Active electrode material

Abstract

The present invention relates to an active electrode material and a method for producing the active electrode material. Such materials are of interest as active electrode materials for lithium-ion or sodium-ion batteries. The present invention relates to a compound represented by the general formula M1 a Al 1-a M2 b Nb 11-b O 29-c-d Q d The active electrode material is represented by the formula:

Description

[Technical Field]

[0001] The present invention relates to active electrode materials and methods for making active electrode materials.

[0002] Such materials of interest are of interest, for example, as anode materials in lithium-ion batteries and as active electrode materials in lithium-ion or sodium-ion batteries. [Background technology]

[0003] Lithium-ion (Li-ion) batteries are a commonly used type of rechargeable battery, with the global market predicted to grow to $200 billion by 2030. Li-ion batteries are the technology of choice for electric vehicles, which meet multiple requirements from technical capabilities to environmental impact, making a green automotive industry a viable path forward.

[0004] A typical lithium-ion battery consists of multiple cells connected in series or parallel. Each cell usually consists of an anode (negative electrode) and a cathode (positive electrode), separated by a porous, electrically insulating film (called a separator) and immersed in a liquid (called an electrolyte) that allows the transport of lithium ions.

[0005] In most systems, the electrode consists of an electrochemically active material, meaning that it can chemically react with lithium ions to reversibly store and release them in a controlled manner, optionally mixed with conductive additives (such as carbon) and a polymeric binder. A slurry of these components is coated as a thin film onto a current collector (typically a thin foil of copper or aluminum), thus forming the electrode when dried.

[0006] In known Li-ion battery technologies, graphite anodes have safety limitations during battery charging, which poses a major obstacle to their application in high-power electronics, automotive, and industrial applications. Among various promising alternatives recently proposed, lithium titanate (LTO) and niobium mixed oxide are strong candidates to replace graphite as the optimal active material for high-power, fast-charging applications.

[0007] Batteries relying on graphite anodes are fundamentally limited in terms of charge rate. Under nominal conditions, lithium ions intercalate into the anode active material during charging. At high charge rates, the voltage profile of typical graphite is such that overpotential can cause the anode site to fall below 0 V vs. Li / Li+, resulting in lithium ions instead depositing as lithium metal on the graphite electrode surface, a phenomenon known as lithium dendrite electroplating. This results in an irreversible loss of active lithium and therefore a rapid loss of cell capacity. In some cases, these dendritic deposits can grow to such large sizes that they can penetrate the battery separator, shorting the cell. This can trigger catastrophic cell failure, resulting in fire or explosion. Therefore, the most fast-charging batteries with graphite anodes are limited to charge rates of 5–7 C, although many are significantly lower.

[0008] Lithium titanate (LTO) anodes have excellent cycle life because their high potential (1.6 V vs. Li / Li+) prevents dendrite electroplating at high charge rates and their 3D crystalline structure prevents significant volume expansion of the active material during lithium ion intercalation. For these two reasons, LTO cells are generally considered to be safe. However, LTO is a relatively poor electronic and ionic conductor, limiting its high-rate capacity retention and power delivery capabilities unless the material is nano-sized to increase its specific surface area and carbon-coated to enhance its electronic conductivity. This particle-level material engineering increases the porosity and specific surface area of ​​the active material, significantly reducing the packing density achievable in the electrode. This results in a lower electrode density and a higher proportion of electrochemically inactive materials (e.g., binders, carbon additives), significantly reducing gravimetric and volumetric energy densities.

[0009] An important indicator of anode performance is the volumetric capacity (mAh / cm) of the electrode. 3 ), i.e., the amount of charge (i.e., lithium ions) that can be stored per unit volume of the anode. This amount, when combined with the cathode and appropriate cell design parameters, is a key factor in determining the overall battery energy density (Wh / L) on a volumetric basis. The volumetric capacity of an electrode is related to the electrode density (g / cm 3 ), the specific capacity of the active material (mAh / g), and the fraction of active material in the electrode. LTO anodes typically have a relatively low specific capacity (about 165 mAh / g, compared to about 330 mAh / g for graphite), which accounts for the low electrode density mentioned above (typically 2.0 g / cm 3 This, combined with the low percentage of active material (less than 90%), results in a very low volumetric capacity (300 mAh / cm 3 LTO batteries / cells have a low energy density (less than 1000 kJ / year), which results in a low battery energy density and a high cost per kWh in various applications. As a result, LTO batteries / cells are generally limited to niche applications, despite their long cycle life, fast charging capabilities, and high safety.

[0010] Niobium mixed oxide structures have recently attracted interest for use in Li-ion cells. 11 O 29 AlNb has been disclosed as a possible active electrode material (CN107742716B; Louet et al., ACS Appl. Mater. Interfaces 2019, 11, 6, 6089-6096). These studies rely on complex particle-level engineering, purportedly attempting to control particle porosity and morphology, such as nanowire formation, while achieving superior properties. It is believed that the properties of these materials can be improved. For example, these materials may not have sufficient electronic conductivity to enable efficient charge and discharge in commercial Li-ion cells, resulting in excessive impedance. Furthermore, there is still room for improvement in Li-ion capacity and tuning of charge and discharge voltage profiles. Making these improvements described herein, which do not require extensive nanoscale or particle-level engineering or coatings, is a critical step toward low-cost battery materials for mass-market adoption. If these improvements are not addressed, the resulting devices will have excessive electrical resistance, leading to reduced energy density, increased polarization, reduced power density, reduced energy efficiency, and increased cost. Therefore, AlNb 11 O 29 There remains a need to improve the properties of for use in lithium-ion batteries. Summary of the Invention

[0011] In a first aspect, the present invention provides an active electrode material comprising a niobium mixed oxide, the niobium mixed oxide having the composition M1 a Al 1-a M2 b Nb 11-b O 29-c-d Q d wherein M1 is selected from Mg, Ca, Sr, Y, La, Ce, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Fe, Co, Ni, Cu, Zn, Cd, B, Ga, In, Si, Ge, Sn, Pb, P, Sb, Bi and mixtures thereof; M2 is selected from Mg, Ca, Sr, Y, La, Ce, Zr, Hf, V, Ta, Cr, Mo, W, Mn, Fe, Co, Ni, Cu, Zn, Cd, B, Al, Ga, In, Si, Ge, Sn, Pb, P, Sb, Bi and mixtures thereof; Q is selected from F, Cl, Br, I, N, S, Se, and mixtures thereof; 0≦a<0.5, 0≦b≦1, −0.5≦c≦1.45, 0≦d≦1.45, One or more of a, b, and d is not equal to 0.

[0012] The composition of niobium mixed oxide is stoichiometric AlNb11 O29 It will be understood that the present invention does not correspond to AlNb by either incorporating additional cations (M1 and / or M2) and / or forming mixed anions (including O and Q), and optionally creating an induced oxygen deficiency or excess. 11 O 29 It has been found that by modifying the AlNbO2, the resulting material has improved electrochemical properties, especially when used as an anode material. When a>0, the niobium mixed oxide is modified by partial substitution of Al by M1. When b>0, the niobium mixed oxide is modified by partial substitution of Nb by M2. When c≠0, the niobium mixed oxide is modified by oxygen deficiency or excess. When d>0, the niobium mixed oxide is modified by partial substitution of O by Q. As shown by this example, the inventors have found that the material according to the invention has improved electrochemical properties compared to the unmodified "base" AlNbO2. 11 O 29We have found that the specific capacity and specific capacity at high C-rates are improved compared to those of the niobium mixed oxides. These are important results in demonstrating the advantages of the materials of the present invention for use in high-power batteries designed for fast charge / discharge. Furthermore, since 0≦a<0.5, Al is the primary non-Nb cation in the niobium mixed oxides. 3+ Since niobium mixed oxides are not redox active, it is surprising that they have the excellent properties for use as active electrode materials shown by this example. Typical prior approaches have focused on redox active cations as the primary non-Nb cations, e.g., transition metals such as Cr and Fe.

[0013] The active electrode material of the present invention is particularly useful in electrodes, preferably for use in the anodes of lithium-ion or sodium-ion batteries. Accordingly, in a further embodiment of the present invention, the active electrode material of the first aspect comprises a niobium mixed oxide and at least one other component. Optionally, the at least one other component is selected from a binder, a solvent, a conductive additive, a different active electrode material, and mixtures thereof. Such compositions are useful in the manufacture of electrodes. A further embodiment of the present invention is an electrode comprising the active electrode material of the first aspect in electrical contact with a current collector. A further embodiment of the present invention is an electrochemical device comprising an anode, a cathode, and an electrolyte disposed between the anode and the cathode, wherein the anode comprises the active electrode material according to the first aspect, and optionally the electrochemical device is a lithium-ion or sodium-ion battery.

[0014] In a second aspect, the present invention provides a method for producing a niobium mixed oxide as defined in accordance with the first aspect, the method comprising the steps of obtaining one or more precursor materials, mixing the precursor materials to form a precursor material mixture, and heat treating the precursor material mixture in the temperature range of 400°C to 1350°C or 800 to 1350°C, thereby obtaining the niobium mixed oxide. This represents a convenient and efficient way of producing the active electrode material of the first aspect.

[0015] The present invention includes combinations of aspects and features described herein, except where such combinations are expressly disallowed or explicitly avoided.

[0016] The principles of the present invention will now be described with reference to the accompanying drawings. [Brief explanation of the drawings]

[0017]

Figure 1

Figure 2

[0018] Aspects and embodiments of the present invention will now be described with reference to the accompanying drawings. Further aspects and embodiments will be apparent to those skilled in the art. All documents mentioned in this text are incorporated herein by reference.

[0019] The term "niobium mixed oxide" (MNO) may refer to an oxide containing niobium and at least one other cation. MNO materials have a high redox voltage relative to lithium, greater than 0.8 V, allowing for safe, long-life operation, essential for fast charging of battery cells. Furthermore, niobium cations can undergo two redox reactions per atom, resulting in higher theoretical capacity than, for example, LTO. The niobium mixed oxides described herein are generally AlNb 11 O 29 It comes from the basic structure of

[0020] AlNb 11 O 29 is MO derived from ReO3 3-x Preferably, the niobium mixed oxide has the Wadsley-Roth crystal structure. The Wadsley-Roth crystal structure is considered to be a crystallographic off-stoichiometry of the MO3 (ReO3) crystal structure, including crystallographic shear, and the MO 3-xAs a result, these structures typically contain octahedral [MO6] subunits in their crystal structure. MNO materials with these structures are believed to have advantageous properties for use as active electrode materials, for example, in lithium-ion batteries.

[0021] The open, tunnel-like MO3 crystal structure of MNO materials also makes them ideal candidates for achieving high-capacity Li-ion storage and high rates of exchangeable intercalation / deintercalation. The crystallographic off-stoichiometry present in the MNO structure gives rise to Wadsley-Roth crystallographic superstructures. These superstructures, compounded by other properties such as the Jahn-Teller effect and increased crystallographic disorder due to the use of multiple mixed cations, stabilize the crystal, keep the tunnels open during intercalation, and maintain stability, resulting in high lithium diffusion rates (approximately 10 -13 cm 2 s -1 (and reported) allows for very high rate capabilities.

[0022] AlNb 11 O 29 The crystal formula of can be described as having a 3x4x∞ crystallographic block structure composed of [MO6] octahedra, where M is Al or Nb. The Al octahedra may be randomly distributed within the structure or may prefer specific locations such as the edges or corners of the blocks. This equates to one Al cation per block.

[0023] The entire crystalline composition of the materials described herein is preferably charge neutral and thermodynamically favorable to comply with the above description. x O y M x O y-δOxygen-deficient structures, for example by introducing defects at the site of oxygen vacancies, are preferred when reducing the electrical resistivity of the material so that the oxygen vacancies are present. Oxygen-deficient structures can include shear defects. Cation (i.e., Al and Nb) or anion (i.e., O) substituted structures can be done so with matching valences (i.e., 5+ cations for equal proportions of 4+ and 6+ cations) or with mismatched valences, which can induce oxygen deficiencies or excesses if substitutions are made at equivalent crystal sites. Substitutions can also occur at different crystal sites, such as intermediate sites.

[0024] The crystalline structure of a material can be determined by analyzing X-ray diffraction (XRD) patterns, as is widely known. For example, the XRD pattern obtained from a particular material can be compared to known XRD patterns to confirm the crystalline structure via a public database, such as the ICDD Crystallographic Database. Rietveld analysis can also be used to determine the crystalline structure of a material, particularly the unit cell parameters. Thus, the active electrode material may have a Wadsley-Roth crystalline structure as determined by X-ray diffraction.

[0025] Preferably, the crystal structure of the niobium mixed oxide is determined by X-ray diffraction and is found to be AlNb 11 O 29 This confirms that the "base" material has been modified without significantly affecting the crystal structure, which is believed to have advantageous properties for use as an active electrode material. 11 O 29 The crystal structure of can be found in ICDD crystallographic database entry JCPDS22-009.

[0026] The niobium mixed oxide and cation / anion exchange can have unit cell parameters a, b, and c, where a is 15.52-15.58 angstroms, preferably 15.53-15.57 angstroms, b is 3.79-3.83 angstroms, preferably 3.80-3.82 angstroms, and c is 20.51-20.55 angstroms, preferably 20.52-20.54 angstroms. The niobium mixed oxide can have unit cell parameters α and γ that are each about 90°, preferably α=γ=90°, while β is 113.00-113.70. 0 , preferably 113.05 to 113.68 0 and the unit cell volume is 1116-1120 Å 3 , preferably 1117 to 1119 angstroms 3 The unit cell parameters can be determined by X-ray diffraction. The niobium mixed oxide can have a crystallite size of 5 to 150 nm, preferably 40 to 70 nm, determined according to the Scherrer formula.

[0027] Here, the term "corresponding" is intended to reflect that the peaks in the X-ray diffraction pattern may be shifted by 0.5 degrees or less (preferably by 0.25 degrees or less, more preferably by 0.1 degrees or less) from the corresponding peaks in the X-ray diffraction pattern of the material listed above.

[0028] Niobium mixed oxide has the composition M1 a Al 1-a M2 b Nb 11-b O 29-c-d Q d wherein M1 is selected from Mg, Ca, Sr, Y, La, Ce, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Fe, Co, Ni, Cu, Zn, Cd, B, Ga, In, Si, Ge, Sn, Pb, P, Sb, Bi and mixtures thereof; M2 is selected from Mg, Ca, Sr, Y, La, Ce, Zr, Hf, V, Ta, Cr, Mo, W, Mn, Fe, Co, Ni, Cu, Zn, Cd, B, Al, Ga, In, Si, Ge, Sn, Pb, P, Sb, Bi and mixtures thereof; Q is selected from F, Cl, Br, I, N, S, Se, and mixtures thereof; 0≦a<0.5, 0≦b≦1, −0.5≦c≦1.45, 0≦d≦1.45, One or more of a, b, and d is not equal to 0.

[0029] "and mixtures thereof" is intended to mean that M1, M2, and Q can each represent two or more elements from the individual listings. Examples of such materials are Zn 0.05 Ga 0.05 Al 0.9 Nb 11 O 28.975 where M1 is Zn a‘ Ga a‘‘ (a'+a''=a), a=0.1, b=0, c=-0.025, d=0. Here, c is the oxidation state of each cation, i.e., Zn 2+ , Ga 3+ , Al 3+ The calculations are based on the assumption that

[0030] The exact values ​​of a, b, c, d within the defined ranges can be selected to provide a charge-balanced or substantially charge-balanced crystal structure. Additionally or alternatively, the exact values ​​of a, b, c, d within the defined ranges can be selected to provide a crystal structure that is thermodynamically stable or thermodynamically metastable.

[0031] If an exchange of cations or anions within the structure (i.e., Al, Nb, O) occurs without preserving the original valence, it can create both an oxygen deficiency and an oxygen excess. For example, to some extent Al 3+ Ge 4+ The material substituted by shows a slight excess of oxygen (i.e., Al2O3 vs. GeO2), while Nb 5+Al 3+ The substitution by NbO indicates a mild oxygen deficiency (i.e., Nb2O5 vs. Al2O3). Oxygen deficiency can also be induced by heat treatment under inert or reducing conditions, resulting in the induction of oxygen vacancy defects in the structure.

[0032] There may be partial oxidation or partial reduction that compensates for the exchange, without preserving the original valence. For example, Ge 4+ By Al 3+ The substitution of some Nb 5+ From Nb 4+ This can be at least partially compensated for by reduction of

[0033] M1 is a cation that substitutes for Al in the crystal structure. M1 can be selected from Mg, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Fe, Co, Ni, Cu, Zn, Cd, B, Ga, Si, Ge, Sn, P, and mixtures thereof, preferably Mg, Zr, V, Cr, Mo, W, Mn, Fe, Co, Ni, Cu, Zn, B, Ga, Si, Ge, P, and mixtures thereof, most preferably Mg, Zr, Mo, W, Cu, Zn, Ga, Ge, P, and mixtures thereof. M1 is Al 3+ Optionally, M1 may have a valence different from Al. This results in an oxygen deficiency or excess. 3+ has a valence equal to or lower than that of, and preferably has a valence lower than that of.

[0034] M1 may also be selected from each of the specific elements used in the examples by itself, for example, M1 is preferably Ga.

[0035] When more than one element is present as M1 or M2, it is understood that the valence refers to M1 or M2 as a whole. For example, if 25 at% of M1 is Zr and 75 at% of M1 is W, then the valence of M1 is 0.25 × 4 (contribution from Zr) + 0.75 × 6 (contribution from W).

[0036] M1 is Al 3+Preferably, the ionic radii of the niobium ions have an ionic radius different from, and most preferably larger than, the ionic radii of AlNb. This causes a change in the unit cell dimensions, resulting in local distortions in the crystal structure and providing the benefits described herein. The ionic radii referred to herein are Shannon's ionic radii (available in R.D. Shannon, Acta Cryst., A32, 1976, 751-767) for the coordination and valence that the ions are expected to adopt in the crystal structure of niobium mixed oxides. For example, AlNb 11 O 29 The crystal structure of 5+ O6 octahedrons are included. Therefore, if M2 is Zr, the ionic radius is 6-coordinate Zr 4+ This is considered to be the ionic radius of AlNb 11 O 29 This is because this is the typical valence and coordination of Zr when substituting Nb.

[0037] The amount of M1 is determined by a, which satisfies the criteria 0≦a<0.5.a. a can be 0≦a≦0.4, preferably 0≦a≦0.2. Most preferably, a>0, for example, a≧0.01. M1 is Al 3+ When M1 has the same valence as M1, higher values ​​of a can be more easily achieved. When M1 contains a cation with a valence of 3+ (e.g., Ga), a can be 0≦a<0.5. When M1 does not contain a cation with a valence of 3+, a can be 0≦a≦0.1.

[0038] M2 is a cation that substitutes for Nb in the crystal structure. M2 can be selected from Mg, Zr, Hf, V, Ta, Cr, Mo, W, Mn, Fe, Co, Ni, Cu, Zn, Cd, B, Al, Ga, Si, Sn, P, and mixtures thereof, preferably Mg, Zr, V, Cr, Mo, W, Mn, Fe, Co, Ni, Cu, Zn, Cd, B, Al, Si, P, and mixtures thereof, most preferably Zr, V, Cr, Mo, W, Fe, Cu, Zn, Al, P, and mixtures thereof. M2 is Nb 5+ This results in an oxygen deficiency or excess. Preferably, M2 is Nb5+ It has a lower valence, which creates an oxygen deficiency, i.e., the presence of oxygen vacancies, which provides the benefits discussed herein.

[0039] M2 can also be selected from each of the specific elements used by itself in the examples.

[0040] M2 is Nb 5+ Preferably, the ionic radius is different from, and most preferably larger than, , which causes a change in the unit cell dimensions and local distortions in the crystal structure, resulting in the benefits described herein.

[0041] The amount of M2 is determined by b, which satisfies the criterion 0≦b≦1, and b may be 0≦b≦0.5, preferably 0≦b≦0.1. In each of these cases, b>0, for example b≧0.01. 5+ If M2 has the same valence as M, then higher values ​​of b can be more easily achieved. If M2 contains a cation with a valence of 5+ (e.g., Ta), then b can be 0≦b≦1. If M2 does not contain a cation with a valence of 5+, then b can be 0≦b≦0.05.

[0042] Optionally, both a and b are > 0. When both a and b are > 0, the "base" material is substituted at both Al sites and Nb sites.

[0043] c reflects the oxygen content of the niobium mixed oxide. If c is greater than 0, it forms an oxygen-deficient material, i.e., the material has oxygen vacancies. Such a material is considered "substantially charge-balanced" as described above, although it does not have a precise charge balance without changing the oxygen state of the cations. Alternatively, c can be equal to 0, in which case it is not an oxygen-deficient material. c can be less than 0, in which case it is an oxygen-rich material. c can be -0.25≦c≦1.45.

[0044] When c is 1.45, the number of oxygen vacancies is equal to 5% of the total oxygen in the crystalline structure. c can be greater than 0.0145, greater than 0.029, greater than 0.0435, or greater than 0.145. c can be between 0 and 1, between 0 and 0.75, between 0 and 0.5, or between 0 and 0.25. For example, c can satisfy 0.01≦c≦1.45. When a material is oxygen-deficient, e.g., oxygen deficiency is induced, the electrochemical properties of the material can be improved, e.g., electrical conductivity can be improved in resistance measurements compared to a comparable non-oxygen-deficient material. As will be understood, percentage values ​​expressed herein are atomic percentages.

[0045] The present invention relates to niobium mixed oxides that may contain oxygen vacancies (oxygen-deficient niobium mixed oxides) or may have an oxygen excess. Oxygen vacancies can be formed in niobium mixed oxides by the substitution of secondary valences of the base material as described above, and oxygen excess can be formed in niobium mixed oxides by the substitution of increased valences. Oxygen vacancies can also be formed by heating niobium mixed oxides under reducing conditions, which can be referred to as the formation of induced oxygen deficiencies. The amount of oxygen vacancies and excess is determined based on the total amount of oxygen in the base material, i.e., the amount of oxygen in the unsubstituted material (e.g., AlNb 11 O 29 ) can be expressed relative to the amount of oxygen.

[0046] Many methods exist for determining whether oxygen deficiencies, e.g., oxygen vacancies, exist in a material. For example, thermogravimetric analysis (TGA) can be performed to measure the mass change of a material when heated in an air atmosphere. Materials containing oxygen vacancies can gain mass when heated in air as the material "reoxidizes" and the oxygen vacancies are filled with oxide anions. The magnitude of the mass increase can be used to quantify the concentration of oxygen vacancies in the material. This assumes that the mass increase occurs due to the complete filling of oxygen vacancies. Note that materials containing oxygen vacancies may experience an initial mass increase as the oxygen vacancies are filled, followed by a mass loss at higher temperatures as the material undergoes thermal decomposition. Furthermore, the mass loss and mass gain processes can overlap; that is, some materials containing oxygen vacancies may not exhibit a mass increase (and in some cases, neither a mass loss nor a mass gain) during TGA analysis.

[0047] Other methods for determining whether oxygen deficiencies, such as oxygen vacancies, are present include Raman spectroscopy, electron paramagnetic resonance (EPR), X-ray photoelectron spectroscopy (XPS, e.g., oxygen 1s XPS and / or cation XPS of mixed oxides), X-ray absorption near edge structure (XANES, e.g., cation XANES of mixed metal oxides), and TEM (e.g., scanning TEM (STEM) with high angle annular dark field (HAADF) and annular bright field (ABF) detector). The presence of vacancies can also be inferred from the properties, e.g., electrical conductivity, of stoichiometric materials compared to the properties of oxygen-deficient materials.

[0048] When d>0, additional anions Q are introduced into the niobium mixed oxides. Their electronic structures are different (i.e., F - vs. O 2- ), and the ionic radius is different (6 coordinates O 2- = 1.40 Å, 6 coordinates F -= 1.33 Å), they can improve the electrochemical performance of the active material. This is because different ionic radii modify the unit cell properties, allowing for improved Li-ion capacity or improved reversibility. They can further improve electrical conductivity by modifying the electronic structure of the crystal (i.e., doping effect), with respect to oxygen vacancy defects or subvalent cation substitution. d can be 0≦d≦1.0, or 0≦d≦0.7. In each of these cases, d can be greater than 0, e.g., d≧0.01. Q can be selected from F, Cl, N, S, and mixtures thereof, or F, N, and mixtures thereof, or Q is F.

[0049] Optionally, d=0, in which case the material has composition M1 a Al 1-a M2 b Nb 11-b O 29-c where M1, M2, a, b, and c are as defined herein. Advantageously, materials with d=0 do not contain an anion Q and may be easier to synthesize.

[0050] When a>0 and b=d=0, the substance is M1 a Al 1-a Nb 11 O 29-c where M1, a, and c are as defined herein, e.g., 0≦c≦1.45. This represents a material modified at the Al site, optionally modified by induced oxygen deficiency. Such a material can be prepared by simple synthetic means from the "base" oxide Alnb 11 O 29 This represents a particularly effective way of improving the properties of, where M1 can represent Mg, V, Cr, W, Zr, Mo, Cu, Ga, Ge, Ni, Hf, Ta, Zn and mixtures thereof, preferably Mg, V, Cr, W, Zr, Mo, Ga, Ge, Zn and mixtures thereof.

[0051] It should be understood that the discussion of the compositional variables (M1, M2, Q, a, b, c, and d) are intended to be read in combination. For example, preferably, M1 is selected from Mg, Zr, V, Cr, Mo, W, Mn, Fe, Co, Ni, Cu, Zn, B, Ga, Si, Ge, P, and mixtures thereof; M2 is selected from Mg, Zr, V, Cr, Mo, W, Mn, Fe, Co, Ni, Cu, Zn, Cd, B, Al, Si, P, and mixtures thereof; and Q is selected from F, Cl, N, S, and mixtures thereof. Preferably, 0≦a≦0.4, 0≦b≦0.5, 0≦c≦1.45, and 0≦d≦1.0.

[0052] For example, niobium mixed oxide has the composition M1 a Al 1-a M2 b Nb 11-b O 29-c-d Q d wherein M1 is selected from Mg, Zr, V, Cr, Mo, W, Mn, Fe, Co, Ni, Cu, Zn, B, Ga, Si, Ge, P, and mixtures thereof; M2 is selected from Mg, Zr, V, Nb, Cr, Mo, W, Mn, Fe, Co, Ni, Cu, Zn, Cd, B, Al, Si, P, and mixtures thereof; Q is selected from F, Cl, N, S and mixtures thereof; 0 <a≦0.4、0≦b≦0.5;-0.25≦c≦1.45、0≦d≦1.45である。

[0053] For example, niobium mixed oxide has the composition M1 a Al 1-a Nb 11 O 29-c-d Q d wherein M1 is selected from Mg, Zr, V, Cr, Mo, W, Mn, Fe, Co, Ni, Cu, Zn, B, Ga, Si, Ge, P, and mixtures thereof, preferably M1 is selected from Zr, Cr, Zn, Ga, and mixtures thereof; Q is selected from F, N, and mixtures thereof, preferably Q is F; 0 <a<0.5、0≦c≦1.45、0≦d≦1.45である。

[0054] For example, niobium mixed oxide has the composition M1 a Al 1-a Nb 11 O 29-c-d Q d wherein M1 is selected from Mg, Zr, Mo, W, Cu, Zn, Ga, Ge, P, and mixtures thereof, preferably M1 is selected from Zr, Zn, Ga, and mixtures thereof; Q is selected from F, N, and mixtures thereof, preferably Q is F; 0 <a≦0.2、0≦c≦1.45、0≦d≦1.45である。

[0055] M1, M2, and Q may also be selected from each of the specific elements used as these dopants in the embodiments.

[0056] The niobium mixed oxide may further contain Li and / or Na. For example, Li and / or Na may be incorporated into the crystal structure when the niobium mixed oxide is used in an electrode of a metal-ion battery.

[0057] The niobium mixed oxide is preferably in granular form. The material has a diameter of 0.1 to 100 μm, or 0.5 to 50 μm, or 1 to 20 μm. 50 These particle sizes are advantageous because they are easy to process and manufacture into electrodes. Furthermore, these particle sizes eliminate the need to use complex and / or expensive methods to produce nano-sized particles. Nano-sized particles (e.g., D of 100 nm or less) can be used. 50 (particles having a particle size of 0.01 mm or less) are typically more complex to synthesize and require additional safety considerations.

[0058] The niobium mixed oxide has a D of at least 0.05 μm, or at least 0.1 μm, or at least 0.5 μm, or at least 1 μm. 10 The particle size may be D10 Maintaining particle size within these ranges reduces the likelihood of parasitic reactions in Li-ion cells due to reduced surface area and allows for easier processing, requiring less binder in the electrode slurry.

[0059] Niobium mixed oxides are available in sizes of 200 μm or less, 100 μm or less, 50 μm or less, or 20 μm or less. 90 The particle size may be D 90 By maintaining the particle size within these ranges, the proportion of the particle size distribution at larger particle sizes is minimized, making it easier to fabricate the material into a homogeneous electrode.

[0060] The term "particle size" refers to the equivalent spherical diameter (esd), i.e., the diameter of a sphere having the same volume as a given particle, the volume of the particle being understood to include the volume of any intra-particle pores. n " and "D n The term "diameter of particle diameter" refers to the diameter below which n% of the particle population is found. 50 " and "D 50 The term "particle size" refers to the volume-based median particle size below which 50% by volume of the particle population is found. It will be understood that when a material contains primary crystallites aggregated into secondary particles, particle size refers to the diameter of the secondary particles. Particle size can be determined by laser diffraction. Particle size can be measured in accordance with ISO 13320:2009, for example, using Mie theory.

[0061] Niobium mixed oxide is 0.1 to 100m 2 / g, or 0.5 to 50 m 2 / g, or 1 to 20 m 2 The niobium mixed oxide may have a BET surface area in the range of 1 / g. Generally, a low BET surface area is preferred to minimize reaction between the niobium mixed oxide and the electrolyte, for example, to minimize the formation of a solid electrolyte interphase (SEI) layer during the first charge-discharge cycle of an electrode containing the material. However, if the BET surface area is too low, the majority of the niobium mixed oxide will be inaccessible to metal ions in the surrounding electrolyte, resulting in unacceptably low charge rates and capacities.

[0062] The term "BET surface area" refers to the surface area per unit mass calculated from measurements of the physical adsorption of gas molecules on a solid surface using the Brunauer-Emmett-Teller theory. For example, BET surface area can be determined in accordance with ISO 9277:2010.

[0063] The specific capacity / reversible delithiation capacity of the niobium mixed oxide can be 190 mAh / g or greater, or 197 mAh / g or greater, where the specific capacity is defined as measured on the second cycle of a galvanostatic cycling test of the half-cell at a rate of 0.1 C over a voltage range of 1.1 to 3.0 V vs. Li / Li+ in the half-cell. Obtaining a material with a high specific capacity can be advantageous because it can provide improved performance in electrochemical devices containing the niobium mixed oxide.

[0064] According to the description below, when formulated or coated as an electrode (optionally with a conductive carbon additive and binder material), the sheet resistivity of the active electrode material, measured as defined in the Examples, can be 2.5 kΩ per square or less, more preferably 1.2 kΩ per square or less. Sheet resistivity is useful as a surrogate measure of the electronic conductivity of such materials. Providing materials with suitably low sheet resistivity can be advantageous, as it can result in improved performance in electrochemical devices containing niobium mixed oxides.

[0065] Niobium mixed oxide is 10 ー15 cm 2 s -1 Greater than, or more preferably, 10 -13 cm 2 s -1 It may be advantageous to provide a material with a suitably high lithium diffusion rate, as this may result in improved performance in electrochemical devices that include niobium mixed oxides.

[0066] The niobium mixed oxide was formed into a composite electrode with a suitable binder and conductive additive according to the following description, and after calendering, the composite electrode had a density of 2.5 g / cm 3 This allows for composite electrodes with electrode porosities (calculated by the average of the measured electrode density / the true density of each component) in the range of 30-40%, in line with the industrial requirements for high energy and high power cells. For example, up to 2.9 g / cm 3 Electrode densities of 1000 to 150 ...

[0067] The initial coulombic efficiency is measured as the difference between the lithiation capacity and the delithiation capacity, measured as the difference between the lithiation capacity and the delithiation capacity in the first charge / discharge cycle at C / 10 of the half-cell. The initial coulombic efficiency of the active electrode material may be greater than 97.10. Providing a material with a suitably high initial coulombic efficiency can be advantageous, as it can result in improved performance in electrochemical devices containing niobium mixed oxides.

[0068] The active electrode material of the first aspect of the present invention comprises a niobium mixed oxide and at least one other component, optionally selected from a binder, a solvent, a conductive additive, a different active electrode material, and mixtures thereof. Such compositions are useful for making electrodes, such as anodes for lithium-ion batteries. Preferably, the different active electrode material is selected from a different niobium mixed oxide having a composition defined by the first aspect, a lithium titanium oxide, a niobium oxide, and mixtures thereof. Alternatively, the active electrode material may consist of a niobium mixed oxide.

[0069] The active electrode material may comprise a niobium mixed oxide and a lithium titanium oxide, preferably a mixture of a niobium mixed oxide and a lithium titanium oxide.

[0070] The lithium titanium oxide preferably has a spinel or ramsdellite crystal structure, as determined, for example, by X-ray diffraction. An example of a lithium titanium oxide having a spinel crystal structure is Li4Ti5O 12 An example of a lithium titanium oxide with the ramsdellite crystal structure is Li2Ti3O7. These materials have been shown to have excellent properties for use as active electrode materials. Thus, lithium titanium oxide is Li4Ti5O 12 and / or may have a crystal structure as determined by X-ray diffraction corresponding to Li2Ti3O7. Lithium titanium oxide may have a crystal structure as determined by X-ray diffraction corresponding to Li4Ti5O 12 , Li2Ti3O7, and mixtures thereof.

[0071] The lithium titanium oxide can be doped with additional cations or anions. The lithium titanium oxide can be oxygen deficient. The lithium titanium oxide can include a coating, optionally selected from carbon, polymer, metal, metal oxide, metalloid, phosphate, and fluoride.

[0072] The lithium titanium oxide can be synthesized by conventional ceramic techniques, such as solid-state or sol-gel synthesis, or it can be obtained from commercial sources.

[0073] The lithium titanium oxide is preferably in the form of particles. The lithium titanium oxide has a D in the range of 0.1 to 50 μm, or 0.25 to 20 μm, or 0.5 to 15 μm. 50 The lithium titanium oxide may have a particle size D of at least 0.01 μm, or at least 0.1 μm, or at least 0.5 μm. 10 The lithium titanium oxide may have a particle size D of 100 μm or less, 50 μm or less, or 25 μm or less.90 The particle size may be D 90 Maintaining the particle size in this range improves the packing of the lithium titanium oxide particles in admixture with the niobium mixed oxide particles.

[0074] Lithium titanium oxides are typically used in battery anodes with small particle sizes due to the low electronic conductivity of the material. In contrast, niobium mixed oxides as defined herein typically have a higher lithium ion diffusion coefficient than lithium titanium oxides, and therefore can be used with larger particle sizes. Advantageously, in the composition, lithium titanium oxides can have smaller particle sizes than niobium mixed oxides, e.g., the D of niobium mixed oxides. 50 D of lithium titanium oxide versus particle size 50 The particle size ratio of the smaller lithium titanium oxide particles to the larger niobium mixed oxide particles is in the range of 0.01:1 to 0.9:1, or 0.1:1 to 0.7:1, so that the smaller lithium titanium oxide particles can be accommodated in the voids between the larger niobium mixed oxide particles, increasing the packing efficiency of the composition.

[0075] Lithium titanium oxide is 0.1 to 100 m 2 / g, or 1 to 50m 2 / g, or 3 to 30 m 2 The polymer may have a BET surface area in the range of 1 / g.

[0076] The mass ratio of lithium titanium oxide to niobium mixed oxide can be in the range of 0.5:99.5 to 99.5:0.5, preferably in the range of 2:98 to 98:2. In one embodiment, the active electrode material contains a higher ratio of lithium titanium oxide than niobium mixed oxide, for example, a mass ratio of at least 2:1, at least 5:1, or at least 8:1. Advantageously, this allows the niobium mixed oxide to be gradually introduced into existing electrodes based on lithium titanium oxide without the need for significant changes in manufacturing technology, providing an efficient way to improve the properties of existing electrodes. In another embodiment, the active electrode material contains a higher proportion of niobium mixed oxide than lithium titanium oxide, for example, a mass ratio of lithium titanium oxide to niobium mixed oxide of less than 1:2, less than 1:5, or less than 1:8. Advantageously, this allows the cost of the active electrode material to be reduced by replacing part of the niobium mixed oxide with lithium titanium oxide.

[0077] The active electrode material can include niobium mixed oxides and niobium oxides. Niobium oxides include Nb 12 O 29 , NbO2, NbO, and Nb2O5. Preferably, the niobium oxide is Nb2O5.

[0078] Niobium oxide is, for example, a crystalline structure of an oxide consisting of Nb and O, for example, Nb 12 O 29 The niobium oxide may be doped with additional cations or anions, provided that the niobium oxide corresponds to NbO2, NbO, and Nb2O5. The niobium oxide may be oxygen deficient. The niobium oxide may include a coating, optionally selected from carbon, polymer, metal, metal oxide, semi-metal, phosphate, and fluoride.

[0079] Niobium oxide is Nb as determined by X-ray diffraction. 12 O 29, NbO2, NbO, or Nb2O5 crystal structure. For example, niobium oxide can have an orthorhombic Nb2O5 crystal structure or a monoclinic Nb2O5 crystal structure. Preferably, niobium oxide has a monoclinic Nb2O5 crystal structure, and most preferably has a H-Nb2O5 crystal structure. Further information regarding the crystal structure of Nb2O5 can be found in Griffith et al., J. Am. Chem. Soc. 2016, 138, 28, 8888-8899.

[0080] Niobium oxide can be synthesized by conventional ceramic techniques, such as solid-state or sol-gel synthesis, or it can be obtained from commercial suppliers.

[0081] The niobium oxide is preferably in the form of particles. The niobium oxide has a diameter of D in the range of 0.1 to 100 μm, or 0.5 to 50 μm, or 1 to 20 μm. 50 The niobium oxide may have a particle size D of at least 0.05 μm, or at least 0.5 μm, or at least 1 μm. 10 The niobium oxide may have a particle size D of 100 μm or less, 50 μm or less, or 25 μm or less. 90 The particle size may be D 90 Maintaining the particle size in this range improves the packing of the niobium oxide particles in the mixture with the niobium mixed oxide particles.

[0082] Niobium oxide is 0.1 to 100m 2 / g, or 1 to 50m 2 / g, or in the range of 1 to 20 m2 / g.

[0083] The mass ratio of niobium oxide to niobium mixed oxide may be in the range of 0.5:99.5 to 99.5:0.5, or in the range of 2:98 to 98:2, or preferably in the range of 15:85 to 35:55.

[0084] The present invention also provides an electrode comprising the active electrode material of the first aspect of the present invention in electrical contact with a current collector. The electrode may form part of a cell. The electrode may form the anode as part of a metal-ion battery, optionally a lithium-ion battery.

[0085] The present invention also provides the use of the active electrode material of the first aspect of the invention in an anode for a metal-ion battery, optionally wherein the metal-ion battery is a lithium-ion battery.

[0086] A further embodiment of the present invention is an electrochemical device comprising an anode, a cathode, and an electrolyte disposed between the anode and cathode, wherein the anode comprises an active electrode material according to the first aspect of the present invention; and optionally, the electrochemical device is a metal-ion battery, such as a lithium-ion battery or a sodium-ion battery. Preferably, the electrochemical device is a lithium-ion battery having a reversible anode active material specific capacity of greater than 195 mAh / g at 20 mA / g, such that the battery can be charged and discharged at current densities relative to the anode active material of 200 mA / g or greater, or 1000 mA / g or greater, or 2000 mA / g or greater, or 4000 mA / g or greater, while retaining 70% or more of the initial cell capacity at 20 mA / g. It has been found that the use of the active electrode material according to the first aspect of the present invention can enable the fabrication of lithium-ion batteries having this combination of properties, representing lithium-ion batteries particularly suitable for use in applications where high charge and discharge current densities are desired. In particular, the examples showed that the active electrode material according to the first aspect of the present invention has improved electronic conductivity and improved delithiation voltage at high C-rates.

[0087] Niobium mixed oxides can be synthesized by conventional ceramic techniques. For example, the materials can be produced by one or more of solid-state or sol-gel synthesis. The materials can also be synthesized by one or more commonly used alternative techniques, such as hydrothermal or microwave hydrothermal synthesis, solvothermal or microwave solvothermal synthesis, co-precipitation synthesis, spark or microwave plasma synthesis, combustion synthesis, electrospinning, and mechanical alloying.

[0088] A second aspect of the present invention provides a method for producing a niobium mixed oxide as defined according to the first aspect of the present invention, the method comprising the steps of obtaining one or more precursor materials, mixing the precursor materials to form a precursor material mixture, and heat treating the precursor material mixture at a temperature in the range of 400°C to 1350°C or 800 to 1300°C, thereby obtaining the niobium mixed oxide.

[0089] To obtain a niobium mixed oxide containing the element Q, the method may further comprise the steps of mixing the niobium mixed oxide with a precursor containing the element Q to obtain a further precursor material mixture, and optionally heat treating the further precursor material mixture under reducing conditions in a temperature range of 300-1300°C or 800-1200°C, thereby obtaining a niobium mixed oxide containing the element Q.

[0090] For example, to obtain a niobium mixed oxide containing N as the element Q, the method may further comprise the steps of mixing the niobium mixed oxide with a precursor containing N (e.g., melamine) to obtain a further precursor material mixture, and heat treating the further precursor material mixture under reducing conditions (e.g., in N) in a temperature range of 300-1300°C, thereby obtaining a niobium mixed oxide containing N as the element Q.

[0091] For example, to obtain a niobium mixed oxide containing F as the element Q, the method may further comprise the steps of mixing the niobium mixed oxide with a precursor containing F (e.g., polyvinylidene fluoride) to obtain a further precursor material mixture, and heat treating the further precursor material mixture under oxidizing conditions (e.g., in air) at a temperature range of 300-1300°C, thereby obtaining a niobium mixed oxide containing F as the element Q.

[0092] The method may include the further step of heat-treating the niobium mixed oxide or the niobium mixed oxide containing element Q under reducing conditions in the temperature range of 400 to 1350°C or 800 to 1300°C, thereby inducing oxygen vacancies in the niobium mixed oxide. The induced oxygen vacancies may be in addition to oxygen vacancies already present in the niobium mixed oxide, for example, due to secondary valence substitution of Al and / or Nb with M1 and / or M2. Alternatively, the induced oxygen vacancies may be new oxygen vacancies, for example, when M1 and M2 have the same valence as Al and Nb. The presence of the induced oxygen vacancies provides the advantages discussed herein.

[0093] The precursor material can include one or more metal oxides, metal hydroxides, metal salts, or ammonium. For example, the precursor material can include one or more metal oxides or metal salts of different oxidation states and / or different crystal structures. Examples of suitable precursor materials include, but are not limited to, NbO, Nb(OH), niobic acid, NbO, ammonium oxalate niobate, NHHPO, (NH)PO, (NH)PO, (NH)PO, PO, HPO, TaO, WO, ZrO, TiO, MoO, VO, ZrO, CuO, ZnO, AlO, KO, KOH, CaO, GeO, GaO, SnO, CoO, CoO, FeO, FeO, MnO, MnO, NiO, NiO, HBO, ZnO, and MgO. The precursor material may not include a metal oxide or may include an ion source other than an oxide. For example, the precursor material may include a metal salt (e.g., NO - , SO3 -) or other compounds (e.g., oxalates, carbonates). To replace the oxygen anion with another electronegative anion Q, precursors containing element Q can include one or more organic compounds, polymers, inorganic salts, organic salts, gases, or ammonium salts. Examples of suitable precursor materials containing element Q include melamine, NH4HCO3, NH3, NHF 、 Including, but not limited to, PVDF, PTFE, NH4Cl, NH4Br, NH4I, Br2, Cl2, I2, ammonium oxychloride amide, and hexamethylenetetramine.

[0094] Some or all of the precursor materials may be particulate. If they are particulate, they preferably have a diameter of less than 20 μm, for example, a D of 10 nm to 20 μm. 50 The precursor material has an initial particle size of less than 20 μm. Obtaining particulate material with such a particle size can help promote more intimate mixing of the precursor materials, thereby resulting in a more efficient solid-state reaction during the heat-treating step. However, it is not necessary for the precursor material to have an initial particle size of less than 20 μm, as the particle size of one or more precursor materials can be mechanically reduced during the step of mixing the precursor materials to form the precursor material mixture.

[0095] The step of mixing the precursor materials to form the precursor material mixture and / or the further precursor material mixture may be carried out by a process selected from, but not limited to, dry or wet planetary ball milling, rolling ball milling, high energy ball milling, high shear milling, air jet milling, steam jet milling, planetary mixing, and / or impact milling. The force used for mixing / milling may depend on the morphology of the precursor materials. For example, if some or all of the precursor materials are mixed into larger particle sizes (e.g., D greater than 20 μm), the mixing / milling force may be increased. 50When the precursor material has a particle size of 20 μm or less, the milling force can be selected to reduce the particle size of the precursor material mixture so that the particle size of the precursor material mixture is reduced to 20 μm or less in diameter. When the particle size of the precursor mixture particles is 20 μm or less, the solid-state reaction of the precursor material of the precursor mixture can be more efficiently promoted during the heat treatment step. Solid-state synthesis can also be performed on pellets formed from precursor powders at high pressures (greater than 10 MPa).

[0096] The step of heat-treating the precursor material mixture and / or the further precursor material mixture can be carried out for a time period of from 1 hour to 24 hours, more preferably from 3 hours to 18 hours. For example, the heat-treating step can be carried out for 1 hour or more, 2 hours or more, 3 hours or more, 6 hours or more, or 12 hours or more. The heat-treating step can be carried out for 24 hours or less, 18 hours or less, 16 hours or less, or 12 hours or less.

[0097] The step of heat-treating the precursor material mixture can be carried out in a gas atmosphere, preferably air. Suitable gas atmospheres include air, N2, Ar, He, CO2, CO, O2, H2, NH3, and mixtures thereof. The gas atmosphere can also be a reducing atmosphere. If it is desired to produce an oxygen-deficient material, the step of heat-treating the precursor material mixture is preferably carried out in an inert or reducing atmosphere.

[0098] The step of heat treating the further precursor material mixture is carried out under reducing conditions, including under an inert gas such as nitrogen, helium, argon, or a mixture of an inert gas and hydrogen, or under vacuum. Preferably, the step of heat treating the further precursor material mixture comprises heating under an inert gas.

[0099] The further step of heat treating the niobium mixed oxide and / or the niobium mixed oxide containing element Q under reducing conditions can be carried out for a time period of 0.5 to 24 hours, more preferably 2 to 18 hours. For example, the heat treatment step can be carried out for 0.5 hours or more, 1 hour or more, 3 hours or more, 6 hours or more, or 12 hours or more. The heat treatment of the further step can be carried out for 24 hours or less, 18 hours or less, 16 hours or less, or 12 hours or less. Reducing conditions include under an inert gas such as nitrogen, helium, or argon, or under a mixture of an inert gas and hydrogen, or under vacuum. Preferably, heating under reducing conditions includes heating under an inert gas.

[0100] In some methods, it may be beneficial to perform a two-step heat treatment. For example, the precursor material mixture and / or the additional precursor material mixture can be heated at a first temperature for a first time, followed by heating at a second temperature for a second time. Preferably, the second temperature is higher than the first temperature. Such a two-step heat treatment can aid in the solid-state reaction to form the desired crystalline structure. This can be performed consecutively or with an intermediate re-grinding step.

[0101] The method can include one or more post-treatment steps after the formation of the niobium mixed oxide. In some cases, the method can include a post-treatment step of heat-treating the niobium mixed oxide, sometimes referred to as "annealing." This post-treatment heat-treatment step can be performed in a different gas atmosphere than the step of heat-treating the precursor material mixture to form the niobium mixed oxide. The post-treatment heat-treatment step can be carried out in an inert gas atmosphere or a reducing gas atmosphere. Such a post-treatment heat-treatment step can be performed at a temperature above 500°C, for example, about 900°C. Including a post-treatment heat-treatment step can be useful, for example, to create deficiencies or defects in the niobium mixed oxide, such as by inducing oxygen deficiencies, or to perform anion exchange, for example, N exchange of O anions, in the formed niobium mixed oxide.

[0102] The method may include milling and / or classifying the niobium mixed oxide (e.g., impact milling, jet milling, steam jet milling, high energy milling, high shear milling, pin milling, air classification, wheel classification, sieving) to obtain a material having any of the particle size parameters listed above.

[0103] There may be a step of coating the niobium mixed oxide with carbon to improve the electrical conductivity of the surface and prevent reaction with the electrolyte. This typically consists of combining the niobium mixed oxide with a carbon precursor to form an intermediate material, which may involve milling, preferably high-energy milling. Alternatively or additionally, the step may involve mixing the niobium mixed oxide with the carbon precursor in a solvent such as water, ethanol, or THF. These represent efficient ways to ensure uniform mixing of the niobium mixed oxide with the carbon precursor.

[0104] polyaromatic sp 2 It has been found that carbon-containing carbon precursors provide a particularly beneficial carbon coating on the niobium mixed oxide of the first aspect of the invention. Thus, the method for producing a niobium mixed oxide comprises: 2 The method may further include combining the niobium mixed oxide with a carbon precursor comprising carbon to form an intermediate material, and heating the intermediate material under reducing conditions to pyrolyze the carbon precursor and form a carbon coating on the niobium mixed oxide and induce oxygen vacancies in the niobium mixed oxide.

[0105] The intermediate material can contain a carbon precursor in an amount of up to 25 wt%, or 0.1-15 wt%, or 0.2-8 wt%, based on the total weight of the niobium mixed oxide and carbon precursor. The carbon coating on the niobium mixed oxide can be present in an amount of up to 10 wt%, or 0.05-5 wt%, or 0.1-3 wt%, based on the total weight of the niobium mixed oxide. These amounts of carbon precursor and / or carbon coating provide a good balance between improving electronic conductivity through the carbon coating and not excessively reducing the capacity of the niobium mixed oxide by excessively reducing the proportion of niobium mixed oxide. The mass of the carbon precursor lost during pyrolysis can range from 30 to 70 wt%.

[0106] The step of heating the intermediate under reducing conditions may be carried out at a temperature ranging from 400 to 1,200° C., or from 500 to 1,100° C., or from 600 to 900° C. The step of heating the intermediate under reducing conditions may be carried out for a duration ranging from 30 minutes to 12 hours, from 1 to 9 hours, or from 2 to 6 hours.

[0107] The step of heating the intermediate under reducing conditions can be carried out under an inert gas such as nitrogen, helium, argon, or a mixture of an inert gas and hydrogen, or can be carried out under vacuum.

[0108] polyaromatic sp 2 The carbon-containing carbon precursor can be selected from pitch carbon, graphene oxide, graphene, and mixtures thereof. Possibly polyaromatic sp 2 The carbon-containing carbon precursor can be selected from pitch carbon, graphene oxide, and mixtures thereof. Most preferably, polyaromatic sp 2 The carbon-containing carbon precursor is selected from pitch carbon, which may be selected from coal tar pitch, petroleum pitch, mesophase pitch, wood tar pitch, isotropic pitch, bitumen, and mixtures thereof.

[0109] Pitch carbon is a mixture of aromatic hydrocarbons of varying molecular weights. It is a low-cost by-product of petroleum refineries and is widely available. The use of pitch carbon is advantageous because pitch has a low oxygen content. Therefore, the use of pitch, in combination with heating the intermediate under reducing conditions, favors the formation of oxygen vacancies in the niobium mixed oxide.

[0110] Other carbon precursors usually contain significant amounts of oxygen. For example, carbohydrates such as glucose and sucrose are commonly used as carbon precursors. These are represented by the empirical formula C m (H2O) n and therefore contains a significant amount of covalently bonded oxygen (e.g., sucrose has the formula C 12 H 22 O 11 (having about 42 wt. % oxygen). It is believed that pyrolysis of a carbon precursor containing a significant amount of oxygen prevents or inhibits the reduction of the niobium mixed oxide or even leads to its oxidation, meaning that oxygen vacancies may not be induced in the niobium mixed oxide. Thus, the carbon precursor may have an oxygen content of less than 10 wt. %, preferably less than 5 wt. %.

[0111] The carbon precursor is sp 3 It may be substantially free of carbon. For example, the carbon precursor may contain less than 10 wt. % sp 3 Carbon source, preferably less than 5 wt% sp 3 The carbohydrate may contain a carbon source. 3 The carbon precursor may be free of carbohydrates. Some carbon precursors used in the present invention are sp 3 It is understood that it may contain carbon impurities, for example up to 3 wt% carbon.

[0112] The niobium mixed oxide of the first aspect of the present invention may include a carbon coating. The carbon coating may be a polyaromatic sp 2 It preferably contains carbon. 2Hybridization is largely preserved during pyrolysis, resulting in polyaromatic sp 2 Such coatings are formed by pyrolyzing a carbon-containing carbon precursor, preferably under reducing conditions. Typically, polyaromatic sp 2 The thermal decomposition of the carbon precursor results in sp 2 This results in an increase in the size of the aromatic carbon domains. Thus, polyaromatic sp 2 The presence of a carbon coating containing polyaromatic sp can be established by knowing the precursors used to make the coating. 2 It can be defined as a carbon coating formed from the pyrolysis of a carbon-containing carbon precursor. Preferably, the carbon coating is derived from pitch carbon.

[0113] polycyclic aromatic sp 2 The presence of carbon-containing coatings can also be established by conventional spectroscopic techniques. For example, Raman spectroscopy detects characteristic peaks (1,000–3,500 cm -1 (most prevalent in the sp region) which can be used to distinguish between the various forms of carbon present. 3 For highly crystalline samples of carbon (such as diamond), the peak is approximately 1332 cm -1 A narrow characteristic peak is obtained at polyaromatic sp 2 Carbon usually exhibits characteristic D, G, and 2D peaks. The relative intensities of the D and G peaks (I D / I G ) is sp 2 vs. SP 3 Niobium mixed oxides, when viewed by Raman spectroscopy, have I values ​​in the ranges of 0.85–1.15, or 0.90–1.10, or 0.95–1.05. D / I G The ratio may be:

[0114] X-ray diffraction can also be used to obtain information about the type of carbon coating, for example, the XRD pattern of a carbon-coated niobium mixed oxide can be compared with the XRD pattern of an uncoated niobium mixed oxide and / or the XRD pattern of a pyrolyzed sample of the carbon precursor used to make the carbon coating.

[0115] The carbon coating may be semi-crystalline, for example, capable of producing a niobium mixed oxide XRD pattern peak centered at about 26° 2θ with a width (full width at half maximum) of at least 0.20°, or at least 0.25°, or at least 0.30°. [Example]

[0116] Niobium mixed oxides were synthesized by a solid-state route. In the first step, precursor materials (Nb2O5, Ga2O3, ZnO, ZrO2, Cr2O3, CeO2, and Al2O3) were mixed with niobium oxides to form nanoparticles with a diameter of less than 20 μm. 50 The materials were mixed in stoichiometric ratios (50 g total) and milled to a particle size of 1000 ppm (v / v). The materials were mixed in stoichiometric ratios (50 g total) and mixed into a uniform powder mixture using an impact mill at 20,000 rpm. The resulting powder was heat-treated in alumina crucibles in a muffle furnace in air at T1 = 600–1350°C for 0.5–24 hours to obtain the desired Wadsley-Roth phase. Specifically, the precursor mixture was heated at a ramp rate of 5° / min to a temperature below 800°C, then at a ramp rate of 1° / min to the maximum temperature of the holding period. In some cases, an additional heat treatment step was also applied at T2 = 600–1350°C for 0.5–12 hours under a N2 atmosphere. To incorporate anions, T 2a / T 2b There was an additional milling / mixing step with the precursor (PVDF with a 1:10 mass ratio of F, or C3H6N6 with a 1:3 mass ratio to the base material if N was required) before heat treatment in one or two steps at 300–1300°C for 0.5–24 h in N2 or air atmosphere.

[0117] If necessary, a final deagglomeration step was used by impact milling or jet milling to adjust the particle size distribution to the desired size. Specifically, the material was deagglomerated by impact milling at 20,000 RPM for 10 seconds. Particle size distribution was obtained using a Horiba dry powder laser diffraction particle analyzer. The air pressure was maintained at 0.3 MPa. The results are shown in Table 1. [Table 1]

[0118] Material characterization The phase purity of the samples was analyzed using a Rigaku Miniflex powder X-ray diffractometer over the 2θ range (10–70°) at a scan rate of 1° / min.

[0119] Figure 1 shows the measured XRD diffraction patterns for samples 1-4, and Figure 2 shows the patterns for samples 5-9. The diffraction patterns have peaks at the same positions (with some shifts due to crystallographic modifications, up to about 0.2°), which is consistent with the crystallographic database entry JCPDS 22-009. There is no amorphous background noise, and the peaks are sharp and intense. This indicates that all samples are crystalline, with crystallite sizes of 40-60 nm according to the Scherrer formula, and a crystal structure of AlNb. 11 O 29 This confirms the existence of the Wadsley-Roth crystal structure. [Table 2]

[0120] Electrochemical characterization The charge rate of a lithium-ion battery is usually expressed as a "C-rate." A 1C charge rate means a charging current such that the cell is fully charged in 1 hour, and a 10C charge means that the battery is fully charged in 1 / 10 of an hour (6 minutes). The C-rate here is defined as the reversible capacity seen by the anode within the voltage limits imposed by the second delithiation cycle, i.e., 1.0 mAh cm within the voltage limits of 1.1 to 3.0 V. -2 For an anode with a capacity of 1.0 mA cm, a 1C rate is 1.0 mA cm. -2 For the typical MNO materials described herein, this corresponds to an applied current density of about 200 mA / g active material.

[0121] For analytical purposes, electrochemical testing was performed in half-coin cells (CR2032 size). In half-coin testing, active materials are tested against a Li metal electrode to evaluate the basic performance of the active material. In the following examples, the active material composition to be tested was combined with N-methylpyrrolidone (NMP), carbon black (Super P) acting as a conductive additive, and poly(vinyl difluoride) (PVDF) binder and mixed in a laboratory-scale centrifugal planetary mixer to form a slurry. The non-NMP composition of the slurry was 92 wt% active material, 3 wt% conductive additive, and 5 wt% binder. This slurry was doctor blade coated onto an Al foil current collector to the desired coating weight of 69-75 gm. 2 The electrode was then coated with 2.6–2.9 g cm at 80°C and dried by heating. -3The electrodes were then calendered to a density of 1000 kJ / cm² to achieve a target porosity of 35-40%. The electrodes were die-cut to the desired size and combined with a separator (Celgard porous PP / PE), Li metal, and electrolyte (1.3 M LiPF6 in EC / DEC) in a steel coin cell case, which was then sealed under pressure. The cells were then cycled at 23 °C at a low current rate (C / 10) between 1.1 and 3.0 V for two full cycles of lithiation and delithiation. The cell performance was then tested at increasing current densities. During these tests, the cells were asymmetrically cycled at 23 °C, with slower lithiation (C / 5), followed by increasing delithiation rates (e.g., 1 C, 5 C, 10 C) to maintain capacity and achieve a nominal voltage of 5 C. The nominal voltage for Li / Li+ was calculated from the integral of the V / Q curve during delithiation divided by the total capacity at C / 10 and 5 C. No constant voltage steps were used.

[0122] Cell resistance is calculated from the direct current internal resistance (DCIR) of a half-coin cell. In a typical measurement, the cell is lithiated to 100% SOC, then delithiated at a rate of C / 10 to 50% SOC, then after a 0.5 hour rest, a 5C delithiation pulse is applied for 10 seconds, followed by another 0.5 hour rest. DCIR is then calculated from V=IR, using the voltage just before the peak and the maximum voltage measured during the pulse.

[0123] The data was averaged from five cells prepared from the same electrode coating, and the error is shown as the standard deviation. The data therefore represent a robust study showing the improvement achieved by the material of the present invention compared to conventional materials.

[0124] Additionally, homogeneous, smooth coatings on both Cu and Al current collector foils, free of visible defects or agglomerates, can be prepared as described above for these samples using a centrifugal planetary mixer with compositions of up to 94 wt% active material, 4 wt% conductive additive, and 2 wt% binder. These can be prepared with both PVDF (i.e., NMP-based) and CMC:SBR-based (i.e., aqueous) binder systems. Coatings can be prepared at 80°C for PVDF and 35-40% porosity for CMC:SBR, with capacities of 1.0 to 5.0 mAh cm. -2 The materials can be calendered at 50°C under a load of 1000 kJ / cm², which is important for demonstrating the viability of these materials in both high-energy and high-power applications, due to their high active material content. [Table 3] [Table 4]

[0125] Consideration Niobium mixed oxide sample 1 * Ga 3+ Cation Al substituted with 3+ The focus was on the cation substitution approach in sample 2. Samples 5-9 were modified with Al 3+ with a further cation (Zn 2+ , Zr 4+ , Cr 3+ , and Ce 4+ ) is replaced by the modified ionic radius and the modified voltage. *The cation exchange is expected to provide benefits to the basic crystal structure of the materials. Table 2 shows the changes in unit cell parameters observed upon cation exchange. This is seen through changes in the ionic radius and electronic structure of these materials. The altered ionic radius can lead to beneficial changes in electrochemical performance through changes in unit cell size and local distortions in the crystal structure, potentially altering the available lithiation sites or lithiation pathways and improving capacity, high-rate capability, and lifetime. For example, the hexacoordinated Ga 3+ The ionic radius of the cation is 0.54 angstroms, and the cation is hexacoordinated Al. 3+ The ionic radius of the cation is 0.62 Å. These effects are observed in Sample 1. * This is due to the improved lower delithiation voltages at C / 10 and 5C for the modified sample compared to the cation exchange rate at C / 10C and 5C, as shown in Table 3. Additionally, Table 4 shows improved capacity retention at rates above 5C, with even greater improvement at the higher rate of 10C, a key result demonstrating the utility of the modified niobium mixed oxide according to the present invention for use in high power Li-ion cells designed for fast charge / discharge. Similar benefits are expected to be seen with the cation exchange approach described for this material for use in Li-ion cells.

[0126] Niobium mixed oxide was prepared by F to obtain sample 4. - The exchange is modified by the introduction of anions. This exchange is similar to cation exchange, but with the introduction of cations O 2- sites, in which case increasing the valence may increase the electronic conductivity of the material. Alternatively, it may occur at interstitial sites within the crystal structure. In either case, this may also result in different unit cell sizes and associated crystallographic distortions due to different anion ionic radii and valences, providing similar potential benefits for cation exchange. Similar benefits are expected to be observed by using anions of different electronegativity and valence with any of the described MNO structures for use in Li-ion cells.

[0127] Niobium mixed oxides can be modified by induced oxygen deficiency through heat treatment in an inert or reducing atmosphere to yield Sample 3. By treating these materials at high temperatures in an inert or reducing atmosphere, they become partially reduced and retain this when returned to room temperature and exposed to an air atmosphere. This is reflected in Table 4, where Sample 3 is significantly lower than Sample 1, especially at 5°C and above. * Compared to the previous example, the capacity retention rate has been further improved, and the cell durability has also been further improved.

[0128] Induced oxygen deficiencies are defects in the crystal structure where, for example, oxygen anions are removed, which in turn reduces the overall redox state of the cations. This provides additional energy states that significantly improve the electrical conductivity of the material, changing the bandgap energy. If induced oxygen deficiencies exist in excess of 5 atomic % (i.e., c>1.45), the stability of the crystal structure may be reduced.

[0129] Similar advantages are expected to be seen in any of the described MNO structures utilizing any combination of M1, M2, Q, a, b, c, and d within the described limitations for use in Li-ion cells.

[0130] While the present invention has been described in conjunction with the exemplary embodiments set forth above, many equivalent modifications and variations will become apparent to those skilled in the art given this disclosure. Accordingly, the exemplary embodiments of the present invention set forth above are considered to be illustrative and not limiting. Various changes to the described implementations may be made without departing from the spirit and scope of the present invention. For the avoidance of doubt, the theoretical explanations presented herein are presented for the purpose of enhancing the reader's understanding. The inventors do not wish to be bound by any of these theoretical explanations.

[0131] Any section headings used herein are for organizational purposes only and are not to be construed as limiting the subject matter described. The specific embodiments of the present invention are as follows. [Embodiment 1] An active electrode material containing a niobium mixed oxide, wherein the niobium mixed oxide has a composition M1 a Al 1-a M2 b Nb 11-b O 29-c-d Q d and in the formula, M1 is selected from Mg, Ca, Sr, Y, La, Ce, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Fe, Co, Ni, Cu, Zn, Cd, B, Ga, In, Si, Ge, Sn, Pb, P, Sb, Bi and mixtures thereof, M2 is selected from Mg, Ca, Sr, Y, La, Ce, Zr, Hf, V, Ta, Cr, Mo, W, Mn, Fe, Co, Ni, Cu, Zn, Cd, B, Al, Ga, In, Si, Ge, Sn, Pb, P, Sb, Bi and mixtures thereof, Q is selected from F, Cl, Br, I, N, S, Se, and mixtures thereof, 0 ≦ a < 0.5, 0 ≦ b ≦ 1, -0.5 ≦ c ≦ 1.45, 0 ≦ d ≦ 1.45, and one or more of a, b, and d are not equivalent to 0, the active electrode material. [Embodiment 2] (i) a > 0, and / or (ii) 0 ≦ a ≦ 0.4, and / or (iii) 0 ≦ a ≦ 0.2, the active electrode material according to Embodiment 1. [Embodiment 3] (i) b > 0, and / or (ii) 0 ≦ b ≦ 0.5, and / or (iii) 0 ≦ b ≦ a, or (iv) b = 0, the active electrode material according to any of the preceding embodiments. [Embodiment 4] (i) c ≠ 0, or (ii) 0 ≦ c ≦ 1.45, or (iii) 0 < c ≦ 1.45, the active electrode material according to any of the preceding embodiments. [Embodiment 5] (i) d > 0, and / or (ii) 0 ≦ d ≦ 1.0, and / or (iii) 0 ≦ d ≦ 0.7, or (iv) d = 0, the active electrode material according to any of the preceding embodiments. [Embodiment 6] At least one of a and b is greater than 0, or when both a and b are greater than 0, or a > 0 and b = 0, the active electrode material according to any of the preceding embodiments. [Embodiment 7] M1 is (i) Mg, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Fe, Co, Ni, Cu, Zn, Cd, B, Ga, Si, Ge, Sn, P, and mixtures thereof, or (ii) Mg, Zr, V, Cr, Mo, W, Mn, Fe, Co, Ni, Cu, Zn, B, Ga, Si, Ge, P, and mixtures thereof, or (iii) Mg, Zr, Mo, W, Cu, Zn, Ga, Ge, P, and mixtures thereof, the active electrode material according to any of the preceding embodiments. [Embodiment 8] The active electrode material according to any of the preceding aspects, wherein M1 is Ga. [Aspect 9] M2 is (i) Mg, Zr, Hf, V, Ta, Cr, Mo, W, Mn, Fe, Co, Ni, Cu, Zn, Cd, B, Al, Ga, Si, Sn, P, and mixtures thereof, or (ii) Mg, Zr, V, Cr, Mo, W, Mn, Fe, Co, Ni, Cu, Zn, Cd, B, Al, Si, P, and mixtures thereof, or (iii) an active electrode material according to any of the preceding aspects, selected from Zr, V, Cr, Mo, W, Fe, Cu, Zn, Al, P, and mixtures thereof. [Aspect 10] The niobium mixed oxide has the composition M1 a Al 1-a Nb 11 O 29-c-d Q d and M1 is selected from Mg, Zr, V, Cr, Mo, W, Mn, Fe, Co, Ni, Cu, Zn, B, Ga, Si, Ge, P, and mixtures thereof, Q is selected from F, N, and mixtures thereof, and 0 < a < 0.5, 0 ≤ c ≤ 1.45, and the active electrode material according to any of the preceding aspects where 0 ≤ d ≤ 1.45. [Aspect 11] The niobium mixed oxide has the composition M1 a Al 1-a Nb 11 O 29-c-d Q d and M1 is selected from Mg, Zr, Mo, W, Cu, Zn, Ga, Ge, P, and mixtures thereof, [[ID= ​ ​ ​ ​ 3+ ​ 3+ ​ ​ ​ ​ ​ 5+ ​ 5+ ​ ​ ​ ​ ​ (iii) The active electrode material of any preceding embodiment, wherein M1 has a valence equal to or lower than 3+ and M2 has a valence lower than 5+. [Aspect 15]

[0023] The active electrode material of any preceding embodiment, wherein M1 is free of Nb and M2 is free of Al. [Aspect 16] (i) Q is selected from F, Cl, N, S, and mixtures thereof; or (ii) Q is selected from F, N, and mixtures thereof; or (iii) The active electrode material of any preceding embodiment, wherein Q is F. [Aspect 17] 10. The active electrode material of any preceding aspect, wherein the niobium mixed oxide is oxygen deficient, and optionally, the niobium mixed oxide induces oxygen deficiency. [Aspect 18] 10. The active electrode material of any preceding aspect, wherein the niobium mixed oxide is coated with carbon. [Aspect 19] The carbon coating is a polyaromatic sp 2 20. The active electrode material of embodiment 18, comprising carbon, and optionally the carbon coating is derived from pitch carbon. [Aspect 20] The niobium mixed oxide is in particulate form, and optionally the niobium mixed oxide has a D in the range of 0.1 to 100 μm, or 0.5 to 50 μm, or 1 to 20 μm. 50

[0023] The active electrode material of any preceding aspect, having a particle size of [Aspect 21] The niobium mixed oxide has a viscosity of 0.1 to 100 m 2 / g, or 0.5 to 50 m 2 / g, or 1 to 20 m 2

[0039] The active electrode material of any preceding embodiment, having a BET surface area in the range of 1 / g. [Aspect 22]

[0023] The active electrode material of any preceding embodiment, wherein the niobium mixed oxide further comprises Li and / or Na. [Aspect 23] The crystal structure of the niobium mixed oxide determined by X-ray diffraction is AlNb 11 O 29

[0023] The active electrode material of any preceding aspect, wherein the active electrode material corresponds to a crystal structure of [Aspect 24] 10. The active electrode material of any preceding aspect, comprising the niobium mixed oxide and at least one other component, optionally the at least one other component selected from a binder, a solvent, a conductive additive, a different active electrode material, and mixtures thereof. [Aspect 25] 25. The active electrode material of embodiment 24, wherein the at least one other component is a different active electrode material selected from a different niobium mixed oxide having a composition defined by any of the preceding embodiments, a lithium titanium oxide, a niobium oxide, and mixtures thereof. [Aspect 26] An electrode comprising the active electrode material according to any one of aspects 1 to 25 in electrical contact with a current collector. [Aspect 27] 26. An electrochemical device comprising: an anode, a cathode, and an electrolyte disposed between the anode and the cathode, wherein the anode comprises the active electrode material of any of aspects 1-25; and optionally, the electrochemical device is a lithium-ion battery or a sodium-ion battery. [Aspect 28] 26. The electrochemical device of embodiment 25, wherein the lithium ion battery has a reversible anode active material specific capacity greater than 195 mAh / g at 20 mA / g, wherein the battery can be charged and discharged at a current density for the anode active material of 200 mA / g or greater, or 1000 mA / g or greater, or 2000 mA / g or greater, or 4000 mA / g or greater, while retaining 70% or more of the initial cell capacity at 20 mA / g. [Aspect 29] 24. A method for producing a niobium mixed oxide as defined in any of Aspects 1 to 23, the method comprising the steps of obtaining one or more precursor materials, mixing the precursor materials to form a precursor material mixture, and heat treating the precursor material mixture at a temperature in the range of 400°C to 1350°C or 800°C to 1300°C, thereby obtaining the niobium mixed oxide. [Aspect 30] mixing said niobium mixed oxide with a precursor comprising element Q to obtain a further precursor material mixture; and 30. The method of embodiment 29, further comprising the step of heat treating the further precursor mixture, optionally under reducing conditions, at a temperature in the range of 300 to 1300°C or 800 to 1200°C, thereby obtaining the niobium mixed oxide comprising element Q. [Aspect 31] 31. The method according to aspect 29 or 30, comprising the further step of heat treating the niobium mixed oxide or the niobium mixed oxide comprising element Q under reducing conditions in a temperature range of 400 to 1350°C or 800 to 1300°C, thereby inducing oxygen vacancies in the niobium mixed oxide. [Aspect 32] The niobium mixed oxide or the niobium mixed oxide containing the element Q is subjected to a polyaromatic sp 2 combining a carbon precursor with carbon to form an intermediate material; and 32. The method of any of aspects 29-31, further comprising heating the intermediate material under reducing conditions to pyrolyze the carbon precursor and form a carbon coating on the niobium mixed oxide and induce oxygen vacancies in the niobium mixed oxide.

Claims

1. 1. An active electrode material comprising a niobium mixed oxide, said niobium mixed oxide having the composition M1 ａ Al １－ａ M2 ｂ Nb １１－ｂ O ２９－ｃ－ｄ Q ｄ wherein M1 is selected from Mg, Zr, V, Ta, Cr, Mo, W, Mn, Fe, Co, Ni, Cu, Zn, B, Ga, Si, Ge, P, and mixtures thereof; M2 is selected from Mg, Zr, V, Ta, Cr, Mo, W, Mn, Fe, Co, Ni, Cu, Zn, Cd, B, Si, P, and mixtures thereof; Q is selected from F, Cl, N, S, and mixtures thereof; 0≦a<0.5, 0≦b≦1, −0.5≦c≦1.45, 0≦d≦1.45, The active electrode material wherein one or more of a, b, and d is not equal to 0.

2. The active electrode material described in claim 1, wherein 0≦a≦0.

4.

3. An active electrode material according to claim 1 or 2, wherein 0≦b≦0.

5.

4. An active electrode material according to any one of claims 1 to 3, wherein 0≦c≦1.

45.

5. The active electrode material according to claim 1, wherein 0≦d≦1.

0.

6. 6. The active electrode material of claim 1, wherein at least one of a and b is greater than 0.

7. M1, 7. The active electrode material of any one of claims 1 to 6, selected from Mg, Zr, Mo, W, Cu, Zn, Ga, Ge, P, and mixtures thereof.

8. 8. The active electrode material of claim 1, wherein M1 is Ga.

9. The niobium mixed oxide has the composition M1 ａ Al １－ａ Nb １１ O ２９－ｃ－ｄ Q ｄ and M1 is selected from Mg, Zr, V, Cr, Mo, W, Mn, Fe, Co, Ni, Cu, Zn, B, Ga, Si, Ge, P, and mixtures thereof; Q is selected from F, N, and mixtures thereof; 9. The active electrode material according to claim 1, wherein 0<a<0.5, 0≦c≦1.45, and 0≦d≦1.

45.

10. The niobium mixed oxide has the composition M1 ａ Al １－ａ Nb １１ O ２９－ｃ－ｄ Q ｄ and M1 is selected from Mg, Zr, Mo, W, Cu, Zn, Ga, Ge, P, and mixtures thereof; Q is selected from F, N, and mixtures thereof; 10. The active electrode material according to claim 1, wherein 0<a≦0.2, 0≦c≦1.45, and 0≦d≦1.

45.

11. (i) M1 has a hexacoordinate ionic radius of 0.1<r<1.0 Angstroms; or (ii) M1 is hexacoordinated Al ３＋ The active electrode material according to any one of claims 1 to 10, having a hexacoordination ionic radius different from

12. (i) M2 has a hexacoordinate ionic radius of 0.1<r<1.0 Angstroms; or (ii) M2 is hexacoordinated Nb ５＋ 12. The active electrode material according to claim 1, wherein the ionic radius of the six-coordination is different from

13. (i) M1 has a valence equal to or lower than 3+, or (ii) M2 has a valence lower than 5+, or (iii) M1 has a valence equal to or lower than 3+, and M2 has a valence lower than 5+.

14. The active electrode material of claim 1, wherein Q is selected from F, N, and mixtures thereof.

15. 15. The active electrode material of any one of claims 1 to 14, wherein the niobium mixed oxide is oxygen deficient.

16. 16. The active electrode material according to any one of claims 1 to 15, wherein the niobium mixed oxide is coated with carbon.

17. The carbon coating is a polyaromatic sp ２ 17. The active electrode material of claim 16 comprising carbon.

18. The niobium mixed oxide is in the form of particles, and the niobium mixed oxide has a D in the range of 0.1 to 100 μm. ５０ 18. The active electrode material according to claim 1, having a particle size of

19. The niobium mixed oxide has a viscosity of 0.1 to 100 m ２ 19. The active electrode material of any one of claims 1 to 18, having a BET surface area in the range of 1 / g.

20. 20. The active electrode material according to any one of claims 1 to 19, wherein the niobium mixed oxide further comprises Li and / or Na.

21. The crystalline structure of the niobium mixed oxide determined by X-ray diffraction is AlNb １１ O ２９ 21. The active electrode material according to claim 1, which corresponds to the crystal structure

22. 22. The active electrode material of any one of claims 1 to 21, comprising the niobium mixed oxide and at least one other component.

23. 23. The active electrode material of claim 22, wherein the at least one other component is selected from lithium titanium oxide, niobium oxide, and mixtures thereof.

24. 24. An electrode comprising the active electrode material of any one of claims 1 to 23 in electrical contact with a current collector.

25. 24. An electrochemical device comprising an anode, a cathode, and an electrolyte disposed between the anode and the cathode, wherein the anode comprises the active electrode material of any of claims 1 to 23.

26. 22. A method for producing a niobium mixed oxide as defined in any one of claims 1 to 21, said method comprising the steps of obtaining one or more precursor materials, mixing said precursor materials to form a precursor material mixture, and heat treating said precursor material mixture at a temperature in the range of 400°C to 1350°C, thereby obtaining said niobium mixed oxide.

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