Conductive Skeleton Research Articles

Cu-MOFs derived three-dimensional Cu1.81S@C for high energy storage performance

Significant volume changes and slow ionic transport during charge/discharge processes restrict the improvement of electrochemical performance for CuxS (x = 1–2). Herein, a new strategy by introducing Cu-BTC (copper(II)-benzene-1,3,5-tricarboxylate) as a processor to derive three-dimensional Cu1.81S@C using green sulfurization and calcination methods is proposed. Benefiting from the high electrical conductivity, multistage pore size structure and stable structure brought by the conductive carbon skeleton after calcination, Cu1.81S@C-650oC exhibits a high specific capacitance of 291.1 F g-1 at a current density of 1 A g-1 and a superior rate capability of 83.6 % at a current density of 10 A g-1. In addition, the assembled asymmetric supercapacitor (Cu1.81S@C-650oC//AC ASC) also shows impressive performances, such as an energy density up to 16 Wh kg-1 at a power density of 352 W kg-1 and an excellent cycling stability of 93.1 % over 5000 cycles at a current density of 2 A g-1. This work demonstrates that the Cu-BTC-derived Cu1.81S@C is an attractive material with potential applications in energy storage devices.

Simultaneous Solar-Thermal Desalination and Catalytic Degradation of Wastewater Containing Both Salt Ions and Organic Contaminants.

Although solar steam generation is promising in generating clean water by desalinating seawater, it is powerless to totally degrade organic contaminants in the seawater. Herein, solar steam generation and catalytic degradation are integrated to generate clean water by simultaneous solar-driven desalination and catalytic degradation of wastewater containing both salt ions and organic contaminants. Stepwise decoration of three-dimensional nickel foam with polypyrrole, reduced graphene oxide (RGO), and cobalt phosphate is realized to obtain polypyrrole/RGO/cobalt phosphate/nickel foam (PGCN) hybrids for solar-driven desalination and catalytic degradation of wastewater containing antibiotics and salt ions. The oxygen-containing groups of the RGO integrated with the porous nickel foam make the porous PGCN hybrid hydrophilic and ensure the upward transport of water to the evaporation surface, and the oxygen vacancies of the cobalt phosphate allow the PGCN to generate abundant highly active singlet oxygen that could still exhibit excellent catalytic degradation performances in the high salinity and highly alkaline environment of seawater. In addition to the high solar light absorbance and satisfactory solar-thermal conversion efficiency of polypyrrole and RGO, the thermally conductive nickel foam skeleton can effectively transfer the heat generated by the solar-thermal energy conversion to the adjacent cobalt phosphate catalyst and nearby wastewater, achieving a solar-thermal-promoted catalytic degradation of organic contaminants. Therefore, a high pure water evaporation rate of 2.08 kg m-2 h-1 under 1 sun irradiation and 100% catalytic degradation of Norfloxacin and dyes are achieved. The PGCN hybrid is highly efficient in purifying seawater containing 10 ppm Norfloxacin and simultaneously achieves a high purification efficiency of 100 kg m-2 h-1.

Multifunctional Ni-doped CoSe2 nanoparticles decorated bilayer carbon structures for polysulfide conversion and dendrite-free lithium toward high-performance Li-S full cell

The commercial application of lithium-sulfur batteries is severely hampered by polysulfide shuttle effects, sluggish redox kinetics, and uncontrollable lithium dendrite growth. Herein, a unique Ni-doped CoSe2 nanoparticle decorated bilayer carbon (Ni-CoSe2/BC) structure is synthesized for both the sulfur cathode and lithium anode, which introduces bi-functionalities including Ⅰ) the internal carbon conductive network skeleton of carbon nanotubes is capable of physically confining, storing, and alleviating volume expansion of sulfur; and Ⅱ) Ni-CoSe2 nanoparticles decorated on the external carbon nanoarrays contribute to efficient chemical anchoring and accelerated polysulfide conversion for the cathode, and serve as lithiophilic sites to induce homogeneous lithium deposition for the anode. As a result, Ni-CoSe2/BC effectively inhibits the shuttle effect and induces dendrite-free lithium deposition. The Ni-CoSe2/BC-S delivers a high discharge specific capacity of 806 mAh g−1 after 400 cycles at 1 C, with a low capacity decay rate of 0.07% per cycle. Moreover, the Ni-CoSe2/BC-Li exhibits an impressively long cycle life of 2000 h at 10 mA cm−2/10 mAh cm−2. Notably, the lithium-sulfur full cell assembled with Ni-CoSe2/BC as universal hosts for both anode and cathode possesses an average discharge capacity of 6.07 mAh cm−2 in 50 cycles (Sulfur loading=12.8 mg cm−2, Electrolyte/Sulfur=7.8 μL mg−1, and Negative/Positive=1.56). This work provides novel structural design and mechanism insights for the practical application of lithium-sulfur batteries.

High thermal conductivity of porous graphite/paraffin composite phase change material with 3D porous graphite foam

Phase change materials (PCMs) are widely used in the field of thermal management and energy storage, but both low thermal conductivity and leakage problem limit their broad applications. In this work, a 3D porous graphite (PG) foam was prepared by a pressing and drying method with solid mixture of graphite powder and ammonium bicarbonate (NH4HCO3), and it was used as the thermal conductive skeleton and shape stabilizer of PCMs. PG/paraffin composite PCMs (CPCMs) were then prepared by the vacuum impregnation of liquid paraffin into PG foam. It showed that the skeleton of 3D PG foam greatly improves the thermal conductivity of CPCMs. The prepared PG/paraffin CPCMs exhibited an ultra-high thermal conductivity of 19.27 Wm-1K−1 at a volume fraction 35.55% of graphite, which is about 76.08 times higher than that of paraffin. The heat conduction mechanism of the PG/paraffin CPCMs are analyzed, and it is found that Maxwell-Eucken model can be used to accurately predict its thermal conductivity. Moreover, the CPCMs show good performance of thermal shape stability and exhibit superior anti-leakage characteristic. The proposed method for the preparation of 3D PG foam is robust, and the excellent performance of their based CPCMs will be promising in the field of heat dissipation and thermal storage.

Field-assisted conductive substrate sparks the redox kinetics of Co9S8 in Li- and Na-ion batteries

As a promising candidate electrode material in both Li- and Na-ion batteries (L/SIBs), the application of Co9S8 is being hindered by its unsatisfactory electrochemical performance caused by the sluggish ion diffusion kinetics and drastic volume expansion. Herein, a hybrid material composed of Co9S8−x, N-doped carbon foam that seeded with Co nanoparticles (Co9S8−x@Co-NC) is constructed. Particularly, theoretical and experimental results imply that a built-in electric field at the interface of Co and NC is observed due to the variation of Fermi levels, forming rich Mott-Schottky-like heterointerfaces, which can significantly enhance the charge transfer capability between the active materials of Co9S8 and conductive NC skeleton. Moreover, the sulfur defects in Co9S8−x can not only effectively lower the energy barrier of the ion diffusion and charge transfer processes, but also endow the target sample with more storage/adsorption/active sites for Li+/Na+ ions, thus improving the rate performance of the Co9S8−x@Co-NC composite. As a result, the Co9S8−x@Co-NC exhibits fast surface-controlled redox kinetics and robust cycling stability. For instance, the Co9S8−x@Co-NC displays impressive Li-storage properties in both half and full cells with a high reversible capacity of 1007.4 mA h g−1 at 0.1 A g−1 after 100 cycles and superior rate capability up to 5 A g−1. Moreover, based on these comprehensive merits, the Co9S8−x@Co-NC composite shows decent electrochemical performance (472.2 and 311.1 mA h g−1 at 0.1 and 10 A g−1, respectively) as an anode for SIBs. This work presents an effective strategy for the construction of Mott-Schottky-like heterointerfaces in Co9S8 based materials and provides specific inspiration for future works designing high-performance electrodes via interfacial engineering.

Enhanced light-to-thermal conversion performance of self-assembly carbon nanotube/graphene-interconnected phase change materials for thermal-electric device

Solar energy conversion and storage technologies have attracted more attention to alleviate the energy crisis and ecological concern. Further improvement on the thermal conductivity and photothermal storage capacity of phase change materials (PCMs) remain a huge challenge. In this work, a new composite PCMs employing carbon-based (CRGO) aerogel as the supporting material and paraffin wax (PW) as the PCM was prepared. We achieve a three-dimensional (3D) porous interconnected structure by cross-linking carbon nanotubes (CNT) with reduced graphene oxide (rGO). This 3D structure could provide more heat transfer channels and effective contact interfaces, resulting in its enhanced thermal conductivity. The aspect ratio of CNT and the ratio of CNT and rGO is regulated to optimize the 3D thermal conductive skeleton for CRGO aerogel. As a result, the multi-layer CRGO aerogel composite PCMs exhibited high solid-liquid phase change enthalpy (146.7 J/g) and excellent phase change stability. Optimal incorporation of 30 % CNT increased the thermal conductivity to 1.27 W/(m·K), which is 452 % higher than that of the pure PW. Meanwhile, a photothermal conversion efficiency of up to 90.3 % was achieved for the composite PCMs. In addition, the output voltage of the solar-thermal-electric device based on composite PCMs (150 mV) is about 3.75 times that of the blank plate (40 mV) under solar radiation. Therefore, CRGO aerogel composite PCMs show great promise for efficient solar-thermal-electric energy conversion utilization.

Asymmetric electrode design with built‐in nitrogen transfer channel achieving maximized three‐phase reaction region for electrochemical ammonia synthesis

AbstractCarbon‐free electrochemical nitrogen reduction reaction (NRR) is an appealing strategy for green ammonia synthesis, but there is still a significant performance bottleneck. Conventional working electrode is usually flooded by the electrolyte during the NRR test, and only the surface material could get access to the nitrogen, which inevitably gives rise to sluggish reaction rate. Herein, an asymmetric electrode design is proposed to tackle this challenge. An aerophilic layer is constructed on one face of the electrocatalyst‐loaded electrode, while the other side maintains its original structure, aiming to achieve facilitated nitrogen transfer and electrolyte permeation within the conductive skeleton simultaneously. This asymmetric architecture affords extensive three‐phase reaction region within the electrode as demonstrated by the combination of theoretical simulations and experimental measurements, which gives full play to the loaded electrocatalyst. As expected, the proof‐of‐concept asymmetric electrode delivers an NH3 yield rate of 40.81 μg h−1 mg−1 and a Faradaic efficiency of 71.71% at −0.3 V versus the reversible hydrogen electrode, which are more than 4 and 7 times that of conventional electrode, respectively. This work presents a versatile strategy for enhancing the interfacial reaction kinetics and is instructive to electrode design for gas‐involved electrochemical reactions.

Temperature-insensitive stretchable conductors based on hierarchical double-layer graphene foams/PEDOT:PSS networks

The development of temperature-insensitive stretchable conductors has significant implications for a wide range of applications, including wearable electronics, flexible sensors, and stretchable circuits in different environments, while resistances of conductive polymer composites are generally temperature dependent. In this study, we develop a novel and facile approach to achieve stable electrical conducting under stretching and temperature variation by incorporating a hierarchical wavy graphene foam (wGF) with a double-layer conductive framework formed by coating highly conductive poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) on interior graphene struts. The resulting wGF/PEDOT:PSS/PDMS composites exhibit exceptional resistance stabilities during stretching within a wide temperature range of -30-145 °C. The synergistic effects of the unique composite structure, including the macroscopic wavy structures, microscopic compacted conductive skeletons, and more ductile double-layer graphene/PEDOT:PSS frameworks, contribute to the excellent stretchable conducting properties and temperature-insensitive performances. The developed temperature-insensitive stretchable conductor holds great promise for reliable performance in various environmental conditions, opening up new opportunities for advanced flexible and wearable electronic devices.

In-situ synthesis of porous Na3V2(PO4)3 with stable V[sbnd]O[sbnd]C bridge bonding by hard template method

Low electronic conductivity and poor properties at high rate have hindered the application of Na3V2(PO4)3 (NVP). Herein, a facile synthesis of NVP with porous carbon skeleton is proposed. Specifically, Na2CO3 and glucose, acting as hard templates, are introduced to the precursors after initial firing stage, and Na2CO3 particles are removed by flushing after the final heatment. Due to the thermal conductivity of Na2CO3, the secondary addition of glucose can generate distinctive graphitized porous carbon skeleton, which bonds well with the amorphous carbon coating to construct stable and conductive network. The porous construction can alleviate the stress and strain caused by the current impact through deformation. Furthermore, ex-situ EIS reveals the highly conductive carbon skeleton can significantly reduce the surface resistance and result in an increase of effective voltage to promote the de-intercalation of Na+. Moreover, the ex-situ X-ray photoelectron spectroscopy (XPS) at different potentials confirms the stabilized existence of VOC bonds. Benefiting from the unique carbon skeleton, the PC-NVP releases capacity of 116.9 mAh g−1 at 0.1C. Even at 120C, PC-NVP still exhibits a high capacity of 84.7 mAh g−1, retaining a value of 41.3 mAh g−1 after 16,000 cycles, corresponding to a low decay rate of 0.0032% per cycle.

Thermal performance analysis of liquid cooling system with hierarchically thermal conductive skeleton for large-scaled cylindrical battery module in harsh working conditions

Liquid cooling (LC) technology is most widely used in battery thermal management systems. However, for cylindrical battery modules, tailor-made LC components with curved surface and complicated LC structures are required to match the curved surface of the cells. Herein, we design an easily-assembled LC structure by directly embedding thermal conductive silica gel (SG) into a 21.6 V/39Ah cylindrical battery module with thermal conductive plates (TCPs) connected to LC plates (LCPs). This LC strategy avoids the tedious and costly procedure of processing LC components with special specifications, and demonstrates excellent adaptability to battery modules with diversified specifications. By selecting copper plates and flexible SG with 2 wt% expanded graphite as the TCPs and embedding material respectively, a high-efficient thermal conductive skeleton can be constructed, endowing the module center with a greatly reduced thermal resistance of 1.27 × 10−2 m2∙K∙W − 1. In addition, the optimal water inlet velocity and cell distance are determined to be 0.2 m∙s − 1 and 7 mm, respectively. As a result, the maximum temperature (Tmax) and temperature difference (ΔTmax) of the battery module are well maintained within the optimal ranges of 28.9∼41.7 °C and 1.4∼4.7 °C under all working conditions, respectively. Remarkably, even under the harsh working conditions with a 3 C discharge rate under 25, 35 and 40 °C, the Tmax can be controlled below 31.6, 40.3 and 41.7 °C, while the corresponding ΔTmax are only 4.6, 3.8 and 3.8 °C, respectively.

Highly thermally conductive and insulating PET nonwoven fabric/PDMS sandwich composite film by synergism of boron nitride nanosheets and alumina particles

AbstractThe accumulation of heat in electronic devices puts forward an urgent demand for thermal interface materials. It is still a great challenge to achieve the good comprehensive performance of high thermal conductivity (TC), insulation, flexibility and tensile strength. In this work, polyester‐based nonwoven fabric (NWF) was coated with boron nitride nanosheets (BNNS) by dispersion and interfacial reinforcement of cellulose nanofibers to obtain a three‐dimensional thermally conductive network skeleton (BNNS@NWF). The sandwich‐structured composite film was assembled by introducing alumina (Al2O3)/polydimethylsiloxane (PDMS) layers on the top and bottom surfaces of BNNS@NWF using scratch coating and hot pressing processes. The composite film has a high TC of 6.42 W/mK at 45.8 wt% BNNS content, and has excellent insulation with a volume resistivity of 1.06 × 1015 Ω cm. This is due to the long‐range effective thermal conduction path constructed by BNNS, the bridging effect of Al2O3 and the synergistic effect of the two fillers. PDMS helps the composite film maintain good flexibility and good TC stability after 30 bending cycles. The PET nonwoven interlayer gives the composite film good mechanical properties with a tensile strength of 17.5 MPa. This work provides a strategy for the efficient preparation of flexible composite films with high TC and insulation properties, which is of great importance for the development of innovative thermal interface materials.Highlights A sandwich‐structured composite film was prepared by a simple scale‐up method. Al2O3 and BNNS achieves synergistic enhancement of thermal conductivity. The film has a high thermal conductivity of 6.42 W/mK and electrical insulation. The film shows good flexibility, high tensile and thermal management properties.

Preparation of 3D BN-BT/PVDF skeleton structure composites for high thermal conductivity and energy storage

To obtain high energy storage dielectric materials with high thermal conductivity for electronic devices, we designed and constructed three-dimensional (3D) BN-BT/PVDF skeleton structure composites based on the ice template method and freeze-drying technology. Phonon thermal conductivity and intrinsic thermal conductivity can be improved by the hexagonal boron nitride (h-BN) thermal conductive skeleton orientation along the ice crystal on nanoscale. The 3D BN-BT/PVDF skeleton structure composites with high thermal conductivity and high energy storage can be obtained by impregnating the barium titanate (BT) modified polyvinylidene fluoride (PVDF) precursor into a 3D thermal conductive skeleton. When the h-BN content is 25 wt%, the comprehensive performance of BN-BT/PVDF composite are the most excellent with the energy storage density of 2.6355 J/cm3, which is 5.64 times of pure PVDF, and the thermal conductivity can reach 0.302 W/(m·K), an improvement of 152%, showing a promising industrial application prospects.

Construction of Microporous Zincophilic Interface for Stable Zn Anode.

Aqueous zinc ion batteries (AZIBs) are promising electrochemical energy storage devices due to their high theoretical specific capacity, low cost, and environmental friendliness. However, uncontrolled dendrite growth poses a serious threat to the reversibility of Zn plating/stripping, which impacts the stability of batteries. Therefore, controlling the disordered dendrite growth remains a considerable challenge in the development of AZIBs. Herein, a ZIF-8-derived ZnO/C/N composite (ZOCC) interface layer was constructed on the surface of the Zn anode. The homogeneous distribution of zincophilic ZnO and the N element in the ZOCC facilitates directional Zn deposition on the (002) crystal plane. Moreover, the conductive skeleton with a microporous structure accelerates Zn2+ transport kinetics, resulting in a reduction in polarization. As a result, the stability and electrochemical properties of AZIBs are improved. Specifically, the ZOCC@Zn symmetric cell sustains over 1150 h at 0.5 mA cm-2 with 0.25 mA h cm-2, while the ZOCC@Zn half-cell achieves an outstanding Coulombic efficiency of 99.79% over 2000 cycles. This work provides a simple and effective strategy for improving the lifespan of AZIBs.

Ag/Reduced Graphene Oxide/Carbon Fiber Composites as Electrodes for Highly Stable and Responsive Marine Electric Field Sensors

The increasing demand for maintenance-free, cost-effective, and high-stability flexible electrodes is highly anticipated for the research of marine electric-field sensors, and various carbon fibers (CFs) are considered the most suitable carbon-based electrode for the purpose. Nevertheless, the conventional fabrication of acidified or nitrogenized CF electrodes did not attract great attention for commercial application, which has limitations in the case of simultaneous cost-effectiveness and long-term stability. In this study, with homemade reduced graphene oxide (rGO) load, the prepared double carbon substrate Ag-rGO-CF composite electrodes have a honeycomb rGO conductive skeleton and the dispersed Ag nanoparticles via a facile hermetic oxidation process and hydrothermal method. The prepared Ag-rGO-CF composite electrode demonstrated an outstanding electrode performance, including low resistance, high electrochemical reaction rate, and stable potential with long-term stability and low cost. The electric double-layer (EDL) structure theory from the Gouy–Chapman–Stern model and double carbon substrate mechanism between CFs and rGO with the help of Ag were clarified, whose principle is to strengthen the adsorption force and electrostatic attraction of the electrode and to offset the residual charge while reducing the thickness of the electric double layer to achieve the purpose of potential balance. The Ag-rGO-CF composite electrode has presented long-term stability and high sensitivity, especially a wide application bandwidth. The Ag-rGO-CF composite electrode made in this study is a competitive candidate material as a flexible marine electrode field sensor.

Spatially Confined Fe7S8 Nanoparticles Anchored on a Porous Nitrogen-Doped Carbon Nanosheet Skeleton for High-Rate and Durable Sodium Storage.

Iron sulfides are widely explored as anodes of sodium-ion batteries (SIBs) owing to high theoretical capacities and low cost, but their practical application is still impeded by poor rate capability and fast capacity decay. Herein, for the first time, we construct highly dispersed Fe7S8 nanoparticles anchored on a porous N-doped carbon nanosheet (CN) skeleton (denoted as Fe7S8/NC) with high conductivity and numerous active sites via facile ion adsorption and thermal evaporation combined procedures coupled with a gas sulfurization treatment. Nanoscale design coupled with a conductive carbon skeleton can simultaneously mitigate the above obstacles to obtain enhanced structural stability and faster electrode reaction kinetics. With the aid of density functional theory (DFT) calculations, the synergistic interaction between CNs and Fe7S8 can not only ensure enhanced Na+ adsorption ability but also promote the charge transfer kinetics of the Fe7S8/NC electrode. Accordingly, the designed Fe7S8/NC electrode exhibits remarkable electrochemical performance with superior high-rate capability (451.4 mAh g-1 at 6 A g-1) and excellent long-term cycling stability (508.5 mAh g-1 over 1000 cycles at 4 A g-1) due to effectively alleviated volumetric variation, accelerated charge transfer kinetics, and strengthened structural integrity. Our work provides a feasible and effective design strategy toward the low-cost and scalable production of high-performance metal sulfide anode materials for SIBs.

Ni-Activated and Ni-P-Activated Porous Titanium Carbide Ceramic Electrodes as Efficient Electrocatalysts for Overall Water Splitting.

Developing electrocatalysts based on transition-metal carbides that can be utilized for commercial water splitting is a challenging endeavor. To address this challenge, we employed a novel approach that merged phase-inversion tape-casting and sintering, subsequently implementing a simple and efficient electrodeposition process, to synthesize Ni-activated and Ni-P-activated titanium carbide (Ni/TiC, Ni-P/TiC) ceramic electrodes as water splitting catalytic cathodes and anodes. These self-supported Ni/TiC and Ni-P/TiC electrodes are binder-free with abundant finger-like pores, which contribute to the formation of highly conductive skeleton and more exposed active sites for direct water splitting. These catalysts exhibit outstanding performance, superior to many reported bifunctional nickel-based catalysts supported on other substrates. Moreover, the exceptional electrocatalytic performance of the Ni/TiC and Ni-P/TiC catalysts is attributed to the synergistic effect between Ni oxides (phosphides) and TiC, as revealed by density functional theory (DFT) calculations. This self-template strategy paves the way for fabricating industrially applicable electrodes to generate hydrogen and oxygen through water splitting.

Flexible CoFe2O4 nanoparticles/N-doped carbon nanofibers membrane as self-standing anode for lithium-ion batteries

The development of new generation wearable electronic devices requires the power supply with high power density, long-term cycling performance, and excellent flexibility and mechanical stability that would enhance the durability of flexible devices during use. Herein, we designed a novel strategy for the preparation of flexible self-supporting nanofiber membrane with highly dispersed CoFe2O4 nanoparticles embedded in one-dimensional (1D) N-doped carbon nanofibers (denoted as [email protected]) by electrospinning and subsequent thermal treatment process, which possesses unique hierarchical structure containing zero-dimensional [email protected] carbon nanospheres and cross-linked three-dimensional (3D) fiber network. The rational combination of the nano-sized CFO particles with high theoretical capacity and a N-doped carbon nanofiber conductive skeleton with interconnected 3D open microstructure facilitates the robust penetration of electrolyte into the electrode, improves the overall electrical conductivity of the electrode, shortens the diffusion pathways of Li+ ions, and buffers the volume change of active materials during lithiation/delithiation. As a consequence, the optimized [email protected] exhibits relatively high electrochemical reversible capacity (611.4 mA h g−1 at 100 mA g−1 after 100 cycles) and good cycling stability, as well as satisfactory rate capability.

Construction of MoS2@reduced graphene oxide/carbon nanotubes three-dimensional network structure and its application in lithium-sulfur batteries

In order to enhance the electrochemical performance of lithium-sulfur batteries, reduced graphene oxide (rGO), and carbon nanotubes (CNTs) were used to construct a conductive and mechanical skeleton of the overall electrode composite. And molybdenum disulfide (MoS2) grew on the skeleton in situ. Thus, a composite MoS2@rGO/CNTs with a three-dimensional (3D) network structure was constructed. A series of corresponding structural characterizations and electrochemical performance tests were carried out. And the results showed that the 3D porous skeleton composed of rGO and CNTs could act as a 3D conductive network, which not only significantly improved the conductivity and structural stability of the cathode material for lithium-sulfur batteries but also provided a large number of active sites for the active substance S. MoS2 had a strong chemisorption effect on lithium polysulfides, which could effectively hinder their shuttle behavior. So, the MoS2@/CNTs/rGO/S cathode material showed good electrochemical performance. Its first discharge specific capacity was up to 1417.8 mAh/g at 0.1 C. After 200 cycles at 0.5 C, its capacity decay rate per cycle was only 0.09%. Its discharge capacity could still maintain at 803.2 mAh/g at 3 C, showing a good application prospect.

Facile fabrication of few-layer nanostructured MoSe2 entrenched on N-doped carbon as a superior anode material for high-performance potassium-ion hybrid capacitors

As an emerging class of advanced capacitor-battery hybrid energy storage and transformation devices, potassium ion hybrid capacitors (PIHCs) have become the next generation of electrochemical energy storage systems owing to their abundant ratio of raw materials and inexpensive potassium resources. However, potassium ions have backward kinetics because of their ionic radius. Therefore, the improvement of applicable materials with powerful capacity and rapid charge and discharge capabilities remains a large challenge. Here, we design simple hydrothermal synthesis methods to anchor MoSe2 nanosheets into a 3-dimensional N-doped porous carbon skeleton as a fast, durable electrode to boost energy storage for PIHCs. Specifically, highly conductive 3-dimensional N-doped porous carbon skeleton materials can efficiently alleviate the accumulation of MoSe2 nanosheets and facilitate electron diffusion. It is demonstrated that MoSe2/NC utilized as potassium ion battery anodes exhibits a reversible capacity (415.1 mA h g−1 at 100 mA g−1) and a superior rate performance (212.4 mAh g−1 at 5000 mA g−1) as a result of its unique nanostructure and powerful chemical interactions between MoSe2 nanosheets and N-doped carbon skeletons. As a result of its use of an anode of MoSe2/NC and a cathode of activated carbon, the PIHCs can provide an extremely high energy density of 136.8 Wh kg−1 accompanied by a power density of 400 W kg−1 excellent rate performance and an exceptionally long-cycle lifespan.

Enhanced performance of hybrid supercapacitors by the synergistic effect of Co(OH)2 nanosheets and NiMn layered hydroxides

A self-supporting composite electrode material with a unique three-dimensional structure was synthesized by in-situ growth of nanoscale NiMnLDH-Co(OH)2 on a nickel foam substrate via hydrothermal electrodeposition. The 3D layer of NiMnLDH-Co(OH)2 provided abundant reactive sites for electrochemical reactions, ensuring a solid and conductive skeleton for charge transfer and resulting in significant enhancement of electrochemical performance. The composite material showed a strong synergistic effect between the small nano-sheet Co(OH)2 and NiMnLDH, which promoted reaction kinetics, while the nickel foam substrate acted as a structural conductivity agent, stabilizer, and good conductive medium. The composite electrode showed impressive electrochemical performance, achieving a specific capacitance of 1870F g−1 at 1 A g−1 and retaining 87% capacitance after 3000 charge–discharge cycles, even at a high current density of 10 A g−1. Moreover, the resulting NiMnLDH-Co(OH)2//AC asymmetric supercapacitor (ASC) demonstrated remarkable specific energy of 58.2 Wh kg−1 at a specific power of 1200 W kg−1, along with outstanding cycle stability (89% capacitance retention after 5000 cycles at 10 A g−1). More importantly, DFT calculations reveal that NiMnLDH-Co(OH)2 facilitates charge transfer, accelerating surface redox reactions and increasing specific capacitance. This study presents a promising approach towards designing and developing advanced electrode materials for high-performance supercapacitors.