Active material, electrode mixture containing the active material, and battery

Abstract

The active substance comprises compound A and compound B. Compound A contains Li, M (M represents one or more elements selected from Ni, Co, and Mn), and O. Compound B contains Li, Nb, and O. In the Raman spectrum obtained by Raman spectrometry, the area of ​​the peak originating from compound B is denoted as S. PB And will be at 540cm ‑1 Above and 650cm ‑1 The area of ​​the peak originating from the aforementioned compound A observed in the following range is denoted as S. PA At that time, S PB With S PA The ratio, i.e., S PB / S PA The value satisfies 0 PB / S PA ≤1.2.​

Description

Technical Field

[0001] This invention relates to active materials for batteries. Additionally, this invention relates to electrode compounds containing the active material and batteries. Background Technology

[0002] Lithium-ion rechargeable batteries are widely used as power sources for portable electronic devices such as laptops and mobile phones due to their high energy density and ease of miniaturization and weight reduction. Furthermore, high-output, high-capacity lithium-ion rechargeable batteries for use in electric vehicles and hybrid electric vehicles are currently under development.

[0003] Currently, many lithium-ion rechargeable batteries use electrolytes containing flammable organic solvents. Therefore, when the battery reaches high temperatures due to short circuits or other reasons, there is a risk of electrolyte ignition. In contrast, solid-state batteries, which use solid electrolytes instead of liquid electrolytes and do not contain flammable organic solvents, have a lower risk of ignition. Therefore, they are expected to be practically used as batteries that combine safety and high energy density.

[0004] Sulfide solid electrolytes have been studied as one type of solid electrolyte used in solid-state batteries. However, solid-state batteries containing sulfide solid electrolytes have the following problem: during charging and discharging, the interfacial resistance between the electrode active material and the sulfide solid electrolyte increases, restricting the movement of lithium ions. This can be attributed to the formation of a resistive layer at the interface between the electrode active material and the sulfide solid electrolyte due to their reaction. To address this problem, for example, Patent Document 1 attempts to suppress the increase in interfacial resistance by coating the surface of the positive electrode active material with a specific compound.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: US2018 / 219229A1 Summary of the Invention

[0008] In the past, various technologies have been proposed for active materials. On the other hand, in order to further improve battery performance, there is a need for active materials that can reduce the interfacial resistance with solid electrolytes such as sulfide solid electrolytes.

[0009] In view of the aforementioned problems, the main objective of this invention is to provide an active material that can reduce the interfacial resistance with a solid electrolyte and improve battery performance.

[0010] This invention provides an active substance comprising compound A and compound B.

[0011] The compound A contains lithium (Li), M (where M represents one or more elements selected from nickel (Ni), cobalt (Co), and manganese (Mn),) and oxygen (O).

[0012] Compound B contains lithium (Li), niobium (Nb), and oxygen (O).

[0013] In the Raman spectrum obtained by Raman spectroscopy, the area of ​​the peak originating from the aforementioned compound B is denoted as S. PB And will be at 540cm -1 Above and 650cm -1 The area of ​​the peak originating from the aforementioned compound A observed in the following range is denoted as S. PA At that time, S PB With S PA The ratio, i.e., S PB / S PA The value satisfies 0 PB / S PA ≤1.2.

[0014] In addition, the present invention provides an electrode mixture comprising the aforementioned active substance and a solid electrolyte.

[0015] Furthermore, the present invention provides a battery comprising a positive electrode layer containing a positive electrode active material, a negative electrode layer containing a negative electrode active material, and a solid electrolyte layer containing a solid electrolyte, wherein the positive electrode active material is the aforementioned active material. Attached Figure Description

[0016] Figure 1 This is a graph showing the Raman spectrum of the active substance obtained in Example 4 and the results of peak separation.

[0017] Figure 2 Images (a) to (c) are scanning transmission electron microscope images of the active substances obtained in Examples 2 to 4, respectively.

[0018] Figure 3 This is a diagram showing the Raman spectra of the active substances obtained in Examples 1 to 5 and Comparative Example 1. Detailed Implementation

[0019] The present invention will now be described based on its preferred embodiments. The present invention relates to active materials used in batteries, electrode mixtures containing the active materials, and batteries. These will be described separately below.

[0020] A. Active substances

[0021] ​The active substance of the present invention comprises two compounds, compound A and compound B, which are specific compounds. It should be noted that the active substance of the present invention only needs to contain compound A and compound B, and may contain other compounds as needed.

[0022] The following is a description of each compound.

[0023] A-1. Compound A

[0024] Compound A contains lithium (Li), element M (M represents one or more elements selected from nickel (Ni), cobalt (Co), and manganese (Mn), and element O. In other words, compound A is composed of a lithium transition metal complex oxide. Examples of lithium transition metal complex oxides used as compound A include, for example, any one or a combination of lithium-containing complex oxides with a layered rock salt structure as shown in LiMO2 (M is defined as described above) and lithium-containing complex oxides with a spinel structure as shown in LiM2O4 (M is defined as described above). However, it is not limited to these.

[0025] In particular, compound A is preferably a lithium-containing composite oxide with the spinel-type structure described above. It should be noted that, hereinafter, the lithium-containing composite oxide with the spinel-type structure is sometimes simply referred to as "spinel-type composite oxide." When the active material of the present invention containing this compound A is used as a positive electrode active material, it has an operating potential of 4.5V or higher based on a Li metal reference potentiometer. "Having an operating potential of 4.5V or higher based on a Li metal reference potentiometer" means that it is not necessary to have only an operating potential of 4.5V or higher as a plateau region, but also includes cases where an operating potential of 4.5V or higher is partially present. Therefore, the present invention is not limited to a positive electrode active material composed only of a 5V-level positive electrode active material having an operating potential of 4.5V or higher as a plateau region. For example, the active material of the present invention may include a positive electrode active material having an operating potential of less than 4.5V as a plateau region.

[0026] When compound A is a spinel-type composite oxide, compound A preferably contains at least the element Mn, and more preferably contains the elements Li, Mn, and O, as well as one or more other elements. Here, "one or more other elements" is preferably a metallic element M1 selected from the group consisting of Ni and Co.

[0027] When compound A is a spinel-type composite oxide, compound A preferably also contains Li, Mn, and O, as well as two or more other elements. At least one of the "two or more other elements" is preferably a metallic element M1 selected from the group consisting of Ni and Co, and the other element is preferably a metallic element M2 comprising one or more combinations of the group consisting of Na, Mg, Al, P, K, Ca, Ti, V, Cr, Fe, Co, Cu, Ga, Y, Zr, Nb, Mo, In, Ta, W, Re, and Ce.

[0028] As a particularly preferred example of compound A, examples include those containing LiMn2O 4-δ A spinel-type lithium-manganese composite oxide with a crystal structure formed by replacing some of the Mn sites with Li, metal element M1 and other metal elements M2.

[0029] Metal element M1 is a substitutional element that primarily contributes to exhibiting an operating potential of 4.5V or higher on a Li metal reference potentiometer, and as described above, it preferably includes at least one of Ni and Co.

[0030] On the other hand, metallic element M2 is a substitution element that primarily helps stabilize the crystal structure and improve properties. Examples of substitution elements that help improve capacity retention include Na, Mg, Al, P, K, Ca, Ti, V, Cr, Fe, Co, Cu, Ga, Y, Zr, Nb, Mo, In, Ta, W, Re, and Ce, among which Na, Mg, Al, P, K, Ca, Ti, Cr, Fe, Co, Cu, Ga, Y, Zr, Nb, Mo, Ta, and W are preferred. Metallic element M2 can be one or a combination of two or more of the above elements. Metallic element M2 preferably contains at least one of the above elements, but may contain metallic elements other than those mentioned above. The metallic element M2 included in the structure is a different type of element than metallic element M1.

[0031] As an example of the composition of compound A, the inclusion formula (1) can be listed: Li x (M1 y M2 z Mn 3-x-y-z )O 4-δ The composition of the spinel-type lithium-manganese composite oxide shown is as described above. Metal elements M1 and M2 in formula (1) are as described above.

[0032] In the aforementioned formula (1), "x" is preferably 1.00 or more and 1.20 or less, more preferably 1.01 or more or 1.10 or less, and more preferably 1.02 or more or 1.08 or less. "y," representing the content of metal element M1, is preferably 0.20 or more and 1.20 or less, more preferably 0.30 or more or 1.10 or less, and more preferably 0.35 or more or 1.05 or less. "z," representing the content of metal element M2, is preferably 0.001 or more and 0.400 or less, more preferably 0.002 or more or 0.400 or less, more preferably 0.005 or more or 0.30 or less, and more preferably 0.10 or more. In particular, by setting it to 0.10 or more, the cycle characteristics can be improved more effectively.

[0033] Other examples of the composition of compound A include formula (2): general formula [Li x (Ni y M3 z Mn 3-x-y-z )O 4-δ The spinel-type lithium-manganese composite oxide shown in [Formula (2)]. In Formula (2), "x" is preferably 1.00 or more and 1.20 or less, more preferably 1.01 or more or 1.10 or less, and more preferably 1.02 or more or 1.08 or less. In Formula (2), "y" is preferably 0.20 or more and 0.70 or less, more preferably 0.30 or more or 0.60 or less, and more preferably 0.35 or more or 0.55 or less.

[0034] In the aforementioned formula (2), the metallic element M3 can be, for example, Na, Mg, Al, P, K, Ca, Ti, V, Cr, Fe, Co, Cu, Ga, Y, Zr, Nb, Mo, In, Ta, W, Re, and Ce, among which Na, Mg, Al, P, K, Ca, Ti, Cr, Fe, Co, Cu, Ga, Y, Zr, Nb, Mo, Ta, and W are preferred. The metallic element M3 can be one or a combination of two or more of the above elements. The "z" representing the molar ratio of the metallic element M3 is preferably greater than 0 and less than 0.5, more preferably greater than 0.01 or less than 0.45, more preferably more than 0.05 or less than 0.40, and even more preferably more than 0.10 or less than 0.35. In particular, by setting it to 0.10 or more, the cycle characteristics can be improved more effectively.

[0035] It should be noted that "4-δ" in the aforementioned formulas (1) and (2) optionally includes oxygen defects. In addition, a part of oxygen is optionally substituted by fluorine or other elements. At this time, δ is preferably 0 or more and 0.2 or less, more preferably 0.1 or less, and still more preferably 0.05 or less.

[0036] It should be noted that, for example, when fitting with the crystal structure model of a cubic crystal of space group Fd-3m (Origin Choice 2), it can be confirmed that compound A has a spinel structure by the ranges of Rwp and S representing the degree of agreement between the observed intensity and the calculated intensity being Rwp < 10 or S < 2.5.

[0037] A-2. Compound B

[0038] Compound B constituting the active material of the present invention contains lithium (Li) element, niobium (Nb) element, and oxygen (O) element. The composition of each element in compound B can be represented by, for example, Li x NbO y wherein x and y can take any values within the range that conforms to the element valences. Among them, a composition (x > 1) containing more than 1 mole of Li relative to 1 mole of Nb is particularly preferred. Thereby, the formation of a compound of Nb and O can be suppressed, and the interfacial resistance with the solid electrolyte can be effectively reduced. Specifically, regarding the values of x and y, x is preferably 1 < x ≤ 2, and y is preferably 3 ≤ y ≤ 8.

[0039] When compound B is represented by Li x NbO y as a method to satisfy x > 1, a method can be cited in which the blending amount of the lithium raw material relative to the niobium raw material is excessive compared to the stoichiometric composition ratio of the composition expected to be formed, such as LiNbO3. At this time, when only lithium is simply added in excess, there is a tendency that lithium carbonate is formed on the surface of the active material due to the excessive lithium, which will become a resistance and instead deteriorate the rate performance and cycle performance. Therefore, considering the formation of an undesired compound, that is, lithium carbonate, it is preferable to adjust the blending amount of the niobium raw material and the lithium raw material so that Li x NbO y becomes a specified composition.

[0040] Regarding the proportion of compound B in the active material, when converted to the amount of niobium (Nb) contained in compound B, it is preferably 0.01% by mass or more and 20% by mass or less, more preferably 0.1% by mass or more and 15% by mass or less, and even more preferably 0.5% by mass or more and 10% by mass or less. By including niobium (Nb) in the active material within this range, as described later, the formation of a high-resistivity region between the active material and the solid electrolyte can be effectively suppressed, and the interfacial resistance between the active material and the solid electrolyte can be reduced. The amount of niobium (Nb) contained in the active material can be determined using ICP emission spectroscopy with a solution containing the active material as the target.

[0041] A-3. Raman spectroscopy

[0042] Regarding the active material of the present invention comprising the above-mentioned compound A and compound B, when measured by Raman spectrometry, peaks originating from the Raman spectrum of compound A and peaks originating from the Raman spectrum of compound B were observed.

[0043] Specifically, in the Raman spectra obtained by Raman spectrometry, the results for compound A vary depending on its composition, but all have a Raman shift of 540 cm⁻¹. -1 Above and 650cm -1 One or more peaks originating from compound A were observed within the following wavenumber range. These peaks were observed regardless of whether compound A had a layered rock salt or spinel structure. Furthermore, the peaks in this wavenumber range included both peaks originating from the one-to-one vibrations of the transition elements and oxygen elements constituting compound A (e.g., peaks originating from MnO, CoO, NiO) and peaks originating from the overall vibrations of the transition elements and all oxygen elements surrounding those transition elements (e.g., peaks originating from MnO6).

[0044] On the other hand, regarding compound B, it also varies depending on its composition, but for example, at 850 cm⁻¹ -1 Above and 950cm -1One or more peaks originating from compound B were observed within the following range. It should be noted that, for example, the Raman spectra of Li3NbO4, LiNbO3, and LiNb3O8 are disclosed in "JOURNAL OF PHYSICS: CONDENSED MATTER J.Phys.: Condens. Matter 25(2013)205901(8pp) 'Identification of LiNbO3, LiNb3O8 and Li3NbO4 phases in thin films synthesized with different deposition techniques by means of XRD and Raman spectroscopy', but none of them show the peak positions and peak area ratios specified in this invention. Therefore, based on the Raman spectra specified in this invention, compound B can be said to possess a novel structure.

[0045] The area of ​​the peak originating from compound B is denoted as S. PB and the above at 540cm -1 Above and 650cm -1 The area of ​​the peak observed in the Raman spectrum originating from compound A within the following range is denoted as S. PA In the present invention, S is an active substance. PB With S PA The ratio, i.e., S PB / S PA The value preferably satisfies 0 PB / S PA ≤1.2. Raman spectroscopy is a spectrum obtained by measuring the Raman scattered light of incident light. Therefore, the Raman spectrum obtained using the active material of this invention as the measurement object reflects the surface state of the active material (not the outermost surface, but the surface layer). It should be noted that the presence of compound B in the surface layer can be confirmed by scanning transmission electron microscopy (hereinafter also referred to as "STEM"). Furthermore, S PB / S PA ​A value (hereinafter also referred to as the "Raman ratio") within a specific range means that the ratio of compound A to compound B in the surface layer of the active material is within a specific range. According to the inventors' findings, the active material of the present invention, in which compound A and compound B exist in the surface layer at a specific Raman ratio, can suppress the formation of a high-resistivity region at the interface between the active material and a solid electrolyte, such as a sulfide solid electrolyte. As a result, the interfacial resistance between the active material and the solid electrolyte decreases, lithium ion movement becomes smoother, and battery capacity increases. This advantage becomes more pronounced when compound A constituting the active material has a spinel-type structure at the 5V level.

[0046] From the viewpoint of further suppressing the formation of the aforementioned high-resistivity region and further improving battery capacity, the Raman spectral ratio is more preferably 0.01 or higher and 0.50 or lower, and more preferably 0.02 or higher and 0.30 or lower.

[0047] As mentioned above, the peak area S used to calculate the Raman spectral ratio PA From 540cm -1 Above and 650cm -1 The peaks observed in the Raman spectrum of compound A within the following wavenumber range are used for calculation. Sometimes multiple peaks are observed within this wavenumber range. In this case, a mathematical operation is performed to separate overlapping peaks into individual peaks, and the sum of the areas of the separated peaks is taken as the peak area S. PA In this case, the peaks whose apexes belong to the aforementioned wavenumber range are considered as the target, and the area of ​​the peaks is calculated.

[0048] On the other hand, when determining the area S of the peak originating from compound B... PB Within the wavenumber range, it is common to observe only one peak. When more than two overlapping peaks are observed, the peak area S is more relevant. PA The same peak separation operation is performed in the same case, and the sum of the areas of the separated peaks is taken as the peak area S. PB .

[0049] In the active material of the present invention, the presence of compounds A and B is not particularly limited as long as the Raman spectral ratio satisfies the above-mentioned range. For example, particles of compound A and particles of compound B may be mixed in the active material. Alternatively, particles of compound B may be present on the surface of particles of compound A. In particular, from the viewpoint that the Raman spectral ratio can be easily set to the above-mentioned range, the active material preferably has a structure in which compound B is present on at least a portion of the surface of the core material containing compound A.

[0050] When the active substance has a structure in which compound B is present on at least a portion of the surface of a core material containing compound A, compound B can uniformly cover the surface of the core material, or it can partially cover the surface of the core material with a portion of the core material exposed. That is, compound B preferably covers the surface of the core material containing compound A to a degree that enables the effects of the present invention to be obtained. When compound B is present on the surface of the core material containing compound A with a portion of the core material exposed, compound B can be dispersed in the "sea area" formed by the surface of the core material containing compound A in the form of "island areas" formed by compound B.

[0051] The shape and size of the aforementioned core material are not particularly limited as long as they are suitable for use as active materials and can be applied to batteries. The shape of the core material is preferably, for example, granular. The thickness of the covering portion can be appropriately adjusted according to the material of the covering portion, preferably to the extent that the effects of the present invention are achieved. The thickness of the covering portion can be, for example, 1 nm or more and 1 μm or less. It should be noted that the thickness of the covering portion can be measured by, for example, observation images from a high-angle scattering annular dark-field scanning transmission microscope (HAADF-STEM), and can be determined from the average value (n≥10). The presence rate of the covering portion on the surface of the core material, in other words, the coverage rate, can be appropriately adjusted according to the material of the covering portion, preferably to the extent that the effects of the present invention are achieved. The aforementioned presence rate is preferably, for example, 30% or more, more preferably 50% or more, particularly preferably 80% or more, and even more preferably 90% or more. The aforementioned presence rate can be determined by, for example, X-ray photoelectron spectroscopy (XPS).

[0052] When the active material of the present invention has a core material and a covering portion, the core material preferably contains compound A, and the covering portion preferably contains compound B. It should be noted that, of all compounds A contained in the active material, the proportion of compound A contained in the core material can be, for example, 70% by mass or more, 80% by mass or more, or 90% by mass or more. On the other hand, of all compounds B contained in the active material, the proportion of compound B contained in the covering portion can be, for example, 70% by mass or more, 80% by mass or more, or 90% by mass or more.

[0053] In this invention, the core material preferably contains compound A as a main component. "Contains...as a main component" means that the content is, for example, 50% by mass or more, of which it is 70% by mass or more, and especially 90% by mass or more.

[0054] Regarding the content of compound B contained in the covering portion, in the Raman spectrum obtained by measuring the active substance using Raman spectrometry, the area of ​​the peak originating from the aforementioned compound B is denoted as S. PB And will be at 540cm -1 Above and 650cm-1 The area of ​​the peak originating from the aforementioned compound A observed in the following range is denoted as S. PA At that time, as described above, S is preferred. PB With S PA The ratio, i.e., S PB / S PA The value satisfies 0 PB / S PA The degree is ≤1.2.

[0055] The presence of compound B on the surface of a core material containing compound A can be confirmed by the Raman spectroscopy described above. In addition, it can also be confirmed by elemental mapping, X-ray photoelectron spectroscopy (XPS), STEM, a combination of STEM and energy-dispersive X-ray spectroscopy (EDS), Auger electron spectroscopy, etc.

[0056] Regardless of the states in which compounds A and B exist, the cumulative particle size D of the active substance at a cumulative volume of 50% capacity is determined by laser diffraction scattering particle size distribution method. 50 All are, for example, 20 μm or less, more preferably less than 15 μm, more preferably more than 1 μm and less than 10 μm, and more preferably more than 2 μm and less than 8 μm. By making D 50 With a particle size of less than 20 μm, when the active material is used, for example, in a cathode compound, good contact between it and the solid electrolyte in the cathode compound can be ensured, thereby improving the lithium-ion utilization rate of the active material. Furthermore, by making D... 50 The particle size is greater than 1 μm, which can prevent particle aggregation and increase the viscosity of the slurry. In order to adjust the D50 of the active material to the aforementioned range, it is only necessary to adjust the operating conditions of the spray drying granulation method, the rotating flow bed granulation method, or the decomposition conditions, etc., and is not limited to these adjustment methods.

[0057] A-4. Manufacturing of active substances

[0058] Next, a suitable method for manufacturing the active substance of the present invention will be described.

[0059] ​First, the manufacturing method of the core material containing compound A will be described. Compound A can be obtained as follows: For example, weighing and mixing raw materials such as a lithium source compound, a manganese source compound, and, if necessary, a nickel source compound, a cobalt source compound, and a titanium source compound, pulverizing them using a wet mill, granulating them, calcining them, heat-treating them as needed, disintegrating them under preferred conditions, and then classifying them as needed. Alternatively, the core material containing compound A can be obtained by adding an alkaline substance such as sodium hydroxide to an aqueous solution containing a manganese source compound and, if necessary, a nickel source compound, a cobalt source compound, and a titanium source compound, to precipitate a metal composite hydroxide, and then mixing the metal composite hydroxide with a lithium source compound and calcining it.

[0060] It should be noted that the detailed manufacturing method for the core material containing compound A can be the same as that described in, for example, International Publication No. 2019 / 044733, therefore, the description here is omitted. The contents of that publication are incorporated herein by reference as part of this specification.

[0061] Next, the preparation of compound B will be described. Compound B is preferably formed on the surface of the core material containing compound A obtained as described above. To form compound B on the surface of the core material containing compound A, it is sufficient to contact compound A with a processing solution containing a lithium source compound and a niobium source compound. Examples of lithium source compounds include lithium hydroxide, lithium sulfate, and lithium chloride. Examples of niobium source compounds include ammonium niobate peroxide. A slurry is prepared by mixing a processing solution containing these compounds dissolved in water with compound A, and the slurry is heated to 90°C or higher, causing the lithium source compound and ammonium niobate peroxide to react in the solution to generate compound B. Compound B has the property of readily adsorbing onto the surface of the core material containing compound A; therefore, by drying the slurry, compound B can be formed on the surface of the core material. The processing solution containing the lithium source compound and ammonium niobate peroxide, heated to 90°C or higher, can be sprayed onto the core material containing compound A, or compound B can be generated from the processing solution heated to 90°C or higher and applied to the surface of the core material containing compound A. Subsequently, it is crushed and heat-treated as needed.

[0062] The amount of the treatment solution is preferably such that the proportion of niobium in the active material is, for example, 0.01% by mass or more, more preferably 0.1% by mass or more, and especially more preferably 0.5% by mass or more. On the other hand, the aforementioned proportion is further preferably such that the proportion of niobium in the active material is, for example, 20% by mass or less, more preferably 15% by mass or less, and especially more preferably 10% by mass or less. The concentration of the aforementioned treatment solution is not particularly limited.

[0063] By drying the aforementioned slurry, compound B can be deposited on the surface of the core material containing compound A. To dry the slurry, methods such as spray drying granulation or rotating flow layer granulation can be used. Subsequently, heat treatment can be performed as needed. Alternatively, heat treatment can be performed in an atmospheric atmosphere. The drying and heat treatment temperatures can be set to a lower temperature, preferably 25°C or higher and 700°C or lower, more preferably 40°C or higher and 500°C or lower, and more preferably 60°C or higher and 200°C or lower. The heat treatment time is preferably 1 hour or higher and 20 hours or lower, more preferably 1 hour or higher and 15 hours or lower, and more preferably 1 hour or higher and 10 hours or lower. This allows for the successful acquisition of an active material with a Raman spectral ratio satisfying the aforementioned range. If excessively high temperatures are used for heat treatment, the resulting active material is unlikely to meet the aforementioned Raman spectral ratio.

[0064] A-5. Uses of active substances

[0065] The active material of the present invention can be suitably used as the positive electrode active material of a battery.

[0066] B. Electrode mixture

[0067] The electrode mixture of the present invention is a mixture containing at least the above-mentioned active substances, and may, as needed, contain at least one of an electrolyte, a conductive material, and a binder. When the active substances are used as positive electrode active substances, the electrode mixture becomes a positive electrode mixture constituting the positive electrode layer. It should be noted that the active substances contained in the electrode mixture can be assumed to be the same as those described in the aforementioned "A. Active Substances" section, therefore, the description here is omitted.

[0068] Examples of electrolytes used in this invention include solid electrolytes. Examples of solid electrolytes include inorganic solid electrolytes such as sulfide solid electrolytes, oxide solid electrolytes, nitride solid electrolytes, and halide solid electrolytes; and organic polymer electrolytes such as polymer electrolytes. From the viewpoint of maximizing the effects of this invention, the electrolyte used in this invention is preferably a sulfide solid electrolyte. The sulfide solid electrolyte can be the same as that used in general solid-state batteries. The sulfide solid electrolyte can be, for example, an electrolyte containing Li and S and having lithium-ion conductivity. The sulfide solid electrolyte can be any of a crystalline material, a glass ceramic, or a glass. The sulfide solid electrolyte can have a sulfide-germanium ore type crystal structure. Examples of such sulfide solid electrolytes include Li₂S-P₂S₅, Li₂S-P₂S₅-LiX ("X" represents one or more halogen elements), Li₂S-P₂S₅-P₂O₅, Li₂S-Li₃PO₄-P₂S₅, Li₃PS₄, Li₄P₂S₆, and Li₂S-P₂S₅.10 GeP2S 12 Li 3.25 Ge 0.25 P 0.75 S4, Li7P3S 11 Li 3.25 P 0.95 S4, Li a PS b X c (X is at least one halogen element. a represents a number of 3.0 or higher and 6.0 or lower. b represents a number of 3.5 or higher and 4.8 or lower. c represents a number of 0.1 or higher and 3.0 or lower.) Compounds such as those shown are also examples. In addition, sulfide solid electrolytes described in, for example, International Publication No. 2013 / 099834 and International Publication No. 2015 / 001818 can be listed.

[0069] The active material contained in the electrode mixture may be the only active material of the present invention, or it may be used in combination with other active materials. Examples of other active materials include known active materials containing lithium transition metal complex oxides. The proportion of the active material of the present invention in the electrode mixture may be, for example, 20% by mass or more, 30% by mass or more, or 40% by mass or more. On the other hand, the aforementioned proportion may be, for example, 70% by mass or less, or 60% by mass or less.

[0070] C. Battery

[0071] The battery of the present invention preferably comprises a positive electrode layer containing a positive electrode active material, a negative electrode layer containing a negative electrode active material, and a solid electrolyte layer containing a solid electrolyte, wherein the aforementioned positive electrode active material is the aforementioned active material. The battery can be manufactured, for example, by stacking the positive electrode layer, the solid electrolyte layer, and the negative electrode layer prepared as described above into three layers and then pressing them together.

[0072] To enhance the desired effect, the battery of the present invention preferably has an interface where the positive electrode active material contacts the solid electrolyte. Here, "positive electrode active material in contact with solid electrolyte" also includes any one of the following: the positive electrode active material contained in the positive electrode layer in contact with the solid electrolyte, or the positive electrode active material contained in the positive electrode layer in contact with the solid electrolyte contained in the solid electrolyte layer.

[0073] The battery of the present invention can be used in solid-state batteries, especially lithium solid-state batteries. Lithium solid-state batteries can be primary or secondary batteries, with lithium secondary batteries being preferred. "Solid-state battery" includes not only solid-state batteries that completely do not contain liquid or gel-like substances as electrolytes, but also those containing, for example, less than 50% by mass, less than 30% by mass, or less than 10% by mass of liquid or gel-like substances as electrolytes.

[0074] The negative electrode active material used in the aforementioned negative electrode layer can be the same as that used in general lithium batteries. Specifically, materials that absorb, store, and release lithium ions can be used, such as carbon materials, silicon oxide compounds (e.g., silicon and Si-O), tin compounds, lithium titanate, and other known materials. Examples of carbon materials include, for instance, substances obtained by sintering organic polymers such as polyacrylonitrile, phenolic resin, phenolic varnish resin, and cellulose, as well as artificial graphite and natural graphite. The aforementioned negative electrode layer, except for using this negative electrode active material, can be fabricated using the same procedures as the positive electrode layer.

[0075] Example

[0076] The present invention will now be described in more detail through examples. However, the scope of the present invention is not limited to these examples. Unless otherwise specified, "%" refers to "mass %".

[0077] [Example 1]

[0078] Except for the absence of Al raw materials, a lithium-manganese-containing composite oxide was obtained using the same method as described in Example 1 of International Publication No. 2019 / 044733. XRD analysis confirmed that this lithium-manganese-containing composite oxide is a spinel-type lithium-manganese-containing composite oxide. Furthermore, the chemical analysis results of this spinel-type lithium-manganese-containing composite oxide, i.e., compound A, showed the following composition: Li: 4.2%, Mn: 41.6%, Ni: 13.5%, Ti: 5.1%. The same applies to subsequent examples and comparative examples.

[0079] Compound B is generated on the surface of a core material containing compound A obtained through the aforementioned operation. Compound B is generated through the following steps.

[0080] A mixed aqueous solution was prepared by dissolving 6.4 g of ammonium niobate peroxide in 450 mL of lithium hydroxide aqueous solution with the lithium ion concentration adjusted to 11.4 g / L. 100 g of the previously obtained core material was added to this mixed aqueous solution to prepare a slurry. The slurry was heated to above 90°C and held for 10 minutes. By heating above 90°C, Li-Nb-O compounds with properties that readily adsorb onto the core material surface were generated. After decanting the liquid, it was washed twice with 900 mL of 0.14 mol / L lithium sulfate solution. Subsequently, it was dried at 120°C and then heat-treated at 200°C for 2 hours under atmospheric atmosphere to obtain the target active material. The volumetric cumulative particle size D of the obtained active material was... 50 It is 3.8μm.

[0081] The proportion of niobium in the active material, as determined by ICP emission spectroscopy, is shown in Table 1 below.

[0082] [Example 2]

[0083] In Example 1, the amount of ammonium niobate peroxide used to generate compound B was set to 8.5 g. Otherwise, the procedure was the same as in Example 1 to obtain the active material. The volumetric cumulative particle size D of the obtained active material was... 50 It is 3.8μm.

[0084] The proportion of niobium in the active material, as determined by ICP emission spectroscopy, is shown in Table 1 below.

[0085] [Example 3]

[0086] In Example 1, the amount of ammonium niobate peroxide used to generate compound B was set to 17.0 g. Otherwise, the procedure was the same as in Example 1 to obtain the active material. The volumetric cumulative particle size D of the obtained active material was... 50 It is 3.8μm.

[0087] The proportion of niobium in the active material, as determined by ICP emission spectroscopy, is shown in Table 1 below.

[0088] [Example 4]

[0089] In Example 1, the amount of ammonium niobate peroxide used to generate compound B was set to 25.5 g. Otherwise, the procedure was the same as in Example 1 to obtain the active material. The volumetric cumulative particle size D of the obtained active material is... 50 It is 3.8μm.

[0090] The proportion of niobium in the active material, as determined by ICP emission spectroscopy, is shown in Table 1 below.

[0091] [Example 5]

[0092] In Example 1, the amount of ammonium niobate peroxide used to generate compound B was set to 42.5 g. Otherwise, the procedure was the same as in Example 1 to obtain the active material. The volumetric cumulative particle size D of the obtained active material was... 50 It is 3.6μm.

[0093] The proportion of niobium in the active material, as determined by ICP emission spectroscopy, is shown in Table 1 below.

[0094] [Comparative Example 1]

[0095] In Example 1, compound B did not form on the surface of the particles of compound A. Otherwise, the procedure was the same as in Example 1 to obtain the active material. The volumetric cumulative particle size D of the active material is... 50 It is 4.6 μm.

[0096] [Evaluation 1]

[0097] For the active substances obtained in the examples and comparative examples, Raman spectra were measured using Raman spectrometry according to the steps described below, and the area S of the peak originating from compound A was determined. PA and the area S of the peak originating from compound B PB The results are shown in Table 1 below. The Raman spectra and peak separation results obtained for the active substance of Example 4 are shown in Table 1. Figure 1 In addition, STEM images were taken of the active substances obtained in Examples 2-4. The results are shown below. Figure 2 (a)~(c).

[0098] Furthermore, the Raman spectra measured for the active substances of each embodiment and comparative example, including Example 4, are shown below. Figure 3 .

[0099] <Raman Spectroscopy Determination>

[0100] (Sample preparation)

[0101] When measuring the Raman spectrum of powder samples, fewer surface irregularities and higher particle density result in more particles existing in the space where the excitation light and Raman scattered light converge, allowing for higher Raman light intensity with lower laser excitation power. Therefore, using a MINI hydraulic press manufactured by Specac and a Φ7mm granulation mold, the active materials obtained in the examples and comparative examples were pressurized to 1 ton each, thereby forming granules.

[0102] (Measurement conditions)

[0103] • Device: LabRAM HR Evolution (Made by Horiba Seisakusho)

[0104] • Excitation wavelength: 325nm

[0105] • Excitation power: 0.6mW

[0106] • Detector: Synerity OE

[0107] • Attenuation filter: 10%

[0108] • Grating: 1200gr / mm

[0109] • Confocal hole: 100μm

[0110] • Exposure time: 40 seconds

[0111] • Objective lens: ×40 / VIS

[0112] • Mapping area: 30μm × 9μm

[0113] • Measurement interval: 2μm

[0114] • Cumulative number of times: 1

[0115] Regarding wavenumber correction, measurements were performed on Si, used as a standard sample, to make the main peak at 520.0 cm⁻¹. -1 .

[0116] Mapping measurements were performed using the aforementioned conditions. Subsequently, the entire spectrum of the mapped region was averaged to obtain the main spectrum. It should be noted that when the S / N ratio difference in the spectrum makes it difficult to determine whether it originates from a peak in the sample or noise, the measurement area can be increased and the spectrum averaged. Additionally, sometimes the spectrum contains peaks based on cosmic rays. It can be determined whether these peaks are based on cosmic rays. If the peak does not appear at that wavenumber with good reproducibility during repeated measurements, then the peak can be identified as a cosmic ray.

[0117] The laser excitation wavelength was 325 nm. This is because, generally, with shorter excitation wavelengths, the penetration depth of light into the material is shallower, making it easier to observe peaks originating from compound B covering the surface of compound A. In fact, the inventors confirmed that when the sample of Example 1 was measured using an excitation wavelength of 532 nm, no peaks originating from compound B were observed.

[0118] =Peak Analysis=

[0119] Peak fitting in the Raman spectrum was performed using the Peak Analyzer fitting program within OriginPro 2019, a plotting software from OriginLab Corporation. Peak fitting was used to obtain parameters such as peak number, full width at half maximum (FWHM), and area. Baseline correction was performed before fitting by removing the baseline from the spectrum. The baseline was determined using a 350 cm⁻¹ baseline. -1 ~1500cm -1 Make within 180cm range -1 300cm -1 1125cm -1 1425cm -1 The fourth point is determined by a fifth-degree polynomial. Furthermore, the baseline is removed from the measured spectrum. Regarding the function used in the fitting, 540 cm⁻¹ -1 ~650cm -1 The peak is set to the Vogit function, and all other peaks are set to the Gaussian function.

[0120] <Peak area S PA and S PB Calculation >

[0121] The area of ​​the peak originating from compound B is denoted as S. PBAnd will be at 540cm -1 Above and 650cm -1 The wavenumber range below has the area of ​​the peak originating from compound A at its apex, denoted as S. PA The aforementioned S PA With S PB The ratio of the peak area to the peak area is denoted as S. PA / S PB .

[0122] [Evaluation 2]

[0123] Using the active materials obtained in the examples and comparative examples as positive electrode active materials, solid-state batteries were fabricated according to the following steps. The discharge capacity of the fabricated solid-state batteries was measured according to the following steps. The results are shown in Table 1 below.

[0124] <Fabrication and Discharge Capacity Measurement of Solid-State Batteries>

[0125] The substances prepared in the examples and comparative examples were used as positive electrode active materials, graphite (Gr) powder was used as negative electrode active materials, and sulfide solid electrolyte with a sulfide-germanium sulfide crystal structure was used as solid electrolyte powder.

[0126] The positive electrode powder was prepared by mixing the positive electrode active material, solid electrolyte powder and conductive material (carbon-based material) powder prepared in the examples and comparative examples in a mortar at a ratio of 60%:30%:10%.

[0127] The negative electrode powder is prepared by mixing graphite (Gr) powder and solid electrolyte powder in a mortar at a ratio of 50%:50%.

[0128] 50 mg of solid electrolyte powder was filled into the insulating cylinder (φ10.5 mm) of a sealed tank and uniaxially molded at 184 MPa. Next, 13 mg of positive electrode powder was filled, and 10 mg of negative electrode powder was filled to the opposite side. After uniaxial molding at 551 MPa, the tank was tightened with pressure screws to obtain a solid battery (solid-state lithium secondary battery) with a positive electrode layer, a negative electrode layer, and a solid electrolyte layer.

[0129] For the obtained solid-state battery, in the first cycle, it was charged at a constant current of 0.1C until the charging termination voltage was 5.0V. Thereafter, it was charged at a constant voltage of 5.0V until the current reached 0.01C. Next, it was discharged at a constant current of 0.1C until the discharge termination voltage was 3.0V. The capacity obtained by discharging at a constant current until reaching 3.0V was taken as the discharge capacity.

[0130] [Table 1]

[0131]

[0132] As clearly shown in Table 1, the solid-state batteries using the active materials obtained in each example as positive electrode active materials have a larger discharge capacity compared to the solid-state batteries using the active materials of the comparative examples.

[0133] like Figure 1 As shown, peaks originating from compound A and compound B were observed in the Raman spectrum of the active substance in Example 4. The wavenumber originating from compound A was 540 cm⁻¹. -1 Above and 650cm -1 The peaks in the following range were observed as multiple overlapping peaks. The results of peak separation of the overlapping peaks are shown in the same figure. Of the two peaks separated, the low-wavenumber peak originates from the one-to-one vibration of the transition element and oxygen element constituting compound A. The high-wavenumber peak originates from the overall vibration of the transition element and all oxygen elements surrounding it. The area S of the low-wavenumber peak is shown in the figure. PA1 The area S of the peak on the high wavenumber side PA2 The sum, i.e. S PA1 +S PA2 It is the area S of the peak originating from compound A. PA .

[0134] like Figure 2 As shown in (a) to (c), it can be confirmed that in the active materials of Examples 2 to 4, there is a covering containing compound B on the surface of the core material containing compound A.

[0135] Industrial availability

[0136] According to the present invention, an active material capable of reducing the interfacial resistance with a solid electrolyte and improving battery capacity can be provided.

Claims

1. An active substance comprising compound A and compound B, Compound A contains lithium (Li), M, and oxygen (O), wherein, The element M represents one or more elements selected from nickel (Ni), cobalt (Co), and manganese (Mn). Compound B contains lithium (Li), niobium (Nb), and oxygen (O). In the Raman spectrum obtained by Raman spectrometry, the area of ​​the peak originating from compound B is denoted as S. PB And will be at 540cm -1 Above and 650cm -1 The area of ​​the peak originating from compound A observed in the following range is denoted as S. PA At that time, S PB With S PA The ratio, i.e., S PB / S PA The value satisfies 0 PB / S PA ≤1.2,​ The compound A is a spinel-type composite oxide or a layered rock salt-type composite oxide. The compound B is represented by Li x NbO y where 1 < x ≤ 2 and 3 ≤ y ≤ 8.

2. The active substance according to claim 1, wherein, The compound A is a spinel-type composite oxide represented by LiM2O4 or a layered rock salt-type composite oxide represented by LiMO2.

3. The active substance according to claim 1 or 2, comprising 0.1% by mass and less than 20% by mass of niobium (Nb).

4. The active substance according to claim 1 or 2, wherein, Compound B is present on at least a portion of the surface of the core material containing compound A.

5. An electrode mixture comprising the active substance and a solid electrolyte as described in any one of claims 1 to 4.

6. A battery comprising a positive electrode layer containing a positive electrode active material, a negative electrode layer containing a negative electrode active material, and a solid electrolyte layer containing a solid electrolyte, wherein, The positive electrode active material is any one of the active materials described in claims 1 to 4.

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