High-performance Hybrid Supercapacitors Research Articles

Graphene-wrapped (Ni,Co)Se2 carbon nanowires toward high performance hybrid supercapacitors

To probe the next generation of flexible supercapacitors for practical application, small size, excellent electrical conductivity, low cost, Eco-friendly and excellent capacitance are prerequisites. However, due to dissatisfied electrical conductivity, limited surface area and low porosity, which results in few active sites and long ion transport channels, electrochemical improvements are needed for bimetallic selenide-based flexible supercapacitors. Hence, novel three dimensional graphene (3DG) encapsulated cobalt-nickel selenide carbon nanowires [3DG/(Co,Ni)Se2 CNWs] composite aerogels was successfully fabricated through a modified self-templating approach. The assembled 3DG/(Co,Ni)Se2 CNWs electrode showcases outstanding electrochemical performance, achieving a high specific capacitance of 1286 F g−1 at 1 A g−1 attributed to its combination structure of carbon based materials and nanowires. It demonstrates excellent cycling stability, with a capacity retention of 88 % after 3000 cycles at 2 A g−1. The prepared 3DG/(Co,Ni)Se2 CNWs//active carbon (AC) asymmetric flexible all-solid-state supercapacitors demonstrates outstanding electrochemical properties, achieving an energy density of up to 28 Wh kg−1 at a power density of 800 W kg−1. Even after 6000 cycles at 5 A g−1, it retains 84.15 % of its specific capacitance, thus presenting a new direction for energy storage applications.

Designing high-performance hybrid supercapacitors and electrochemical sensors with carbon nanotube-embedded silver manganese sulfide@AC@NF composites

Recently, there has been a lot of interest in hybrid supercapacitors due to their amazing capacity to store energy, surpassing the energy storage capability of both conventional supercapacitors and batteries. In this work, physical integration of silver manganese sulphide (AgMnS) into carbon nanotubes was achieved using hydrothermal synthesis. A comprehensive evaluation was conducted on the material's electrical characteristics. With this composite functioning as the positive electrode and activated carbon (AC) acting as the negative, an asymmetric device configuration was used. The AgMnS@CNT composite demonstrated a notable specific capacity of 358.0C/g at a 2.0 A/g rate. The material demonstrated a remarkable 49.5 Wh/kg energy density and a remarkable 1505.0 W/kg power density. 83.3 % of the initial capacity of the composite material remained even after 5000 cycles. This illustrates its continued stability and suggests that its operating lifetime may be increased. Besides; the hybrid electrode is used to detect the glucose in the specimen up to 0 mM to 2 mM. The electrochemical device showed a remarkable value of sensitivity of 1402 μA·cm−2 mM−1. As the field of energy storage technology develops, this dynamic composite may reveal completely new and exciting options.

Convenient room-temperature synthesis of sulfur and nitrogen co-doped NiCo-LDH coupled with CNTs on NiCo foam as battery-type electrode for high performance hybrid supercapacitor

Convenient room-temperature synthesis of sulfur and nitrogen co-doped NiCo-LDH coupled with CNTs on NiCo foam as battery-type electrode for high performance hybrid supercapacitor

Rational design of the binder-free polythiophene nanofibers deposited nickel foam for the high-performance aqueous asymmetric supercapacitor

Development of the binder-free electrode materials and employing in the supercapacitor is the essential footstep for high energy storage. The present study highlights the cost-effective synthesis strategy for the binder-free growth of the amorphous polythiophene nanofibers over the nickel foam substrate. The presence of functional bonds like CC, C-H, and C-S has confirmed the deposition of the polythiophene nanofibers on the nickel foam, while elemental mapping analysis detected the uniform distribution of Carbon and Sulfur elements over nanofibers. The surface structure of the polythiophene is transformed from nanofibers to a wire-like structure as the result of the monomer concentration variation. The optimized polythiophene film exhibited the highest areal capacitance of 1263.2 mF/cm2 at 2 mA/cm2 with 90.03% capacitance retention after 5000 cycles. Moreover, the aqueous asymmetric device (PTh//AC) is fabricated which delivered 31.5 F/g at 10 mA/cm2. The highest specific energy of PTh//AC device was 6.3 Wh/kg. Also, it showed good retention capability with 82.3% retention. Based on these results, the present investigation provides the performance metrics of the polythiophene nanofibers and highlights the potential utilization of the polythiophene-based supercapacitor in practical energy storage systems.

Biomass-Derived Carbon Materials for Advanced Metal-Ion Hybrid Supercapacitors: A Step Towards More Sustainable Energy

Modern research has made the search for high-performance, sustainable, and efficient energy storage technologies a main focus, especially in light of the growing environmental and energy-demanding issues. This review paper focuses on the pivotal role of biomass-derived carbon (BDC) materials in the development of high-performance metal-ion hybrid supercapacitors (MIHSCs), specifically targeting sodium (Na)-, potassium (K)-, aluminium (Al)-, and zinc (Zn)-ion-based systems. Due to their widespread availability, renewable nature, and exceptional physicochemical properties, BDC materials are ideal for supercapacitor electrodes, which perfectly balance environmental sustainability and technological advancement. This paper delves into the synthesis, functionalization, and structural engineering of advanced biomass-based carbon materials, highlighting the strategies to enhance their electrochemical performance. It elaborates on the unique characteristics of these carbons, such as high specific surface area, tuneable porosity, and heteroatom doping, which are pivotal in achieving superior capacitance, energy density, and cycling stability in Na-, K-, Al-, and Zn-ion hybrid supercapacitors. Furthermore, the compatibility of BDCs with metal-ion electrolytes and their role in facilitating ion transport and charge storage mechanisms are critically analysed. Novelty arises from a comprehensive comparison of these carbon materials across metal-ion systems, unveiling the synergistic effects of BDCs’ structural attributes on the performance of each supercapacitor type. This review also casts light on the current challenges, such as scalability, cost-effectiveness, and performance consistency, offering insightful perspectives for future research. This review underscores the transformative potential of BDC materials in MIHSCs and paves the way for next-generation energy storage technologies that are both high-performing and ecologically friendly. It calls for continued innovation and interdisciplinary collaboration to explore these sustainable materials, thereby contributing to advancing green energy technologies.

Chemical route synthesis of nanohybrid MoO3-rGO for high-performance hybrid supercapacitors

Asymmetric Hybrid supercapacitor (AHS) is distinguished by a combination of electrostatic and electrochemical storage mechanisms. High performance of AHS is based on MoO3 (MO) hybridized with reduced graphene oxide (rGO). In the present study, a single step hydrothermal method was used to synthesise MO and MoO3-rGO (MOG) nanohybrid materials. MO and MOG samples were then used to prepare electrodes. These electrodes were subjected to CV, GCD, and EIS analyses with three- and two-electrode systems. Results showed that the MOG-2 composite achieved a higher specific capacity of 607.82 C g−1 than bare MO at 96 C g−1 at a sweep rate of 2 mVs−1 in the three-electrode system. Thus, rGO can effectively enhance active sites for redox reactions. At current density of 1 A g−1, the MOG//rGO had the highest specific capacity of 188.40 C g−1. Based on GCD evaluation, the HSC coin cell device had a maximum energy density of 36.78 Whkg−1 and a power density 2546.84 Wkg−1and the device retained 87.6 % capacity after 10,000 cycles.

Interlaced-structural composite assembled by nickel cobalt layered double hydroxides and superfine coal for electrode material in high-performance hybrid supercapacitor

Nickel-cobalt hydrotalcite (NiCo-LDH) is widely acknowledged as a promising electrode material due to its high specific capacitance and energy density. However, in order to further enhance its cycle stability, the assistance of functional carbon materials is required. In this study, a superfine coal (FC) with an oxygen-enriched surface prepared through ball milling modification is incorporated into hydrothermal synthesis process of NiCo-LDH to form a composite known as NiCo-LDH/FC (NiCo-FC). When 0.325 g FC is added, the resulting NiCo-3FC exhibits an interlaced-structural characteristic along with excellent electrochemical properties and cycle stability. In a 6 M KOH electrolyte, NiCo-3FC demonstrates a significantly higher specific capacitance of 2101.03 F g−1 at a current density of 1 A g−1 compared to that of pristine NiCo-LDH (1706.44 F g−1). The hybrid supercapacitors (HSC) assembled using NiCo-3FC and popcorn carbon (PC) achieves a capacitance of 302.19 F g−1 at 1 A g−1 within the voltage range of 1.6 V, outperforming HSC assembled using NiCo-LDH and PC (257.58 F g−1), while exhibiting remarkable enhancement in cycle stability from 54.32 % to 83.63 % after undergoing 5000 cycles. Moreover, it displays a high energy density of 104.57 Wh kg−1 at a low power density of 0.79 kW kg−1, indicating that NiCo-3FC deserves recognition as a high-performance electrode material with significant practical value.

Bimetal-organic frameworks derived redox-type composite materials for high-performance energy storage

Electrodes and electroactive materials are crucial components in the development of supercapacitors due to their geometric properties. In this study, bimetal-organic frameworks (Bi-MOFs, ZIF-8@ZIF-67) were utilized as electrode materials for a high-performance hybrid supercapacitor (HSC) by designing a novel synthesis of metallic carbonate hydroxide/oxides. In particular, the Bi-MOFs function as a sacrificial precursor in the synthesis of hollow NiMn(CO3)0.5·0·.11H2O/ZnO@Co3O4 CNCs (NM-CH/ZnO@Co3O4 CNCs) cubic composite materials by a straightforward low-temperature treatment. The NM-CH/ZnO@Co3O4 CNCs exhibited exceptional electrochemical performance with high specific capacity of 196.3 ± 0.08 mAh/g, specific capacitance of 1179 ± 0.10 F g−1 at 0.5 A g−1, and outstanding cycling stability of 98% after 25,000 cycles compared to the other electrode materials. The porous and hollow structure, along with a large surface area, contributed to the enhanced electrochemical properties of the composite material. An HSC was constructed using NM-CH/ZnO@Co3O4 CNCs as the cathode and activated porous carbon (APC) as the anode, resulting in a device with a specific energy of 33 ± 0.12 Wh kg−1 and a power density of 19354 ± 0.07 W kg−1. The use of Bi-MOF electrodes presents new avenues for the development of high-performance energy storage materials, with the potential for industrial energy storage application demonstrated though the successful powering of portable lightbulbs.

ZnMnCo-S nanoneedle arrays as battery-type eletrodes for high-performance hybrid supercapacitors

Transition metal sulfides are used in the field of supercapacitors due to their remarkable electrical conductivity and superior energy density. However, few research has been conducted on how the sulfidation process affects the structure and electrochemical properties of electrodes. The nanoneedle array Zn-Mn-Co sulfide (ZMC-S/NF) electrode is prepared by directly growing on nickel foam (NF) via a two-step hydrothermal technique. During the first step, the Zn-Mn-Co carbonate hydroxide nanoneedle skeleton can be obtained. During the second step, the nanoneedle skeletons are etched, and rough nanoneedle arrays are created by the introduced sulfur ions,i.e., the sulfidation process. The ZMC-S/NF electrode exhibits a specific capacity of 1401.0 C g−1 at 2 A g−1. It still has excellent rate performance with a specific capacity of 1015.3 C g−1 at 20 A g−1. Moreover, it exhibits excellent cycling stability with 81.9% capacity retention after 10,000 cycles. ZMC-S/NF as the cathode and activated carbon (AC) as the anode are assembled to be a hybrid supercapacitor (HSC), which has an energy density of 43.4 Wh kg−1 at a power density of 700.4 W kg−1. The effect of adding Zn and Mn to the Co3S4 on energy band structure and density of states during the sulfidation process is calculated by the DFT. The HSC devices constructed by two series-connected ZMC-S/NF//AC can light a star made by ten 1.8 V-red Light Emitting Diodes (LEDs) for 10 minutes.

Hydrochloric acid induced microstructural reconfiguration from bulk α-NiS microspheres to porous/hollow NiSx microspheres for high-performance hybrid supercapacitor

Nickel sulfide is well known as a promising energy storage/conversion material considering its high redox activity, high theoretical capacity, easy preparation, and rich phase structures. Unfortunately, nickel sulfide prepared by conventional methods usually exhibits a bulk structure, which significantly limited its charge storage. To overcome this obstacle, we developed a facile hydrochloric acid-induced structure reconstruction strategy to fabricate porous and hollow structured nickel sulfide via a one-step hydrothermal process. We found that nickel sulfide undergoes de-nickelization in the presence of 3 M hydrochloric acid, resulting in the transformation from bulk structure to porous/hollow structures, accompanied by a transition from nickel-rich phase (α-NiS) to nickel-deficient phase (Ni3S4 or NiS2). The electrochemical results demonstrated the obviously improved specific capacity of nickel sulfide after structure reconstruction, among which the porous NS-HCl-1 h (α-NiS/Ni3S4) microspheres delivers the highest specific capacity (204.4 mAh g-1 at 1 A g-1) and show a rate performance about 50.0% from 1 to 20 A g-1. The assembled NS-HCl-1 h//rGO supercapacitor delivers a maximum energy density of 47.1 Wh kg-1 at a power density of 803.6 W kg-1, and maintain a capacity retention rate about 88.6% after 10,000 cycles. This work provides a novel method and contributes new insight for the structural reconstruction of transition metal sulfides (TMSs).

Ultrasonic-Assisted Electrodeposition of Mn-Doped NiCo2O4 for Enhanced Photodegradation of Methyl Red, Hydrogen Production, and Supercapacitor Applications

This paper presents a novel ultrasonic-assisted electrodeposition process of Mn-doped NiCo2O4 onto a commercial nickel foam in a neutral electroplating bath (pH = 7.0) under an ultrasonic power of 1.2 V and 100 W. Different sample properties were studied based on their crystallinity through X-ray diffraction (XRD), morphology was studied through scanning electron microscopy (SEM), and photodegradation was studied through ultraviolet–visible (UV–Vis) spectrophotometry. Based on the XRD results, the dominant crystallite phase obtained was shown to be a pure single NiCo2O4 phase. The optical properties of the photocatalytic film showed a range of energy band gaps between 1.72 and 1.73 eV from the absorption spectrum. The surface hydroxyl groups on the catalytic surface of the Mn-doped NiCo2O4 thin films showed significant improvements in removing methyl red via photodegradation, achieving 88% degradation in 60 min, which was approximately 1.6 times higher than that of pure NiCo2O4 thin films. The maximum hydrogen rate of the composite films under 100 mW/cm2 illumination was 38 μmol/cm2 with a +3.5 V external potential. The electrochemical performance test also showed a high capacity retention rate (96% after 5000 charge–discharge cycles), high capacity (260 Fg−1), and low intrinsic resistance (0.8 Ω). This work concludes that the Mn-doped NiCo2O4 hybrid with oxygen-poor conditions (oxygen vacancies) is a promising composite electrode candidate for methyl red removal, hydrogen evolution, and high-performance hybrid supercapacitor applications.

Cation-driven self-assembly of core–shell covalent organic frameworks@Ti3CN MXene nanospheres for high-performance aqueous zinc-ion hybrid supercapacitors

Rechargeable aqueous Zn-ion hybrid supercapacitors (ZISCs) with the superiorities of high theoretical capacity, low redox potential and aqueous electrolytes with superior ionic conductivity (∼1 S cm−1) are promising energy storage systems. However, a primary concern persists due to the absence of cathode materials with both high energy densities and satisfactory cycling stability for robust ZISCs. In this study, we design a spherical core–shell covalent organic frameworks@Ti3CN MXene (CM-P) cathode via a cation-driven electrostatic self-assembly strategy. The CM-P with the constructed heterostructures shows both well-organized pore channels and excellent intrinsic conductivity, facilitating fast accessibility to intrinsic redox-active sites (such as C = O and N), and promoting effective ion diffusion characterized by low energy barriers. Consequently, the CM-P cathodes demonstrate excellent electrochemical performance, featuring an ultrahigh specific capacity of 260 mAh/g at 0.1 A, a high-rate capability with 68 % retention at 1 A/g, and long-term cycling stability. First-principle calculations elucidate that the enhanced charge-storage mechanism relies on the heterostructures of CM-P, accelerating ion adsorption/diffusion and electron transfer. Furthermore, the assembled CM-P//Zn ZISCs devices show a high energy density of 217.1 Wh kg−1 along with power density of 22.3 kW kg−1. This work provides an innovative approach to design COFs-based heterostructures for advanced ZISCs.

High-Performance Zinc-Ion Hybrid Supercapacitor from Guilin Sanhua Liquor Lees-Derived Carbon Materials.

Aqueous zinc-ion hybrid supercapacitors (ZHSCs) have attracted considerable attention because they are inexpensive and safe. However, the inadequate energy densities, power densities, and cycling performance of current ZHSC energy-storage devices are impediments that need to be overcome to enable the further development and commercialization of this technology. To address these issues, in this study, we prepared carbon-based ZHSCs using a series of porous carbon materials derived from Sanhua liquor lees (SLPCs). Among them, the best performance was observed for SLPC-A13, which exhibited excellent properties and a high-surface-area structure (2667 m2 g-1) with abundant micropores. The Zn//SLPC-A13 device was assembled by using 2 mol L-1 ZnSO4, SLPC-A13, and Zn foil as the electrolyte, cathode, and anode, respectively. The Zn//SLPC-A13 device delivered an ultrahigh energy density of 137 Wh kg-1 at a power density of 462 W kg-1. Remarkably, Zn//SLPC-A13 retained 100% of its specific capacitance after 120,000 cycles of long-term charge/discharge testing, with 62% retained after 250,000 cycles. This outstanding performance is primarily attributed to the SLPC-A13 carbon material, which promotes the rapid adsorption and desorption of ions, and the charge-discharge process, which roughens the Zn anode in a manner that improves reversible Zn-ion plating/stripping efficiency. This study provides ideas for the preparation of ZHSC cathode materials.

High-performance Zn-ion hybrid supercapacitors based on biomass-derived hierarchical porous carbon through template-activated bifunctional induced and ice-crystal assisted strategy

As a highly desirable cathode material for Zn ion hybrid supercapacitors (ZHSCs), biomass-derived carbon precursor shrinks and collapses at elevated temperatures resulting in an impeded internal morphology, which severely hampers ion storage and transport. Herein, a unique porous carbon with multi-level pore structures is produced by a one-step carbonization-activation process. The Gelatin with rich functional groups is employed as the gel-state biomass precursor and the ZnCl2 acted as both a template and an activator. Furthermore, the growth of ice crystals during freeze-drying prevents the carbon framework from collapsing and self-polymerizing of ZnCl2, endowing the prepared porous carbon with a high specific surface area (1336 m2/g) and inheritance of biomass precursor heteroatoms (including N and O). Therefore, at 0.5 A/g, the prepared material displays a desirable specific capacitance of 337.6 F/g in 6 M KOH. In particular, the assembled ZHSC simultaneously shows excellent cycling performance (after 10000 cycles, the specific capacitance increases to 95.6% at 10 A/g) and high energy and power density (120.1 Wh/kg at 450 W/kg). This work provides important insights for the facile preparation of electrode materials for high-performance ZHSCs.

Design and construction of conductive polymer PPy anchored NiCo bi-metal sulfide composite electrode materials for high-performance hybrid supercapacitor and electrochemical hydroquinone sensor

The development of green energy materials has a crucial role in the energy crisis and environmental issues. The dual-functional oriented strategy was used to prepare new electrode material PPy@NCS by using glycerol as a template. The electrode material PPy@NCS-5 exhibits a higher specific capacitance of 2011.6 F g−1 at 1 A g−1 and delivers excellent long-term cycling stability with 93.3 % of its specific capacitance retained at 20 Ag−1 after 5000 cycles. A hybrid supercapacitor (HSC) combining PPy@NCS-5 and activated carbon (AC) yields a high energy density of 44.6 Wh kg−1 at a power density of 15,005.6 W kg−1. Furthermore, the as-prepared PPy@NCS-5/GCE can be used as an HQ sensor, which displays high sensitivity (0.026 μA/μM), an extraordinary linear response ranging (0.5–1923 μM), and a low detection limit (0.026 μM).

Graphene nanoribbons on three-dimensional carbon nanomaterials for high-performance flexible zinc-ion hybrid supercapacitors

The rational design of electrodes is crucial for the performance and practical applications of flexible zinc-ion hybrid supercapacitors (ZIHS). In this paper, we have developed an easy strategy to design electrodes based on current collectors with vertically aligned nanohole arrays on their surfaces. Zinc nanosheet arrays were deposited on a porous aluminum oxide/aluminum (AAO) film to form a Zn@AAO anode. Graphene nanoribbons (GR) unzipped for carbon nanotubes were coated on a unique three-dimensional carbon pre-coated AAO (CAAO) film to form a GR@CAAO composite cathode. After assembling with ZnSO4/gelatin gel electrolyte, a quasi-solid Zn@AAO//GR@CAAO ZIHS with a potential of 1.6 V was obtained. The as-prepared ZIHS exhibits an areal capacitance of 156 mF cm−2 at 0.25 mA cm−2 and a high energy density of 56 μW h cm−2 at 0.202 mW cm−2, an excellent flexibility as well as long cycle life.

Void space expanded hierarchical battery-type composite material for high-capacity hybrid supercapacitors

Synergetic modulation of battery-type materials with excellent electrochemical activity is an important feature to elevate the energy storage performance in the hybrid supercapacitors (HySCs). In this study, we synthesized a void space expanded nickel sulfide@nickel molybdenum oxysulfide on Ni foam (NixSy@NiMoOx-1Sy/Ni foam) using wet-chemical sulfurization technique. The growth solution, composed of sulfur ions, partially converts NiMo DHs into NiMoOx-1Sy and the Ni foam substrate into NixSy, resulting in the formation of a hybrid-composite. Increased mass-loading growth of NixSy@NiMoOx-1Sy/Ni foam and multi-oxidation states of nickel species in the composite were confirmed using the X-ray photoelectron spectroscopy analysis. The binder-free NixSy@NiMoOx-1Sy/Ni foam electrode was electrochemically cycled in aqueous KOH electrolyte, demonstrating battery-type redox behavior with enhanced capacity (310.6 mAh/g) compared to the NixSy/Ni foam (221.1 mAh/g) and NiMo DHs/Ni foam (142.5 mAh/g) electrodes, which could be ascribed to the improved electrical conductivity, adequate electrolyte diffusivity, and fast charge transfer properties. Furthermore, a two-electrode system based HySC was assembled using the battery-type NixSy@NiMoOx-1Sy/Ni foam and capacitive-type activated carbon, enabling a maximum energy density (58.8 Wh/kg) and power density (2666.7 W/kg) with good cycling stability and coulombic efficiency. The high-performance HySCs were used to power-up portable lighting devices, demonstrating their practical use in real-time applications.

Sonochemical synthesis of CoNi layered double hydroxide as a cathode material for assembling high performance hybrid supercapacitor

Fabricating battery-type electrode materials with large specific surface area and mesopores is an efficient method for enhancing the electrochemical performance of supercapacitors. This method may provide more active sites for Faradic reactions and shorten the ion-diffusion paths. In this study, the CoNi layered double hydroxides (LDHs) with the morphology of nanoflowers and nanoflakes were prepared in solutions with pH values of 7.5 (CoNi LDH-7.5) and 8.5 (CoNi LDH-8.5) via a simple sonochemical approach. These CoNi LDHs possessed large specific surface areas and favourable electrochemical properties. The CoNi LDH-7.5 delivered a specific capacity of 740.8C/g at a current density of 1 A/g, surpassing CoNi LDH-8.5 with 668.1C/g. The hybrid supercapacitor (HSC) was assembled with activated carbon as the anode and CoNi LDH as the cathode to assess its practical application potential in the field of electrochemical energy storage. The CoNi LDH-7.5//AC HSC achieved the highest energy density of 35.6 W h kg−1 at a power density of 781.1 W kg−1. In addition, both HSCs exhibited little capacity decay over 5,000 cycles at a high current load of 8 A/g. These electrochemical properties of CoNi LDHs make them promising candidates for battery-type electrode materials. The current sonochemical method is simple and can be applied to the preparation of other LDHs-based electrode materials with favourable electrochemical performance.

Anion storing, oxygen vacancy incorporated perovskite oxide composites for high-performance aqueous dual ion hybrid supercapacitors

Dual ion storage hybrid supercapacitors (HSCs) are considered as a promising device to overcome the limited energy density of existing supercapacitors while preserving high power and long cyclability. However, the development of high-capacity anion-storing materials, which can be paired with fast charging capacitive electrodes, lags behind cation-storing counterparts. Herein, we demonstrate the surface faradaic OH− storage mechanism of anion storing perovskite oxide composites and their application in high-performance dual ion HSCs. The oxygen vacancy and nanoparticle size of the reduced LaMnO3 (r-LaMnO3) were controlled, while r-LaMnO3 was chemically coupled with ozonated carbon nanotubes (oCNTs) for the improved anion storing capacity and cycle performance. As taken by in-situ and ex-situ spectroscopic and computational analyses, OH− ions are inserted into the oxygen vacancies coordinating with octahedral Mn with the increase in the oxidation state of Mn during the charging process or vice versa. Configuring OH− storing r-LaMnO3/oCNT composite with Na+ storing MXene, the as-fabricated aqueous dual ion HSCs achieved the cycle performance of 73.3% over 10,000 cycles, delivering the maximum energy and power densities of 47.5 W h kg−1 and 8 kW kg−1, respectively, far exceeding those of previously reported aqueous anion and dual ion storage cells. This research establishes a foundation for the unique anion storage mechanism of the defect engineered perovskite oxides and the advancement of dual ion hybrid energy storage devices with high energy and power densities.

One-step hydrothermal synthesis of Fe3+-doped sheet-like δ-MnO2 for high-performance hybrid supercapacitors

KMnO4 was the Mn source, FeCl3·6H2O was the Fe source, and Fe3+-doped δ-MnO2 was prepared by a one-step hydrothermal method. The effects of different addition amounts of FeCl3·6H2O on the morphology, crystal structure and electrochemical properties of MnO2 were studied. The results show that pure phase MnO2 has a sheet morphology. The doping of Fe3+ decreases the size of sheet MnO2 and increases the specific surface area of MnO2, but XRD shows that MnO2 still retains the δ-type. At the same time, the doping of Fe3+ causes MnO2 to expose high-energy crystal faces, which enhances the electrochemical activity of MnO2. Further studies found that Fe3+ of FeCl3·6H2O plays an important role, while Cl− has nothing to do with it. The electrochemical test results show that when 3 mmol Fe3+ is added, the specific capacitance of MnO2–0.3 reaches the maximum value (196 F g−1), which is much higher than that of pure MnO2 (123.4 F g−1). Finally, the hybrid supercapacitor assembled from MnO2–0.3 and activated carbon has an energy density of 19.9 Wh kg−1, which can maintain 83.3 % of the initial value after 20,000 cycles. This work provides us with a new way to control the structure of electrode materials.