Electrode active material

Abstract

The present invention provides a method for producing an electrode active material, the method comprising processing a precursor mixture comprising a niobium precursor, a titanium precursor, and a metal halide to form an electrode active material, wherein the atomic ratio of Nb:Ti in the precursor mixture is >2, and the atomic ratio of cations:anions in the precursor mixture is greater than or equal to TiNbO, ... 10 O 29 , TiNb 14 O 37 , or TiNb 24 O 62 The cation:anion atomic ratio does not correspond to the active material TiNb2O7, Ti2Nb 10 O 29 , TiNb 14 O 37 , and / or TiNb 24 O 62 The present invention relates to a method for producing a compound having a crystal structure of

Description

[Technical Field]

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

[0002] Lithium-ion (Li-ion) batteries are a commonly used type of rechargeable battery, with the global market predicted to grow to $200 billion by 2030. Li-ion batteries are the technology of choice for electric vehicles, which meet multiple demands from technical performance to environmental impact, providing a viable path to a green automotive industry.

[0003] A typical lithium-ion battery consists of multiple cells connected in series or parallel. Each cell usually consists of an anode (negative electrode) and a cathode (positive electrode), separated by a porous, electrically insulating film (called a separator) and immersed in a liquid (called an electrolyte) that allows the transport of lithium ions.

[0004] In most systems, the electrode consists of an active electrode material, meaning a material that can chemically react with lithium ions to reversibly store and release them in a controlled manner, optionally mixed with a conductive additive (e.g., carbon) and a polymeric binder. A slurry of these components is coated as a thin film onto a current collector (usually a thin foil of copper or aluminum), thereby forming an electrode upon drying.

[0005] In known Li-ion battery technologies, graphite anodes have limitations in battery safety during charging, posing a major obstacle to their application in high-power electronics, automobiles, and industrial applications. Under standard conditions, lithium ions intercalate into the anode active material during charging. At high charge rates, the voltage profile of typical graphite is at high risk of overpotentially lowering the anode site below 0 V vs. Li / Li+, resulting in lithium ions instead depositing as lithium metal on the graphite electrode surface, a phenomenon known as lithium dendrite electroplating. This results in an irreversible loss of active lithium and therefore a rapid decline in cell capacity. In some cases, these dendritic deposits can grow to such a large size that they can penetrate the battery separator, causing a short circuit in the cell. This can trigger catastrophic cell failure, resulting in fire or explosion. Therefore, the fastest-charging batteries with graphite anodes are limited to charge rates of 5–7 C, although many are significantly lower.

[0006] Lithium titanate (Li4Ti5O 12 Among a wide range of recently proposed alternatives, mixed niobium oxides (MNOs, defined herein as oxides containing niobium and at least one other cation) have emerged as leading candidates to replace graphite as active materials for high-power and fast-charging applications.

[0007] LTO anodes exhibit excellent cycle life because their high charge potential (1.6 V vs. Li / Li+) prevents dendrite electroplating at high charge rates and their three-dimensional crystalline structure prevents the significant volume expansion of the active material associated with Li-ion intercalation. For these two reasons, LTO cells are generally considered to be highly safe. However, LTO's relatively poor electronic and ionic conductivity limits its capacity retention and resulting power performance at high rates unless the material is nanosized to increase its specific surface area. Carbon coatings can be used to enhance electronic conductivity and / or avoid reactions with the electrolyte (He, YB. et al., Sci Rep 2, 913 (2012) and Han, C. et al., J. Mater. Chem. A, 2017, 5, 6368-6381). This particle-level material engineering increases the porosity and specific surface area of ​​the active material, significantly reducing the packing density achievable in the electrode. This is due to the low density of the electrodes and the high proportion of electrochemically inactive materials (e.g. binders, carbon additives), which leads to a significant decrease in gravimetric and volumetric energy density.

[0008] An important indicator of anode performance is the volumetric capacity (mAh / cm) of the electrode. 3 ), i.e., the amount of charge (i.e., lithium ions) that can be stored per unit volume of the anode. This amount, when combined with the cathode and appropriate cell design parameters, is a key factor in determining the overall battery energy density (Wh / L) on a volumetric basis. The volumetric capacity of an electrode is related to the electrode density (g / cm 3 ), the specific capacity of the active material (mAh / g), and the percentage of active material in the electrode. LTO anodes typically have a relatively low specific capacity (approximately 165 mAh / g, compared to approximately 330 mAh / g for graphite), which explains the low electrode density mentioned above (typically <2.0 g / cm 3 ) and the low proportion of active material (<90%), resulting in a very low volumetric capacity (<300mAh / cm 3), resulting in lower battery energy density and higher $ / kWh (dollar per kWh) costs for many applications. As a result, LTO batteries are generally limited to specific niche applications, despite their long cycle life, fast charging capabilities, and safety.

[0009] MNO has attracted attention as an alternative to LTO because it exhibits similar properties such as fast charging and long cycle life. Furthermore, MNO has a larger capacity than LTO, which means the battery has a higher energy density. However, MNO may have other drawbacks. TiNb2O7 and Ti2Nb 10 O 29 Several studies have reported that titanium niobium oxides such as TiNb2O7 have a problem with gassing, where gas species are generated by interfacial reactions with the electrolyte (Buannic et al., J. Mater. Chem. A, 2016, 4, 11531-11541; Parikh et al., ACS Appl. Mater. Interfaces 2021, 13, 46, 55145-55155; and Wu et al., ACS Appl. Mater. Interfaces 2018, 10, 32, 27056-27062). The gas generation mechanism of TiNb2O7 is still unclear, and researchers have proposed that it may be due to the presence of trace amounts of water, Ti, or other metals. 4+These findings suggest the possibility of catalytic effects due to the metal oxide nature of MNO. Furthermore, due to its metal oxide nature, the ionic and electronic conductivity must be improved to achieve optimal performance at high power (GB2598438B, GB2588254B). Furthermore, the formation of titanium niobium oxide via solid-state reactions is extremely energy-intensive. Generally, a reaction temperature of 1200 °C is required for complete formation of TiNb2O7, which requires a long time, making cost-effective mass production difficult. Therefore, areas for improvement in titanium niobium oxide include: (i) processability—reducing the reaction energy and shortening the synthesis temperature and time are desirable; (ii) ionic and electronic conductivity—higher conductivity improves the performance of Li-ion battery cells at high charge / discharge rates; and (iii) reducing the reaction with the electrolyte to improve the first-cycle coulombic efficiency and cycle life.

[0010] US Published Patent Application Publication US20200140339A1 discloses Ti (1-x) M1 x Nb (2-y) M2 y O (7-z) Q z or Ti (2-x’) M1 x’ Nb (10-y) M2 y’ O (29-z’) Q z’ where M1 is Li, Mg, or a combination thereof, M2 is Fe, Mn, V, Ni, Cr, or a combination thereof, and Q is F, Cl, Br, I, S, or a combination thereof, and 0≦x≦0.15, 0≦y≦0.15, 0.01≦z≦2, 0≦x′≦0.3, 0≦y′≦0.9, and 0.01≦z′≦8. Therefore, the doped titanium niobium oxide referred to in U.S. Published Patent Application US20200140339A1 is a doped titanium niobium oxide having a chemical composition of TiNb2O7 or Ti2Nb 10 O 29 requires the same cation:anion ratio as

[0011] US Published Patent Application US20210296631A1 describes an active material composite of titanium niobium oxide having fluorine atoms on at least a portion of the surface, wherein the fluorine level on the electrode surface is 3.5≦A F / (A Ti +A Nb )≦50. The fluorine source of the electrode is derived from the electrolyte and is formed after the battery is assembled as a post-treatment, for example, by a pulse charging treatment.

[0012] AlF 3は It has been used as a coating to improve the diffusivity of Li ions in LTO and to tailor the surface reactivity (Li, et al., Electrochimica Acta, 2014, 139, 104; Chung, et al., Journal of Electroanalytical Chemistry, 2019, 837, 240).

[0013] International Patent Application Publication No. WO2008100002A1 describes an anode active material with a fluorine-based surface coating to reduce electrolyte side reactions. The material is prepared by dispersing the anode material in a metal salt and fluorine precursor solution, followed by calcination to form the fluorine-based coating. Examples include graphite-based anode active materials, where optimization of electrolyte side reactions and the solid electrolyte interface (SEI) is important. Summary of the Invention

[0014] In a first aspect, the present invention provides a method of making an electrode active material, the method comprising treating a precursor mixture comprising a niobium precursor, a titanium precursor, and a metal halide to form an electrode active material; the atomic ratio of Nb:Ti in the precursor mixture is >2; The atomic ratio of cations to anions in the precursor mixture was TiNb2O7, Ti2Nb 10 O 29 , TiNb 14 O 37 , or TiNb 24 O 62does not correspond to the atomic ratio of cations to anions, The electrode active material is TiNb2O7, Ti2Nb 10 O 29 , TiNb 14 O 37 , and / or TiNb 24 O 62 The method further provides a method for producing a compound having a crystal structure of

[0015] As shown in this example, the inventors have discovered that the electrode active material prepared according to the first embodiment exhibits excellent capacity retention and high first-cycle coulombic efficiency even when delithiated at rates up to 10 C. Compared to pure titanium niobium oxide, the electrode active material is improved. These results are important in demonstrating the advantages of the metal halide-modified titanium niobium oxide of the present invention for use in high-power batteries designed for high-rate charging and discharging.

[0016] The inventors have found that the atomic ratio of cations to anions is similar to that of the base material (TiNb2O7, Ti2Nb 10 O 29 , TiNb 14 O 37 , or TiNb 24 O 62 ), i.e., in an "off-stoichiometric ratio," the use of metal halides surprisingly makes it possible to obtain the crystalline structure of the base material in the resulting electrode active material. The "off-stoichiometric ratio" of the active electrode is believed to induce disorder and / or defects in the crystalline structure, which is believed to contribute to the observed improved properties. Furthermore, the use of metal halides has been found to favor the formation of the desired crystalline structure, allowing for synthesis at lower temperatures and shorter synthesis times, resulting in more economical electrode active materials.

[0017] In a second aspect, the present invention provides an electrode active material obtainable by the method of the first aspect.

[0018] In a third aspect, the present invention provides a composition comprising the electrode active material of the second aspect and at least one other component, optionally the at least one other component selected from a binder, a solvent, a conductive additive, a different electrode active material, and mixtures thereof.

[0019] In a fourth aspect, the present invention provides an electrode comprising the electrode active material of the second aspect, optionally deposited on a current collector.

[0020] In a fifth aspect, the present invention provides a metal-ion battery comprising the electrode of the fourth aspect, optionally wherein the metal-ion battery is a lithium-ion battery or a sodium-ion battery and the electrode forms the anode.

[0021] In a sixth aspect, the present invention provides the use of an electrode material according to the second aspect in a metal-ion battery, optionally for use in the anode of a lithium-ion battery or a sodium-ion battery. [Brief explanation of the drawings]

[0022] [Figure 1] XRD patterns of Examples 1 to 4 [Figure 2] XRD patterns of Examples 5 to 7 [Figure 3] XRD pattern of Comparative Example A [Figure 4] XRD pattern of Comparative Example B [Figure 5] XRD pattern of Comparative Example C [Figure 6] XRD pattern of Comparative Example D [Figure 7] XRD pattern of Comparative Example E [Figure 8] XRD pattern of comparative example F [Figure 9] XRD pattern of Example 8 DETAILED DESCRIPTION OF THE INVENTION

[0023] The electrode active material is TiNb2O7, Ti2Nb10 O 29 , TiNb 14 O 37 , and / or TiNb 24 O 62 These crystal structures belong to the Wadsley-Roth type phase group. The Wadsley-Roth type crystal structure is a crystallographic off-stoichiometry of the MO3 (ReO3) crystal structure that includes crystallographic shear, and MO 3-x As a result, these structures typically contain octahedral [MO6] subunits in the crystal structure. Phases with such structures are believed to have advantageous properties for use as electrode active materials, for example in lithium-ion batteries. The open, tunnel-like crystal structure is an ideal candidate for high-capacity Li-ion storage and fast intercalation / deintercalation. The crystallographic off-stoichiometry present in the crystal structure induces Wadsley-Roth crystallographic superstructures. These superstructures, combined with other properties such as the Jahn-Teller effect and enhanced crystallographic disorder due to the use of multiple mixed cations, stabilize the crystal, keep the tunnels open and stable during intercalation, and promote high Li-ion diffusion rates (approximately 10–13 cm). 2 s -1 The mixed niobium oxides have a high redox potential of >0.8 V vs. lithium, enabling safe and long-life operation, which is crucial for fast-charging battery cells. Furthermore, the niobium cation can undergo two redox reactions per atom, resulting in a higher theoretical capacity than, for example, LTO.

[0024] The TiNb2O7 crystal structure belongs to the monoclinic system with the A2 / m space group. It can be described as having a 3x3x∞ crystallographic block structure of [MO6] octahedra, where M is Ti or Nb. The crystal structure of TiNb2O7 can be found in PDF card [01-072-0116] (Wadsley, AD, Acta Crystallogr., 14, 660, (1961)). The unit cell parameters are typically within the following ranges: a is 11.90-11.94 Å, b is 3.80-3.82 Å, and c is 20.38-20.45 Å. The unit cell angles may be α = γ = 90°, and β may be 120.10-120.30°. Materials with the TiNb2O7 crystal structure can be identified by a characteristic peak at 2θ = 26.0 ± 0.2° in the XRD pattern using Cu K-α radiation.

[0025] Ti2Nb 10 O 29 The crystal structure of Ti2Nb can be either monoclinic or orthorhombic, or can be considered a mixture of both. It can be described as having a 3x4x∞ crystallographic block structure of [MO6] octahedra, where M is Ti or Nb. Monoclinic Ti2Nb 10 O 29 The crystal structure of orthorhombic TiNb can be found under ICSD identification number 15474 (Wadsley, AD, Acta Crystallogr., 14, 664, (1961)). 10 O 29The crystal structure of Ti2Nb can be referenced under ICSD identification number 22000 (RB von Dreele, AK Cheetham, Proceedings of the Royal Society London, Series A, 338, 311, (1974)). The unit cell parameters are typically within the following ranges for an orthorhombic unit cell: a is 28.30-28.70 Å, b is 3.78-3.83 Å, and c is 20.35-20.70 Å. The unit cell angles may be α = β = γ = 90°. The monoclinic unit cell is typically within the following ranges: a is 20.54-20.57 Å, b is 3.80-3.82 Å, and c is 15.52-15.55 Å. The unit cell angles may be α = γ = 90°, and β is 113.00-113.70°. 10 O 29 A material having a crystalline structure can be identified by having a characteristic peak at 2θ=24.9±0.2 in an XRD pattern using Cu K-α radiation.

[0026] TiNb 14 O 37 The crystal structure belongs to the monoclinic system. It can be described as having a 3x5x∞ crystallographic block structure consisting of [MO6] octahedra, where M is Ti or Nb. The crystal structure is reported in Brunner, H., et.al., Zeitschrift fur Naturforschung B, 31, 5, 549, (1976). The unit cell parameters are typically within the following ranges: a is 20.00-21.60 Å, b is 3.81-3.83 Å, c is 29.82-30.15 Å, α = γ = 90°, and β is 94.50-95.50°. TiNb 14 O 37 A material having a crystalline structure can be identified by having a characteristic peak at 2θ=23.8±0.2 in an XRD pattern using Cu K-α radiation.

[0027] TiNb 24 O 62The crystal structure is monoclinic with a C2 space group. It can be described as having a 3 × 4 × 0.5 crystallographic block structure composed of 3 × 4 [MO6] octahedral blocks, where M is Ti or Nb, with 0.5 NbO4 tetrahedra per block. TiNb 24 O 62 The crystal structure of TiNb can be found in PDF card [01-072-1655] (Roth, RS, Wadsley, AD, Acta Crystallogr., 18, 724, (1965)). The unit cell parameters are typically in the following ranges: a is 29.59-29.98 Å, b is 3.80-3.84 Å, and c is 20.91-21.29 Å. The unit cell angles have α = γ = 90°, and β can be 94.2-95.6°. 24 O 62 A material having a crystalline structure can be identified by having a characteristic peak at 2θ=24.7±0.2 in an XRD pattern using Cu K-α radiation.

[0028] The crystalline structure adopted as the electrode active material can be controlled by controlling the atomic Nb:Ti ratio in the precursor mixture. Preferably, the electrode active material is TiNb2O7 and / or Ti2Nb 10 O 29 , most preferably TiNb2O7. Crystal structure can be determined by analyzing X-ray diffraction (XRD) patterns obtained using Cu K-α radiation, as is widely known. For example, the XRD pattern obtained from a given material can be compared with known XRD patterns from a public database, such as the ICDD Crystallography Database, to confirm the crystal structure. Rietveld and Pauly analyses can also be used to determine the crystal structure of a material, particularly the unit cell parameters. Thus, the crystal structure of an electrode active material can be determined by XRD.

[0029] The electrode active material may have a mixed crystal structure, where two or more crystal structures are present. For example, a TiNb2O7 crystal structure and a Ti2Nb 10 O 29However, the electrode active material may have a single predominant crystal structure (e.g., TiNb2O7 or Ti2Nb 10 O 29 ), with other crystalline structures preferably present at <10 wt%, <5 wt%, or <1 wt%, as determined, for example, by XRD analysis with Cu K-α radiation. 10 O 29 , TiNb 14 O 37 , or TiNb 24 O 62 ; or TiNb2O7 or Ti2Nb 10 O 29 The electrode active material may have a single-phase crystalline structure consisting of a crystalline structure of TiNbO; most preferably, it may have a single-phase crystalline structure consisting of a crystalline structure of TiNbO. When the electrode active material has a single-phase crystalline structure, it will be understood that no other phases will be detected by XRD analysis using Cu K-α radiation. It will be understood that the single-phase electrode active material of the present invention may then be mixed with additional materials of different crystalline structures to form, for example, electrode compositions described herein.

[0030] Those skilled in the art will understand that single phase generally refers to a body of material with a uniform chemical composition and structure. In practical terms, a single phase can be described by the relative average arrangement and identity of ions in the crystalline structure and their characteristic range of variation, as determined by measurements on a representative sample of the entire material. Because perfect uniformity in chemical composition and structure is virtually impossible due to unavoidable practical and physical limitations, such as defects, impurities, disorder, and distortion, tolerances must be established based on the limitations of available measurement techniques, such as XRD analysis.

[0031] The atomic ratio of cations to anions in the precursor mixture was TiNb2O7, Ti2Nb 10 O 29 , TiNb 14 O 37 , or TiNb 24 O 62The atomic ratio of cations to anions in TiNb2O7 is 3:7 (1 × Ti + 2 × Nb: 7 × O), whereas the atomic ratio of cations to anions in TiNb2O7 is 3:7 (1 × Ti + 2 × Nb: 7 × O). 10 O 29 The atomic ratio of cations to anions is 12:29, and TiNb 14 O 37 The atomic ratio of cations to anions is 15:37, and TiNb 24 O 62 The atomic ratio of cations to anions in the precursor mixture is 25:62. For example, the atomic ratio of cations to anions in a precursor mixture containing Nb2O5:TiO2:AlF3 in a molar ratio of 1:0.94:0.01 is 2.95:6.91 (1 x 2 x Nb + 0.94 x 1 x Ti + 0.01 x 1 x Al:1 x 5 x O + 0.94 x 2 x O + 0.01 x 3 x F). Surprisingly, when metal halides are used in the precursor mixture, even single phases such as TiNb2O7, Ti2Nb 10 O 29 , TiNb 14 O 37 , and / or TiNb 24 O 62 It was found that the crystal structure of

[0032] The atomic ratio of Nb:Ti in the precursor mixture is >2. Optionally, the atomic ratio of Nb:Ti in the precursor mixture is 5, 14, or 24 (TiNb 10 O 29 , TiNb 14 O 37 , and TiNb 24 O 62 (atomic ratio in

[0033] If the cation:anion ratio is kept the same as the base material composition and one element is partially substituted with another, the material likely maintains the base crystal structure and compensates for potential valence changes by partially oxidizing or reducing the other element. For example, if 4+ cations are replaced with 3+ cations, the 5+ cations in the system may be partially reduced to 4+. In this invention, the cation:anion atomic ratio is intentionally set to a non-stoichiometric ratio, i.e., not the same ratio as the base titanium niobium material. This, combined with the high electronegativity of the halide anions, is thought to induce a stronger Jahn-Teller effect, causing stronger distortion of the octahedrons, increasing the entropy of the system and therefore reducing the reaction energy. In this way, electrode active materials can be synthesized more economically, as shown in the examples. Furthermore, the addition of extra valence electrons from the halide anion can change the occupancy of the Nb 4d orbital and the O 2p orbital, shifting the Fermi level toward the conduction band and potentially exhibiting higher electronic conductivity (El-Shazly, et al., Applied Physics A, 2016, 122, 859). This improves the properties of the electrode active material used in lithium-ion battery anodes, such as the capacity and capacity retention at high delithiation rates, as shown in the examples.

[0034] The precursor mixture includes a niobium precursor, a titanium precursor, and a metal halide. The precursor may be one or more metal oxides, metal hydroxides, metal salts (e.g., NO3 - ,SO3 - ) or ammonium salts. Preferably, the niobium and titanium precursors are not metal halides.

[0035] Examples of suitable niobium precursors include Nb2O5, Nb(OH)5, niobic acid, NbO, ammonium niobium oxalate, NbO2, NbO2F, Nb3O7F, niobium chloride, niobium fluoride, and niobium bromide. Typically, the oxidation state of Nb in the niobium precursor is 5+. Preferably, the niobium precursor is a niobium oxide, such as Nb2O5.

[0036] Examples of suitable titanium precursors include TiO2, titanium chloride, titanium fluoride, titanium bromide, titanium oxalate, ammonium titanyl oxalate or ammonium titanyl nitrate, titanyl nitrate, titanyl sulfate, titanyl hydroxide, and ammonium bis(oxalate)oxotitanate. Typically, the oxidation state of Ti in the titanium precursor is 4+. Preferably, the titanium precursor is TiO2.

[0037] Examples of suitable metal halides include MgNb 14 O 35 F2, ZnNb 14 O 35 Examples of suitable metal halides include F2, zirconium chloride, zirconium fluoride, zirconium bromide, copper chloride, copper fluoride, copper bromide, zinc chloride, zinc fluoride, zinc bromide, and aluminum chloride, as well as aluminum fluoride, aluminum bromide, germanium chloride, germanium fluoride, germanium bromide, gallium chloride, gallium fluoride, gallium bromide, tin bromide, tin chloride, tin fluoride, iron chloride, iron fluoride, iron bromide, manganese bromide, manganese chloride, manganese fluoride, magnesium fluoride, magnesium chloride, magnesium bromide, nickel fluoride, nickel chloride, nickel bromide, chromium fluoride, chromium chloride, and chromium bromide. Preferably, the metal in the metal halide is not Nb or Ti. In this way, the base niobium titanium oxide is substituted with a different cation, contributing to the presence of disorder and / or defects. The oxidation state of the metal in the metal halide can be +4 or less, such as +3 or +2. When the oxidation state is +3 or less, the base niobium titanium oxide is 4+ Cations and Nb 5+The cations are replaced by cations of lower oxidation states than the cations, further contributing to the presence of disorder and / or defects. The metal of the metal fluoride may be Mg, Al, Zn, Cr, Ni, Nb, Cu, Mn, Fe, Zr, Ga, Ge, Sn, and mixtures thereof, or may be selected from the group consisting of Al, Zn, Cr, Fe, Zr, Nb, and mixtures thereof, or Al, Zn, and mixtures thereof. The metal halide may be a metal fluoride, a metal chloride, a metal bromide, or a metal fluoride or metal chloride, and most preferably, the metal halide is a metal fluoride. For example, the metal fluoride may be selected from ZnF2 and / or AlF3.

[0038] The metal halide can be present in an amount such that the metal of the metal halide is present at ≧0.1 at%, 0.2-5 at%, 0.3-3 at%, or ≦6 at%, relative to the amount of Nb and Ti in the precursor mixture.

[0039] The precursor material may not contain metal oxides or may contain ion sources other than oxides. For example, the niobium and / or titanium precursors may be prepared by dissolving metal salts (e.g., NO3 - , SO3 - ) or other compounds (e.g., oxalates, carbonates).

[0040] The precursor mixture may further include precursors other than the niobium precursor, the titanium precursor, and the metal halide. For the replacement of the base material with additional cations, the precursor mixture may include one or more metal oxides or metal salts. Examples of cation-substituted precursor materials include, but are not limited to, the following: NH4H2PO4, (NH4)2PO4, (NH4)3PO4, PO5, H3PO3, Ta2O5, WO3, ZrO2, TiO2, MoO3, VO5, ZrO2, CuO, Cr2O3, ZnO, Al2O3, KO, KOH, CaO, GeO2, Ga2O3, SnO2, CoO, Co2O3, Fe2O3, Fe3O4, MnO, MnO2, NiO, Ni2O3, H3BO3, Li2CO3, Na2CO3, Mg5(CO3)4(OH)2.5H2O, and MgO. To further replace oxygen anions with other electronegative anions, the precursor may include one or more organic compounds, polymers, inorganic salts, organic salts, gases, or ammonium salts, examples of which include melamine, NH4HCO3, NH3, NHF, PVDF, PTFE, NHCl, NH4Br, NHCl, Br2, Cl2, I2, ammonium oxychloride amide, and hexamethylenetetramine. The precursor mixture may include less than 10 wt%, less than 5 wt%, or less than 1 wt% of additional precursors. The precursor mixture may include a niobium precursor, a titanium precursor, and a metal halide.

[0041] If it is desired to produce an electrode active material containing a cation in a particular oxidation state, a precursor containing the cation in that oxidation state can be selected. For example, Mn 2+ When producing an electrode active material containing Mn, MnO can be used as a precursor. 4+ When producing an electrode active material containing MnO2, MnO2 can be used as a precursor.

[0042] It will be appreciated that the electrode active material may further comprise Li and / or Na, which may be reversibly intercalated in situ when the electrode active material is in a metal ion battery.

[0043] Some or all of the precursors may be particulate materials. If they are particulate materials, they preferably have a diameter of less than 20 μm, for example, D of 10 nm to 20 μm. 50 The particle size of the precursor material may be less than 20 μm, since the particle size of the precursor material may be reduced mechanically, for example, by grinding during the step of mixing the precursor materials to form the precursor material mixture.

[0044] Comminution of the precursors to obtain the desired particle size may be carried out by a process selected from grinding milling, impact milling, air jet milling, steam jet milling, high energy milling, high shear milling, pin milling, air classification, wheel classification, sieving, cyclone separation, and / or bead milling. Mixing of the precursors to form a precursor mixture may be carried out by a process selected from dry or wet / solvated planetary ball milling, tumbling ball milling, high energy ball milling, bead milling, pin milling, high shear milling, planetary mixing, powder mixing, impaction milling, high shear and / or intensive mixer mixing. The force used for mixing and / or milling may depend on the morphology of the precursor material. For example, if some or all of the precursors have a larger particle size (e.g., D greater than 20 μm), the mixing may be carried out by a process selected from dry or wet / solvated planetary ball milling, tumbling ball milling, high energy ball milling, bead milling, pin milling, high shear milling, planetary mixing, powder mixing, impaction milling, high shear and / or intensive mixer mixing. 50 When the precursor mixture has a particle size (particle size), the grinding force can be selected to reduce the particle size of the precursor so that the particle size of the precursor mixture is 20 μm or less. Having particles in the precursor mixture with a particle size of 20 μm or less can more efficiently promote the reaction of the precursor during the processing step to form the electrode active material. Processing of the precursor mixture can include, for example, solid-state synthesis performed in a solid-state chamber formed from the precursor powder at high pressure (e.g., >10 MPa).

[0045] Treating the precursor mixture preferably includes heating the precursor mixture. Heating can be carried out for 1 to 48 hours, 2 to 24 hours, or preferably 3 to 18 hours. For example, heating 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 heating time can be 24 hours or less, 18 hours or less, 16 hours or less, or 12 hours or less. Heating can be carried out at 400 to 1350°C, 800 to 1250°C, or preferably 1000 to 1125°C. It has been found that by using the precursor mixture according to the present invention, an electrode active material having a desired crystal structure can be synthesized more economically.

[0046] Heating of the precursor mixture can be carried out in a gas atmosphere, preferably N2 or air, preferably in the absence of water. Suitable gas atmospheres include air, N2, Ar, He, CO2, CO, O2, H2, NH3, and mixtures thereof. The gas atmosphere can also be a reducing atmosphere. If it is desired to produce an oxygen-deficient material, the step of heat-treating the precursor mixture is preferably carried out in an inert or reducing atmosphere.

[0047] In some methods, a two-step heat treatment may be performed. For example, the precursor mixture may be heated at a first temperature for a first time period, followed by a second temperature for a second time period. Preferably, the second temperature is higher than the first temperature. Such a two-step heat treatment may support a solid-state reaction to form the desired crystalline structure. This may be performed sequentially or with an intermediate re-grinding step.

[0048] Processing the precursor mixture to form the electrode active material includes conventional ceramic synthesis techniques. For example, the electrode active material can be formed by one or more of solid-state synthesis, sol-gel synthesis, hydrothermal or microwave hydrothermal synthesis, solvothermal or microwave solvothermal synthesis, co-precipitation synthesis, spark or microwave plasma synthesis, combustion synthesis, electrospinning, spray pyrolysis, chemical vapor deposition, and atomic layer deposition. Optionally, processing the precursor mixture includes solid-state synthesis, hydrothermal or microwave hydrothermal synthesis, solvothermal or microwave solvothermal synthesis, co-precipitation synthesis, and / or chemical vapor deposition. Most preferably, processing the precursor mixture includes solid-state synthesis.

[0049] Solid-state synthesis is a widely used method for chemically reacting solid starting materials to form new solids. It generally involves measuring solid precursors to the intended elemental ratio, mixing the precursors (e.g., wet or dry milling), and heating the precursor mixture to promote a solid-state reaction to yield the desired product. It may also include additional steps such as spray drying (e.g., after precursor mixing) or deagglomeration (e.g., after heating).

[0050] To provide an electrode active material comprising more electronegative anions than the halide from oxygen and metal halide, the method can further include mixing the electrode active material with a precursor comprising more electronegative anions to provide a further precursor mixture, and heat treating the further precursor mixture at a temperature in the range of 300-1200°C or 800-1100°C, optionally under reducing conditions, which can provide an electrode active material comprising additional electronegative anions.

[0051] For example, to provide an N-containing electrode active material, the method can further include mixing the electrode active material with an N-containing precursor (e.g., melamine or urea) to provide a further precursor mixture, and heat-treating the further precursor mixture under reducing conditions (e.g., in a N atmosphere) at a temperature in the range of 300 to 1200°C, whereby the N-containing electrode active material can be provided.

[0052] For example, to provide an F-containing electrode active material (e.g., when the metal halide does not contain F), the method can further include mixing the electrode active material with an F-containing precursor (e.g., polyvinylidene fluoride or NHF) to provide a further precursor mixture, and heat-treating the further precursor mixture under oxidizing conditions (e.g., in air) at a temperature in the range of 300 to 1200°C, which provides an F-containing electrode active material.

[0053] The method may further comprise the step of heat treating the electrode active material under reducing conditions at a temperature in the range of 400-1350° C. or 800-1250° C., which generates oxygen vacancies in the electrode active material.

[0054] The method may include one or more post-treatment steps after the formation of the electrode active material. In some cases, the method may include a post-treatment step of heat-treating the electrode active material, which may be referred to as “annealing.” This post-treatment heat-treatment step may be performed in a different gas atmosphere than the step of treating the precursor mixture to form the electrode active material. The post-treatment heat-treatment step may be performed in an inert or reducing gas atmosphere. Such a post-treatment heat-treatment step may be performed at a temperature above 500°C, e.g., about 900°C. It may be beneficial to include a post-treatment heat-treatment step to create additional disorder or defects in the electrode active material or to perform anion exchange (e.g., N exchange for O anions) on the electrode active material, for example, to change the electron distribution or electronic band structure.

[0055] The method can include grinding and / or classifying the electrode active material (e.g., impact grinding, jet grinding, steam jet grinding, high energy grinding, high shear grinding, pin grinding, air classification, wheel classification, sieving, cyclone separation, bead grinding) to provide a material having any of the particle size parameters provided herein.

[0056] The electrode active material is preferably in the form of fine particles. The active electrode material has a diameter of D in the range of 0.1 to 100 μm, or 0.5 to 50 μm, or 1 to 20 μm. 50 These particle sizes are advantageous because they are easy to process and manufacture into electrodes. Furthermore, these particle sizes eliminate the need to use complex and / or expensive methods to produce nano-sized particles. Nano-sized particles (e.g., D of 100 nm or less) can be used. 50 Particles with a particle size of 1000 nm or less are typically more complex to synthesize and require additional safety considerations.

[0057] The electrode active material has a D of at least 0.05 μm, or at least 0.1 μm, or at least 0.5 μm, or at least 1 μm. 10 It may have a particle size. 10 Maintaining particle size within these ranges reduces the potential for parasitic reactions in Li-ion cells due to reduced surface area, requires less binder in the electrode slurry, and facilitates processing.

[0058] The electrode active material has a D of 200 μm or less, 100 μm or less, 50 μm or less, or 20 μm or less. 90 It may have a particle size. 90 By maintaining the particle size within these ranges, the proportion of the particle size distribution having large particle sizes is minimized, facilitating the fabrication of the material into a homogeneous electrode.

[0059] The term "particle size" refers to the equivalent spherical diameter (esd), i.e., the diameter of a sphere having the same volume as a given particle, the particle volume being understood to include the volume of any intra-particle voids. n " and "Dn The term "particle size" refers to the diameter below which n% by volume of the particle population is found, i.e., "D 50 " and "D 50 "Particle size" refers to the volume-based median particle size below which 50% by volume of the particle population is found. When a material contains primary crystallites aggregated into secondary particles, it is understood that the particle size refers to the diameter of the secondary particles. Particle size can be measured by laser diffraction. Particle size can be measured, for example, using Mie theory in accordance with ISO 13320:2009.

[0060] The electrode active material is 0.1 to 100 m 2 / g, or 0.2 to 50 m 2 / g, or 0.5 to 20 m 2 The electrode active material can have a BET surface area in the range of 0.1 μm / g. Generally, a low BET surface area is preferred to minimize reaction between the electrode active material and the electrolyte, for example, to minimize the formation of a solid electrolyte interfacial (SEI) layer during the first charge-discharge cycles of an electrode made from this material. However, if the BET surface area is too low, the bulk of the electrode active material may become inaccessible to metal ions in the surrounding electrolyte, resulting in unacceptably low charge rates and capacities.

[0061] "BET surface area" refers to the surface area per unit mass calculated from measurements of the physical adsorption of gas molecules on a solid surface using the Brunauer-Emmett-Teller theory. For example, BET surface area can be measured in accordance with ISO 9277:2010.

[0062] The electrode active material may be coated with carbon, for example to improve the electronic conductivity of the surface and / or to prevent reaction with the electrolyte, and therefore the method may include the further step of forming a carbon coating on the electrode active material.

[0063] The electrode active material may have a protective coating, optionally comprising niobium oxide, aluminum oxide, zirconium oxide, organic or inorganic fluorides, organic or inorganic phosphates, titanium oxide, lithiated versions thereof, and mixtures thereof.

[0064] The metal:titanium atomic ratio of the metal halide in the precursor mixture is preferably <0.3.

[0065] The present invention provides an electrode active material obtainable by the method of the first aspect. To confirm the presence of off-stoichiometry in accordance with the present invention, elemental analysis can be performed on the electrode active material, for example by ICP-OES, ICP-MS, XRF, EDS / X from SEM or TEM, and / or XPS.

[0066] The electrode active material may be part of a composition comprising the electrode active material and at least one other component, optionally the at least one other component selected from a binder, a solvent, a conductive additive, a different electrode active material, and mixtures thereof.

[0067] The electrode active material is usually incorporated into an electrode, which is typically in the form of an electrode composition in electrical contact with a current collector, which is typically a metal foil, such as copper or aluminum foil.

[0068] Accordingly, the present invention also provides a method of manufacturing an electrode, the method comprising producing an electrode active material by the method of the first aspect of the present invention, and forming an electrode comprising the electrode active material. Preferably, forming the electrode comprises depositing the electrode active material on a current collector.

[0069] The depositing step can include forming a slurry of the electrode active material and a solvent. The slurry can include at least one other component selected from a binder, a conductive additive, a different electrode active material, and mixtures thereof. The slurry can be deposited onto a current collector and the solvent can be removed, thereby forming an electrode layer on the current collector. A dry process that does not use a solvent to coat the current collector can also be used, such as by extrusion. Further steps, such as heat treatment to cure the binder and / or calendaring the electrode layer, can be optionally performed. For example, the solvent can be removed by drying, for example, at a temperature of 30 to 100°C. The electrode can be formed at a density of 2 to 3.5 or 2.4 to 2.9 g cm -3 The electrode layer may have a thickness in the range of 5 μm to 2 mm, preferably 5 μm to 1 mm, preferably 5 μm to 500 μm, preferably 5 μm to 200 μm, preferably 5 μm to 100 μm, preferably 5 μm to 50 μm.

[0070] Alternatively, the slurry can be formed into a free-standing film or mat comprising the electrode active material, for example, by casting the slurry into a suitable casting mold, removing the solvent, and then removing the casting mold. The resulting film or mat is in the form of a coherent, free-standing mass that can be bonded to a current collector by known methods.

[0071] Optionally, the electrode active material forms at least 5%, 10%, or 50% by weight of the total electrode active material in the electrode. The electrode active material may form the only electrode active material in the electrode.

[0072] The electrode composition may further comprise at least one other component selected from a binder, a conductive additive, a different electrode active material (e.g., an additional electrode active material of the present invention), and mixtures thereof. For example, one electrode composition comprises about 92 wt. % of the electrode active material of the present invention, about 5 wt. % of a conductive additive (e.g., carbon black), and about 3 wt. % of a binder (e.g., poly(vinyl difluoride)), based on the total dry weight of the electrode composition.

[0073] 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, polyetheramide, 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, cellulosic 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), hydrogenated form of NBR (HNBR), styrene butadiene rubber (SBR), and polyimides. The binder can be present in the electrode composition at 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.

[0074] The conductive additive is preferably a non-active material added to improve the conductivity between the electrode active materials and between the electrode active material and the current collector. The conductive additive may be appropriately selected from graphite, carbon black, carbon fiber, vapor-grown carbon fiber (VGCF), carbon nanotubes, graphene, acetylene black, ketjen black, metal fiber, metal powder, and conductive metal oxides. Preferred conductive additives include carbon black and carbon nanotubes. The conductive additive may be included 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.

[0075] The electrode active material 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 electrode active material is present in 100 wt% of the electrode composition, a solid electrode can be obtained.

[0076] If a different electrode active material is present in addition to the electrode active material, it may be selected from lithium titanium oxide, mixed niobium oxides such as titanium niobium oxide, different electrode active materials of the present invention, graphite, hard carbon, soft carbon, silicon, doped versions thereof, and mixtures thereof.

[0077] The electrode active material may be combined with lithium titanium oxide to form an electrode composition.

[0078] The lithium titanium oxide preferably has a spinel or ramsdellite crystal structure, as determined, for example, by X-ray diffraction. Examples of lithium titanium oxides having a spinel crystal structure include Li4Ti5O 12 An example of a lithium titanium oxide having a ramsdellite crystal structure is Li2Ti3O7. These materials have been shown to have excellent properties for use as electrode active materials. Thus, lithium titanium oxide is Li4Ti5O 12 and / or may have a crystal structure as determined by X-ray diffraction corresponding to Li2Ti3O7. Lithium titanium oxide may have a crystal structure as determined by X-ray diffraction corresponding to Li4Ti5O 12 , Li2Ti3O7, and mixtures thereof.

[0079] The lithium titanium oxide may be doped with additional cations or anions. The lithium titanium oxide may be oxygen deficient. The lithium titanium oxide may include a coating, optionally selected from carbon, polymer, metal, metal oxide, metalloid, phosphate, and fluoride.

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

[0081] The lithium titanium oxide is preferably in the form of particles. The lithium titanium oxide has a D in the range of 0.1 to 50 μm, or 0.25 to 20 μm, or 0.5 to 15 μm. 50 The lithium titanium oxide may have a particle size D of at least 0.01 μm, or at least 0.1 μm, or at least 0.5 μm. 10 The lithium titanium oxide may have a particle size D of 100 μm or less, 50 μm or less, or 25 μm or less. 90 The particle size may be D 90 By maintaining the particle size within this range, the packing properties of the titanium lithium oxide particles in the mixture with the electrode active material particles are improved.

[0082] Lithium titanium oxide is typically used in battery anodes in small particle sizes due to the material's low electronic conductivity. In contrast, the electrode active materials of the present invention typically have a higher lithium ion diffusion coefficient than lithium titanium oxide, and therefore can be used in larger particle sizes. Advantageously, in electrode compositions, lithium titanium oxide can be used in a range of particle sizes, e.g., the D of lithium titanium oxide. 50 Particle size and electrode active material D 50 The particle size of the lithium titanium oxide particles can be smaller than that of the electrode active material, such that 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, the smaller lithium titanium oxide particles can be accommodated in the voids between the larger electrode active material particles, thereby increasing the packing efficiency of the composition.

[0083] Lithium titanium oxide is 0.1 to 100 m 2 / g, or 1 to 50m 2 / g, or 3 to 30 m 2 The polymer may have a BET surface area in the range of / g.

[0084] The mass ratio of lithium titanium oxide to electrode active material can be in the range of 0.5:99.5 to 99.5:0.5, preferably in the range of 2:98 to 98:2. In one embodiment, the electrode composition includes a higher proportion of lithium titanium oxide than the electrode active material, e.g., a mass ratio of at least 2:1, at least 5:1, or at least 8:1. Advantageously, this allows for the stepwise introduction of the electrode active material into existing lithium titanium oxide-based electrodes without significant changes to manufacturing techniques, providing an efficient method for improving the performance of existing electrodes. In another embodiment, the electrode composition has a higher proportion of electrode active material than lithium titanium oxide, e.g., a mass ratio of lithium titanium oxide to electrode active material of less than 1:2, or less than 1:5, or less than 1:8. Advantageously, this allows for cost reduction of the electrode composition by replacing a portion of the electrode active material with lithium titanium oxide.

[0085] The electrode active material may be combined with niobium oxide to form an electrode composition. 12 O 29 , NbO2, NbO, and Nb2O5. Preferably, the niobium oxide is Nb2O5.

[0086] Niobium oxide is, for example, a crystalline structure of an oxide consisting of Nb and O, for example, Nb 12 O 29 , NbO2, NbO, and Nb2O5. The niobium oxide may be doped with additional cations or anions, provided that the niobium oxide corresponds to NbO2, NbO, and Nb2O5. The niobium oxide may be oxygen-deficient. The niobium oxide may include a coating, optionally selected from carbon, polymer, metal, metal oxide, semi-metal, phosphate, and fluoride.

[0087] Niobium oxide is Nb as determined by X-ray diffraction. 12 O 29, NbO2, NbO, or Nb2O5 crystal structure. For example, niobium oxide can have an orthorhombic Nb2O5 crystal structure or a monoclinic Nb2O5 crystal structure. Preferably, niobium oxide has a monoclinic Nb2O5 crystal structure, and most preferably has a H-Nb2O5 crystal structure. Further information regarding the crystal structure of Nb2O5 can be found in Griffith et al., J. Am. Chem. Soc. 138, 28, 8888-8899 (2016).

[0088] Niobium oxide can be synthesized by conventional ceramic techniques, such as solid-state or sol-gel synthesis, or it can be obtained from commercial sources.

[0089] The niobium oxide is preferably in the form of fine particles. The niobium oxide has a particle size of 0.1 to 100 μm, or 0.5 to 50 μm, or 1 to 20 μm. 50 The niobium oxide may have a particle size D of at least 0.05 μm, or at least 0.5 μm, or at least 1 μm. 10 The niobium oxide may have a particle size of 100 μm or less, 50 μm or less, or 25 μm or less. 90 It can have a particle size. 90 Maintaining the particle size in this range improves the packing of the niobium oxide particles in the mixture with the electrode active material particles.

[0090] Niobium oxide is 0.1 to 100m 2 / g, or 1 to 50m 2 / g, or 1 to 20 m 2 The polymer may have a BET surface area in the range of / g.

[0091] The mass ratio of niobium oxide to the electrode active material 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.

[0092] The present invention also provides use of the electrode active material of the present invention in the anode of a metal-ion battery, optionally wherein the metal-ion battery is 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-state-based batteries. Accordingly, the present invention also provides a method for producing a metal-ion secondary battery, comprising producing an electrode active material by the method of the first aspect of the present invention, forming an electrode comprising the electrode active material, and forming a metal-ion secondary battery comprising the electrode. Preferably, the electrode forms the anode of the metal-ion battery.

[0093] A further embodiment of the present invention is an electrochemical device comprising an anode, a cathode, and an electrolyte disposed between the anode and the cathode, wherein the anode comprises an electrode active material according to the present invention; optionally, the electrochemical device is a metal-ion battery, such as a lithium-ion battery or a sodium-ion battery. Preferably, the electrochemical device is a lithium-ion battery having a reversible anode active material specific capacity of greater than 225 mAh / g at 20 mA / g, and the battery can be charged and discharged at current densities relative to the anode active material of 200 mA / g or greater, or 1000 mA / g or greater, or 2000 mA / g or greater, or 4000 mA / g or greater, while retaining greater than 70% of the initial cell capacity at 20 mA / g. It has been found that the use of the electrode active material according to the present invention enables the fabrication of lithium-ion batteries having this combination of properties, making them particularly suitable for use in applications where high charge and discharge current densities are desired. Notably, the examples show that the electrode active material according to the present invention has excellent capacity retention at high C-rates. [Example]

[0094] Synthesis and material characterization Metal halide-modified titanium niobium oxides can be synthesized by solid-state reactions under N2 or dry air atmosphere. The precursor mixtures are shown in Tables 1 and 2. The precursors for Examples 2, 3, 4, 6, and 7 were mixed using impact milling at a blade rotation speed of 15,000 rpm for 4 minutes, followed by heating at 1100°C for 12 hours in N2. Example 1 was prepared by rolling 200 g of a precursor containing TiO2 and Nb2O5 in a ball mill at 400 rpm for 3 hours, followed by heating in air at 1200°C for 12 hours. Example 5 was prepared by impact milling at a blade rotation speed of 10,000 rpm for 2 minutes, followed by heating at 20,000 rpm for 4 minutes. The mixed powder was heated in air at 1100°C for 12 hours. Example 8 was prepared by roller ball milling in ethanol for 24 hours. The resulting mixture was then dried on a hot plate at 80°C to form a powder, which was then placed in a crucible and fired in air at 1150°C for 12 hours.

[0095] The powders of Examples 1 and 5 exhibited an off-white color, and the powder of Example 8 exhibited a white color, while the powders of Examples 2, 3, 4, 6, and 7 exhibited a blue-gray color indicating a change in the band gap of the material of the present invention, suggesting an increase in electrical conductivity. The as-synthesized powders were then deagglomerated by impact milling at a blade rotation speed of 20,000 rpm for 4 minutes to obtain fine particles.

[0096] The phase purity of the samples was analyzed using a Rigaku Miniflex powder X-ray diffractometer at a scan rate of 1° / min over the 2θ range (10-70°). This instrument has an instrument shift error of 0.1°, and the peaks in a single XRD result may shift by up to 0.2°. These or equivalent conditions can be used to determine whether a material is single-phase.

[0097] The particle size distribution was determined using a laser diffraction particle size distribution analyzer LA-960 manufactured by Horiba Co., Ltd. and a dry powder feeder. The air pressure was maintained at 0.3 MPa.

[0098] The XRD pattern of the metal halide-modified TiNb2O7 matched that of the pure TiNb2O7 found in the PDF card [01-072-0116] (Wadsley, AD, Acta Crystallogr., 14, 660, (1961)), with a difference in peak intensity at 2θ = 27.07° corresponding to the (60-1) plane (Figures 1 and 9).

[0099] Metal halide modified Ti2Nb 10 O 29 The XRD pattern of Ti2Nb 10 O 29 It is a mixture of monoclinic and orthorhombic phases. 10 O 29 The reference is from Wadsley, AD, Acta Crystallogr., 14, 664, (1961). Orthorhombic Ti2Nb 10 O 29 The reference is from RB von Dreele, AK Cheetham, Proceedings of the Royal Society London, Series A, 338, 311, (1974) (Figure 2).

[0100] Based on the above reference pattern, Rietveld refinement of all examples was performed using HighScore Plus. The goodness of fit of all refinements performed is less than 10.

[0101] [Table 1] [Table 2] [Table 3]

[0102] Electrochemical characterization The charge rate of a Li-ion battery is typically expressed as a "C-rate." A 1C charge rate refers to a charging current that fully charges the cell in 1 hour, while a 10C charge means that the cell is fully charged in 1 / 10 of an hour (6 minutes). The C-rate here is defined as the reversible capacity of the anode within the voltage limits imposed by the second delithiation cycle. That is, for an anode exhibiting a capacity of 1.0 mAh within the voltage limits of 1.1 to 3.0 V, a 1C rate corresponds to an applied current of 1.0 mA. For the typical materials described herein, this corresponds to approximately 225 mA / g of active material.

[0103] Electrochemical testing was performed in analytical half-coin cells (CR2032 size). Half-coin testing involves comparing electrodes to Li metal electrodes to evaluate the fundamental performance of the active material. In the following examples, the active material composition to be tested was combined with N-methylpyrrolidone (NMP), carbon black (Super P) acting as a conductive additive, and poly(vinyl difluoride) (PVDF) binder and mixed in a laboratory-scale centrifugal planetary mixer to form a slurry. The non-NMP composition of the slurry was 92 wt% active material, 5 wt% conductive additive, and 3 wt% binder. This slurry was then doctor-blade coated onto an Al foil current collector at 67-73 gm. -2 The electrode was coated to the desired loading amount of 2.6 to 2.9 g cm and then heated and dried. -3 The electrodes were then calendered to a density of 1000 kJ / cm², achieving a porosity of 30-35%. The electrodes were die-cut to the desired size and combined with a separator (Celgard porous PP / PE), Li metal, and electrolyte (EC / DEC with 1.3 M LiPF₆) in a steel coin cell casing, which was then sealed under pressure. They were then subjected to two cycles of lithiation and delithiation between 1.1 and 3.0 V at low current (C / 10) at 25°C. The cell's performance was then tested at increasing currents. During these tests, the cells were asymmetrically cycled at 25°C, with a slow lithiation rate (C / 5) followed by increasing delithiation rates (e.g., 1C, 5C, and 10C) to test capacity retention at various currents.

[0104] The data are averages of 3-5 cells prepared from the same electrode coating, and the errors are shown from the standard deviation. Therefore, this data is a robust study showing the improvement achieved by the material according to the present invention compared to previous materials. These data are presented in Tables 4-6.

[0105] Both Cu and Al current collector foils were coated with uniform, smooth coatings, free of visible defects and agglomerates, prepared using a centrifugal planetary mixer as described above for these samples, with compositions up to 94 wt% active material, 4 wt% conductive additive, and 2 wt% binder. These were prepared with both PVDF (i.e., NMP-based) and CMC:SBR-based (i.e., water-based) binder systems. Coatings were prepared at 80°C for PVDF and 50°C for CMC:SBR, with concentrations of 1.0–5.0 mAhcm. -2 The materials can be calendered to 30-40% porosity at loadings of 1000 MPa, which is important for demonstrating the viability of these materials in both high-energy and high-power applications involving highly active materials.

[0106] [Table 4] [Table 5] [Table 6] [Table 7] [Table 8] [Table 9]

[0107] solid phase NMR Fluorine-19 NMR spectra were measured at 379.60 MHz using a Bruker Advance III HD spectrometer and a 3.2 mm magic-angle spinning probe (MAS probe). Spectra were acquired using direct polarization. A recycle delay of 2 seconds was used. Samples were acquired under magic-angle spinning (MAS) conditions at a spinning rate of 20 kHz. Spectral calibration was performed using a CFCl3 reference standard, setting the signal of a 50% CF3COOH sample in H2O used as an external standard to -76.54 ppm.

[0108] Consideration Compared with the comparative examples, the titanium niobium oxide modified with metal halides according to the present invention showed significant improvements in electrochemical properties.

[0109] Example 1* is a comparative example where no metal halide was used and corresponds to TiNb2O7. Example 8* is a comparative example where a metal halide was used in the precursor mixture, but the atomic ratio of cations:anions in the precursor mixture corresponds to that of TiNb2O7. Examples 2, 3, and 4 are comparative examples where a metal halide was used in the precursor mixture, but the atomic ratio of cations:anions in the precursor mixture corresponds to that of TiNb2O7, Ti2Nb 10 O 29 , TiNb 14 O 37 , or TiNb 24 O 62 The atomic ratio of cations to anions does not correspond to the atomic ratio of the cations to anions. Compared with Examples 1* and 8*, Examples 2, 3, and 4 showed higher first cycle coulombic efficiencies at 5C and 10C, as well as higher delithiation capacities and capacity retention. This improved rate performance can be explained by improved electrical conductivity. This improvement in conductivity is due to the incorporation of halide anions and metal cations into the crystal structure and the shift of the Fermi level toward the conduction band due to the compositional deviation from the stoichiometric ratio. This is consistent with other titanium niobium oxides, e.g., Ti2Nb 10 O 29 and TiNb 14 O37 has a similar block structure, so it can be generalized.

[0110] Furthermore, the incorporation of metal halides can significantly reduce the reaction energy: non-nanosized TiNb2O7 can only be obtained at 1200 °C in a solid-state reaction, but the incorporation of metal halides can reduce the reaction temperature to 1100 °C, providing economic advantages in industrial-scale processes.

[0111] Solid-state NMR confirmed the chemical environment of F in Example 6. A signal corresponding to an F atom located in a bridging position between two Al atoms and bonded to Al in an octahedral environment was observed at −161.6 ppm, indicating that Al and F from the metal halides used in the precursor mixture entered the Wadsley-Roth crystal structure.

[0112] synthetic research Synthesis studies were conducted to assess the importance of metal halides and non-stoichiometry in the precursor mixture in forming the desired crystal structure. Comparatives A, B, C, and E were synthesized under identical conditions: impact milling for 4 minutes at a blade speed of 15,000 rpm, followed by heating in N2 at 1100 °C for 12 hours. Comparative D was synthesized under the same milling conditions as above, but was heated in air at 1150 °C for 12 hours. Comparative F was synthesized under the same milling conditions as above, but was heated in N2 at 1150 °C for 12 hours.

[0113] Comparison A The precursor mixture was Nb2O5:TiO2 with a molar ratio of 1:0.9. The XRD pattern of the obtained material showed peaks due to the TiNb2O7 crystal structure, but the Ti2Nb 10 O 29The peaks were accompanied by additional peaks due to the presence of NbO, TiO, AlF, and AlF (see arrows in Figure 3). In contrast, Example 4 (NbO:TiO:AlF = 1:0.9:0.05) was able to form single-phase TiNbO. This indicates that single-phase TiNbO cannot be produced from precursor mixtures with non-stoichiometric ratios of Nb / Ti > 2 without the use of metal halides.

[0114] Comparison B The precursor mixture was Nb2O5:TiO2:aluminum oxalate in a molar ratio of 1:0.9:0.05. The XRD pattern of the resulting material showed Ti2Nb 10 O 29 The high levels of TiO2 and TiNbO2 in the SiO2 solution resulted in broad peaks (Figure 4). In contrast, Example 4 (Nb2O5:TiO2:AlF3 = 1:0.9:0.05) was able to form single-phase TiNb2O7. This indicates that while the metal halides used in this invention lead to the formation of a single phase, substitution with an alternative metal precursor (aluminum oxalate in this study) does not result in a single phase.

[0115] Comparison C The precursor mixture was Nb2O5:TiO2:AlF3 with a molar ratio of 1:2:0.1. The XRD pattern of the resulting material showed peaks due to TiNb2O7, along with additional peaks due to TiO2 (see arrows in Figure 5). No peaks due to AlF3 were observed. This indicates that the formation of a single phase is not possible even with a Nb:Ti ratio of 2 in the presence of metal halides. It is believed that AlF3 reacted preferentially with Nb2O5, resulting in the residual TiO2 in the synthesized material.

[0116] Comparison D The precursor mixture was Nb2O5:TiO2:ZnF2 with a molar ratio of 1:0.9:0.1 (i.e., corresponding to the stoichiometric ratio of TiNb2O7). The XRD pattern of the obtained material showed peaks attributable to the TiNb2O7 crystal structure, but not Ti2Nb 10 O 29The results also showed additional peaks due to the stoichiometric substitution of ZnF for TiO, indicating that a single phase could not be formed even at a higher temperature of 1150 °C. In contrast, Example 3 (NbO:TiO:ZnF = 1:0.94:0.01) was able to form single-phase TiNbO. This indicates that the non-stoichiometric precursor mixture of the present invention is necessary for single-phase formation.

[0117] Comparison E The precursor mixture was Nb2O5:TiO2:AlF3 with a molar ratio of 0.9:1.1:0.1 (i.e., corresponding to the stoichiometric ratio of TiNb2O7). The XRD pattern of the resulting material showed peaks attributed to TiNb2O7, along with additional peaks attributed to TiO2 (see arrows in Figure 7). Since Al is a 3+ cation, Nb and Ti were adjusted to achieve the stoichiometric composition. In contrast, Example 4 (Nb2O5:TiO2:AlF3 = 1:0.9:0.05) was able to form single-phase TiNb2O7. This demonstrates that the non-stoichiometric precursor mixture according to the present invention is necessary for single-phase formation.

[0118] Comparison F The precursor mixture was Nb2O5:TiO2:NH4F in a molar ratio of 1:0.95:0.1 (i.e., not corresponding to the stoichiometry of TiNb2O7, but without the use of metal halides). The XRD patterns of the resulting materials show high levels of Ti2Nb, even at the higher synthesis temperature (1150 °C). 10 O 29 Impurities were observed (see arrows in Figure 8). In contrast, Examples 3 and 4 were able to form single-phase TiNb2O7 at 1100 °C. This indicates that metal halides must be present in the precursor mixture to form single-phase materials. Simultaneous substitution of anions and cations by metal halides leads to single-phase formation.

Claims

1. 1. A method for producing an electrode active material, the method comprising: treating a precursor mixture comprising a niobium precursor, a titanium precursor, and a metal halide to form the electrode active material; the atomic ratio of Nb:Ti in the precursor mixture is >2; The atomic ratio of cations to anions in the precursor mixture was TiNb ２ O ７ , Ti ２ Nb １０ O ２９ , TiNb １４ O ３７ , or TiNb ２４ O ６２ does not correspond to the atomic ratio of cations to anions, The electrode active material is TiNb ２ O ７ , Ti ２ Nb １０ O ２９ , TiNb １４ O ３７ , and / or TiNb ２４ O ６２ The method according to claim 1, wherein the compound has a crystal structure represented by the formula:

2. The electrode active material is TiNb ２ O ７ and optionally, an X-ray diffraction pattern of the electrode active material is ２ O ７ 2. The method of claim 1, wherein the crystal structure has a peak at 2θ=26.0±0.2 assigned to the crystal structure of

3. 3. The method of claim 2, wherein the crystalline structure is monoclinic and optionally the unit cell parameters are a between 20.38 and 20.45 Å, b between 3.80 and 3.82 Å, c between 11.90 and 11.94 Å, α=γ=90°, and β between 120.10 and 120.30°.

4. The electrode active material is Ti ２ Nb １０ O ２９ and optionally, an X-ray diffraction pattern of the electrode active material is ２ Nb １０ O ２９ 2. The method of claim 1, wherein the compound has a peak at 2θ=24.9±0.2 assigned to a crystalline structure of

5. 5. The method of claim 4, wherein the crystal structure is orthorhombic and optionally the unit cell parameters are a between 28.30 and 28.70 Å, b between 3.78 and 3.83 Å, c between 20.35 and 20.70 Å, and α=β=γ=90°.

6. 5. The method of claim 4, wherein the crystal structure is monoclinic, and optionally the unit cell parameters of the electrode active material are a between 20.54 and 20.57 Å, b between 3.80 and 3.82 Å, c between 15.52 and 15.55 Å, α=γ=90°, and β between 113.00 and 113.70°.

7. The electrode active material is TiNb １４ O ３７ and optionally, an X-ray diffraction pattern of the electrode active material is １４ O ３７ 2. The method of claim 1, wherein the compound has a peak at 2θ=23.8±0.2 assigned to a crystalline structure of

8. 8. The method of claim 7, wherein the crystal structure is monoclinic, and optionally the unit cell parameters of the electrode active material are a between 20.00 and 21.60 Å, b between 3.81 and 3.83 Å, c between 29.82 and 30.15 Å, α=γ=90°, and β between 94.50 and 95.50°.

9. The electrode active material is TiNb ２４ O ６２ and optionally, an X-ray diffraction pattern of the electrode active material is ２４ O ６２ 2. The method of claim 1, wherein the compound has a peak at 2θ=24.7±0.2 assigned to a crystalline structure of

10. 10. The method of claim 9, wherein the crystalline structure is monoclinic and optionally the unit cell parameters are a between 29.59 and 29.98 Å, b between 3.80 and 3.84 Å, c between 20.91 and 21.29 Å, α=γ=90°, and β between 94.2 and 95.6°.

11. The electrode active material is TiNb ２ O ７ and / or Ti ２ Nb １０ O ２９ or the electrode active material has a crystal structure of TiNb ２ O ７ 10. The method of any preceding claim, wherein the crystalline structure of

12. The electrode active material is TiNb ２ O ７ , Ti ２ Nb １０ O ２９ , TiNb １４ O ３７ , or TiNb ２４ O ６２ or TiNb ２ O ７ Or Ti ２ Nb １０ O ２９ or TiNb ２ O ７ 10. The method of claim 9, wherein the crystalline structure is a single phase crystalline structure consisting of:

13. The niobium precursor is Nb ２ O ５ , Nb(OH) ５ , niobic acid, NbO, ammonium niobium oxalate, NbO ２ , NbO ２ F, Nb ３ O ７ F, niobium chloride, niobium fluoride, niobium bromide, and mixtures thereof, or the niobium precursor is a niobium oxide, or the niobium precursor is Nb ２ O ５ 10. A method according to any preceding claim, wherein:

14. The titanium precursor is TiO ２ , titanium chloride, titanium fluoride, titanium bromide, titanium oxalate, ammonium titanyl oxalate or ammonium titanyl nitrate, titanyl nitrate, titanyl sulfate, titanyl hydroxide, and ammonium bis(oxalate)oxotitanate, and mixtures thereof, or the titanium precursor is selected from TiO ２ 10. A method according to any preceding claim, wherein:

15. 10. The method of any of the preceding claims, wherein the oxidation state of the metal of the metal halide is +4 or less or +3 or less.

16. 10. A method according to any preceding claim, wherein the metal of the metal halide is Mg, Al, Zn, Cr, Ni, Nb, Cu, Mn, Fe, Zr, Ga, Ge, Sn, and mixtures thereof, or Al, Zn, Cr, Fe, Zr, Nb, and mixtures thereof, or Al, Zn, and mixtures thereof.

17. 10. The method of any preceding claim, wherein the metal halide is a metal fluoride, a metal chloride, or a metal bromide, optionally wherein the metal halide is a metal fluoride.

18. 10. The method of any preceding claim, wherein the metal of the metal halide is neither Nb nor Ti.

19. 10. The method of any preceding claim, wherein the niobium precursor and the titanium precursor are not metal halides.

20. The metal fluoride is ZnF ２ and / or AlF ３ 10. A method according to any preceding claim, wherein:

21. The niobium precursor, the titanium precursor, and the metal halide are in particulate form, and optionally the niobium precursor, the titanium precursor, and the metal halide have a D of <20 μm. ５０ 10. The method of any preceding claim, wherein the particle size is

22. 10. The method of any of the preceding claims, wherein the atomic ratio of titanium in the precursor mixture to the metal of the metal precursor is <0.

3.

23. 10. A method according to any preceding claim, wherein the metal halide is present in an amount such that the metal of the metal halide is ≥ 0.1 at%, 0.2-5 at%, 0.3-3 at%, or ≤ 6 at%, relative to the amount of Nb and Ti in the precursor mixture.

24. The electrode active material is particulate, and optionally the electrode active material has a D in the range of 0.1 to 100 μm, or 0.5 to 50 μm, or 1 to 20 μm. ５０ 10. The method of any preceding claim, wherein the particle size is

25. The electrode active material has a D of at least 0.05 μm, or at least 0.1 μm, or at least 0.5 μm, or at least 1 μm. １０ 10. The method of any preceding claim, wherein the particle size is

26. The electrode active material has a D of 200 μm or less, or 100 μm or less, or 50 μm or less, or 20 μm or less. ９０ 10. The method of any preceding claim, wherein the particle size is

27. The electrode active material has a thickness of 0.1 to 100 m ２ / g, or 0.25 to 50 m ２ / g, or 0.5 to 20 m ２ 10. The method of any preceding claim, wherein the surface has a BET surface area in the range of 1 / g.

28. 10. The method of any preceding claim, wherein the electrode active material is coated with carbon.

29. 10. The method of any preceding claim, wherein the electrode active material comprises a protective coating, optionally the protective coating comprising niobium oxide, aluminum oxide, zirconium oxide, organic or inorganic fluorides, organic or inorganic phosphates, titanium oxide, lithiated versions thereof, and mixtures thereof.

30. 10. The method of any preceding claim, wherein processing the precursor mixture comprises solid state synthesis, hydrothermal or microwave hydrothermal synthesis, solvothermal or microwave solvothermal synthesis, co-precipitation synthesis, spark or microwave plasma synthesis, combustion synthesis, electrospinning, spray pyrolysis, chemical vapor deposition, and / or atomic layer deposition, optionally wherein processing the precursor mixture comprises solid state synthesis.

31. 10. The method of any preceding claim, wherein treating the precursor mixture comprises heating the precursor mixture.

32. 32. The method of claim 31, wherein the heating is carried out at 400 to 1350°C, or 800 to 1250°C, or 1000 to 1125°C.

33. 33. The method of claim 31 or 32, wherein the heating is carried out for 1 to 48 hours, or 2 to 24 hours, or 3 to 18 hours.

34. A method according to any of claims 31 to 33, wherein the heating is carried out in a gas atmosphere, optionally under nitrogen or air, optionally in the absence of water.

35. An electrode active material obtained by the method according to any one of claims 1 to 34.

36. 36. A composition comprising the electrode active material of claim 35 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 electrode active material, and mixtures thereof.

37. 36. An electrode comprising the electrode active material of claim 35, optionally wherein the electrode active material is deposited on a current collector.

38. 38. The electrode of claim 37, wherein the electrode active material of claim 35 forms at least 5 wt%, at least 10 wt%, or at least 50 wt% of the total electrode active material in the electrode, or wherein the electrode active material of claim 35 is the only electrode active material in the electrode.

39. 40. The electrode of claim 38, further comprising at least one other component selected from a binder, a conductive additive, a different electrode active material, and mixtures thereof.

40. 40. The electrode of claim 39, wherein the different electrode active materials are selected from lithium titanium oxide, titanium niobium oxide, niobium oxide, different electrode active materials obtainable by the method of any of claims 1 to 35, graphite, hard carbon, soft carbon, silicon, doped and / or carbon-coated versions thereof, and mixtures thereof.

41. 41. The electrode of any of claims 37 to 40, wherein the electrode active material is present in the electrode composition at 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.

42. 42. A metal-ion battery comprising the electrode of any one of claims 37 to 41, optionally wherein the metal-ion battery is a lithium-ion battery or a sodium-ion battery, and the electrode forms the anode.

43. 43. The metal-ion battery of claim 42, wherein the lithium-ion battery has an anode active material with a reversible specific capacity greater than 225 mAh / g at 20 mA / g, wherein the battery can be charged and discharged at current densities for the anode active material of 200 mA / g or greater, or 1000 mA / g or greater, or 2000 mA / g or greater, or 4000 mA / g or greater, while retaining greater than 70% of the initial cell capacity at 20 mA / g.

44. 36. Use of the electrode active material of claim 35 in a metal ion battery, optionally in a lithium ion battery or a sodium ion battery.

Images