Battery-type Materials Research Articles

Fabrication of super-high energy density asymmetric supercapacitor prototype device employing NiCo2S4@f-MWCNT nanocomposite

Materials with high porosity, high redox activity and rich electrochemically active sites are promising candidates for pseudocapacitance. Among the bimetallic sulphides of transition metals, nickel cobalt sulphide (NiCo2S4; NCS) is a promising pseudocapacitive material. NiCo2S4 (NCS) can be coupled with carbonaceous material such as functionalised multiwalled carbon nanotubes (NCS@f-MWCNT) to further enhance the electrochemical characteristics such as high charge-storage capacity, improved charge-discharge characteristics, stability and rate performance. In this line, bare NiCo2S4 (NCS) and functionalized multiwalled carbon nanotubes (f-MWCNT) loaded NiCo2S4 nanoparticles were synthesized by hydrothermal method by employing hexadecyltrimethylammonium bromide (CTAB) as surfactant. X-ray diffraction studies confirmed the formation of cubic phase of NiCo2S4 and transmission electron microscopic study revealed the formation of NCS@f-MWCNT nanocomposite. The XPS findings confirmed the co-existence of Ni3+, Ni2+, Co3+, and Co2+ species in both the NCS and NCS@f-MWCNT samples. Cyclic voltammetry analysis was performed to determine the respective impacts of the surface adsorption and diffusion-mediated processes on the charging/discharging kinetics. The incorporation of f-MWCNT into NCS led to improved overall charge storage kinetics, demonstrating a promising avenue for developing low-cost cathode materials for high-performance hybrid battery-type materials with both high power and energy densities. Bare NiCo2S4 showed a specific capacitance of ~899 Fg−1 at 1 Ag−1 with a capacitance retention of ~52 %. While NCS@f-MWCNT exhibited a high charge storage capacity of ~1360 Fg−1 with capacitance retention of 89 % at 10 Ag−1. An asymmetric coin cell devices were fabricated using NCS@f-MWCNT as a positive electrode and an activated carbon, reduced graphene oxide ((ASC2) or carbon fiber (ASC3) as negative electrodes. Among them, the NCS@f-MWCNT//AC (say ASC1) showed outstanding charge storage characteristics with a capacitance of ~109.9 Fg−1, energy density ~ 78.3 Whk g−1 and power density ~ 800 Wk g−1 at 1Ag−1. The presented analysis has demonstrated that a hybrid structure made of highly conductive materials like functionalized multiwall carbon nanotubes could be employed to synergistically enhance the electrochemical performance of NiCo2S4.

Electrosynthesis of Co[sbnd]Mn layered-double-hydroxide as a precursor for Co-Mn-MOFs and subsequent electrochemical sulfurization for supercapacitor application

Today, researchers are focusing on improving the electrochemical efficiency of supercapacitors by designing and evolving synthesis routes for battery-type hierarchical materials. This study proposes a green method for creating high-efficiency positive electrode materials with a mesoporous heterostructure on Ni foam (NF) using a metal-organic framework (MOF)-derived approach. A binder-free electrosynthesis technique was utilized to grow CoMn-layered double hydroxide (CoMn-LDH) and exchange ions to obtain a porous metal precursor, namely binary Co-Mn-MOF. The MOF arrays were then electrochemically converted to CoMn-sulfide (CMS), which exhibits excellent conductivity and a mesoporous structure, enabling it to serve as a 3D continuous network for ion and electron conduction in energy storage. The synthesized sample was characterized using various techniques, including field-emission scanning electron microscopy (FESEM), elemental mapping, high-resolution transmission electron microscopy (HR-TEM), energy-dispersive X-ray analysis (EDX), Brunauer-Emmett-Teller (BET) surface area analysis, X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD). Among the prepared electrode samples, CoMn−S with an Mn/Co feeding ratio of 1:2 demonstrated outstanding electrochemical properties. Based on this platform, CMS was applied and validated as a positive electrode in supercapacitors, exhibiting a high specific capacity of 1091C g−1 at 1 A g−1 in a three-electrode configuration and remarkable cycling life (85 % capacitance retention over 7000 cycles at 25 A g−1). Furthermore, an assembled asymmetric supercapacitor (ASC) device using CMS as the cathode and AC as the anode demonstrated satisfactory electrochemical performance. The CMS//AC device delivers an energy density of 84 Wh kg−1 at a high power density of 1191.4 W kg−1 and maintains stable electrochemical stabilities (92 % capacitance retention even after 7000 cycles). This synthesis approach opens up a new avenue for developing binder-free electrodes with hierarchical structures using metal sulfides, thereby enhancing the electrochemical performance of hybrid supercapacitors.

Porous prussian blue analogs derived nickel-iron bimetallic phosphide nanocubes on conductive hollow mesoporous carbon nanospheres for stable and flexible high-performance supercapacitor electrode

Nickel-iron bimetallic phosphide (Ni-Fe-P) is the ideal battery-type materials for supercapacitor in virtue of high theoretical specific capacitance. Nevertheless, its actual adhibition is astricted on account of inferior rate capability and cyclic stability. Herein, we constructed hierarchical core–shell nanocomposites with hollow mesoporous carbon nanospheres (HMCS) packaged via prussian blue analogs derived Ni-Fe-P nanocubes (Ni-Fe-P@HMCS), as a positive electrode for hybrid supercapacitor (HSC). Profiting from the cooperative effects of Ni-Fe-P nanocubes with small size and good dispersibility, and HMCS with continuously conductive network, the Ni-Fe-P@HMCS composite electrode with abundantly porous architectures presents an ultrahigh gravimetric specific capacity for 739.8 C g−1 under 1 A g−1. Specially, the Ni-Fe-P@HMCS electrode presents outstanding rate capability of 78.4% (1 A g−1 to 20 A g−1) and cyclic constancy for 105% after 5000 cycles. Density functional theory implies that the composite electrode possesses higher electrical conductivity than bare Ni-Fe-P electrode by reason of the incremental charge density, and the electrons transferring from NiFe3P4 to HMCS layers. Additionally, the assembled Ni-Fe-P@HMCS//HMCS HSC facility delivers the high energy density for 64.1 Wh kg−1, remarkable flexibility and mechanical stability. Thus, this work proffers a viable and efficacious measure to construct ultra-stability electrode for high-performance portable electronic facilities.

Active sites-induced decoration of nickel hydroxide nanosheets on copper oxide nanocubes as electroactive material of battery supercapacitor hybrids

Battery supercapacitor hybrids (BSH) comprising battery and supercapacitor-type electrodes can attain high energy/power densities and long cycle life. Copper oxide is regarded as a promising battery-type active material, due to low-cost, high chemical stability and good electrochemical properties. However, poor electrical conductivity and insufficient active sites should be improved to attain high energy storage ability. In this work, a novel battery-type material composed of Ni(OH)2 nanosheets decorated on Cu2O cages is synthesized via a facile solution process for the first time. Less deposition of Ni(OH)2 leads to sparse distribution on Cu2O cages, and full coverage of Ni(OH)2 is achieved via depositing four Ni(OH)2 layers on Cu2O cages. The largest specific capacitance (CF) of 389.1 F/g is achieved at 20 mV/s for the optimized Ni(OH)2 and Cu2O (Ni(OH)2@Cu2O) composite, while the Cu2O electrode shows a smaller CF value of 79.7 F/g. Coating Ni(OH)2 on Cu2O can induce active site formation and enhance electrical conductivity. The Ni(OH)2@Cu2O positive electrode and the active carbon negative electrode are used to assemble a BSH, which presents a maximum energy density of 4.09 Wh/kg at 500 W/kg and excellent cycling ability with CF retention of 70% and Coulombic efficiency higher than 97% after 10,000 charge/discharge cycles.

High electrochemical performance of cobalt ions-doped Ni3Se4 boosted by its highly conductive hierarchical framework

Battery-type materials have the intrinsic feature of poor electrical conductivity, significantly affecting their electrochemical performance. At the same time, the low cycling stability of these materials is a key factor weakening the feasibility of their application in supercapacitors (SCs). Although various strategies based on nanoengineering are adopted to address these two issues, it seems that the progress so far does not prove the significant effectiveness of these strategies. In this work, a battery-type material, cobalt ions-doped Ni3Se4, is synthesized using a hydrothermal selenization procedure to address the two issues mentioned above. We preliminarily demonstrate that the electrochemical activity and cycling stability of battery-type materials depend on their intrinsically high conductivity, given that these materials have the proper structure and composition. Based on high electrical conductivity, the cobalt ions-doped Ni3Se4 exhibits high capacitive performance and remarkable cycling stability due to the synergistic effect between Ni and Co and the porous nanosheets self-supported structure. The result of this work proves that the cobalt ions-doped Ni3Se4 with the highly conductive hierarchical framework is a promising electrode material for SCs.

Reconfiguration of the electronic structure of metal phosphide for ultrahigh energy density hybrid supercapacitors

Nanostructured mixed transition metal phosphides are promising battery-type materials for supercapacitor applications due to their advantageous morphology and electronic properties. In the present study, we constructed a porous NiFeP/MoO2@Co3O4 core–shell heterostructure grown on nickel foam using a hydrothermal route, phosphorization treatment and atomic layer deposition. The resulting NiFeP/MoO2@Co3O4 cuboids were characterized by a lower charge transfer resistance, rich electroactive sites and shorter ion diffusion paths for redox reactions. It is discovered that the excellent supercapacitive performance of NiFeP/MoO2@Co3O4 cuboids was obtained not only because of the rich active sites via the formation of multiple components but also due to the strong electronic interaction between Co and Ni/Fe/Mo species. Benefiting from the rich active sites of NiFeP, the designed NiFeP/MoO2@Co3O4 exhibited a specific capacity of 1531.1 C g−1 and a high durability, with a retention rate of 90.8% after 20,000 cycles, outperforming previously reported metal-phosphide-based materials. A hybrid device was also constructed with a NiFeP/MoO2@Co3O4 cathode and a graphene anode, delivering a maximum energy density of 71.3 W h kg−1 at a power density of 2100.3 W kg−1 with exceptional capacity retention after 10,000 cycles. These results suggest that the proposed novel strategy has great potential for the improvement of smart nanostructures for advanced supercapacitors.

Ni-Co PBA-decorated CNTs as battery-type cathode materials for potassium-ion hybrid capacitors

Ni-Co PBA-decorated CNTs as battery-type cathode materials for potassium-ion hybrid capacitors

Electronic Structure Engineered Heteroatom Doped All Transition Metal Sulfide Carbon Confined Heterostructure for Extrinsic Pseudocapacitor.

Ultra-high energy density battery-type materials are promising candidates for supercapacitors (SCs); however, slow ion kinetics and significant volume expansion remain major barriers to their practical applications. To address these issues, hierarchical lattice distorted α-/γ-MnS@Cox Sy core-shell heterostructure constrained in the sulphur (S), nitrogen (N) co-doped carbon (C) metal-organic frameworks (MOFs) derived nanosheets (α-/γ-MnS@Cox Sy @N, SC) have been developed. The coordination bonding among Cox Sy , and α-/γ-MnS nanoparticles at the interfaces and the π-π stacking interactions developed across α-/γ-MnS@Cox Sy and N, SC restrict volume expansion during cycling. Furthermore, the porous lattice distorted heteroatom-enriched nanosheets contain a sufficient number of active sites to allow for efficient electron transportation. Density functional theory (DFT) confirms the significant change in electronic states caused by heteroatom doping and the formation of core-shell structures, which provide more accessible species with excellent interlayer and interparticle conductivity, resulting in increased electrical conductivity. . The α-/γ-MnS@Cox Sy @N, SC electrode exhibits an excellent specific capacity of 277 mA hg-1 and cycling stability over 23600 cycles. A quasi-solid-state flexible extrinsic pseudocapacitor (QFEPs) assembled using layer-by-layer deposited multi-walled carbon nanotube/Ti3 C2 TX nanocomposite negative electrode. QFEPs deliver specific energy of 64.8 Wh kg-1 (1.62 mWh cm-3 ) at a power of 933 W kg-1 and 92% capacitance retention over 5000 cycles.

Tailing copper cobalt sulfide particle-decorated tube-like structure as efficient active material of battery supercapacitor hybrid

Copper cobalt sulfide (CuCo2S4) has received intensive attentions as one of effective battery-type materials of battery supercapacitor hybrids (BSH), because of numerous redox states and large conductivity. Morphology has been widely reported to play important roles on energy storage ability. Tube-like structure is beneficial for providing large surface area at inner/outer surface, and efficient charge transfer paths in one-dimensional directions. In this study, the CuCo2S4 particle-decorated tube-like structure is firstly designed on nickel foam via the hydrothermal process at different temperatures. The effects on morphology, composition and electrochemical performance are examined. The CuCo2S4 synthesized at 160 °C shows the most uniform rod size and regularly distributed particles on surface. The highest specific capacitance (CF) of 831.7 F/g corresponding to the capacity of 115.6 mAh/g is achieved for the optimal CuCo2S4 electrode, due to the largest electrochemical surface area with multiple active sites. A BSH is fabricated by using the CuCo2S4 positive electrode and the activated carbon negative electrode. A wide potential window of 1.5 V and the maximum energy density of 32.1 Wh/kg at power density of 1.1 kW/kg are achieved. The CF retention of 78.8% and Coulombic efficiency of 95.5% are also attained after 10,000 charge/discharge cycles for the BSH.

Novel synthesis of polyaniline, manganese oxide and nickel sulfide lavandula-like composites as efficient active material of supercapacitor

Transition metal sulfides (TMS) are considered as the efficient battery-type material due to high theoretical capacity, redox reversibility, and electrical conductivities. The Ni3S2 with a high theoretical capacity and abundant sources is one of the efficient energy storage materials, but high contact resistances and poor cyclic stability of Ni3S2 restrict its electrochemical performance. The binder-free design, morphology regulation, composite development, and conductive polymer incorporation are useful strategies for solving the problems of Ni3S2. In this study, a novel lavandula-like manganese oxide, Ni3S2 and polyaniline composite (PANI/MnOx/Ni3S2) is synthesized on Ni foam as the binder-free battery-type electrode of battery supercapacitor hybrid (BSH) as clean energy sources at the first time. The Mn amounts and aniline electropolymerization durations play important roles on active sites and electrical conductivity. The functions of MnOx and PANI are analyzed by comparing physical and electrochemical properties of Ni3S2, MnOx/Ni3S2, PANI, PANI/Ni3S2 and PANI/MnOx/Ni3S2 electrodes. The largest specific capacitance (CF) of 9.5 F/cm2 at 30 mA/cm2 is achieved for the optimized PANI/MnOx/Ni3S2 electrode. A BSH assembled using activated carbon and PANI/MnOx/Ni3S2 electrodes presents the maximum energy density of 2.31 Wh/m2 at 65 W/m2, and the CF retention of 78.5 % and Coulombic efficiency of 95.8 % after 10,000 times repeatedly charging and discharging process.

Facile synthesis of copper cobalt sulfide and nickel hydroxide tube-like composites as battery-type active material of energy storage devices

Bimetallic sulfide has attracted much attentions as efficient electroactive materials of battery supercapacitor hybrid (BSH), because of numerous redox states, high conductivity and good energy efficiency. Developing composites having excellent chemical and electrochemical properties is necessary to enhance the energy storage features of bimetallic sulfides. In this study, CuCo2S4 and Ni(OH)2 composites (CuCo2S4@Ni(OH)2) are designed on Ni foam via the facial hydrothermal process and chemical bath deposition as the electroactive material of BSH at first time. Effects of Ni(OH)2 amounts on CuCo2S4 on electrochemical and physical properties of CuCo2S4@Ni(OH)2 are investigated. The physical mixed CuCo2S4 and Ni(OH)2 composite is also fabricated to verify synergistic effects of CuCo2S4@Ni(OH)2. A higher specific capacitance (CF) of 1583.9 F/g along with the capacity of 220.0 mAh/g are got for optimal CuCo2S4@Ni(OH)2 electrode, respectively comparing to 831.7 and 1063.3 F/g of CuCoS4 and Ni(OH)2 electrodes. A BSH is fabricated by the CuCo2S4@Ni(OH)2 electrode and the activated carbon electrode. The potential window of 1.6 V and maximum energy density of 32.1 Wh/kg at 1.1 kW/kg are achieved. The CF retention of 78% and Coulombic efficiency higher than 97% in 8000 charge/discharge cycles are also obtained for this BSH.

A high performance all-polymer symmetric faradaic deionization cell

Faradaic deionization (FDI) is an emerging and promising electrochemical technology for stable and efficient water desalination. Battery-type energy storage materials applied in FDI have demonstrated to achieve higher salt removal capacities than carbon-based conventional capacitive deionization (CDI) systems. However, most of the reported FDI systems are based on inorganic intercalation compounds that lack cost, safety and sustainability benefits, thereby curtailing the development of a feasible FDI cell. In this work, we introduce an all-polymer rocking chair practical FDI cell, with a symmetric system composed by a redox-active naphthalene-polyimide (named as PNDIE) buckypaper organic electrodes. First, electrochemical performance of PNDIE in 0.05 M NaCl under open-air conditions is evaluated in both three-electrode half- and symmetric FDI full-cell using typical lab-scale electrode dimensions (1.6 mgPNDIE; 0.78 cm2), revealing promising specific capacity (115 mAh g−1) and excellent cycle stability for full-cell experiments (77 % capacity retention over 1000 cycles). Then, all-polymer rocking chair FDI flow cell was constructed with practical PNDIE electrodes (92.2 mgPNDIE; 9.6 cm2) that delivered large desalination capacity (155.4 mg g−1 at 0.01 A g−1) and high salt-removal rate and productivity (3.42 mg g−1 min−1 at 0.04 A g−1 and 62 L h−1 m−2, respectively). In addition, long-term stability (23 days) experiments revealed salt adsorption capacity (SAC) retention values over 95% after 100 cycles. The overall electrochemical and deionization performances of the reported technology is far superior than the state-of-the-art CDI and FDI techniques, making it a competitive choice for robust and sustainable “water-energy” electrochemical applications.

Battery-Type-Behavior-Retention Ni(OH)2-rGO Composite for an Ultrahigh-Specific-Capacity Asymmetric Electrochemical Capacitor Electrode.

Nanosized battery-type materials applied in electrochemical capacitors can effectively reduce a series of problems caused by low conductivity and large volume changes. However, this approach will lead to the charging and discharging process being dominated by capacitive behavior, resulting in a serious decline in the specific capacity of the material. By controlling the material particles to an appropriate size and a suitable number of nanosheet layers, the battery-type behavior can be retained to maintain a large capacity. Here, Ni(OH)2, which is a typical battery-type material, is grown on the surface of reduced graphene oxide to prepare a composite electrode. By controlling the dosage of the nickel source, the composite material with an appropriate Ni(OH)2 nanosheet size and a suitable number of layers was prepared. The high-capacity electrode material was obtained by retaining the battery-type behavior. The prepared electrode had a specific capacity of 397.22 mA h g-1 at 2 A g-1. After the current density was increased to 20 A g-1, the retention rate was as high as 84%. The prepared asymmetric electrochemical capacitor had an energy density of 30.91 W h kg-1 at a power density of 1319.86 W kg-1 and the retention rate could reach 79% after 20,000 cycles. We advocate an optimization strategy that retains the battery-type behavior of electrode materials by increasing the size of nanosheets and the number of layers, which can significantly improve the energy density while combining the advantage of the high rate capability of the electrochemical capacitor.

Rapid, external acid-free synthesis of Bi2WO6 nanocomposite for efficient supercapacitor application

BackgroundIt is crucial to create improved energy storage technologies, such as supercapacitors to reduce the erratic nature of natural energy sources, which heavily rely on the production of electroactive materials with optimal electrochemical properties. A symmetric supercapacitor may achieve a wide voltage window and prevent electrolyte breakdown by taking advantage of both battery-type and capacitor-type materials. This overcomes the energy limits of conventional supercapacitors. Recently, tungsten oxide-based materials have attracted attention as a family of attractive electrode materials for pseudocapacitors due to their greater electronic conductivity, eco-friendliness, strong electrochemical durability, variable oxidation state, and affordability. MethodsIn this work, we have synthesized Bi2WO6 nanocomposite by a single-step redox reaction under hydrothermal conditions without using of any external acidic medium. Significant findingsThe synthesized Bi2WO6 nanocomposite exhibits the highest specific capacitance of 363 F/g in neutral electrolyte. Moreover, the fabricated symmetric supercapacitor device of synthesized Bi2WO6 nanocomposite shows a maximum energy density of 26.18 Wh/kg and a power density of 5.4 kW/kg. The fabricated symmetric supercapacitor device exhibits excellent durability. The device demonstrates 89% specific capacitance retention after 5000 continuous charge-discharge cycles.

Nonporous, conducting bimetallic coordination polymers with an advantageous electronic structure for boosted faradaic capacitance.

Conductive coordination polymers (c-CPs) are promising electrode materials for supercapacitors (SCs) owing to their excellent conductivity, designable structures and dense redox sites. However, despite their high intrinsic density and outstanding electrical properties, nonporous c-CPs have largely been overlooked in SCs because of their low specific surface areas and deficient ion-diffusion channels. Herein, we demonstrate that the nonporous c-CPs Ag5BHT (BHT = benzenehexathiolate) and CuAg4BHT are both battery-type capacitor materials with high specific capacitances and a large potential window. Notably, nonporous CuAg4BHT with bimetallic bis(dithiolene) units exhibits superior specific capacitance (372 F g-1 at 0.5 A g-1) and better rate capability than isostructural Ag5BHT. Structural and electrochemical studies showed that the enhanced charge transfer between different metal sites is responsible for its outstanding capacitive performance. Additionally, the assembled CuAg4BHT//AC SC device displays a favorable energy density of 17.1 W h kg-1 at a power density of 446.1 W kg-1 and an excellent cycling stability (90% capacitance retention after 5000 cycles). This work demonstrates the potential applications of such nonporous redox-active c-CPs in SCs and highlights the roles of bimetallic redox sites in capacitive performance, which hold promise for the future development of c-CP-based energy storage technologies.

Synergistic effect of NaTi2(PO4)3 and MXene synthesized in situ for high-performance sodium-ion capacitors

The rapid growth of industries that use electrical energy requires novel energy storage systems that are low-cost, reliable, and have improved capacity and power. Sodium-ion capacitors (SICs) have attracted considerable attention as next-generation energy storage systems because they comprise sodium, which is a relatively inexpensive resource, and have high energy and power. Battery-type materials for SICs need to be studied due to their poor rate performance and lifespan. This study reports a NaTi2(PO4)3/MXene (NTP/MXene) composite as a battery-type anode material for high-performance SICs. The NTP/MXene composite is synthesized via the in situ growth of NTP, with poor electrical conductivity, on the surface of MXene, with a two-dimensional structure and high electrical conductivity. The in situ synthesized NTP/MXene composite exhibits better rate performance and cyclic stability than NTP or MXene. These improved electrochemical properties are attributed to the synergistic effect of the pseudocapacitive characteristics of MXene and the battery characteristics of NTP. An SIC assembled with the NTP/MXene composite and activated carbon affords a high energy density of 112.1 Wh kg−1 and a high power density of 9.5 kW kg−1. Furthermore, it exhibits excellent long-term capacity retention of 78 % even after 10,000 cycles.

High Electrochemical Performance of a Nanostructured Electrode Material Based on a Cobalt-Manganese Layered Double Hydroxide

In this work, alpha-cobalt hydroxide (Co(OH)2) and cobalt/manganese layered double hydroxide (CoMn-75-LDH) were synthesized using the Tower method. The alpha phase was confirmed for Co(OH)2 through XRD analysis. Furthermore, the TEM images showed that the materials are formed by nanoparticles with an average size of ~5 nm. Cyclic voltammetry and galvanostatic charge/discharge measurements were carried out and the CoMn-75-LDH presented a superior electrochemical behavior to Co(OH)2. The presence of Mn2+/3+ ions in the crystal structure of CoMn-75-LDH, verified by XPS analysis, enhanced the electrical conductivity of the material, providing more electroactive sites, as a result, the electrochemical performance of the material was improved. Electrochemical studies showed that CoMn-75-LDH has a specific capacitance of 677 F g-1 at current density of 0.5 A g-1 compared to Co(OH)2, whose specific capacitance value was 268.7 F g-1 at the same current density. In addition, the electrochemical signature of Co(OH)2 revealed that the electrode material exhibits an extrinsic pseudocapacitive behavior instead of the typical behavior of battery-type materials due to its nanostructured morphology. Also, electrochemical studies showed that the charge storage mechanism for CoMn-75-LDH is controlled by both the capacitive and diffusion process.

Development of high-performance supercapacitor based on Fe3O4@SiO2@PolyFc nanoparticles via surface-initiated radical polymerization

The magnetic core-shell Fe3O4@SiO2 nanoparticles were prepared via the Stöber route and functionalized with triethoxyvinylsilane as coupling agent to introduce reactive vinyl groups onto the surface of Fe3O4@SiO2 nanoparticles, afterwards, 3-(4-ferrocenylbutoxy)-1-propene as a redox active monomer was grafted onto the surface of modified-MNPs through a surface-initiated radical polymerization. The chemical structure, surface morphology, crystalline structure and elemental composition of the synthesized nanoparticles were evaluated and investigated using FT-IR, FE-SEM, EDX, XRD, and BET techniques. The supercapacitor performance of the synthesized electrode materials was investigated using various electrochemical experiments such as CV, GCD and EIS. The modified final nanoparticles showed an excellent charge storage capacity of 170 mAh g−1 (612 C g−1) at 2.5 A g−1. The surface modified Fe3O4 with grafting of the Fc moiety as a Faradaic battery-type redox active material ensured a high specific capacity of the final modified nanoparticles.

Reconfiguring the Electronic Structure of Heteroatom Doped Carbon Supported Bimetallic Oxide@Metal Sulfide Core-Shell Heterostructure via In Situ Nb Incorporation toward Extrinsic Pseudocapacitor.

High-energy-density battery-type materials have sparked considerable interest as supercapacitors electrode; however, their sluggish charge kinetics limits utilization of redox-active sites, resulting in poor electrochemical performance. Here, the unique core-shell architecture of metal organic framework derived N-S codoped carbon@Cox Sy micropetals decorated with Nb-incorporated cobalt molybdate nanosheets (Nb-CMO4 @Cx Sy NC) is demonstrated. Coordination bonding across interfaces and π-π stacking interactions between CMO4 @Cx Sy and N and, S-C can prevent volume expansion during cycling. Density functional theory analysis reveals that the excellent interlayer and the interparticle conductivity imparted by Nb doping in heteroatoms synergistically alter the electronic states and offer more accessible species, leading to increased electrical conductivity with lower band gaps. Consequently, the optimized electrode has a high specific capacity of 276.3mAh g-1 at 1Ag-1 and retains 98.7% of its capacity after 10 000 charge-discharge cycles. A flexible quasi-solid-state SC with a layer-by-layer deposited reduced graphene oxide /Ti3 C2 TX anode achieves a specific energy of 75.5Wh kg-1 (volumetric energy of 1.58 mWh cm-3 ) at a specific power of 1.875kWh kg-1 with 96.2% capacity retention over 10 000 charge-discharge cycles.

Advanced hybrid supercapacitors assembled with high-performance porous MnCo2O4.5 nanosheets as battery-type cathode materials

Porous MnCo2O4.5 nanosheets (NSs) were fabricated through a sequence of synthetic procedures containing initial solvothermal reactions, precursor aging in water, hydrothermal treatment, and final annealing conversion in air. These ultrathin NSs possessed a huge specific surface area of 104.93 m2 g−1 along with an average pore size of 14.15 nm. Electrochemical performance of the NSs was assessed in three-electrode & two-electrode systems. It was confirmed that the MnCo2O4.5 NSs delivered a specific capacity of 304.37 C g−1 at 1 A g−1 and 225.60 C g−1 at 10 A g−1 in 2 M of KOH electrolyte. To evaluate the practical application in electrochemical energy storage, a hybrid supercapacitor (HSC) was assembled with MnCo2O4.5 NSs as cathode and activated carbon (AC) as anode. The MnCo2O4.5 NSs//AC HSC exhibited a high energy density of 33.36 W h kg−1 at the power density of 950.83 W kg−1, and showed an outstanding cyclic durability with 100.04 % capacity retention over 5000 cycles at 6 A g−1. The current synthetic strategy provides a good pathway for the preparation of other transition metal oxides (TMOs)-based electrode materials with large surface area and superior electrochemical property for the further assembly of advanced HSC devices.