Enhanced electrochemical performance of flower-like Co 3 O 4 as an anode material for high performance lithium-ion batteries

Ruddlesden-Popper 2D Perovskite-MoS2 Hybrid Heterojunction Photocathodes for Efficient and Scalable Photo-Rechargeable Li-Ion Batteries

Photo-rechargeable batteries (PRBs) can provide a compact solution to power autonomous smart devices located at remote sites that cannot be connected with the grid. The study reports the Ruddlesden-Popper (RP) metal halide perovskite (MHP) and molybdenum disulfide (MoS2) hybrid heterojunction-based photocathodes for Li-ion photo-rechargeable battery (Li-PRB) applications. Hybrid Lithium-ion batteries (LIBs) have demonstrated an average discharge specific capacity of 144.46 and 129.17 mAhg-1 for 50 cycles when operating at 176 and 294 mAg-1, respectively compared to the pristine LIBs which have shown specific capacity of 37.48 and 25.60 mAhg-1 under similar conditions. Hybrid Li-PRB has achieved an average dark discharge specific capacities of 128.66 mAhg-1 (capacity retention: 96.56%) which enhanced to 180.67 mAhg-1 under illumination (capacity retention: 97.39%; photo-enhancement: 40.42%) at 64 mAg-1. Excellent performance of hybrid Li-PRB is attributed to the formation of type-II heterojunction that leads to improved crystallinity and film morphology. The PRB has demonstrated a high photo conversion and storage efficiency (PC-SE) of 0.52% under standard 1 Sun illumination, which outperforms other previously reported MHP based LIBs and PRBs. This work provides a novel approach of harnessing the potential of MHPs for PRBs and offers new avenues for MHP photocathodes for various applications beyond PRBs.

Synergistic effect between ZnCo2O4 and Co3O4 induces superior electrochemical performance as anodes for lithium-ion batteries

The current work describes a facile synthesis of spinel-type ZnCo2O4 along with an additional phase, Co3O4, by simply maintaining a non-stoichiometric ratio of Zn and Co precursors. Pure ZnCo2O4 and Co3O4 were also synthesized using the same method to compare results. The obtained morphologies of samples show that small-sized nanoparticles are interconnected and form a porous nanosheet-like structure. When used as anode materials for Li-ion batteries, the ZnCo2O4/Co3O4 nanocomposite electrode exhibits a highly stable charge capacity of 1146.2 mA h g-1 at 0.5C after 350 cycles, which is superior to those of other two pure electrodes, which can be attributed to its optimum porosity, synergistic effect of ZnCo2O4 and Co3O4, increased active sites for Li+ ion diffusion, and higher electrical conductivity. Although the pure Co3O4 electrode displayed a much higher rate capability than the ZnCo2O4/Co3O4 nanocomposite electrode at all investigated current rates, the Co3O4 morphology apparently could not withstand long-term cycling, and the electrode became pulverized due to the repeated volume expansion/contraction, resulting in a rapid decrease in the capacity.

Rapid microwave hydrothermal processed spinel Co3O4nanospheres infused N-doped graphene nanosheets for high-performance battery

Spinel Co₃O₄nanospheres have been synthesized by the microwave-assisted hydrothermal method. The N-doped graphene nanosheets (NGN) were synthesized using Hummer's method. The prepared spinel Co₃O₄and NGN were mixed under certain proportions using an ultrasonication process and treated with microwave radiation to prepare a novel spinel Co₃O₄nanospheres infused NGN. The synthesized samples were characterized by x-ray diffraction, Raman spectroscopy, Zetasizer, scanning electron microscope/transmission electron microscopy and x-ray photoelectron spectroscopy for identifying crystal structure and phase, particle size, and the morphology of the nanostructure and the elemental configuration, respectively. The prepared spinel Co₃O₄/NGN were used as anode material and lithium metal as a reference electrode to fabricate half cell using Swagelok cell components. The electrochemical properties were studied and found to exhibit a larger specific capacity of 575 mAh g^-1compared to traditional graphite electrodes, after 100 cycles under 0.1 C rate with a coulombic efficiency of ≈100%. The good electrochemical properties ascribe to the distinctive surface morphological nanostructures of nanoporous nanospheres of spinel Co₃O₄nanospheres and nanosheets of N-doped graphene that reduce the lithium-ion diffusion pathway. The developed anode material would be a potential electrode for lithium ion battery applications.

Synthesis, Characterization and Applications of Spinel Cobaltite Nanomaterials

Recently, spinel structures (AB₂O₄) Nanoparticles (NPs) having binary and ternary mixtures of metal oxides have been established as promising redox catalysts. Due to the presence of two mixed valence metal cations, transport of electrons takes place easily between multiple transition-metal cations with relatively low energy of activation. Among these, spinel cobaltite (MCo₂O₄) is very attractive due to its low cost, non-toxicity, higher stability, higher electronic conductivity and electrochemical property. To date, MCo₂O₄ has been used in the fabrication of supercapacitors, electrodes for oxygen evolution reaction, and electrochemical sensors for glucose. A variety of MMCo₂O₄materials have been synthesized, characterized, and utilized in the fabrication of super capacitors, electrodes for oxygen evolution reaction, and electrochemical sensors for glucose. The progress in the field of the spinel MCo₂O₄ materials opens the door to novel and efficient applications in the nanoscience and nanotechnology, and elctrochemistry.

Low-temperature combustion of methane over graphene templated Co3O4 defective-nanoplates

Transition metal oxides are the potential catalysts to replace noble-metal based catalyst for the catalytic combustion of methane due to the tolerable reactivity and low cost. However, these catalysts are challenged by the low temperature reactivity. Herein, the surface defective Co₃O₄ nanoplates are realized through a facile co-precipitation and thermal reduction method with the association of GO. The resultant catalysts (CoGO50) demonstrate a superior low-temperature reactivity for the methane oxidation to CO₂ and H₂O in comparison with the common Co₃O₄ catalyst. The reliable stability of CoGO50 catalyst was proved by 80 h testing with intermittent feeding of water vapor. The experimental analysis demonstrates that the presence of a small amount of GO significantly affects the catalysts in surface valence state, active oxygen species and surface oxygen vacancies through reacting with the cobalt oxide as a reductant. Moreover, GO plays as 2D confine template to form smaller and thinner nanoplates. This work provides a facile method to control the surface properties of catalyst not only for Co₃O₄ based catalysts but also for wider solid catalysts.

Solution combustion synthesis of a nanometer-scale Co3O4 anode material for Li-ion batteries

A novel solution combustion synthesis of nanoscale spinel-structured Co3O4 powder was proposed in this work. The obtained material was composed of loosely arranged nanoparticles whose average diameter was about 36 nm. The as-prepared cobalt oxide powder was also tested as the anode material for Li-ion batteries and revealed specific capacities of 1060 and 533 mAh·g-1 after 100 cycles at charge-discharge current densities of 100 and 500 mA·g-1, respectively. Moreover, electrochemical measurements indicate that even though the synthesized nanomaterial possesses a low active surface area, it exhibits a relatively high specific capacity measured at 100 mA·g-1 after 100 cycles and a quite good rate capability at current densities between 50 and 5000 mA·g-1.

The construction of CuCo2O4/N-doped reduced graphene oxide hybrid hollow spheres as anodes for sodium-ion batteries

Hierarchical CuCo₂O₄/N-doped reduced graphene oxide (CuCo₂O₄/N-rGO) hollow hybrid nanospheres was constructed and further applied as highly capacity anode materials for SIBs.

High-Loading Carbon Nanotubes on Polymer Nanofibers as Stand-Alone Anode Materials for Li-Ion Batteries

To address the instability and repulsive interaction of carbon nanotubes (CNTs) in Li-ion batteries, mixed polymers (polyacrylonitrile and polyvinylpyrrolidone) were employed as matrix support to ensure that CNT particles remain in place during charge/discharge process and prevent particle migration. Various CNT-based anodes have been reported, but these require metal support that could result in contact resistance. Hence, free-standing CNT electrodes are an attractive option. A simple method of electrospinning polymers and calcination at 800 °C is presented with CNT loading as high as 50 wt % can be obtained without binder and acts as main active material rather than an additive as described in previous studies. The anode [pyrolyzed polymer (PP)-CNT] showed excellent performance with a high discharge specific capacity of 960 mA h/g at a current density of 200 mA/g. The capacity at a higher current density (1600 mA/g) remained greater than graphite (372 mA h/g) at 521 mA h/g and showed a high stability for 675 cycles without exhibiting any significant capacity loss with a Coulombic efficiency of >95%. A rate capability experiment showed the reversibility of PP-CNTs after subjecting them to an increasing current density and regaining >95% of the initial capacity at a low current density (200 mA/g). The high capacitive performance of the material is attributed to the high loading of CNTs and their containment within the bulk of the polymer matrix to prevent particle migration and agglomeration as well as the capacity of the nanofibers to preserve a tight proximity of the electrolyte-electrode interface.

Synthesis of C/Co3O4 composite mesoporous hollow sphere sandwich graphene films for high-performance supercapacitors

rGO/C/Co₃O₄ electrodes have been successfully prepared for high performance asymmetric supercapacitors.

Electrochemical growth of Co(OH)2 nanoflakes on Ni foam for methanol electro-oxidation

Co(OH)₂ nanoflakes directly grown on Ni foam using an electrodeposition route exhibit a promising performance for electrocatalytic oxidation of methanol.

Mesoporous Mn2O3/reduced graphene oxide (rGO) composite with enhanced electrochemical performance for Li-ion battery

Transition metal oxides are the most promising candidates in low-cost and eco-friendly energy storage/conversion applications.

Facile synthesis of nanocrystalline-assembled nest-like NiO hollow microspheres with superior lithium storage performance

Interconnected nest-like NiO hollow microspheres assembled from nanocrystallites are prepared by a facile hydrothermal method followed by annealing at 700 °C in air.

Novel Bake-in-Salt Method for the Synthesis of Mesoporous Mn3O4@C Networks with Superior Cycling Stability and Rate Performance

The commercial applications of Mn₃O₄ in lithium ion batteries (LIBs) are greatly restricted because of the low electrical conductivity and poor cycling stability at high current density. To overcome these drawbacks, mesoporous Mn₃O₄@C networks were designed and synthesized via an improved bake-in-salt method using NaCl as the assistant salt, and without the protection of inert gas. The added NaCl plays a versatile role during the synthetic process, including the heat conducting medium, removable hard template and protective layer. Because of the homogeneous distribution of Mn₃O₄ nanoparticles within the carbon matrix, the as-prepared Mn₃O₄@C networks show excellent cycling stability in LIBs. After cycling for 950 times at a current density of 1 A g^-1, the discharge capacity of the as-prepared Mn₃O₄@C networks is determined to be 754.4 mA h g^-1, showing superior cycling stability as compared to its counterparts. The valuable and promising method, simple synthetic procedure and excellent cycling stability of the as-prepared Mn₃O₄@C networks makes it a promising candidate as the potential anode material for LIBs.

Hierarchical Mesoporous 3D Flower-like CuCo2O4/NF for High-Performance Electrochemical Energy Storage

Ternary spinel CuCo2O4 nanostructure clenches great potential as high-performance electrode material for next-generation energy storage systems because of its higher electrical conductivity and electrochemical activity. Carbon free and binder free 3D flower-like CuCo2O4 structure are grown on nickel foam (NF) via a facile hydrothermal synthesis method followed by annealing. The obtained CuCo2O4/NF is directly used as electrode for lithium ion batteries (LIBs) and supercapacitors (SCs) application. The electrochemical study of 3D flower-like CuCo2O4 as an electrode for LIB and SC shows highly mesoporous unique architecture plays important role in achieving high capacity/capacitance with superior cycle life. The high surface area and mesoporous nature not only offer sufficient reaction sites, but also can accelerate the liquid electrolyte to penetrate electrode and the ions to reach the reacting sites. In outcome, it exhibits highest capacity of 1160 mA h g(-1) after 200 cycles when used as an anode for LIB and specific capacitance of 1002 F g(-1) after 3000 cycles. The superior electrochemical of synthesized material is attributed to direct contact of electrode active material with good intrinsic electrical conductivity to the underneath conductive NF substrate builds up an express path for fast ion and electron transfer.

Unique 1D Co3O4 crystallized nanofibers with (220) oriented facets as high-performance lithium ion battery anode material

A novel one-step hydrothermal and calcination strategy was developed to synthesize the unique 1D oriented Co₃O₄ crystal nanofibers with (220) facets on the carbon matrix derived from the natural, abundant and low cost wool fibers acting as both carbon precursor and template reagent. The resultant W2@Co₃O₄ nanocomposite exhibited very high specific capacity and favorable high-rate capability when used as anode material of lithium ion battery. The high reversible Li⁺ ion storage capacity of 986 mAh g⁻¹ was obtained at 100 mA g⁻¹ after 150 cycles, higher than the theoretical capacity of Co₃O₄ (890 mAh g⁻¹). Even at the higher current density of 1 A g⁻¹, the electrode could still deliver a remarkable discharge capacity of 720 mAh g⁻¹ over 150 cycles.

Excellent lithium ion storage property of porous MnCo2O4 nanorods

The porous MnCo₂O₄ nanorods have been successfully prepared by a simple and economic method and exhibited a high electrochemical performance.

One-dimensional porous nanofibers of Co3O4 on the carbon matrix from human hair with superior lithium ion storage performance

One-dimensional (1D) hierarchical porous nanofibers of Co3O4 possessing of (220) facets on the carbon matrix from human hair (H2@Co3O4) with 20-30 nm in width and 3-5 μm in length are prepared by a facile solvothermal and calcination approach. The well crystallized small Co3O4 particles with the diameter of about 8-12 nm were closely aggregated together in the nanofibers. Electrochemical analyses show that the first discharge capacity of H2@Co3O4 electrode is 1368 mAh g(-1) at the current density of 0.1 A g(-1) based on the total mass of composite. A high reversible capacity of 916 mAh g (-1) was obtained over 100 cycles at 0.1 A g(-1), presenting a good cycling stability. When cycled at a high current density of 1 and 2 A g(-1), the specific capacity of 659 and 573 mAh g(-1) could be still achieved, respectively, indicating a superior power capability.

Cu2+ ions inducing the growth of porous Co3O4 nanospheres as high-capacity supercapacitors

Porous Co₃O₄ nanospheres were successfully synthesized using Cu²⁺ ions as structure-inducing agents, which exhibit good capacitive properties.

Self-assembly process of China rose-like β-Co(OH)2 and its topotactic conversion route to Co3O4 with optimizable catalytic performance

China rose-like structured β-Co(OH)₂ were fabricated by a facile and surfactant free solvothermal method.