Effect of Initial Reactants and Reaction Temperature on Molten Salt Synthesis of CuCo₂O₄ and Its Sustainable Energy Storage Properties

We have prepared CuCo₂O₄ using 0.5 M NaNO₃ and 0.5 M LiNO₃ molten salts at different temperatures (410 and 610 °C) in the air. This was later used as an anode material for LIBs. The morphology, structure, and electrochemical properties of the products were observed using various techniques such as scanning electron microscopy, X-ray diffraction (XRD), Brunauer–Emmett–Teller surface and density method, cyclic voltammetry, and galvanostatic cycling tests. The XRD patterns showed a minor CuO phase in addition to the major CuCo₂O₄ phase in most of the reactant and salt combination. CuCo₂O₄ prepared using copper sulfate and cobalt sulfate at 610 °C and copper sulfate and cobalt acetate at 410 °C showed the best performance with capacities of 848 mAh g^–1 and 882 mAh g^–1 and capacity retentions of 93% and 94%, respectively

Energy Storage Studies on InVO₄ as High Performance Anode Material for Li-Ion Batteries

InVO₄ has attracted much attention as an anode material due to its high theoretical capacity. However, the effect of preparation methods and conditions on morphology and energy storage characteristic has not been extensively investigated and will be explored in this project. InVO₄ anode material was prepared using five different preparation methods: solid state, urea combustion, precipitation, ball-milling, and polymer precursor methods. Morphology and physical properties of InVO₄ were then analyzed using X-ray diffraction (XRD), scanning electron microscope (SEM), and Brunauer–Emmett–Teller (BET) surface area method. XRD patterns showed that orthorhombic phased InVO₄ was synthesized. Small amounts of impurities were observed in methods II, III, and V using XRD patterns. BET surface area ranged from 0.49 to 9.28 m² g^–1. SEM images showed slight differences in the InVO₄ nanosized crystalline structures with respect to preparation methods and conditions. Energy storage studies showed that, among all the preparation methods, the urea combustion method produced the best electrochemical results, with negligible capacity fading between the 2nd and 50th cycles and high capacity of 1241 mA h g^–1 at the end of the 20th cycle, close to the theoretical capacity value. Precipitation method also showed good performance, with capacity fading (14%) and capacity of 1002 mA h g^–1 at the 20th cycle. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) was then used to determine the reaction mechanisms of InVO₄

Maghemite Nanoparticles on Electrospun CNFs Template as Prospective Lithium-Ion Battery Anode

In this work, maghemite (γ-Fe₂O₃) nanoparticles were uniformly coated on carbon nanofibers (CNFs) by a hybrid synthesis procedure combining an electrospinning technique and hydrothermal method. Polyacrylonitrile nanofibers fabricated by the electrospinning technique serve as a robust support for iron oxide precursors during the hydrothermal process and successfully limit the aggregation of nanoparticles at the following carbonization step. The best materials were optimized under a carbonization condition of 600 °C for 12 h. X-ray diffraction and electron microscopy studies confirm the formation of a maghemite structure standing on the surface of CNFs. The average size of γ-Fe₂O₃ nanoparticles is below 100 nm, whereas CNFs are ∼150 nm in diameter. In comparison with aggregated bare iron oxide nanoparticles, the as-prepared carbon–maghemite nanofibers exhibit a higher surface area and greatly improved electrochemical performance (>830 mAh g^–1 at 50 mA g^–1 for 40 cycles and high rate capacity up to 5 A g^–1 in the voltage range of 0.005–3 V vs Li). The greatly enhanced electrochemical performance is attributed to the unique one-dimensional nanostructure and the limited aggregation of nanoparticles

Constructing Highly Oriented Configuration by Few-Layer MoS₂: Toward High-Performance Lithium-Ion Batteries and Hydrogen Evolution Reactions

Constructing three-dimensional (3D) architecture with oriented configurations by two-dimensional nanobuilding blocks is highly challenging but desirable for practical applications. The well-oriented open structure can facilitate storage and efficient transport of ion, electron, and mass for high-performance energy technologies. Using MoS₂ as an example, we present a facile and effective hydrothermal method to synthesize 3D radially oriented MoS₂ nanospheres. The nanosheets in the MoS₂ nanospheres are found to have less than five layers with an expanded (002) plane, which facilitates storage and efficient transport of ion, electron, and mass. When evaluated as anode materials for rechargeable Li-ion batteries, the MoS₂ nanospheres show an outstanding performance; namely, a specific capacity as large as 1009.2 mA h g^–1 is delivered at 500 mA g^–1 even after 500 deep charge/discharge cycles. Apart from promising the lithium-ion battery anode, this 3D radially oriented MoS₂ nanospheres also show high activity and stability for the hydrogen evolution reaction

Template Free Facile Molten Synthesis and Energy Storage Studies on MCo₂O₄ (M = Mg, Mn) as Anode for Li-Ion Batteries

Spinel MCo₂O₄ (M = Mg, Mn) materials were synthesized using a template free molten salt method with various precursor salts. Powder X-ray diffraction, Brunauer–Emmett–Teller (BET) surface area analysis, scanning electron microscopy, and transmission electron microscopy were carried out to characterize the phase, structure, and morphology of the compounds. Electrochemical cycling was carried out between voltages 0.005 and 3.0 V was carried out on button cells. At the end of cycling using 60 mA g^–1, MgCo₂O₄ showed reversible capacity of 816 (±5) mAh g^–1 after 50 cycles and MnCo₂O₄ showed a capacity fading of only 4% after 45 cycles retaining a capacity of 863 (±5) mAh g^–1. In addition, cyclic voltammetry and electrochemical impedance spectroscopy were carried out on select cycles to study the electrode kinetics

Mixed Oxides, (Ni_1–<i>x</i>Zn_<i>x</i>)Fe₂O₄ (<i>x</i> = 0, 0.25, 0.5, 0.75, 1): Molten Salt Synthesis, Characterization and Its Lithium-Storage Performance for Lithium Ion Batteries

We prepared solid solutions based on Ni, Zn, and Fe oxides to be used as nanomaterials for anodes of Li-ion batteries. The materials were synthesized using molten salt method with KCl as the molten salt. The prepared nanomaterials (Ni_1–<i>x</i>Zn_<i>x</i>)­Fe₂O₄ (<i>x</i> = 0, 0.25, 0.5, 0.75, 1) were subsequently characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), the Brunauer–Emmett–Teller surface and density methods. Cyclic voltammetry (CV) and galvanostatic cycling tests were then conducted to understand the lithium storage performance of the electrodes. Electrochemical impedance spectroscopy (EIS) was also performed to analyze the kinetics of our electrodes and other characteristics of the battery cell. The electrochemical properties of prepared compounds showed reversible capacities (mAh/g) of 706, 819, 603, 781, 637 for <i>x</i> = 0, 0.25, 0.5, 0.75, and 1 at the end of the 50th cycle

Sustainable Graphenothermal Reduction Chemistry to Obtain MnO Nanonetwork Supported Exfoliated Graphene Oxide Composite and its Electrochemical Characteristics

Exfoliated graphene oxide (EG)/manganese­(II) oxide (MnO) composite powder is synthesized by simple solid state graphenothermal reduction process. Structural, chemical, and morphological studies confirm the formation of EG/MnO composite in which cubic MnO crystallites are found to anchor onto EG surfaces. The as-synthesized EG/MnO composite is constituted with 65 and 35 wt % of MnO and EG, respectively. The EG/MnO composite exhibits a specific surface area of ∼82 m² g^–1 and an average pore size of ∼12 nm. As an anode in lithium-ion batteries, the EG/MnO composite shows a high reversible capacity of 936 mAh g^–1 at a current rate of 75 mA g^–1. Capacity retention of ∼84% (784 mAh g^–1) is observed even at the 100th cycle which corresponds to a Coulombic efficiency of ∼99%. Cyclic voltammetry studies on the composite show that Li storage is owing to reversible conversion reactions of MnO and electrochemical absorption/desorption by EG. Electrochemical impedance spectroscopy studies clearly show easy lithiation kinetics. Owing to the electrochemical performance of EG/MnO composite and its easy, reproducible, and scalable synthesis procedure, it is an excellent addition to this class of similar materials

RGO/Stibnite Nanocomposite as a Dual Anode for Lithium and Sodium Ion Batteries

RGO/Sb₂S₃ nanocomposite has been investigated in this study as a dual anode material for Li- and Na-ion battery applications. The stibnite phase of Sb₂S₃, and its rGO composite have been obtained from a molecular complex, Sb­(SCOPh)₃ or its rGO mixture by solid state decomposition or hydrothermal treatment. The pristine sample consists of micron sized particles with rod-like morphology while the rGO composite is made of nanoparticles of Sb₂S₃ embedded in rGO sheets. Electrochemical lithium and sodium storage properties of the prepared materials have been investigated using galvanostatic cycling, cyclic voltammetry, and electrochemical impedance spectroscopy studies. The rGO composite demonstrates better lithium storage capacity than the pristine sample owing to enhanced conductivity. In addition, the rGO sheets act as a buffer for volume change during lithium/sodium cycling resulting in a better energy storage

Experimental Elucidation of a Graphenothermal Reduction Mechanism of Fe₂O₃: An Enhanced Anodic Behavior of an Exfoliated Reduced Graphene Oxide/Fe₃O₄ Composite in Li-Ion Batteries

The graphenothermal reduction mechanism of Fe₂O₃ by graphene oxide (GO) is elucidated through careful experimental analysis. The degree of oxidation (DO) of GO plays a key role in controlling the reduction of Fe₂O₃ by GO. GO with low DO follows a conventional three-stage reaction path, i.e., ′2GO + Fe₂O₃ → EG/Fe₃O₄ (Stage I) → EG/FeO (Stage II) → EG/Fe (Stage III)′ (where EG is exfoliated reduced graphene oxide), at temperatures 650 and 750 °C to reduce Fe₂O₃, whereas the GO with higher DO transforms rapidly and ceases the reduction at Stage I, i.e., with the formation of EG/Fe₃O₄ at 650 °C. It is also found that slow thermal treatment of GO continues the reduction to Stage II and further to Stage III depending on time of heating and temperature. EG/Fe₃O₄ (synthesized at 550 °C, 5 h) by using GO with low DO showed superior cycling performance as an anode of Li-ion battery than its counterpart prepared (at 650 °C, 5 h) from GO with high DO owing to good contacts between EG and Fe₃O₄. EG/Fe₃O₄ (synthesized at 550 °C, 5 h) exhibited reversible capacity as high as 860 mAh/g which is greater than the specific capacity of EG/Fe₃O₄ synthesized (at 650 °C, 5 h) by 150 mAh/g. Overall, EG/Fe₃O₄ (synthesized at 550 °C, 5 h) outperformed its counterpart (i.e., EG/Fe₃O₄ synthesized at 650 °C, 5 h) by exhibiting excellent cycling stability and rate capability at current rates ranging from 0.5 to 3.0 C

Lithium Storage Properties of Pristine and (Mg, Cu) Codoped ZnFe₂O₄ Nanoparticles

ZnFe₂O₄ and Mg_<i>x</i>Cu_0.2Zn_{0.82–<i>x</i>}Fe_1.98O₄ (where <i>x</i> = 0.20, 0.25, 0.30, 0.35, and 0.40) nanoparticles were synthesized by sol–gel assisted combustion method. X-ray diffraction (XRD), FTIR spectroscopy, Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Brunauer–Emmett–Teller (BET) surface area studies were used to characterize the synthesized compounds. ZnFe₂O₄ and the doped compounds crystallize in <i>Fd</i>3<i>m</i> space group. The lattice parameter of ZnFe₂O₄ is calculated to be <i>a</i> = 8.448(3) Å, while the doped compounds show a slight decrease in the lattice parameter with an increase in the Mg content. The particle size of all the compositions are in the range of ∼50–80 nm, and the surface area of the compounds are in the range of 11–12 m² g^–1. Cyclic voltammetry (CV), galvanostatic cycling, and electrochemical impedance spectroscopy (EIS) studies were used to investigate the electrochemical properties of the different compositions. The as-synthesized samples at 600 °C show large-capacity fading, while the samples reheated at 800 °C show better cycling stability. ZnFe₂O₄ exhibits a high reversible capacity of 575 mAh g^–1 after 60 cycles at a current density of 100 mA g^–1. Mg_0.2Cu_0.2Zn_0.62Fe_1.98O₄ shows a similar capacity of 576 mAh g^–1 after 60 cycles with better capacity retention