Active Electrode Material

Abstract

The present invention relates to a mixed phase oxide for use as an active electrode material, for example in a lithium-ion or sodium-ion battery, comprising Nb and Ti, and further comprising M(III) and / or M(II), wherein M(III) is selected from Cr, Al, Ga, and mixtures thereof, and M(II) is selected from Zn, Cu, Mg, and mixtures thereof, the mixed phase oxide comprising an interpenetrating mixture of a first phase and a second phase, the first phase having a crystal structure of TiNb2O7, the second phase having a crystal structure of Zn2Nb 34 O 87 It has a crystal structure of:

Description

Technical Field

[0001] The present invention relates to an active electrode material, a method for manufacturing the active electrode material, and an electrode including the active electrode material. Such substances are, for example, substances of interest as anode materials and as active electrode materials for metal ion batteries, such as lithium ion batteries or sodium ion batteries.

Background Art

[0002] Lithium ion (Li ion) batteries are a type of commonly used rechargeable battery, and the global market is predicted to grow to $200 billion by 2030. Li ion batteries are an optimal technology for electric vehicles with multiple requirements from technical capabilities to environmental impacts, and offer a feasible path towards an environmentally friendly automotive industry.

[0003] A typical lithium ion battery is composed of a plurality of cells connected in series or parallel. Each cell usually consists of an anode (negative electrode) and a cathode (positive electrode), separated by a porous electrical insulating membrane (referred to as a separator), and immersed in a liquid (referred to as an electrolyte) that enables the transport of lithium ions.

[0004] In most systems, the electrodes are composed of an active electrode material, which means that they can react chemically with lithium ions and reversibly occlude and release them in a controlled state, and this is mixed with a conductive additive (such as carbon) and a polymer binder as required. A slurry of these components is coated as a thin film on a current collector (generally a thin foil of copper or aluminum), thereby forming the electrode when dried.

[0005] In known lithium-ion battery technology, the graphite anode has limitations in terms of safety during battery charging, which has been a major obstacle to applications in high-power electronic devices, automobiles, and industries. Among various recently proposed promising alternatives, lithium titanate (LTO) and niobium mixed oxides are strong candidates as active materials that are optimal for high-power and fast-charging applications to replace graphite.

[0006] Batteries that rely on graphite anodes are fundamentally limited in terms of the charging rate. Under nominal conditions, lithium ions are inserted into the anode active material during charging. As the charging rate increases, the typical voltage profile of graphite makes it highly likely that the potential at the anode site will become lower than 0 V with respect to Li / Li+ due to overvoltage, causing a phenomenon called lithium dendrite electroplating where lithium ions are instead deposited on the surface of the graphite electrode as metallic lithium. As a result, active lithium is irreversibly lost, and thus the cell capacity rapidly decreases. In some cases, these dendritic deposits grow to a very large size, which may penetrate the cell separator and lead to a short circuit of the cell. This can trigger the cell to suddenly fail, sometimes resulting in fire or explosion. Therefore, in the fastest-charging-capable batteries with graphite anodes, the charging rate is limited to 5 - 7C, but usually much lower than that.

[0007] Lithium titanate (LTO) anodes are not affected by dendrite electroplating at high charge rates due to their high potential (1.6 V vs. Li / Li+), and because they correspond to a 3D crystal structure, they are not affected by significant volume expansion of the active material during lithium-ion intercalation, so they have excellent cycle life. For these two reasons, LTO cells are generally regarded as highly safe cells. However, since LTO is a relatively poor electronic and ionic conductor, there are limitations to the capacity retention rate at high rates and the achievable power capabilities unless the material is nanosized to increase the specific surface area and carbon-coated to increase the electronic conductivity. This particle-level materials engineering increases the porosity and specific surface area of the active material, and significantly reduces the achievable packing density in the electrode. This is because the density of the electrode decreases, the proportion of electrochemically inert materials (such as binders, carbon additives) increases, leading to a significant decrease in the weight energy density and volume energy density.

[0008] An important indicator of the anode's ability is the volume specific capacity of the electrode (mAh / cm 3 ), that is, the amount of charge (i.e., lithium ions) that can be stored per unit volume of the anode. This amount is an important factor in determining the overall energy density of the battery (Wh / L) on a volume basis when combined with the cathode and appropriate cell design parameters. The volume specific capacity of the electrode can be estimated as the product of the electrode density (g / cm 3 ), the specific capacity of the active material (mAh / g), and the proportion of the active material in the electrode. LTO anodes usually have a relatively small specific capacity (about 165 mAh / g, compared to about 330 mAh / g for graphite), which, combined with the above-mentioned low electrode density (usually less than 2.0 g / cm 3 ) and a small proportion of the active material (less than 90%), results in a very small volume specific capacity (less than 300 mAh / cm 3 ), and thus a small battery energy density, and a high cost per kWh in various applications. As a result, LTO batteries / cells are generally limited to niche specific applications despite their long cycle life, fast charging performance, and high safety.

[0009] Titanium niobium oxide has been proposed for use as an active electrode material. US2012 / 0052401A1 discloses an oxide of the general formula Li x M 1-y Nb y Nb2O7, where 0 ≦ x ≦ 3, 0 ≦ y ≦ 1, and M represents Ti or Zr. US2015 / 0086872A1 discloses an oxide based on TiNb2O7 having a specific form of carbon coating. US2019 / 0296343A1 and US2014 / 0120404A1 disclose a mixture of a TiNb2O7 phase and a Ti2Nb 10 O 29 , Nb 14 TiO 37 , TiNb 24 O 64 , and / or a TiO2 phase. US2021 / 0376307A1 discloses an Nb-Ti oxide in which the molar ratio of Nb to Ti is >2 and which contains 100 - 2,000 ppm of K, Fe, and / or P. EP3667805A1 discloses a Ti-containing oxide having a coating layer containing Zn, In, Sn, Pb, Hg, Cu, Cd, Ag, and / or Bi. US2015 / 0125753A1 discloses an Nb composite oxide having a P compound on its surface.

[0010] However, there is still a need to identify further active electrode materials with good properties, especially for use in Li-ion cells for high-power / rapid charging applications. For example, identifying these materials that do not require large-scale particle-level engineering and / or coating is an important step towards low-cost battery materials for mass-market adoption. SUMMARY OF THE INVENTION

[0011] In a first aspect, the present invention provides a mixed-phase oxide for use as an active electrode material, the mixed-phase oxide contains Nb and Ti, and further contains M(III) and / or M(II), M(III) is selected from Cr, Al, Ga, and mixtures thereof, M(II) is selected from Zn, Cu, Mg, and mixtures thereof, the mixed-phase oxide comprises an interpenetrating mixture of a first phase and a second phase, the first phase has a crystal structure of TiNb2O7, and the second phase has a crystal structure of Zn2Nb 34 O 87 .

[0012] The inventors have discovered that the mixed-phase oxide according to the first aspect has excellent properties for use in high-power batteries designed for fast charge / discharge, such as maintaining high capacity at high rates of, for example, 5C and 10C, as shown by the present examples.

[0013] In a second aspect, the present invention provides an electrode comprising the mixed-phase oxide of the first aspect as an active electrode material.

[0014] In a third aspect, the present invention provides a metal-ion battery comprising the electrode of the second aspect. Optionally, the metal-ion battery is a lithium-ion battery or a sodium-ion battery, preferably a lithium-ion battery. Preferably, the electrode forms the anode of the metal-ion battery.

[0015] In a fourth aspect, the present invention provides the use of the mixed-phase oxide defined in the first aspect in a metal-ion battery, optionally as an active electrode material at the anode. Optionally, the metal-ion battery is a lithium-ion battery or a sodium-ion battery, preferably a lithium-ion battery.

[0016] In a fifth aspect, the present invention provides a method for manufacturing an electrode, comprising obtaining the mixed-phase oxide defined in the first aspect and depositing the mixed-phase oxide on a current collector, thereby forming an electrode. BRIEF DESCRIPTION OF THE DRAWINGS

[0017]

Figure 1

[0018] The mixed-phase oxide contains Nb, Ti, M(III), and M(II). Oxides containing Nb and at least one other cation can enable safe and long-life operation because the high redox voltage for lithium can exceed 0.8 V, and are essential for rapid charging of battery cells. Furthermore, Nb cations can undergo two redox reactions per atom, resulting in a higher theoretical capacity than, for example, LTO.

[0019] The mixed-phase oxide contains an interpenetrating mixture of a first phase and a second phase. The interpenetrating mixture is one that cannot separate the first and second phases without destroying the mixed-phase oxide.

[0020] The first phase has the crystal structure of TiNb2O7, and the second phase has the crystal structure of Zn2Nb 34 O 87 . The interpenetrating mixture of these phases, in combination with the presence of M(III) and / or M(II), simultaneously modifies each of the two "base" oxides that define the crystal structure (i.e., TiNb2O7 and pure Zn2Nb 34 O 87 ) by substituting elements. For example, it is believed that the first phase contains M(III) and / or M(II) in addition to Ti and Nb, and the second phase contains M(III) and / or Ti in addition to M(II) and Nb. The inventors have found that this simultaneous substitution approach, when combined with the two-phase interpenetrating mixture, improves the properties of each of the "base" oxides, providing synergistic advantages compared to comparing the first and second phases separately. For example, the mixed-phase oxide of the present invention provides surprisingly improved performance at high rates of 5C or more. Furthermore, adding M(II) cations and / or M(III) cations increases the entropy of the system and promotes the formation of the desired crystal structure.

[0021] The first phase has the crystal structure of TiNb2O7, which is derived from MO of the class known as the Wadsley-Roth crystal structure and is related to ReO3 3-xIt can be regarded as having a 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 there is a simplified formula for MO 3-x . As a result, these structures usually contain octahedral subunits of [MO6] in the crystal structure. The phases having these structures are considered to have advantageous properties for use as active electrode materials in, for example, lithium-ion batteries.

[0022] The open tunnel-like MO3 crystal structure provides an ideal candidate for high-capacity Li-ion storage and a high ratio of intercalation / deintercalation. The crystallographic off-stoichiometry present in the crystal structure causes the Wadsley-Roth crystallographic superstructure. These superstructures are combined by other properties such as the Jahn-Teller effect and becoming more crystallographically disordered by utilizing multiple mixed cations, stabilizing the crystal, opening tunnels during intercalation to maintain stability, and enabling a very high rate capability due to a high lithium diffusion rate (reported to be about 10 -13 cm 2 s -1 ).

[0023] The crystal structure of TiNb2O7 can be described as having a 3x3x∞ crystallographic block structure composed of [MO6] octahedrons, where M is Ti or Nb in the formula. The crystal structure is generally monoclinic. The crystal structure of TiNb2O7 can be found in PDF card 00-039-1407. The unit cell parameters a, b, and c can be such that a is 17.66 - 17.74 Å, preferably 17.68 - 17.72 Å, b is 3.77 - 3.84 Å, preferably 3.79 - 3.82 Å, and c is 11.86 - 11.94 Å, preferably 11.88 - 11.92 Å. The crystal structure of the first phase has unit cell parameters α and γ, each being about 90°, preferably α = γ = 90°, and β can be 95.30 - 95.37°, preferably 95.32 - 95.36°.

[0024] While not wishing to be bound by theory, the inventors believe that adding a larger cation, such as Zn, to the Wadsley-Roth crystal structure can change the lattice parameters of the structure, thereby allowing for better diffusion of lithium ions. Furthermore, doping with such non-redox active cations can avoid the tilting of octahedra during charging and discharging and impart structural stability. 2+ The second phase has the crystal structure of Zn2Nb

[0025] O 34 which can also be regarded as having a MO 87 Wadsley-Roth crystal structure derived from ReO3. The crystal structure of Zn2Nb 3-x O 34 can be described as having a 3x4x∞ crystallographic block structure composed of [MO6] octahedra, where M is Zn or Nb. In the absence of M(II), the crystal structure Zn2Nb 87 O 34 is realized with M(III) or Ti adopting the Zn site. The large block size is advantageous for fast lithium insertion and removal compared to other Wadsley-Roth structures with smaller octahedral block sizes and may be more stable than those with larger octahedral block sizes. The Zn octahedra may be randomly distributed within the structure or may prefer specific locations such as the edges or corners of the blocks. This is equal to 2 / 3 of one Zn cation per block. 87 The crystal structure of the second phase can be monoclinic or orthorhombic, or can be regarded as a mixture of monoclinic and orthorhombic. The crystal structure of monoclinic Zn2Nb

[0026] O 34 can be found in the ICDD crystallographic database entry PDF card 00-013-0317. The crystal structure of orthorhombic Zn2Nb 87 O 34 can be found in PDF card 04-021-7859. 87 The inventors believe that adding a larger cation, such as Zn, to the Wadsley-Roth crystal structure can change the lattice parameters of the structure, thereby allowing for better diffusion of lithium ions. Furthermore, doping with such non-redox active cations can avoid the tilting of octahedra during charging and discharging and impart structural stability.

[0027] When refined to a monoclinic structure, the unit cell parameters a, b, and c can be such that a is from 15.52 to 15.58 Å, preferably from 15.53 to 15.57 Å, b is from 3.79 to 3.84 Å, preferably from 3.80 to 3.83 Å, c is from 20.53 to 20.66 Å, preferably from 20.54 to 20.65 Å, the unit cell parameters α and γ are each about 90°, preferably α = γ = 90°, and β can be from 113.00 to 113.75°, preferably from 113.06 to 113.69°.

[0028] As is widely known, the crystal structure of a phase can be determined by analysis of the X-ray diffraction (XRD) pattern obtained using Cu K-α radiation. For example, the XRD pattern obtained from a particular substance can be compared with known XRD patterns, and the crystal structure can be confirmed via a public database such as the ICDD crystallography database. Rietveld analysis and Pawley analysis can also be used to determine the crystal structure of a substance, particularly the unit cell parameters. Thus, the crystal structures of the first and second phases can be determined by XRD.

[0029] The XRD pattern of the mixed-phase oxide preferably shows a peak A attributable to the first phase at 2θ = 26.0 ± 0.1°. The XRD pattern of the mixed-phase oxide preferably shows a peak B attributable to the second phase at 2θ = 24.9 ± 0.1°. The intensity I A of peak B relative to the intensity I B of peak A can be such that 0 < I B / I A ≤ 0.4, or 0.01 ≤ I B / I A ≤ 0.25, or preferably 0.05 ≤ I B / I A ≤ 0.22. In certain examples, the ratio is 0.07 ≤ I B / I A ≤ 0.16. The peak intensity ratio can be readily calculated using the normalized heights of peaks A and B.

[0030] The weight ratio of the first phase to the second phase can be 199:1 to 1:1, or 99:1 to 3:1, or 50:1 to 8:1. The weight ratio of the phases in the mixed-phase oxide can be determined by refining the XRD pattern of the mixed-phase oxide. The target weight ratio can be obtained by controlling the relative amounts of elemental precursors used in the synthesis.

[0031] Other phases may be present in the mixed-phase oxide. For example, the first phase and the second phase can form at least 80 wt%, at least 90 wt%, or at least 95 wt% of the mixed-phase oxide. The first phase and the second phase can form substantially all of the mixed-phase oxide with, for example, less than 1 wt% of other phases. Preferably, the first phase forms at least 85 wt%, or at least 90 wt%, or at least 92 wt% of the mixed-phase oxide.

[0032] Nb is preferably the major cation present in the mixed-phase oxide. For example, the mixed-phase oxide can contain 66 - 80 at%, or 66.5 - 75 at%, or 66.9 - 69.9 at% of Nb based on all the cations.

[0033] The mixed-phase oxide can contain 33 - 17 at%, or 33.1 - 24 at%, or 33.2 - 30 at% of Ti based on all the cations.

[0034] The mixed-phase oxide can contain >0 - 1 at%, or 0.01 - 0.4 at%, or 0.01 - 0.2 at% of M(III) based on all the cations.

[0035] The mixed-phase oxide can contain >0 - 2 at%, or 0.01 - 1 at%, or 0.02 - 0.5 at% of M(II) based on all the cations.

[0036] The combined amount of M(III) and M(II) may be ≧0.05 at%, ≧0.5 at%, or ≧0.6 at% compared to the amount of Nb.

[0037] The atomic ratio of Ti:Nb may be at least 0.3:1, or at least 0.4:1, or may be from 0.42:1 to 0.5:1.

[0038] It will be appreciated that the amounts of Nb, Ti, M(III), and / or M(II) can be combined to further define the mixed-phase oxide.

[0039] M(III) generally represents a cation having a 3+ oxidation state in the oxide. M(III) is selected from Cr, Al, Ga, and mixtures thereof, or from Cr, Al, and mixtures thereof. Preferably, M(III) is Cr.

[0040] M(II) generally represents a cation having a 2+ oxidation state in the oxide. M(II) is selected from Zn, Cu, Mg, and mixtures thereof, or from Zn, Cu, and mixtures thereof. Preferably, M(II) is Zn.

[0041] Preferably, the mixed-phase oxide contains M(III), particularly when M(III) is Cr and M(II) is Zn, and most preferably contains M(III) and M(II).

[0042] The mixed-phase oxide may optionally further contain at least one additional element. Optionally, the additional element is selected from Zr, Hf, V, Fe, Ta, Mo, W, Mn, Co, Ni, Cd, B, Si, Sn, P, and mixtures thereof, or from Zr, V, Fe, Mo, W, Mn, Co, Ni, Cd, B, Si, P, and mixtures thereof, or preferably from Zr, V, Fe, Mo, W, Cu, P, and mixtures thereof. The at least one additional element may be present in an amount of 1.5 at% or less, or from 0.01 to 1.0 at% based on all the cations. The at least one additional element may be present in a total amount of ≤5 at%, or ≤1 at%, or from 0.01 to 0.5 at% based on the amount of Nb.

[0043] When M(III) and / or M(II) are limited to preferred elements, any optional additional elements may include alternative M(III) and / or M(II) elements. For example, when M(III) is Cr and M(II) is Zn, at least one additional element may further be selected from Al, Ga, Cu, Mg, and mixtures thereof.

[0044] Alternatively, the cations of the mixed-phase oxide can consist of, or can consist of Nb, Ti, M(III), and / or M(II).

[0045] The mixed-phase oxide can further contain Li and / or Na, which can be reversibly inserted in situ when the oxide functions as an active electrode material in a metal-ion battery.

[0046] Advantageously, it has been found that the mixed-phase oxide can be formed by a simple solid-phase synthesis method, as shown by this example. Furthermore, the improved properties obtained by the interpenetrating mixture of the first phase and the second phase are obtained without the need for particle-level engineering, for example, without the need to form a core / shell structure which can usually require complex synthesis. Thus, preferably, the interpenetrating mixture of the first phase and the second phase does not form a core / shell structure. For example, the interpenetrating mixture of the first phase and the second phase does not form a structure in which the first phase forms a shell portion and the second phase forms a core portion surrounded by the shell portion.

[0047] The mixed-phase oxide is preferably granular. The mixed-phase oxide can have a particle size D in the range 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 facilitate processing and manufacturing into electrodes. Furthermore, these particle sizes eliminate the need to use complex and / or expensive methods to yield nano-sized particles. Nano-sized particles (e.g., D of 100 nm or less) 50Particles having a particle size) are usually more complex to synthesize and further require consideration of safety.

[0048] The mixed-phase oxide may have 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 By maintaining the particle size of D within these ranges, the possibility of parasitic reactions in the Li-ion cell due to a decrease in surface area is reduced, and processing becomes easier with less binder for the electrode slurry. 10 By maintaining the particle size of D within these ranges, the proportion of the particle size distribution at a large particle size is minimized, and it becomes easier to manufacture the material into a homogeneous electrode.

[0049] The mixed-phase oxide may have a D of 200 μm or less, 100 μm or less, 50 μm or less, or 20 μm or less. 90 By maintaining the particle size of D within these ranges, the proportion of the particle size distribution at a large particle size is minimized, and it becomes easier to manufacture the material into a homogeneous electrode. 90 The term "particle size" refers to the diameter of an equivalent sphere (esd), i.e., the diameter of a sphere having the same volume as a given particle, and the volume of the particle is understood to include the volume of any internal pores within the particle. "D

[0050] The term "particle size" refers to the diameter below which n volume % of the particle population is found. That is, the terms "D n " and "the particle size of D n " refer to the volume-based median particle size below which 50 volume % of the particle population is found. If the material contains primary microcrystals aggregated into secondary particles, it will be understood that the particle size refers to the diameter of the secondary particles. The particle size can be determined by laser diffraction. The particle size is measurable in accordance with ISO13320:2009 and, for example, uses the Mie theory. 50 " and "the particle size of D 50 The mixed-phase oxide is 0.1 - 100 m

[0051] / g, or 0.25 - 50 m 2 / g, or 0.5 - 20 m 2 / g, or 0.5 - 20 m 2It can have a BET surface area in the range of / g. Generally, a low BET surface area is preferred, for example, to minimize the formation of the solid electrolyte interphase (SEI) layer during the first charge-discharge cycle of an electrode containing the substance, in order to minimize the reaction between the mixed-phase oxide and the electrolyte. However, if the BET surface area is too small, most of the mixed-phase oxide cannot approach the metal ions in the surrounding electrolyte, resulting in an unacceptable low charge rate and capacity.

[0052] The term "BET surface area" refers to the surface area per unit mass calculated from the measurement of the physical adsorption of gas molecules on a solid surface using the Brunauer-Emmett-Teller theory. For example, the BET surface area can be determined in accordance with ISO9277:2010.

[0053] The mixed-phase oxide can have a crystallite size greater than 180 nm, or greater than 200 nm, or greater than 225 nm, or preferably greater than 250 nm. The crystallite size may be in the range of 180 nm to 20 μm, or 200 nm to 10 μm, or 225 nm to 5 μm, or 250 nm to 3 μm. In these ranges of crystallite sizes, there are fewer grain boundaries in the material, and thus less interfacial resistance, so it is considered that ion transport is improved compared to materials with smaller crystallites. Higher density particles and higher density electrodes can also be manufactured with larger crystallite sizes. The crystallite size can be conveniently measured by the Scherrer method using crushed Si crystals as a standard.

[0054] In the powder X-ray diffraction pattern, the shape of the diffraction peak is determined by the convolution of the line profile (instrument contribution) generated by the optical system of the diffractometer and that generated by the sample (sample-dependent peak broadening). The finite-sized diffraction crystallites in the sample contribute to the width of the diffraction peak. The instrument contribution can be considered, and then the volume-weighted average crystallite size can be determined using the diffraction peak width by using the Scherrer equation. The Scherrer equation correlates the width of the diffraction peak at a given Bragg angle with the minimum crystallite diameter.

Number

[0055] Preferably, the volume-weighted average crystallite size of the sample is determined using the Scherrer method, and the contribution of the instrument can be determined from the measurement of the standard sample. The standard sample should be a crystalline substance with a large crystallite size, for example, an average crystallite size > 1 μm, and ideally should have a Bragg peak at the same angle as the peak selected for the analysis of the test sample. LaB6 (e.g., NIST SRM 660C) or crushed Si crystals (e.g., NIST SRM 640C) are often used. The sample peak selected for analysis should be a single Bragg reflection and preferably the peak with the highest scattering intensity. The full width at half maximum of the peak is measured by finding the point of the diffraction peak where the scattering intensity is intermediate between the background intensity and the maximum intensity of the peak and measuring the difference in the values of the 2θ Bragg angle of the peak at these scattering intensity values.

[0056] Preferably, the standard sample and the test sample should be measured using the same instrument under the same conditions. The scan speed and step size of the diffraction measurement should be such that the peak intended for investigation includes the measured values of at least 8 data points exceeding the half-maximum point, and the maximum intensity point of the peak should have at least 10 times the intensity of the background.

[0057] Transmission electron microscopy (TEM) examination can be further used to confirm the crystallite size determined by the Scherrer method. The diameter D measured by the particle size distribution 50Particles of an overall size close to are examined by selected area electron diffraction (SAED) to investigate the degree of crystalline domains within the particles. When the zone axis is aligned and a clear diffraction pattern is obtained, a spatial map can be created by measuring the diffraction pattern at spatial intervals until a grain boundary is encountered.

[0058] The mixed-phase oxide can be coated with carbon to, for example, improve the electrical conductivity of the surface and / or prevent reaction with the electrolyte.

[0059] The mixed-phase oxide may have a protective coating, and optionally, the protective coating includes niobium oxide, aluminum oxide, zirconium oxide, organic or inorganic fluorides, organic or inorganic phosphates, titanium oxide, lithiated versions thereof, and mixtures thereof.

[0060] The electrode of the second aspect is typically in the form of an electrode composition that is in electrical contact with a current collector, wherein the electrode composition includes a mixed-phase oxide. The current collector is usually a metal foil such as copper foil or aluminum foil.

[0061] Optionally, the mixed-phase oxide forms at least 25 wt%, 50 wt%, or 75 wt% of the total active electrode material of the electrode. The mixed-phase oxide can form the sole active electrode material of the electrode.

[0062] The electrode composition may further include at least one other component selected from a binder, a conductive additive, different active electrode materials (e.g., additional mixed-phase oxides as defined herein), and mixtures thereof. For example, one electrode composition includes about 92 wt% of a mixed-phase oxide, about 5 wt% of a conductive additive (e.g., carbon black), and about 3 wt% of a binder (e.g., poly(vinylidene fluoride)) based on the total dry weight of the electrode composition.

[0063] Examples of suitable binders include polyvinylidene fluoride and its copolymers (PVDF), polytetrafluoroethylene (PTFE) and its copolymers, polyacrylonitrile (PAN), poly(methyl)methacrylate or poly(butyl)methacrylate, polyvinyl chloride (PVC), polyvinyl formal, polyether amide, polymethacrylic acid, polyacrylamide, polyitaconic 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), alginates and their alkali metal salts, butadiene acrylonitrile rubber (NBR), the hydrogenated form of NBR (HNBR), styrene butadiene rubber (SBR), and polyimide. The binder can be present in the electrode composition in an amount of 0 to 30 wt%, or 0.1 to 10 wt%, or 0.1 to 5 wt% based on the total dry weight of the electrode composition.

[0064] The conductive additive is preferably a non-active material included to improve the electrical conductivity between the active electrode materials and between the active electrode material and the current collector. The conductive additive can be appropriately selected from graphite, carbon black, carbon fiber, vapor-grown carbon fiber (VGCF), carbon nanotube, graphene, acetylene black, ketjen black, metal fiber, metal powder, and conductive metal oxide. Preferred conductive additives include carbon black and carbon nanotubes. The conductive additive can be present in the electrode composition in an amount of 0 to 20 wt%, 0.1 to 10 wt%, or 0.1 to 5 wt% based on the total dry weight of the electrode composition.

[0065] The mixed-phase oxide can be present in the electrode composition in an amount of 100 to 50 wt%, 99.8 to 80 wt%, or 99.8 to 90 wt% based on the total dry weight of the electrode composition. When the active electrode material is present at 100 wt% of the electrode composition, it can be used as a solid electrode.

[0066] When different active electrode materials are present in addition to the mixed-phase oxide, they can be selected from lithium titanate, titanium niobate, different mixed-phase oxides, graphite, hard carbon, soft carbon, silicon, their doped versions, and mixtures thereof.

[0067] The mixed-phase oxide can form an active electrode material in combination with lithium titanate.

[0068] Lithium titanate preferably has a spinel or ramsdellite crystal structure, as determined, for example, by X-ray diffraction. Examples of lithium titanate having a spinel crystal structure are Li4Ti5O 12 . Examples of lithium titanate having a ramsdellite crystal structure are Li2Ti3O7. These materials have been shown to have excellent properties for use as active electrode materials. Therefore, lithium titanate can have a crystal structure determined by X-ray diffraction corresponding to Li4Ti5O 12 and / or Li2Ti3O7. Lithium titanate can be selected from Li4Ti5O 12 , Li2Ti3O7, and mixtures thereof. Lithium titanate may be doped with additional cations or anions. Lithium titanate can be oxygen-deficient. Lithium titanate can include a coating, and optionally, the coating is selected from carbon, polymer, metal, metal oxide, semimetal, phosphate, and fluoride. Lithium titanate can be synthesized by conventional ceramic techniques, such as solid-phase synthesis or sol-gel synthesis. Alternatively, lithium titanate can be obtained from commercial suppliers.

[0069] Lithium titanate is preferably granular. Lithium titanate has a D in the range of 0.1 to 50 μm, or 0.25 to 20 μm, or 0.5 to 15 μm 50may have a particle size. Lithium titanate may have a D of at least 0.01 μm, or at least 0.1 μm, or at least 0.5 μm 10 may have a particle size. Lithium titanate may have a D of 100 μm or less, 50 μm or less, or 25 μm or less 90 may have a particle size. D 90 By maintaining the particle size within this range, the packing of lithium titanate particles in a mixture with mixed-phase oxide particles is improved.

[0070] Lithium titanate is usually used for the anode of a battery with a small particle size because the electronic conductivity of the material is low. In contrast, the mixed-phase oxide defined herein typically has a higher lithium-ion diffusion coefficient than lithium titanate and can therefore be used with a larger particle size. Advantageously, in the composition, lithium titanate may have a smaller particle size than the mixed-phase oxide. For example, the ratio of the D 50 particle size of lithium titanate to the D 50 particle size of the mixed-phase oxide is in the range of 0.01:1 to 0.9:1, or 0.1:1 to 0.7:1. In this way, the smaller lithium titanate particles can be accommodated in the voids between the larger mixed-phase oxide particles, increasing the packing efficiency of the composition.

[0071] Lithium titanate may have a BET surface area in the range of 0.1 to 100 m 2 / g, or 1 to 50 m 2 / g, or 3 to 30 m 2 / g.

[0072] The mass ratio of lithium titanate to the mixed-phase oxide may 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 contains a higher ratio of lithium titanate than the mixed-phase oxide, for example, at a mass ratio of at least 2:1, at least 5:1, or at least 8:1. Advantageously, this allows the gradual introduction of the mixed-phase oxide into existing electrodes based on lithium titanate without significantly changing the manufacturing technology, resulting in an efficient way to improve the properties of the existing electrodes. In another embodiment, the active electrode material has a higher proportion of the mixed-phase oxide than lithium titanate, for example, the mass ratio of lithium titanate to the mixed-phase oxide is less than 1:2, or less than 1:5, or less than 1:8. Advantageously, this makes it possible to reduce the cost of the active electrode material by replacing part of the mixed-phase oxide with lithium titanate.

[0073] The mixed-phase oxide can form an active electrode material in combination with niobium oxide. The niobium oxide is Nb 12 O 29 , NbO2, NbO and Nb2O5. Preferably, the niobium oxide is Nb2O5.

[0074] The niobium oxide can be doped with additional cations or anions, for example, on the condition that the crystal structure of the niobium oxide corresponds to the crystal structures of oxides composed of Nb and O, such as Nb 12 O 29 , NbO2, NbO, and Nb2O5. The niobium oxide can be oxygen-deficient. The niobium oxide may include a coating, and optionally, the coating is selected from carbon, polymer, metal, metal oxide, semimetal, phosphate, and fluoride.

[0075] The niobium oxide is Nb 12 O 29It can have the crystal structure of NbO2, NbO, or Nb2O5. For example, the niobium oxide can have the crystal structure of orthorhombic Nb2O5 or monoclinic Nb2O5. Preferably, the niobium oxide has the crystal structure of monoclinic Nb2O5, and most preferably has the crystal structure of H-Nb2O5. Further information regarding the crystal structure of Nb2O5 can be found in Griffith et al., J. Am. Chem. Soc. 2016, 138, 28, 8888-8899. The niobium oxide can be synthesized by conventional ceramic techniques such as solid-phase synthesis or sol-gel synthesis. Alternatively, the niobium oxide can be obtained from commercial suppliers.

[0076] The niobium oxide is preferably granular. The niobium oxide can have a D 50 particle size in the range of 0.1 to 100 μm, or 0.5 to 50 μm, or 1 to 20 μm. The niobium oxide can have a D 10 particle size of at least 0.05 μm, or at least 0.5 μm, or at least 1 μm. The niobium oxide can have a D 90 particle size of 100 μm or less, 50 μm or less, or 25 μm or less. By maintaining the D 90 particle size within this range, the packing of niobium oxide particles in the mixture with the mixed-phase oxide particles is improved.

[0077] The niobium oxide can have a BET surface area in the range of 0.1 to 100 m 2 / g, or 1 to 50 m 2 / g, or 1 to 20 m 2 / g.

[0078] The mass ratio of the niobium oxide to the mixed-phase oxide may be in the range of 0.5:99.5 to 99.5:0.5, or 2:98 to 98:2, or preferably in the range of 15:85 to 35:55.

[0079] The present invention also provides for the use of the mixed-phase oxide as defined herein in the anode of a metal-ion battery, optionally, the metal-ion battery being a lithium-ion battery or a 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-based batteries.

[0080] 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, the anode comprising the mixed-phase oxide according to the first aspect of the present invention, optionally, the electrochemical device being 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 greater than 230 mAh / g at 23 mA / g, and while retaining more than 70% of the initial cell capacity at 23 mA / g, the battery can be charged and discharged at a current density with respect to the anode active material of 200 mA / g or more, or 1000 mA / g or more, or 2000 mA / g or more, or 4000 mA / g or more. By using the active electrode material of the first aspect of the present invention, it may be possible to manufacture a lithium-ion battery having this combination of characteristics, representing a lithium-ion battery particularly suitable for use in applications where high charge and discharge current densities are desired. In particular, the examples have shown that the active electrode material according to the first aspect of the present invention has excellent capacity at high C-rates.

[0081] The mixed-phase oxide can be synthesized by conventional ceramic techniques. For example, it may be produced by one or more of solid-state synthesis or sol-gel synthesis, and preferably can be produced by solid-state synthesis using particulate precursors as shown by the examples. The mixed-phase oxide can be further synthesized by one or more of the commonly used alternative techniques such as hydrothermal synthesis or microwave hydrothermal synthesis, solvothermal synthesis 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.

[0082] The mixed-phase oxide can be obtained by a method comprising the steps of obtaining one or more precursor substances, mixing the precursor substances to form a precursor substance mixture, and heat-treating the precursor substance mixture in a temperature range of 800 °C to 1350 °C or 1000 °C to 1300 °C to thereby obtain the mixed-phase oxide.

[0083] The mixed-phase oxide is modified to contain at least one electronegative element, and oxygen anions can be partially replaced with alternative anions selected from F, Cl, Br, I, N, S, Se, and mixtures thereof, or F, Cl, N, S, and mixtures thereof, or preferably F, N, and mixtures thereof. The at least one electronegative element can be present in a total amount of ≤5 at% or ≤1 at% relative to the amount of O. The electronegative element can be introduced by mixing the mixed-phase oxide with a precursor containing the electronegative element to obtain a further precursor material mixture, and heat-treating the further precursor material mixture in a temperature range of 300 - 1200 °C or 800 - 1100 °C, optionally under reducing conditions, to thereby obtain a mixed-phase oxide containing the further electronegative element.

[0084] For example, to obtain a mixed-phase oxide containing N, the method may further include mixing the mixed-phase oxide with a precursor containing N (such as melamine or urea) to obtain a further precursor substance mixture, and heat-treating the further precursor substance mixture in a temperature range of 300 to 1200 °C under reducing conditions (such as under N2), thereby obtaining a mixed-phase oxide containing N.

[0085] For example, to obtain a mixed-phase oxide containing F, the method may further include mixing the mixed-phase oxide with a precursor containing F (such as polyvinylidene fluoride or NH4F) to obtain a further precursor substance mixture, and heat-treating the further precursor substance mixture in a temperature range of 300 to 1200 °C under oxidizing conditions (such as in air), thereby obtaining a mixed-phase oxide containing F.

[0086] The method may further include a further step of heat-treating the mixed-phase oxide in a temperature range of 400 to 1350 °C or 800 to 1250 °C under reducing conditions, thereby inducing oxygen vacancies in the mixed-phase oxide.

[0087] Precursor substances for making mixed-phase oxides can include one or more metal oxides, metal hydroxides, metal salts or ammonium salts. For example, the precursor substance can include one or more metal oxides or metal salts with different oxidation states and / or different crystal structures. Examples of suitable precursor substances include, but are not limited to, Nb2O5, Nb(OH)5, niobic acid, NbO2, ammonium niobate oxalate, 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, Cr2O3, MnO, MnO2, NiO, Ni2O3, H3BO3, ZnO, Li2CO3, Na2CO3, H3BO3, NiO, Mg5(CO3)4(OH)2·5H2O, and MgO. The precursor substance may not contain a metal oxide, or may contain an ion source other than an oxide. For example, the precursor substance can include a metal salt (e.g., NO3 - , SO3 - ) or other compounds (e.g., oxalates, carbonates). When substituting the anions of oxygen with other electronegative anions, the precursor can 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.

[0088] Some or all of the precursor substances may be particulate materials. When they are particulate materials, preferably, they have a diameter of less than 20 μm, for example, a D of 250 nm to 20 μm 50has a particle size. Obtaining such particulate matter with such a particle size helps to promote closer mixing of the precursor substances, thereby enabling a more efficient solid-state reaction during the heat treatment step. However, since the particle size of one or more of the precursor substances can be mechanically reduced during the step of mixing the precursor substances to form the precursor substance mixture, it is not essential for the precursor substances to have an initial particle size of less than 20 μm.

[0089] The step of mixing the precursor substances to form a precursor substance mixture and / or a further precursor substance mixture can be carried out by a process selected from dry or wet / planetary solvation ball milling, rolling ball milling, high-energy ball milling, bead milling, pin milling, classification steps, high-shear milling, air jet milling, steam jet milling, planetary mixing, high-shear mixing, impact mixing, powder mixing, and / or impact milling. The force used for mixing / milling can depend on the form of the precursor substances. For example, if part or all of the precursor substances have a larger particle size (e.g., a particle size exceeding 20 μm), the milling force can be selected to reduce the particle size of the precursor substances such that the particle size of the precursor substance mixture is reduced to a diameter of 20 μm or less. When the particle size of the particles of the precursor mixture is 20 μm or less, the solid-state reaction of the precursor substances in the precursor substance mixture can be promoted more efficiently during the heat treatment step. Solid-phase synthesis can also be carried out with pellets formed from the precursor powder at high pressure (above 10 MPa). 50 The step of heat-treating the precursor substance mixture and / or a further precursor substance mixture can be carried out for a time of 1 hour to 24 hours, more preferably 3 hours to 18 hours. For example, the heat treatment 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 treatment step can be carried out for 24 hours or less, 18 hours or less, 16 hours or less, or 12 hours or less.

[0090] The step of heat-treating the precursor substance mixture and / or a further precursor substance mixture can be carried out for a time of 1 hour to 24 hours, more preferably 3 hours to 18 hours. For example, the heat treatment 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 treatment step can be carried out for 24 hours or less, 18 hours or less, 16 hours or less, or 12 hours or less.

[0091] The step of heat-treating the precursor mixture can be carried out in a gaseous atmosphere, preferably in air. Suitable gaseous atmospheres include air, N2, Ar, He, CO2, CO, O2, H2, NH3, and mixtures thereof. The gaseous atmosphere may be a reducing atmosphere. When it is desired to produce an oxygen-deficient material, preferably, the step of heat-treating the precursor mixture is carried out in an inert atmosphere or a reducing atmosphere.

[0092] The further step of heat-treating the precursor mixture can be carried out under reducing conditions. Reducing conditions include under an inert gas such as nitrogen, helium, argon, or under a mixture of an inert gas and hydrogen, or under vacuum. Preferably, the further step of heat-treating the precursor mixture includes heating under an inert gas.

[0093] The further optional step of heat-treating the mixed-phase oxide and / or the mixed-phase oxide containing additional electronegative anions under reducing conditions can be carried out over a time period of 0.5 hours to 24 hours, more preferably 2 hours 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, 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.

[0094] In some methods, it may be beneficial to perform a two-step heat treatment. For example, the precursor mixture and / or the further precursor 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. By performing such a two-step heat treatment, the solid-state reaction can be assisted to form the desired crystal structure. This can be carried out continuously or in an intermediate regrinding step.

[0095] This method can include one or more post-treatment steps after the formation of the mixed-phase oxide. In some cases, this method can include a post-treatment step of heat-treating the mixed-phase oxide, which may also be referred to as "annealing". This post-treatment heat-treatment step can be carried out in a gas atmosphere different from the step of heat-treating the precursor substance mixture to form the mixed-phase 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 carried out at a temperature exceeding 500 °C, for example, about 900 °C. Including the post-treatment heat-treatment step can be beneficial, for example, to form deficiencies or defects in the mixed-phase oxide, such as inducing oxygen deficiency, or to perform anion exchange, such as N exchange of O anions, in the formed mixed-phase oxide.

[0096] This method can include the step of milling and / or classifying the mixed-phase oxide (e.g., impact milling, jet milling, steam jet milling, high-energy milling, ball milling, high-shear milling, pin milling, air classification, wheel classification, sieving, cyclone separation, bead milling) to obtain a substance having any of the above particle size parameters.

[0097] The present invention provides a method for manufacturing an electrode, which includes obtaining a mixed-phase oxide defined herein and depositing the mixed-phase oxide on a current collector to form an electrode. Obtaining the mixed-phase oxide may include synthesizing the mixed-phase oxide by the method provided herein. The deposition step may include forming a slurry of the mixed-phase oxide and a solvent. The slurry can include at least one other component selected from a binder, a conductive additive, different active electrode materials, and mixtures thereof. By depositing the slurry on the current collector and removing the solvent, an electrode layer can be formed on the current collector. Optionally, further steps such as heat treatment to cure any binder and / or calendaring of the electrode layer can also be performed. For example, the solvent can be removed by drying at a temperature of, for example, 30 to 100 °C. The electrode can be calendared to a density of 2 to 3.5 or 2.6 to 2.9 g / cm -3 ³. The thickness of the electrode layer can range 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, preferably from 5 μm to 50 μm.

[0098] Alternatively, the slurry can be formed into a self-supporting film or mat containing the mixed-phase oxide by, for example, casting the slurry on a suitable casting template, removing the solvent, and then removing the casting template. The resulting film or mat is cohesive and in the form of a self-supporting mass and can then be bonded to the current collector by known methods.

Examples

[0099] The mixed-phase oxide was synthesized by a solid-phase route. In the first step, precursor materials (Nb₂O₅, TiO₂, ZnO, Cr₂O₃, CuO, MgO, Al₂O₃, and Ga₂O₃) were made to have a D of less than 20 μm 50It was milled to a particle size of millimeters. Then, an appropriate amount of precursors was combined and mixed in an impact mill at 20,000 rpm to obtain a homogeneous powder mixture (total 50 g). The obtained powder was heat-treated in an alumina crucible using a muffle furnace at 1100 - 1200 °C for 1 - 24 hours according to the desired Wadsley-Roth phase. Samples 3 - 12 were removed from the furnace, milled in an impact mill at 20,000 rpm, and heated twice using the same conditions. A heating rate of 5 °C / min was used for all heat treatment conditions. Finally, if necessary, a deagglomeration step by milling in an impact mill at 20,000 rpm for at least 2 minutes was utilized to adjust the desired particle size distribution. The particle size distribution was obtained using a laser diffraction particle analyzer for dry powders manufactured by Horiba. The air pressure was maintained at 0.3 MPa. The results are shown in Table 1.

Table 1

[0100] For example, 95TiNb2O7:5Cr 0.6 Zn 1.6 Nb 33.8 O 87 The notation such as means a mixed-phase oxide prepared from precursors weighed to an elemental ratio of a mixture of 95 parts by weight of TiNb2O7 and 5 parts by weight of Cr 0.6 Zn 1.6 Nb 33.8 O 87 The first and second phases of the synthesized mixed-phase oxide contain additional substitution elements compared to the "base" oxide. Specifically, In Samples 3 - 5, the first phase has the crystal structure of TiNb2O7 but further contains Cr and / or Zn, and the second phase has the crystal structure of Zn2Nb 34 O 87 but further contains Cr and / or Ti, In Sample 6, the first phase has the crystal structure of TiNb2O7 but further contains Al and / or Zn, and the second phase has the crystal structure of Zn2Nb 34 O 87 but further contains Al and / or Ti, In Sample 7, the first phase has the crystal structure of TiNb2O7 but further contains Cr, and the second phase has the crystal structure of Zn2Nb 34 O 87 but contains Cr and / or Ti, In Sample 8, the first phase has the crystal structure of TiNb2O7 but further contains Cr and / or Al, and the second phase has the crystal structure of Zn2Nb 34 O 87 but contains Cr, Al, and / or Ti, In Sample 9, the first phase has the crystal structure of TiNb2O7 but further contains Ga and / or Al, and the second phase has the crystal structure of Zn2Nb 34 O 87 but contains Ga, Al, and / or Ti, In Sample 10, the first phase has the crystal structure of TiNb2O7 but further contains Cu and / or Ga, and the second phase has the crystal structure of Zn2Nb 34 O 87 but contains Cu, Ga, and / or Ti, In Sample 11, the first phase has the crystal structure of TiNb2O7 but further contains Zn, and the second phase has the crystal structure of Zn2Nb 34 O 87 but further contains Ti, In Sample 12, the first phase has the crystal structure of TiNb2O7 but further contains Mg and / or Cr, and the second phase has the crystal structure of Zn2Nb 34 O 87 but contains Mg, Cr, and / or Ti.

Table 2

[0101] The advantages of the synthesis of the examples in this specification are the reference systems TiNb2O7 and 95TiNb2O7:5Ti2Nb 10 O 29They are shown for

[0102] . These data were collected from a Rigaku SmartLab SE powder X-ray diffractometer using a variable-temperature heating stage, where the unreacted sample was heated at 6 °C / min and XRD scans were performed every 2 minutes. The results are presented in Table 2. The synthesis of Samples 3 and 5 reached completion at temperatures below 1200 °C, as indicated by the absence of anatase peaks, while the synthesis of Samples 1* and 13* did not reach completion. After heat-treating Samples 1* and 13* at 1200 °C for 12 hours, the synthesis of Sample 13* reached completion, but the synthesis of Sample 1* did not reach completion. This is evidenced by the rutile TiO2(110) peak present in the XRD pattern of Sample 1*. These data indicate that the synthesis efficiency of the samples was improved in the present invention, which promotes more cost-effective production.

[0102] Characterization of Substances The phase purity of the samples was analyzed using a Rigaku Miniflex powder X-ray diffractometer in the 2θ range (10 - 70°) at a scan rate of 1° / min. Figure 1 shows the measured XRD diffraction patterns of Samples 1 - 8. Table 3 presents the crystal structure parameters obtained from the refinement of the XRD patterns of each sample. The first phase with the crystal structure of TiNb2O7 was found to have peaks at the same positions that match ICDD entry 00-039-1407 (space group I12 / m1) (with some shift of up to about 0.2° due to crystal changes). The second phase with the crystal structure of Zn2Nb 34 O 87 was found to have peaks at the same positions that match ICDD database entry 00-013-0317 (space group A12 / m1) (with some shift of up to about 0.2° due to crystal changes). Sample 2 was refined using a combination of the crystal structures of both monoclinic (A12 / m1) and orthorhombic (Amma - PDF card 04-021-7859). The second phase of the mixed-phase oxide was refined using only the monoclinic crystal structure. The peak shifts compared to the reference database entries of the "base" crystal structure are due to substitution elements with different ionic radii (e.g., TiNb2O7 substituted with Cr and / or Zn, and Zn2Nb substituted with Cr and / or Ti34 O 87 ) incorporation. The mass ratio between the first and second phases due to refinement was found to be in good agreement with the ratio predicted based on the amount of the precursor, again reflecting the substitution elements with a small difference as expected.

[0103] Sample 3 was subjected to TEM-EDX analysis. The analysis showed a uniform distribution of cations throughout the observed particles, and no localization of cations in specific domains. This supports the existence of an interpenetrating mixture of the first and second phases and the simultaneous substitution of the "base" phase.

Table 3

Table 4

[0104] Electrochemical property evaluation The charging rate of a Li-ion battery is usually expressed in terms of the "C rate". The 1C charging rate means the charging current at which the cell is fully charged in 1 hour, and 10C charging means that the battery is fully charged in 1 / 10 (6 minutes) of 1 hour. The C rate here is defined from the reversible capacity seen at the anode within the voltage limit applied in the second delithiation cycle, that is, within the voltage limit of 1.1 - 3.0 V for an anode showing a capacity of 1.0 mAh cm -2 of the capacity shown, the 1C rate is 1.0 mA cm -2corresponds to the applied current density. For typical materials described herein, this corresponds to approximately 250 mA / g of active material. For analysis, electrochemical tests were performed in a half coin cell (CR2032 size). In the half coin test, the active material is tested against a Li metal electrode with an electrode to evaluate the basic capabilities 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 a poly(vinylidene fluoride) (PVDF) binder, and mixed into a slurry using a laboratory-scale centrifugal planetary mixer. The non-NMP composition of the slurry was 92 wt% active material, 5 wt% conductive additive, and 3 wt% binder. This slurry was coated onto an Al foil current collector by doctor blade coating to a desired coating amount of 69 - 75 g m -2 up to and dried by heating. Next, the electrode was calendared at 80 °C to a density of 2.6 - 2.9 g cm -3 to achieve a target porosity of 30 - 35%. The electrode was punched to the desired size and combined with a separator (porous PP / PE from Celgard), Li metal, and an electrolyte (1.3 M LiPF6 in EC / DEC) in a steel coin cell case and sealed under pressure. Then, at a low current rate of 25 °C (C / 10), the cycle was performed with two full cycles of lithiation and delithiation between 1.1 - 3.0 V. Then, the current density was increased to test the cell's capabilities. During these tests, the cell was subjected to an asymmetric cycle of slow lithiation (C / 5) at 25 °C and then increasing the rate of delithiation (e.g., 5C, 10C) to obtain the capacity. The data was averaged from 3 - 5 cells prepared from the same electrode coating, and the error is indicated from the standard deviation. Thus, the data represents a conclusive study showing that an improvement was achieved by the material according to the present invention compared to conventional materials. These data are shown in Table 5.

Table 5

[0105] Discussion The interpenetrating mixture of the first and second phases, as well as the simultaneous replacement of the "base" phase, have been found to bring about a surprising improvement in the properties of the mixed-phase oxide compared to either of the single phases. In particular, at high rates of 5C and above, the delithiation specific capacity of Samples 3 - 5 (mixed-phase oxides containing Nb, Ti, Cr, and Zn) is higher than that of both Sample 1*(TiNb2O7) and Sample 2*(Cr 0.6 Zn 1.6 Nb 33.8 O 87 ) and shows a synergistic improvement. Similarly, the delithiation specific capacity at 5C and above for each of Sample 6 (mixed-phase oxide containing Nb, Ti, Al, and Zn), Sample 7 (mixed-phase oxide containing Nb, Ti, and Cr), Sample 8 (mixed-phase oxide containing Nb, Ti, Cr, and Al), Sample 9 (mixed-phase oxide containing Nb, Ti, Ga, and Al), Sample 10 (mixed-phase oxide containing Nb, Ti, Cu, and Ga), Sample 11 (mixed-phase oxide containing Nb, Ti, and Zn), and Sample 12 (mixed-phase oxide containing Nb, Ti, Mg, and Cr) has been found to be higher than that of both Sample 1* and Sample 2*.

[0106] Similar advantages are expected to be shown for the described ranges of elements M(III) and M(II). Specific embodiments of the present invention are as follows. [Aspect 1] A mixed-phase oxide for use as an active electrode material, wherein the mixed-phase oxide contains Nb and Ti, and further contains M(III) and / or M(II), M(III) is selected from Cr, Al, Ga, and mixtures thereof, M(II) is selected from Zn, Cu, Mg, and mixtures thereof, the mixed-phase oxide contains an interpenetrating mixture of a first phase and a second phase, the first phase has a crystal structure of TiNb 2 O 7 , and the second phase has a crystal structure of Zn 2 Nb 34 O 87 , the mixed-phase oxide. [Aspect 2] The mixed-phase oxide according to Aspect 1, wherein the XRD pattern of the mixed-phase oxide shows a peak A attributed to the first phase at 2θ = 26.0 ± 0.1°. [Aspect 3] The mixed-phase oxide according to any of the preceding aspects, wherein the XRD pattern of the mixed-phase oxide shows a peak B attributed to the second phase at 2θ = 24.9 ± 0.1°. [Aspect 4] The ratio of the intensity I of the peak B B to the intensity I of the peak A A is 0 < I B / I A ≤ 0.4, or 0.01 ≤ I B / I A ≤ 0.25, or 0.05 ≤ I B / I A ≤ 0.22, or 0.07 ≤ I B / I A ≤ 0.16, the mixed-phase oxide according to Aspects 2 and 3. [Aspect 5] The mixed-phase oxide according to any of the preceding aspects, wherein the weight ratio of the first phase to the second phase is 199:1 to 1:1, or 99:1 to 3:1, or 50:1 to 8:1. [Aspect 6] The mixed-phase oxide according to any of the preceding aspects, wherein the first phase forms at least 85 wt%, or at least 90 wt%, or at least 92 wt% of the mixed-phase oxide. [Aspect 7] The mixed-phase oxide according to any of the preceding aspects, wherein the first phase and the second phase form at least 80 wt%, at least 90 wt%, or at least 95 wt% of the mixed-phase oxide. [Aspect 8] The mixed-phase oxide according to any of the preceding aspects, containing 66 - 80 at% of Nb and 33 - 17 at% of Ti for all cations, and further containing >0 - 1 at% of M(III) and / or >0 - 2 at% of M(II). [Aspect 9] The mixed-phase oxide according to any of the preceding aspects, wherein the amount of the combination of M(III) and M(II) is ≥ 0.05 at%, or ≥ 0.5 at%, or ≥ 0.6 at% with respect to the amount of Nb. [Aspect 10] The mixed-phase oxide according to any of the preceding aspects, wherein the atomic ratio of Ti:Nb is at least 0.3:1, or at least 0.4:1, or 0.42:1 to 0.5:1. [Aspect 11] The mixed-phase oxide according to any of the preceding aspects, comprising M(III) or comprising M(III) and M(II). [Aspect 12] The mixed-phase oxide according to any of the preceding aspects, wherein M(III) is Cr, Al, and mixtures thereof, and M(II) is Zn. [Aspect 13] The mixed-phase oxide according to any of the preceding aspects, wherein M(III) is Cr, Al, and mixtures thereof, or M(III) is Cr. [Aspect 14] The mixed-phase oxide according to any of the preceding aspects, wherein M(II) is Zn, Cu, and mixtures thereof, or M(II) is Zn. [Aspect 15] The mixed-phase oxide according to any of the preceding aspects, comprising M(III) and M(II), wherein M(III) is Cr and M(II) is Zn. [Aspect 16] The mixed-phase oxide is in particulate form, and optionally, the mixed-phase oxide has a D 50 particle size in the range of 0.1 to 100 μm, or 0.5 to 50 μm, or 1 to 20 μm. The mixed-phase oxide according to any of the preceding aspects. [Aspect 17] The mixed-phase oxide has a BET surface area in the range of 0.1 to 100 m 2 / g, or 0.25 to 50 m 2 / g, or 0.5 to 20 m 2 / g. The mixed-phase oxide according to any of the preceding aspects. [Aspect 18] The mixed-phase oxide according to any of the preceding aspects, having a crystallite size greater than 180 nm, or greater than 200 nm, or greater than 225 nm, or greater than 250 nm. [Aspect 19] Further comprising at least one additional element, and optionally, the additional element is (i) Zr, Hf, V, Fe, Ta, Mo, W, Mn, Co, Ni, Cd, B, Si, Sn, P, and mixtures thereof, or (ii) Zr, V, Fe, Mo, W, Mn, Co, Ni, Cd, B, Si, P, and mixtures thereof, or (iii) Zr, V, Fe, Mo, W, P, and mixtures thereof. The mixed-phase oxide according to any of the preceding aspects. [Aspect 20] The mixed-phase oxide according to Aspect 19, wherein the at least one additional element is present in a total amount of ≤ 5 at%, or ≤ 1 at%, or ≤ 0.5 at% based on the amount of Nb. [Aspect 21] (i) F, Cl, Br, I, N, S, Se, and mixtures thereof, or (ii) F, Cl, N, S, and mixtures thereof, or (ii) a mixed-phase oxide according to any of the preceding aspects, further comprising at least one electronegative element selected from F, N, and mixtures thereof. [Aspect 22] The mixed-phase oxide according to Aspect 21, wherein the at least one electronegative element is present in a total amount of ≦5 at% or ≦1 at% relative to the amount of O. [Aspect 23] The mixed-phase oxide according to any of the preceding aspects, wherein the interpenetrating mixture of the first phase and the second phase does not form a core / shell structure. [Aspect 24] The mixed-phase oxide according to any of the preceding aspects, wherein the mixed-phase oxide is coated with carbon. [Aspect 25] A composition comprising a mixed-phase oxide according to any of Aspects 1 to 24 and at least one other component, optionally, wherein the at least one other component is selected from binders, solvents, conductive additives, different active electrode materials, and mixtures thereof. [Aspect 26] An electrode comprising a mixed-phase oxide according to any of Aspects 1 to 24 as an active electrode material. [Aspect 27] The electrode according to Aspect 26, wherein the mixed-phase oxide forms at least 25 wt%, at least 50 wt%, or at least 75 wt% of the total active electrode material of the electrode, or wherein the mixed-phase oxide is the sole active electrode material of the electrode. [Aspect 28] The electrode according to Aspect 26 or 27, further comprising at least one other component selected from binders, conductive additives, different active electrode materials, and mixtures thereof. [Aspect 29] The electrode according to Aspect 28, wherein the different active electrode material is selected from lithium titanate, titanium niobate, different mixed-phase oxides, graphite, hard carbon, soft carbon, silicon, their doped and / or carbon-coated versions, and mixtures thereof. [Aspect 30] Optionally, a metal-ion battery is a lithium-ion battery, and the electrode forms an anode, a metal-ion battery comprising the electrode according to any of Aspects 26 to 29. [Aspect 31] A lithium-ion battery having a reversible anode active material specific capacity greater than 230 mAh / g at 23 mA / g, while retaining more than 70% of the initial cell capacity at 23 mA / g, the battery being capable of charging and discharging at a current density with respect to the anode active material of 230 mA / g or more, or 1000 mA / g or more, or 2000 mA / g or more, or 4000 mA / g or more, the metal ion battery according to aspect 30. [Aspect 32] Use of a mixed-phase oxide, wherein the mixed-phase oxide is as described in any of aspects 1 to 24 as an active electrode material in a metal ion battery, and optionally in the anode of a lithium-ion battery, said use. [Aspect 33] A method for manufacturing an electrode, obtaining a mixed-phase oxide as described in any of aspects 1 to 24, and depositing the mixed-phase oxide on a current collector to form the electrode, the method comprising.

Claims

1. A mixed-phase oxide for use as an active electrode material, wherein the mixed-phase oxide contains Nb and Ti, and further contains M(III) and / or M(II), M(III) is selected from Cr, Al, Ga, and mixtures thereof, M(II) is selected from Zn, Cu, Mg, and mixtures thereof, wherein the mixed-phase oxide contains an interpenetrating mixture of a first phase and a second phase, The first phase has a crystal structure of TiNb ２ O ７ , and the second phase has a crystal structure of Zn ２ Nb ３４ O ８７ , the mixed-phase oxide having the same.

2. The mixed-phase oxide according to claim 1, wherein the XRD pattern of the mixed-phase oxide shows a peak A attributable to the first phase at 2θ = 26.0 ± 0.1°.

3. The mixed-phase oxide according to claim 2, wherein the XRD pattern of the mixed-phase oxide shows a peak B attributable to the second phase at 2θ = 24.9 ± 0.1°.

4. The intensity I of the peak B Ｂ of the peak A Ａ is such that the ratio to is 0 < I Ｂ / I Ａ ≤ 0.4, or 0.01 ≤ I Ｂ / I Ａ ≤ 0.25, or 0.05 ≤ I Ｂ / I Ａ ≤ 0.22, or 0.07 ≤ I Ｂ / I Ａ ≤ 0.

16. The mixed-phase oxide according to claim 3

5. The mixed-phase oxide according to any one of claims 1 to 4, wherein the weight ratio of the first phase to the second phase is 199:1 to 1:1, or 99:1 to 3:1, or 50:1 to 8:

1.

6. The mixed-phase oxide according to any one of claims 1 to 4, wherein the first phase forms at least 85% by weight, or at least 90% by weight, or at least 92% by weight of the mixed-phase oxide.

7. The mixed-phase oxide according to any one of claims 1 to 4, wherein the first phase and the second phase form at least 80% by weight, at least 90% by weight, or at least 95% by weight of the mixed-phase oxide.

8. The mixed-phase oxide according to any one of claims 1 to 4, containing 66 to 80 at% of Nb and 33 to 17 at% of Ti for all cations, and further containing >0 to 1 at% of M(III) and / or >0 to 2 at% of M(II).

9. The mixed-phase oxide according to any one of claims 1 to 4, wherein the amount of the combination of M(III) and M(II) is ≧0.05 at%, or ≧0.5 at%, or ≧0.6 at% with respect to the amount of Nb.

10. The mixed-phase oxide according to any one of claims 1 to 4, wherein the atomic ratio of Ti:Nb is at least 0.3:1, or at least 0.4:1, or 0.42:1 to 0.5:

1.

11. The mixed-phase oxide according to any one of claims 1 to 4, containing M(III), or containing M(III) and M(II).

12. The mixed-phase oxide according to any one of claims 1 to 4, wherein M(III) is Cr, Al, and mixtures thereof, and M(II) is Zn.

13. The mixed-phase oxide according to any one of claims 1 to 4, wherein M(III) is Cr, Al, and mixtures thereof, or M(III) is Cr.

14. The mixed-phase oxide according to any one of claims 1 to 4, wherein M(II) is Zn, Cu, and mixtures thereof, or M(II) is Zn.

15. The mixed-phase oxide according to any one of claims 1 to 4, comprising M(III) and M(II), wherein M(III) is Cr and M(II) is Zn.

16. The mixed-phase oxide is in particulate form, and optionally the mixed-phase 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 The mixed-phase oxide according to any one of claims 1 to 4, having a particle size of.

17. The mixed-phase oxide has a BET surface area in the range of 0.1 to 100 m ２ / g, or 0.25 to 50 m ２ / g, or 0.5 to 20 m ２ / g. The mixed-phase oxide according to any one of claims 1 to 4.

18. The mixed-phase oxide according to any one of claims 1 to 4, wherein the mixed-phase oxide has a crystallite size greater than 180 nm, or greater than 200 nm, or greater than 225 nm, or greater than 250 nm.

19. Further comprising at least one additional element, and optionally, the additional element is (i) Zr, Hf, V, Fe, Ta, Mo, W, Mn, Co, Ni, Cd, B, Si, Sn, P, and mixtures thereof, or (ii) Zr, V, Fe, Mo, W, Mn, Co, Ni, Cd, B, Si, P, and mixtures thereof, or (iii) The mixed-phase oxide according to any one of claims 1 to 4, selected from Zr, V, Fe, Mo, W, P, and mixtures thereof.

20. The mixed-phase oxide according to claim 19, wherein the at least one additional element is present in a total amount of ≦ 5 at%, or ≦ 1 at%, or ≦ 0.5 at% based on the amount of Nb.

21. (i) F, Cl, Br, I, N, S, Se, and mixtures thereof, or (ii) F, Cl, N, S, and mixtures thereof, or (ii) The mixed-phase oxide according to any one of claims 1 to 4, further comprising at least one electronegative element selected from F, N, and mixtures thereof.

22. The mixed-phase oxide according to claim 21, wherein the at least one electronegative element is present in a total amount of ≦ 5 at% or ≦ 1 at% based on the amount of O.

23. The mixed-phase oxide according to any one of claims 1 to 4, wherein the interpenetrating mixture of the first phase and the second phase does not form a core / shell structure.

24. The mixed-phase oxide according to any one of claims 1 to 4, wherein the mixed-phase oxide is coated with carbon.

25. A composition comprising a mixed-phase oxide according to any one of claims 1 to 4 and at least one other component, optionally wherein the at least one other component is selected from a binder, a solvent, a conductive additive, a different active electrode material, and mixtures thereof.

26. An electrode comprising a mixed-phase oxide according to any one of claims 1 to 4 as an active electrode material.

27. The electrode according to claim 26, wherein the mixed-phase oxide forms at least 25 wt%, at least 50 wt%, or at least 75 wt% of the total active electrode material of the electrode, or wherein the mixed-phase oxide is the sole active electrode material of the electrode.

28. The electrode according to claim 26, further comprising at least one other component selected from a binder, a conductive additive, a different active electrode material, and mixtures thereof.

29. The electrode according to claim 28, wherein the different active electrode material is selected from lithium titanate, titanium niobate, different mixed-phase oxides, graphite, hard carbon, soft carbon, silicon, their doped and / or carbon-coated versions, and mixtures thereof.

30. A metal ion battery optionally comprising the electrode according to claim 26, wherein the metal ion battery is a lithium ion battery and the electrode forms an anode.

31. A lithium ion battery having a reversible anode active material specific capacity greater than 230 mAh / g at 23 mA / g, and while maintaining more than 70% of the initial cell capacity at 23 mA / g, the battery can be charged and discharged at a current density with respect to the anode active material of 230 mA / g or more, or 1000 mA / g or more, or 2000 mA / g or more, or 4000 mA / g or more.

32. Use of a mixed-phase oxide, wherein the mixed-phase oxide is as described in any one of claims 1 to 4 as an active electrode material in a metal ion battery, optionally in the anode of a lithium ion battery.

33. A method of manufacturing an electrode, comprising obtaining a mixed-phase oxide according to any one of claims 1 to 4, and depositing the mixed-phase oxide on a current collector to form the electrode.

Images