Microsphere Electrode Research Articles

Controlled morphology significantly enhances electrochemical performance of LaNiO3-NiO anodes for Li-ion batteries

Traditional graphite anodes have become increasingly reliable in lithium-ion battery applications. However, there is an urgent need to overcome their limitations, such as the low theoretical capacity and less favorable rate performance. Recently, perovskite-type oxides have garnered increasing attentions as anodes owing to their advantages of capacity, rate performance, lifespan, and safety. In our previous study, the electrochemical performance of LaNiO3-NiO nanoparticles was enhanced compared to those of LaNiO3, primarily thanks to the synergistic effect of the biscuit-shaped LaNiO3-NiO and graphene-like layered g-C3N4. Morphology modulation is an important method for enhancing the performance of the anode materials. Based on this concept, we designed two kinds of LaNiO3-NiO with different morphologies (micro-sphere and micro-flower), and tested their physical and electrochemical properties. The discharge capacity of the LaNiO3-NiO micro-sphere anode was 714.5 mAh g−1 after 950 cycles at 1000 mA g−1, which is significantly higher than those of LaNiO3-NiO micro-flower and nanoparticle. However, the LaNiO3-NiO Micro-flower anode maintains a reversible capacity of 144.2 mAh g−1 at 10.0 A g−1, which is higher than that of the LaNiO3-NiO Micro-sphere electrode (125.8 mAh g−1). It was found that the morphology modification endows the electrodes possessing their own outstanding electrochemical properties.

Biomass-based controllable morphology of carbon microspheres with multi-layer hollow structure for superior performance in supercapacitors

The electrochemical properties of corn starch (CS)-based hydrothermal carbon microsphere (CMS) electrode materials for supercapacitor are closely related to their structures. Herein, cetyltrimethyl ammonium bromide (CTAB) was used as a soft template to form the corn starch (CS)-based carbon microspheres with radial hollow structure in the inner and middle layers by hydrothermal and sol-gel method. Due to the introduction of multi-layer hollow structure of carbon microsphere, more micropores were produced during CO2 activation, which increased the specific surface area and improved the capacitance performance. Compared to commercial activated carbon, the four different morphologies of corn starch CMS had better electrochemical performances. Consequently, the proposed CO2–(CTAB)-CS-CS exhibits a high discharge specific capacitance of 242.5F/g at 1 A/g in three-electrode system with 6 M KOH electrolyte, better than commercial activated carbon with 208.5F/g. Moreover, excellent stability is achieved for CO2–(CTAB)-CS-CS with approximately 97.14 % retention of the initial specific capacitance value after 10,000 cycles at a current density of 2 A/g, while the commercial activated carbon has 86.96 % retention. This implies that the corn starch-based multilayer hollow CMS could be a promising electrode material for high-performance supercapacitors.

Ultrathin VO2(B) nanosheets assembled into 3D micro/nano structured flower-like microspheres for high-performance cathode materials of Li-ion batteries

Vanadium oxides, as a potential cathode material for lithium-ion batteries (LIBs), have received extensive attention from researchers owing to their significant advantages in terms of theoretical specific capacity, energy density, and power density. However, vanadium oxides lead to irreversible decay of specific capacity during cycling for reasons such as poor structural stability and electrical conductivity. In this paper, the flower-like VO2(B) microsphere assembled from ultrathin nanosheets was synthesized successfully by hydrothermal method, and their effects on the morphology as well as the phase of VO2(B) are investigated by varying the hydrothermal reaction time and the concentration of oxalic acid. The results show that the flower-like VO2(B) microsphere electrode material not only provides a larger active area, but also offers a faster lithium ion diffusion rate and a shorter charge transport path, resulting in a high reversible capacity, outstanding rate performance, and excellent long cycle life. The flower-like VO2(B) microsphere electrode exhibited a first discharge specific capacity of 282.9 mAh/g (at a current density of 0.1 A/g) and a capacity retention of 80.7 % after 50 cycles. In addition, the electrode material shows a first discharge specific capacity of 209.6 mAh/g at a high current density (1 A/g) and a capacity retention rate of 83.1 % after 200 cycles. Consequently, the VO2(B) provides great development potential as a cathode material for next-generation LIBs.

Surface design and engineering of ZnMn2O4/RGO composites for highly stable supercapacitor devices

The manipulation of phase and morphology of metal oxides by controlled engineering is considered to be a significant approach for enhancing electrochemical characteristics. The development of composite materials that are both highly efficient and cost-effective is crucial in the context of supercapacitors. A hydrothermal route is opted to fabricate ZnMn2O4/RGO microsphere electrodes. The control of process parameters during the synthesis and subsequent annealing allows for the development of microspheres exhibiting unique topographies of the surface. The incorporation of RGO into the composites has the potential to enhance conductivity, hence improving the overall utilization of the material. The ZnMn2O4/RGO composites exhibited the specific capacitances of 628, 545, 488, 446, 380 and 364 F g−1 at current densities of 1, 2,3,5,10 and 20 A g−1, respectively. Furthermore, the results demonstrated exceptional rate capability as the material retained 58 % of its initial capacitance even under a high current density. In addition, it retained a capacitance of 95.2 % even after 10,000 cycles at 1 A g−1. Furthermore, ZnMn2O4/RGO@ASC device displayed a reasonable specific capacitance of 128.7 F g−1 at 1.5 A g−1 and retained a capacitance of 83.9 % for 5000 cycles at 5 A g−1. The ZnMn2O4/RGO@ASC device had the energy density of 40.2 W h kg−1 at a power density of 1125 W/ kg. As a result, developed supercapacitor devices are preferred for use in portable electronics and industrial applications.

The synergistic effect of carbon and polypyrrole co-coating enhances the electrochemical performance of TiO2 microspheres for high-performance supercapacitors

Carbon and polypyrrole co-coated TiO2 microspheres (TiO2@NC@PPy) electrodes were synthesized by hydrothermal, coating and potentiostatic deposition. The carbon coating layer and polypyrrole layer can significantly improve the conductivity of the electrode, and the unique hierarchical porous microsphere structure can adsorb PPy, preventing its structural decomposition and volume expansion while enhancing the cycle stability. Therefore, the areal capacitance was increased from 2.26 mF/cm2 to 389.76 mF/cm2 at a current density of 2 mA/cm2, retaining 73.34% capacity after 2000 cycles.

High-Power-Density Thermoelectrochemical Cell Based on Ni/NiO Nanostructured Microsphere Electrodes with Alkaline Electrolyte.

Effective low-grade waste heat harvesting and its conversion into electric energy by the means of thermoelectrochemical cells (TECs) are a strong theme in the field of renewable energy investigation. Despite considerable scientific research, TECs have not yet been practically applied due to the high cost of electrode materials and low effectiveness levels. A large hypothetical Seebeck coefficient allow the harvest of the low-grade waste heat and, particularly, to use TECs for collecting human body heat. This paper demonstrates the investigation of estimated hypothetical Seebeck coefficient dependency on KOH electrolyte concentration for TECs with hollow nanostructured Ni/NiO microsphere electrodes. It proposes a thermoelectrochemical cell with power density of 1.72 W·m-2 and describes the chemistry of electrodes and near-electrode space. Also, the paper demonstrates a decrease in charge transfer resistance from 3.5 to 0.52 Ω and a decrease in capacitive behavior with increasing electrolyte concentration due to diffusion effects.

Achieving high energy density in supercapattery by employing CuFe2O4 microsheets and Bi2O3 microspheres

In this work, we report a high energy density supercapattery device were employing hydrothermally synthesized two-dimensional CuFe2O4 microsheets as cathode and synthesized redox-active Bi2O3 microsphere as the anode. The charge storage characteristics of the electrode materials were detailed studied. Herein, the 2D-CuFe2O4 microsheet-based positive electrode showed an enhanced areal capacitance and cyclic stability of 1279 mF cm−2 and 98% after 5000 GCD cycles, respectively. Moreover, Bi2O3 microspheres electrode material delivered a favourable capacitance of 1368.25 mF cm−2 and noticeable cyclic stability of 81% even after 3000 GCD counts. Both the positive and negative electrodes showed excellent electrochemical performance owing to their vast electrochemical active sites, which induce fast electron/ion transportation. Furthermore, a supercapattery device was assembled employing CuFe2O4/Ni-foam as cathode and Bi2O3/Ni-foam as anode for evaluating its real-time performance. This supercapattery device delivers a high energy density and power density of 67.55 µ Wh cm−2 and 3200 µ W cm−2, respectively, in the optimal 1.6 V cell voltage. Moreover, the device showed a good cycling stability value of 87.4% with noticeable coulombic efficiency of 99.2% with the 10,000 cycles. These electrochemical results suggest that the assembled device was esteemed the highly beneficial energy storage system.

Ultrathin V6O13 nanosheets assembled into 3D micro/nano structured flower-like microspheres for high-performance cathode materials of Li-ion batteries

Benefiting from its unique high theoretical capacity and energy density, V6O13 is considered an outstanding cathode candidate. Nevertheless, the lithium ions will form LixV6O13 when embedded in V6O13, resulting in volume expansion and crystal structure instability. For that reason, the construction of three-dimensional nanostructures is an awfully serviceable method to resolve the above problems. Herein, we adopt a green and convenient hydrothermal method to synthesize three-dimensional microsphere structure composed of nanoflakes, and flower-like V6O13 microspheres are synthesized by adjusting the concentration of nitric acid (HNO3). Meanwhile, the formation mechanism of flower-like V6O13 microspheres is investigated by controlling the hydrothermal reaction time and the concentration of HNO3. As a lithium-ion cathode material, flower-like V6O13 microspheres show an initial discharge specific capacity of up to 368.1 mAh/g at a current density of 0.1 A/g. There was still a discharge specific capacity of up to 313.1 mAh/g after 50 charge/discharge cycles, with a capacity retention rate of 85.1%. The flower-like V6O13 microsphere electrode also combines an excellent rate performance with a satisfactory cycling stability, which achieves a cycle retention rate of 80.2% even after 200 charge/discharge cycles, and an initial discharge specific capacity of 216.9 mA/g even at a high current density of 1 A/g. The results show that, benefitting from its large specific surface area and robust three-dimensional structure, the flower-like V6O13 microsphere electrode material exhibits excellent cycling performance, and the lithium-ion batteries which use it as the cathode material perform equally well in terms of high capacity and high rate.

Rapid synthesis of nickel‑copper phosphate electrode by microwave-assisted hydrothermal reaction for supercapattery

This study reports the fabrication of binder-free nickel‑copper phosphate (NCP) battery-type electrode via microwave-assisted hydrothermal method for the first time. This fabrication method involved microwave heating which significantly reduced the reaction time compared to the conventional hydrothermal method. The NCP electrodes with different precursor ratios (Ni:Cu of 4:0, 3:1, 1:1, 1:3, and 0:4) were fabricated at 90 °C for 12.5 min. Among all NCP binder-free electrodes, Ni3-Cu-P electrode (Ni:Cu of 3:1) exhibited superior electrochemical performance by showing the highest specific capacity of 1030.8 C/g and areal capacity of 0.72 C/cm2 at 3 A/g, and the lowest charge transfer (25.9 Ω) and ion diffusion resistances. These can be explained by the fact that Ni3-Cu-P electrode had a small-sized microsphere electrode material with an amorphous structure deposited on the nickel foam. The small-sized microsphere provided a larger surface area for faradaic reaction. Besides, the amorphous structure offered more electrochemical sites for faradaic reaction. Therefore, it was selected as the battery-type electrode for supercapattery. The Ni3-Cu-P//AC supercapattery delivered a higher energy density of 51.6 Wh/kg at 2.25 kW/kg power density, and outstanding stability with 91.3 % capacity retention after 3000 cycles.

Role of vanadium ions substitution on spinel MnCo2O4 towards enhanced electrocatalytic activity for hydrogen generation

Improving efficient electrocatalysts (ECs) for hydrogen generation through water splitting is of significant interest in tackling the upcoming energy crisis. Sustainable hydrogen generation is the primary prerequisite to realizing the future hydrogen economy. This work examines the electrocatalytic activity of hydrothermally prepared vanadium doped MnCo spinel oxide microspheres (MC), MnVxCo2−xO4 (Vx-MnCo MC, where x ≤ 0.4) in the HER (hydrogen evolution reaction) process. Magnetization measurements demonstrated a paramagnetic (at high temperatures) to a ferrimagnetic (at low temperatures) transition below the Curie temperature (Tc) in all the samples. The magnetization is found to intensify with the rising vanadium content of MCs. The optimized catalyst Vx-MnCo MCs (x = 0.3) outperformed other prepared ECs with a Tafel slope of 84 mV/dec, a low onset potential of 78.9 mV, and a low overpotential of 85.9 mV at a current density of 10 mA/cm2, respectively. The significantly improved HER performance of hydrothermally synthesized Vx-MnCo MCs (x = 0.3) is principally attributable to many exposed active sites, accelerated electron transport at the EC/electrolyte interface, and remarkable electron spectroscopy for chemical analysis (ECSA) value was found ~ 11.4 cm2. Moreover, the Vx-MnCo MCs (x = 0.3) electrode exhibited outstanding electrocatalytic stability after exposure to 1000 cyclic voltametric cycles and 36 h of chronoamperometric testing. Our results suggest a feasible route for developing earth-abundant transition metal oxide-based EC as a superior electrode for future water electrolysis applications.

Rational construction of porous marigold flower-like nickel molybdenum phosphates via ion exchange for high-performance long-lasting hybrid supercapacitors

The assembled hybrid supercapacitor device using the urea-based nickel molybdenum phosphate nanopetals embedded microspheres electrode exhibits outstanding long-term cycling stability, demonstrating its practical applications.

Controllable synthesis of flower-like MnV2O6·2H2O microsphere as electrode for advanced hybrid supercapacitors

Exploring novel electrode materials with rational morphology and structure is critical for the development of supercapacitors. In this paper, flower-like MnV2O6·2H2O microspheres have been controllably synthesized through a methanol and ethylene glycol assisted solvothermal method. Especially, the methanol solvent (structure-directing agent) induces the assembly process of the recrystallized nanosheets into flower-like microspheres, and the assistance of ethylene glycol (chelating agent) can effectively reduce the microsphere size through the strong complexation between metal ions and ethylene glycol. Benefiting from the unique three-dimensional (3D) hierarchical porous structure, the flower-like MnV2O6·2H2O microsphere electrode has an outstanding charge capacity (374.1 C·g−1 at 1 A·g−1), good rate capability, and excellent electrochemical stability (92.7 % capacity retention after 10,000 cycles). After being assembled into supercapacitor, the fabricated MnV2O6·2H2O//AC device exhibits a superior energy density of 35.7 Wh·kg−1 at the power density of 571.7 W·kg−1. These excellent properties demonstrate its potential application prospect in supercapacitor.

Aqueous Rechargeable Zn/ZnO Battery Based on Deposition/Dissolution Chemistry.

Recently, a novel electrochemical regulation associated with a deposition/dissolution reaction on an electrode surface has been proven to show superiority in large-scale energy storage systems (ESSs). Hence, in the search for high-performance electrodes showcasing these novel regulations, we utilized a low-cost ZnO microsphere electrode to construct aqueous rechargeable batteries (ARBs) that supplied a harvestable and storable charge through electrochemical deposition/dissolution via a reversible manganese oxidation reaction (MOR)/manganese reduction reaction (MRR), respectively, induced by the inherent formation/dissolution of zinc basic sulfate in a mild aqueous electrolyte solution containing 2 M ZnSO4 and 0.2 M MnSO4.

Battery-like Supercapacitor of Graphene Supported 3D BiOBr Hierarchical Microspheres Electrode Prepared Using Solvothermal Method

Recent reports have proposed battery-like materials as the relevant bridal material between pseudocapacitors and battery materials. Such electrode materials have been widely used as electrodes in hybrid supercapacitors. From this perspective, graphene-supported 3D BiOBr hierarchical microspheres electrode materials were developed for hybrid supercapacitors in 6 M KOH electrolyte. The 2D/3D of graphene/BiOBr achieves the maximum specific capacity of 435.1 C/g at a current density of 0.5 A/g. It was found that the coulombic efficiency of the electrode was 98.6% after 1000 cycles. Using these electrodes, we have successfully fabricated an asymmetric supercapacitor device similar to a hybrid battery, which has a significant energy density of 32.5 Wh/kg at 8700 W/kg and 124.8 F/g at 0.5 A/g. Excellent capacitance, with remarkable cycle stability and a retention rate of 95.3% after 2000 cycles at 8 A/g. Due to the well-designed electrode materials, battery-like supercapacitors exhibit excellent electrochemical performance and are a source of inspiration for other energy storage devices.

Design of MoS2/NC/MnO2 hollow microsphere electrode for high performance supercapacitors

Design of MoS2/NC/MnO2 hollow microsphere electrode for high performance supercapacitors

Micron-sized NiMn-glycerate solid spheres as cathode materials for all-solid-state asymmetric supercapacitor with superior energy density and cycling life

• NiMn-glycerate microspheres as cathode materials for all-solid-state supercapacitor. • The bimetallic synergistic effect under optimum Ni/Mn ratio improve kinetics. • Micron-sized solid spheres help to keep stable structure during the long cycles. • The large interlayer spacing of metal-glycerate conduce to complete reactions. • Amorphous structure provides more active sites and accelerates charge transfer. Nowadays, it is a great challenge to develop electrode materials with microstructure exhibiting good electrochemical performances. There is poor adhesion between nano-electrode materials and conducting substrate, because large specific surface area causes serious aggregation and uneven coating, limiting the practical application of high performance nano-electrode materials. In this work, micron-sized NiMn-glycerate (NiMn-Gly) solid spheres were synthesized via a facile solvothermal method as cathode material of supercapacitor. By optimizing Ni/Mn ratio and designing amorphous structure, NiMn-Gly microspheres electrode delivers a specific capacitance of 719C g −1 at the current density of 1.0 A g −1 . Furthermore, an all-solid-state asymmetric supercapacitor assembled by NiMn-Gly microspheres and activated carbon exhibits a maximum energy density of 54.4 Wh kg −1 at 800 W kg −1 and achieves outstanding cycling stability (100%, 20,000 cycles, 10 A g −1 ). Two devices connected in series can light up a blue LED bulb and keep it bright for more than 15 min. Hence, we successfully prepared micron-sized electrode material with excellent electrochemical performances which may be a breakthrough for the practical application of supercapacitors.

Monitoring the Degree of Comfort of Shoes In-Motion Using Triboelectric Pressure Sensors with an Ultrawide Detection Range.

Shoes play an important role in sports and human daily life. Here, an in-shoe sensor pad (ISSP) attached to the vamp lining is based on a triboelectric nanogenerator (TENG) for monitoring the real-time stress distribution on the top side of a foot. Each sensor unit on this ISSP is an air-capsule TENG (AC-TENG) consisting of activated carbon/polyurethane (AC/PU) and microsphere array electrodes. The detection range of each AC-TENG reaches 7.27 MPa, which is enough for monitoring the pressure change during different sports. This multifunctional ISSP can realize many typical functions of conventional smart shoes, including step counting and human-machine interaction. Moreover, it can also reveal special information, including the fitness of shoes, the stress concentration on toes, and the in-motion comfort degree. The signal processing and data transmission modules in the system have a hybrid power supply with wireless power transfer, while the real-time information about feet can be observed on a cell phone. Hence, this ISSP provides a potential approach to study the feet motion and comfort degree of shoes in long-term operations, which can guide both athlete training and the customized design of shoes.

Oxygen vacancy inducing phase transition during charge storage in MnOx@rGO supercapacitor electrode

Herein, in-situ Raman and electrochemical quartz crystal microbalance techniques combined with density functional theory (DFT) calculations are adopted to prove the charge storage mechanism for high-stability MnOx@graphene microspheres electrode in alkaline electrolyte (KOH). The results reveal that the layered MnO2 phase gradually transformed into the spinel Mn3O4 phase in the process of discharging, accompanied by the insertion of potassium ions. Moreover, the Mn-O bonds length near the potassium ions in [MnO6] octahedral structure becomes longer, while the long unstable Mn-O bonds tend to lose oxygen and create oxygen vacancies, which further transforms the layered structure into stable spinel structure. Furthermore, it is also found that potassium ions can be more easily embedded in the layered MnO2 with oxygen vacancies due to the lower energy demand compared with the pure MnO2. Meanwhile, the MnOx@graphene microspheres electrode exhibits a capacity retention as high as 90% after 10,000 cycles at 10 A g−1, indicating a superior cyclic stability.

Preparation of V2O5 porous microstructures with enhanced performances of lithium ion batteries

In this work, two V2O5 porous microstructures with nest-like shape and spherical shape were synthesized and characterized. As the formed V2O5 samples were used as active materials for the preparation of lithium-ion batteries, the enhanced electrochemical performances could be obtained. The novel structure endows the electrode materials shorter diffusion pathways and contributes to the transport of Li+-electrons. For the formed V2O5 porous microspheres electrode, a stable reversible specific capacity of 989.8 mA h g−1 can be obtained at 0.5 A g−1 after 350 cycles. As the current density gradually increases to 5.0 A g−1, the reversible capacity still maintains at 426.2 mA h g−1. These characteristics prove that the formed V2O5 porous microspheres present a wide application prospect in the field of portable energy storage device.

Ni2V2O7 dandelion microsphere for a high-performance electrocatalyst in water splitting

Water splitting is an effective way to produce hydrogen to solve the energy crisis problem, and inorganic metal compounds are widely used in electrocatalysis field due to efficient hydrogen evolution reaction (HER). Herein, we synthesize Ni2V2O7 dandelion microsphere from nickel nitrate and vanadium pentoxide by “one-step hydrothermal” way, which exhibits large specific surface area of 102.74 m2 g−1. The as-prepared Ni2V2O7 microsphere shows good electrocatalysis performances including OER overpotential of 358 mV and good stability, as well as HER overpotential of 195 mV. Furthermore, the Ni2V2O7 microsphere electrode is assembled to Ni2V2O7 microsphere//Ni2V2O7 microsphere system, showing the water splitting voltage of 1.50 V at 10 mA cm−2 by two-electrode method, which is much lower than those of commercial RuO2//Pt/C system and most of spinel oxides electrocatalysts. Our work opens up a new and facile avenue for fabricating inorganic microsphere electrocatalyst in hydrogen production field.