Retention Of Initial Capacitance Research Articles

Core-shell NiCo2S4@C with three dimensional carbon frameworks for enhanced asymmetrical supercapacitor and lithium storage performance

Transition-metal sulfides have been considered as promising candidates for electrochemical supercapacitor and lithium ion batteries. Unfortunately, the shortcomings including large volume change, low conductivity as well as severe structural exfoliation from conductive substrate or current collector inhibit their practical application. Herein, the hydrothermal and solvothermal approach are developed for the controllable synthesis of core-shell NiCo2S4@C with three dimensional carbon frameworks. As an asymmetric supercapacitor, the NiCo2S4@C/YP-50 F displays a high energy density of 46.7 Wh kg−1 at a power density of 0.8 kW kg−1 and the good cycling stability (∼110 % of the initial capacitance retention at 16 kW kg−1 over 2000 cycles). Furthermore, the NiCo2S4@C exhibits the specific capacity of 414 mAh g−1 after 500 cycles at 2000 mA g−1 when evaluated as anode for lithium ion batteries. The excellent performance can be ascribed to the core-shell structure and the three dimensional carbon frameworks. The synthetic approach can be extended to fabricate other high performance metal sulfides for energy storage.

Building Flame-Retardant Polymer Electrolytes via Microcapsule Technology for Stable Lithium Batteries.

Flame retardants could improve the safety properties of lithium batteries (LBs) with the sacrifice of electrochemical performance due to parasitic reactions. To concur with this, we designed thermal-response clothes for hexachlorophosphazene (HCP) additives by the microcapsule technique with urea-formaldehyde (UF) resin as the shell. HCP@UF combines with polyacrylonitrile (PAN) by hydrogen bonds successfully to form PAN-HCP@UF as the flame-retardant solid polymer electrolyte. The hydrogen bonds ensure excellent mechanical properties of the polymer electrolyte. The multiscale free radical-annihilating agent HCP effectively eliminates hydrogen free radicals of electrolytes under high temperature, showing excellent flame retardation. During the operation of the battery, functional groups on the UF resin act as active sites to promote the migration of lithium ions, while the internal HCP is protected from electrochemical reaction. With 25% HCP@UF addition, the limiting oxygen index of the PAN-HCP@UF increases to 28% and the Li+ transfer number up to 0.80. By UF protection, the initial capacity retention rate of the Li||LFP battery that assembles with PAN-HCP@UF is 88.8% after 500 cycles at 0.5 C. Thus, the microcapsule-encapsulated approach is deemed to provide an innovative strategy to prepare high-safety solid-state LB with a stable long cycle life.

Modulating solvated structure of Zn2+ and inducing surface crystallography by a simple organic molecule with abundant polar functional groups to synergistically stabilize zinc metal anodes for long-life aqueous zinc-ion batteries

Aqueous zinc-ion batteries (AZIBs) have attracted significant attention owing to their inherent security, low cost, abundant zinc (Zn) resources and high energy density. Nevertheless, the growth of zinc dendrites and side reactions on the surface of Zn anodes during repeatedly plating/stripping shorten the cycle life of AZIBs. Herein, a simple organic molecule with abundant polar functional groups, 2,2,2-trifluoroether formate (TF), has been proposed as a high-efficient additive in the ZnSO4 electrolyte to suppress the growth of Zn dendrites and side reaction during cycling. It is found that TF molecules can infiltrate the solvated sheath layer of the hydrated Zn2+ to reduce the number of highly chemically active H2O molecules owing to their strong binding energy with Zn2+. Simultaneously, TF molecules can preferentially adsorb onto the Zn surface, guiding the uniform deposition of Zn2+ along the crystalline surface of Zn(002). This dual action significantly inhibits the formation of Zn dendrites and side reactions, thus greatly extending the cycling life of the batteries. Accordingly, the Zn//Cu asymmetric cell with 2 % TF exhibits stable cycling for more than 3,800 cycles, achieving an excellent average Columbic efficiency (CE) of 99.81 % at 2 mA cm−2/1 mAh cm−2. Meanwhile, the Zn||Zn symmetric cell with 2 % TF demonstrates a superlong cycle life exceeding 3,800 h and 2,400 h at 2 mA cm−2/1 mAh cm−2 and 5 mA cm−2/2.5 mAh cm−2, respectively. Simultaneously, the Zn//VO2 full cell with 2 % TF possesses high initial capacity (276.8 mAh/g) and capacity retention (72.5 %) at 5 A/g after 500 cycles. This investigation provides new insights into stabilizing Zn metal anodes for AZIBs through the co-regulation of Zn2+ solvated structure and surface crystallography.

3D Architecting triple gradient graphene-based fiber electrode for high-performance asymmetric supercapacitors

High-performance fibrous architectures and controllable fabrication methods for active nanomaterials are fundamental in the development of fiber-based supercapacitors (FSCs). Herein, we rationally designed a triple gradient structured fibrous electrode based on three-dimensional (3D) architectural approach with Ni3S2 nanoflakes (Ni3S2 NFs) in situ growth on Ni-coated graphene fiber (Ni3S2-NiGFs) for highly energy-dense asymmetric supercapacitors. Remarkably, the Ni-metal coating imparted the Ni3S2-NiGFs exceptional electrical conductivity (619.8 S cm−1), mechanical strength (335.0 MPa), and flexibility without significantly compromising its density. Moreover, the unique 3D interconnected ultrathin Ni3S2 NFs significantly increase the contact area between the electrode and the electrolyte solution, providing abundant redox activity to facilitate ion transport and accumulation. Therefore, the fibrous electrode showcased a remarkable areal specific capacitance of 1387.6 mF cm−2 at 3 mA cm−2 in 3 M KOHaq electrolyte, while its asymmetric FSCs delivered an impressive areal energy density of 15.6 μW h cm−2 at power density of 1.0 mW cm−2 along with durable cycle life (86.7 % of the initial specific capacitance retention over 10,000 cycles). In summary, the featured work provides a facile but robust electrode design to realize highly energy-dense flexible energy storage devices for next-generation wearable industries.

Designing intimately interconnected neuron-shaped nickel-copper(I) sulfide nanocomposites as cathode material for supercapacitors

Nanostructured transition metal sulfides have attracted significant attention as pseudocapacitance materials owing to their high specific capacitance and improved conductivity compared to oxides. Bimetallic nickel‑copper(I) (NiCu) sulfides are promising candidates for use in asymmetric supercapacitors because of their high specific capacitance, wide voltage range, and high conductivity. In this study, we synthesize neuron-shaped Ni-Cu(I) sulfide nanocomposites with intimate interconnectivity via the sulfidation and ion exchange of Ni-Cu(I) carbonate hydroxide, prepared by a straightforward hydrothermal process. The product's unique structure, featuring a neuronal network, exhibits a high specific capacitance of 1226.5 F g−1 at 1 A g−1 and an excellent cycling stability (88.97 % capacitance retention after 5000 cycles), which is attributed to the coexistence of bimetallic components and an inherently interconnected neuron-shaped configuration that prevents structural collapse and self-aggregation, while providing easy electrolyte accessibility. Furthermore, an asymmetric supercapacitor with a Ni-Cu(I) sulfide cathode material demonstrates a maximum power and energy densities of 9000 W kg−1 and 23.99 Wh kg−1, respectively, with an initial capacity retention rate of 83.69 % after 5000 cycles. The distinctive structural features of Ni-Cu(I) sulfides enhance the energy storage capabilities of the nanomaterials, enabling the development of portable electronic devices.

Enhancing aqueous zinc-ion batteries: The role of copper-ion-doped Mn3O4 as cathode material

It is widely recognized that manganese-based cathode materials are the most prospective cathode energy storage materials among zinc ion batteries. While rapid capacity decay and structural instability are the main hindrance in the rapid advancement of Manganese based materials. It has been established that ion doping is an accurate lever to enhance the stability of the structure and cycling performance of manganese-based materials. In this work, copper ions were selected as doping of Mn3O4 to mitigate obstacle of H+/Zn2+ extraction/insertion by expanding the lattice spacing of Mn3O4. The results show that Cu2+ doping results in a significant improvement in the properties of Mn3O4 (CMO). After 600 cycles at a current density of 1 A g−1, the initial capacity retention rate of Mn3O4 without doping is only 35.4 %, while the CMO achieves a capacity retention rate of 98.9 % (capacity retention of 166 mAh g−1). In addition, the CMO obtains a high specific capacity of 360 mAh g−1 at 0.1 A g−1. The significant difference in electrochemical properties between CMO and Mn3O4 indicates that Cu2+ doping improves the energy storage capacity of the cathode material.

Heterostructured SnSe-MnSe@rGO as a composite electrode for Li-ion batteries and high energy density asymmetric supercapacitors

Systematically fabricated hybrid nanomaterials have good outer walls and inherent features, which can significantly improve energy storage capabilities. Herein, we demonstrated the successful preparation of heterostructure SnSe-MnSe nanomaterials anchored reduced Graphene oxide using the hydrothermal method. The SnSe-MnSe@rGO is used as the composite electrode for lithium-ion battery and supercapacitor applications. The SnSe, MnSe, and SnSe-MnSe materials were also prepared and compared their performances with the SnSe-MnSe@rGO material. The first cycle charge/discharge capacity of SnSe-MnSe@rGO was 484.6/641.9 mAhg−1 at 0.1Ag−1 with coulombic efficiency of 75.49 %. After 1000 cycles at 1Ag−1, the SnSe-MnSe@rGO delivered the discharge capacity of 175.7 mAhg−1 at 1Ag−1 with 72.75 % retention of capacity. For supercapacitor application, the SnSe-MnSe@rGO exhibits the battery-type energy storage mechanism and provides a specific capacity of 210. 8 mAhg−1 at 1 Ag−1 with superior rate capability and it withstands 94 % of initial capacity after 5000 GCD cycles at 20 Ag−1 in three-electrode electrochemical cells. The asymmetric type such as activated carbon//SnSe-MnSe@rGO device delivers the capacity of 105.8 mAhg−1 and shows a high energy density of 84.7 Whkg−1 with the power density of 810.5 Wkg−1 at 1 Ag−1. The device holds 89 % of its initial capacity retention after 10,000 continuous GCD cycles at 10 Ag−1. This study emphasizes a comprehensive and fundamental understanding of the reaction mechanisms at the heterostructures, as well as the strategic design of composite materials for constructing advanced electrodes in the realm of sustainable energy storage applications.

In situ confined growth of Cu2-xSe nanoparticles in highly defective nitrogen-doped carbon for high-rate sodium-ion battery anodes

Transition metal selenides are considered as hopeful anode materials for sodium-ion battery (SIB) due to the high specific capacity and rich reserves in nature. However, the inherent low conductivity of these anode materials, as well as the inevitable volume expansion and structural collapse during cycling, result in their poor rate performance and cycling stability. Herein, a universal selenization-co-carbonization strategy is proposed to synthesize Cu2-xSe nanoparticles in-situ confined in highly defective nitrogen-doped carbon (Cu2-xSe@NC) with superior architectural features, which involves simultaneous selenization and carbonization procedure of octahedral metal–organic framework (Cu-BTC) precursor. The nitrogen-doped carbon matrix stabilizes/confines the Cu2-xSe nanoparticles to prevent their agglomeration and volume expansion during cycling while endowing high electrical conductivity to the hybrid materials. As anode for SIBs, the Cu2-xSe@NC exhibits a high reversible capacity of 340 mAh/g at 0.1 A/g with a high initial coulombic efficiency of 70 %, superior rate performance (capacity retention of 82.4 % from 0.02 to 5 A/g), and long-cycle durability. The ex-situ XRD and HRTEM techniques confirmed that Cu2-xSe undergoes complex intercalation and crystal evolution accompanied by reversible intermediate phases (NaCuSe and Na2Se) transformation during charge/discharge cycle. First-principles calculations and in-situ EIS confirmed that the intercalation of Na+ can greatly reducing the energy band gap and improving the electrical conductivity of Cu2-xSe@NC, thereby achieving excellent rate performance. Moreover, the Cu2-xSe@NC anode is also evaluated by matching with Na3V2(PO4)3 cathode to assemble a full SIB, which can provide high initial capacity and capacity retention, revealing its potential for practical application.

The hydrothermal synthesis of d-Ti3CN/V2O5 hollow spheres for enhanced supercapacitors applications

In this work, d-Ti3CN MXene was obtained by selective etching of Al from Ti3AlCN by hydrofluoric acid, and a hydrothermal method was employed to prepare d-Ti3CN/V2O5 hollow spheres. The prepared d-Ti3CN/V2O5 hollow spheres showed enhanced electrochemical properties. V2O5 hollow spheres expanded the distance between d-Ti3CN MXene sheets, leading to fast electron transport and improved electrochemical performance of d-Ti3CN/V2O5 hollow spheres. A specific capacitance of 340 F g−1 was achieved at 1 A g−1 current density, which is higher than that of d-Ti3CN MXene (321 F g−1) and V2O5 hollow sphere (155 F g−1). The initial capacitance retention is 89 % after 6000 cycles of constant current charge and discharge at the current density of 10 A g−1. In short, d-Ti3CN/V2O5 hollow spheres show excellent supercapacitor performance regarding specific capacitance and stability.

Decorating N-doped carbon-coated cobalt phosphide nanoparticles onto N-doped carbon nanotubes for high-performance supercapacitors and efficient methanol electro-oxidation

Cobalt phosphide (CoP) has become a promising electrode material for supercapacitors and methanol electro-oxidation due to its high electrical conductivity and and multiple oxidation states. However, the insufficient electroactive sites and large volume changes restrict its electrochemical performance. Herein, a novel CoP/carbon nanocomposite electrode material is designed and synthesized by decorating N-doped carbon (NC) coated CoP nanoparticles onto N-doped carbon nanotubes (N-CNTs). N-CNTs serve as support to grow CoP nanoparticles, which effectively reduces the sizes and aggregation of CoP nanoparticles and provides more electroactive sites. Density function theory calculation results confirm that the coating of NC on CoP nanoparticles increases the electrical conductivity of CoP by transferring electrons from NC to CoP. Meanwhile, a built-in electrical field is formed at the CoP/NC interface, resulting in higher electron/ion transfer efficiency as well as easier surface OH– adsorption. Moreover, the flexible NC shell and N-CNTs supports together effectively withstand the mechanical stress and buffer volume changes of CoP during the charge/discharge processes. Therefore, the obtained N-CNTs@CoP@NC nanocomposite electrode demonstrates high specific capacities (1003 and 621C g−1 at 1 and 10 A g−1, respectively) and good cycling performance (91.2 % retention of initial capacity after 10,000 cycles at 5 A g−1). Furthermore, it also shows a current density of up to 281 mA cm−2at a scan rate of 10 mV s−1with 92.4 % retention of initial current density in 1 M KOH with 0.5 M methanol. These results highlight a feasible strategy for improving practical capacities and cyclic stability of CoP-based electrode materials by integrating nanostructured CoP with one/two-dimensional carbon materials.

Improving the stability of ceramic-type lithium tantalum phosphate (LiTa2PO8) solid electrolytes in all-solid-state batteries

Solid-state battery (SSB) systems are among the most promising next-generation batteries for electronics and electric vehicles because of their high volumetric energy density, safety, nonflammability, and chemical stability, compared to lithium-ion batteries using conventional liquid electrolytes. However, SSBs have several limitations, including the reactivity of the electrode materials. Herein, we address these issues by synthesizing lithium tantalum phosphate (LTPO) solid-electrolyte disks through a cold sintering process and assembling them with a lithium manganese iron phosphate (LMFP) electrode into an all-solid-state battery. The SSB fabricated with LTPO/LMFP exhibited a high initial discharge capacity (~130 mAh/g) and capacity retention (70 % after 100 cycles) at room temperature (RT). The LTPO with an amorphous lithium-based composite in the grain boundaries has high ionic conductivity and stability at the interface of the LMFP electrodes. In addition, the LMFP cathodes with an adhesive layer infiltrating the pores of the electrode significantly improved the cyclic performance of the SSB system with an initial capacity of 125 mAh/g and capacity retention of approximately 98 % after 100 cycles at RT. The analysis and future experimental results proved that this novel material and approach can improve the electrochemical performance of rechargeable SSBs and contribute to the development of high-performance energy storage devices for various applications.

Polyacrylonitrile-sodium lignosulfonate -derived nitrogen-doped three-dimensional hierarchical porous carbon for supercapacitors

Modulation of pore structure and heteroatom doping are very important strategies to improve the electrochemical properties of carbon electrode materials. This report investigates the use of biomass-derived nitrogen-doped porous carbon materials to address the challenge of the specific capacitance and energy density in supercapacitors. Nitrogen-doped three-dimensional hierarchical porous carbon materials were prepared using a polyacrylonitrile/sodium lignosulfonate composite monolith as a precursor by thermally induced phase separation and subsequent carbonization/activation. This method precisely controls the structure and surface properties of porous carbon materials by regulating the structure of the precursor and situ doping of nitrogen, which is a valuable strategy for the controllable regulation of the pore structure for nitrogen-doped porous carbon materials. The resulting carbon material displayed excellent capacitance performance, exhibiting a high specific capacitance of 325.7F g -1 at a current density of 0.5 A/g, maintaining initial capacitance retention of 90.1 % at a current density of 5 A/g after 10,000 cycles. When investigated for practical applications, the assembled supercapacitor device had a higher energy density (9.88 W h kg- 1), which is higher than commercial carbon-based supercapacitors.

High-energy-density zinc ion capacitors based on 3D porous free-standing defect-reduced graphene oxide hydrogel cathodes.

Zinc ion capacitors (ZICs) have shown potential for breaking the energy density ceiling of traditional supercapacitors (SCs) via appropriate device design. Nevertheless, a significant challenge remains in advancing ZIC positive electrode materials with excellent conductivity, high specific capacitance, and reliable cycle stability. A highly attractive option for carbon-based electrode materials is reduced graphene oxide (RGO) due to its vast specific surface area, prominent porosity, and 3D cross-linked frame. However, the tight stacking of RGO sheets driven by van der Waals forces can restrict active sites, decrease specific capacitance, and elevate electrochemical impedance. To overcome these challenges, 3D defective RGO (DRGO) hydrogels were prepared by a metal Co cocatalytic gasification reaction. This method produced mesoporous defects on the surface of RGO hydrogels via a low-temperature hydrothermal self-assembly strategy. The surface of the layer has a wide and uniform distribution, which can offer abundant redox active sites, rich ion transfer channels, and fast reaction kinetics. In this work, 3D DRGO//Zn exhibited a wide operating window (0-1.8 V), high specific capacitance (189.39 F g-1 at 1 A g-1), outstanding energy density (85.23 W h kg-1 at 960.31 W kg-1; 52.36 W h kg-1 at 17454.87 W kg-1), and persistent cycling life (98.86% initial capacitance retention after 10 000 cycles at 10 A g-1). This study emphasizes the device design of ZIC and promising prospects of using 3D DRGO hydrogel as a feasible positive electrode for ZIC.

A Dual-Approach for Extending the Lifespan of Cobalt-Free Na[Ni0.55Mn0.35Fe0.1]O2 cathode Via Bi5+-Doping and Bi2O3 Coating in Sodium-Ion Batteries

A cobalt-free layered Na[Ni0.55Mn0.35Fe0.1]O2(NFM) cathode material has been synthesized and dual surface and structural modifications have been performed. Bi5+ is doped into pure NFM in order to tune the structure, whereas, a thin layer of Bi2O3 is coated on surface of the Bi5+-coated NFM to modify the surface. The structure, morphology, and electrochemical performance of prepared samples are analyzed and compared by various characterization techniques. The pristine NFM cathode exhibits the specific discharge capacity of 170 mAh g-1, while Bi-doped cathode exhibits 181 mAh g-1, and Bi2O3 coated cathode renders 180 mAh g-1. It is observed that, pristine NFM cathode suffers rapid capacity degradation and nearly ~80% capacity loss within first 250 cycles. After 1000 cycles, BNFM shows 47% capacity retention, while, BNMF@Bi2O3 shows 73% capacity retention of initial capacity. This improvement in the rate capability is obtained due to the effect of Bi-doping and Bi2O3 coating, where, former enlarges interlayer spacing and latter provides the ionic conducting channel as well as protects the particle from the contact of the electrolyte. The combined effect of Bi-doping and Bi2O3 coating facilitates fast diffusion of Na-ions within the transition metal layers resulting in superior rate capability. Fig: Cyclability of pristine, Bi-doped and Bi2O3 coated NFM cathode materials Figure 1

Polythiophene Coating-encapsulated CoNi2S4@HCS for quasi-solid-state hybrid supercapacitors with gel electrolyte containing gelatin

Supercapacitors play a crucial role in energy storage applications due to their high energy and power densities. In this context, synthesizing composites such as: poly(3,4propylenedioxythiophene)/CoNi2S4@hollow carbon sphere (PProDOT/CoNi2S4@HCS) through solid-state thermal polymerization and hydrothermal ion exchange has gained significant attention. The PProDOT/CoNi2S4@HCS composite exhibits exceptional electrochemical performance, including a high specific capacitance of 1054 C g−1 and an initial capacity retention rate of 83.3% at 20 A g−1. This signifies that the composite can effectively store and deliver electrical energy. The composite possesses a three-dimensional core-shell structure, wherein HCS acts as a carbon-based substrate that prevents the aggregation of CoNi2S4 nanoparticles. Simultaneously, the PProDOT film ensures the structural integrity of CoNi2S4 and facilitates efficient electron/ion transfer within the composite. Furthermore, researchers have assembled a quasi-solid-state supercapacitor using the PProDOT/CoNi2S4@HCS composite and a gel electrolyte composed of polyvinyl alcohol/sulfonated cellulose/gelatin (PVA/sCMC/GEL/KOH). This supercapacitor demonstrates outstanding characteristics, such as a high energy density of 85.3 Wh kg−1, a high power density of 7957 W kg−1, and a capacity retention rate of 87.56% after 15,000 cycles at 4 A g−1. These results indicate that the composite-based supercapacitor can provide long-term stability and reliable performance under demanding operating conditions.

Synthesis of FeOOH/Zn(OH)2/CoS Ferromagnetic Nanocomposites and the Enhanced Mechanism of Magnetic Field for Their Electrochemical Performances.

The FeOOH/Zn(OH)2/CoS (FZC) nanocomposites are synthesized and show the outstanding electrochemical properties in both supercapacitor and catalytic hydrogen production. The specific area capacitance reaches 17.04 Fcm-2, which is more than ten times higher than that of FeOOH/Zn(OH)2 (FZ) substrate: 1.58 Fcm-2). FZC nanocomposites also exhibit the excellent cycling stability with an initial capacity retention rate of 93.6% after 10000 long-term cycles. The electrolytic cell (FZC//FZC) assembled with FZC as both anode and cathode in the UOR (urea oxidation reaction)|| HER (hydrogen evolution reaction) coupled system requires a cell voltage of only 1.453V to drive a current density of 10mAcm-2. Especially, the electrochemical performances of FZC nanocomposites are enhanced in magnetic field, and the mechanism is proposed based on Stern double layer model at electrode-electrolyte interface (EEI). More electrolyte ions reach the surface of FZC electrode material under Kelvin force, moreover, the warburg impedance of FZC nanocomposites decrease under magnetic field action, which results in the enhanced behaviors for both the energy storage and urea oxidation reaction .

A twofold approach for prolonging the lifespan of cobalt-free Na[Ni0.55Mn0.35Fe0.1]O2 cathode via Bi5+-doping and Bi2O3 coating in sodium ion batteries

A cobalt-free biphasic (P2/O3) layered Na[Ni0.55Mn0.35Fe0.1]O2 (NFM) cathode material has been synthesized and dual surface and structural modifications have been performed. Bi5+ is doped into pure NFM in order to tune the P2/O3 phase, whereas, a thin layer of Bi2O3 is coated on surface of the Bi5+-doped NFM (BNFM) for surface modification. The structure, morphology, and electrochemical performance of prepared samples are analyzed and compared by various characterization techniques. The pristine NFM cathode exhibits the specific discharge capacity of 170 mAh g−1, while Bi-doped cathode exhibits 181 mAh g−1, and Bi2O3 coated cathode renders 180 mAh g−1. It is observed that, pristine NFM cathode suffers rapid capacity degradation and nearly ~80 % capacity loss within first 250 cycles. After 1000 cycles, BNFM shows 47 % capacity retention, while, Bi2O3 coated BNFM (BNMF@Bi2O3) shows 73 % capacity retention of initial capacity. This improvement in the rate capability is obtained due to the effect of Bi-doping and Bi2O3 coating, where, former enlarges interlayer spacing and latter provides the ionic conducting channel as well as protects the particle from the contact of the electrolyte. The combined effect of Bi-doping and Bi2O3 coating facilitates fast diffusion of Na-ions within the transition metal layers resulting in superior rate capability.

Facile preparation of Ni@C/hierarchically porous carbon nanocomposites with excellent electrochemical performance from Ni-MOF/porous polymers

High performance supercapacitors are significant for the practical application of the novel renewable energies. Comparisons suggest that hybrid supercapacitor (HSC) is a fairly promising type for application since it combines high power density and high energy density. In this study, hierarchically porous carbons (HPCs) supported Ni@C nanoparticles (Ni@C/HPCs) were obtained by pyrolyzing the precursors of Ni-based MOF/porous polymers (Ni-MOF/polyHIPEs) which were prepared by high internal phase emulsion (HIPE) polymerization followed with solvothermal Ni-MOF growing. The composition and morphology of the Ni@C/HPCs can be controlled by changing the growth time of Ni-MOF. The optimized sample Ni@C/HPC-15 demonstrates a high specific capacity of 215.0 C g−1 at 1 A g−1 and a high rate performance of 82.3% when the current density increases from 1 A g−1 to 10 A g−1. Furthermore, Ni@C/HPC//HPC HSC was assembled and achieved an energy density of 40.9 Wh kg−1 at a power density of 747.2 W kg−1. In particular, the assembled HSC exhibited a remarkable initial capacitance retention of 86.3% after 5000 cycles at 6 A g−1. The reported convenient method may provide inspiration in the preparation and optimization of HPC-based electrode materials with satisfactory performances for energy storage.

Sonochemical synthesis of battery-type ZnCo2O4 electrode material with huge specific surface area for advanced hybrid supercapacitors

Sonochemistry is a novel and efficient method for the synthesis of electrode materials within micro-/nano-scale. In this work, the ZnCo2O4 nanoparticles (NPs) and chain-like ZnCo2O4 nanostructures, namely ZnCo2O4–7.5 and ZnCo2O4–9.5, were sonochemically prepared by controlling the pH value of reaction system combined with an extra calcination. The ZnCo2O4–7.5 NPs exhibited a larger specific surface area (SSA) of 148.77 m2 g−1, and presented better electrochemical properties such as a high specific capacity (Cs) of 331.2C g−1 under 2 A g−1 along with 82.5 % rate performance at 10 A g−1. As for the ZnCo2O4–9.5 nanostructure, it delivered an inferior Cs of 274.8C g−1 and showed a moderate rate capability with 75.6 % capacity retention, accordingly. The hybrid supercapacitor (HSC) device was assembled using such ZnCo2O4–7.5 NPs (ZnCo2O4–9.5 nanostructure) as cathode and activated carbon (AC) as anode to explore the application potential in the field of electrochemical energy storage. After 7000 cycles at the current density of 8 A g−1, both ZnCo2O4–7.5//AC and ZnCo2O4–9.5//AC HSCs showed outstanding cyclic stabilities with 100.4 % and 105.1 % of initial capacity retention, respectively. Meanwhile, the ZnCo2O4–7.5//AC HSC delivered a high energy density (Ed) of 38.1 W h kg−1 at the power density (Pd) of 1002.0 W kg−1, and it could still hold 26.3 W h kg−1 at the higher Pd of 9136.5 W kg−1. In contrast, the ZnCo2O4–9.5//AC HSC presented a slightly inferior Ed of 36.8 W h kg−1 at 1104.7 W kg−1. The both types of ZnCo2O4–7.5 and ZnCo2O4–9.5 electrode materials demonstrate excellent electrochemical property, and they can be expected to show brilliant application potential in the field of electrochemical energy storage & conversion when served as electrode materials for high-performance hybrid supercapacitors.

Unveiling the impact of reaction temperature on hydrothermally synthesized nickel phosphate hydrate for supercapacitors

Transition metal phosphates have engrossed a hefty amount of interest in the field of energy storage owing to their fascinating characteristics. Herein, this study reports nickel phosphate hydrate (NP) deposited on nickel foam using a facile hydrothermal method. The X-ray diffraction (XRD) technique confirms the formation of NP on the nickel foam having a monoclinic structure and an “I2/m” space group. The scanning electron microscopy (SEM) studies revealed a stacked micro-sheet-like structure. The electrochemical measurements were examined under a potential window of −0.2 to 0.55 V Vs SCE in a 1 M KOH electrolyte delivering a maximum areal capacitance of 6333.33 mF cm−2 at a current density of 10 mA cm−2. The synthesized electrodes’ charge storage kinetics were diffusion-driven. Moreover, the electrode produced an energy density of 316.67 µWh cm−2 along with an impressive cyclic retention of ∼89 % over 1000 charge–discharge cycles. A hybrid supercapacitor device was fabricated with N5//AC as the electrodes shows 94.44 % of its initial capacitance retention after 5000 cycles.