A first principles study of corundum V2O3 material as a promising anode for Li/Mg/Al-ion batteries

In this work the electrochemical properties of corundum V2O3 are calculated using the first principle calculations. Our results highly recommend V2O3 as promising anode for both MIBs and AIBs.

Discharging Behavior of Hollandite α-MnO2 in a Hydrated Zinc-Ion Battery

Hollandite, α-MnO₂, is of interest as a prospective cathode material for hydrated zinc-ion batteries (ZIBs); however, the mechanistic understanding of the discharge process remains limited. Herein, a systematic study on the initial discharge of an α-MnO₂ cathode under a hydrated environment was reported using density functional theory (DFT) in combination with complementary experiments, where the DFT predictions well described the experimental measurements on discharge voltages and manganese oxidation states. According to the DFT calculations, both protons (H⁺) and zinc ions (Zn²⁺) contribute to the discharging potentials of α-MnO₂ observed experimentally, where the presence of water plays an essential role during the process. This study provides valuable insights into the mechanistic understanding of the discharge of α-MnO₂ in hydrated ZIBs, emphasizing the crucial interplay among the H₂O molecules, the intercalated Zn²⁺ or H⁺ ions, and the Mn⁴⁺ ions on the tunnel wall to enhance the stability of discharged states and, thus, the electrochemical performances in hydrated ZIBs.

Review of ZnO Binary and Ternary Composite Anodes for Lithium-Ion Batteries

To enhance the performance of lithium-ion batteries, zinc oxide (ZnO) has generated interest as an anode candidate owing to its high theoretical capacity. However, because of its limitations such as its slow chemical reaction kinetics, intense capacity fading on potential cycling, and low rate capability, composite anodes of ZnO and other materials are manufactured. In this study, we introduce binary and ternary composites of ZnO with other metal oxides (MOs) and carbon-based materials. Most ZnO-based composite anodes exhibit a higher specific capacity, rate performance, and cycling stability than a single ZnO anode. The synergistic effects between ZnO and the other MOs or carbon-based materials can explain the superior electrochemical characteristics of these ZnO-based composites. This review also discusses some of their current limitations.

Local and Bulk Probe of Vanadium-Substituted α-Manganese Oxide (α-KxVyMn8-yO16) Lithium Electrochemistry

A series of V-substituted α-MnO₂ (K_xMn_8-yV_yO₁₆·nH₂O, y = 0, 0.2, 0.34, 0.75) samples were successfully synthesized without crystalline or amorphous impurities, as evidenced by X-ray diffraction (XRD) and Raman spectroscopy. Transmission electron microscopy (TEM) revealed a morphological evolution from nanorods to nanoplatelets as V-substitution increased, while electron-energy loss spectroscopy (EELS) confirmed uniform distribution of vanadium within the materials. Rietveld refinement of synchrotron XRD showed an increase in bond lengths and a larger range of bond angles with increasing V-substitution. X-ray absorption spectroscopy (XAS) of the as-prepared materials revealed the V valence to be >4+ and the Mn valence to decrease with increasing V content. Upon electrochemical lithiation, increasing amounts of V were found to preserve the Mn-Mn_edge relationship at higher depths of discharge, indicating enhanced structural stability. Electrochemical testing showed the y = 0.75 V-substituted sample to deliver the highest capacity and capacity retention after 50 cycles. The experimental findings were consistent with the predictions of density functional theory (DFT), where the V centers impart structural stability to the manganese oxide framework upon lithiation. The enhanced electrochemistry of the y = 0.75 V-substituted sample is also attributed to its smaller crystallite size in the form of a nanoplatelet morphology, which promotes facile ion access via reduced Li-ion diffusion path lengths.

Structural and electrochemical investigation of crystallite size controlled zinc ferrite (ZnFe2O4)

Zinc ferrite, ZnFe₂O₄(ZFO), is a promising electrode material for next generation Li-ion batteries because of its high theoretical capacity and low environmental impact. In this report, synthetic control of crystallite size from the nanometer to submicron scale enabled probing of the relationships between ZFO size and electrochemical behavior. A facile two-step coprecipitation and annealing preparation method was used to prepare ZFO with controlled sizes ranging ∼9 to >200 nm. Complementary synchrotron and electron microscopy techniques were used to characterize the series of materials. Increasing the annealing temperature increased crystallinity and decreased microstrain, while local structural ordering was maintained independent of crystallite size. Electrochemical characterization revealed that the smaller sized materials delivered higher capacities during initial lithiation. Larger sized particles exhibited a lack of distinct electrochemical signatures above 1.0 V, suggesting that the longer diffusion length associated with greater crystallite size causes the lithiation process to proceed via non discrete lithium insertion, cation migration, and conversion processes. Notably, larger particles exhibited enhanced electrochemical reversibility over 50 cycles, with capacity retention improving from <20% to >40% at C/2 cycling rate. This intriguing result was probed through x-ray absorption spectroscopy (XAS) and x-ray photoelectron spectroscopy (XPS) measurements of the cycled electrodes. XAS revealed that the larger crystallite size materials do not completely convert to Fe⁰during the first lithiation and that independent of size, delithiation results in the formation of nanocrystalline FeO and ZnO phases rather than ZnFe₂O₄. After 20 cycles, the larger crystallites showed reversibility between partially oxidized FeO in the charged state and Fe⁰in the discharged state, while the smaller crystallite size material was electrochemically inactive as Fe⁰. XPS analysis revealed more significant solid electrolyte interphase (SEI) formation on the cycled electrodes utilizing ZFO with smaller crystallite size. This finding suggests that excessive SEI buildup on the smaller sized, higher surface area ZFO particles contributes to their reduced electrochemical reversibility relative to the larger crystallite size materials.

Nanostructured ZnFe2O4: An Exotic Energy Material

More people, more cities; the energy demand increases in consequence and much of that will rely on next-generation smart materials. Zn-ferrites (ZnFe₂O₄) are nonconventional ceramic materials on account of their unique properties, such as chemical and thermal stability and the reduced toxicity of Zn over other metals. Furthermore, the remarkable cation inversion behavior in nanostructured ZnFe₂O₄ extensively cast-off in the high-density magnetic data storage, 5G mobile communication, energy storage devices like Li-ion batteries, supercapacitors, and water splitting for hydrogen production, among others. Here, we review how aforesaid properties can be easily tuned in various ZnFe₂O₄ nanostructures depending on the choice, amount, and oxidation state of metal ions, the specific features of cation arrangement in the crystal lattice and the processing route used for the fabrication.

Engineering zinc ferrite nanoparticles in a hierarchical graphene and carbon nanotube framework for improved lithium-ion storage

This work presents the successful fabrication of a composite made of multi-walled carbon nanotubes and reduced graphene oxide, with immobilized zinc ferrite nanoparticles (ZnFe₂O₄@CNT/RGO). Functionalized CNT (F-CNT) and few-layered graphene oxide (GO) not only works as a precursor for the hierarchical CNT/RGO skeleton, but also participates in the redox reactions with zinc and ferrous ions to synthesize the intermediate products ZnO@CNT and FeOOH@RGO, respectively. A ZnO@CNT/FeOOH@RGO composite is obtained by through the spontaneous assembly process between the above intermediate species, and the final ZnFe₂O₄@CNT/RGO composite is fabricated through a simple solid-state reaction. The ZnFe₂O₄@CNT/RGO composite delivers a reversible capacity of about 1250 mAh·g^-1 after 100 cycles at a low current of 200 mA·g^-1, about 1100 mAh·g^-1 after 300 cycles at a high current of 1000 mA·g^-1. It has been verified that an increase in battery performance can be attributed to the engineered hierarchical CNT/RGO supportive skeleton, the generation of smaller electrochemically active ZnO and Fe₂O₃ crystals, and pseudocapacitive behavior. The sample design and preparation method in this work are both economical and scalable, allowing further development and use in other applications.

(De)lithiation of spinel ferrites Fe3O4, MgFe2O4, and ZnFe2O4: a combined spectroscopic, diffraction and theory study

Iron based materials hold promise as next generation battery electrode materials for Li ion batteries due to their earth abundance, low cost, and low environmental impact. The iron oxide, magnetite Fe3O4, adopts the spinel (AB2O4) structure. Other 2+ cation transition metal centers can also occupy both tetrahedral and/or octahedral sites in the spinel structure including MgFe2O4, a partially inverse spinel, and ZnFe2O4, a normal spinel. Though structurally similar to Fe3O4 in the pristine state, previous studies suggest significant differences in structural evolution depending on the 2+ cation in the structure. This investigation involves X-ray absorption spectroscopy and X-ray diffraction affirmed by density functional theory (DFT) to elucidate the role of the 2+ cation on the structural evolution and phase transformations during (de)lithiation of the spinel ferrites Fe3O4, MgFe2O4, and ZnFe2O4. The cation in the inverse, normal and partially inverse spinel structures located in the tetrahedral (8a) site migrates to the previously unoccupied octahedral 16c site by 2 electron equivalents of lithiation, resulting in a disordered [A]16c[B2]16dO4 structure. DFT calculations support the experimental results, predicting full displacement of the 8a cation to the 16c site at 2 electron equivalents. Substitution of the 2+ cation results in segregation of oxidized phases in the charged state. This report provides significant structural insight into the (de)lithiation mechanisms for an intriguing class of iron oxide materials.

Simple and effective synthesis of zinc ferrite nanoparticle immobilized by reduced graphene oxide as anode for lithium-ion batteries

In this work, a simple and effective method is developed to synthesize zinc ferrite nanoparticles (ZnFe₂O₄) in a redox coprecipitation reaction system containing only ferrous and zinc salt followed by a solid-state reaction. On this foundation, ZnFe₂O₄ nanoparticles with reduced size are further immobilized by reduced graphene oxide (RGO) to engineer a ZnFe₂O₄/RGO composite by simply introducing graphene oxide (GO) in the above reaction system. The ZnFe₂O₄/RGO composite electrode exhibits attractive lithium-ion storage capability with a reversible capacity of about 760 mAh·g^-1 for 200 charge/discharge cycles and 603 mAh·g^-1 for 700 cycles under a current rate of 1.0 A·g^-1. The robust and porous RGO supporting framework, well immobilized ZnFe₂O₄ nanoparticles with controlled size and pseudocapacitive behavior of the composite jointly ensure the good battery performance. Moreover, the synthetic route for ZnFe₂O₄ nanoparticles and ZnFe₂O₄/RGO composite is simple and economic, which may be further developed for massive production and applied in other fields.

Tunable Metallogels Based on Bifunctional Ligands: Precursor Metallogels, Spinel Oxides, Dye and CO2 Adsorption

A semisolid gel material is a gift of serendipity via various chemical interactions, and metal incorporation (metallogels) imparts diverse functional properties. In this work, we have synthesized four metallogels from tetrapodal and hexapodal carboxylic acid/amide-based low-molecular-weight gelators with Ni(II) and Cu(II) salts. These metallogels can be tuned to be a low-temperature precursor of porous spinel oxides. These xerogels exhibit impressive water soluble dye and carbon dioxide adsorption, which coupled with the tunability and facile synthesis of porous spinel oxides underscores their potential in environmental remediation and energy applications.

Spinel ferrite (AFe2O4)-based heterostructured designs for lithium-ion battery, environmental monitoring, and biomedical applications

The development of spinel ferrite nanomaterial (SFN)-based hybrid architectures has become more popular owing to the fascinating physicochemical properties of SFNs, such as their good electro-optical and catalytic properties, high chemothermal stability, ease of functionalization, and superparamagnetic behaviour. Furthermore, achieving the perfect combination of SFNs and different nanomaterials has promised to open up many unique synergistic effects and advantages. Inspired by the above-mentioned noteworthy properties, numerous and varied applications have been recently developed, such as energy storage in lithium-ion batteries, environmental pollutant monitoring, and, especially, biomedical applications. In this review, recent development efforts relating to SFN-based hybrid designs are described in detail and logically, classified according to 4 major hybrid structures: SFNs/carbonaceous nanomaterials; SFNs/metal–metal oxides; SFNs/MS₂; and SFNs/other materials. The underlying advantages of the additional interactions and combinations of effects, compared to the standalone components, and the potential uses have been analyzed and assessed for each hybrid structure in relation to lithium-ion battery, environmental, and biomedical applications.

We have summarized recent developments in SFN-based hybrid designs. The additional interactions, combination effects, and important changes have been analyzed and assessed for LIB, environmental monitoring, and biomedical applications.

Size-dependent kinetics during non-equilibrium lithiation of nano-sized zinc ferrite

Spinel transition metal oxides (TMOs) have emerged as promising anode materials for lithium-ion batteries. It has been shown that reducing their particle size to nanoscale dimensions benefits overall electrochemical performance. Here, we use in situ transmission electron microscopy to probe the lithiation behavior of spinel ZnFe₂O₄ as a function of particle size. We have found that ZnFe₂O₄ undergoes an intercalation-to-conversion reaction sequence, with the initial intercalation process being size dependent. Larger ZnFe₂O₄ particles (40 nm) follow a two-phase intercalation reaction. In contrast, a solid-solution transformation dominates the early stages of discharge when the particle size is about 6–9 nm. Using a thermodynamic analysis, we find that the size-dependent kinetics originate from the interfacial energy between the two phases. Furthermore, the conversion reaction in both large and small particles favors {111} planes and follows a core-shell reaction mode. These results elucidate the intrinsic mechanism that permits fast reaction kinetics in smaller nanoparticles.

Reducing particle size of electrode materials to nanoscale dimensions is believed responsible for their enhanced reaction kinetics and electrochemical performance. Here, the authors use in situ transmission electron microscopy to study the dynamic process of the spinel zinc ferrite nanoparticles as a function of size, finding that the intercalation reaction pathway changes below a critical particle size.

Essential Role of Spinel ZnFe2O4 Surfaces during Lithiation

Spinel zinc ferrite (ZnFe₂O₄) is a well-known anode material in lithium ion batteries (LIBs) because of its large theoretical capacity. However, the high potentials observed at the initial stage of lithiation cannot be captured using a model of Li⁺ intercalation into the stoichiometric ZnFe₂O₄ bulk. Here, using density functional theory, we report for the first time that the ZnFe₂O₄ surfaces are responsible for the measured initial potentials. Among the three identified stable surfaces, ZnFeO₂-terminated ZnFe₂O₄(1 1 0), O-terminated ZnFe₂O₄(1 1 1), and Zn-terminated ZnFe₂O₄(1 1 1), both (1 1 1) surfaces display higher lithiation potentials than the (1 1 0) surface, and the estimated potentials based on Zn-terminated (1 1 1) fit well with the experimental observations, whereas using the models based on ZnFe₂O₄(1 1 0) and previously ZnFe₂O₄ bulk, the estimated potentials are much lower. In terms of Li⁺ diffusion, the Zn-terminated ZnFe₂O₄(1 1 1) surface is the most active, where the energetically favorable saturation of Li⁺ on the surface is able to facilitate the process. Our results provide a new strategy for the design of LIB materials, via controlling the particle shape and the associated surface characteristics, thus enhancing the discharging performance.

Synthesis and Characterization of CuFe2O4 Nano/Submicron Wire-Carbon Nanotube Composites as Binder-free Anodes for Li-Ion Batteries

A series of one-dimensional CuFe₂O₄ (CFO) nano/submicron wires possessing different diameters, crystal phases, and crystal sizes have been successfully generated using a facile template-assisted coprecipitation reaction at room temperature, followed by a short postannealing process. The diameter and crystal structure of the resulting CuFe₂O₄ (CFO) wires were judiciously tuned by varying the pore size of the template and the postannealing temperature, respectively. Carbon nanotubes (CNTs) were incorporated to generate CFO-CNT binder-free anodes, and multiple characterization techniques were employed with the goal of delineating the relationships between electrochemical behavior and the properties of both the CFO wires (crystal phase, wire diameter, crystal size) and the electrode architecture (binder-free vs conventionally prepared approaches). The study reveals several notable findings. First, the crystal phase (cubic or tetragonal) did not influence the electrochemical behavior in this CFO system. Second, regarding crystallite size and wire diameter, CFO wires with larger crystallite sizes exhibit improved cycling stability, whereas wires possessing smaller diameters exhibit higher capacities. Finally, the electrochemical behavior is strongly influenced by the electrode architecture, with CFO-CNT binder-free electrodes demonstrating significantly higher capacities and cycling stability compared to conventionally prepared coatings. The mechanism(s) associated with the high capacities under low current density but limited electrochemical reversibility of CFO electrodes under high current density were probed via X-ray absorption spectroscopy mapping with submicron spatial resolution for the first time. Results suggest that the capacity of the binder-free electrodes under high rate is limited by the irreversible formation of Cu⁰, as well as limited reduction of Fe³⁺ to Fe²⁺, not Fe⁰. The results (1) shed fundamental insight into the reversibility of CuFe₂O₄ materials cycled at high current density and (2) demonstrate that a synergistic effort to control both active material morphology and electrode architecture is an effective strategy for optimizing electrochemical behavior.