Metal Oxide Anodes Research Articles

Lithiation phase behaviors of metal oxide anodes and extra capacities

Binary metal oxides have received sustained interest as anode materials due to their desirable capacities, exceeding theoretical values particularly in the first discharge. Although they have received increasing attention in recent years, topical debates persist regarding not only their lithiation mechanisms but also the origin of additional capacity. Aiming to resolve these disagreements, we perform a systematic study of a series of iron and manganese oxides to investigate their phase behavior during first discharge. Using a combination of in operando pair distribution function measurements and our recently developed Metropolis non-negative matrix factorization approach to address the analytical challenges concerning materials’ nanoscopic nature and phase heterogeneity, here we report unexpected observation of non-equilibrium FeO x solid-solution phases and pulverization of MnO. These processes are correlated with the extra capacities observed at different depths of discharge, pointing to a metal-dependent nature of this additional capacity and demonstrating the advantage of our approach with promising prospects for diverse applications. The extra capacity may have a dominant source depending on specific metal species bcc -FeO x intermediate lithiate via oxygen extraction from the Fe sublattice Local structure characterization using pair distribution function Robust phase deconvolution using Metropolis non-negative matrix factorization Binary metal oxide anodes in lithium-ion batteries show extra capacities at their initial discharge. In this article, Hua et al. perform a systematic study of iron and manganese oxides’ lithiation phase behaviors and report unexpected observations of bcc -FeO x solid solution and MnO pulverization, processes correlated with the extra capacities seen at different depths of discharge.

Li-Ion Capacitors Based on Activated Ferric Oxide as an Anode

Abstract Low-cost Fe-based electrode materials for Li-ion energy storage devices attract lots of attention. In this work, porous Fe2O3 nanoparticles are synthesized by a simple route. First, their lithium storage performance is investigated by assembling half-cell configurations with Li foil as the counter electrode. During initial dozens of cycles, capacities of Fe2O3 nanoparticles fall off rapidly, which is related to continuous growth of solid electrolyte interphase (SEI). Amazingly, the capacities show an upturn in extended cycles. The pseudocapacitance of activated capacities is revealed by executing cyclic voltammetry (CV) tests at various scan rates on 500-cycled Fe2O3 electrodes. Based on electrochemical results, we speculate this special cycling performance of Fe2O3 nanoparticles may be associated with reversible electrochemical processes of SEI under the catalysis of nano-size Fe. Further, 500-cycled Fe2O3 anodes are reassembled with activated carbon cathodes for Li-ion capacitors (LICs). The LICs show energy densities of 110 Wh kg−1 at power densities of 136 W kg−1, and 72.8% capacity retention after 3000 cycles at 2 A g−1. We report an interesting electrochemical behavior of porous Fe2O3 nanoparticles, and a high-performance LIC based on activated Fe2O3 as an anode. This work may offer a new understanding for lithium storage capacities of metal oxide anodes.

Electrochemical systems equipped with 2D and 3D microwave-made anodes for the highly efficient degradation of antibiotics in urine

This work focuses on the importance of choosing a suitable electrochemical cell to remove antibiotics from urines. For this purpose, we investigate the use of two electrochemical cells for electrolysis and photo-electrolysis of urine polluted with a mixture of Penicillin G, Meropenem, and Chloramphenicol. The two reactors studied were a conventional flow pass electrochemical cell (E-cell) and a microfluidic flow-through reactor (MF-Reactor). Both reactors are equipped with a mixed metal oxide anode (MMO-RuO2IrO2) produced by hybrid heating using microwaves. The MMO coating was deposited on a Ti plate for the E-cell (2-D electrode) and on a Ti foam for the MF-Reactor (3-D electrode). Results demonstrate that the MF-Reactor stands out to reduce two important factors in electrochemical oxidation, the ohmic resistance associated with the microfluidic concept and the mass transfer limitations associated with the flow-through configuration. Moreover, it allows operating at a lower effective current density because of its larger active anodic surface area. Photo-electrolysis results in faster removal of all antibiotics studied in the MF-Reactor and E-cell, compared to the single electrolysis, thereby highlighting the significance of UV light-mediated electrochemical oxidation processes. This work highlights that despite the large number of papers focused on the selection of suitable electrodes for the electrochemical treatment of different types of wastes, the choice of the electrochemical cell can be even more important than the selection of those electrode materials, and it demonstrates that even using the same coating as the anode, highly different outcomes can be reached.

Treatment of intermediate landfill leachate using different anode materials in electrooxidation process

AbstractThis study aims to investigate the performances of widely used anode materials in the treatment of intermediate landfill leachate treatment by electrooxidation (EO) process. The raw leachate was collected from an 8‐year‐old landfill facility and had a chemical oxygen demand (COD) of 4660 mg/L, biological oxygen demand (BOD5) of 1370 mg/L, and total organic carbon (TOC) of 2260 mg/L. TOC and COD removal efficiencies of Boron‐Doped Diamond (BDD), Pt, and four different Ti‐based mixed metal oxide (MMO) anodes ((RuO2–TiO2, RuO2–IrO2, PtO2–IrO2, and IrO2–Ta2O5) were compared at the current densities of 25 mA/cm2, 75 mA/cm2, and 125 mA/cm2. At the highest current density, the BDD achieved 100% TOC and COD removal efficiencies in 240 min. BDD was followed by the Pt anode, which achieved 95.53% COD and 92.74% TOC removal efficiencies. The Pt electrode also had the lowest SEC values at all current densities. Although the performances of four MMO electrodes were very close, RuO2–TiO2 achieved a slightly higher performance than the others. It was concluded that Pt anode can be a promising alternative to BDD, which was 18 times more expensive, with its comparable pollutant removal performance and low specific energy consumption.

Mixed metal oxide anodes used for the electrochemical degradation of a real mixed industrial wastewater

Mixed industrial wastewaters are often highly contaminated with heavy metals and organic pollutants. Treating these mixed wastewaters requires many stagewise unit operations. Our work investigates using an electrochemical oxidation-in-situ coagulation (ECO-IC) process as a pre-treatment step toward the efficient treatment of real mixed industrial wastewater rich with heavy metals and organic contaminants. The process degraded organic contaminants in the wastewater via anodic electrochemical oxidation. Simultaneously, heavy metals were precipitated in the solution by coagulants (iron hydroxides) formed in-situ by cathode-generated hydroxyl ions reacting with the significant amounts of dissolved iron in the wastewater. IrO2–RuO2 mixed metal oxide anodes were identified as the best electrodes for organic compound degradation demonstrating 97% degradation of methyl orange (MO) as a model compound within 15 min. These anodes were used to treat real industrial wastewater produced from the industrial cleaning of train tanker cars transporting industrial solvents. The electrochemical treatment experiments resulted in a treated solution with a lower heavy metal content, achieving 96% reduction in Fe and 30% reduction in As content. Only moderate decreases in organic content were observed up to a maximum of 13% reduction in total organic carbon after 1 h of treatment. Electrochemical treatment of the mixed industrial wastewater produced greater effective diameter of the suspended particles and distinct sediment, liquid, and suspended foam phases that could be easily separated for further treatment. ECO-IC shows promise as an efficient and chemical-free method to coagulate heavy metals in real industrial wastewaters and could be an effective pre-treatment in their separation.

ZnSe/CoSe/NCDPH composites as anode materials for lithium ion batteries with high capacity and long cycle

In this paper, dopamine hydrochloride (DPH) is introduced to synthesize ZIF-8@ZIF-67@DPH in the preparation of ZIF-8@ZIF-67. ZnSe/CoSe/NCDPH (N-doped carbon) composites are calcined in a high-temperature inert atmosphere with ZIF-8@ZIF-67@DPH as the precursor, selenium powder as the selenium source. ZnSe/CoSe/NCDPH has high discharge specific capacity, good cycle stability and outstanding rate performance. The first discharge capacity of ZnSe/CoSe/NCDPH is 1616.6 mAh g−1 at the current density of 0.1 A g−1, and the reversible capacity remains at 1214.2 mAh g−1 after 100 cycles, the reversible capacity is 416.7 mAh g−1 after 1000 cycles at 1 A g−1. Therefore, ZnSe/CoSe/NCDPH composites provide a new step for the research and synthesis of new stable, high-capacity, and safe high-performance lithium ion batteries. The bimetallic selenide composites not only have bimetallic active sites, but also can form synergistic effect between different metal phases, which can effectively reduce the capacity attenuation caused by volume expansion and reactive stress enrichment during lithium storage of metal oxide anode materials. Meanwhile, N-doped carbon can improve the conductivity and provide more active sites to store lithium, thus improving its lithium storage capacity.

Sequential Reductive/oxidative Bioelectrochemical Process for Groundwater Perchloroethylene Removal

Chlorinated aliphatic hydrocarbons (CAHs) are common groundwater contaminants, microbial communities naturally present in groundwater can reduce CAHs as perchloroethylene (PCE) and trichloroethylene (TCE) to ethylene through reductive dechlorination (RD) reaction while low chlorinated CAHs like cis-dichloroethylene (cis DCE) and vinyl chloride (VC) can be oxidized by aerobic pathways. A combination of reductive and oxidative dechlorination results an effective strategy for the complete mineralization of CAHs. Bioelectrochemical systems (BES) are innovative processes which can be adopted to stimulate both reductive and oxidative dechlorination biomass through polarized electrodes. The present study describes the performances of a an oxidative bioelectrochemical reactor composed by a membrane-less microbial electrolysis cell (MEC) equipped with an internal graphite counterelectrode. In the oxidative reactor the oxygen provided by a mixed metal oxides (MMO) anode stimulated the oxidative dechlorination of the cisDCE contained in synthetic groundwater. Throughout the experimental period, both reductive and oxidative dechlorination pathways were identified due to presence of an internal counter electrode that acted as electron donor. Reductive and oxidative bioelectrochemical reactions, including anions reduction were determined and their relative contribution to the overall flowing current has been quantified in terms of oxidative and reductive coulombic efficiencies.

Porous carbon assisted carbon nanotubes supporting Fe3O4 nanoparticles for improved lithium storage

Herein, to efficiently improve the lithium storage of Fe3O4 nanoparticles, a distinctive porous carbon (PC) assisted carbon nanotubes (CNTs) supporting architecture has been designed and fabricated successfully. The Fe3O4 nanoparticles are deposited on the surface of CNTs and then covered by an extra PC. In such a designed architecture, highly conductive and robust CNTs can not only improve the conductivity but also boost the structure of the as-fabricated Fe3O4-based composite (CNTs@Fe3O4@PC). In particular, the foam-like PC has a certain level of volume elasticity and open tunnel-like structure to better anchor the Fe3O4 nanoparticles on the surface of CNTs and facilitate the transfer of electrons and ions, therefore guaranteeing the fast kinetics and long-term stability. The results show that the capacitive contribution is predominant in lithium storage of the CNTs@Fe3O4@PC electrode. Consequently, the as-fabricated CNTs@Fe3O4@PC shows high capacity, good rate capability, and long life, displaying 766 and 572 mAh g-1 after 400 and 700 cycles at 200 and even 1000 mA g-1, respectively. Thus outstanding performance makes the CNTs@Fe3O4@PC have great potential to be advanced lithium-ion battery anode materials. Furthermore, this strategy can be extended to other nanostructured metal oxide anodes, such as CoO, SnO2, and Bi2O3 nanomaterials.

(Invited) Disordered Rock-Salt Li3+XV2O5: A High-Rate Anode for Lithium-Ion Batteries

Rechargeable lithium-ion batteries with high energy density that can be safely charged and discharged at high rates are desirable for electrified transportation and other applications. However, the sub-optimal intercalation potentials of current anodes result in a trade-off between energy density, power and safety. Here we report that disordered rock salt Li3+x V2O5 can be used as a fast-charging anode that can reversibly cycle two lithium ions at an average voltage of about 0.6 volts versus a Li/Li+ reference electrode. The increased potential compared to graphite reduces the likelihood of lithium metal plating if proper charging controls are used, alleviating a major safety concern (short-circuiting related to Li dendrite growth). In addition, a lithium-ion battery with a disordered rock salt Li3V2O5 anode yields a cell voltage much higher than does a battery using a commercial fast-charging lithium titanate anode or other intercalation anode candidates (Li3VO4 and LiV0.5Ti0.5S2). DFT calculations reveal that lithium is displaced from stable octahedral sites to less stable tetrahedral sites, resulting in a suppression of the voltage. The crystal structure is well maintained throughout the process with a maximum volume change of 5.9%. This gives rise to exceptional cycling stability, with negligible capacity decay after 6000 cycles. Further, the material is shown to have exceptional rate capabilities, delivering over 40 per cent of its capacity in 20 seconds. Theoretical calculations unveil unique lithium redistribution mechanisms that are responsible for the high rate capability. At the beginning of Li insertion into Li3V2O5, diffusion of Li takes place by a concerted t-o-t mechanism where tetrahedral Li pushes its neighboring octahedral Li to another tetrahedral sites. At the end of the insertion process, direct tetrahedron to tetrahedron (t-t) diffusion is preferred. Both of these mechanism feature low activation energy values which result in rapid lithium diffusion and exceptional rate capabilities. This low-potential, high-rate intercalation reaction can be used to identify other metal oxide anodes for fast-charging, long-life lithium-ion batteries.

ZnMn2O4 spheres anchored on jute porous carbon for use as a high-performance anode material in lithium-ion batteries

As anodes of lithium-ion batteries, transition metal oxide materials have been considerably studied due to their high theoretical specific capacities. However, their poor conductivities and the disintegration of their structures due to volume changes when charging and discharging have restricted the development of transition metal oxide anode materials in lithium-ion batteries. In this work, a novel ZnMn2O4 sphere/jute porous carbon composite material is prepared and displays a high capacity of 1501.6 mA h g−1 after 200 cycles at a current density of 0.2 C (1 C = 784 mA g−1). At a current density of 2 C, it still has a capacity of 701.9 mA h g−1 and no capacity loss for 1000 cycles. The reason for this excellent cycling stability is that the anode material has formed a special structure of ZnMn2O4 spheres composited with jute biomass porous carbon during the preparation process. Biomass porous carbon can promote charge transfer and reduce the volume change of ZnMn2O4. This work proposes an approach to prepare an environmentally friendly, high-performance lithium-ion battery anode material.

Research progress of transition metal oxide anode materials for lithium-ion batteries

Research progress of transition metal oxide anode materials for lithium-ion batteries

Outstanding performance of the microwave-made MMO-Ti/RuO2IrO2 anode on the removal of antimicrobial activity of Penicillin G by photoelectrolysis

This paper studies the applicability of a novel microwave-prepared mixed metal oxide (MMO-Ti/RuO2IrO2) anode in the electrolysis and photo-electrolysis of synthetic urine intensified with Penicillin G. Results are compared with those obtained using boron-doped diamond (BDD) as the anode. In general, electrolysis with both anodes are effective in terms of penicillin removal, and the combination with UV radiation shows a clear synergistic effect on the degradation of Penicillin G: 420% and 355% using MMO and BDD, respectively. The outstanding performance of the MMO-Ti/RuO2IrO2 anode is demonstrated by the decrease in toxicity and the reduction of the antibiotic effect on the urine observed during photo-electrolysis. Notably, photo-electrolysis using the MMO-Ti/RuO2IrO2 anode generates solutions with almost zero residual toxicity and without antibiotic effect, with lower specific energy consumption than using BDD anode. The remarkable performance of the microwaves-prepared MMO-Ti/RuO2IrO2 coatings makes them very promising for being used in the electrochemical treatment of sanitary wastes.

Study of synergetic effects of ternary transition metal in the electrochemical performance of metal oxides anode for lithium-ion battery

Synergistic effect improves the electrochemical properties of metal oxide anode materials for lithium ion-batteries. The influence of different ratios of nickel and manganese on the microscopic morphology and the contribution of pseudocapacitance were investigated. The ternary Prussian blue analog NixMny[Fe(CN)6]2(x + y = 3) manufactured by adjusting the ratio of Ni-Mn mixed salt was used to obtain the ternary transition metal oxide. When the ratio of Ni and Mn is 8:2 or 2:8, the synergistic effect of oxide anode materials between the ternary transition metals is strong. The corresponding materials have excellent cycle stability, higher reversible capacity, lower charge transfer resistance and higher proportion of pseudocapacitance contribution. The calcined product is NiFe2O4-FeMnO3, which has a core-shell structure when the ratio of Ni and Mn is 2:8, and the first cycle discharge capacity is 1697.6 mAh/g. It can provide a reversible capacity 536.1 mAh/g after 500 cycles at 500 mA/g. The analysis of electrode dynamics shows that the pseudocapacitance contribution can reach 46.8% at 0.1 mV/s.

High-stability Mn–Co–Ni ternary metal oxide microspheres as conversion-type anodes for sodium-ion batteries

For sodium-ion batteries (SIBs), the electrochemical process for electrodes involves ion transport in the solid electrolyte interphase (SEI) and active materials. Generally, the large ion radius of Na+ is often considered as the key factor in poor electrode kinetics. However, for conversion-type metal oxide anodes with low redox potentials, unstable SEIs as well as the corresponding kinetic barrier also have significant effects on electrochemical behaviors and deserve more attention. Herein, porous and micro-spherical (Mn0.6Co0.3Ni0.1)3O4 is tailored as a SIB anode using co-precipitation. A high Mn percentage is beneficial to the formation of a micro-spherical morphology during co-precipitation. Due to its lack of electrochemical activity, Mn also contributes to the morphological stability of active materials during cycling. This allows for a clear observation regarding morphological changes of SEI products generated at the electrode surface. It is revealed that branch-like products are gradually converted into a dense interphase layer at electrode surfaces during cycling. The unstable and uneven topography of these electrode surfaces generates kinetic barriers that account for low rate capacities of the as-obtained (Mn0.6Co0.3Ni0.1)3O4 materials. The synthesized metal oxide is able to retain 98.1% of its initial sodiation capacity after 2000 cycles at 0.5 A g−1.

Hierarchical Triple‐Shelled MnCo2O4 Hollow Microspheres as High‐Performance Anode Materials for Potassium‐Ion Batteries

Metal oxide anode materials generally possess high theoretical capacities. However, their further development in potassium-ion batteries (KIBs) is limited by self-aggregation and large volume fluctuations during charge/discharge processes. Herein, hierarchical MnCo2 O4 hollow microspheres (ts-MCO HSs) with three porous shells that consist of aggregated primary nanoparticles are fabricated as anode materials of KIBs. The porous shells are in favor of reducing the diffusion path of K-ions and electrons, and thus the rate performance can be enhanced. The unique triple-shelled hollow structure is believed to provide sufficient contact between electrolyte and metal oxides, possess additional active storage sites for K-ions, and buffer the volume change during K-ions insertion/extraction. A high specific capacity of 243mAhg-1 at 100mAg-1 in the 2nd cycle and a highly improved rate performance of 153mAhg-1 at 1Ag-1 are delivered when cycled between 0.01 and 3.0V. In addition, the transformation of substances during charging/discharging processes are intuitively demonstrated by the in situ X-ray diffraction strategy for the first time, which further proves that the unique structure of ts-MCO HSs with three porous shells can significantly enhance the potassium ions storage performance.

High lithium storage performance of CoO with a distinctive dual-carbon-confined nanoarchitecture.

Herein, a distinctive dual-carbon-confined nanoarchitecture, composed of an inner highly conductive, robust carbon nanotube (CNT) support and outer well-designed porous carbon (PC) coating, was demonstrated to efficiently improve the electrochemical properties of CoO nanoparticles for the first time, and the CoO nanoparticles were confined between the CNTs and porous carbon. The well-designed porous carbon coating showed significant superiority compared to common non-porous carbon coatings, due to its distinctive characteristics such as high flexibility, rich free space and open tunnel-like structure. Therefore, the synergistic effects of the CNT core and the porous carbon sheath endowed the CoO-based composite (CNTs@CoO@PC) with improved electrochemical reaction kinetics, large pseudocapacitive contribution and superior structural stability. As a result, the CNTs@CoO@PC showed outstanding performance with 1090, 571 and 242 mA h g-1 at 200, 1000 and 5000 mA g-1 after 300, 600 and 1000 cycles, respectively. Furthermore, this strategy may be used to improve other metal oxide anode materials for lithium storage.

Two‐dimensional Fe2O3/TiO2 Composite Nanoplates with Improved Lithium Storage Properties as Anodic Materials for Lithium‐Ion Full Cells

AbstractThe rapid capacity decay is one of the challenges for the anodes of metal oxides‐based lithium‐ion batteries (LIBs). Herein, we report a characteristic nanoplate‐structured metal oxide anode consisting of hexagonal Fe2O3 and TiO2 (denoted as Fe2O3/TiO2) via a facile hydrothermal strategy. Owing to two‐dimensional (2D) structured and stable TiO2 modifier, Fe2O3/TiO2 composite demonstrates significantly improved electrochemical LIBs performances. The Fe2O3/TiO2 composite material buffers the volume expansion of Fe2O3 and improves the rate capability and cycling performances. Upon 1000 long‐term cycles, the anode electrode delivers high discharge capacity of 1056 mAh g−1 at 0.5 A g−1. The full cell that is composed of Fe2O3/TiO2 as the anode and commercial LiFePO4 as the cathode delivers superior rate capacity (84 mAh g−1 at 2 A g−1) and stable cycle capacity (132 mAh g−1 at 0.1 A g−1 after 150 cycles). This 2D composite nanostructure offers an approach to improve the metal oxide‐based anodes of LIBs.

Silicon nanoparticle self-incorporated in hollow nitrogen-doped carbon microspheres for lithium-ion battery anodes

In this study, Silicon nanoparticles (Si NPs) were homogeneously self-incorporated into melamine–formaldehyde resin microspheres using a facile hydrothermal technique, followed by annealing the precursors to form hollow nitrogen-doped carbon microspheres (hNC MSs) containing approximately 10.8 wt.% Si NPs (Si@hNC MSs). Melamine was directly polymerized with formaldehyde, providing N and C sources for Li-ion battery anodes. Electrochemical tests demonstrated that the Si@hNC MS anode delivered a high reversible capacity of 872 mAh g–1 at a current density of 200 mA g–1 after 360 cycles. The hNC MSs largely limited the Si volumetric changes caused by repeated charging and discharging, resulting in the high electrochemical stability of the Si anode. This work demonstrates that melamine–formaldehyde resins can be used directly as C and N sources and can effectively mitigate the Si volumetric expansion. Moreover, we believe that this unique resin, an effective C source, has promising potential for improving the electrochemical performance of other metal or metal-oxide anodes.

Optimizing RuOx−TiO2 composite anodes for enhanced durability in electrochemical water treatments

Metal oxide anode electrocatalysts are important for an effective removal of contaminants and the enhancement of electrode durability in the electrochemical oxidation process. Herein, we report the enhanced lifetime of RuOx−TiO2 composite anodes that was achieved by optimizing the fabrication conditions (e.g., the Ru mole fraction, total metal content, and calcination time). The electrode durability was assessed through accelerated service lifetime tests conducted under harsh environmental conditions, by using 3.4% NaCl and 1.0 A/cm2. The electrochemical characteristics of the anodes prepared with metal oxides having different compositions were evaluated using cyclic voltammetry, electrochemical impedance spectroscopy, and X-ray analyses. We noticed that, the larger the Ru mole fraction, the more durable were the electrodes. The RuOx−TiO2 electrodes were found to be highly stable when the Ru mole fraction was >0.7. The 0.8RuOx−0.2TiO2 electrode was selected as the one with the most appropriate composition, considering both its stability and contaminant treatability. The electrodes that underwent a 7-h calcination (between 1 and 10 h) showed the longest lifetime under the tested conditions, because of the formation of a stable Ru oxide structure (i.e., RuO3) and a lower resistance to charge transfer. The electrode deactivation mechanism that occurred due to the dissolution of active catalysts over time was evidenced by an impedance analysis of the electrode itself and surface elemental mapping.

Lithiation mechanism of W18O49 anode material for lithium-ion batteries: Experiment and first-principles calculations

Abstract Tungsten-based materials are very promising anode materials for lithium-ion batteries. Their lithiation processes involve two types of reactions, intercalation and conversion reactions, which occur sequentially according to the degree of lithiation. However, the boundary between these two reactions and their effects on the overall electrochemical performance still need more in-depth understanding and description. Herein, an X-ray diffraction and first-principles calculation were combinedly implemented to reveal the lithiation processes of the monoclinic W18O49. The transformation between intercalation and conversion reactions was found to be dependent on the number of intercalated Li atoms. The in-situ XRD analysis shows structural phase transformations occurred as the deep charge-discharge was performed, which corresponding to the structure of LixW18O49 (x > 22) revealed by the first-principles calculation. Moreover, excellent stability of battery capacity was found in the shallow charge-discharge, whereas not in the deep charge-discharge. Based on this study, we comprehensively deciphered the factors that affect the electrochemical performance and reaction mechanism of W18O49 with lithium. We hope this study could contribute to the application of W18O49 and similar transition metal oxide anode materials for lithium ion batteries.