High-performance Electrode Materials Research Articles

Electrospun Mesoporous Ni0.5Zn0.5Fe2O4 - CNT - Hollow Carbon Ternary Composite Nanofibers as High Performance Electrodes for Advanced Symmetric Supercapacitors.

Spinel ferrites have attracted considerable interest in energy storage systems due to their unique magnetic, electrical and catalytic properties. However, they suffer from poor electronic conductivity and low specific capacity. We have addressed this limitation by synthesizing composite hollow carbon nanofibers (HCNF) embedded with nanostructured Nickel Zinc Ferrite (NZF) and Multiwalled carbon nanotubes (CNT), through coaxial electrospinning. These ternary composite nanofibers NZF-CNT-HCNF have a high specific capacity of 833 C g-1 at a current density of 1 A g-1 and have a capacity retention of 90 % after 3000 cycles. Their performance is much better than pure NZF fibers (180 C g-1) or hollow carbon nanofibers (96 C g-1), suggesting synergy between various constituents of the composite. A symmetric supercapacitor fabricated from NZF-CNT-HCNF composite nanofibers (30 % NZF) has a high specific capacity of 302 C g-1 (302 A g-1) at a current density of 1 A g-1 and has a capacity retention of 95 % after 5000 cycles. At the same current density, the device has a high energy density of 39 Whkg-1 and power density of 1000 Wkg-1 at a current density of 1 A g-1. This performance can be attributed to the high specific surface area (776 m2 g-1), mesoporosity (pore size ~4 nm), interconnectedness of the nanofibers and high electrical conductivity of CNTs. These fibers can be used as light-weight high performance electrode materials in advanced energy storage devices.

Nickel-mediated V4O7 as high-performance cathode material for aqueous Zn-ion batteries

Vanadium-based materials are currently favored by researchers due to their multi-structure, which can enhance the steric resistance and electrostatic repulsion during the (de)intercalation process of zinc ions. However, their low conductivity remains an inherent hindrance to their practical application. Therefore, finding a way to adjust the electronic structure of vanadium-based compounds is considered an effective strategy. Presently, we have designed a porous Ni-mediated V4O7, wherein the presence of oxygen defects and heterostructures in V4O7/NiO (Od-NVO-4) substantially improves the diffusion kinetics of ions/electrons and boosts the electrochemical performance. As anticipated, the Zn//V4O7/NiO battery exhibits a high specific capacity (348.6 mAh g−1 at 0.1 A g−1), favorable rate capability (323.8 mAh g−1 at 4 A g−1), and remarkable cycle stability (206.3 mAh g−1 at 2 A g−1 after 2000 cycles). Additionally, the underlying mechanism of electrochemical zinc storage is comprehensively described through electrochemical kinetic analysis and theoretical calculations. These results unambiguously reveal the intrinsic link between the surface/interface structure and electrochemical performance of the cathode, offering a valuable reference for designing high-performance electrode materials.

Electrochemical Performance of MoB/Si3N4 Heterojunction as a Potential Anode Material for Li Ion Batteries.

In response to the current policy of high storage capacity, two-dimensional (2D) materials have revealed promising prospects as high-performance electrode materials. MoB, as a type of such material, is widely regarded as an anode candidate for Li-ion batteries due to its large specific surface area and abundant ion diffusion channels; the long-term cycling stability, however, is poor owing to material pulverization during the cycle. Therefore, MoB/Si3N4 heterojunction in this work is proposed as an anode material, with Si3N4 acting as a skeleton, maintaining the stability of the structure, while retaining the high energy storage properties of MoB as well. In addition, a certain built-in electric field is formed between them, which can play a role in regulating charge transfer, improving the ion transport channel, and accelerating the migration rate. Herein, the structural, electronic, and electrochemical properties are systematically investigated by first-principles calculations; the final results indicate that the heterojunction anode material does indeed have built-in electric fields, which promote the anode material to possess excellent electrical conductivity and outstanding electrochemical property. Meanwhile, the introduction of vacancy defects can bolster the diffusion kinetic performance of ion transport and greatly reduce the diffusion energy barrier of Li ions, which is conducive to the realization of rapid charge and discharge for the Li ion battery. Based on the synergistic effect of two single-component materials, the synthesized anode material displays a high theoretical capacity of 461 mAh/g, and the calculated open-circuit voltage is 0.66 V, within the range of the negative electrode criterion of 0-1 V, which can effectively play a role in preventing the formation of Li dendrites; these properties are comparable to other 2D anode materials as well. Given these intriguing properties, the MoB/Si3N4 heterojunction is an exceptional candidate for advanced LIB high-performance anode materials.

Enhanced electrochemical activity by NiCo-P nano-particles modified Co-MOF nanorods

The design and preparation of high-performance electrode materials are among the most extensively researched topics in supercapacitor studies. By combining the three-dimensional structure and compatibility of cobalt-based metal-organic framework (Co-MOF) with the high redox activity of metal phosphates, a green, efficient, and safe co-precipitation and electro-deposition strategy was employed to fabricate the Co-MOF@NiCo-P heterostructure composite electrode material, with NiCo-P nanoparticles uniformly decorated on the surface of Co-MOF, addressing the issues of limited conductivity of Co-MOF and the tendency of NiCo-P to aggregate when grown in situ on foam nickel. In a three-electrode system, the Co-MOF@NiCo-P electrode exhibits specific capacities of 1389.8 F g−1 at 1 A g−1 and 964.3 F g−1 at 20 A g−1. The assembled Co-MOF@NiCo-P//AC hybrid supercapacitor device demonstrates energy densities of 54.08 Wh kg−1 (22.92 Wh kg−1) and power densities of 825 W kg−1 (8250 W kg−1), showing promising application prospects. This research offers a novel method for developing high-performance electrode materials.

Reduced Graphene Oxide/Silica Based Electrode Material: Synthesis and Characterization

<span lang="EN-US">Developing a Reduced Graphene Oxide (rGO) synthesis method based on rice husk as a composite electrode material with silica has garnered particular attention for designing high-quality electrode materials. This research successfully synthesized rGO-Si material from rice husk-derived activated carbon through a one-step thermal reduction process at 200 °C. This method offers a simple, efficient, cost-effective, and environmentally friendly synthesis approach. The resulting samples' morphology, surface composition, crystal structure, surface area, and pore diameter size were characterized using FE-SEM, EDX, XRD, and SAA-BET. EDX characterization results confirmed the predominance of carbon content in the samples. At the same time, the natural emergence of Si without external addition due to thermal reduction at 200 °C was an intriguing initial finding. The spherical crystal structure of silica between the wrinkled rGO layers was confirmed through FE-SEM and XRD analysis. The synergistic effect between Si and rGO significantly increased the sample's surface area, with a value of 34.17 m<sup>2</sup>/g for the rGO sample before thermal reduction, which increased to 121.24 m<sup>2</sup>/g after the thermal reduction process at 200 °C. This process also positively impacted the reduction in pore size of rGO-Si, with a value decreasing from 9.33 nm before thermal reduction to 4.89 nm after the thermal reduction process. The results of this study demonstrate that rGO-Si synthesized from rice husk-derived activated carbon holds great potential as a high-performance electrode material, combining the advantages of thermal reduction, natural Si content, and increased surface area for diverse applications.</span>

Activated biomass-derived 3-dimensional porous graphene-like carbon for high-performance energy storage electrode materials

This article reports studies on the fabrication of active material for supercapacitor electrodes, from 3D porous graphene-like carbon (GLC), synthesized by carbonization from coffee waste (CW) and tea waste (TW) at 550 °C, followed by thermochemical activation in KOH at 850 °C in a quartz tubular furnace. The microstructure of coffee and tea waste shows the form of micro- and mesopores during carbonization and further chemical activation forms hierarchically highly porous 3D graphene-like carbon. GLC-CW exhibited a higher specific surface area (SSA) of 3486 m2/g according to the Brunauer-Emmett-Teller (BET) method, compared to GLC-TW, which had an SSA of 2407 m2/g. These results highlight the effectiveness of graphene-like carbon derived from coffee and tea waste, demonstrating its potential as a promising material for high-capacity supercapacitors. The electrochemical characteristics of the assembled supercapacitors using GLC-CW and GLC-TW revealed significantly higher specific capacitance values of 214 F/g and 182 F/g respectively, along with cycling stability of 98 % and 95 % during 5000 cycles of charge and discharge at 2 A/g current density. This approach can produce high-performance electrode materials for supercapacitors at a reasonable cost and with easy scalability.

In-situ synthesis AgO/AgNPs composite as binder-free cathode for high-performance aqueous AgO-Al batteries

Aqueous AgO-Al batteries are promising systems due to their ultrahigh specific capacity, energy density, and stable output voltage. However, they still suffer from the low utilization and sluggish kinetics of the cathode. In this study, the binder-free AgO/AgNPs composites were synthesized in-situ using a simple electrodeposition method. Due to the excellent conductivity and rich mesoporous structure of AgO/AgNPs materials, the electron and ion transfer kinetics were enhanced, thereby improving the charge storage performance of the electrode. As expected, the AgO-Al battery with the optimized AgO/AgNPs composite cathode demonstrated excellent rate performance, achieving a high discharge capacity of 325.1 mAh g−1, and a stable operating voltage platform of 1.55 V at the current density of 1000 mA cm−2. The maximum energy and power density were 687 Wh kg−1 and 6.2 kW kg−1, respectively. This work presents an effective strategy for designing high-performance AgO electrode materials for AgO-Al batteries.

In situ growth of MnO2 on graphitized cellulose nanocrystal: A novel coaxial heterostructures with unblocked conductive networks as advanced electrode materials for supercapacitor

Manganese dioxide (MnO2) with high theoretical capacitance and natural abundance has attracted great attention but is still challenging for use in supercapacitors, due to the limited conductivity and lower electron and ion migration. Here, a facile in situ growth strategy is developed to prepare heterostructural graphitized cellulose nanocrystal (GCNC)/MnO2 with unblocked conductive networks through a hydrothermal reaction. The GCNC with highly ordered graphitic carbon layers as conductive support framework solves the agglomeration problem of MnO2 and increases effective specific surface areas in contact with electrolyte ions. Meanwhile, the stable connection of MnOC covalent bonds enhances the interface bonding, which effectively reduces the contact resistance at the interface of heterostructural GCNC/MnO2 and enhances the interface firmness. The resulting GCNC/MnO2 electrode shows a remarkable specific capacitance of 528.2 F g−1 at 0.5 A g−1. Furthermore, the symmetric supercapacitor based on GCNC/MnO2-15 mM exhibits high rate capability and excellent cycle stability of 100 % capacitance retention after 3000 cycles. This work provides a new path to designing high performance electrode material for sustainable energy technologies.

One step glow-discharge electrolysis-based preparation of Al doped Ni-Co layered double hydroxide/ graphene oxide as supercapacitor electrode material

Nickel-cobalt layered double hydroxides (LDHs) are promising materials for supercapacitor electrodes; however, they face challenges in terms of cycling stability and rate capability owing to agglomeration and low conductivity. In this study, Ni(III)CoAlx-LDH/GO with an extended layer spacing and excellent electronic conductivity was synthesized by one-step glow discharge electrolysis. A nickel–cobalt alloy was used as the anode, a graphite rod as the cathode, and sodium chloride as the electrolyte. In addition, incorporating an appropriate amount of aluminum chloride into the electrolyte can alter the microstructure of the electrode material, leading to enhanced electrochemical performance. Ni(III)CoAl0.2-LDH/GO, synthesized using 0.2 g AlCl3, demonstrated exceptional electrochemical performance of 1014C g−1 at 2 A/g. At a current density of 5 A/g, the capacitance retention rate was 85.3 % after 10,000 cycles, indicating strong cyclic stability. Moreover, an asymmetric supercapacitor built with Ni(III)CoAl0.2-LDH/GO as the anode and commercial activated carbon as the cathode achieved a specific capacitance of 146.2F/g at a current density of 1 A/g. This device demonstrated outstanding circular stability, retaining 85.07 % of its capacitance after 10,000 cycles. In addition, the device achieves relatively high energy density and power density (energy density of 66.63 Wh kg−1 at a power density of 1022.23 W kg−1). This study introduces a novel synthesis method for the preparation of high-performance electrode materials aimed at advancing energy storage devices.

Rapid and controllable microwave synthesis of nickel cobalt sulfide electrodes for high-performance asymmetric supercapacitors

The efficient and controllable synthesis method of high-performance energy storage electrode materials is crucial for advancing the development of energy storage technologies. Herein, by leveraging microwave heating technology in the sulfidation of nickel cobalt MOF, we effectively enhanced the efficiency of the synthesis process. Notably, sulfidation time emerged as a pivotal factor in tuning the crystalline phase structure and conductive properties of the material, leading to the successful development of NCS2 electrode material with a unique structure through optimized sulfidation conditions. Electrochemical performance tests of the NCS2 material revealed exceptional results; it exhibited a specific capacity of 1311 Fg[Formula: see text] at a current density of 1 Ag[Formula: see text] and retained 73.4% of its initial capacity when the current density increased to 10 Ag[Formula: see text], demonstrating outstanding rate performance. The composite NCS2//AC supercapacitor exhibits an energy density of 24.2 Whkg[Formula: see text] at power density of 800 Wkg[Formula: see text], even though after 1000 consecutive charge-discharge cycles, the capacity retention rate remained high at 77.1%, validating the exceptional stability and reliability of the NCS2 material during cycling. This work employs microwave sulfidation for the rapid and controlled synthesis of nickel cobalt sulfides, providing a green and efficient synthetic strategy for metal sulfide active materials.

Synergistic effects of MXene and Co3O4 in composite electrodes: High-performance energy storage solutions

The development of high-performance electrode materials is crucial for advancing supercapacitor technology. The two-dimensional layered structure of MXene (Ti3C2Tx) presents high conductivity, abundant surface functional groups and accessible ion interaction between layers. However, the MXene suffers from the layer aggregation. To overcome this issue, we synthesized a composite material combining MXene with cobalt oxide (Co3O4) to enhance electrochemical performance in supercapacitors. MXene’s two-dimensional layered structure, high conductivity, and abundant surface functional groups allow for efficient ion intercalation, while Co3O4 contributes high theoretical capacitance and rich oxidation states. The resulted MXene/Co3O4 composite exhibits an impressive areal capacitance of 6.456F/cm2 at a current density of 3 mA/cm2, maintaining 90.52 % capacitance retention at 30 mA/cm2, and 81.37 % capacity after 5000 charge–discharge cycles. Additionally, the asymmetric supercapacitor (ASC) device fabricated using the MXene/Co3O4 composite achieves a power density of 6.41 mW/cm2 at an energy density of 0.37 mWh/cm2, with 82.3 % capacitance retention after 5000 cycles. These results demonstrate that the MXene/Co3O4 composite material is a promising candidate for high-performance supercapacitors, offering significant improvements in rate capability and long-term cycling stability.

Potentiostatic strengthening tactic for constructing defects rich battery-type nickel-cobalt selenate for enhancing energy storage

Reasonably designing transition metal composite electrode materials with high defect levels can overcome the disadvantage of relatively moderate energy density in supercapacitors. Herein, an appealing potentiostatic strengthening tactic for constructing defect rich electrode materials is proposed. Notably, the densely nanoneedle-like nickel–cobalt-based selenide (NCSe) undergoes in situ electrochemical reconstruction after potentiostatic modification, with significant changes in morphology, structure, and composition. The highly active materials NCSe-E, transforming from weakly active substances NCSe mentioned above, are rich in oxygen vacancies and a large number of exposed active sites. Subsequently, it is compared with typical cyclic voltammetry (CV) scanning techniques and the phase evolution process is explored using in situ and ex situ methods. The results show that the plentiful defects promote the adsorption/desorption of OH–, leading to superior rate performance of NCSe-E, with a specific capacity of 3830 mC cm−2 at 1 mA cm−2 and capacity retention of 72.0 % at 50 mA cm−2. Kinetic analysis and theoretical calculations further reveal that oxygen vacancies enhance ions adsorption energy in NCSe-E and promote charge transfer during charging/discharging processes. This work indicates that the novel defect construction strategy provides some new insights for achieving reasonable regulation of high-performance transition metal compound electrode materials.

Boosting supercapacitive performance of SnS2 via trace Pb doping

High-performance electrode materials are crucial for enhancing the performance of supercapacitors. Among various candidates, pseudo-capacitive SnS2 is a promising one due to its high specific capacitance, earth-abundance, nontoxicity as well as low-cost. However, its actual electrochemical performance is restricted owing to the poor intrinsic conductivity and current fabrication processes on improving the conductivity are usually complicated. In this study, based on first-principles calculations, Pb doping is introduced to enhance the conductivity of SnS2. Pb-doped SnS2 nanosheets are synthesized via a simple one-step hydrothermal method. With trace Pb doping (Pbo.o1SnS2), an impressive 4-order-of-magnitude increase in conductivity was achieved compared to pristine SnS2. Furthermore, Pb-doped SnS2 nanosheets exhibit a superior mass-specific capacitance of 533.7 F g−1 at 50 mV s−1 and excellent long-term capacitance retention of 90.2 % over 100,000 cycles at 5 A g−1. This study presents a simple and effective approach to enhancing the supercapacitor performance of SnS2 and advances the practical applications of electrochemical energy storage devices based on 2D materials.

Fluorinated reduced graphene oxide nanosheets for symmetric supercapacitor device performance

This study explores the potential of using spent lithium-ion battery anodes (graphite) for fabricating symmetric energy devices through a simple regeneration process. Specifically, the use of fluorine-doped reduced graphene oxide (RGO) nanosheets derived from waste batteries as the basis for a symmetric supercapacitor (SC) device is investigated. To enhance the electrochemical energy storage capabilities, a facile hydrothermal technique is employed to synthesize fluorinated graphene. Fluorination of the graphene sheets is successfully realized, as confirmed by the presence of boron with a 2.94 at.% fluorine-doped level, according to the Energy dispersive spectroscopy (EDS) spectrum analysis. Electrochemical analysis of the F-RGO electrode performance consistent with electric double-layer capacitance. Moreover, with a three-electrode system, the F-RGO electrode achieves a maximum specific capacitance of 207F/g under a current density of 1 A/g. A two-electrode symmetric device employing F-RGO exhibits a specific capacitance of 54F/g at 1 A/g. Furthermore, electrochemical impedance measurements demonstrate low charge transfer resistance (Rct) values, specifically 8.63 Ω for F-RGO, signifying improved electrochemical performance. Thus, fluorine atomic doping in RGO nanosheets contributes to the improvements of the specific capacitance and overall superior electrochemical performance of F-RGO, and F-RGO is a highly electrochemical active material for high-performance energy storage electrodes for SCs.

Hierarchical porous MXene film with diffusion path optimization for supercapacitor

MXenes have immense potential in electrochemical energy storage owing to their outstanding physicochemical properties such as their oxygen-containing groups that impart additional pseudocapacitance to acidic electrolytes. However, during electrode assembly, MXene nanosheets undergo restacking because of hydrogen bonding and van der Waals forces, which causes electrolyte ions to traverse long diffusion pathways between the long and narrow nanosheets. Exploiting the oxidative properties of Ti3C2Tx, a hierarchical porous MXene film with micro-, meso- and macroporous structures was successfully prepared using a simple hydrothermal oxidation and etching process to create micro- and mesoporous structures, followed by ice templating to prepare three-dimensional (3D) linked macroporous structures. Because these hierarchical pores have synergistic effects on electrochemical activity and electrolyte ion diffusion, the film attained a specific capacitance of 539F/g at a current density of 2 A/g when it was used as a supercapacitor electrode, which corresponds to one of the highest values reported for MXene-based electrodes. The film retained 83% of its specific capacitance when the current density was increased to 40 A/g, and exhibited excellent cycling stability. By using this multi-porous MXene design, synergistic improvement in ion diffusion was successfully realized and thus a new strategy to prepare high-performance supercapacitor electrode materials was developed.

Ag-doped MgCo2O4/MXene composite: Tailoring the electrochemical properties via 2D layered material for next generation supercapacitor study

The major concern of the modern era is to conserve and store energy for future use because of the continuous depletion of natural resources. Spinel cobaltites have attracted a lot of attention to be studied in the energy storage and conversion arena because of their prospective applications and excellent electrochemical performance. Achieving excellent chemo-mechanically robust electrode materials requires creative structural design and effective multicomponent strategy implementation. Herein, MgCo2O4 (MC) and Ag-MgCo2O4 (AMC) were fabricated by hydrothermal treatment. Further, Ag-MgCo2O4 (AMC) coupling with MXene sheets was accomplished by ultrasonication treatment. After structural, morphological, functional, and compositional analyses, prepared materials were studied for supercapacitor measurements. AMC/MXene exhibited remarkable outcomes because of Ag ions insertion into the spinel oxide structure, providing electron transport paths by creating voids and interfacial contact between the electrolyte and available active sites, and 2D MXene layers boosting the transportation of ions during the charging and discharging stages. The specific capacitance at 1 Ag−1 was found to be 1722 Fg−1 for AMC/MXene. The bulk (solution) resistance Rs was found to be the lowest 0.63 Ω for AMC/MXene among other fabricated materials in this study. Hence, developing AMC/MXene offers an advanced method to build high-performance 2D electrode materials with hybrid structures for energy storage applications.

A self-supporting nanoflower-like film of 3D walnut shell derived carbon/NiCo2S4 for supercapacitors and zinc-ion batteries with high energy density

Nanocomposites with special structures can generally provide more efficient electron and ion transfer kinetics during electrochemical charge storage, resulting in satisfactory energy densities. Herein, we adopted a simple hydrothermal method to prepare a nanoflower-like NiCo2S4 growing on hierarchical porous N, O co-doped walnut shell-derived carbon (10-WSC-N/O@NiCo2S4). Metal ions (Ni2+, Co2+) enhanced the active site to obtain better electrochemical activity, as well as the porous carbon framework helped achieve better ion transport and electron conduction. Importantly, 10-WSC-N/O@NiCo2S4 exhibits 1176 F g−1 at 0.5 A g−1, the prepared 10-WSC-N/O@NiCo2S4//WSC-N/O displays a remarkable energy density of 68.6 Wh kg−1 at 375 W kg−1 and only decreases a 12 % in capacitance after 8000 cycles at 3.0 A g−1. Additionally, the 10-N/O@NiCo2S4//Zn device achieves a high energy density of 88.54 Wh kg−1 at 750 W kg−1. Overall, this work provides an efficient strategy for fabricating high-performance electrode materials.

High-performance NF-loaded F-NiFe-LDH/rGO nanoflower/nanosheet composite electrode material achieving enhanced specific capacitance and energy density for supercapacitor

High-performance nanostructured F-NiFe-LDH/rGO composite electrode materials with F-NiFe-LDH nanoflowers and rGO nanosheets are synthesized in a controlled hydrothermal method by leveraging the strong synergistic effects between the components, enabling the construction of F-NiFe-LDH/rGO//AC asymmetric supercapacitors. The incorporation of rGO significantly enhances electron transport, resulting in an exceptional specific capacitance of 2860 F g−1 at a current density of 1 A g−1, with a remarkable capacity retention of 102 % after 1000 cycles. This represents a notable improvement in electrochemical energy storage, with surface-controlled capacitance contributing more in alkaline electrolytes for F-NiFe-LDH/rGO composite compared to F-NiFe-LDH alone. The asymmetric supercapacitor device exhibits a specific capacitance of 354 F g−1 at 1 A g−1, maintaining 92.31 % of its initial capacitance after 1000 charge/discharge cycles at 5 A g−1, and achieves an impressive energy density of 110 Wh kg−1 at 1 A g−1. The innovation of this work lies in the controllable preparation of nanostructured F-NiFe-LDH-rGO supercapacitor electrode material with enhanced specific capacitance and energy density by the synergistic effect between F-NiFe-LDH and rGO. This work offers a solid foundation for creating high-performance supercapacitor electrode materials and devices for energy storage applications.

Exploring the Electrochemical Superiority of V2O5/TiO2@Ti3C2-MXene Hybrid Nanostructures for Enhanced Lithium-Ion Battery Performance.

The use of vanadium(V)-based materials as electrode materials in electrochemical energy storage (EES) devices is promising due to their structural and chemical variety, abundance, and low cost. V-based materials with a layered structure and high multielectron transfer in the redox reaction have been actively explored for energy storage. Our current work presents the structural and electrochemical properties of a vanadium-based composite with TiO2@Ti3C2 MXene, referred to as VM. This composite is obtained through the in situ thermal decomposition of the VO2(OH)/Ti3C2mixture, which is achieved by solution mixing and drying. The material structure is confirmed using various characterization tools, which establish an orthorhombic V2O5 nanostructure compositing with nanocrystalline TiO2@Ti3C2. VM with 5 wt % MXene, referred to as VM5, can achieve 460 mAhg-1 at a current density of 0.1 Ag1- and 290 mAhg-1 at 1 Ag1-, with an average coulombic efficiency of 98.5%. The presence of the V2O5/TiO2 (nanocrystals) heterojunction attached with Ti3C2 sheets contributed to reduced charge transfer resistance. The cyclic stability shows a capacity retention of 62% over 500 cycles at 1 Ag1- (4C rate, where 1C equals 0.25 Ag1-) with a 0.22 capacity drop with each cycle. Dunn's approach to examining the charge storage mechanism demonstrates 72% contribution of the surface-dominant capacitive process and 28% of the diffusion-controlled intercalation process at 0.4 mVs-1, suggesting a potential high-performance pseudocapacitive hybrid electrode material for lithium-ion batteries.

Synthesis of rice husk derived porous carbon as low-cost and high-performance electrode material for supercapacitors

Porous carbon electrode materials derived from agricultural by-products of food processing have attracted widespread interest. Rice husk (RH) is a promising raw material owing to its abundance and low price. In this study, a supercapacitor electrode was prepared by using recycled RH and secondarily activated with ZnCl2 to enhance its electrochemical energy storage performance. RH carbonized at the optimum temperature (i.e., 800 °C) was activated to synthesize RH-800-X (X = 1, 2, 3, 4, or 5, representing the mass ratio of ZnCl2 to RH-800). Sample RH-800-3 exhibited the highest specific surface area (1348.29 m2 g−1) and mesoporous pore volume (0.8375 cm3 g−1) among the samples. In a three-electrode system, the prepared electrodes delivered a high specific capacitance (242 F g−1 at 0.3 A g−1 in 6 M KOH solution). Furthermore, the capacitance retention of RH-800-3 remained at 99.9 % after 17,000 charge/discharge cycles. The results demonstrate the excellent capacitive behavior and superior electrochemical performance of RH-800-3. In addition, symmetrical capacitors prepared using RH-800-3 have an energy density of up to 101 Wh kg−1 at a power density of 900 W kg−1. Therefore, this study presents a simple and effective method for preparing a high-performance electrode material from biomass-derived porous carbon (i.e., recycled RH) and offers a new perspective for the efficient utilization of waste biomass resources.