Ternary NiCeCo-Layered Double Hydroxides Grown on CuBr2@ZIF-67 Nanowire Arrays for High-Performance Supercapacitors

Polyaniline-modified NiCo layered double hydroxide hollow nanocages for aqueous ammonium-ion supercapacitors

Aqueous ammonium ion supercapacitors have attracted extensive attention from researchers for their environmental friendliness, high safety, and low cost. Unfortunately, compared with other energy storage technologies, the research and development of high-performance ammonium storage electrode materials is lagging, which has seriously hindered its development. Here, we designed and prepared nickel-cobalt layered double hydroxide nanocages (HLDH@P) with a unique hollow structure and polyaniline (PANI) coating, and used them as ammonium ion energy storage hosts. The optimized HLDH@P electrode material exhibits a great specific capacity of up to 1248 F g-1 at 1 A/g, while a high discharge plateau of 0.6 V is observed. The assembled asymmetric supercapacitor (A-HSC) has an energy density of 42 Wh kg-1 and a corresponding power density of 623 W kg-1, while also exhibiting excellent cycling stability. In addition, density functional theory (DFT) shows that the abundant nitrogen-containing groups in the composite material effectively increase the adsorption energy of NH4+ ions, and the large number of hydrogen bonds formed thereby greatly improve the electrochemical performance of the composite material. The results of this study fully demonstrate the broad application prospects of surface engineering in designing high-performance ammonium storage electrode materials.

Zeolitic Imidazolate Framework-67-Derived NiCoMn-Layered Double Hydroxides Nanosheets Dispersedly Grown on the Conductive Networks of Single-Walled Carbon Nanotubes for High-Performance Hybrid Supercapacitors

A supercapacitor's energy storage capability is greatly dependent on electrode materials. Layered double hydroxides (LDHs) were extensively studied as battery-type electrodes because of their 2D structure and quick intercalation/deintercalation of electrolyte ions. However, the energy storage capability for pristine LDHs is limited by their large aggregation tendency and poor electrical conductivity. Herein, a novel NiCoMn-LDH/SWCNTs (single-walled carbon nanotubes) composite electrode material, with ultrathin NiCoMn-LDH nanosheets dispersedly grown among the highly conductive networks of SWCNTs, was prepared via a facile zeolitic imidazolate framework-67 (ZIF-67)-derived in situ etching and deposition procedure. The NiCoMn-LDH/SWCNTs electrode demonstrates a specific capacitance as large as 1704.3 F g-1 at 1 A g-1, which is ascribed to its exposure of more active sites than NiCoMn-LDH. Moreover, the assembled NiCoMn-LDH/SWCNTs//BGA (boron-doped graphene aerogel) hybrid supercapacitor exhibits a superior capacitance of 167.9 F g-1 at 1.0 A g-1, an excellent energy density of 45.7 Wh kg-1 with a power density of 700 W kg-1, and an outstanding cyclic stability with 82.3% incipient capacitance maintained when subjected to 5000 charge and discharge cycles at the current density of 10 A g-1, suggesting the significant potential of NiCoMn-LDH/SWCNTs as the electrode material applicable in supercapacitors.

Innovative spherical Fe-Mn layered double hydroxides (LDH) for the degradation of sulfisoxazole through activated periodate: Efficacy and mechanistic insights

Advanced oxidation technology based on peroxides is widely regarded as an efficient method for treating emerging contaminants. However, the precise mechanism by which layered double hydroxides (LDHs) enhance oxidant activation requires further investigation. In this study, a spherical Fe-Mn LDH (S-FML) with improved crystallinity using a simple hydrothermal method. Compared to granular Fe-Mn LDH (G-FML), S-FML demonstrated superior periodate (PI) activation efficiency and outstanding stability. Intensive mechanistic studies have shown that the synergistic action of Fe2⁺ and Mn2⁺ in S-FML plays a key role in the degradation reaction. Three primary pathways for SIZ degradation and a reduction in solution toxicity post-reaction were identified through analysis of degradation intermediates and density functional theory (DFT) calculations. This research offers valuable theoretical insights and a scientific foundation for designing high-performance heterogeneous catalysts and elucidating the efficient activation mechanisms of PI for emerging pollutant treatment.

In situ construction of NiCo-layered double hydroxide nanobranches with adjustable layer spacing on micro-sized carbon plate for high-performance supercapacitors

Binary layered double hydroxides (LDHs) are an emerging class of materials for supercapacitors owing to their tunable topological structure and excellent theoretical energy storage capacity. However, aggregation and restacking cause a decrease in the interlayer distance of LDHs, resulting in a considerable drop in real specific capacitance. To address this, large-sized anions are intercalated into the interlayer space. Herein, we constructed 3D top-tangled NiCo-LDH nanobranches in situ on a biomass micro-sized carbon plate (CP). By varying the amount of benzene-1,4-dicarboxylic acid (BDC), we prepared a BDC-intercalated CP/NiCo-LDH composite material with adjustable interlayer spacing. Remarkably, the CP/NiCo-LDH-BDC(0.03) composite exhibited excellent electrochemical properties (1530 F g-1/212.5 mAh/g at 1 A/g). It retained 88.36 % capacity after 5000 charge-discharge cycles. The constructed CP/NiCo-LDH-BDC(0.03)//CP asymmetric supercapacitor showed excellent gravimetric capacitance (123 F g-1/54.7 mAh/g at 1 A/g) and energy density (43.7 Wh kg-1 at 800 W kg-1). Furthermore, two asymmetric capacitors connected in series powered a small lightbulb for 2 min, even in a bent state. These findings show that the fabricated CP and CP/NiCo-LDH-BDC(0.03) electrode materials can be applied in flexible and wearable energy storage systems.

One-Step Synthesis of NiCo-LDH@Ni(OH)2 Heterostructure Foams on Biomass-Derived Porous Carbon for High-Performance Supercapacitors

Layered double hydroxides (LDHs) have attracted much attention as pseudocapacitor supercapacitor electrodes because of their high theoretical specific capacity. However, LDHs have drawbacks such as poor electrical conductivity, and their specific capacities are lower than the theoretical values. In this work, NNCLDH@OPC electrodes are constructed via in situ synthesis of heterostructure foams (NNCLDH) consisting of NiCo-LDH and Ni(OH)2 on pomelo peel-derived porous carbon (OPC) through a one-step solvothermal method using ZIF-67 as a template. Owing to the synergistic effect of the 3D nanofoam structure and the multicomponent heterostructure as well as the conductive porous carbon support, the NNCLDH/OPC exhibited ultrahigh electrochemical performance as well as excellent cycling stability: a specific capacity of 3290 F g-1 at 1 A g-1 and a capacitance retention of 77.8% after 4000 cycles at a current density of 10 A g-1. In addition, the assembled NNCLDH@OPC//OPC asymmetric supercapacitor (ASC) has a maximum energy density of 51 Wh kg-1 with a power density of 812 W kg-1 and a maximum power density of 16 kW kg-1 at a current density of 20 A g-1. These results demonstrate the significant application potential of NNCLDH/OPC composites in supercapacitor electrodes.

Ni,S co-doped Cu dendrites decorated with core-shell architecture assisted by MOF and Fe0.92Co0.08S nanoflakes on nanocellulose/graphene fibers for fabrication of flexible wire-type micro-supercapacitor

One-dimensional micro-supercapacitors (1D micro-SCs) have been regarded as an efficient energy storage system to fulfill the ever-growing need for miniaturized electronics. Designing multi-dimensional nanoarchitectures on fibrous microelectrodes is an effective strategy to build a high-performance 1D micro-SC. In this work, Ni,S-doped Cu was firstly prepared on Cu wire as a micro-sized 1D current collector through Cu electrodeposition using a H2 bubble template and then co-doped with nickel and sulfur. Benefiting from the high electrical/thermal conductivity of Cu, and the highly electroactive sites of Ni and S as well as the 3D porous architecture, the deposited Ni,S-doped Cu provided a platform for growing active substances. Thereafter, cobalt carbonate hydroxide (CoCH) pine-like nanoneedle integrated ZIF-67 polyhedrons were synthesized on a foam-like skeleton and converted into NiMoCo-layered triple hydroxide (LTH)/Ni,S-doped Cu shish-kebab type nanoarrays by applying a hydrothermal method. Finally, Ni2Mo3N-CoN/Ni,S-doped Cu was prepared via nitridation. The potent interactions and synergy between components realized a well-organized hybrid nanoarchitecture consisting of dodecahedrons decorated on needle-like arrays within a 3D framework with rich redox properties, rapid ion/electron transfer dynamics and high electroactivity. In comparison to the LTH obtained from the electrodeposition method (without the ZIF-67 precursor) and that derived from leaf-like ZIF-Co, this modified microfiber exhibited a high charge storage capacity of 1.5 mA h cm-2 (149.9 mA h cm-3 and 0.187 mA h cm-1) at 4 mA cm-2 and possesses an excellent durability of 98.4% after 5000 cycles. Additionally, FeCoS nanoflakes were electrodeposited using carbon fiber coated with an rGO-nanocellulose hydrogel (GNCH) and employed as a negative 1D microelectrode, which delivered a high specific capacitance of 1223 mF cm-2 (83 F cm-3, 232.4 mF cm-1) at 4 mA cm-2 with a superior cyclic lifespan. Ultimately, the assembled 1D flexible micro-device (Ni2Mo3N-CoN/Ni,S-doped Cu@CW//FeCoS/GNCH@CF) yielded an energy density of 7.2 mW h cm-3 at a power density of 294 mW cm-3 and outstanding cycling stability in PVA/KOH electrolyte and preserved the capacitive performance under various bending states. This research highlights that assembled 1D micro-SCs have a high potency for next-generation portable/wearable energy-supply microelectronics.

Enhanced electrocatalytic activity in MOFs-derived 3D hollow NiCo-LDH nanocages decorated porous biochar for simultaneously ultra-sensitive electrochemical sensing of Cu2+ and Hg2

Layered double hydroxides (LDHs) have attracted significant attention due to their compositional and structural flexibility. However, it is challenging but meaningful to design and fabricate hierarchical mixed-dimensional LDHs with synergistic effects to increase the electrical conductivity of LDHs and promote the intrinsic activity. Herein, 3D hollow NiCo-LDH nanocages decorated porous biochar (3D NiCo-LDH/PBC) has been synthesized by using ZIF-67 as precursor, which was utilized for constructing electrochemical sensing platform to realize simultaneous determination of Cu2+ and Hg2+. The 3D NiCo-LDH/PBC possessed the characteristics of hollow material and three-dimensional porous material, revealing a larger surface area, more exposed active sites, and faster electron transfer, which is beneficial to enhancing its electrochemical performance. Consequently, the developed sensor displayed good performance for simultaneously detecting Cu2+ and Hg2+ with ultra-low limit of detection (LOD) of 0.03 μg L-1 and 0.03 μg L-1, respectively. The proposed sensor also demonstrated excellent stability, repeatability and reproducibility. Furthermore, the sensor can be successfully used for the electrochemical analysis of Cu2+ and Hg2+ in lake water sample with satisfactory recovery, which is of great feasibility for practical application.

High performance supercapacitors deploying cube-templated tracheid cavities of wood-derived carbon

Wood-derived carbon, with its strong tracheid array structure, is an ideal material for use as a self-supporting electrode in supercapacitors. By leveraging the inherent through pore structure and surface affinity found in wood tracheids, we successfully engineered a highly spatially efficient cube-templated porous carbon framework inside carbonized wood tracheid cavities through precise control over precursor crystallization temperatures. This innovative cubic channel architecture effectively maximizes up to (79 ± 1)% of the cavity volume in wood-derived carbon while demonstrating exceptional hydrophilicity and high conductivity properties, facilitating the development of supercapacitors with enhanced areal/volumetric capacitances (2.65F cm-2/53.0F cm-3 at 5.0 mA cm-2) as well as superior areal/volumetric energy densities (0.37 mWh cm-2/7.36 mWh cm-3 at 2.5 mW cm-2). The fabrication of these cube-templated channels with high cube filling content is not only simple and precisely controllable, but also environmentally friendly. The proposed method eliminates the conventional acid-base treatment process for pore formation, facilitating the rapid development and practical implementation of thick electrodes with superior performance in supercapacitors. Moreover, it offers a universal research approach for the commercialization of wood-derived thick electrodes.

N-doped porous carbon with ZIF-67-derived CoFe2O4-Fe particles for supercapacitors

The development of novel materials for electrodes with high energy densities is essential to the advancement of energy storage technologies. In this study, N-doped layered porous carbon with ZIF-67-derived binary CoFe2O4-Fe particles was successfully fabricated by the pyrolysis of an Fe-based chitosan (CS) hydrogel mixed with ZIF-67 particles. Various characterization techniques were employed to assess the performance of the prepared porous CoFe2O4-Fe@NC composite. This composite exhibits excellent performance owing to the effective combination of multivalent CoFe2O4-Fe particles derived from ZIF-67 with N-doped porous carbon substances with a high surface area, which helps to accelerate ion and charge transfer. The specific capacitance of the CoFe2O4-Fe@NC composite carbonized at 700 °C reached 3960.9F/g at 1 A/g. When this composite is combined with activated carbon (AC) to construct an asymmetric supercapacitor (ASC), a density of energy of up to 84.9 W h kg-1 is attained at a power capacity of 291.6 W kg-1. Moreover, this composite maintained a capacitance retention of up to 94.9 % after 10,000 cycles. This work offers new perspectives on high-performance supercapacitors and their applications.

In Situ Construction of NiCoMn-LDH Derived from Zeolitic Imidazolate Framework on Eggshell-Like Carbon Skeleton for High-Performance Flexible Supercapacitors

Active compounds based on LDH (ternary layered double hydroxide) are considered the perfect supercapacitor electrode materials on account of their superior electrochemical qualities and distinct structural characteristics, and flexible supercapacitors are an ideal option as an energy source for wearable electronics. However, the prevalent aggregation effect of LDH materials results in significantly compromised actual specific capacitance, which limits its broad practical applications. In this research, a 3D eggshell-like interconnected porous carbon (IPC) framework with confinement and isolation capability is designed and synthesized by using glucose as the carbon source to disperse the LDH active material and enhance the conductivity of the composite material. Second, by constructing NiCoMn-LDH nanocage structure based on ZIF-67 (zeolitic imidazolate framework-67) at the nanometer scale the obtained IPC/NiCoMn-LDH electrode material can expose more active sites, which allows to achieve excellent specific capacitance (2236 F g-1/ 310.6 mAh g-1 at 1 A g-1), good rate as well as the desired cycle stability (85.9% of the initial capacitance upon 5000 cycles test). The constructed IPC/NiCoMn-LDH//IPC ASC (asymmetric supercapacitor) exhibits superior capacitive property (135 F g-1/60.1 mAh g-1 at 0.5 A g-1) as well as desired energy density (40 Wh kg-1 at 800 W kg-1).

In Situ Fabrication of Hierarchical CuO@CoNi-LDH Composite Structures for High-Performance Supercapacitors

Layered double hydroxide (LDH) materials, despite their high theoretical capacity, exhibit significant performance degradation with increasing load due to their low conductivity. Simultaneously achieving both high capacity and high rate performance is challenging. Herein, we fabricated vertically aligned CuO nanowires in situ on the copper foam (CF) substrate by alkali-etching combined with the annealing process. Using this as a skeleton, electrochemical deposition technology was used to grow the amorphous α-phase CoNi-LDH nanosheets on its surface. Thanks to the high specific surface area of the CuO skeleton, ultrahigh loading (̃16.36 mg cm-2) was obtained in the fabricated CF/CuO@CoNi-LDH electrode with the cactus-like hierarchical structure, which enhanced the charge transfer and ion diffusion dynamics. The CF/CuO@CoNi-LDH electrode achieved a good combination of high areal capacitance (33.5 F cm-2) and high rate performance (61% capacitance retention as the current density increases 50 times). The assembled asymmetric supercapacitor device demonstrated a maximum potential window of 0-1.6 V and an energy density of 1.7 mWh cm-2 at a power density of 4 mW cm-2. This work provides a feasible strategy for the design and fabrication of high-mass-loading LDH composites for electrochemical energy storage applications.

In situ selective selenization of ZIF-derived CoSe2 nanoparticles on NiMn-layered double hydroxide@CuBr2 heterostructures for high performance supercapacitors

As an emerging energy storage device, the practical application of supercapacitors (SCs) is currently constrained by their low energy density. Enhancing the capacitance of supercapacitors by leveraging the synergistic effect of multiple components in composite electrodes with well-designed structures can effectively increase their energy density. Here, a wire-sheet-particle hierarchical heterostructured CoSe2@NiMn-layered double hydroxide (NiMn-LDH) @Cu1.8Se/Copper foam (CF) electrode is synthesized via phase pseudomorphic transformation process achieved by selective selenization for Cu and Co elements. Benefiting from the stable support structure of CuBr2, the large specific surface area of NiMn-LDH, and the excellent conductivity of CoSe2, the prepared binder-free electrode shows excellent electrochemical properties. The CoSe2@NiMn-LDH@Cu1.8Se hybrid electrode exhibits a superior specific areal capacitance of 7064 mF cm-2 at 2 mA cm-2 and a stable cyclic performance with 80.11 % capacitance retention after 10,000 cycles. Furthermore, the assembled CoSe2@NiMn-LDH@Cu1.8Se/CF//AC (activated carbon) asymmetric supercapacitor (ASC) achieves an energy density of 36.6 Wh kg-1 when the power density is 760.6 W Kg-1 and retains 87.35 % of the initial capacitance after 5000 cycles. Overall, this pioneering research provided new insight for preparing supercapacitor electrode materials by selective selenization and ration design of the structures.

High-mass-loading cobalt iron phosphide@nickel vanadium layered double hydroxide heterogeneous nanosheet arrays for hybrid supercapacitors

Designing multidimensional heterostructures on flexible substrates is an efficient approach to resolve the low energy density of supercapacitors. Herein, a three-dimensional (3D) porous cobalt iron phosphide (CoFeP)@nickel vanadium-layered double hydroxide (NiV-LDH) heterostructure has been prepared anchored on carbon cloth (CC) substrate. In this nanoarchitecture, NiV-LDH nanosheets are densely wrapped on the surface of CoFeP nanosheets, which forms a hierarchically porous framework with an enlarged surface area and accessible pore channels. Benefiting from the strong interaction and synergistic effect between CoFeP and NiV-LDH, the well-defined heterostructure can realize simultaneously rich redox active sites, rapid reaction dynamics, and good structural stability. Thus, the binder-free CoFeP@NiV-LDH electrode with a high mass loading of 6.47 mg cm-2 displays a significantly increased specific capacity of 903.1C g-1 (2.35C cm-2) at 1 A g-1 and enhanced rate capability when compared to pristine CoFeP and NiV-LDH. Additionally, the assembled hybrid supercapacitor (HSC) yields an energy density of 77.9 Wh kg-1/0.98 Wh cm-2 and excellent long-term stability. This research proposes a rational route for designing heterogeneous micro-/nanoarchitectures with commercial-level mass loading for the practical application of high-energy-density supercapacitors.

Pulsed laser welding of macroscopic 3D graphene materials

Welding is a key missing manufacturing technique in graphene science. Due to the infusibility and insolubility, reliable welding of macroscopic graphene materials is impossible using current diffusion-bonding methods. This work reports a pulsed laser welding (PLW) strategy allowing for directly and rapidly joining macroscopic 3D porous graphene materials under ambient conditions. Central to the concept is introducing a laser-induced graphene solder converted from a designed unique precursor to promote joining. The solder shows an electrical conductivity of 6700 S m-1 and a mechanical strength of 7.3 MPa, over those of most previously reported porous graphene materials. Additionally, the PLW technique enables the formation of high-quality welded junctions, ensuring the structural integrity of weldments. The welding mechanism is further revealed, and two types of connections exist between solder and base structures, i.e., intermolecular force and covalent bonding. Finally, an array of complex 3D graphene architectures, including lateral heterostructures, Janus structures, and 3D patterned geometries, are fabricated through material joining, highlighting the potential of PLW to be a versatile approach for multi-level assembly and heterogeneous integration. This work brings graphene into the laser welding club and paves the way for the future exploration of the exciting opportunities inherent in material integration and repair.

Metal-Organic Frameworks and Their Derivatives-Based Nanostructure with Different Dimensionalities for Supercapacitors

With the urgent demand for the achievement of carbon neutrality, novel nanomaterials, and environmentally friendly nanotechnologies are constantly being explored and continue to drive the sustainable development of energy storage and conversion installations. Among various candidate materials, metal-organic frameworks (MOFs) and their derivatives with unique nanostructures have attracted increasing attention and intensive investigation for the construction of next generation electrode materials, benefitting from their unique intrinsic characteristics such as large specific surface area, high porosity, and chemical tunability as well as the interconnected channels. Nevertheless, the poor electrochemical conductivity severely limits their application prospects, hence a variety of nanocomposites with multifarious structures have been designed and proposed from different dimensionalities. In this review, recent advances based on MOFs and their derivatives in different dimensionalities ranging from 1D nanopowders to 2D nanofilms and 3D aerogels, as well as 4D self-supporting electrodes for supercapacitors are summarized and highlighted. Furthermore, the key challenges and perspectives of MOFs and their derivatives-based materials for the practical and sustainable electrochemical energy conversion and storage applications are also briefly discussed, which may be served as a guideline for the design of next-generation electrode materials from different dimensionalities.

Hierarchical NiCo@NiOOH@CoMoO4 Core-Shell Heterostructure on Carbon Cloth for High-Performance Asymmetric Supercapacitors

The fabrication of low-cost, effective, and highly integrated nanostructured materials through simple and reproducible methods for high-energy-density supercapacitors is highly desirable. Herein, an activated carbon cloth (ACC) is designed as the functional scaffold for supercapacitors and treated hydrothermally to deposit NiCo nanoneedles working as internal core, followed by a dip-dry coating of NiOOH nanoflakes core-shell and uniform hydrothermal deposition of CoMoO4 nanosheets serving as an external shell. The structured core-shell heterostructure ACC@NiCo@NiOOH@CoMoO4 electrode resulted in exceptional specific areal capacitance of 2920 mF cm-2 and exceptional cycling stability for 10 000 cycles. Moreover, the fabricated electrode is developed into an asymmetric supercapacitor which demonstrates excellent areal capacitance, energy density, and power density within the broad potential window of 1.7 V with a cycling life of 92.4% after 10 000 charge-discharge cycles, which reflects excellent cycle life. The distinctive core-shell structure, highly conductive substrate, and synergetic effect of coated material results in more electrochemical active sites and flanges for effective electrons and ion transportation. This unique technique provides a new perspective for cost-efficient supercapacitor applications.

Interlayer Nano-Dots Induced High-Rate Supercapacitors

The fast OH- transfer between hydroxide layers is the key to enhancing the charge storage efficiency of layered double hydroxides (LDH)-based supercapacitors (SCs). Constructing interlayer reactive sites in LDH is much expected but still a huge challenge. In this work, CdS nano-dots (NDs) are introduced to interlayers of ultra-thin NiFe-LDH (denoted CdSinter. -NiFe-LDH), promoting the interlayer ions flow for higher redox activity. The excellent performance is not only due to the enlarged layer spacing (from 0.70 to 0.81 nm) but also stems from anchored interlayer reactive units and the undamaged original layered structure of LDH, which contribute to the improvement of OH- diffusion coefficient (1.6 × 10-8  cm2  s-1 ) and electrochemical active area (601 mF cm-2 ) better than that of CdS NDs on the surface of NiFe-LDH (2.1 × 10-9  cm2  s-1 and 350 mF cm-2 ). The champion CdSinter. -NiFe-LDH electrode displays high capacitance of 3330.0 F g-1 at 1 A g-1 and excellent retention capacitance of 90.9% at 10 A g-1 , which is better than the NiFe-LDH with CdS NDs on the surface (1966.6 F g-1 ). Moreover, the assembled     asymmetric SCs (ASC) device demonstrate an outstanding energy density/power density (121.56 Wh kg-1 /754.5 W kg-1 ).

Electrochemically activated 3D Mn doped NiCo hydroxide electrode materials toward high-performance supercapacitors

Metal doping and electrochemical reconstruction had been demonstrated to play a significant role in the preparation of advanced electrode materials, which is helpful to achieve high-performance supercapacitors. However, there was no report about the combination of two technologies to construct electrode materials and their applications in supercapacitors. Herein, a rational Mn doped NiCo sulfide compound with open structure composed of 2D ultra-thin nanosheets was designed via a Mn doping route. In order to further improve the energy storage performance of the resulted product, we adopted a simple electrochemical activation strategy to reconstruct it. It was found that the reconstructed sample not only exhibited an irreversible evolution of structure (from 2D sheet to 3D channel), but also the phase transformation (from metal sulfide to metal hydroxide). Benefiting from the stable 3D curved structure with numerous channels, multitudinous charge transfer provided by numerous valence states of metals and copious active sites by low crystalline state, the in-situ self-reconstructed sample exhibited superior capacitance. In details, the optimized product delivered excellent specific capacitance of 1462C g^-1 (3655F/g) at 1 A g^-1 and high rate capability of 66 % even at 5 A g^-1. Moreover, the corresponding assembled asymmetric supercapacitor exhibited an excellent energy density of 141.8 Wh kg^-1 at a power density of 850.1 W kg^-1, and the capacitance retention rate was 96.6 % even after 5000 cycles, which was distinctly superior than thoseofthe previous similarmaterialsreported. In a word, this work provided a feasible and effective strategy to construct 3D Mn doped NiCo hydroxide electrode materials toward high-performance supercapacitors.

Interface engineered hydrangea-like ZnCo2O4/NiCoGa-layered double hydroxide@polypyrrole core-shell heterostructure for high-performance hybrid supercapacitor

Rationally constructing advanced battery-type electrodes with hierarchical core-shell heterostructure is essential for improving the energy density and cycling stability of hybrid supercapacitors. Herein, this work successfully constructs hydrangea-like ZnCo₂O₄/NiCoGa-layered double hydroxide@polypyrrole (denoted as ZCO/NCG-LDH@PPy) core-shell heterostructure. Specifically, the ZCO/NCG-LDH@PPy employs ZCO nanoneedles clusters with large open void space and rough surfaces as the core, and NCG-LDH@PPy composite as the shell, comprising hexagonal NCG-LDH nanosheets with rich active surface area, and conductive PPy films with different thicknesses. Meanwhile, density functional theory (DFT) calculations authenticate the charge redistribution at the heterointerfaces between ZCO and NCG-LDH phases. Benefiting from the abundant heterointerfaces and synergistic effect among different active components, the ZCO/NCG-LDH@PPy electrode acquires an extraordinary specific capacity of 381.4 mAh g^-1 at 1 A g^-1, along with excellent cycling stability (89.83% capacity retention) after 10,000 cycles at 20 A g^-1. Furthermore, the prepared ZCO/NCG-LDH@PPy//AC hybrid supercapacitor (HSC) exhibits a remarkable energy density (81.9 Wh kg^-1), an outstanding power density (17,003.7 W kg^-1), and superior cycling performance (a capacitance retention of 88.41% and a coulombic efficiency of 93.97%) at the end of the 10,000th cycle. Finally, two ZCO/NCG-LDH@PPy//AC HSCs in series can light up a LED lamp for 15 min, indicating its excellent application prospects.

In Situ Generation of Vertically Crossed P-Cu3Se2 Ultrathin Nanosheets Derived from Cu2S Nanorod Arrays for High-Performance Supercapacitors

Transition-metal selenides (TMSs) have great potential in the synthesis of supercapacitor electrode materials due to their rich content and high specific capacity. However, the aggregation phenomenon of TMS materials in the process of charging and discharging will cause capacity attenuation, which seriously affects the service life and practical applications. Therefore, it is of great practical significance to design simple and efficient synthesis strategies to overcome these shortcomings. Hence, P-doped Cu₃Se₂ nanosheets are loaded on vertically aligned Cu₂S nanorod arrays to synthesize CF/Cu₂S@Cu₃Se₂/P nanocomposites with a unique core-shell heterostructure. Notably, the Cu₂S precursors can be rapidly converted into Cu₃Se₂ nanorod arrays in situ in just 30 min at room temperature. The unique core-shell heterostructure effectively avoids the aggregation phenomenon, and the doped P elements further enhance the electrochemical properties of the electrode materials. Therefore, the as-prepared CF/Cu₂S@Cu₃Se₂/P electrode exhibits a high areal capacitance of 5054 mF cm^-2 (1099 C g^-1) at 3 mA cm^-2 and still retains 90.2% capacitance after 10 000 galvanostatic charge-discharge (GCD) cycles. The asymmetric supercapacitor (ASC) device assembled from synthetic CF/Cu₂S@Cu₃Se₂/P and activated carbon (AC) possesses an energy density of 41.1 Wh kg^-1 at a power density of 480.4 W kg^-1. This work shows that the designed CF/Cu₂S@Cu₃Se₂/P electrode has broad application prospects in the field of electrochemical energy storage.