Na2SO4 Aqueous Electrolyte Research Articles

Ultrahigh voltage window, preeminent energy density aqueous supercapacitor derived from honeycomb-like porous carbon decorated with carbon dots

The development of advanced electrode materials with high specific capacitance and wide voltage window is of great importance in improving the low energy density of aqueous supercapacitors (ASCs). Herein, a novel heteroatoms doped 3 D porous carbon decorated with 0 D carbon dots is prepared from egg whites and yolks. The unique honeycomb-like interconnected pore structure and multi-component feature endows the prepared material with specific surface area (1999.3 m2/g), high pore volume (1.22 cm3/g) with abundant micropores (0.67 cm3/g) and multi-doped heteroatoms including P, S, O and N, leading to excellent specific capacitance of 472.9 F/g at 1 A/g. More importantly, the symmetric supercapacitor assembled from the prepared porous carbon exhibits the voltage window as high as 2.6 V in 1.5 M Na2SO4 aqueous electrolyte. Hence, the symmetric supercapacitor achieves a leap forward in energy density (107.5 Wh/kg at a power density of 650 W/kg and maintains about 65.2 Wh/kg at 26,000 W/kg) relative to other ASCs. These preeminent results provide important insight for the design of aqueous symmetric carbon-based supercapacitor with ultrahigh voltage window and energy density.

Synthesis and characterization of MnO2/Eggplant carbon composite for enhanced supercapacitors

In this paper, the eggplant carbon (EC)was derived from eggplant skin by one-step carbonization method. Subsequently, the MnO2/eggplant carbon (MnO2/EC) composite was prepared viain-situ hydrothermal method. The morphology and structure as well as electrochemical performance were investigated through a series of characterization and tests. The results showed that the urchin shaped structures of MnO2 was successfully loaded on the surface of EC. The electrochemical studies indicated that the specific capacitance of the MnO2/ECcomposite could reach 652.5F/g at 0.5 A/g in 1 M Na2SO4 aqueous electrolyte. In addition, the MnO2/EC composite exhibits excellent cyclic stability after 10000 cycles, which might be ascribed to the synergistic effect of MnO2 and EC for the improvement of electrochemical performance. Taken together, this work demonstrated that MnO2/EC composite can be used in the aspect of energy storage for high-performance supercapacitors.

New PEDOT Derivatives Electrocoated on Silicon Nanowires Protected with ALD Nanometric Alumina for Ultrastable Microsupercapacitors.

This work deals with electroactive conducting polymers (ECPs) used as a complementary component on purely capacitive silicon nanowires protected by a 3 nm alumina layer. Accordingly, in this work, we use a fast and simple deposition method to create a pseudocapacitive material based on the electropolymerization in aqueous micellar media (SDS and SDBS 0.01 M) of hydroxymethyl-EDOT (EDOT-OH) onto 3 nm alumina-coated silicon nanowires (Al3@SiNWs). The composite material displays remarkable capacitive behavior with a specific capacitance of 4.75 mF·cm−2 at a current density of 19 µA·cm−2 in aqueous Na2SO4 electrolyte.

Synthesis of dumbbell-shaped ZnO nanostructures for energy storage and photocatalytic dye degradation applications

ABSTRACT In this present work, a dumbbell-shaped ZnO nanostructure was successfully synthesized by a hydrothermal method through optimized hydrothermal temperature (200°C). The XRD showed the formation of the hexagonal crystalline structure with high-phase purity. The FE-SEM images of ZnO prepared at a hydrothermal temperature of 200°C exhibits a well-defined, monodispersed dumbbell-shaped morphology. The chemical surface states were investigated using XPS. The prepared ZnO-based anode material was tested using a 1M Na2SO4 aqueous electrolyte with a three-electrode cell configuration. The ZnO 200°C electrode materials delivered a high specific capacitance of 316 F/g at 1 A/ and columbic efficiency of 96% and capacitance retention of 92% after 10,000 cycles at the current density of 10 A/g. Due to its inherent properties, the maximum degradation efficiency of 91% for 180 min was obtained from a dumbbell-shaped ZnO (200°C) sample. The ZnO nanostructured materials suggest potential applications for supercapacitors and textile wastewater treatments.

Electrochemical Performance of NASICON-structured Na3-x V2-xTix(PO4)3 (0.0 < x < 1.0) as aqueous Na-ion battery positive electrodes

Phosphate frameworks with NASICON structure are among the most studied and applied Li- and Na-ion battery electrode and electrolyte materials. In this work, the NASICON-structured Na3-xV2-xTix(PO4)3 with x = 0.0, 0.25, 0.5, 0.75 and 1.0 are successfully prepared by conventional solid-state synthesis and characterized in detail as potential aqueous Na-ion battery positive electrodes with improved charge capacity and cycling stability. Structural analysis using powder X-ray diffractometry indicates that titanium substitutes vanadium at arbitrary concentration without significant distortion of the NASICON structure. The results show that titanium content in this system directly correlates with its aqueous stability when cycled in simple 1 M Na2SO4 aqueous electrolyte within the vanadium redox potential range. Electrochemical kinetics and charge capacity measurements show Na2VTi(PO4)3 as well as Na2.25V1.25Ti0.75(PO4)3 to be stable positive electrodes in simple aqueous electrolyte solutions. Hybrid density functional theory analysis of V-O chemical bonding suggests that it is stabilized by the presence of titanium in the NASICON structure. In this work, we show that the observed capacity loss in full symmetric cells is caused by the capacity imbalance between positive and negative electrodes which progresses during cycling but not the aqueous materials stability per se. This imbalance is caused by several parasitic reactions, the most important being the oxygen reduction reaction catalyzed by Ti(III) species. Careful mitigation and management of this reaction could, in principle, allow for the preparation of truly capacity balanced cells (i.e. without a need of any electrode overcapacity), and superior cycling stability.

MgO template-assisted synthesis of hierarchical porous carbon with high content heteroatoms for supercapacitor

Traditional porous carbon obtained by potassium hydroxide activation are facing with complex preparation process, low heteroatoms content and sluggish ion-transport kinetics caused by their amorphous microporous structure. Herein, we develop a facile method to prepare heteroatom-doped hierarchical porous carbon (HPC) using magnesium oxide as template and polyacrylamide as raw material without any activation. MgO and polyacrylamide can be closely combined by electrostatic self-assembly, so as to give full play to the role of MgO template. The prepared samples exhibit three-dimensional (3D) interconnected hierarchical porous structure, large specific surface area (SSA) and a large amount of nitrogen (10.97 at.%) and oxygen (10.3 at.%) functional groups. Benefiting from their synergy, the optimized NHPC-700 electrode possesses a high specific capacitance of 295.3 F g−1 at 0.5 A g−1, excellent rate characteristics and superior cycling performance (100.76 % capacitance retention after 10,000 cycles). Furthermore, the assembled NHPC-700//NHPC-700 symmetrical supercapacitor provides a high energy density of 15.16 Wh kg−1 in 1 M Na2SO4 aqueous electrolyte. The results fully demonstrate that the obtained hierarchical porous carbon shows promising application in supercapacitors.

Synergetic Effect on Electrochemical Performance of Activated Carbon - Multiwalled Carbon Nanotubes Supercapacitor using various Electrodes in Aqueous Electrolyte

An Electrical double-layer capacitor (EDLC) has been fabricated with activated carbon (AC) and multi-walled carbon nanotubes (MWCNTs), which in turn were synthesized from Pongamia pinnata fruit shell and its seed oil, respectively. The activated carbon was produced by the chemical activation process at varying carbonization temperatures from 600-900 °C for 5 hours in N2 atmosphere. The obtained activated carbon had a high surface area of 1170 m2 g-1 and a total pore volume of 0.5907 cm3 g-1. The surface area of MWCNTs was 216.1 2 m2 g-1 and the total pore volume was 1.5067 cm3 g-1. The as-prepared AC and MWCNTs were characterized by surface area analysis using Brunner-Emmett-Teller method (BET), X-ray diffraction analysis (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopic analysis, Field emission scanning electron microscopy (FESEM), High-resolution transmission electron microscopy (HR-TEM), Energy-dispersive X-ray spectroscopy (EDAX) and DFT (Density functional theory). The electrochemical performance of AC-MWCNTs (25:75) Stainless steel (SS) electrode and Graphite sheet electrode (GE) were studied by cyclic voltammetry, Galvanostatic charge-discharge and electrochemical impedance spectroscopy using 0.5 M Na2SO4 aqueous electrolyte. It has shown a specific capacitance of 174 Fg-1 and 95.26 Fg-1 respectively, using the three-electrode system at a current density of 1 mA g-1. The AC-MWCNT (25:75) SS electrode has exhibited excellent specific capacitance (CSP) and its Specific energy density and Power density were greater than AC-MWCNT (25:75) GE. The electrochemical performance of AC-MWCNT (25:75) SS electrode was identified as a suitable, low-cost and promising energy storage device for future generations. The present investigation attempts to promote the supercapacitor device in the context of available and future technologies for alternative energy systems with outstanding performance.

Phytosynthesis of Co3O4 Nanoparticles as the High Energy Storage Material of an Activated Carbon/Co3O4 Symmetric Supercapacitor Device with Excellent Cyclic Stability Based on a Na2SO4 Aqueous Electrolyte.

The benign preparation of cobalt oxide nanoparticles (Co3O4-NPs) was performed using marine red algae extract (Grateloupia sparsa) as a simple, cost-effective, scalable, and one-pot hydrothermal technique. The nominated extract was employed as an environmental reductant and stabilizing agent. The resultant product showed the typical peak of Co3O4-NPs around 400 nm wavelength as ascertained by UV–vis spectroscopy. Size and morphological techniques combined with X-ray diffraction (XRD) showed the small size of Co3O4-NPs deformed in a spherical shape. The activated carbon (AC) electrode and Co3O4-NP electrode delivered a specific capacitance (Csp) of 125 and 182 F g–1 at 1 A g–1, respectively. The energy density of the AC and AC/Co3O4 electrodes with a power density of 543.44 and 585 W kg–1 was equal to 17.36 and 25.27 Wh kg–1, respectively. The capacitance retention of designed electrodes was 99.2 and 99.5% after 3000 cycles. Additionally, a symmetric AC/Co3O4//AC/Co3O4 supercapacitor device had a specific capacitance (Csp) of 125 F g–1 and a high energy density of 55 Wh kg–1 at a power density of 650 W kg–1. Meanwhile, the symmetric device exhibited superior cyclic stability after 8000 cycles, with a capacitance retention of 93.75%. Overall, the adopted circular criteria, employed to use green technology to avoid noxious chemicals, make the AC/Co3O4 nanocomposite an easily accessible electrode for energy storage applications.

Ruthenium dioxide anchored on reduced graphene oxide nanocomposite for 1.2 V symmetric supercapacitor devices

In this work, the high-performance symmetric electrochemical capacitor based on ruthenium dioxide anchored on reduced graphene oxide nanostructures was developed. The created system consists of the negative and positive electrodes with Na2SO4 aqueous electrolyte. The symmetric capacitor devices electrodes were tested in the potential range of 0 to 1.2 V. As a result, at 2 A/g,the rGO/RuO2 and RuO2 electrodes gained higher energy (41 Wh kg−1 and 31 Wh kg−1) and power densities (1.2 kW kg−1 and 0.98 kW kg−1). After the 2000th cycle,the rGO/RuO2 electrode has such a high cyclic efficiency of 96%, which is considerably higher than the pure RuO2 (88%).This is due to the anchoring of high conducting rGO in rGO/RuO2 nanocomposite. These findings reinforce the idea of graphene-based nanocomposites having as a safe aqueous electrolyte in high-voltage energy storage devices.

Novel green synthesis of graphene oxide-manganese dioxide using solution plasma process for energy storage

Graphene oxide-manganese dioxide (GO-MnO2) forms an interesting family of nanocomposites that have been widely studied and applied to many electrochemical applications, including supercapacitors. However, a number of reported preparation methods still suffer several disadvantages, including complex preparation, long synthesis time, and detrimental effects on the environment as a result of excessive use of chemicals. In contrast, solution plasma process (SPP) offers a simple method that can be used to synthesize nanomaterials with minimal use of chemical reagents and short preparation time under ambient processing conditions. This work demonstrated that SPP-based preparation of the GO-MnO2 composite can be achieved. Moreover, the SPP regime was found to enable interaction between the Mn ions and the exfoliated GO sheets, with the capability of upscaling the preparation. The highest specific capacitance of the GO-MnO2 composite was obtained when only 10 min of SPP discharge time was used, resulting in the specific capacitance of 218 F g−1 at a scan rate of 5 mV s−1 in 1 M Na2SO4 aqueous electrolyte solution. This method provides a facile in situ approach to deposit MnO2 onto the GO sheets and could offer a promising, green alternative strategy to prepare similar electrode materials for other applications.

Computation and Investigation of Two-Dimensional WO3·H2O Nanoflowers for Electrochemical Studies of Energy Conversion and Storage Applications.

The aim of this study is to prepare a two-dimensional (2D) WO3·H2O nanostructure assembly into a flower shape with good chemical stability for electrochemical studies of catalyst and energy storage applications. The 2D-WO3·H2O nanoflowers structure is created by a fast and simple process at room condition. This cost-effective and scalable technique to obtain 2D-WO3·H2O nanoflowers illustrates two attractive applications of electrochemical capacitor with an excellent energy density value of 25.33 W h kg–1 for high power density value of 1600 W kg–1 and good hydrogen evolution reaction results (low overpotential of 290 mV at a current density of 10 mA cm–2 with a low Tafel slope of 131 mV dec–1). A hydrogen evolution reaction (HER) study of WO3 in acidic media of 0.5 M H2SO4 and electrochemical capacitor (supercapacitors) in 1 M Na2SO4 aqueous electrolyte (three electrode system measurements) demonstrates highly desirable characteristics for practical applications. Our design for highly uniform 2D-WO3·H2O as catalyst material for HER and active material for electrochemical capacitor studies offers an excellent foundation for design and improvement of electrochemical catalyst based on 2D-transition metal oxide materials.

KMnO4-assisted synthesis of hierarchical porous carbon with ultrahigh capacitance for supercapacitor

Porous carbon obtained by the conventional method (KOH/ZnCl2 chemical activation after carbonization) is faced with long ion diffusion distance, large ion diffusion resistance, which resulting in unsatisfactory electrochemical properties. Herein, we report a facile method to synthesize oxygen rich hierarchical porous carbon (OHPC) using corn stalks as carbon precursor and KMnO4 act as activator. Due to the high specific surface area, hierarchical porous framework and abundant oxygen functional groups, the optimized OHPC-600 displays a large specific capacitance of 464.7 F g−1 at 0.5 A g−1 and still maintains a large specific capacitance of 253.3 F g−1 even at 50 A g−1, suggesting superior rate property. More interestingly, the as-assembled symmetric supercapacitor shows a large energy density of 21.0 W h kg−1 and good cycle stability (the retention rate is 89.8% after 10,000 cycles) in 1 M Na2SO4 aqueous electrolyte. This work provides an excellent renewable candidate and a practicable route design strategy for conversion of biowaste into excellent performance electrode material.

Three‐Dimensional Porous Carbon Materials from Coix lacryma‐jobi L. Shells for High‐Performance Supercapacitor

AbstractThree‐dimensional (3D) porous carbon materials are widely concerned because of their excellent electrochemical performance in supercapacitors. Herein, a new porous Coix lacryma‐jobi L. shells‐based carbon (CSC) is prepared by carbonization and activation for super‐capacitors. The obtained CSC‐3 (CSC‐x, x: KOH/CSC mass ratio) possesses abundant porous structures, some functional groups with nitrogen and oxygen atoms, and good electrochemical performance. When the mass ratio of KOH to CSC is 3 : 1, the obtained CSC‐3 has the largest specific surface area (SSA, 1191.7 m2 g−1). Besides the material exhibits good electrochemical capability in the three‐electrode system with 6 m KOH aqueous electrolyte, such as desirable specific capacitance (at 0.5 A g−1, the specific capacitance is 413.5 F g−1), ideal rate performance (from 0.5 A g−1 to 10 A g−1, the specific capacitance retention rate is 70.86 %) and long cycle life (the specific capacitance only reduced by 2.47 % after 5000 cycles at 0.5 A g−1). Assembled symmetric supercapacitor (CSC‐3//CSC‐3) shows gratifying energy density (11.58 Wh Kg−1 at the power density of 324.93 W Kg−1 in 6 m KOH aqueous electrolyte and 14.67 Wh Kg−1 at 474.93 W Kg−1 in 1 m Na2SO4 aqueous electrolyte). This work provides possibility of utilizing waste Coix lacryma‐jobi L. shells to produce low‐cost and high‐performance super‐capacitor electrode materials for sustainable electrochemical energy storage.

MnO2-MXene Composite as Electrode for Supercapacitor

A MnO2-MXene composite material is reported, in which MnO2 particles have been grown onto Ti3C2 MXene flakes. Thanks to its interconnected structure, it can not only boost the low electrical conductivity of MnO2, but also suppress the restacking of MXene flakes. As an electrode material in a three-electrode cell, the composite showed greater capacitance and improved stability performance than raw MnO2 in both KOH and Na2SO4 aqueous electrolytes. Equipped with MnO2–MXene composite material as positive and activated carbon as negative, an asymmetric device using Na2SO4 as electrolyte displayed an energy density of 20 Wh kg−1 at 500 W kg−1 power density. On the other hand, the device operated in KOH electrolyte showed an energy density of 17 Wh kg−1 at 400 W kg−1, and 11 Wh kg−1 at 8 kW kg−1.

Simple and efficient CVD synthesis of graphitic P-doped 3D cubic ordered mesoporous carbon at low temperature with excellent supercapacitor performance

Heteroatom doping is a promising strategy for improving the electrochemical performance of carbon materials. Herein, we spotlight an advantageous, simple, and efficient CVD synthesis of P-doped 3D cubic ordered mesoporous carbon (POMC) for the first time. The POMC was prepared by pyrolysis of acetylene/triphenylphosphine (C2H2/Ph3P) mixture at relatively low temperature over Fe-KIT-6 as a sacrificial template. The ensuing P-doped OMC showed an enhanced porous texture than an undoped counterpart with a specific surface area of 403.5 m2/g, pore volume of 0.545 cm3/g, average pore size of 4.64 nm and suitable heteroatom functionalities with P and O contents of 0.13% and 9.83%, correspondingly. The obtained POMC exhibited a much higher specific capacitance of 288F/g at 0.2 A/g (175F/g for OMC), good cyclic stability of 97.6 %, and good rate capability than pristine OMC in 6 M KOH. It is equivalent to or improved than various stated mono doped and even dual doped porous carbon electrodes. Furthermore, a symmetric supercapacitor (POMC//POMC) was fabricated with 1 M Na2SO4 aqueous neutral electrolyte exhibits high cycling stability (89.3%) even with a wide potential window (2.0 V) and offers a relatively high energy density (10.01 Wh/kg) with a power density of 300 W/kg.

Glucosamine derived hydrothermal carbon electrodes for aqueous electrolyte energy storage systems.

Nitrogen-doped porous hard carbons are synthesized by hydrothermal carbonization method (HTC) using glucosamine as biosource and treated at different carbonization temperatures in nitrogen environment (500, 750, 1000 °C). The electrochemical performances of hard carbons electrode materials for aqueous electrolyte sodium ion batteries are examined to observe the effect of two different voltage ranges (-0.8-0.0) V and (0.0-0.8) V in 1.0 M Na2SO4 aqueous electrolyte. The best electrochemical performances are acquired for the 1000 °C treated glucosamine (GA-1000) porous carbon sample that provides ~96 F/g capacitance value in the negative voltage range (between -0.8 and 0.0) V. The sodium diffusion coefficient of the GA-1000 carbon calculated by electrochemical impedance measurements is found to be 1.5 × 10-14 cm2/s.

Nitrogen-doped porous carbon nanosheets for high-performance supercapacitors

Two-dimensional (2D) porous carbon nanosheets have received widespread attention in supercapacitor because of their high specific surface area, high aspect ratio and short ion diffusion distance. Here, we develop a novel strategy to prepare 2D porous nitrogen-doped carbon nanosheets (NCS) using MgAl-LDH as the template by electrostatic self-assembly with anionic polyacrylamide, then followed carbonization and KOH activation. The optimized NCS-700 samples possess high specific surface area, hierarchical porous sheet-like structure and rich N (3.15 at%) and O (9.58 at%) functional groups. As an electrode material, the NCS-700 samples exhibit a high specific capacitance of 356 F g−1 at 0.5 A g−1 and superior rate characteristic (228 F g−11 at 30 A g−1), as well as long lifespan. Moreover, the assembled NCS-700//NCS-700 symmetrical supercapacitor shows a high energy density of 29.0 Wh kg−1 and outstanding cycling stability in 1 M Na2SO4 aqueous electrolyte. Therefore, the above results show that this work provides a new method for the synthesis of porous carbon sheets for high performance supercapacitor.

Etlingera elatior leaf agricultural waste as activated carbon monolith for supercapacitor electrodes

Recently, biomass waste has become the focus of several researchers because it has promising potential when processed into porous activated carbon. Abundant availability, uncomplicated processing, and more economical are the reasons for choosing biomass as the basic material for making carbon electrodes for electric energy storage supercapacitors. In this study, Etlingera elatior waste biomass is processed into activated carbon by heating at high temperature and impregnation of 0.5 M ZnCl2. The monolith sample was optimized through a single-stage integrated high-temperature pyrolysis process. Where the process of carbonization of N2 gas from a temperature of 30 °C to 600 °C followed by a physical activation process of CO2 gas to a temperature of 800 °C. Determination of the physical properties of the electrodes through density characterization, while the electrochemical properties were analyzed by cyclic voltammetry and galvanostatic charge discharge methods. Cyclic voltammetry and galvanostatic charge discharge analysis were performed with 1 M Na2SO4 aqueous electrolyte at a voltage of 0–1 V and a scan rate of 1 mV/s. Furthermore, the high electrochemical behavior of the CV method was found to be 108 F/g, while for the gcd method, the specific capacitance was much higher at 148 F/g at a constant current density of 1.0 A/g. Further calculations found an energy density of 8.23 Wh/kg and a power density of 161 W/kg. These results support the optimization of 0.5 M ZnCl2 impregnated Etlingera elatior leaves as the base material for activated carbon electrodes to increase the supercapacitor capacitance.

Origin of capacitance decay for a flower-like δ-MnO2 aqueous supercapacitor electrode: The quantitative surface and electrochemical analysis

Herein, we report the electrochemical energy storage performance of δ-MnO2 (K-birnessite MnO2) as supercapacitor electrode material in Na2SO4 aqueous electrolyte. The electrode exhibited considerable electrochemical performances due to the fast intercalation/deintercalation reactions of Na+ on the pseudocapacitive MnO2 surface. However, a long-term cyclic stability test of the electrode at a low specific current (1 A g−1) demonstrated a decline in its initial capacitance value to the tune of ~ 21%. To quantify the above discrepancy, the electrochemical intercalation of Na+ ions on the electrode surface was quantitatively studied employing electrochemical impedance spectroscopy, EDAX analysis and X-ray photoelectron spectroscopy. Further, the surface of the electrode was analyzed by performing complete charge and charge/discharge measurements at a low specific current of 0.1 A g−1. These results disclosed that, besides the surface intercalation/deintercalation reactions, some Na+ ions have permanently substituted into the bulk (layer) of δ-MnO2 by replacing the host K ions from the layered nanostructure. Thus, this finding suggests that Na+ ions replaced in the site of K in δ-MnO2 considerably affect the electrochemical properties of the supercapacitor electrode.

Single-Step Preparation of Ultrasmall Iron Oxide-Embedded Carbon Nanotubes on Carbon Cloth with Excellent Superhydrophilicity and Enhanced Supercapacitor Performance.

Nanocomposites consisting of carbon materials and metal oxides are generally preferred as anodes in electrochemical energy storage. However, their low capacitance limits the achieved energy density of supercapacitors (SCs) in aqueous electrolytes. Herein, we propose a rapid combustion strategy to construct a novel electrode architecture-ultrasmall Fe2O3 anchoring on carbon nanotubes (FeO-CNT)-as a superhydrophilic and flexible anode for SCs. In 1 M Na2SO4 aqueous electrolyte, such an FeO-CNT-20 anode presents a high capacitance of 483.4 mF cm-2 (326 F g-1) at 1 mA cm-2. The aqueous asymmetric supercapacitor devices (ASCs) assembled by FeO-CNT-20 and MnO2 present a maximum operating potential of 2.0 V with a high areal energy density of 0.11 mWh cm-2 at a power density of 0.5 mW cm-2. The flexible solid-state ASCs display an energy density of 0.99 mWh cm-3 at 14.3 mW cm-3. The rapidly prepared FeO-CNT not only offers an attractive electrode for SCs but also would open up exciting new avenues to the rational design and large-scale preparation of Fe2O3-based nanocomposites for electrochemical energy storage.