positive electrode active material

Abstract

Provided is a positive electrode active material capable of reducing the rate of increase in resistance that occurs with charging and discharging of a battery. The positive electrode active material has a first peak in the range of 690 ev or higher and 700 ev or lower and a second peak in the range of 640 ev or higher and 650 ev or lower in TEM-EDX analysis, and contains an Mn element corresponding to the second peak.

Description

Technical Field

[0001] This disclosure relates to positive electrode active materials. Background Technology

[0002] Various technologies have been proposed regarding the positive electrode active materials disclosed in Patent Documents 1 to 3.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2021-114411

[0006] Patent Document 2: Japanese Patent Publication No. 2021-509764

[0007] Patent Document 3: Japanese Patent Application Publication No. 2010-135207 Summary of the Invention

[0008] The problem that the invention aims to solve

[0009] In the past, various positive electrode active materials have been proposed to obtain positive electrodes with high battery characteristics such as high cycle performance and high output performance.

[0010] When manganese-containing positive electrode active materials are used in batteries, their resistance increases with the charging and discharging of the battery, and there is room for improvement in this regard.

[0011] This disclosure was made in view of the above-mentioned circumstances, and its main purpose is to provide a positive electrode active material capable of reducing the rate of increase in resistance during the charging and discharging of the battery.

[0012] Methods for solving problems

[0013] That is, this disclosure includes the following methods.

[0014] <1>

[0015] A positive electrode active material,

[0016] In TEM-EDX (transmission electron microscopy-energy dispersive X-ray spectroscopy) analysis, the positive electrode active material exhibits a first peak value in the range of 690 eV to 700 eV, and a second peak value in the range of 640 eV to 650 eV.

[0017] The positive electrode active material contains Mn element corresponding to the second peak value.

[0018] <2>

[0019] According to the positive electrode active material recorded in <1>, among which,

[0020] When the region extending from the surface of the positive electrode active material toward the center to a predetermined depth T is designated as the surface layer, and the region extending from the predetermined depth T to the center is designated as the core layer...

[0021] In the TEM-EDX analysis, the surface layer has a first peak and a second peak, and the peak intensity of the first peak is higher than that of the second peak, and the amount of the element corresponding to the first peak is higher than the amount of Mn element corresponding to the second peak.

[0022] In the TEM-EDX analysis, the central layer has a first peak and a second peak, and the peak intensity of the second peak is higher than that of the first peak, and the amount of Mn element corresponding to the second peak is higher than that corresponding to the first peak.

[0023] <3>

[0024] According to the positive electrode active material recorded in <1>, among which,

[0025] When the region extending from the surface of the positive electrode active material toward the center to a predetermined depth T is designated as the surface layer, and the region extending from the predetermined depth T to the center is designated as the core layer...

[0026] In the TEM-EDX analysis, the surface layer exhibits the first peak but does not have the second peak, and does not contain the Mn element corresponding to the second peak.

[0027] In the TEM-EDX analysis, the central layer has the second peak value but does not have the first peak value and does not contain any elements corresponding to the first peak value.

[0028] <4>

[0029] According to the positive electrode active material recorded in <1>, among which,

[0030] When the region extending from the surface of the positive electrode active material toward the center to a predetermined depth T1 is designated as the first surface layer, the region extending from the predetermined depth T1 to a predetermined depth T2 is designated as the second surface layer, the region extending from the predetermined depth T2 to a predetermined depth T3 is designated as the first central layer, and the region extending from the predetermined depth T3 to the center is designated as the second central layer...

[0031] In the TEM-EDX analysis, the first surface layer has the first peak value but does not have the second peak value and does not contain the Mn element corresponding to the second peak value.

[0032] In the TEM-EDX analysis, the second surface layer has both the first peak and the second peak, and the peak intensity of the first peak is higher than that of the second peak, and the amount of the element corresponding to the first peak is higher than the amount of Mn corresponding to the second peak.

[0033] In the TEM-EDX analysis, the first central layer has a first peak and a second peak, and the peak intensity of the second peak is higher than that of the first peak, and the amount of Mn element corresponding to the second peak is higher than that corresponding to the first peak.

[0034] In the TEM-EDX analysis, the second central layer has the second peak value but does not have the first peak value and does not contain any elements corresponding to the first peak value.

[0035] <5>

[0036] According to any one of <1> to <4>, the positive electrode active material, among which,

[0037] The positive electrode active material further contains Li, Ni, and Co elements.

[0038] <6>

[0039] According to the positive electrode active material described in <5>, among which,

[0040] The positive electrode active material contains 0.1 mol of Mn, relative to the total amount of Ni, Co, and Mn contained in it being 1 mol.

[0041] <7>

[0042] A positive electrode layer comprising the positive electrode active material described in any one of <1> to <6>.

[0043] <8>

[0044] A battery having a positive electrode layer containing a positive electrode active material described in any one of <1> to <6>.

[0045] <9>

[0046] A method for manufacturing a positive electrode active material, wherein the positive electrode active material described in any one of <1> to <6> is manufactured.

[0047] include:

[0048] The first stage firing process involves firing a first mixture of transition metal hydroxide and lithium compound at 700℃~1100℃ to obtain the precursor of the positive electrode active material.

[0049] The spray drying process includes spray drying the second mixture of the precursor of the positive electrode active material and Mn(NO3)2 using a spray dryer to obtain a dried product; and

[0050] The second stage involves a firing process, in which the dried material is fired at 100℃ to 130℃ to obtain the positive electrode active material.

[0051] In the spray drying process, the air inlet temperature of the spray dryer is 100℃~130℃.

[0052] Invention Effects

[0053] According to this disclosure, a positive electrode active material can be provided that can reduce the rate of increase in resistance during battery charging and discharging. Attached Figure Description

[0054] Figure 1 This is a schematic diagram illustrating an example of the structure of the positive electrode active material of this disclosure.

[0055] Figure 2 This is a schematic diagram illustrating another example of the structure of the positive electrode active material of this disclosure.

[0056] Figure 3 This shows the spectrum of the positive electrode active material of Example 1 obtained by TEM-EDX. Detailed Implementation

[0057] The following describes embodiments of this disclosure. It should be noted that matters not specifically mentioned in this specification but necessary for implementing this disclosure (e.g., the general composition and manufacturing process of the positive electrode active material that does not constitute a feature of this disclosure) are design matters understood by those skilled in the art based on prior art. This disclosure can be implemented based on the content disclosed in this specification and common technical knowledge in the field.

[0058] In addition, the dimensional relationships (length, width, thickness, etc.) in the attached drawings do not reflect the actual dimensional relationships.

[0059] Unless otherwise specified, elements described in the "singular form" may include plural forms. For example, a particle may also represent multiple particles (a group of particles).

[0060] In this disclosure, an example of a method for calculating the average particle size is shown below. First, for a single particle, the particle size is calculated by considering it as spherical in a transmission electron microscope (TEM) image or a scanning electron microscope (SEM) image at an appropriate magnification (e.g., 50,000 to 1,000,000 times). For 200 to 300 particles of the same type, the particle size is calculated based on the TEM or SEM observations described above, and the average value of these particles is taken as the average particle size.

[0061] 1. Positive electrode active material

[0062] This disclosure provides a positive electrode active material that, in TEM-EDX analysis, has a first peak value in the range of 690 eV to 700 eV and a second peak value in the range of 640 eV to 650 eV, wherein the positive electrode active material contains Mn element corresponding to the second peak value.

[0063] In this disclosure, because the positive electrode active material exhibits a first peak and a second peak in TEM-EDX analysis, the leaching of Mn elements from the positive electrode active material during battery charging and discharging can be suppressed, thereby inhibiting the increase in battery resistance. This is believed to be because the element corresponding to the first peak is more stable than the Mn element corresponding to the second peak. Since the element corresponding to the first peak exists near the surface of the positive electrode active material, the leaching of Mn elements from the positive electrode active material can be further suppressed.

[0064] Figure 1 This is a schematic diagram illustrating an example of the structure of the positive electrode active material of this disclosure. For example... Figure 1 As shown, the positive electrode active material 100 of this disclosure has: a surface layer 10, which is a region extending from the surface of the positive electrode active material 100 toward the center C to a predetermined depth T; and a central layer 20, which is a region extending from the predetermined depth T to the center C.

[0065] Figure 2 This is a schematic diagram illustrating another example of the structure of the positive electrode active material of this disclosure. For example... Figure 2As shown, the positive electrode active material 200 of this disclosure has: a first surface layer 11, which is a region extending from the surface of the positive electrode active material 200 toward the center C to a predetermined depth T1; a second surface layer 12, which is a region extending from a position at a predetermined depth T1 from the surface of the positive electrode active material 200 to a predetermined depth T2 from the surface of the positive electrode active material 200; a first central layer 21, which is a region extending from a position at a predetermined depth T2 from the surface of the positive electrode active material 200 to a predetermined depth T3 from the surface of the positive electrode active material 200; and a second central layer 22, which is a region extending from a position at a predetermined depth T3 from the surface of the positive electrode active material 200 to the center C of the positive electrode active material 200.

[0066] In TEM-EDX analysis, the positive electrode active material exhibits a first peak value in the range of 690 eV to 700 eV, and a second peak value in the range of 640 eV to 650 eV.

[0067] The presence or absence of the first and second peaks can be confirmed by the following method. In TEM-EDX analysis, the peak observed in the range of 610 eV to 630 eV is taken as the baseline peak. If the peak intensity of the first peak is higher than that of the baseline peak, the first peak is considered to exist. If the peak intensity of the second peak is higher than that of the baseline peak, the second peak is considered to exist.

[0068] The first peak value can be the peak value corresponding to the element Mn(NO3)2. The element corresponding to the first peak value (sometimes referred to as element Q in this disclosure) can be, for example, the element corresponding to Mn(NO3)2, or the Mn element, or an impurity element other than the Mn element. Examples of impurity elements include, for example, element F. That is, element Q can also be at least either the Mn element or the F element.

[0069] The second peak could be the peak value corresponding to the Mn element in Mn2p3 of lithium nickel cobalt manganese oxide. In lithium nickel cobalt manganese oxide, Mn mainly exists in the form of LiMnO2 crystal structure, and sometimes it also exists in other forms such as Li2MnO3, MnO2, Mn2O3, and MnO.

[0070] The crystal structure of a compound containing an element corresponding to the first peak value can also be different from the crystal structure of a compound containing an Mn element corresponding to the second peak value.

[0071] When the element corresponding to the first peak is Mn, the valence of the Mn element corresponding to the first peak can be greater than the valence of the Mn element corresponding to the second peak.

[0072] The positive electrode active material contains at least Mn element corresponding to the second peak value.

[0073] [First Implementation Method]

[0074] The positive electrode active material can be a monolayer structure containing an Mn layer, which contains an element corresponding to a first peak value and an Mn element corresponding to a second peak value. In the positive electrode active material, the amount of the element corresponding to the first peak value is less than the amount of the Mn element corresponding to the second peak value.

[0075] [Second Implementation]

[0076] The positive electrode active material can also be a two-layer structure consisting of a surface layer and a core layer.

[0077] The surface layer is the region extending from the surface of the positive electrode active material toward the center to a specified depth T.

[0078] In TEM-EDX analysis, the surface layer has a first peak and a second peak, and the peak intensity of the first peak is higher than that of the second peak, and the amount of the element corresponding to the first peak is higher than that of the Mn element corresponding to the second peak.

[0079] Alternatively, in TEM-EDX analysis, the surface layer has a first peak and no second peak, contains elements corresponding to the first peak, but does not contain Mn elements corresponding to the second peak.

[0080] The surface layer may also not contain Ni or Co elements.

[0081] The outermost surface of the surface layer can be set as the location where the first peak is first observed when performing a line scan analysis from the surface of the positive electrode active material toward the center using TEM-EDX.

[0082] The central layer extends from a specified depth T of the positive electrode active material to its center. If the specified depth T of the positive electrode active material corresponds to the surface layer, the central layer does not include the specified depth T of the positive electrode active material.

[0083] In TEM-EDX analysis, the central layer has a first peak and a second peak, and the peak intensity of the second peak is higher than that of the first peak. The amount of the element corresponding to the first peak is less than the amount of Mn element corresponding to the second peak.

[0084] Alternatively, in TEM-EDX analysis, the central layer has a second peak but no first peak, contains Mn elements corresponding to the second peak, but does not contain elements corresponding to the first peak.

[0085] The central layer may also contain at least one of Ni and Co elements.

[0086] The outermost surface of the central layer can be defined as the position where, when a line scan analysis is performed from the surface of the positive electrode active material toward the center using TEM-EDX, the peak intensity of the second peak first becomes higher than that of the first peak, or the position where the second peak is observed and the first peak is not observed for the first time.

[0087] The specified depth T from the surface of the positive electrode active material can be, for example, less than half the depth Tmax from the surface of the positive electrode active material to the center, or a depth extending from the surface toward the center exceeding 0 nm but less than 0.9 nm, or a depth extending from the surface toward the center of 0.9 nm. The ratio (T / Tmax) of the specified depth T from the surface of the positive electrode active material to the depth Tmax extending from the surface of the positive electrode active material to the center is, for example, a lower limit greater than 0, greater than 0.001, greater than 0.0036, greater than 0.0072, greater than 0.0144, greater than 0.02, or greater than 0.03, and an upper limit less than 0.5, less than 0.3, less than 0.2, or less than 0.1.

[0088] In the second embodiment, the positive electrode active material may also have a central layer containing Mn elements corresponding to the second peak value, and a surface layer (coating layer) covering the surface of the central layer containing elements corresponding to the first peak value.

[0089] The coating layer can be a layer containing Mn(NO3)2 or a layer composed of Mn(NO3)2.

[0090] The coating layer can be identified, for example, by performing elemental analysis on TEM images observed through TEM using energy-dispersive X-ray spectroscopy (EDX). Elemental analysis can be performed using known methods, such as SEM-EDX (scanning electron microscopy-energy-dispersive X-ray spectroscopy) and X-ray photoelectron spectroscopy (XPS), in addition to TEM-EDX.

[0091] The thickness of the coating layer is not particularly limited, for example, the lower limit is 0.5 nm or more, 1 nm or more, or 3 nm or more, and the upper limit is 20 nm or less, 15 nm or less, 10 nm or less, or 5 nm or less. Here, the thickness of the coating layer is obtained as the average value obtained by measuring at least 5 points when observing the positive electrode active material by TEM.

[0092] [Third Implementation Method]

[0093] The positive electrode active material can also be a four-layer structure consisting of a first surface layer, a second surface layer, a first central layer, and a second central layer.

[0094] The first surface layer is the region extending from the surface of the positive electrode active material toward the center to a specified depth T1.

[0095] The specified depth T1 from the surface of the positive electrode active material can be a depth extending from the surface of the positive electrode active material toward the center that is more than 0 nm and less than 0.9 nm, or it can be a depth extending from the surface of the positive electrode active material toward the center that is 0.9 nm.

[0096] Alternatively, in TEM-EDX analysis, the first surface layer has a first peak and no second peak, contains elements corresponding to the first peak, but does not contain Mn elements corresponding to the second peak.

[0097] The first surface layer may also not contain Ni or Co elements.

[0098] The outermost surface of the first layer can be set as the location where the first peak is first observed when a line scan analysis is performed from the surface of the positive electrode active material toward the center using TEM-EDX.

[0099] The second surface layer extends from a predetermined depth T1 from the surface of the positive electrode active material to a predetermined depth T2 from the surface of the positive electrode active material. If the predetermined depth T1 of the positive electrode active material corresponds to the first surface layer, the second surface layer does not include the predetermined depth T1 of the positive electrode active material.

[0100] The specified depth T2 from the surface of the positive electrode active material can also be a depth of more than 0.9 nm and less than 1.8 nm extending from the surface of the positive electrode active material toward the center.

[0101] Alternatively, in TEM-EDX analysis, the second surface layer has both a first peak and a second peak, with the peak intensity of the first peak being higher than that of the second peak, and the amount of the element corresponding to the first peak being greater than the amount of Mn corresponding to the second peak. Regarding the intensity ratio, the ratio of the first peak intensity to the second peak intensity can be 1.1–2.0 or 1.1–1.2.

[0102] The second surface layer may also contain at least one of Ni and Co elements.

[0103] The outermost surface of the second layer can be defined as the position where, during a line scan analysis of the positive electrode active material from the surface toward the center using TEM-EDX, the second peak is first observed, and the peak intensity of the first peak becomes higher than that of the second peak.

[0104] The first central layer is the region extending from a specified depth T2 from the surface to a specified depth T3. If the specified depth T2 of the positive electrode active material corresponds to the second surface layer, the first central layer does not include the specified depth T2 of the positive electrode active material.

[0105] The specified depth T2 from the surface of the positive electrode active material can also be a depth of more than 1.8 nm and less than 3.6 nm extending from the surface of the positive electrode active material toward the center.

[0106] In TEM-EDX analysis, the first central layer has a first peak and a second peak, and the peak intensity of the second peak is higher than that of the first peak, while the amount of the element corresponding to the first peak is higher than the amount of Mn corresponding to the second peak. Regarding the intensity ratio, the ratio of the first peak intensity to the second peak intensity can be 0.5–0.9 or 0.5–0.6.

[0107] The first central layer may also contain at least one of Ni and Co elements.

[0108] The outermost surface of the first central layer can be set such that, when performing a line scan analysis from the surface of the positive electrode active material toward the center using TEM-EDX, the peak intensity of the second peak first becomes higher than that of the first peak.

[0109] The second central layer extends from a predetermined depth T3 from the surface of the positive electrode active material to the center. If the predetermined depth T3 of the positive electrode active material corresponds to the first central layer, the second central layer does not include the predetermined depth T3 of the positive electrode active material.

[0110] The specified depth T3 from the surface of the positive electrode active material can be a depth of more than 3.6 nm extending from the surface of the positive electrode active material toward the center, or it can be a depth of 3.6 nm extending from the surface of the positive electrode active material toward the center.

[0111] In TEM-EDX analysis, the second central layer has a second peak and does not have a first peak. It contains Mn elements corresponding to the second peak but does not contain elements corresponding to the first peak.

[0112] The second central layer may also contain at least one of Ni and Co elements.

[0113] The outermost surface of the second central layer can be set as the position where the first peak is not observed and the second peak is observed when a TEM-EDX line scan analysis is performed from the surface of the positive electrode active material toward the center.

[0114] The positive electrode active material is used in the battery. Details about the battery will be described later.

[0115] Positive electrode active material can also be particles.

[0116] The average particle size of the positive electrode active material can be, for example, 0.5 μm or more, 1 μm or more, or 2 μm or more. The average particle size of the positive electrode active material can be, for example, 30 μm or less, 10 μm or less, 5 μm or less, or 3 μm or less.

[0117] The positive electrode active material must contain at least Mn corresponding to the second peak value, and may also contain elements corresponding to the first peak value, such as Li, transition metals (TM), and O. The positive electrode active material can be a lithium transition metal composite oxide containing Li, a transition metal, and O. The lithium transition metal composite oxide must contain at least Mn as a transition metal, and may also contain two, three, or more than four transition metals. Examples of transition metals include Ti, V, Cr, Mn, Fe, Co, Ni, Zr, and Nb.

[0118] Lithium transition metal composite oxides need to contain at least Mn as a transition metal, and may further contain, for example, Co and Ni as transition metals.

[0119] Lithium transition metal composite oxides can also contain other metals M besides Li and transition metals, in addition to Li and transition metals. 1 (Including semi-metals). As other metals M 1 Examples include Al, Si, Ga, Ge, In, Sn, etc.

[0120] Lithium transition metal composite oxides may also contain Li, Ni, Co, Mn, and O.

[0121] When the total amount of all metals other than Li in the lithium transition metal composite oxide is 1 mol, the total proportion of Ni, Co, and Mn in the lithium transition metal composite oxide can be, for example, 0.80 mol or more, 0.90 mol or more, 0.95 mol or more, or 1 mol. It should be noted that "total amount of Ni, Co, and Mn" also includes the case where the proportion of Ni and Co in Ni, Co, and Mn is 0.

[0122] Lithium transition metal composite oxides can have the general formula Li x Ni a Co b Mn c O y The composition represented by (0.1≦x≦1.5, 0.5≦a<1.0, 0≦b≦0.3, 0<c≦0.3, a+b+c=1.0, 1.5≦y≦2.1).

[0123] In the general formula, the Li component ratio "x" only needs to satisfy the relationship "0.1 ≤ x ≤ 1.5". The Li component ratio "x" can also be 0.4 or higher, 0.6 or higher, 0.8 or higher, 1.0 or higher, or 1.1 or higher. The Li component ratio "x" can also be 1.4 or lower or 1.2 or lower.

[0124] In the above general formula, the ratio of component O "y" must satisfy the relationship "1.5 ≤ y ≤ 2.1". The ratio of component O "y" can also be 1.6 or higher, 1.7 or higher, 1.8 or higher, or 1.9 or higher. The ratio of component O "y" can also be 2.0 or lower.

[0125] In the above general formula, the Ni component ratio "a", the Co component ratio "b", and the Mn component ratio "c" satisfy the relationship "a+b+c=1.0".

[0126] In the above general formula, the Ni component ratio "a" only needs to satisfy the relationship "0.5 ≤ a < 1.0". The Ni component ratio "a" can also be 0.6 or higher, 0.7 or higher, 0.8 or higher, or 0.85 or higher. The Ni component ratio "a" can also be 0.9 or lower.

[0127] In the above general formula, the Co component ratio "b" only needs to satisfy the relationship "0 ≤ b ≤ 0.3". The Co component ratio "b" can also be, for example, 0.01 or more, 0.02 or more, 0.03 or more, 0.04 or more, 0.05 or more, 0.06 or more, 0.07 or more, or 0.075 or more. The Co component ratio "b" can also be, for example, 0.25 or less, 0.20 or less, 0.15 or less, 0.10 or less, 0.09 or less, or 0.08 or less.

[0128] In the above general formula, the Mn component ratio "c" only needs to satisfy the relationship "0 < c ≤ 0.3". The Mn component ratio "c" can also be, for example, 0.01 or higher, 0.02 or higher, 0.03 or higher, 0.04 or higher, 0.05 or higher, 0.06 or higher, 0.07 or higher, or 0.075 or higher. The Mn component ratio "c" can also be, for example, 0.25 or lower, 0.20 or lower, 0.15 or lower, 0.10 or lower, 0.09 or lower, or 0.08 or lower.

[0129] Any dopant can be added to the lithium transition metal composite oxide. The dopant is an element other than Li, Ni, Co, Mn, and O. The dopant may contain at least one element selected from, for example, the group consisting of Zr, Mo, Mg, Ca, Na, Fe, Cr, Zn, Si, Sn, Al, and Ag. When a+b+c = 1.0, the dopant composition ratio d can be, for example, 0.005 or more, 0.01 or more, 0.02 or more, 0.03 or more, or 0.04 or more. When a+b+c = 1.0, the dopant composition ratio d can also be, for example, 0.05 or less.

[0130] Lithium transition metal complex oxides are crystalline primary particles.

[0131] Lithium transition metal composite oxides are monocrystalline active materials composed of the aforementioned primary particles. Monocrystalline active materials refer to materials that are not polycrystalline (active materials formed by the seamless aggregation of multiple primary particles). That is, monocrystalline active materials can be single-crystal particles. Compared to polycrystalline active materials, monocrystalline active materials have the advantage of less degradation over time.

[0132] In SEM images, single-crystal active materials appear as independent, unaggregated individual particles (primary particles). Single-crystal active materials do not exhibit grain boundaries in SEM images. The magnification of SEM images is, for example, 10,000 to 30,000 times.

[0133] The crystal structure of lithium transition metal composite oxides can be a layered rock salt structure. Alternatively, lithium transition metal composite oxides can also have a crystal structure belonging to space group R-3m.

[0134] The particle size of primary particles in lithium transition metal composite oxides can be 0.5 μm or larger, 0.6 μm or larger, 0.8 μm or larger, or 1.0 μm or larger. If the particle size is too small, the particles cannot grow sufficiently, making it difficult to prepare single crystals. On the other hand, the particle size can be, for example, less than 10 μm, less than 5 μm, or less than 3 μm. The particle size of primary particles can be obtained, for example, from the longest diameter in TEM or SEM images. Furthermore, if the cathode layer contains primary particles (lithium transition metal composite oxides), the particle size of the primary particles can also be obtained from the longest diameter of the primary particles in the SEM cross-sectional image of the cathode layer. The "particle size of primary particles" mentioned here is not the average particle size. That is, when the cathode layer contains multiple primary particles, the "particle size of primary particles" refers to the "particle size of each individual primary particle."

[0135] 2. Method for manufacturing positive electrode active material

[0136] This disclosure provides a method for manufacturing the aforementioned positive electrode active material, comprising:

[0137] The first stage firing process involves firing a first mixture of transition metal hydroxide and lithium compound at 700℃~1100℃ to obtain the precursor of the positive electrode active material.

[0138] The spray drying process includes spray drying the second mixture of the precursor of the positive electrode active material and Mn(NO3)2 using a spray dryer to obtain a dried product; and

[0139] The second stage involves a firing process, in which the dried material is fired at 100℃ to 130℃ to obtain the positive electrode active material.

[0140] In the spray drying process, the air inlet temperature of the spray dryer is 100℃~130℃.

[0141] The method for manufacturing the positive electrode active material disclosed herein includes (1) a first-stage firing process, (2) a spray drying process, and (3) a second-stage firing process.

[0142] (1) First stage firing process

[0143] In the first stage of the firing process, a first mixture of transition metal hydroxide and lithium compound is fired at 700℃~1100℃ to obtain the precursor of the positive electrode active material.

[0144] The method for manufacturing transition metal hydroxides disclosed herein is not particularly limited, and the following methods may be cited as examples. First, an aqueous solution of the transition metal hydroxide as a raw material is prepared. For example, a method of dissolving a water-soluble transition metal compound in water may be cited as a method of preparing the aqueous solution. For example, metal salts such as sulfates and nitrates may be cited as transition metal compounds. For example, NiSO4 and Ni(NO3)2 may be cited as Ni sources. For example, CoSO4, Co(NO3)2, and Co(NO3)3 may be cited as Co sources. For example, MnSO4 and Mn(NO3)2 may be cited as Mn sources. The composition of the aqueous solution may be appropriately adjusted according to the target positive electrode active material.

[0145] Next, a certain amount of NH3 aqueous solution is added to the reaction vessel, and nitrogen replacement is carried out under stirring with a stirrer or similar device to create a non-oxidizing atmosphere. The nitrogen flow rate during nitrogen replacement is not particularly limited; for example, it can be set to 2–6 L / min.

[0146] Next, add an aqueous sodium hydroxide solution to the reaction vessel to maintain an alkaline pH (e.g., pH = 11.3–12.0), while simultaneously adding the above-mentioned raw material aqueous solution and NH3 aqueous solution dropwise into the reaction vessel for 5–15 hours. The reaction temperature is not particularly limited; for example, it can be set to above 50°C and below 65°C.

[0147] Pre-firing can also be carried out after the reaction is complete. Pre-firing can be carried out, for example, at 120℃~220℃, 4~10 hours, and 0.2~1.0MPa.

[0148] After the reaction or pre-calcination is complete, the mixture is washed with water and filtered to remove the transition metal hydroxide, which is then dried. The drying process can be carried out, for example, at 110°C for 10–12 hours.

[0149] In this disclosure, the transition metal hydroxide contains a transition metal. The transition metal hydroxide may be a nickel-cobalt-manganese composite hydroxide containing nickel (Ni), cobalt (Co), and manganese (Mn). In the nickel-cobalt-manganese composite hydroxide, the molar ratio of each metal relative to the total amount of nickel, cobalt, and manganese is the same as the component ratio represented by the above general formula for the lithium transition metal composite oxide in the positive electrode active material portion.

[0150] The lithium compound (Li source) can be, for example, selected from at least one of lithium carbonate, lithium nitrate, lithium acetate, lithium hydroxide, lithium oxide, and lithium chloride. The lithium compound can be lithium hydroxide. The molar ratio of Li in the Li source to the TM contained in the transition metal hydroxide can be, for example, 0.4 or more, 0.6 or more, 0.8 or more, 1.0 or more, or 1.1 or more, or 1.4 or less or 1.2 or less.

[0151] The ratio of lithium compound and transition metal hydroxide in the first mixture is set such that the molar ratio of lithium and other metals relative to the total stoichiometric ratio of lithium and metals contained in the transition metal hydroxide in the target cathode active material is typically equal to the molar ratio of lithium and other metals in the first mixture. The mixing method is not particularly limited and known methods can be used.

[0152] The first mixture may also contain molten salt. By functioning as a flux, the primary particles can undergo sufficient grain growth. The molten salt may contain Li. Examples of molten salts include lithium hydroxide. The molar ratio (Li / TM) of Li in the molten salt relative to the transition metal hydroxide may be, for example, 0.01 or more, 0.05 or more, 0.10 or more, or 0.15 or more. On the other hand, the Li / TM ratio may be, for example, 0.60 or less, 0.50 or less, 0.40 or less, or 0.30 or less.

[0153] The first mixture may also contain lithium hydroxide as a Li source and a molten salt. The molar ratio of Li in the Li source and the molten salt to the TM in the transition metal hydroxide (Li´ / TM) may, for example, be 1.01 or more, 1.05 or more, 1.10 or more, or 1.15 or more. On the other hand, Li´ / TM may, for example, be 1.60 or less, 1.50 or less, 1.40 or less, or 1.30 or less.

[0154] For example, lithium transition metal composite oxides can be obtained by calcining the first mixture at 700℃ to 1100℃ for 8 to 15 hours. Known calcining furnaces such as muffle furnaces can be used for calcination.

[0155] The firing temperature in the first stage of the firing process is limited to a lower limit of 800℃, 850℃, 900℃, or 950℃, and an upper limit of 1000℃.

[0156] The firing time in the first stage of the firing process can be more than 9 hours or more than 10 hours.

[0157] The firing time in the first stage of the firing process can be less than 13 hours or less than 11 hours.

[0158] The precursor of the positive electrode active material obtained by calcining the transition metal hydroxide of this disclosure is usually a single-crystal active material composed of primary particles.

[0159] (2) Spray drying process

[0160] In the spray drying process, a second mixture of the precursor of the positive electrode active material and Mn(NO3)2 is spray dried using a spray dryer to obtain the dried product.

[0161] The intake temperature of the spray dryer is 100℃~130℃. By setting the temperature to not exceed the boiling point of Mn(NO3)2, Mn(NO3)2 can be coated onto the surface of the lithium transition metal composite oxide.

[0162] The suction pressure of the spray dryer can be 1.0 to 3.0 MPa or 2.0 MPa, and the nozzle pressure of the spray nozzle can be 0.1 to 0.3 MPa or 0.2 MPa.

[0163] The mass percentage of Mn(NO3)2 contained in the second mixture is not particularly limited, and can be 1 to 3% by mass or 1.6% by mass.

[0164] The second mixture contains at least a precursor of the positive electrode active material and Mn(NO3)2, and is a slurry obtained by adding the precursor of the positive electrode active material and Mn(NO3)2 to a solvent and stirring.

[0165] Solvents used in the spray drying process include, for example, water and ion-exchanged water.

[0166] (3) Second stage firing process

[0167] In the second stage of the firing process, the dried material is fired at 100℃~130℃ to obtain the positive electrode active material.

[0168] In the second stage of the firing process, by firing the dried material at 100℃~130℃, the evaporation of Mn(NO3)2 can be suppressed, and a positive electrode active material containing the element corresponding to the first peak value can be obtained.

[0169] The firing time in the second stage firing process can be more than 1 hour, more than 9 hours, or more than 10 hours. On the other hand, the firing time in the second stage firing process can be less than 15 hours, less than 13 hours, or less than 11 hours.

[0170] 3. Battery

[0171] The positive electrode active material provided in this disclosure is, for example, a positive electrode active material that can be used as the positive electrode of a battery (such as a lithium-ion battery). That is, in this disclosure, a battery in which a positive electrode, an electrolyte layer, and a negative electrode are stacked in sequence can be provided, i.e., a battery in which the positive electrode contains the positive electrode active material of this disclosure.

[0172] According to this disclosure, by using the above-mentioned positive electrode active material in a battery, the rate of increase in resistance during battery charging and discharging can be reduced.

[0173] The following is an explanation of the battery.

[0174] [positive electrode]

[0175] The positive electrode has a positive electrode layer and may be further equipped with a positive electrode current collector as needed.

[0176] The positive electrode layer is a layer that contains at least the positive electrode active material disclosed herein as the positive electrode active material.

[0177] The positive electrode layer can be disposed on one side or both sides of the positive electrode current collector. The positive electrode can be a multilayer structure with two or more positive electrode layers formed on at least one side of the positive electrode current collector. In addition, when two or more positive electrode layers are formed, the types of positive electrode active materials contained in each positive electrode layer can be the same or different.

[0178] The positive electrode active material used in the positive electrode layer may contain only the positive electrode active material disclosed herein, or it may further contain other active materials. Additionally, the positive electrode layer may, as needed, contain at least one of an electrolyte, a conductive material, and a binder.

[0179] The mixing ratio (mass ratio) of the positive electrode active material and other active materials disclosed herein can be, for example, "positive electrode active material of this disclosure: other active materials = 9.5:0.5~0.5:9.5", "positive electrode active material of this disclosure: other active materials = 9:1~1:9", "positive electrode active material of this disclosure: other active materials = 8:2~2:8", "positive electrode active material of this disclosure: other active materials = 7:3~3:7", or "positive electrode active material of this disclosure: other active materials = 6:4~4:6". Other active materials can be polycrystalline active materials (polycrystalline particles) composed of secondary particles of the aforementioned lithium transition metal composite oxide. Other active materials include, for example, lithium iron phosphate (olivine structure), lithium manganese phosphate (olivine structure), lithium manganese iron phosphate (olivine structure), LiMnO2 (rock salt structure), Li(NiMn)2O4 (spinel structure), and LiCoO2 (layered structure).

[0180] The proportion of positive electrode active material in the positive electrode layer can be, for example, 20% by mass or more, or 30% by mass or more, or 40% by mass or more. If the proportion of positive electrode active material is too small, there is a possibility that sufficient energy density cannot be obtained. On the other hand, the proportion of positive electrode active material in the positive electrode layer can be, for example, 95% by mass or less, or 70% by mass or less, or 60% by mass or less. If the proportion of positive electrode active material is too large, there is a possibility that the ionic conductivity and electronic conductivity in the positive electrode layer will be relatively reduced.

[0181] As an electrolyte, examples include solid electrolytes. Solid electrolytes can be inorganic solid electrolytes such as sulfide solid electrolytes, halide solid electrolytes, oxide solid electrolytes, and complexed hydride solid electrolytes, or organic solid electrolytes such as gel electrolytes.

[0182] Sulfide solid electrolytes are electrolytes containing sulfur (S). They typically contain at least lithium (Li) and sulfur. Sulfide solid electrolytes may also further contain nitrogen (M) (M is at least one of P, As, Sb, Si, Ge, Sn, B, Al, Ga, and In). Additionally, sulfide solid electrolytes may also contain halogens such as sulfur (F), chlorine (Cl), br, and iodine (I).

[0183] Sulfide solid electrolytes can be glass-based (amorphous), glass-ceramic, or crystalline. They can also possess crystalline phases. Examples of such crystalline phases include the Thio-LISICON type, the argyrodite type, and the LGPS type.

[0184] The composition of sulfide solid electrolytes is not particularly limited; examples include xLi₂S・(1-x)P₂S₅ (0.5≦x<1) and yLiI・zLiBr・(100-yz)(xLi₂S・(1-x)P₂S₅) (0.5≦x<1, 0≦y≦30, 0≦z≦30). In the above compositions, x can satisfy 0.7≦x≦0.8. Other examples of sulfide solid electrolyte compositions include Li 7-x PS 6-x X x X is at least one of F, Cl, Br, and I, and x satisfies 0 ≤ x < 2. Other examples of sulfide solid electrolytes include Li. 4-x Me 1-x P x S4 (0 < x < 1). Me is at least one of Al, Zn, In, Ge, Si, Sn, Sb, Ga, and Bi. Examples of sulfide solid electrolytes include LiI-LiBr-Li2S-P2S5, LiI-Li2S-P2S5, LiI-Li2S-P2O5, and LiI-Li3PO4-P2S5.

[0185] Examples of oxide solid electrolytes include substances with a garnet-type crystal structure containing Li, La, A (where A is at least one of Zr, Nb, Ta, and Al), and O. Examples of oxide solid electrolytes include Li₂O-B₂O₃-P₂O₅, Li₂O-SiO₂, Li₂O-B₂O₃, and Li₂O-P₂O₃. 1.3 Al 0.3 Ti 0.7 (PO4)3, Li5La3Ta2O 12 Li7La3Zr2O 12 Li6BaLa2Ta2O 12 Li 3.6 Si 0.6 P 0.4 O4, Li4SiO4, Li3PO4, and Li 3+x PO 4-x N x (1≦x≦3), etc.

[0186] As a halide solid electrolyte, it can be, for example, a solid electrolyte containing Li, D, and X (D represents at least one of Ti, Al, and Y, and X represents F, Cl, or Br).

[0187] Gel electrolytes may also contain an electrolyte and a polymeric material. The polymeric material can form a polymeric matrix. The polymeric material includes, for example, at least one selected from the group consisting of polyvinylidene fluoride (PVdF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), polyacrylonitrile (PAN), polyvinylidene fluoride-polyacrylonitrile (PVdF-PAN), polyethylene oxide (PEO), polyethylene glycol (PEG), and derivatives of the above substances.

[0188] From an operational point of view, solid electrolytes can be in granular form.

[0189] In addition, the average particle size of the solid electrolyte is not particularly limited and can be from 1 nm to 100 μm.

[0190] The proportion of solid electrolyte in the positive electrode layer is, for example, 1% by mass or more. If the proportion of solid electrolyte is too small, there is a possibility that the ion conduction pathways in the positive electrode layer are insufficient. On the other hand, the proportion of solid electrolyte in the positive electrode layer is, for example, 60% by mass or less. If the proportion of solid electrolyte is too large, there is a possibility that the proportion of positive electrode active material will be relatively reduced, resulting in a decrease in energy density.

[0191] The positive electrode layer can also contain conductive materials. By adding conductive materials, the electronic conductivity of the positive electrode layer is improved. Examples of conductive materials include carbon-based conductive materials, metal particles, and conductive polymers. Examples of carbon-based conductive materials include granular materials such as acetylene black (AB) and Ketjen black (KB), fibrous materials such as vapor-grown carbon fibers (VGCF), carbon nanotubes (CNTs), and carbon nanofibers (CNFs).

[0192] The proportion of conductive material in the positive electrode layer is, for example, 0.1% by mass or more. If the proportion of conductive material is too small, there is a possibility that the electron conduction pathways in the positive electrode layer are insufficient. On the other hand, the proportion of conductive material in the positive electrode layer is, for example, 5% by mass or less. If the proportion of conductive material is too large, there is a possibility that the proportion of positive electrode active material will be relatively reduced, resulting in a decrease in energy density.

[0193] The positive electrode layer may also contain a binder. Examples of binders include styrene-butadiene rubber (SBR), polyimide (PI), polyacrylic acid (PAA), acrylonitrile-butadiene rubber (NBR), butadiene rubber (BR), polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE), styrene-isoprene-styrene block copolymer (SIS), and ethylene-propylene-diene terpolymer (EPDM).

[0194] The proportion of binder in the positive electrode layer can be, for example, 0.5% by mass or more. If the proportion of binder is too small, there is a possibility that the increase in resistance caused by charging and discharging may not be sufficiently reduced. On the other hand, the proportion of binder in the positive electrode layer can be, for example, 15% by mass or less. If the proportion of binder is too large, there is a possibility that the proportion of positive electrode active material will be relatively reduced, resulting in a decrease in energy density.

[0195] The thickness of the positive electrode layer can be, for example, 0.1 μm or more and 1000 μm or less, or 1 μm or more and 500 μm or less, or 30 μm or more and 100 μm or less.

[0196] The manufacturing method of the positive electrode layer is not particularly limited. For example, a method can be used to obtain a positive electrode slurry by mixing the above-mentioned positive electrode active material, the above-mentioned conductive material, and a solvent, coating the positive electrode slurry onto a positive electrode current collector, and drying it to obtain the positive electrode layer. During the formation of the positive electrode layer, a compaction process can be performed to compact the positive electrode layer in the thickness direction. Examples of compaction processes include roller compaction and plate compaction.

[0197] Examples of solvents include N-methylpyrrolidone (NMP), tetrahydronaphthalene, diisobutyl ketone, butyl butyrate, mesitylene, heptane, dibutyl ether, decane, dodecane, isodecane, and toluene, and may contain two or more of these components.

[0198] Materials used as positive current collectors include, for example, SUS, Cr, Au, Pt, Zn, aluminum, copper, nickel, iron, titanium, and carbon. The thickness of the positive current collector is, for example, 0.1 μm or more and 100 μm or less. The shape of the positive current collector can be foil-like or plate-like. The top view shape of the positive current collector is not particularly limited; for example, it can be circular, elliptical, rectangular, or any polygonal shape. The positive current collector can be constructed with a buffer layer, an elastic layer, or a positive temperature coefficient (PTC) thermistor layer disposed on its surface.

[0199] [negative electrode]

[0200] The negative electrode has a negative electrode layer and may be further equipped with a negative electrode current collector as needed.

[0201] The negative electrode layer is a layer containing at least a negative electrode active material. Additionally, the negative electrode layer may, as needed, contain at least one of an electrolyte, a conductive material, and a binder. The negative electrode layer can have a larger area than the positive electrode layer.

[0202] The negative electrode active material can be in granular or flake form. The average particle size of the negative electrode active material is, for example, 1 μm or more. Alternatively, the average particle size of the negative electrode active material is, for example, 30 μm or less.

[0203] The negative electrode active material may include at least one selected from the group consisting of carbon-based active materials, Li-based active materials, Si-based active materials, Si-C composite materials, and lithium titanate.

[0204] Carbon-based active materials may include at least one material selected from the group consisting of graphite, soft carbon, and hard carbon. "Graphite" is a general term for both natural and artificial graphite. Graphite can also be a mixture of natural and artificial graphite. The mixing ratio (mass ratio) of natural and artificial graphite can be, for example, "natural graphite:artificial graphite = 1:9 to 9:1" or "natural graphite:artificial graphite = 3:7 to 7:3".

[0205] Examples of Li-based active materials include Li, lithium silicate, and Li alloys.

[0206] Examples of Si-based active materials include Si, SiO, and Si alloys.

[0207] Si-C composite materials refer to composite materials of carbon-based active materials (such as graphite) and Si-based active materials (such as Si). For example, Si particles can be dispersed within carbon particles. For example, Si particles can also be dispersed within graphite particles. For example, lithium silicate particles can also be coated with carbon materials (such as amorphous carbon).

[0208] Regarding the electrolyte, conductive material, and binder used in the negative electrode layer, the same substances as those described in the positive electrode layer can be listed.

[0209] The negative electrode layer may also contain a thickener as needed. Examples of thickeners include carboxymethyl cellulose (CMC).

[0210] Materials used as negative electrode current collectors include, for example, SUS, aluminum, copper, nickel, iron, titanium, and carbon. Furthermore, the thickness of the negative electrode current collector varies depending on its shape, ranging from 1 μm to 50 μm. The shape of the negative electrode current collector can be foil-like or plate-like. The top-view shape of the negative electrode current collector is not particularly limited; examples include circular, elliptical, rectangular, and arbitrary polygonal shapes. The negative electrode current collector can be constructed with a buffer layer, an elastic layer, or a PTC thermistor layer disposed on its surface.

[0211] [Electrolyte layer]

[0212] The electrolyte layer is a layer formed between the positive electrode layer and the negative electrode layer, and it contains at least an electrolyte. The electrolyte can be a solid electrolyte or a liquid electrolyte (electrolyte).

[0213] The electrolyte layer may also contain solid electrolytes and electrolyte solutions.

[0214] Solid electrolytes can be listed as the same substances described in the above positive electrode layer.

[0215] Electrolytes can be aqueous or non-aqueous. They can be used alone or in combination.

[0216] Aqueous electrolytes contain water as a main solvent component. That is, based on the total amount of solvent (liquid component) constituting the electrolyte (100 mol%), water can account for more than 50 mol%, especially more than 70 mol%, and can also account for more than 90 mol%. On the other hand, there is no particular upper limit to the proportion of water in the solvent.

[0217] The solvent contains water as the main component, but may also contain solvents other than water. Examples of solvents other than water include one or more selected from ethers, carbonates, nitriles, alcohols, ketones, amines, amides, sulfur-containing compounds, and hydrocarbons. Based on the total amount of the solvent (liquid component) constituting the electrolyte (100 mol%), the solvents other than water may be 50 mol% or less, particularly 30 mol% or less, or even 10 mol% or less.

[0218] The aqueous electrolyte used in this disclosure contains an electrolyte. The electrolyte used in the aqueous electrolyte can be any electrolyte known in the past. Examples of electrolytes include lithium salts, nitrates, acetates, and sulfates of imide compounds. Specific examples of electrolytes include lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(pentafluoroethanesulfonyl)imide (LiBETI), lithium bis(nonafluorobutylsulfonyl)imide, lithium nonafluoro-N-[(trifluoromethane)sulfonyl]butanesulfonamide, lithium N,N-hexafluoro-1,3-propanedisulfonylimide, CH3COOLi, LiPF6, LiBF4, Li2SO4, and LiNO3.

[0219] The concentration of the electrolyte in an aqueous electrolyte solution can be appropriately set according to the required battery characteristics, within a range that does not exceed the saturation concentration of the electrolyte relative to the solvent. This is because the presence of solid electrolyte residues in the aqueous electrolyte solution can hinder the battery reaction.

[0220] For example, when using LiTFSI as the electrolyte, the aqueous electrolyte may contain more than 1 mol of LiTFSI per kilogram of water, particularly more than 5 mol, and may also contain more than 7.5 mol. There is no specific upper limit; for example, it may be less than 25 mol.

[0221] As a non-aqueous electrolyte, a non-aqueous electrolyte containing lithium salt and non-aqueous solvent is usually used.

[0222] Examples of lithium salts include inorganic lithium salts such as LiPF6, LiBF4, LiClO4, and LiAsF6, and organic lithium salts such as LiCF3SO3, LiN(SO2CF3)2 (Li-TFSI), LiN(SO2C2F5)2, and LiC(SO2CF3)3.

[0223] Examples of non-aqueous solvents include ethylene carbonate (EC), propylene carbonate (PC), butenyl carbonate (BC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), γ-butyrolactone, sulfolane, acetonitrile (AcN), dimethoxymethane, 1,2-dimethoxyethane (DME), 1,3-dimethoxypropane, diethyl ether, tetraethylene glycol dimethyl ether (TEGDME), tetrahydrofuran, 2-methyltetrahydrofuran, dimethyl sulfoxide (DMSO), and mixtures thereof. From the viewpoint of ensuring high dielectric constant and low viscosity, mixtures of cyclic carbonate compounds such as EC, PC, and BC with high dielectric constant and high viscosity and chain carbonate compounds such as DMC, DEC, and EMC with low dielectric constant and low viscosity can be used. Mixtures of EC and DEC can also be used.

[0224] The concentration of lithium salt in non-aqueous electrolytes is, for example, 0.3–5 M.

[0225] Non-aqueous electrolytes may also contain ionic liquids. Ionic liquids may contain, for example, at least one of the following groups: sulfonium salts, ammonium salts, pyridinium salts, piperidinium salts, pyrrolidineium salts, morpholinium salts, phosphate salts, imidazolium salts, and their derivatives.

[0226] The electrolyte layer can be a membrane impregnated with the above-mentioned electrolyte and used to prevent the positive electrode layer from contacting the negative electrode layer.

[0227] The membrane material can be a porous membrane, and is not particularly limited. Examples include polyethylene (PE), polypropylene (PP), polyester, polyvinyl alcohol, cellulose, and polyamide resins, with polyethylene and polypropylene being preferred. Furthermore, the membrane can be a single-layer or multi-layer structure. Examples of multi-layer membranes include a PE / PP double-layer structure, or a PP / PE / PP or PE / PP / PE triple-layer structure.

[0228] The diaphragm can also be made of resin nonwoven fabric or glass fiber nonwoven fabric, etc.

[0229] [Solid electrolyte layer]

[0230] The electrolyte layer can be a solid electrolyte layer composed of solids.

[0231] When the electrolyte layer is a solid electrolyte layer, the solid electrolyte layer contains solid electrolyte and may contain binders, etc., as needed.

[0232] Solid electrolytes can be listed as the same substances described in the above positive electrode layer.

[0233] Solid electrolytes can be used alone or in combination with one or more other solid electrolytes. Furthermore, when using two or more solid electrolytes, they can be mixed, or each solid electrolyte can be formed into two or more separate layers to create a multilayer structure.

[0234] The proportion of solid electrolyte in the solid electrolyte layer is not particularly limited. For example, it can be 50% or more by mass, or it can be in the range of 60% or more and less than 100% by mass, or it can be in the range of 70% or more and less than 100% by mass, or it can be 100% by mass. The solid electrolyte layer may also contain less than 1% by mass of electrolyte relative to the total amount of solid electrolyte layer.

[0235] Examples of binders that can be contained in the above-mentioned positive electrode layer include those examples.

[0236] The content of binder in the solid electrolyte layer can be 0% to 10% by mass relative to the total amount of the solid electrolyte layer.

[0237] The thickness of the electrolyte layer can be, for example, 0.1 μm or more and 1000 μm or less, or 0.1 μm or more and 500 μm or less, or 0.1 μm or more and 100 μm or less.

[0238] The battery disclosed herein also includes a constraint clamp that applies constraint pressure to the positive electrode layer, the electrolyte layer, and the negative electrode layer along the thickness direction. In particular, when the electrolyte layer is a solid electrolyte layer, constraint pressure can be applied to form good ion conduction paths and electron conduction paths. The constraint pressure can be, for example, 0.1 MPa or more, 1 MPa or more, or 5 MPa or more. On the other hand, the constraint pressure can be, for example, 100 MPa or less, 50 MPa or less, or 20 MPa or less.

[0239] [Battery]

[0240] The type of battery disclosed herein is not particularly limited, but a typical example is a lithium-ion battery. Furthermore, the battery disclosed herein can be a liquid battery with an electrolyte layer containing an electrolyte solution, or a solid battery with an electrolyte layer containing a solid electrolyte. A solid battery can be a semi-solid battery or a fully solid battery. In this disclosure, a semi-solid battery is a battery whose electrolyte layer contains solid components such as inorganic solid electrolytes and liquid components (e.g., solvents and electrolyte solutions). In this disclosure, a fully solid battery is a battery whose electrolyte layer contains only solid components such as inorganic solid electrolytes as the electrolyte. Additionally, the battery disclosed herein can be a primary battery or a secondary battery, preferably a secondary battery. This is because secondary batteries can be repeatedly charged and discharged, making them useful, for example, as automotive batteries.

[0241] The shape of the battery is not particularly limited; for example, it can be button-shaped, cylindrical, square, sheet-shaped, push-button-shaped, flat, or stacked.

[0242] A battery stack consisting of multiple stacked batteries can be either unipolar or bipolar.

[0243] Batteries are used in various applications, including as power sources for vehicles such as hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), battery electric vehicles (BEVs), gasoline vehicles, and diesel vehicles. They are particularly preferred as drive power sources for HEVs, PHEVs, or BEVs. Furthermore, batteries can be used as power sources for mobile bodies other than vehicles (e.g., railways, ships, aircraft) and for electrical products such as information processing devices.

[0244] It should be noted that this disclosure is not limited to the embodiments described above. The embodiments described above are merely illustrative, and solutions having substantially the same structure and achieving the same effect as the technical concept described in the claims of this disclosure are also included within the technical scope of this disclosure.

[0245] [Example]

[0246] (Example 1)

[0247] Synthesis of transition metal hydroxides

[0248] NiSO4, CoSO4, and MnSO4 were dissolved in ion-exchanged water to prepare a raw material aqueous solution. The molar ratio of Ni, Co, and Mn in the raw material aqueous solution was set as Ni:Co:Mn = 80:10:10. The concentration of the raw material aqueous solution (the proportion of all raw materials to the raw material aqueous solution) was 30% by mass.

[0249] <Hydrothermal Synthesis (Crystallization)>

[0250] A certain amount of NH3 aqueous solution was added to the reaction vessel, and nitrogen was replaced in the reaction vessel under stirring. NaOH aqueous solution was added to the reaction vessel to maintain an alkaline pH (pH=12), and while maintaining a constant temperature, the above-mentioned raw material aqueous solution and NH3 aqueous solution were added dropwise to precipitate the transition metal hydroxide. The reaction temperature was set at 60℃, and the reaction time was set at 10 hours.

[0251] <Filtering>

[0252] After hydrothermal synthesis, the transition metal hydroxides are dispersed using ion-exchanged water for washing. The washed transition metal hydroxides are then filtered and removed.

[0253] <Drying>

[0254] The transition metal hydroxide was dried at 120°C for 16 hours to evaporate the moisture.

[0255] Synthesis of positive electrode active materials

[0256]

[0257] The dried transition metal hydroxide was mixed with LiOH, a lithium compound used as a Li source, using an agate mortar to obtain a mixture.

[0258] The mixture was prepared such that the molar ratio (Li / NCM ratio) of the lithium compound relative to the total stoichiometry (NCM) of Ni, Co, and Mn contained in the transition metal hydroxide reached 1.1.

[0259] <First Stage Firing>

[0260] The obtained mixture was calcined in a furnace at 1000℃ under an oxygen atmosphere for 10 hours to synthesize the positive electrode active material (Li). 1.1 Ni 0.8 Co 0.1 Mn 0.1 O2), to obtain the first stage of fired product.

[0261] <First Stage Crushing>

[0262] The first-stage fired material is pulverized using a jet mill to achieve the specified particle size.

[0263] <Spray drying>

[0264] Add 100 ml of ion-exchanged water and 0.5 g of Mn(NO3)2 to a beaker, and while stirring, add 30 g of the first-stage calcined material to obtain a slurry. Spray dry the slurry using a spray dryer to obtain the dried product. Here, the spray dryer's inlet temperature is 130℃, the inlet pressure is 2.0 MPa, and the nozzle pressure is 0.2 MPa.

[0265] <Second Stage Firing>

[0266] The dried material was calcined in a furnace at 100°C in an oxygen atmosphere for 10 hours to obtain the second-stage calcined product of the positive electrode active material.

[0267] <Second Stage Crushing>

[0268] The second-stage calcined material is pulverized using a jet mill to pulverize the positive electrode active material, which is the second-stage calcined material, to a specified particle size, thereby obtaining positive electrode active material particles.

[0269] (Example 2)

[0270] Except that the air inlet temperature of the spray dryer was set to 100°C in the above <Spray Drying> section, the positive electrode active material was prepared in the same manner as in Example 1.

[0271] (Comparative Example 1)

[0272] In the above-mentioned [synthesis of positive electrode active material], the <spray drying>, <second stage calcination>, and <second stage pulverization> are not performed. The particles of the first stage calcined material obtained in the <first stage pulverization> of the [synthesis of positive electrode active material] are used as the positive electrode active material. Otherwise, the positive electrode active material is prepared in the same way as in Example 1.

[0273] (Comparative Example 2)

[0274] Except that the air inlet temperature of the spray dryer was set to 200°C in the above <Spray Drying> section, the positive electrode active material was prepared in the same manner as in Example 1.

[0275] [TEM-EDX Analysis]

[0276] The positive electrode active materials of Examples 1-2 and Comparative Examples 1-2 were subjected to TEM-EDX line scan analysis, and the following results were obtained.

[0277] Figure 3The spectrum of the positive electrode active material of Example 1 obtained by TEM-EDX is shown. Figure 3 P1 is the first peak value, and P2 is the second peak value.

[0278] When observing the positive electrode active materials of Examples 1 and 2 by TEM-EDX, a first peak was observed in a region extending 2.7 nm from the surface of the positive electrode active material particles toward the center in the range of 690 eV to 700 eV. Furthermore, a second peak was observed in a region extending from a depth of 0.9 nm from the surface of the positive electrode active material particles toward the center in the range of 640 eV to 650 eV. Therefore, it was confirmed that the positive electrode active materials of Examples 1 and 2 have a surface layer where the intensity of the first peak is greater than the intensity of the second peak, and a central layer where the intensity of the first peak is less than the intensity of the second peak.

[0279] When the positive electrode active material of Comparative Example 1 was observed by TEM-EDX, no first peak was observed in the range of 690 eV to 700 eV, and a second peak was observed in the entire region of the positive electrode active material particles in the range of 640 eV to 650 eV.

[0280] When the positive electrode active material of Comparative Example 2 was observed by TEM-EDX, no first peak was observed in the range of 690 eV to 700 eV, and a second peak was observed in the entire region of the positive electrode active material particles in the range of 640 eV to 650 eV. The reason for this is presumably that in Comparative Example 2, because the inlet temperature of the spray dryer was set higher than the boiling point of Mn(NO3)2 (130°C), the Mn(NO3)2 vaporized, and no coating layer containing the elements corresponding to the first peak was formed.

[0281] [Fabrication of Battery Cells (Wound Cylindrical Battery Cells)]

[0282] Using the positive electrode active materials of Examples 1-2 and Comparative Examples 1-2, wound cylindrical battery cells of Examples 1-2 and Comparative Examples 1-2 were fabricated.

[0283] Specifically, firstly, using a coating machine (manufactured by Allgood Co., Ltd.) with film thickness adjustment function, a positive electrode composite slurry containing positive electrode active material, acetylene black as a conductive material, and polyvinylidene fluoride as a binder is coated onto the surface of a metal foil serving as the positive electrode current collector. Then, it is dried at 80°C for 5 minutes using a dryer to create a positive electrode with a positive electrode layer on the positive electrode current collector. The composition of the positive electrode composite slurry is as follows: positive electrode active material: conductive material: binder = 88:10:2 by mass.

[0284] On the other hand, using a coating machine (manufactured by Allgood Co., Ltd.) with film thickness adjustment function, a negative electrode composite slurry containing natural graphite as the negative electrode active material, SBR as the binder, and CMC as the thickener is coated onto the surface of a metal foil serving as the negative electrode current collector. Then, it is dried at 80°C for 5 minutes using a dryer to create a negative electrode with a negative electrode layer on the negative electrode current collector.

[0285] Prepare a 1M LiPF6 solution as the electrolyte, which contains LiPF6 as the electrolyte, ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) as solvents, and the volume ratio is EC:DMC:EMC = 3:4:3.

[0286] The above-mentioned positive electrode, separator and negative electrode are stacked, and the separator is immersed in the above-mentioned electrolyte to produce the wound cylindrical battery cells of Examples 1-2 and Comparative Examples 1-2.

[0287] [Evaluation of Battery Cells]

[0288] Each of the prepared wound cylindrical battery cells was subjected to a 100-cycle cycle test, and the IV resistance was measured before and after the cycle test. The cycle test was conducted under the following conditions for 100 cycles.

[0289] <Loop Condition>

[0290] • Voltage range: 3.0V~4.3V

[0291] • C-ratio: 0.3C

[0292] • Mode: CC charge / discharge

[0293] • Temperature: 50℃

[0294] [IV Resistance Measurement]

[0295] Within a voltage range of 3.0V to 4.3V, the upper limit voltage of 4.3V is set to SOC 100%, and voltage adjustment is performed in a way that achieves SOC 50%.

[0296] The voltage drop (V) after 10 seconds of discharge was measured at 0°C under various C-rate conditions of 0.1C, 0.3C, 0.5C, 0.7C, and 1.0C.

[0297] Plot the voltage drop (V) relative to the current value, fit a linear function to the line, and use the slope of the resulting line as the IV resistance.

[0298] [Calculation of the increase rate of IV resistance after 100 cycles]

[0299] The above measurements were performed before and after 100 cycles of the cyclic test, and the change before and after the cyclic test was calculated and taken as the resistance increase rate.

[0300] The increase in IV resistance after 100 cycles (%) = (IV resistance after cycle test) / (IV resistance before cycle test) × 100

[0301] [Determination of Mn dissolution]

[0302] After the cycle test, each battery cell was disassembled, the negative electrode layer was removed, and ICP-MS was performed on the negative electrode layer to determine the Mn content per milligram of negative electrode layer used in the measurement. The results are shown in Table 1.

[0303] The Mn content per milligram of negative electrode layer used in the determination was 1200 ppm / mg in Comparative Example 1, 1150 ppm / mg in Comparative Example 2, 812 ppm / mg in Example 1, and 724 ppm / mg in Example 2. The amount of Mn contained in the negative electrode layer can be considered as the amount of Mn dissolved from the positive electrode active material in the positive electrode layer. It can be seen that, compared with the batteries using the positive electrode active materials of Comparative Examples 1-2, the amount of Mn dissolved from the positive electrode layer is reduced in the batteries using the positive electrode active materials of Examples 1-2.

[0304] [Table 1]

[0305]

[0306] Based on the results shown in Table 1, the following comparative analysis is conducted.

[0307] As shown in Table 1, it can be seen that the batteries using the positive electrode active materials of Examples 1-2 have a smaller resistance increase rate after 100 cycles compared to the batteries using the positive electrode active materials of Comparative Examples 1-2. Therefore, it can be seen that including elements corresponding to the first peak value in the positive electrode active material, especially on the surface side, can reduce the resistance increase rate during battery charging and discharging.

[0308] Explanation of reference numerals in the attached figures

[0309] 10 …Surface

[0310] 11 …First Surface

[0311] 12 …Second Surface

[0312] 20 …Central layer

[0313] 21 …First Central Layer

[0314] 22 …Second Central Layer

[0315] 100 Positive Electrode Active Material

[0316] 200 Positive electrode active material.

Claims

1. A positive electrode active material, In TEM-EDX analysis, the positive electrode active material exhibits a first peak value in the range of above 690 eV and below 700 eV, and a second peak value in the range of above 640 eV and below 650 eV. The positive electrode active material contains Mn element corresponding to the second peak value.

2. The positive electrode active material according to claim 1, wherein, When the region extending from the surface of the positive electrode active material toward the center to a predetermined depth T is designated as the surface layer, and the region extending from the predetermined depth T to the center is designated as the core layer... In the TEM-EDX analysis, the surface layer has a first peak and a second peak, and the peak intensity of the first peak is higher than that of the second peak, and the amount of the element corresponding to the first peak is higher than the amount of Mn element corresponding to the second peak. In the TEM-EDX analysis, the central layer has a first peak and a second peak, and the peak intensity of the second peak is higher than that of the first peak, and the amount of Mn element corresponding to the second peak is higher than that corresponding to the first peak.

3. The positive electrode active material according to claim 1, wherein, When the region extending from the surface of the positive electrode active material toward the center to a predetermined depth T is designated as the surface layer, and the region extending from the predetermined depth T to the center is designated as the core layer... In the TEM-EDX analysis, the surface layer exhibits the first peak but does not have the second peak, and does not contain the Mn element corresponding to the second peak. In the TEM-EDX analysis, the central layer has the second peak value but does not have the first peak value and does not contain any elements corresponding to the first peak value.

4. The positive electrode active material according to claim 1, wherein, When the region extending from the surface of the positive electrode active material toward the center to a predetermined depth T1 is designated as the first surface layer, the region extending from the predetermined depth T1 to a predetermined depth T2 is designated as the second surface layer, the region extending from the predetermined depth T2 to a predetermined depth T3 is designated as the first central layer, and the region extending from the predetermined depth T3 to the center is designated as the second central layer... In the TEM-EDX analysis, the first surface layer has the first peak value but does not have the second peak value and does not contain the Mn element corresponding to the second peak value. In the TEM-EDX analysis, the second surface layer has both the first peak and the second peak, and the peak intensity of the first peak is higher than that of the second peak, and the amount of the element corresponding to the first peak is higher than the amount of Mn corresponding to the second peak. In the TEM-EDX analysis, the first central layer has a first peak and a second peak, and the peak intensity of the second peak is higher than that of the first peak, and the amount of Mn element corresponding to the second peak is higher than that corresponding to the first peak. In the TEM-EDX analysis, the second central layer has the second peak value but does not have the first peak value and does not contain any elements corresponding to the first peak value.

5. The positive electrode active material according to claim 1, wherein, The positive electrode active material further contains Li, Ni, and Co elements.

6. The positive electrode active material according to claim 5, wherein, The positive electrode active material contains 0.1 mol of Mn, relative to the total amount of Ni, Co, and Mn contained in it being 1 mol.

7. A positive electrode layer comprising the positive electrode active material as described in claim 1.

8. A battery comprising a positive electrode layer containing the positive electrode active material as described in claim 1.

9. A method for manufacturing a positive electrode active material, comprising manufacturing the positive electrode active material according to claim 1. include: In the first stage of the firing process, the first mixture of transition metal hydroxide and lithium compound is fired at 700℃~1100℃ to obtain the precursor of the positive electrode active material. The spray drying process includes spray drying the second mixture of the precursor of the positive electrode active material and Mn(NO3)2 using a spray dryer to obtain a dried product; and The second stage involves a firing process, in which the dried material is fired at 100℃ to 130℃ to obtain the positive electrode active material. In the spray drying process, the air inlet temperature of the spray dryer is 100℃~130℃.

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