Active electrode material

Abstract

The invention relates to an electrode comprising mixed niobium oxide as active electrode material. The electrode may be used in a metal ion battery, such as a lithium ion battery. The mixed niobium oxide may have the formula MIx-uMy (x / (5-y)) MVzNb100-(x / (5-y))-zO250-u / 2, wherein: MI is a cation having an oxidation state of 1; my is a cation of which the average oxidation state is y; mV is a cation having an average oxidation state of 5; 1 < = y < = 4; 0.5 < = x < = 6; 0 < = z < = 10; 0 < = u < = 5; xgt; u.

Description

[0001] This application is a divisional application of Chinese invention application with an international filing date of December 14, 2022, international application number PCT / GB2022 / 053230, Chinese national phase application number 202280084264.2, and invention title "Active Electrode Material". Technical Field

[0002] This invention relates to active electrode materials, methods for manufacturing active electrode materials, and electrodes comprising active electrode materials. Such materials are of interest as active electrode materials (e.g., as anode materials) in metal-ion batteries (such as lithium-ion or sodium-ion batteries). Background Technology

[0003] Lithium-ion (Li-ion) batteries are a commonly used type of rechargeable battery, and their global market is projected to grow to $200 billion by 2030. Li-ion batteries are the technology of choice for electric vehicles with diverse requirements in terms of technical performance and environmental impact, thus providing a viable path for the green automotive industry.

[0004] A typical lithium-ion battery consists of multiple battery cells connected in series or parallel. Each individual battery cell typically consists of an anode (negative electrode) and a cathode (positive electrode), which are separated by a porous electrically insulating membrane (called a separator) and immersed in a liquid (called an electrolyte) capable of transporting lithium ions.

[0005] In most systems, the electrode consists of an active electrode material—meaning it can chemically react with lithium ions to reversibly store and release them in a controlled manner—mixed with conductive additives (such as carbon) and polymer binders, if necessary. A slurry of these components is coated in thin film onto a current collector (typically a thin foil of copper or aluminum) to form the electrode after drying.

[0006] In known Li-ion battery technologies, the safety limitations of graphite anodes during battery charging severely hinder their application in high-power electronics, automotive, and industrial applications. Among the wide range of potential alternatives recently proposed, lithium titanate (LTO) and hybrid niobium oxide are leading contenders to replace graphite as the preferred 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 insert into the anode active material during charging. As the charge rate increases, the typical graphite voltage profile presents a high risk of overpotential, where the potential at the anode sites becomes <0 V relative to Li / Li+. This leads to a phenomenon called lithium dendrite plating, where lithium ions are deposited as lithium metal on the surface of the graphite electrode. This results in the irreversible loss of active lithium and thus rapid capacity decay of the battery cell. In some cases, these dendritic deposits can grow to such a large size that they pierce the battery separator and cause a short circuit in the battery cell. This can trigger a catastrophic failure of the battery cell, leading to a fire or explosion. Therefore, the fastest-charging batteries with graphite anodes are limited to charge rates of 5-7 C, but typically lower.

[0008] Lithium titanate (LTO) anodes are not susceptible to dendrite plating at high charge rates due to their high potential (1.6 V relative to Li / Li+) and exhibit excellent cycle life because their adaptive 3D crystal structure prevents significant volume expansion of the active material during Li-ion intercalation. For both reasons, LTO cells are generally considered high-safety cell types. However, LTO is a relatively poor electronic and ionic conductor, resulting in limited capacity retention and power performance at high rates unless the material is nanoscale to increase specific surface area and coated with carbon to increase electronic conductivity. This particulate-scale material engineering increases the porosity and specific surface area of ​​the active material and leads to a significant reduction in the achievable fill density in the electrode. This is significant because it results in a low-density electrode and a higher fraction of electrochemically inactive materials (e.g., binders, carbon additives), leading to much lower gravitational and volumetric energy densities.

[0009] The key metric for anode performance is electrode volumetric capacity (mAh / cm³). 3 Electrode volumetric capacity, or the amount of charge (i.e., lithium ions) that can be stored per unit volume of the anode, is a crucial factor in determining the total battery energy density (Wh / L) based on volume when combined with the cathode and appropriate cell design parameters. Electrode volumetric capacity can be approximated by electrode density (g / cm³). 3 The specific capacity (mAh / g) of the active material is the product of the amount of active material in the electrode and the fraction of active material in the electrode. LTO anodes typically have a relatively low specific capacity (c. 165 mAh / g, to be compared with graphite's c. 330 mAh / g), coupled with the low electrode density discussed above (typically <2.0 g / cm³). 3 The combination of low active material fraction (<90%) results in a very low volumetric capacity (<300 mAh / cm³). 3This results in low battery energy density and high cost per kWh across a wide range of applications. Consequently, LTO batteries / cells are typically limited to specific niche applications, despite their long cycle life, fast charging capabilities, and high safety.

[0010] Hybrid niobium oxides have been known in academic literature for some time. Recently, the use of some hybrid niobium oxides in lithium-ion battery cells has attracted interest. For example, Zhu et al., J. Mater. Chem. A, 2019, 7, 25537 and Zhu et al., Chem. Commun., 2020, 56, 7321-7324 disclose Zn₂Nb as a possible active electrode material. 34 O 87 and Cu2Nb 34 O 87 These papers rely on complex particle-level engineering to achieve the allegedly desirable properties, such as attempts to control particle porosity and morphology. WO2021 / 074593 and WO2021 / 074594 disclose various substituted and / or oxygen-deficient hybrid niobium oxides that have been found to possess good properties for use as active electrode materials. However, there is still a need to identify other hybrid niobium oxides with good properties for use as active electrode materials, particularly those with good properties for lithium-ion battery cells intended for high-power / fast-charging applications. For example, identifying such materials that do not require extensive particle-level engineering and / or coatings is an important step towards bringing low-cost battery materials to the mass market. Summary of the Invention

[0011] In a first aspect, the present invention provides an electrode comprising a mixed niobium oxide as an active electrode material, wherein the mixed niobium oxide has the formula M as defined in claim 1. I x-u M y (x / (5-y)) M V z Nb 100-(x / (5-y))-z O 250-u / 2 .

[0012] Mixed niobium oxide may also have formula B as defined in claims. a M v z Nb 100-a-z O 250-a .

[0013] Mixed niobium oxide may also have the formula M as defined in claims. b Nb 100-b O 250-2.5b+bc .

[0014] The inventors have discovered that the electrodes according to the first aspect retain surprisingly high capacity even during delithiation at high rates, such as 5C and 10C, as shown in the embodiments of the present invention. These are important results demonstrating the advantages of the hybrid niobium oxide of the present invention for designing high-power batteries for fast charging / discharging.

[0015] In a second aspect, the present invention provides a metal-ion battery comprising a mixed niobium oxide as the active electrode material, wherein the mixed niobium oxide is as defined in the first aspect. Optionally, the metal-ion battery is a lithium-ion battery or a sodium-ion battery, preferably a lithium-ion battery.

[0016] In a third aspect, the present invention provides the use of mixed niobium oxide as defined in the first aspect as an active electrode material in a metal-ion battery. Optionally, the metal-ion battery is a lithium-ion battery or a sodium-ion battery, preferably a lithium-ion battery.

[0017] In a fourth aspect, the present invention provides a method of manufacturing an electrode, comprising providing a mixed niobium oxide as defined in the first aspect; and depositing the mixed niobium oxide onto a current collector to form an electrode. Attached Figure Description

[0018] The principles of the invention will now be discussed with reference to the accompanying drawings.

[0019] Figure 1 XRD patterns of the selected synthesized Wadsley-Roth 4×4 octahedral block structure.

[0020] Figure 2 TEM micrographs and selected area electron diffraction of sample 11 obtained using a Thermo Scientific (FEI) Talos F200X G2 TEM. Left panel: High-magnification image showing the highly crystalline structure. Right panel: Selected area electron diffraction, where the (110) interplanar spacing matches the interplanar spacing determined by XRD.

[0021] Figure 3 XRD pattern of sample 18 collected using CuKα X-ray source.

[0022] Figure 4 The voltage curves of samples 3 and 18 in the half-cell cells during the second cycle relative to the state of charge / discharge when using a C-rate of C / 10 from 3.0 to 1.1 V. Detailed Implementation

[0023] The term "hybrid niobium oxide" refers to an oxide containing niobium and at least one other cation. Hybrid niobium oxide exhibits a high redox voltage (>0.8V) relative to lithium, enabling safe and long-life operation, which is crucial for battery cells in fast-charging batteries. Furthermore, each atom of the niobium cation can undergo two redox reactions, resulting in a higher theoretical capacity than, for example, LTO.

[0024] Mixed niobium oxide can have formula M I x-u M y (x / (5-y)) M V z Nb 100-(x / (5-y))-z O 250-u / 2 ,in:

[0025] M I It is a cation with an oxidation state of 1;

[0026] M y It is a cation with an average oxidation state of y;

[0027] M V It is a cation with an average oxidation state of 5;

[0028] 1 ≤ y ≤ 4;

[0029] 0.5 ≤ x ≤ 6;

[0030] 0 ≤ z ≤ 10;

[0031] 0 ≤ u ≤ 5;

[0032] x > u.

[0033] Mixed niobium oxide can also have formula B a M v z Nb 100-a-z O 250-a ,in

[0034] M V It is a cation with an average oxidation state of 5;

[0035] 0 ≤ z ≤ 10;

[0036] 0 < a ≤ 8.

[0037] Mixed niobium oxide can also have formula M b Nb 100-b O 250-2.5b+bc ,in

[0038] M is a cation selected from P, B, W, Mo, V, Ti, Si and mixtures thereof;

[0039] c is half the average oxidation state of M;

[0040] 1.5 ≤ c ≤ 3; and

[0041] 0.5 < b ≤ 6.

[0042] Mixed niobium oxides with the formulas defined herein are uniform because they can adopt crystal structures considered to contribute to their advantageous properties as active electrode materials. In particular, mixed niobium oxides can adopt crystal structures having a Wadsley-Roth crystal structure comprising 4×4 octahedral blocks. The Wadsley-Roth crystal structure is considered a crystallographically nonstoichiometric MO3 (ReO3) crystal structure containing crystallographic shear, simplified to MO3. 3-x Therefore, these structures typically contain [MO6] octahedral subunits in their crystal structure. In a 4×4 octahedral block structure, each block is connected only by octahedra sharing edges. This structure was reported in 1967 as having a monoclinic unit cell (a = 28.51 Å, b = 3.830 Å, c = 17.48 Å, β = 120.80º, space group = C2 / m). This structure and related structures have been reported in historical academic literature, but no data on electrochemical lithiation or delithiation have been provided (Andersson, Zeitschrift für anorganische und allgemeine Chemie, Vol. 351, No. 1-2, April 1967, pp. 106-112; Pekhtereva, Yu.A., & Shukaev, IL (1999), Zhurnal Neorganicheskoj Khimii, 44(2), 290-294; Cava et al. 1983 J. Electrochem. Soc. 130 2345; Villafuerte-Castrejón, Journal of Solid State Chemistry, Vol. 71, No. 1, November 1987, No. 103-108; Norin and Bertil, Acta Chemica Scandinavica, Vol. 25 (1971), pp. 741–743; Reisman and Holtzberg, J. Am. Chem. Soc. 1958, 80, 24, 6503–6507. It is believed that this large bulk size, compared to other Wadsley-Roth structures with smaller octahedral bulk sizes, facilitates rapid lithium insertion and removal, and potentially offers higher stability compared to Wadsley-Roth structures with even larger octahedral bulk sizes.

[0043] The polymorph of niobium oxide N-Nb₂O₅ adopts a Wadsley-Roth crystal structure comprising 4×4 octahedral blocks. Therefore, the crystal structure of mixed niobium oxide, as determined by X-ray diffraction, preferably corresponds to the crystal structure of N-Nb₂O₅. The crystal structure of N-Nb₂O₅ can be found in Andersson 1967, Zeitschrift für anorganische und allgemeine Chemie, Vol. 351, Nos. 1-2, April 1967.

[0044] Compared to the empirical formula of N-Nb₂O₅, the mixed niobium oxide according to the present invention has a modified cation-to-anion ratio. In formula M... I x-u M y (x / (5-y)) M V z Nb 100-(x / (5-y))-z O 250-u / 2 In the middle, some Nb were M I and M y The substitution of the two increases the ratio of cations to anions. In formula B... a M v z Nb 100-a-z O 250-a In this process, some Nb has been replaced by B, resulting in the loss of oxygen in the crystal structure to maintain charge neutrality, and also increasing the cation-to-anion ratio; the crystal structure of materials with this formula may contain some tetrahedral boron cations between 4×4 octahedral blocks. This modification is believed to contribute to the advantageous properties of mixed niobium oxide as an active electrode material. For example, the modified cation-to-anion ratio is thought to stabilize the crystal structure.

[0045] The crystal structure of a material can be determined by analyzing X-ray diffraction (XRD) patterns, which are typically obtained from a Cu Kα source, as is well known. For example, the crystal structure can be confirmed by comparing the XRD pattern obtained from a given material with known XRD patterns, for example via public databases such as the ICDD crystallography database. Rietveld and Pawley analyses can also be used to determine the crystal structure of a material, particularly for cell parameters. Thus, as determined by X-ray diffraction, mixed niobium oxide can have a Wadsley-Roth crystal structure comprising 4×4 octahedral blocks.

[0046] Here, the term 'corresponding' is intended to reflect that the peaks in the X-ray diffraction pattern may be offset by no more than 0.5 degrees from the corresponding peaks in the X-ray diffraction patterns of the materials listed above (preferably no more than 0.25 degrees, more preferably no more than 0.1 degrees).

[0047] Mixed niobium oxide can be produced using a monoclinic crystal structure, for example, a monoclinic crystal structure with cell parameters a = 25.7–31.4 Å, b = 3.4–4.2 Å, c = 15.8–19.3 Å, α = 90°, γ = 112.6–137.6°, and γ = 90°. The cell parameters can be determined by X-ray diffraction.

[0048] M I It is a cation with an oxidation state of 1. M I It can be selected from Li, Na, K, and mixtures thereof. Preferably, M I Selected from Li, Na, and mixtures thereof.

[0049] x is M I The atomic weight is in the range of 0.5 ≤ x ≤ 6. x can be an integer, such as x = 1, 2, 3, 4, 5 or 6. Optionally, 2 ≤ x ≤ 5, such as x = 2, 3, 4 or 5. Preferably, x = 4.

[0050] This formula is in M I There may be drawbacks in this regard; for example, some 1+ cations are lost via volatility due to their typically low atomic weight. Therefore, the atomic weight of x can be modified by the variable 0 ≤ u ≤ 5, where x > u, for example, x ≥ u + 1. Optionally, 0 ≤ u ≤ 3 or 0.01 ≤ u ≤ 2. Alternatively, u = 0.

[0051] M y It is a cation with an average oxidation state of y. The term "average oxidation state" means that when more than one cation is present, the oxidation state refers to M as a whole. y For example, if M y 1 / 3 is W 6+ And M y 2 / 3 is Fe 3+ Then y is 4 (1 / 3 × 6 (W's contribution) + 2 / 3 × 3 (Fe's contribution)). However, M y M II M III M IV and M V It can consist of a single cation, in which case the oxidation state is the oxidation state of that cation.

[0052] M yIt can be selected from Li, Na, K, Cu, Zn, Mg, Ca, Ni, Fe, Mn, Co, Cr, V, Al, B, Ga, Sc, Y, In, La, Yb, Ce, Zr, Ti, Sn, Ge, Si, P, Ta, W, Mo and mixtures thereof; or Li, Na, K, Cu, Zn, Mg, Ni, Fe, Mn, Co, Cr, V, Al, B, Ga, Zr, Ti, Si, P, Ta and mixtures thereof; or Li, Na, Cu, Zn, Mg, Ni, Fe, Mn, Co, Cr, Al, B, Ga, Zr, Ti and mixtures thereof. Optionally, M y It does not contain Li.

[0053] The range of y is 1 ≤ y ≤ 4, optionally 2 ≤ y ≤ 4. y can be an integer, for example, y = 1, 2, 3, or 4; preferably 2, 3, and 4. When y is an integer, optionally, M is formed. y All cations have the same oxidation state.

[0054] When y is 1, 2, 3, or 4, M y It can be selected from Li, Na, Cu, Zn, Mg, Ca, Ni, Fe, Mn, Co, Cr, Al, B, Ga, Sc, Y, In, La, Yb, Ce, Zr, Ti, Sn, Ge and mixtures thereof.

[0055] When y is 2, 3, or 4, M y It can be selected from Cu, Zn, Mg, Ca, Ni, Fe, Mn, Co, Mn, Cr, Al, B, Ga, Sc, Y, In, La, Yb, Ce, Zr, Ti, Sn, Ge and mixtures thereof.

[0056] M y The atomic weight depends on M I The quantity and M y The oxidation states of the atoms have a relationship of x / (5-y).

[0057] M V It is an optional cation with an average oxidation state of 5. Optionally, M V It is a cation with an oxidation state of 5, in which M is formed V All cations have the same oxidation state 5.

[0058] M V The atomic weight is z, and its range is 0 ≤ z ≤ 10. Optionally, 0 ≤ z ≤ 5. z can be > 0, for example > 0.01. Alternatively, z = 0, in which case M V It does not exist.

[0059] M VIt may be selected from Mn, Fe, Al, Ga, Y, In, La, Yb, Cu, Zn, Mg, Ni, Co, Ca, Ce, Zr, Ti, Sn, Ge, Si, V, P, Ta, W, Mo, Cr and mixtures thereof; or Ce, Zr, Ti, Sn, Ge, Si, V, P, Ta, W, Mo, Cr, V, P, Ta and compounds thereof; or V, P, Ta and mixtures thereof. Optionally, M is formed. V All of the cations have an oxidation state of 5.

[0060] When y = 1, the mixed niobium oxide can have the formula M I x-u N I x / 4 M V z Nb 100-x / 4-z O 250-u / 2 , where N I It is a cation with an oxidation state of 1. N I It can be selected from Li, Na, K and mixtures thereof; preferably Li, Na and mixtures thereof.

[0061] When y = 2, the mixed niobium oxide can have the formula M I x-u M II x / 3 M V z Nb 100-x / 3-z O 250-u / 2 M II It is a cation with an average oxidation state of 2. M II It may be selected from Cu, Zn, Mg, Ni, Fe, Mn, Co, Ca and mixtures thereof; or Cu, Zn, Mg, Ni and mixtures thereof; or Zn, Mg, Ni and mixtures thereof. Optionally, M is formed. II All of the cations have an oxidation state of 2.

[0062] When y = 3, the mixed niobium oxide can have the formula M I x-u M III x / 2 M V z Nb 100-x / 2-z O 250-u / 2 M III It is a cation with an average oxidation state of 3. M III It can be selected from Mn, Cr, V, Fe, Al, B, Ga, Y, In, La, Yb, Ce and mixtures thereof; or Mn, Cr, Fe, Al, B, Ga, Y and mixtures thereof; or Cr, Al, Fe and mixtures thereof. Optionally, M is formed. IIIAll of the cations have an oxidation state of 3.

[0063] When y = 4, the mixed niobium oxide can have the formula M I x-u M IV x M V z Nb 100-x-z O 250-u / 2 M IV It is a cation with an average oxidation state of 4. M IV It can be selected from Zr, Ti, Mn, Ce, Sn, Ge, V, Si and mixtures thereof; or Zr, Ti, Sn, Ge, V and mixtures thereof; or Ti, V and mixtures thereof. Optionally, M is formed. V All of the cations have an oxidation state of 4.

[0064] B a M v z Nb 100-a-z O 250-a The atomic weight of B is a, which ranges from 0 < a ≤ 8, for example, 0.01 < a ≤ 8. Optionally, 1 ≤ a ≤ 5 or 1.5 ≤ a ≤ 3. a can be an integer. Preferably, a = 2. Up to 10 atomic percent of the cation may be partially substituted by at least one cation selected from: P, K, Fe, Ti, Zr, Sn, Ge, Zn, Mg, Al, Ga, Y, W, Mo, Cr, V, Si, Ni, Mn, Ta, Li, Na and mixtures thereof; or Ti, W, Mo, Cr, Zn, Al, Fe, P and mixtures thereof.

[0065] In M as described above b Nb 100-b O 250-2.5b+bc In this context, M is a cation selected from P, B, W, Mo, V, Ti, Si, and mixtures thereof. M may be selected from P, W, B, Ti, and mixtures thereof; or P, W, and mixtures thereof. Preferably, M comprises P and / or W. Up to 10 atomic% of the cation may be partially substituted by at least one cation selected from: K, Fe, Zr, Sn, Ge, Zn, Mg, Al, Ga, Y, Cr, Ni, Mn, Ta, Li, Na, and mixtures thereof; or Cr, Zn, Al, Fe, and mixtures thereof. b is 0.5 < b ≤ 6, or 1 ≤ b ≤ 5.75, or 1.5 ≤ b ≤ 5.5. c is half the average oxidation state of M, and is 1.5 ≤ c ≤ 3, or 2 ≤ c ≤ 2.75, or 2.5.

[0066] In M from CuKα source b Nb100-b O 250-2.5b+bc In the X-ray diffraction pattern, the strongest peak between 18.15–18.65° 2θ may have a full width half maximum (WHM) of >0.2; optionally >0.4, >0.6 and / or <0.9 (e.g., >0.2 to <0.9). Figure 3 The XRD pattern of a sample exhibiting this peak is shown. It is believed that the sample with this peak contains some connected tetrahedral cations between 4×4 octahedral blocks within a Wadsley-Roth crystal structure. Materials with this crystal structure have been found to have particularly high capacities.

[0067] It should be understood that for variables in the formula (e.g., M, M...) I , x, u, M y y, M v The discussion of (z, a, b, c) is intended to be read in combination. For example, mixed niobium oxide can have formula M. I x-u M y (x / (5-y)) M V z Nb 100-(x / (5-y))-z O 250-u / 2 ,in:

[0068] M I It consists of Li, Na, and mixtures thereof;

[0069] M y It is a cation selected from Li, Na, Cu, Zn, Mg, Ca, Ni, Fe, Mn, Co, Cr, Al, B, Ga, Sc, Y, In, La, Yb, Ce, Zr, Ti, Sn, Ge and mixtures thereof with an average oxidation state of y;

[0070] M V It is a cation selected from V, P, Ta and their mixtures, with an average oxidation state of 5;

[0071] 1 ≤ y ≤ 4;

[0072] 2 ≤ x ≤ 6;

[0073] 0 ≤ z ≤ 10;

[0074] 0 ≤ u ≤ 3;

[0075] x ≥ u + 1.

[0076] For example, mixed niobium oxide can have the formula M I x M y (x / (5-y))Nb 100-(x / (5-y)) O 250 ,in:

[0077] M I It consists of Li, Na, and mixtures thereof;

[0078] M y It is a cation with an oxidation state of y selected from Li, Na, Cu, Zn, Mg, Ca, Ni, Fe, Mn, Co, Cr, Al, B, Ga, Sc, Y, In, La, Yb, Ce, Zr, Ti, Sn, Ge and mixtures thereof, wherein M forms y All cations have the same oxidation state;

[0079] y = 1, 2, 3 or 4;

[0080] x = 3, 4 or 5.

[0081] M y M I N I M II M III M IV M can also be selected from each particular element as used in the embodiments.

[0082] Optionally, if further cations other than Li and Nb are present, the mixed niobium oxide contains only Li. An example of such a material is Li₄Cr₂Nb. 98 O 250 Cr is a cation other than Li and Nb. Furthermore, the mixed niobium oxide may be Li-free. It should be understood that mixed niobium oxides (including those without Li) can reversibly insert Li in situ when used as active electrode materials in lithium-ion batteries.

[0083] In mixed niobium oxide, the cations can be partially substituted by further cations of different oxidation states, for example, up to 20 atomic%, 10 atomic%, or 5 atomic% of cations can be substituted. Substitution of cations of different oxidation states creates a charge-imbalanced material. This charge imbalance can be compensated for by oxygen deficiency (substitution by cations of lower oxidation states) or excess (substitution by cations of higher oxidation states). Alternatively or additionally, the charge imbalance can be compensated for by the oxidation or reduction of cations.

[0084] Oxygen anions may be partially replaced by alternative electronegative anions (such as F, Cl, Br, S, Se, N, and mixtures thereof). Optionally, up to 10 atomic% or 5 atomic% of oxygen anions may be partially replaced by alternative electronegative anions.

[0085] The mixed niobium oxide is preferably in particulate form. The mixed niobium oxide may have a density (D) in the range of 0.1-100 μm, 0.5-50 μm, or 1-20 μm. 50 Particle size. These particle sizes are advantageous because they are easy to handle and fabricate into electrodes. Furthermore, these particle sizes avoid the need for complex and / or expensive methods to produce nanoscale particles. Nanoscale particles (e.g., those with a density of 100 nm or less) 50 Particles of different sizes are generally more complex to synthesize and require additional safety considerations.

[0086] The mixed niobium oxide may have a Do of at least 0.05 μm, or at least 0.1 μm, or at least 0.5 μm, or at least 1 μm. 10 Particle size. By using D 10 By maintaining particle size within these ranges, the likelihood of parasitic reactions in Li-ion battery cells decreases due to the reduced surface area, and the electrode slurry is easier to process with less binder.

[0087] Mixed niobium oxide may have a D-value not exceeding 200 μm, 100 μm, 50 μm, or 20 μm. 90 Particle size. By using D 90 By maintaining the particle size within these ranges, the proportion of large particle size distributions is minimized, making it easier to fabricate homogeneous electrodes from the material.

[0088] The term "particle size" refers to the equivalent spherical diameter (esd), that is, the diameter of a sphere with the same volume as a given particle, where particle volume should be understood to include the volume of any internal pores within the particle. The term "D" n "and "D n "Particle size" refers to a diameter such that a group of particles with an volume of n% below that diameter exists, i.e., the term "D". 50 "and "D 50 "Particle size" refers to the median particle size based on volume, below which there is a group of particles comprising 50% of the volume. In cases where the material contains primary microcrystals agglomerated into secondary particles, it should be understood that particle size refers to the diameter of the secondary particles. Particle size can be determined by laser diffraction. Particle size can also be determined according to ISO 13320:2009, for example, using Mie theory.

[0089] Mixed niobium oxide can have properties ranging from 0.1 to 100 m. 2 / g, or 0.2-50 m 2 / g, or 0.5-20 m 2The BET surface area is within the range of / g. Generally, a low BET surface area is preferred in order to minimize the reaction between the mixed niobium oxide and the electrolyte, for example, to minimize the formation of a solid electrolyte interphase (SEI) layer during the first charge-discharge cycle of the electrode containing the material. However, an excessively low BET surface area can lead to unacceptably low charge rates and capacities because the bulk of the mixed niobium oxide has limited access to metal ions in the surrounding electrolyte.

[0090] The term "BET surface area" refers to the surface area per unit mass calculated using the Brunauer-Emmett-Teller theory by measuring the physical adsorption of gas molecules on a solid surface. For example, BET surface area can be determined according to ISO 9277:2010.

[0091] Hybrid niobium oxide can be coated with carbon, for example, to improve its surface electronic conductivity and / or prevent reaction with electrolytes.

[0092] The mixed niobium oxide may have a protective coating; optionally, the protective coating comprises niobium oxide, aluminum oxide, zirconium oxide, organic or inorganic fluorides, organic or inorganic phosphates, titanium oxide, its lithiated form, and mixtures thereof.

[0093] In a first aspect, the mixed niobium oxide forms the active electrode material of the electrode, preferably the active electrode material of the lithium-ion battery anode. However, any mixed niobium oxide as defined herein can be provided as an active electrode material suitable for incorporation into an electrode. For example, the mixed niobium oxide disclosed herein can be provided as a raw material rather than as part of the electrode, for example, for sale to electrode manufacturers.

[0094] Electrodes are typically in the form of electrode compositions that are in electrical contact with the current collector, wherein the electrode composition contains a mixture of niobium oxide. Current collectors are typically metal foils, such as copper or aluminum foil.

[0095] Optionally, the mixed niobium oxide forms at least 5%, 10%, or 50% by weight of the total active electrode material in the electrode. The mixed niobium oxide may form the only active electrode material in the electrode.

[0096] The electrode composition may further comprise at least one other component selected from binders, conductive additives, different active electrode materials (e.g., further mixed niobium oxide as defined herein), and mixtures thereof. For example, an electrode composition comprises about 92% by weight of mixed niobium oxide, about 5% by weight of conductive additive (e.g., carbon black), and about 3% by weight of binder (e.g., poly(difluoroethylene)) based on the total dry weight of the electrode composition.

[0097] Examples of suitable adhesives include polyvinylidene fluoride and its copolymers (PVDF), polytetrafluoroethylene (PTFE) and its copolymers, polyacrylonitrile (PAN), poly(meth)methacrylate or poly(butyl)methacrylate, polyvinyl chloride (PVC), polyvinyl alcohol formal, polyetheramide, polymethacrylic acid, polyacrylamide, polyitacrylic acid, polystyrene sulfonic acid, polyacrylic acid (PAA) and its alkali metal salts, modified polyacrylic acid (mPAA) and its alkali metal salts, cellulose-based polymers, carboxymethyl cellulose (CMC), modified carboxymethyl cellulose (mCMC), sodium carboxymethyl cellulose (Na-CMC), polyvinyl alcohol (PVA), alginate and its alkali metal salts, butadiene-acrylonitrile rubber (NBR), hydrogenated form of NBR (HNBR), styrene-butadiene rubber (SBR), and polyimide. The adhesive may be present in the electrode composition at 0-30% by weight, 0.1-10% by weight, or 0.1-5% by weight based on the total dry weight of the electrode composition.

[0098] The conductive additive is preferably an inactive material, which is included to improve conductivity between active electrode materials and between the active electrode materials and the current collector. The conductive additive may suitably be selected from graphite, carbon black, carbon fiber, vapor-grown carbon fiber (VGCF), carbon nanotubes, graphene, acetylene black, Ketjen black, metal fibers, metal powders, and conductive metal oxides. Preferred conductive additives include carbon black and carbon nanotubes. The conductive additive may be present in the electrode composition at 0-20% by weight, 0.1-10% by weight, or 0.1-5% by weight based on the total dry weight of the electrode composition.

[0099] The active electrode material can be present in the electrode composition at 100-50% by weight, 99.8-80% by weight, or 99.8-90% by weight based on the total dry weight of the electrode composition. When the active electrode material is present at 100% by weight of the electrode composition, it can be used in a solid-state electrode.

[0100] When different active electrode materials exist in addition to mixed niobium oxide, the active electrode materials can be selected from lithium titanium oxide, titanium niobium oxide, different mixed niobium oxides, graphite, hard carbon, soft carbon, silicon, their doped forms, and mixtures thereof.

[0101] Hybrid niobium oxide can be combined with lithium titanium oxide to form active electrode materials.

[0102] Lithium titanium oxides preferably have a spinel or orthorhombic manganese oxide crystal structure, for example, as determined by X-ray diffraction. An example of a lithium titanium oxide with a spinel crystal structure is Li₄Ti₅O₅. 12An example of lithium titanium oxides with an orthorhombic manganese oxide crystal structure is Li₂Ti₃O₇. These materials have been shown to have good properties for use as active electrode materials. Therefore, lithium titanium oxides can have the same structure as determined by X-ray diffraction as Li₄Ti₅O₇. 12 And / or the crystal structure of Li₂Ti₃O₇. Lithium titanium oxide may be selected from Li₄Ti₅O₇. 12 Li2Ti3O7 and its mixtures.

[0103] Lithium titanium oxides may be doped with additional cations or anions. Lithium titanium oxides may be oxygen-deficient. Lithium titanium oxides may form coatings, optionally wherein the coating is selected from carbon, polymers, metals, metal oxides, metalloids, phosphates, and fluorides.

[0104] Lithium titanium oxides can be synthesized using conventional ceramic techniques, such as solid-state synthesis or sol-gel synthesis. Alternatively, lithium titanium oxides can be obtained from commercial suppliers.

[0105] Lithium titanium oxide is preferably in particulate form. The lithium titanium oxide may have a density (D) in the range of 0.1-50 μm, or 0.25-20 μm, or 0.5-15 µm. 50 Particle size. Lithium titanium oxide may have a density of at least 0.01 μm, or at least 0.1 μm, or at least 0.5 μm. 10 Particle size. Lithium titanium oxides may have a D particle size not exceeding 100 μm, 50 μm, or 25 μm. 90 Particle size. By using D 90 Maintaining the particle size within this range improves the packing of lithium titanium oxide particles in a mixture with mixed niobium oxide particles.

[0106] Due to the low electronic conductivity of the material, lithium titanium oxide is typically used in battery anodes with small particle sizes. Conversely, mixed niobium oxide, as defined herein, can be used with larger particle sizes because it typically has a higher lithium-ion diffusion coefficient than lithium titanium oxide. Advantageously, in the composition, lithium titanium oxide can have a smaller particle size than mixed niobium oxide, for example, making the Dx of the lithium titanium oxide... 50 Particle size and D of mixed niobium oxide 50 The particle size ratio is in the range of 0.01:1 to 0.9:1, or 0.1:1 to 0.7:1. In this way, smaller lithium titanium oxide particles can be accommodated in the voids between larger mixed niobium oxide particles, thereby improving the filling efficiency of the composition.

[0107] Lithium titanium oxide can have properties ranging from 0.1 to 100 μm. 2 / g, or 1-50 m 2 / g, or 3-30 m 2 BET surface area within the range of / g.

[0108] The mass ratio of lithium titanium oxide to mixed niobium oxide can range from 0.5:99.5 to 99.5:0.5, preferably from 2:98 to 98:2. In one embodiment, the active electrode material comprises a higher proportion of lithium titanium oxide than the mixed niobium oxide (e.g., a mass ratio of at least 2:1, at least 5:1, or at least 8:1). Advantageously, this allows for the incremental introduction of mixed niobium oxide into existing lithium titanium oxide-based electrodes without requiring significant changes to the manufacturing technology, thus providing an effective way to improve the properties of existing electrodes. In another embodiment, the active electrode material has a higher proportion of mixed niobium oxide than the lithium titanium oxide, for example, such that the mass ratio of lithium titanium oxide to mixed niobium oxide is less than 1:2, or less than 1:5, or less than 1:8. Advantageously, this allows for a reduction in the cost of the active electrode material by replacing some of the mixed niobium oxide with lithium titanium oxide.

[0109] Hybrid niobium oxide can be combined with niobium oxide to form active electrode materials. Niobium oxide can be selected from Nb. 12 O 29 Niobium oxide is NbO2, NbO, and Nb2O5. Preferably, niobium oxide is Nb2O5.

[0110] Niobium oxide can be doped with additional cations or anions, for example, assuming that the crystal structure of niobium oxide corresponds to an oxide composed of Nb and O (e.g., Nb). 12 O 29 Niobium oxide has a crystal structure of NbO2, NbO, and Nb2O5. Niobium oxide can be oxygen-deficient. Niobium oxide can form a coating, optionally wherein the coating is selected from carbon, polymers, metals, metal oxides, metalloids, phosphates, and fluorides.

[0111] Niobium oxide can have Nb 12 O 29 The crystal structure of niobium oxide (NbO2, NbO, or Nb2O5) is determined by X-ray diffraction. For example, niobium oxide may have an orthorhombic Nb2O5 crystal structure or a monoclinic Nb2O5 crystal structure. Preferably, niobium oxide has a monoclinic Nb2O5 crystal structure, and most preferably, an H-Nb2O5 crystal structure. Further information on the crystal structure of Nb2O5 can be found in Griffith et al., J. Am. Chem. Soc. 2016, 138, 28, 8888–8899.

[0112] Niobium oxide can be synthesized using conventional ceramic techniques, such as solid-state synthesis or sol-gel synthesis. Alternatively, niobium oxide can be obtained from commercial suppliers.

[0113] Niobium oxide is preferably in particulate form. Niobium oxide may have a density (D) in the range of 0.1-100 μm, 0.5-50 μm, or 1-20 μm. 50 Particle size. Niobium oxide may have a density of at least 0.05 μm, or at least 0.5 μm, or at least 1 μm. 10 Particle size. Niobium oxide can have a D particle size not exceeding 100 μm, 50 μm, or 25 μm. 90 Particle size. By using D 90 Maintaining the particle size within this range improves the packing of niobium oxide particles in a mixture with mixed niobium oxide particles.

[0114] Niobium oxide can have a range of 0.1-100 μm. 2 / g, or 1-50 m 2 / g, or 1-20 m 2 BET surface area within the range of / g.

[0115] The mass ratio of niobium oxide to mixed niobium oxide can 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.

[0116] This invention also provides the use of mixed niobium oxide as defined herein in the anode of a metal-ion battery, optionally wherein the metal-ion battery is a lithium-ion or sodium-ion battery, preferably a lithium-ion battery. Lithium-ion batteries include liquid-based batteries, polymer-based batteries, semi-solid-based batteries, and all-solid-state batteries.

[0117] A further embodiment of the invention is an electrochemical device comprising an anode, a cathode, and an electrolyte disposed between the anode and the cathode, wherein the anode comprises an active electrode material according to a first aspect of the invention; optionally, the electrochemical device is a metal-ion battery, such as a lithium-ion battery or a sodium-ion battery. For example, the anode may be an electrode according to a first aspect of the invention. Preferably, the electrochemical device is a lithium-ion battery having a reversible anode active material specific capacity greater than 180 mAh / g at 20 mA / g, wherein the battery is capable of charging and discharging at current densities of 200 mA / g or greater, or 1000 mA / g or greater, or 2000 mA / g or greater, or 4000 mA / g or greater relative to the anode active material, while retaining greater than 70% of the initial cell capacity at 20 mA / g. It has been found that using the active electrode material of the first aspect of the invention can produce lithium-ion batteries with such a combination of properties, representing lithium-ion batteries particularly suitable for applications requiring high charge and discharge current densities. Notably, examples have shown that the active electrode material according to the first aspect of the invention exhibits excellent capacity retention at high C-rates.

[0118] Electrochemical devices preferably have an N / P ratio > 1, where N / P is defined as:

[0119]

[0120] in:

[0121] Area loading (mg / cm-) 2 () is the dry loading of the electrode composition, without considering the current collector;

[0122] The active fraction (wt%) is the percentage of the dry electrode composition that serves as the active material;

[0123] First lithiation / delithiation capacity (mAhg) -1 ) is the specific capacity at C / 10 at 25°C, measured on an equivalent half-cell cell with a lithium metal counter electrode, during the first lithiation cycle of the anode or the first delithiation cycle of the cathode.

[0124] The first lithiation / delithiation capacity was measured on an equivalent half-cell unit. An equivalent half-cell unit can be understood as utilizing the same electrode composition deposited with the same areal loading and activity fraction as a full-cell unit. For the anode, the first constant current C / 10 lithiation (discharge, negative current) capacity (relative to Li / Li+) was measured at 25°C. For the cathode, the first constant current C / 10 delithiation (charge, positive current) capacity (relative to Li / Li+) was measured at 25°C.

[0125] N / P is preferably greater than 1, for example, ≥1.01. N / P can be in the range of >1-2, or 1.01-1.5, or most preferably 1.05-1.3.

[0126] The cathode comprises an active cathode material, which may be selected from LiNi. 1-x M x O2-based nickel-based oxides (where M = Co, Mn, Al), such as NMC (lithium nickel manganese cobalt oxide), NCA (lithium cobalt aluminum oxide), and LCO (lithium cobalt oxide); and LNMO (lithium nickel manganese oxide) (e.g., LiNi). 0.5 Mn 1.5 O4). For example, the active cathode material can be lithium nickel manganese cobalt oxide. Active cathode materials are widely available from commercial suppliers. Active cathode materials may be doped with additional cations and / or anions.

[0127] The choice of active electrode material can affect the appropriate voltage range, including for determining the initial lithiation / delithiation capacity. For example, an appropriate voltage range could be: LNMO: 5.2–3V, with an upper limit of 5.2V; NCA, NMC, and LCO: 4.5–2.7V, with an upper limit of 4.5V; mixed niobium oxide: 3–0V, with a lower limit of 0V. A narrower range could be: LNMO: 5–3V, with an upper limit of 5V; NCA, NMC, and LCO: 4.3–2.7V, with an upper limit of 4.3V; mixed niobium oxide: 3V–1.0V, with a lower limit of 1.0V.

[0128] An appropriate voltage range can be determined empirically. For example, the voltage distribution is related to changes in the energy states of the anode and cathode materials, which are associated with the removal or insertion of electrons and ions. The cutoff voltage of the cell can be chosen to decrease before a specific inflection point in the voltage distribution, corresponding to an energy state rise of one or both electrodes above a critical level that causes the crystal structure to decay to a lower energy structure at a rate significantly detrimental to cell performance. The absolute voltage at which this occurs is a function of the electrode potentials of the two electrodes, but can be calculated using a common reference electrode and, for well-established families of materials with reliable standard electrochemical behavior, does not need to be determined experimentally.

[0129] The cathode active material is preferably in particulate form, for example, having a D0.05 in the range of 0.1-100 μm, 0.5-50 μm, or 1-20 μm. 50 Particle size.

[0130] The electrolyte may comprise any material suitable for metal-ion battery operation, preferably lithium-ion battery operation. For example, the electrolyte may be a non-aqueous solution (e.g., an organic electrolyte solution). The electrolyte may contain one or more non-aqueous solvents and a salt at least partially dissolved in the solvent. For example, the solvent may include organic solvents, such as ethylene carbonate (EC) and / or other carbonate-based solvents, or butyrate, or acetate, or mixtures thereof. The solvent may contain 1 M LiPF6 dissolved in a mixture of aprotic solvents, such as a 1:1 weight ratio of ethylene carbonate and other carbonate-based solvents or a mixture of butyrate or acetate.

[0131] Salts suitable for use in this invention include LiPF6, LiSbF6, LiBF4, LiTFSI, LiFSI, LiAlCl4, LiAsF6, LiClO4, LiGaCl4, LiC(SO2CF3)3, LiN(CF3SO2)2, Li(CF3SO3), LiB(C6H4O2)2, LiBOB (lithium bis(oxalate)borate) and LiDFOB (lithium difluoro(oxalate)borate). Low-viscosity solvents (e.g., organic solvents) suitable for electrolytes may include, but are not limited to, ethyl methyl carbonate (EMC), dioxane (DOL), ethyl acetate (EA); propylene acetate (PA); butyl acetate (BA); methyl butyrate (MB); ethyl butyrate (EB); dimethyl carbonate (DMC); diethyl carbonate (DEC); 1,2-dimethoxyethane (DME); tetrahydrofuran (THF); methyl acetate (MA); diethylene glycol dimethyl ether (DGL); triethylene glycol dimethyl ether; tetraethylene glycol dimethyl ether; cyclic carbonates; cyclic esters; cyclic amides; propylene carbonate (PC); methyl propyl carbonate (MPC); acetonitrile; dimethyl sulfoxide (DMS); dimethylformamide; dimethylacetamide; γ-butyrolactone (GBL); and N-methylpyrrolidone (NMP); and various mixtures or combinations thereof.

[0132] Hybrid niobium oxide can be synthesized using conventional ceramic techniques. For example, it can be obtained through one or more of solid-state synthesis or sol-gel synthesis. Hybrid niobium oxide can also be synthesized through one or more commonly used alternative techniques, such as hydrothermal or microwave hydrothermal synthesis, solvothermal or microwave solvothermal synthesis, coprecipitation synthesis, spark or microwave plasma synthesis, combustion synthesis, electrospinning, spray pyrolysis, chemical vapor deposition, atomic layer deposition, and mechanical alloying.

[0133] Mixed niobium oxide can be provided by a method comprising the following steps: providing one or more precursor materials; mixing the precursor materials to form a precursor material mixture; and heat-treating the precursor material mixture in a temperature range of 400°C-1350°C or 800°C-1250°C, thereby providing mixed niobium oxide.

[0134] To provide a mixed niobium oxide containing additional electronegative anions other than oxygen, the method may further include the steps of: mixing the mixed niobium oxide with a precursor containing additional electronegative anions to provide a further precursor material mixture; and optionally heat-treating the further precursor material mixture under reducing conditions at a temperature range of 300-1200°C or 800-1100°C to provide the mixed niobium oxide containing additional electronegative anions.

[0135] For example, to provide a N-containing mixed niobium oxide, the method may further include the steps of: mixing the mixed niobium oxide with a N-containing precursor (e.g., melamine or urea) to provide a further precursor material mixture; and heat-treating the further precursor material mixture under reducing conditions (e.g., under N2) in a temperature range of 300°C to 1200°C to provide a N-containing mixed niobium oxide.

[0136] For example, to provide a mixed niobium oxide containing F, the method may further include the steps of: mixing the mixed niobium oxide with an F-containing precursor (e.g., polyvinylidene fluoride or NH4F) to provide a further precursor material mixture; and heat-treating the further precursor material mixture under oxidizing conditions (e.g., in air) in a temperature range of 300°C to 1200°C to provide a mixed niobium oxide containing F.

[0137] The method may include a further step of heat-treating the mixed niobium oxide under reducing conditions at a temperature in the range of 400-1350°C or 800-1250°C to induce oxygen vacancies in the mixed niobium oxide.

[0138] Precursor materials used to prepare mixed niobium oxide may include one or more metal oxides, metal hydroxides, metal salts, or ammonium salts. For example, precursor materials may include one or more metal oxides or metal salts with different oxidation states and / or different crystal structures. Examples of suitable precursor materials include, but are not limited to: Nb₂O₅, Nb(OH)₅, niobic acid, NbO, ammonium oxalate niobate, NH₄H₂PO₄, (NH₄)₂PO₄, (NH₄)₃PO₄, P₂O₅, H₃PO₃, Ta₂O₅, WO₃, ZrO₂, TiO₂, MoO₃, V₂O₅, ZrO₂, CuO, ZnO, Al₂O₃, K₂O, KOH, CaO, GeO₂, Ga₂O₃, SnO₂, CoO, Co₂O₃, Fe₂O₃, Fe₃O₄, MnO, MnO₂, NiO, Ni₂O₃, H₃BO₃, ZnO, Li₂CO₃, Na₂CO₃, H₃BO₃, NiO, Mg₅(CO₃)₄(OH)₂·5H₂O, and MgO. Precursor materials may not contain metal oxides, or may contain ion sources other than oxides. For example, the precursor material may contain a metal salt (e.g., NO3). - SO3 - ) or other compounds (e.g., oxalates, carbonates). For the substitution of oxoanions with other electronegative anions, the precursor may include one or more organic compounds, polymers, inorganic salts, organic salts, gases, or ammonium salts; examples include, but are not limited to: melamine, NH4HCO3, NH3, NH4F 、 PVDF, PTFE, NH4Cl, NH4Br, NH4I, Br2, Cl2, I2, ammonium oxychloride amide, and hexamethylenetetramine.

[0139] When it is desired to prepare a mixed niobium oxide containing cations of a specific oxidation state, a precursor containing cations in that oxidation state can be selected. For example, when preparing a mixed niobium oxide containing Mn... 2+ When preparing mixed niobium oxide, MnO can be used as a precursor. 4+ When mixing niobium oxides, MnO2 can be used as a precursor.

[0140] Some or all of the precursor materials may be particulate materials. Where they are particulate materials, preferably, they have a diameter less than 20 μm (e.g., 10 nm to 20 µm). 50Particle size. Providing particulate materials with this particle size can help promote a more compact mixing of precursor materials, resulting in a more efficient solid-state reaction during the heat treatment step. However, it is not necessary for the precursor materials to have an initial particle size of <20 µm in diameter, as the particle size of one or more precursor materials can be mechanically reduced during the step of mixing the precursor materials to form a precursor material mixture.

[0141] The step of mixing precursor materials to form precursor material mixtures and / or further precursor material mixtures can be carried out by processes selected from: dry or wet / solventized planetary ball milling, rolling ball milling, high-energy ball milling, bead milling, pin milling, classification steps, high-shear grinding, air jet milling, steam jet milling, planetary mixing, powder filling, and / or impact milling. The force used for mixing / milling may depend on the morphology of the precursor materials. For example, some or all of the precursor materials have a large particle size (e.g., D > 20 µm). 50 In the case of particle size, the grinding force can be selected to reduce the particle size of the precursor material, thereby reducing the particle size of the precursor material mixture to 20 µm or less in diameter. When the particle size in the precursor material mixture is 20 µm or less, this can promote more efficient solid-state reaction of the precursor material in the precursor material mixture during the heat treatment step. Solid-state synthesis can also be carried out in pellets formed from precursor powder under high pressure (>10 MPa).

[0142] The heat treatment step of the precursor material mixture and / or further precursor material mixture may be performed for 1 hour to 24 hours, more preferably 3 hours to 18 hours. For example, the heat treatment step may be performed for 1 hour or longer, 2 hours or longer, 3 hours or longer, 6 hours or longer, or 12 hours or longer. The heat treatment step may be performed for 24 hours or less, 18 hours or less, 16 hours or less, or 12 hours or less.

[0143] The heat treatment step of the precursor material mixture can be performed in a gaseous atmosphere, preferably air. Suitable gaseous atmospheres include air, N2, Ar, He, CO2, CO, O2, H2, NH3, and mixtures thereof. The gaseous atmosphere can be a reducing atmosphere. When it is desired to prepare an oxygen-deficient material, the heat treatment step of the precursor material mixture is preferably performed in an inert or reducing atmosphere.

[0144] The step of further heat treatment of the precursor material mixture can be performed under reducing conditions. 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, the step of further heat treatment of the precursor material mixture includes heating under an inert gas.

[0145] Optionally, a further step of heat treatment of the mixed niobium oxide and / or the mixed niobium oxide containing additional electronegative anions under reducing conditions may be performed for 0.5 hours to 24 hours, more preferably 2 hours to 18 hours. For example, the heat treatment step may be performed for 0.5 hours or longer, 1 hour or longer, 3 hours or longer, 6 hours or longer, or 12 hours or longer. Further steps of the heat treatment may be performed 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.

[0146] In some methods, performing a two-step heat treatment may be advantageous. For example, a precursor material mixture and / or a further precursor material mixture may be heated at a first temperature for a first time length, followed by heating at a second temperature for a second time length. Preferably, the second temperature is higher than the first temperature. Performing such a two-step heat treatment can facilitate a solid-state reaction to form the desired crystal structure. This can be done sequentially or in the presence of an intermediate regrinding step.

[0147] The method may include one or more post-treatment steps following the formation of the mixed niobium oxide. In some cases, the method may include a post-treatment step of heat-treating the mixed niobium oxide, sometimes referred to as 'annealing'. This post-treatment heat treatment step may be performed in a different gas atmosphere than the step of heat-treating the precursor material mixture to form the mixed niobium oxide. The post-treatment heat treatment step may be performed in an inert or reducing gas atmosphere. This post-treatment heat treatment step may be performed at a temperature above 500°C, for example, at about 900°C. Incorporating a post-treatment heat treatment step may facilitate, for example, the formation of vacancies or defects in the mixed niobium oxide, such as inducing oxygen deficiency; or anion exchange on the formed mixed niobium oxide, such as exchanging O anions with N.

[0148] The method may include the following steps: grinding and / or classifying the mixed niobium oxide (e.g., impact milling, jet milling, steam jet milling, high-energy milling, high-shear milling, pin milling, air classification, wheel classification, sieving, cyclone separation, bead milling) to provide material having any of the particle size parameters given above.

[0149] This invention provides a method for manufacturing an electrode, the method comprising providing a mixed niobium oxide as defined herein; and depositing the mixed niobium oxide onto a current collector to form an electrode. Providing the mixed niobium oxide may include synthesizing the mixed niobium oxide by the method provided herein. The deposition step may include forming a slurry of the mixed niobium oxide and a solvent. The slurry may contain at least one other component selected from binders, conductive additives, different active electrode materials, and mixtures thereof. The slurry may be deposited onto a current collector and the solvent removed to form an electrode layer on the current collector. Further steps may be performed as appropriate, such as heat treatment for curing any binder and / or calendering of the electrode layer. For example, the solvent may be removed by drying at a temperature of, for example, 30-100°C. The electrode may be calendered to 2-3.5 or 2.6-2.9 g cm⁻¹. -3 The electrode layer may have a thickness ranging from 5 µm to 2 mm, preferably from 5 µm to 1 mm, preferably from 5 µm to 500 µm, preferably from 5 µm to 200 µm, preferably from 5 µm to 100 µm, and preferably from 5 µm to 50 µm.

[0150] Alternatively, the slurry can be molded into a self-supporting membrane or pad containing mixed niobium oxide, for example, by casting the slurry onto a suitable casting mold, removing the solvent, and then removing the casting mold. The resulting membrane or pad takes the form of a cohesive, self-supporting block, which can then be bonded to a current collector by known methods.

[0151] Example

[0152] Mixed niobium oxide was synthesized via a solid-state route. For example, appropriate amounts of Nb₂O₅ and precursor materials were mixed and ground using a pestle and mortar or an impact mill to form a homogeneous precursor mixture. The resulting mixture was then heated to a high temperature (>800 °C) in an alumina crucible at a heating rate between 5–10 °C / min and held for 6–12 h. This process was repeated until the desired single phase (4 × 4 Wadsley-Roth block structure) was observed in the X-ray diffraction pattern. Specifically, stoichiometric amounts of precursor materials (Nb₂O₅, Li₂CO₃, Na₂CO₃, H₃BO₃, TiO₂, Al₂O₃, Fe₂O₃, Cr₂O₃, NiO, and Mg₅(CO₃)₄(OH)₂·5H₂O) were mixed and hand-ground in a pestle and mortar for 15 minutes (approximately 5 g) or ground using an impact mill at 20,000 rpm for 4 minutes (approximately 50 g). The resulting powder was placed in an alumina crucible and heat-treated in air in a muffle furnace at T1 = 875-1150 °C, optionally 900-1150 °C, for 6-12 h. All heating steps were performed at a heating rate of 5 °C / min. Optionally, an additional grinding and heat treatment step T2 was performed to improve phase purity. Following this, a final grinding step was performed using a pestle and mortar or an impact mill to depolymerize the powder. The composition and synthesis parameters are summarized in Table 1.

[0153]

[0154] Table 1: Summary of synthesized materials

[0155] Material characterization

[0156] Phase purity of samples was analyzed using a Rigaku Miniflex powder X-ray diffractometer in the 2θ range (10–70°) at a scan rate of 1° / min, or using a Bruker D8 powder diffractometer in the 2θ range (10–50° or 10–60°) (step size 0.0189°, step time 0.42 s).

[0157] Figure 1 and Figure 3 The measured XRD diffraction patterns of the selected samples are shown. Figure 2 A TEM micrograph showing the obtained highly crystalline structure is shown. Table 2 provides the unit cell parameters obtained from the Pawley refinement based on the N-Nb2O5 structure.

[0158]

[0159] Table 2: Summary of the unit cell parameters of the sample calculated based on Pawley refinement in Topas software.

[0160] Electrochemical characterization

[0161] The charging rate of a Li-ion battery cell is typically expressed as "C-rate". A 1C charging rate refers to the charging current required to fully charge the battery cell in one hour, while a 10C charging rate refers to a full charge in 1 / 10 (6 minutes) of one hour. The C-rate here is defined based on the reversible capacity of the anode observed within the voltage limit applied during the second cycle of delithiation at the anode; specifically, it represents a capacity of 1.0 mAh cm⁻¹ within a voltage limit of 1.1–3.0 V. -2 The capacity of the anode, with a 1C rate corresponding to an applied 1.0 mA cm⁻¹ -2 The current density. In typical materials as described herein, this corresponds to approximately 185 mA / g of active material.

[0162] Electrochemical tests were performed in a half-button cell (CR2032 size) for analysis. In the half-button test, the active material was tested in an electrode relative to the Li metal electrode to evaluate its basic performance. In the following examples, the active material composition to be tested was combined with N-methylpyrrolidone (NMP), carbon black (Super P) as a conductive additive, and a poly(difluoroethylene) (PVDF) binder, and mixed using a laboratory-scale centrifugal planetary mixer to form a slurry. The non-NMP composition of the slurry was 92 wt% active material, 5 wt% conductive additive, and 3 wt% binder. The slurry was coated onto an Al foil current collector by doctor blade coating up to 50-100 gm. -2 The desired loading was achieved, and the electrode was dried by heating. It was then rolled to 2.6–2.9 g cm⁻¹ at 80 °C. -3 The density was adjusted to achieve a target porosity of 35-47%. Electrodes were stamped to the desired dimensions and assembled with a separator (Celgard porous PP / PE), Li metal, and electrolyte (1.3 M LiPF6 in EC / DEC) within a steel button cell housing and sealed under pressure. The cells were then cycled at 25°C at low current rates (C / 10) between 1.1 and 3.0 V to achieve two complete lithiation and delithiation cycles. Following this, the cell performance was tested at increased current densities. During these tests, the cells were subjected to asymmetric cycling at 25°C, where slow lithiation (C / 5) was followed by increased delithiation rates (e.g., 1C, 5C, 10C) to provide capacity retention.

[0163] Data from 3 to 5 battery cells prepared with the same electrode coating were averaged, with errors expressed as standard deviations. Therefore, these data represent a robust study demonstrating improvements achieved by the material according to the invention compared to previous materials. These data are shown in Tables 3 and 4. Voltage versus charge / discharge state curves for samples 1 and 18 are shown in... Figure 4 middle.

[0164] For homogeneous, smooth coatings on Cu and Al current collector foils, the coatings, free of visible defects or agglomerates, can also be prepared using a centrifugal planetary mixer, as described above for these samples, into compositions of up to 94 wt% active material, 4 wt% conductive additives, and 2 wt% binder. These can be prepared using PVDF (i.e., NMP-based) and CMC:SBR-based (i.e., water-based) binder systems. (The last part, "1.0 to 5.0 mAh cm⁻¹", appears to be an error and can be omitted.) -2 Under certain loads, the coatings can be calendered to a porosity of 35% to 40% for PVDF at 80°C and for CMC:SBR at 50°C. This is important for demonstrating the feasibility of these materials in high-energy and high-power applications with high levels of active materials.

[0165]

[0166] Table 3: Electrode performance at C / 10 after two complete lithiation and delithiation cycles between 1.1 and 3.0 V.

[0167]

[0168] Table 4: Electrode performance under increasing current density

[0169] discuss

[0170] The hybrid niobium oxide according to the invention has been found to exhibit remarkable properties at high delithiation rates, such as 5C and 10C. In particular, in some cases, the specific capacity at lower rates is largely retained at higher rates, for example, the capacity at 10C is 97.7% or higher of the capacity at 0.5C; this is an extremely high capacity retention. These are important results demonstrating the advantages of the hybrid niobium oxide of the invention for designing high-power batteries for fast charging / discharging.

Claims

1. An electrode comprising a mixed niobium oxide as an active electrode material, wherein the mixed niobium oxide has a Wadsley-Roth block structure comprising 4×4 octahedral blocks, wherein the mixed niobium oxide has formula B a M v z Nb 100-a-z O 250-a ,in M V It is a cation with an average oxidation state of 5, wherein M V Selected from Mn, Fe, Al, Ga, Y, In, La, Yb, Cu, Zn, Mg, Ni, Co, Ca, Ce, Zr, Ti, Sn, Ge, Si, V, P, Ta, W, Mo, Cr and mixtures thereof; 0 ≤ z ≤ 10； 0 < a ≤ 8。 2. The electrode according to claim 1, wherein: (i) 1 ≤ a ≤ 5; or (ii) 1.5 ≤ a ≤ 3; or (iii) a = 2.

3. The electrode according to claim 1, wherein: (i) M V Selected from Ce, Zr, Ti, Sn, Ge, Si, V, P, Ta, W, Mo, Cr and mixtures thereof; or (ii) M V Selected from V, P, Ta and their mixtures.

4. The electrode according to claim 1, wherein M is formed V All of the cations have an oxidation state of 5.

5. The electrode according to claim 1, wherein: (i) 0 ≤ z ≤ 5; and / or (ii) z > 0; or (iii) z = 0.

6. An electrode comprising a mixed niobium oxide as an active electrode material, wherein the mixed niobium oxide has a Wadsley-Roth block structure comprising 4×4 octahedral blocks, wherein the mixed niobium oxide has the formula M b Nb 100-b O 250-2.5b+bc ,in M is a cation selected from P, B, W, Mo, V, Ti, Si and mixtures thereof; c is half the average oxidation state of M; 1.5 ≤ c ≤ 3; and 0.5 < b ≤ 6。 7. The electrode according to claim 6, wherein the strongest peak in the X-ray diffraction pattern of the material having a CuKα source has a full width at half maximum (FWHM) of >0.2 between 18.15 and 18.65° 2θ, optionally wherein the FWHM is >0.4, >0.6, and / or <0.

9.

8. The electrode according to claim 6, wherein M is selected from P, W, Ti, B and mixtures thereof; or P, W and mixtures thereof.

9. The electrode according to claim 1 or claim 6, wherein the cation is partially replaced by cations of different oxidation states; optionally, up to 20 atomic percent of the cation is replaced by cations of different oxidation states.

10. The electrode according to claim 1 or claim 6, wherein the oxygen anions are partially replaced by electronegative anions such as F, Cl, Br, S, Se, N and mixtures thereof; optionally, up to 10 atomic percent of the oxygen anions have been partially replaced by electronegative anions.

11. The electrode according to claim 1 or claim 6, wherein the mixed niobium oxide has a Dx in the range of 0.1-100 μm, or 0.5-50 μm, or 1-20 µm. 50 Particle size.

12. The electrode according to claim 1 or claim 6, wherein the mixed niobium oxide has a content of 0.1-100 μm. 2 / g, or 0.2-50 m 2 / g, or 0.5-20 m 2 BET surface area within the range of / g.

13. The electrode according to claim 1 or claim 6, wherein the mixed niobium oxide is coated with carbon.

14. The electrode according to claim 1 or claim 6, wherein the mixed niobium oxide has a protective coating; optionally, wherein the protective coating comprises niobium oxide, aluminum oxide, zirconium oxide, organic and inorganic fluorides, organic and inorganic phosphates, titanium oxide, its lithiated form, and mixtures thereof.

15. The electrode according to claim 1 or claim 6, wherein the mixed niobium oxide has a monoclinic crystal structure; optionally, wherein the mixed niobium oxide has cell parameters a = 25.7-31.4 Å, b = 3.4-4.2 Å, c = 15.8-19.3 Å, α = 90°, γ = 112.6-137.6°, and γ = 90°.

16. The electrode according to claim 1 or claim 6, wherein the crystal structure of the mixed niobium oxide corresponds to the crystal structure of N-Nb2O5.

17. The electrode according to claim 1 or claim 6, wherein the mixed niobium oxide forms at least 5%, 10%, or 50% by weight of the total active electrode material in the electrode; or wherein the mixed niobium oxide is the only active electrode material in the electrode.

18. The electrode according to claim 1 or claim 6, further comprising at least one other component selected from binders, conductive additives, different active electrode materials and mixtures thereof.

19. The electrode of claim 18, wherein the different active electrode materials are selected from lithium titanium oxide, titanium niobium oxide, different mixed niobium oxides, graphite, hard carbon, soft carbon, silicon, their doped and / or carbon-coated forms, and mixtures thereof.

20. A metal-ion battery comprising the electrode of any one of claims 1 to 19, optionally wherein the metal-ion battery is a lithium-ion battery, and said electrode forms an anode.

21. The metal-ion battery of claim 20, wherein the metal-ion battery is a lithium-ion battery having a reversible anode active material specific capacity of greater than 180 mAh / g at 20 mA / g, wherein the battery is capable of charging and discharging at a current density of 200 mA / g or greater, or 1000 mA / g or greater, or 2000 mA / g or greater, or 4000 mA / g or greater relative to the anode active material, while retaining greater than 70% of the initial battery cell capacity at 20 mA / g.

22. An electrochemical device comprising an anode, a cathode, and an electrolyte disposed between the anode and the cathode, wherein the anode comprises a mixed niobium oxide as an active anode material according to any one of claims 1 to 16, wherein the device has an N / P ratio >1, wherein N / P is defined as: in: Area loading (mg / cm-) 2 () is the dry loading of the electrode composition, without considering the current collector; The active fraction (wt%) is the percentage of the dry electrode composition that serves as the active material; First lithiation / delithiation capacity (mAhg) -1 ) is the specific capacity at C / 10 at 25°C, measured on an equivalent half-cell cell with a lithium metal counter electrode, during the first lithiation cycle of the anode or the first delithiation cycle of the cathode.

23. The use of the mixed niobium oxide according to any one of claims 1 to 16 in a metal-ion battery; optionally as an active electrode material in the anode of a lithium-ion battery.

24. A method for manufacturing an electrode, the method comprising: Provides a mixed niobium oxide as claimed in any one of claims 1 to 16; as well as The mixed niobium oxide is deposited onto the current collector to form the electrode.

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