPT@AC anodes, they showed a high capacity of 253.9 and 370.5 mA h g-1 at 100 mA g-1. Besides, the capacities of pure polymers were calculated to be 693.5 and 1276.5 mA h g-1 for PTPT and POTPT, respectively, at 100 mA g-1. Compared with PTPT, the introduction of the 3,4-ethylenedioxy unit into the side chain of the thiophene unit leads to substantially improved performance of POTPT due to the lowered LUMO energy levels of POTPT and the electron-rich feature of the EDOT unit. It is suggested that the structure-tuning strategy might be an effective method to prepare the new polymer-based anode for next generation LIBs with high performance and high safety.

Spinel-type FeNi2S4 with rich sulfur vacancies grown on reduced graphene oxide toward enhanced supercapacitive performance

Due to the coexistence of rich sulfur vacancies and rGO, the r-FeNi₂S₄-rGO electrode shows a superior specific capacitance.

Nanostructured flower-shaped CuCo2S4 as a Pt-free counter-electrode for dye-sensitized solar cells

We demonstrated a solvothermally prepared cost-effective, mesoporous, and high surface area nanostructured flower-shaped CuCo2S4 counter-electrode for dye-sensitized solar cells. The new counter electrode exhibited comparable results with a traditional Pt-based counter electrode, 7.56% vs. 7.42%, respectively. The electrochemical analysis demonstrated superior electrocatalytic activity of the product, which was stable even after 6 months of aging.

Fabrication of Few-Layer Graphene-Supported Copper Catalysts Using a Lithium-Promoted Thermal Exfoliation Method for Methanol Oxidative Carbonylation

Exfoliation of graphene oxide (GO) via thermal expansion is regarded as the most promising approach to obtain few-layer graphene (FLG) in bulk. Herein, we introduce an efficient strategy for improving the exfoliation process by adding a tiny amount of lithium nitrate in the precursors, which significantly enhances the removal of oxygen-containing functional groups and produces 1-2 layer graphene. FLG-supported highly dispersed Cu nanoparticles (NPs, ≈4.2 nm) can be further synthesized through exfoliating the mixture of GO, lithium nitrate, and copper(II) nitrate, which displayed superior catalytic activity and stability in the synthesis of dimethyl carbonate (DMC) using liquid methanol oxidative carbonylation. The characterization results demonstrate that during the thermal expansion process, lithium nitrate was decomposed to Li₂O and immediately reacted with CO₂ released by the decomposition of GO to form stable Li₂CO₃, which promotes efficient charge transfer and produces Cu^δ+ (0 < δ < 1) species in the Cu/Li-PGO catalyst. Density functional theory calculations prove that the presence of Cu^δ+ markedly facilitates CO adsorption over the resulting catalyst and causes a decrease of the energy barrier of the rate-limiting step for DMC formation (CO insertion). These findings give a theoretical explanation of the enhanced catalytic performance of the Cu/Li-PGO catalyst. The present work provides a simple and practical avenue to the exfoliation of graphene and the dispersions of metal NPs on graphene sheets.

CuCo2 S4 -rGO Microflowers: First-Principle Calculation and Application in Energy Storage

This paper demonstrates the ability of a CuCo₂ S₄ -reduced graphene oxide (rGO) composite to perform robust electrochemical performances applying to supercapacitors (SCs) and lithium ion batteries (LIBs). The first-principle calculation based on density functional theory is conducted to study the electronic property of CuCo₂ O₄ and CuCo₂ S₄ and provide a theoretical basis for this work. Then, the 3D spinel-structured CuCo₂ O₄ and CuCo₂ S₄ microflowers are synthesized and compared as electrodes for both SCs and LIBs. The CuCo₂ S₄ microflowers can provide a larger specific surface area, which enlarges the contact area between the electrode material and the electrolyte and contributes to high-efficiency electrochemical reactions. The reduced graphene oxides are coated on the CuCo₂ S₄ microflowers, therefore effectively increasing the conductivity, and further absorbing the stress produced in the reaction process. As an electrode of a symmetric supercapacitor, the optimized CuCo₂ S₄ -rGO composite exhibits an energy density of 16.07 Wh kg^-1 and a maximum power density of 3600 W kg^-1 . Moreover, the CuCo₂ S₄ -rGO composite can also be used as an anode for lithium ion batteries, exhibiting a reversible capacity of 1050 mAh g^-1 after 140 cycles at the current density of 200 mA g^-1 . The galvanostatic intermittence titration techniques also reveal superior Li-ion diffusion behavior of the CuCo₂ S₄ -rGO composite during redox reactions.

In-situ synthesis of Fe7S8 nanocrystals decorated on N, S-codoped carbon nanotubes as anode material for high-performance lithium-ion batteries

Fe₇S₈ has emerged as an attractive anode material for lithium-ion batteries (LIBs) due to its outstanding features such as low cost, high theoretical capacity, as well as environmental benignity. However, the rapid capacity fading derived from the tremendous volume change during the charging/discharging process hinders its practical application. Nanostructure engineering and the combination with carbonaceous material are essential to address this issue. In this work, Fe₇S₈ nanocrystals decorated on N, S-codoped carbon nanotubes (Fe₇S₈-NSC) were synthesized through a facile one-step pyrolysis of Fe-containing polypyrrole (PPy) nanotubes with sulphur powders under nitrogen atmosphere. When evaluated as anode of LIBs, Fe₇S₈-NSC demonstrates excellent cycling stability (718.8 mAh g^-1 at 100 mA g^-1 after 100 cycles) and superior rate ability (290.8 mAh g^-1 at 2000 mA g^-1). Moreover, Fe₇S₈-NSC shows a typical specific capacity recovery phenomenon, an extraordinary capacity of 744.4 mAh g^-1 at 2000 mA g^-1 after 1000 cycles can be achieved, which outperforms most of the Fe₇S₈-based anode materials reported before. The Fe₇S₈-NSC should be a promising anode material for high-performance LIBs.

Self-Templating Synthesis of Hollow Co3O4 Nanoparticles Embedded in N,S-Dual-Doped Reduced Graphene Oxide for Lithium Ion Batteries

The design and synthesis of hollow-nanostructured transition metal oxide-based anodes is of great importance for long-term operation of lithium ion batteries. Herein, we report a two-step calcination strategy to fabricate hollow Co₃O₄ nanoparticles embedded in a N,S-co-doped reduced graphene oxide framework. In the first step, core-shell-like Co@Co₃O₄ embedded in N,S-co-doped reduced graphene oxide is synthesized by pyrolysis of a Co-based metal organic framework/graphene oxide precursor in an inert atmosphere at 800 °C. The designed hollow Co₃O₄ nanoparticles with an average particle size of 25 nm and wall thickness of about 4-5 nm are formed by a further calcination process in air at 250 °C via the nanoscale Kirkendall effect. Both micropores and mesopores are generated in the HoCo₃O₄/NS-RGO framework. Benefiting from the hierarchical porous structure of the hollow Co₃O₄ and the co-doping of nitrogen and sulfur atoms in reduced graphene oxide, the thus-assembled battery exhibits a high specific capacity of 1590 mAh g^-1 after 600 charge-discharge cycles at 1 A g^-1 and a promising rate performance from 0.2 to 10 A g^-1.

Freestanding Needle Flower Structure CuCo2S4 on Carbon Cloth for Flexible High Energy Supercapacitors With the Gel Electrolyte

A facile hydrothermal approach was adopted to the direct synthesis of bimetallic sulfide (CuCo₂S₄) on carbon cloth (CC) without binders for the supercapacitor's electrodes. A possible formation mechanism was proposed. The prepared bimetallic electrode exhibited a high specific capacitance (Csp) of 1,312 F·g⁻¹ at 1 A·g⁻¹, and an excellent capacitance retention of 94% at 5 A·g⁻¹ over 5,000 cycles. In addition, the asymmetric supercapacitor (CuCo₂S₄/CC//AC/CC) exhibited energy density (42.9 wh·kg⁻¹ at 0.8 kW·kg⁻¹) and outstanding cycle performance (80% initial capacity retention after 5,000 cycles at 10 A·g⁻¹). It should be noted that the electrochemical performance of a supercapacitor device is quite stable at different bending angles. Two charged devices in series can light 28 red-colored LEDs (2.0 V) for 5 min. All of this serves to indicate the potentially high application value of CuCo₂S₄.

Sea urchin-like CuCo2S4 microspheres with a controllable interior structure as advanced electrode materials for high-performance supercapacitors

The rational construction of a supercapacitor electrode structure can realize high specific surface area, good cycling stability and high capacitance.

NiMoS4 nanocrystals anchored on N-doped carbon nanosheets as anode for high performance lithium ion batteries

Owing to the excellent electrical conductivity and high theoretical capacity, binary transition metal sulfides have attracted extensive attention as promising anodes for lithium ion batteries (LIBs). However, the relatively poor electrical conductivity and serious capacity fading originated from large volume change still hinder their practical applications. Herein, binary NiMoS₄ nanoparticles are deposited on N doped carbon nanosheets (NC@NiMoS₄) through a facile hydrothermal method. The N doped carbon nanosheets and the strong chemical bonding between NC and NiMoS₄ can accommodate the volume change, keep the structural integrity and promote the ion/electron transfer during electrochemical reaction. The extra voids between NiMoS₄ nanoparticles enlarge the contact area and reduce the lithium migration barriers. As anode for LIBs, the NC@NiMoS₄ exhibits the excellent cycle stability with 834 mAh g^-1 after 100 cycles at the current density of 100 mA g^-1. Even at high rate of 2000 mA g^-1, the specific capacity of 544 mAh g^-1 can be achieved after 500 cycles.

Interfacial Electronic Structure Modulation of Hierarchical Co(OH)F/CuCo2S4 Nanocatalyst for Enhanced Electrocatalysis and Zn-Air Batteries Performances

The exploration of robust multifunctional electrocatalyst for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is a continuing challenge for the sustainable energy sources. However, as the key reactions in renewable metal-air batteries and fuel cells, the energy conversion efficiencies of ORR and OER are greatly affected by their reaction kinetics. In addition to designing excellent electrocatalysts, new methods to stabilize the electrolyte/electrode interfaces are urgently needed. Herein, a hierarchical Co(OH)F/CuCo₂S₄ hybrid was created as an efficient catalyst for OER and ORR in alkaline media. Combining spinel ferrite with the hydroxide can greatly boost their catalytic performance. The optimal Co(OH)F/CuCo₂S₄ hybrid exhibits superior OER performance and durable stability, as demonstrated by an ultralow overpotential of 230 mV at 10 mA·cm^-2. The onset potential and the half-wave potential in 0.1 M KOH solution for ORR are 0.88 and 0.80 V, respectively. Furthermore, the Co(OH)F/CuCo₂S₄ hybrid served as a catalyst in Zn air batteries catalyst exhibits a low overpotential of 1.12 V at 50.0 mA·cm^-2, large power density of 144 mW·cm^-2, and a long electrochemical lifetime of 118 h (118 cycles), which is even better than those of the Pt/C and RuO₂ catalysts. The rational integration of spinel and hydroxide at the interface can provide multifunctional electrocatalysis and possess a high reactivity for oxygen conversion. Synergistic coupling effect and interfacial electronic interaction between Co(OH)F and CuCo₂S₄ can significantly enhance the electron transfer rate, and these synergistic advantages enable the heterogeneous structure of the multifunctional electrocatalyst to produce excellent catalytic performance.

Encapsulating MnSe Nanoparticles Inside 3D Hierarchical Carbon Frameworks with Lithium Storage Boosted by in Situ Electrochemical Phase Transformation

Electrode materials that act through the electrochemical conversion mechanism, such as metal selenides, have been considered as promising anode candidates for lithium-ion batteries (LIBs), although their fast capacity attenuation and inadequate electrical conductivity are impeding their practical application. In this work, these issues are addressed through the efficient fabrication of MnSe nanoparticles inside porous carbon hierarchical architectures for evaluation as anode materials for LIBs. Density functional theory simulations indicate that there is a completely irreversible phase transformation during the initial cycle, and the high structural reversibility of β-MnSe provides a low energy barrier for the diffusion of lithium ions. Electron localization function calculations demonstrate that the phase transformation leads to high charge transfer kinetics and a favorable lithium ion diffusion coefficient. Benefitting from the phase transformation and unique structural engineering, the MnSe/C chestnut-like structures with boosted conductivity deliver enhanced lithium storage performance (885 mA h g^-1 at a current density of 0.2 A g^-1 after 200 cycles), superior cycling stability (a capacity of 880 mA h g^-1 at 1 A g^-1 after 1000 cycles), and outstanding rate performance (416 mA h g^-1 at 2 A g^-1).

Carbon Quantum Dot-Anchored Bismuth Oxide Composites as Potential Electrode for Lithium-Ion Battery and Supercapacitor Applications

The present investigation elucidates a simple hydrothermal method for preparing nanostructured bismuth oxide (Bi₂O₃) and carbon quantum dot (CQD) composite using spoiled (denatured) milk-derived CQDs. The formation of the CQD-Bi₂O₃ composite was confirmed by UV-vis absorption, steady-state emission, and time-resolved fluorescence spectroscopy studies. The crystal structure and chemical composition of the composite were examined by X-ray diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy, and thermogravimetric analysis. The surface morphology and the particle size distribution of the CQD-Bi₂O₃ were examined using field emission scanning electron microscope and high-resolution transmission electron microscope observations. As an anode material in lithium-ion battery, the CQD-Bi₂O₃ composite exhibited good electrochemical activity and delivered a discharge capacity as high as 1500 mA h g^-1 at 0.2C rate. The supercapacitor properties of the CQD-Bi₂O₃ composite electrode revealed good reversibility and a high specific capacity of 343 C g^-1 at 0.5 A g^-1 in 3 M KOH. The asymmetric device constructed using the CQD-Bi₂O₃ and reduced graphene oxide delivered a maximum energy density of 88 Wh kg^-1 at a power density of 2799 W kg^-1, while the power density reached a highest value of 8400 W kg^-1 at the energy density of 32 Wh kg^-1. The practical viability of the fabricated device is demonstrated by glowing light-emitting diodes. It is inferred that the presence of conductive carbon network has significantly increased the conductivity of the oxide matrix, thereby reducing the interfacial resistance that resulted in excellent electrochemical performances.

Organometallic Precursor-Derived SnO2/Sn-Reduced Graphene Oxide Sandwiched Nanocomposite Anode with Superior Lithium Storage Capacity

Benefiting from the reversible conversion reaction upon delithiation, nanosized SnO₂, with its theoretical capacity of 1494 mA h g^-1, has gained special attention as a promising anode material. Here, we report a self-assembled SnO₂/Sn-reduced graphene oxide (rGO) sandwich nanocomposite developed by organometallic precursor coating and in situ transformation. Ultrafine SnO₂ nanoparticles with an average diameter of 5 nm are sandwiched within the rGO/carbonaceous network, which not only greatly alleviates the volume changes upon lithiation and aggregation of SnO₂ nanoparticles but also facilitates the charge transfer and reaction kinetics of SnO₂ upon lithiation/delithiation. As a result, the SnO₂/Sn-rGO nanocomposite exhibited a superior lithium storage capacity with a reversible capacity of 1307 mA h g^-1 at a current density of 80 mA g^-1 in the potential window of 0.01-2.5 V versus Li⁺/Li and showed a reversible capacity of 767 mA h g^-1 over 200 cycles at a current density of 400 mA g^-1. When cycling at a higher current density of 1600 mA g^-1, the SnO₂/Sn-rGO nanocomposite showed a highly stable capacity of 449 mA g^-1 without obvious decay after 400 cycles.