All-solid-state Asymmetric Supercapacitor Research Articles

Solvothermal growth of silver-doped vanadium pentoxide microurchins as a cathode material for all-solid-state asymmetric supercapacitors

This study aims to improve the electrochemical properties of vanadium pentoxide by inserting silver cations into the vanadium oxide lattice. The porous silver-doped V2O5 (Ag-V2O5) microurchins were grown via a facile one-step solvothermal process. The enhanced mesoporosity and interlayer d-spacing upon silver-doping, as confirmed by Brunauer–Emmett–Teller (BET) and X-ray diffraction analyses, played an important role in facilitating the intercalation/de-intercalation of electrolyte ions and thus enhancing the capacitive performance of V2O5. The Ag-V2O5 electrode delivered a superior capacitance of 535.6 F/g at 0.5 A/g and a higher rate capacity of 78.8% in non-aqueous lithium perchlorate electrolyte compared to sodium perchlorate electrolyte. Furthermore, the specific capacitance of V2O5 was remarkably increased by ∼56% upon 5.33 at% Ag-doping. An all-solid-state asymmetric supercapacitor (ASC) was fabricated using Ag-V2O5 as the cathode, activated carbon cloth as the anode, and LiClO4-loaded poly(acrylonitrile-co-1-vinylimidazole-co-itaconic acid) as a solid electrolyte. The ASC was stably operating in a wide potential window of 0–1.6 V and delivered a high energy of 53.8 Wh kg−1. Most importantly, the ASC exhibits a slow self-discharge rate with only 7.7% voltage loss after 17 h when charged at 1.6 V. Hence, these impressive electrochemical performances of Ag-V2O5 make it a promising cathode material for next-generation supercapacitors.

Mn-doped NiCoFeO4 based hierarchical Ni foam as binder-free electrode for all-solid-state asymmetric supercapacitor

Herein, we demonstrate a facile hydrothermal method to directly grow Mn-doped NiCoFeO4 flower like hierarchical nanostructures on Ni-foam. The hierarchical morphology was confirmed by electron microscopic analysis and whereas formation of the ternary oxide was verified by X-ray diffraction analysis. Energy dispersive X-ray analysis confirmed the elemental composition. The Mn-doped NiCoFeO4 on Ni foam significantly outperformed the undoped NiCoFeO4 on Ni foam when tested as electrode material by three terminal electrochemical analysis as it exhibited specific capacitance of 500 mF/cm2 at a current density of 5 mA/cm2 which is five times that exhibited by the undoped NiCoFeO4 (99 mF/cm2) along with 83 % capacity retention after 7500 cycles at a high current density of 25 mA/cm2 highlighting the strong influence of Mn doping. Further, an all-solid state asymmetric supercapacitor (ASC) was fabricated using the hierarchical Mn-doped NiCoFeO4 on Ni-foam as anode and commercial activated carbon as cathode which exhibited power density of 2 mW/cm2 at energy density of 60 μWh/cm2 and was able to power a light emitting diode (LED) for 3 min. Thus, the novel Mn-doped hierarchical NiCoFeO4 on Ni-foam developed in this work shows great potential as a low-cost high-performance binder-free electrode for an all-solid-state asymmetric supercapacitor.

Synthesis of 2D bi-metallic Zn/Cu metal-organic framework integrated graphene nanocomposites for all-solid-state asymmetric supercapacitors

In this work, a novel two-dimensional (2D) bi-metallic metal-organic frameworks (MOFs) consisting of zinc and copper metal centers with 1,3,5-tricarboxylic acid as a chief and efficient organic linker (Zn/Cu-BTC) and its composite with exfoliated graphene nanosheets (EGNSs) have been investigated for supercapacitor applications. The composites were synthesized via facile in-situ solvothermal process. Different spectroscopic, microscopic, and surface analyses confirmed the successful formation of porous electroactive composites, where 2D MOF nanosheets were vertically grown on the EGNS surfaces. In the two-electrode symmetric system, the as-synthesized Zn/Cu-BTC MOF@EGNS electrode achieved an enhanced specific gravimetric capacitance and equivalent volumetric capacitance of 1284.9 F/g and 813.3 F/cm3 at 0.5 A/g. It exhibits high-rate performance and prolonged cycling stability with >90 % retention after 8000 cycles. All-solid-state asymmetric supercapacitor (ASC) device was constructed with Zn/Cu-BTC MOF@EGNS composite and EGNS electrodes, where PVA-KOH membrane served as a separator-cum-electrolyte. The ASC device delivered a satisfactory energy density of 60.55 Wh kg−1 and a maximum power density of 10 kW kg−1 with an admirable cycling stability of 92 % after 10,000 charge-discharge cycles. In the future, this work can encourage manufacturing innovation.

Surface‐Modified ZnCo2O4 Nanoparticles as Binder‐Free Electrode for All Solid‐State Asymmetric Supercapacitor

AbstractChoice of electrode material is crucial to the development of high‐performance supercapacitors. Since surface properties are key to the performance of an electrode material for supercapacitors, surface chemical treatment of electrode materials is an interesting topic of research. ZnCo2O4 (ZCO) is a low‐cost binary transition metal oxide with high theoretical conductivity and charge storage capacity making it a good choice for supercapacitor electrode. Herein, we present a systematic investigation of the influence of four different surface modifier (3 surfactants, 1 mineralizer) on ZCO electrode directly grown on Ni foam to compare the relative influence on the performance of the modified ZCO electrode. Analyses of the modified ZCO electrodes revealed the formation of cubic spinel phase of ZCO with average particle size of ~30 nm. The sodium dodecyl sulfate (ZCO−S) modified electrode (ZCO−S) exhibited the best electrochemical performance with specific capacitance of 1988 F/g at 1 A/g and 87 % capacity retention after 7000 cycles at 10 A/g. Further, an all‐solid‐state asymmetric supercapacitor (ASC) was fabricated with ZCO−S on Ni foam and carbon nanotube combination which exhibited specific capacitance of 102 F/g at 1 A/g corresponding to power density of ~1599 W‐kg−1 establishing ZCO−S as a very good electrode material for supercapacitor.

Hierarchical Lotus-Seedpod-Derived Porous Activated Carbon Encapsulated with NiCo2S4 for a High-Performance All-Solid-State Asymmetric Supercapacitor

Converting biowaste into carbon-based supercapacitor materials provides a new solution for high-performance and environmentally friendly energy storage applications. Herein, the hierarchical PAC/NiCo2S4 composite structure was fabricated through the combination of activation and sulfuration treatments. The PAC/NiCo2S4 electrode garnered advantages from its hierarchical structure and hollow architecture, resulting in a notable specific capacitance (1217.2 F g−1 at 1.25 A g−1) and superior cycling stability. Moreover, a novel all-solid-state asymmetric supercapacitor (ASC) was successfully constructed, utilizing PAC/NiCo2S4 as the cathode and PAC as the anode. The resultant device exhibited exceptionally high energy (49.7 Wh kg−1) and power density (4785.5 W kg−1), indicating the potential of this biomass-derived, hierarchical PAC/NiCo2S4 composite structure for employment in high-performance supercapacitors.

Ni3S2@NiCo-LDH cross-linked nanosheet arrays on Ni foam for high-performance all-solid-state asymmetric supercapacitors

Nickel-Cobalt layered double hydroxide (NiCo-LDH) nanosheets have the advantages of large interlayer spacing, adjustable structure, and high theoretical capacity, which has attracted extensive attention. However, the poor conductivity and structural instability limit their application in electrode materials. Herein, a high-performance all-solid-state asymmetric supercapacitor (ASC) is designed with AC as the anode and Ni3S2@NiCo-LDH as the cathode. The open Ni3S2@NiCo-LDH cross-linked nanosheets arrays are uniformly arranged on the Ni foam (NF), which not only increases the sufficient contact area between electrode and electrolyte, but also facilitates the rapid transfer of electrons. Therefore, the assembled ASC exhibits high area-specific capacitance of 1267.2 mF cm−2 at 5 mA cm−2, high energy density of 450.60 μW h cm−2 at the power density of 3.99 mW cm−2, and excellent cyclic stability with 85.2 % capacity retention over 5000 cycles. This work demonstrates the feasibility of the cross-linked nanosheets arrays of Ni3S2@NiCo-LDH on NF, which shows great potential as electrode for novel energy storage devices.

NiO@MXene Nanocomposite as an Anode with Enhanced Energy Density for Asymmetric Supercapacitors

MXene composites with different metal oxides have recently demonstrated good electrochemical performance with enhanced conductivity and also hinder the restacking of MXene. With this motivation, we synthesized the nickel oxide@MXene (NO@MXene) series with varying compositions, which was screen-printed on a flexible stainless-steel mesh (FSSM) substrate as an anode for a supercapacitor. The effect of sample composition, i.e., 5% NO@MX, 10% NO@MX, 15% NO@MX, and 20% NO@MX, on the electrochemical properties is studied systematically. The 15% NO@MX composite electrode demonstrated a maximum capacitance of 1542 F g–1@6 mA cm–2 current density in 1 M KOH. An all-solid-state asymmetric supercapacitor (ASC) with 15% NO@MX (anode) and copper oxide (cathode) displayed a 1 V potential window. The device exhibited a specific capacitance of 73.3 F g–1@10 mA cm–2 current density with a maximum energy density of 10.7 Wh kg–1 and a power density of 3333 W kg–1 in polymer gel of PVA–KOH electrolyte. The cyclic stability of the device demonstrates 90.6% capacitance retention over 5000 cycles. It is envisaged that 15% NO@MX as an anode would serve as a promising electrode for the all-solid-state device for supercapacitor applications.

The fabrication of Co3S4/NF@NiCo-LDH nanocomposites for integrated all-solid-state asymmetric supercapacitors

In the study, Co3S4/[email protected] nanocomposites were successfully synthesized on nickel foam (NF) by a simple and cost-effective hydrothermal method. The supercapacitors with Co3S4/[email protected] as electrode materials exhibited an ultra-high specific capacitance of 3480.0 F g-1 at a current density of 1 A g-1. Co3S4/[email protected]//activated carbon (AC) all-solid-state asymmetric supercapacitor (ASS) was assembled with PVA/KOH as the electrolyte. The ASS device exhibits excellent cycling stability of 77.97% capacitance retention after 5000 cycles at 10 A g-1. The maxmum energy density of Co3S4/[email protected]//AC ASS was 275.2 Wh kg-1, with the power density of 5760 W kg-1. Especially, the ASS devices connected in different manners presented the typical performances of integrated circuits: voltage enhancement for series devices and current enhancement for parallel devices. Therefore, the study presented great practical potentials for new energy storage devices in integrated circuits.

3D emerging nanosheets comprising hierarchical CoMoO4/MnO2 composites for flexible all-solid-state asymmetric supercapacitors

Flexible and portable energy storage gadgets have aroused mounting interest because of the remarkable achievement in the field of intelligent and wearable devices. In this paper, perpendicularly organized CoMoO4/MnO2 (CMO/MO) heterostructures are produced in situ on the surface of Ni foam, and the porous 3D architectures and rough nanoplates outside could offer substantial active sites and decrease the ion diffusion distances. Such splendid architecture with massive electrochemically active sites exhibits greater areal capacity in contrast to CoMoO4. Subsequently, an all-solid-state asymmetric supercapacitor (ASSC) based on the CMO/MO and PVA/KOH gel electrolyte is prepared. The ASSC could work under high voltages ranging from 0 to 1.4 V and deliver a maximum areal capacitance of 0.467 Fcm−2 (1 mAcm−2). It also exhibits a great energy density of 35.81 Wh kg−1 at a watt density of 198.22 W kg−1, and the capacity retention could keep 75% even after 8000 cycles. Collectively, this research offers enlightenment regarding the synthesis of electrode materials.

A novel hierarchical core-shell structure of NiCo2O4@NiCo-LDH nanoarrays for higher-performance flexible all-solid-state supercapacitor electrode materials

In the present work a 3D hierarchical NiCo 2 O 4 @NiCo-LDH core-shell structure has been fabricated on activated carbon cloth through a facile hydrothermal strategy and an electrodeposition step. The core of the NiCo 2 O 4 nanowires forms the nanoarray backbone on carbon cloth while the shell of NiCo-LDH nanosheets extends the electrochemical active sites and generates mesoporous hierarchical channels to facilitate electron and ion transport. Therefore, with the optimized mass ratio of 1.9 between NiCo-LDH and NiCo 2 O 4 , such a core-shell structure enhanced the areal capacitance of the as-prepared NiCo 2 O 4 @NiCo-LDH electrode up to 6092 mF/cm 2 (or areal capacity of 0.846 mAh/cm 2 at 2 mA/cm 2 for the battery type pseudocapacitor) and obtain high specific capacitance of 1882 F/g under 1 A/cm 2 . The capacity retention rate can maintain 83.9 % after 5000 cycles at 30 mA/cm 2 . Furthermore, an all-solid-state asymmetric supercapacitor (ASC) was assembled using NiCo 2 O 4 @NiCo-LDH//activated carbon. Such an ASC exhibits a very high energy density of 49 Wh/kg at the power density of 750 W/kg and retains 30 Wh/kg at 7500 W/kg. The ASC shows its excellent cycling stability by keeping 83.3 % of initial capacity retention rate after 2000 cycles under 5 A/g. The assembled flexible all-solid-state supercapacitor with NiCo 2 O 4 @NiCo-LDH//activated carbon exhibits good mechanical stability and high specific capacity of 157 F/g under 1 A/g. The significantly improved electrochemical properties demonstrates the practical applications of the core-shell structure of NiCo 2 O 4 @NiCo-LDH on carbon cloth for novel ASC configuration design and development of next energy storage devices. • The unique NiCo 2 O 4 @NiCo-LDH cover-shell heterostructure greatly improve the electrochemical performance. • The NiCo 2 O 4 @NiCo-LDH//ACC electrode shows the high area capacitance of 6092 mF/cm 2 . • The NiCo 2 O 4 @NiCo-LDH//AC ASC device has good flexibility, high energy density and power density.

In situ generation of CeCoSx bimetallic sulfide derived from “egg-box” seaweed biomass on S/N co-doped graphene aerogels for flexible all solid-state supercapacitors

Practical applications of flexible electrochemical energy storage devices are still limited by the lack of robust mechanical structures and high capacitive storage capabilities. Herein, the 3D CeCoSx-SA/GF porous aerogels are designed and prepared based on sodium alginate, which possess a special structure that can be explained by the so-called “egg-box” model. Each metal ion can be paired with the carboxyl and hydroxyl groups of the G monomer on two adjacent sodium alginate molecular chains. Melamine foam is used as carrier for graphene/sodium alginate impregnation and plays an important role on significantly limiting the agglomeration of graphene nanosheets due to their strong π-π stacking. The fabricated electrode based on CeCoSx-SA/GF shows an excellent electrochemical capacitance of 873.3F/g at the current density of 1A/g. In addition, the capacitance retention rate can still remain 87.1 % after 5000 cycles at a high current density of 8 A/g. Moreover, the fabricated all-solid state asymmetric supercapacitor device assembled with CoCeSx-SA/GF and active carbon shows an energy density of 29.58 Wh kg−1 at a power density of 801 W kg−1. For practical applications, the fabricated supercapacitor device can power a multifunctional display for 28 mins and illuminate a small light bulb for 3 mins. Moreover, the KOH/polyvinyl alcohol gel-electrolyte was used to fabricate high-strength and flexible CeCoSx-SA/GF/PVA/KOH composite film electrode, which can be bent at various angles (0°-180°) and can be twisted into various shapes. Notably, the CeCoSx-SA/GF/PVA/KOH composite film can lift plastic bottles containing 500 mL (500 g) and 1000 mL (1 kg) water, respectively, indicating that it has great application potential for wearable and portable electronic devices.

Boosting the Electrochemical Performance of Mn-doped CuCo2O4/CuO Heterostructures for All-Solid-State Asymmetric Battery-type Supercapacitors

The introduction of Manganese (Mn) ions (2+ ⇋ 3+ ⇋ 4+) to transition metal oxides proved to be a potential strategy to tailor the redox behavior of these materials for energy storage. We fabricate a lower electronegative element (i.e., Mn) doped copper cobaltite and copper oxide (CuCo2O4/CuO; CCO) heterostructures electrodes through the hydrothermal synthesis route. The ensued electrodes have a more than 2-fold improvement in specific capacity (382.9 C g−1) than the undoped CCO electrode (120.8 C g−1) at 1 A g−1. The all-solid-state asymmetric supercapacitor (ASC) practical device is constructed with higher Mn-doped CCO heterostructures as the positive electrode and activated carbon (AC) as the negative electrode. With a voltage window of 1.5 V, the fabricated ASC device has a high specific energy of 52.6 Wh kg−1 and specific power of 774.3 W kg−1. The long-term cyclic stability of 92% capacity retention after 5000 cycles at the current density of 4 A g−1. Additionally, two ASC devices are series-connected that can power up a red light-emitting diode (LED) display for more than 150 s, demonstrating the device’s efficient power delivery.

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

Ternary layered double-hydroxide-based active compounds are regarded as ideal electrode materials for supercapacitors because of their unique structural characteristics and excellent electrochemical properties. Herein, an NiCeCo-layered double hydroxide with a core-shell structure grown on copper bromide nanowire arrays (CuBr2@NCC-LDH/CF) has been synthesized through a hydrothermal strategy and calcination process and utilized to fabricate a binder-free electrode. Due to the unique top-tangled structure and the complex assembly of different active components, the prepared hierarchical CuBr2@NCC-LDH/CF binder-free electrode exhibits an outstanding electrochemical performance, including a remarkable areal capacitance of 5460 mF cm-2 at 2 mA cm-2 and a capacitance retention of 88% at 50 mA cm-2 as well as a low internal resistance of 0.163 Ω. Moreover, an all-solid-state asymmetric supercapacitor (ASC) installed with CuBr2@NCC-LDH/CF and activated carbon electrodes shows a high energy density of 118 Wh kg-1 at a power density of 1013 W kg-1. Three assembled ASCs connected in series can operate a multifunctional display for over three and a half hours. Therefore, this innovative work provides new inspiration for the preparation of electrode materials for supercapacitors.

Fabrication of semi‐flexible carbon quantum dots‐reinforced polypyrrole ( PPy / CQDs ) composite electrodes by hybrid electrospray deposition for high‐performance energy storage device

A carbon quantum dots-reinforced polypyrrole (PPy/CQDs) composite electrodes were prepared via the hybrid electrospray method. PPy/CQDs composite shows superior electrochemical performance with a specific capacity (Qg) of 174.21 C g−1 at 1 A g−1 in 3 M KOH aqueous electrolyte. An all-solid-state asymmetric supercapacitor (ASC) is composed of PPy/CQDs as a positive electrode and rGO as a negative electrode with PVA/KOH gel electrolyte, which exhibited the specific capacity (Qg) of 79.25 C g−1 at the current density of 1.5 A g−1 with an energy and power density of 26.44 Wh kg−1 and 18 090.82 W kg−1, respectively. An assembled PPy/CQDs//rGO device offers cyclic retention of about 76.8% at 15 A g−1 after 10 000 cycles. The above results confirmed that the as-prepared PPy/CQDs composite electrode is more suitable for high-performance-based semi-flexible supercapacitor application.

Facile strategy for preparing the composite of MoS2 microspheres and N/S dual-doped graphene stabilized by graphene quantum dots for all-solid-state asymmetric supercapacitor

The composite (GQDs-MoS2/NSG) of molybdenum disulfide (MoS2) and N/S dual-doped graphene (NSG) has been successfully synthesized through in situ self-assembly by a new hydrothermal strategy using graphene quantum dots (GQDs) as auxiliary agent. The effect of GQDs dosage on the morphology of MoS2 has been investigated. Results show that adding GQDs to the nanohybrids can significantly improve the dispersion uniformity and binding state of MoS2 and NSG, and increase the overall defect density. When the GQDs dosage is 20 mg, the sample GQDs-MoS2/NSG20 has the best performance, and its specific capacitance reaches 564.3 .Fg−1 at a scan rate of 10 .mV s−1. Under a large current density of 20 .A g−1, the specific capacitance retention rate of GQDs-MoS2/NSG20 is 92.8% after 10,000 constant current charge/discharge loops. The contribution of the pseudocapacitance of GQDs-MoS2/NSG20 at 10–200 mV.s−1 was studied by using dynamic analysis and density functional theory calculation. All-solid-state asymmetric supercapacitor (ASC) was fabricated with NSG and GQDs-MoS2/NSG20. When the power density is 900 W.kg−1, the energy density reaches 68.8 Wh.kg−1. At a current density of 20 A.g−1, the specific capacitance retention rate is 92.2% after 10000 constant current charge/discharge loops.

Hierarchical MnCo2O4@CuCo2O4 core-shell nanoarrays on carbon cloth as binder-free electrode for flexible all-solid-state asymmetry supercapacitors

Hierarchical core-shell nanowire arrays with a shell of CuCo2O4 nanosheets and a core of MnCo2O4 nanowires directly coated on the conductive carbon cloth (CC) are rationally designed and synthesized via a facile hydrothermal route with a post low-temperature thermal treatment in air. The binder-free MnCo2O4@CuCo2O4/CC composite material exhibits an enhanced performance (1241.0 C g−1 at 1 A g−1) compared with the MnCo2O4/CC (832.7 C g−1 at 1 A g−1) and CuCo2O4/CC (734.1 C g−1 at 1 A g−1). In addition, the MnCo2O4@CuCo2O4/CC electrode is assembled into a flexible all-solid-state asymmetric supercapacitor (ASC), which delivers a maximum specific energy of 62.0 Wh kg−1 at a specific power of 747.2 W kg−1 with 91.2% capacity retention after 10000 charge–discharge cycles at 8 A g−1. And the ASC device also exhibits 91.7% capacity retention at floating time over 200 h at 8 A g−1. Further, the MnCo2O4@CuCo2O4//AC device shows superior flexible performance while bending at various angles. These results make this MnCo2O4@CuCo2O4 core/shell composite to be a good candidate for flexible all-solid-state electrochemical capacitors applications.

Sodium 5-sulfosalicylate-assisted hydrothermal synthesis of a self-supported Co3S4−Ni3S2@nickel foam electrode for all-solid-state asymmetric supercapacitors

Rational design and construction of self-supporting electrodes with high energy exporting densities promise a future of wearable and portable devices. Herein, we demonstrate that, for the first time, a one-pot hydrothermal method for the in-site growth of Co3S4 −Ni3S2 on nickel foam (NF) with the assistance of a chelating agent sodium 5-sulfosalicylate (SSS) (labeled as CS4−Ni3S2@F-SSS) for high-performance supercapacitors. Served directly as a self-supporting supercapacitor electrode, CS4−Ni3S2@F-SSS owns a specific capacitance of up to 2825.5 mF cm−2 at a corresponding 2 mA cm−2 current density and a commendable rate capability of 82% conducted within a current density domain of 2 − 40 mA cm−2 accompanied by good cyclability. More strikingly, the assembled tow-electrode (CS4−Ni3S2@F-SSS vs. active carbon (AC)@NF) all-solid-state asymmetric supercapacitor (ASC) is capable of reaching an energy density of 40.9 Wh kg−1 at a high power density of 1566.4 W kg−1 with excellent durability (92.8% retention after 2000 charge−discharge cycles at 8 mA cm−2), which are amongst the top of analogous ASCs in peer reports. Additionally, the possible factors that are accountable for the extraordinary supercapacitive performance of CS4−Ni3S2@F-SSS are discussed and analyzed.

Core-shell structured ZIF-7@ZIF-67 with high electrochemical performance for all-solid-state asymmetric supercapacitor

Zeolitic imidazolate frameworks (ZIFs) are considered as a promising material for energy storage in recent years. Here, core-shell structured ZIF-7@ZIF-67 is synthesized in this work. The core-shell structured material can promote electron transfer of inner-outer metals ions of ZIF-7@ZIF-67, quicken diffusion of electrolyte ions and improve the capacitance performance compared to the ZIF-7 and ZIF-67. ZIF-7@ZIF-67 delivers good energy storage ability with a specific capacitance of 518.9 F g−1 at a current density of 1 A g−1 and remarkable stability with a retention of 99.6% after 4000 cycles in the three-electrode system. Furthermore, an all-solid-state asymmetric supercapacitor (ASC) device is assembled based on core-shell structured ZIF-7@ZIF-67 as positive electrode. Impressively, the ASC device displays an energy density of 31 Wh kg−1 at a power density of 400 W kg−1 and an excellent cyclic stability with 99.5% retention after 10,000 cycles at a current density of 10 A g−1. Finally, two all-solid-state ASCs are contacted to power various lighting-emitting diodes (LED). The red LED can be kept glowing for over 10 min. These electrochemical characteristics suggest that core-shell structured ZIF-7@ZIF-67 is a potential material for energy storage device with long-life cyclic stability.

MgCo2O4@NiMn layered double hydroxide core-shell nanocomposites on nickel foam as superior electrode for all-solid-state asymmetric supercapacitors

In this work, MgCo2O4@NiMn layered double hydroxide (LDH) core-shell structured nanocomposites on Ni foam (NF) are synthesized by facile hydrothermal and calcination methods. MgCo2O4/NF is synthesized first via a hydrothermal reaction and annealing treatment, and then utilized to prepare MgCo2O4@NiMn-LDH/NF core-shell structured nanocomposites via the second hydrothermal process. It is found that the MgCo2O4@NiMn-LDH/NF nanocomposite prepared from 6 h hydrothermal reaction (MC@NM-LDH-2) exhibits an excellent specific capacitance of 3757.2 F g−1 (at 1 A g−1). Moreover, a high capacitance retention (86.9% after 6000 cycles) and a low internal resistance (Rs) (0.565 Ω) can be achieved. Furthermore, an all-solid-state asymmetric supercapacitor (ASC) is assembled using MgCo2O4@NiMn-LDH/NF-2 as positive electrode and activated carbon (AC) as negative electrode. The as-fabricated MgCo2O4@NiMn-LDH/NF-2//AC ASC shows a high energy density of 62.33 Wh kg−1 at 750 W kg−1. Meanwhile, the MgCo2O4@NiMn-LDH/NF-2//AC ASC device possesses an outstanding cycling stability of 93.7% retention of the initial capacitance after 6000 cycles and three ASC devices connected in series can light up a LED bulb for 15 min. Our results manifest that these core-shell structure MgCo2O4@NiMn-LDH nanocomposites could envision huge potential application in energy storage devices.

Facile construction of MgCo2O4@CoFe layered double hydroxide core-shell nanocomposites on nickel foam for high-performance asymmetric supercapacitors

In this work, hierarchical MgCo2O4@CoFe layered double hydroxide (LDH) core-shell nanowire arrays on Ni foam (NF) are synthesized by facile hydrothermal and calcination methods. MgCo2O4/NF has been first synthesized via a hydrothermal reaction and annealing treatment and then utilized to prepare MgCo2O4@CoFe-LDH/NF core-shell nanocomposites via the second hydrothermal reaction. It is found that the MgCo2O4@CoFe-LDH/NF core-shell nanocomposite prepared from 3 h hydrothermal reaction (MC@CF-LDH-3) exhibits an excellent specific capacitance of 903.15 C g−1 (2007 F g−1) at the current density of 1 A g−1. Moreover, a high capacitance retention (80.2% maintained after 5000 cycles) and a low internal resistance (Rs) (0.75 Ω) can be acquired. Furthermore, an all-solid-state asymmetric supercapacitor (ASC) is assembled using MgCo2O4@CoFe-LDH/NF-3 as the positive electrode and activated carbon (AC) as the negative electrode. The as-fabricated MgCo2O4@CoFe-LDH/NF-3//AC ASC shows a high energy density of 60.82 Wh kg−1 at 725 W kg−1. Meanwhile, the MgCo2O4@CoFe-LDH/NF-3//AC ASC device possesses an excellent cycling stability of 93.6% retention of the initial capacitance after 5000 cycles and two ASC devices connected in series can light up a LED bulb for 8 min. Our results manifest that this hierarchical MgCo2O4@CoFe-LDH composite has huge potential application in energy storage devices.