Positive electrode active material for lithium secondary battery, positive electrode for lithium secondary battery, and lithium secondary battery

Abstract

The present application provides a kind of positive active material for lithium secondary battery, it at least contains Li, Ni, element X and carbon atom, above-mentioned element X is selected from the group consisting of Al, Ti, Nb, B, W, Zr, Mg, Sn and P more than one element, and satisfy following (1) and (2).(1) Cx / Cy≤10(2)0<(Cy / Cz)≤100(In above-mentioned (1) or (2), Cx is the existence amount (mass %) of above-mentioned element X by using X-ray photoelectron spectroscopy method determination.The existence amount (mass %) of above-mentioned carbon atom by using C1s spectrum of X-ray photoelectron spectroscopy method determination is Cy.Cz is the existence amount (mass %) of above-mentioned carbon atom by using combustion-infrared absorption method determination.

Description

Technical Field

[0001] This invention relates to positive electrode active materials for lithium secondary batteries, positive electrodes for lithium secondary batteries, and lithium secondary batteries.

[0002] This application claims priority based on Japanese Patent Application No. 2020-141233, filed on August 24, 2020, the contents of which are incorporated herein by reference. Background Technology

[0003] Lithium metal composite oxides are used as positive electrode active materials for lithium secondary batteries. Lithium secondary batteries are being used not only in small power sources such as mobile phones and laptops, but also in medium and large power sources such as automobiles and energy storage.

[0004] In the manufacture of positive electrode active materials for lithium-ion batteries, carbon atoms sometimes remain in the resulting positive electrode active material. This is because the positive electrode active material contains compounds containing carbon atoms derived from the raw materials used in the manufacturing process. Examples of compounds containing carbon atoms include lithium carbonate.

[0005] If a large amount of carbon-containing compounds remain on the outer surface (especially the surface of the particles) of the positive electrode active material used in lithium-ion batteries, these compounds may decompose during the discharge reaction, producing gas. Furthermore, if carbon-containing compounds come into contact with the electrolyte, the electrolyte may decompose, generating gas. These gases contribute to the degradation of battery performance.

[0006] To suppress the degradation of such battery characteristics, research has been conducted on methods to cover the lithium metal composite oxide contained in the positive electrode active material of lithium secondary batteries with metal or metal oxide.

[0007] For example, Patent Document 1 describes the application of a compound containing tungsten and lithium to the surface of lithium-nickel composite oxide particles. Furthermore, Patent Document 1 describes limiting the amount of lithium carbonate present on the surface of the lithium-nickel composite oxide particles.

[0008] Existing technical documents

[0009] Patent documents

[0010] Patent Document 1: JP-A-2017-134996 Summary of the Invention

[0011] The problem that the invention aims to solve

[0012] On the other hand, there is a demand for positive electrode active materials for lithium secondary batteries that retain carbon atoms even in the positive electrode active material, have high initial discharge capacity, and can improve cycle characteristics.

[0013] The purpose of this invention is to provide a positive electrode material for lithium secondary batteries that has a high initial discharge capacity and excellent cycle characteristics even when it contains carbon atoms, as well as a positive electrode for lithium secondary batteries and a lithium secondary battery containing the positive electrode material for lithium secondary batteries.

[0014] In this specification, "high initial discharge capacity" means an initial discharge capacity of 160 mAh / g or higher, as measured by the method described later. Furthermore, "excellent cycle characteristics" means a cycle retention rate of 72% or higher, as measured by the method described later.

[0015] Methods for solving problems

[0016] This invention includes [1] to

[15] .

[0017] [1] A positive electrode active material for lithium secondary batteries, which contains at least Li, Ni, element X and carbon atoms, wherein the element X is one or more elements selected from the group consisting of Al, Ti, Nb, B, W, Zr, Mg, Sn and P, and satisfies (1) and (2) below.

[0018] (1) Cx / Cy≤10

[0019] (2) 0 < (Cy / Cz) ≤ 100

[0020] (In (1) or (2) above, Cx is the amount of element X present (mass%) as determined by X-ray photoelectron spectroscopy. Cy is the amount of carbon atoms present (mass%) as determined by C1s spectrum obtained by X-ray photoelectron spectroscopy. Cz is the amount of carbon atoms present (mass%) as determined by combustion-infrared absorption method.)

[0021] [2] A positive electrode active material for lithium secondary batteries, which contains at least Li, Ni, element X and carbon atoms, wherein the element X is one or more elements selected from the group consisting of Al, Ti, Nb, B, W, Zr, Mg, Sn and P, and satisfies (1) and (3) below.

[0022] (1) Cx / Cy≤10

[0023] (3) 0 < (Cy / Cz) ≤ 500

[0024] (In (1) or (3) above,

[0025] Cx represents the amount (mass%) of element X obtained by X-ray photoelectron spectroscopy.

[0026] Cy represents the amount (mass%) of the carbon atoms present, determined by the C1s spectrum obtained using X-ray photoelectron spectroscopy.

[0027] Cz represents the amount (by mass%) of the aforementioned carbon atoms, determined by combustion-infrared absorption spectrometry.

[0028] [3] The positive electrode active material for lithium secondary batteries according to [1] or [2], wherein the above-mentioned Cy is 0 < Cy ≤ 50.

[0029] [4] The positive electrode active material for lithium secondary batteries according to any one of [1] to [3], wherein the above Cz is 0 < Cz ≤ 2.

[0030] [5] The positive electrode active material for lithium secondary batteries according to any one of [1] to [4], wherein the above Cz is 0 < Cz ≤ 0.4.

[0031] [6] The positive electrode active material for lithium secondary batteries according to any one of [1] to [5], wherein the above Cx is 0 < Cx ≤ 95.

[0032] [7] The positive electrode active material for lithium secondary batteries according to any one of [1] to [6] is represented by the following compositional formula (I) and further contains carbon atoms.

[0033] Li[Li m (Ni (1-n-p) X n M p ) 1-m O2(I)

[0034] (Where -0.1≤m≤0.2, 0<p<0.6, and 0<n≤0.2. Element M is one or more elements selected from the group consisting of Co, Mn, Fe, Cu, Mo, Zn, Ga, and V.)

[0035] [8] A positive electrode active material for a lithium secondary battery according to any one of [1] to [7], wherein the positive electrode active material for a lithium secondary battery comprises a lithium metal composite oxide and a composite phase, wherein the lithium metal composite oxide contains Li, Ni and one or more elements selected from the group consisting of elements M and Al, and the composite phase contains element X. Wherein, element M is one or more elements selected from the group consisting of Co, Mn, Fe, Cu, Mo, Zn, Ga and V.

[0036] [9] The positive electrode active material for lithium secondary batteries according to any one of [1] to [8] has a BET specific surface area of ​​2.0 m². 2 / g or less.

[0037]

[10] A positive electrode for a lithium secondary battery, comprising any one of [1] to [9] positive electrode active materials for lithium secondary batteries.

[0038]

[11] A lithium secondary battery having the positive electrode for a lithium secondary battery as described in

[10] .

[0039]

[12] A method for manufacturing a positive electrode active material for a lithium secondary battery, comprising the following steps (a), (b) and (c) in sequence.

[0040] Step (a): A step of mixing a metal composite compound containing at least Ni with a lithium compound and calcining it to obtain a lithium metal composite oxide.

[0041] Step (b): A step of mixing the above-mentioned lithium metal composite oxide with a compound containing element X in a ratio of at least 1.0 mol% to at least 5.5 mol% of the total molar amount of element X relative to the total molar amount of metal elements other than lithium atoms contained in the above-mentioned lithium metal composite oxide to obtain a mixture. Element X is one or more elements selected from the group consisting of Al, Ti, Nb, B, W, Zr, Mg, Sn, and P, and the 50% cumulative volume particle size D of the compound containing element X is... 50 (μm) is greater than 0.02μm and less than 90μm.

[0042] Step (c): A step of heat-treating the above mixture in an oxygen-containing atmosphere at a temperature of 200°C or higher and 600°C or lower.

[0043]

[13] The method for manufacturing positive electrode active material for lithium secondary batteries according to

[12] includes the step (a) of mixing a metal composite compound with a lithium compound and calcining it, and crushing the calcined material using a stone mill crusher.

[0044]

[14] The method for manufacturing a positive electrode active material for a lithium secondary battery according to

[12] or

[13] , wherein the above-mentioned step (b) includes a step of mixing a covering material containing element X with a lithium metal composite oxide in water or an atmosphere containing water and carbon dioxide.

[0045]

[15] The method for manufacturing a positive electrode active material for a lithium secondary battery according to any one of

[12] to

[14] , wherein the above-mentioned step (b) includes a step of mixing a covering material containing element X with a lithium metal composite oxide and holding the mixture in water or an atmosphere containing water and carbon dioxide.

[0046] Invention Effects

[0047] According to the present invention, it is possible to provide a positive electrode active material for lithium secondary batteries, a positive electrode for lithium secondary batteries, and a lithium secondary battery that have high initial discharge capacity and excellent cycle characteristics even when carbon atoms are included in the positive electrode active material for lithium secondary batteries. Attached Figure Description

[0048] Figure 1A This is a schematic diagram illustrating an example of a lithium secondary battery.

[0049] Figure 1B This is a schematic diagram illustrating an example of a lithium secondary battery.

[0050] Figure 2 This is a schematic diagram illustrating the stacked structure of an all-solid-state lithium-ion secondary battery.

[0051] Figure 3 This is a schematic diagram showing the overall structure of an all-solid-state lithium-ion secondary battery. Detailed Implementation

[0052] In this specification, the abbreviation for Metal Composite Compound is sometimes referred to as "MCC".

[0053] In this specification, the term "CAM" is sometimes used as an abbreviation for "Cathode Active Material for lithium secondary batteries".

[0054] In this specification, lithium metal composite oxide is sometimes referred to as "LiMO".

[0055] <Positive electrode active materials for lithium secondary batteries>

[0056] The CAM of this embodiment contains at least Li, Ni, element X, and carbon atoms. Element X is one or more elements selected from the group consisting of Al, Ti, Nb, B, W, Zr, Mg, Sn, and P.

[0057] It should be noted that in this specification, Ni does not refer to nickel metal, but to nickel atoms. Similarly, Co, Al, and Li refer to cobalt atoms, aluminum atoms, and lithium atoms, respectively.

[0058] The carbon atoms contained in the CAM of this embodiment are preferably derived from compounds containing carbon atoms, such as lithium carbonate, lithium bicarbonate, organolithium compounds, and hydrocarbons. The compounds containing carbon atoms are compounds contained in the raw materials used in the manufacture of the CAM, or compounds obtained through reactions during the manufacture of the CAM.

[0059] In this embodiment, the CAM preferably has carbon atoms on its surface, and preferably has carbon atoms on both its surface and interior. The LiMO contained in the CAM preferably has carbon atoms on its surface, and preferably has carbon atoms on both its surface and interior.

[0060] In this embodiment, CAM is a powder.

[0061] In this embodiment, "X-ray photoelectron spectroscopy" is referred to as "XPS".

[0062] XPS allows for the analysis of the constituent elements and electronic states of the surface portion of particles within a CAM by measuring the energy of photoelectrons generated when the surface of particles in a CAM is irradiated with X-rays. The bonding energy of photoelectrons emitted from the surface of CAM particles when irradiated with AlKα rays as excitation X-rays is analyzed. XPS enables the analysis of the surface state of particles within a CAM.

[0063] X-ray photoelectron spectroscopy analysis

[0064] As an X-ray photoelectron spectroscopy device used in measurements utilizing XPS, specifically the K-Alpha manufactured by ThermoFisher Scientific can be used.

[0065] Specifically, the spectra of C1s and element X were measured. For the X-ray source, AlKα rays were used, and a neutralization gun (accelerating voltage 0.3V, current 100μA) was used during the measurement to neutralize the charged particles.

[0066] The spectral peaks of element X are the spectral peaks of aluminum 2p, titanium 2p, niobium 3d, boron 1s, tungsten 4f, zirconium 3d, magnesium 2p, tin 3d and phosphorus 2p.

[0067] The measurement conditions were set as follows: spot diameter = 400 μm, pass energy = 50 eV, step size = 0.1 eV, and dwell time = 500 ms. The peak areas (described later) were calculated using the Avantage data system manufactured by Thermo Fisher Scientific for the obtained XPS spectra. In the C1s spectrum, the peak attributed to surface contaminant hydrocarbons was set to 284.6 eV for charge correction.

[0068] Cx, Cy, and Cz

[0069] The presence (mass%) of element X obtained by measurement using XPS, i.e., the presence (mass%) of element X calculated based on the spectral peak area of ​​element X obtained by measuring CAM using XPS, is set as Cx.

[0070] The spectral peaks for element X are aluminum 2p, titanium 2p, niobium 3d, boron 1s, tungsten 4f, zirconium 3d, magnesium 2p, tin 3d, and phosphorus 2p.

[0071] The measurement conditions for XPS only need to be appropriately adjusted to conditions that can measure most of the particles contained in CAM. As an example, the conditions can be listed as follows: X-ray irradiation diameter of 400 μm, pass energy of 50 eV, step of 0.1 eV, and dwell time of 500 ms.

[0072] For the obtained XPS spectra, the spectral peak area of ​​element X was calculated using the Avantage data system manufactured by Thermo Fisher Scientific, and the abundance of element X was calculated based on it. In this embodiment, the C1s peak was set to 284.6 eV for charge correction.

[0073] XPS can determine the amount of element X present in the surface region of particles within the range of X-ray irradiation. The total amount of element X present in the surface region of particles within the range of X-ray irradiation is called the measured value.

[0074] The amount of carbon atoms present (mass%) determined by C1s spectra obtained through X-ray photoelectron spectroscopy, specifically the amount of carbon atoms present (mass%) based on the peak area at a bonding energy of 290 ± 5 eV in the C1s spectrum obtained by XPS measurement of CAM, is defined as Cy. The peak at a bonding energy of 290 ± 5 eV indicates the presence of carbon atoms from (-CO3) sources.

[0075] XPS can determine the amount of carbon atoms present in the surface region of particles within the range of X-ray irradiation. The total amount of carbon atoms present in the surface region of particles within the range of X-ray irradiation is called the measured value.

[0076] In this embodiment, the amount of carbon atoms (mass%) obtained when CAM is measured by combustion-infrared absorption method is set as Cz. The combustion-infrared absorption method is performed using the following method. According to the combustion-infrared absorption method, the amount of carbon atoms contained in the entirety of CAM particles can be determined.

[0077] The combustion-infrared absorption method is carried out by heating CAM in a tubular resistance furnace to a specified temperature in an oxygen stream to induce combustion. The carbon-containing gaseous components such as carbon dioxide or carbon monoxide produced by combustion are measured using an infrared detector, which allows for the determination of the amount of carbon contained in the CAM particles as a whole.

[0078] Specifically, the EMIA-810W (Horiba Manufacturing Co., Ltd.) can be used as a device for the combustion-infrared absorption method.

[0079] In CAM, Cx, Cy and Cz satisfy the following (1) and (2).

[0080] (1) Cx / Cy≤10

[0081] (2) 0 < (Cy / Cz) ≤ 100 [(1)]

[0083] The value of “Cx” is the amount (mass%) of element X present in the surface region of the particles contained in the CAM.

[0084] The value of “Cy” is the amount (mass%) of carbon atoms present in the surface region of the particles contained in the CAM.

[0085] The value of “Cx / Cy” refers to the ratio of the amount (mass%) of element X to carbon atoms in the surface region of the particles contained in the CAM.

[0086] If the value of "Cx / Cy" is below 10, it can be inferred that an ion-conducting phase has formed in the surface region of the particles contained in the CAM. The "ion-conducting phase" is a phase containing carbon atoms and element X that promotes the movement of lithium ions. If an ion-conducting phase forms in the surface region of the particles contained in the CAM, the initial discharge capacity of the battery is likely to be higher, and the cycle characteristics are likely to be improved.

[0087] On the other hand, if the value of "Cx / Cy" exceeds 10, it can be inferred that a resistive phase that hinders the movement of lithium ions is likely to form in the surface region of the particles contained in the CAM. In this case, the initial discharge capacity of the manufactured battery is likely to be low, and the cycle characteristics are also likely to be poor.

[0088] Here, the surface region of the particles contained in CAM refers to the region that can be analyzed by XPS measurement of the constituent elements or electronic states. Specifically, it refers to the region extending from the outermost surface to the depth that can be measured by XPS in the direction from the outermost surface toward the center of the particle.

[0089] The value of “Cx / Cy” is preferably 9.5 or less, more preferably 9.0 or less, and particularly preferably 8.5 or less. Examples of lower limits for “Cx / Cy” include 0.10 or more, 0.15 or more, and 0.20 or more.

[0090] The upper and lower limits of “Cx / Cy” can be combined arbitrarily. As examples of combinations, “Cx / Cy” can be 0.10 or higher and 10 or lower, 0.15 or higher and 9.5 or lower, 0.20 or higher and 9.0 or lower, and 0.20 or higher and 8.5 or lower. [(2)]

[0092] The value of “Cz” is the amount of carbon atoms present in the total number of particles contained in CAM (mass%).

[0093] The value of “Cy / Cz” refers to the ratio of the amount of carbon atoms (mass%) present in the surface region of the particles contained in the CAM to the amount of carbon atoms (mass%) present in the total particles contained in the CAM.

[0094] The smaller the Cy / Cz value, the less carbon atoms are present on the surface of the particles in the CAM (Cy / Cz-Carbon Module) compared to the amount of carbon atoms inside the particles. If the Cy / Cz value is below 100, it can be inferred that the amount of carbon atoms on the surface of the particles in the CAM is sufficiently small. Therefore, it becomes less likely for the electrolyte to decompose and generate gas due to the reaction of carbon-containing compounds with the electrolyte. As a result, the battery's cycle characteristics become less prone to degradation.

[0095] The "Cy / Cz" is preferably 80 or less, and more preferably 60 or less. Examples of lower limits for "Cy / Cz" include 1.0 or more, 2.5 or more, 5.0 or more, and 5.3 or more.

[0096] The upper and lower limits of “Cy / Cz” can be combined arbitrarily. As examples of combinations, “Cy / Cz” can be listed as 1.0 or higher and 80 or lower, 2.5 or higher and 70 or lower, 5.0 or higher and 60 or lower, and 5.3 or higher and 60 or lower.

[0097] Since the CAM that satisfies (1) and (2) has the above-mentioned ion-conducting phase fully formed in the surface region of the particles, it can improve the first discharge capacity of the manufactured battery and improve the cycle characteristics.

[0098] In one embodiment of the present invention, Cx, Cy and Cz in CAM satisfy (1) above and (3) below.

[0099] (3) 0 < (Cy / Cz) ≤ 500

[0100] In (3), Cy is the amount of carbon atoms present (mass%) determined by the C1s spectrum obtained by X-ray photoelectron spectroscopy.

[0101] Cz represents the amount (by mass%) of the aforementioned carbon atoms, determined by combustion-infrared absorption spectrometry. [(3)]

[0103] The explanations regarding Cy and Cz are the same as those in (2) above.

[0104] If the "Cy / Cz" value is below 500, it can be inferred that the amount of carbon atoms present in the surface region of the particles contained in the CAM is sufficiently low. Therefore, it becomes less likely for the electrolyte to decompose and generate gas due to the reaction of compounds containing carbon atoms with the electrolyte. As a result, the battery's cycle characteristics become less prone to degradation.

[0105] The "Cy / Cz" value is preferably 400 or less, more preferably 375 or less, and even more preferably 350 or less. Examples of lower limits for "Cy / Cz" include 5.0 or more, 10 or more, 20 or more, and 25 or more.

[0106] The upper and lower limits of “Cy / Cz” can be combined arbitrarily. As examples of combinations, “Cy / Cz” can be listed as 5.0 or higher and 400 or lower, 10 or higher and 375 or lower, 20 or higher and 350 or lower, and 25 or higher and 350 or lower.

[0107] Since the CAM that satisfies (1) and (3) has the above-mentioned ion-conducting phase fully formed in the surface region of the particles, it can improve the first discharge capacity of the manufactured battery and improve the cycle characteristics.

[0108] Cx is preferably 0 < Cx ≤ 95. Furthermore, Cx is preferably 0.1 or more, more preferably 2.5 or more, and even more preferably 5.0 or more. Cx is preferably 85 or less, more preferably 75 or less, and even more preferably 65 or less.

[0109] The upper and lower limits of Cx can be combined arbitrarily.

[0110] As examples of combinations, Cx can be listed as 0.1 or higher and 85 or lower, 2.5 or higher and 75 or lower, and 5.0 or higher and 65 or lower.

[0111] Cy is preferably 0 < Cy ≤ 50. Furthermore, Cy is preferably 1.0 or more, more preferably 2.0 or more, even more preferably 3.0 or more, and particularly preferably 4.6 or more. Cy is preferably 48 or less, more preferably 45 or less, and even more preferably 40 or less.

[0112] The upper and lower limits of Cy can be combined arbitrarily.

[0113] As examples of combinations, Cy can be listed as 1.0 and above and 48 and below, 2.0 and above and 45 and below, 3.0 and above and 40 and below, and 4.6 and above and 40 and below.

[0114] Cz is preferably 0 < Cz ≤ 2. Furthermore, Cz is preferably 0.1 or more, more preferably 0.15 or more, and even more preferably 0.25 or more. Cz is preferably 2.0 or less, more preferably 1.8 or less, even more preferably 1.6 or less, and particularly preferably 1.5 or less.

[0115] The upper and lower limits of Cz can be combined arbitrarily.

[0116] As examples of combinations, Cz can be listed as greater than 0 and less than 2.0, greater than 0.1 and less than 1.8, greater than 0.15 and less than 1.6, and greater than 0.25 and less than 1.5.

[0117] In one embodiment of the present invention, Cz is preferably 0 < Cz ≤ 0.4. Furthermore, Cz is preferably 0.01 or more, more preferably 0.03 or more, and even more preferably 0.05 or more. Cz is preferably 0.4 or less, more preferably 0.38 or less, even more preferably 0.35 or less, and particularly preferably 0.3 or less.

[0118] The upper and lower limits of Cz can be combined arbitrarily.

[0119] As examples of combinations, Cz can be listed as greater than 0 and less than 0.4, greater than 0.01 and less than 0.38, greater than 0.03 and less than 0.35, and greater than 0.05 and less than 0.3.

[0120] If Cx, Cy, and Cz are within the ranges mentioned above, the initial discharge capacity of the manufactured battery can be further improved, and the cycle characteristics can be further improved.

[0121] The CAM preferably contains both LiMO and a composite phase. Furthermore, it is particularly preferred that the composite phase is present in the surface region of the LiMO. The surface region of the LiMO may be covered by the composite phase, or the composite phase may be dispersed within a portion of the surface region of the LiMO, with a portion of the LiMO surface exposed.

[0122] It should be noted that the "surface region of LiMO" refers to the outermost surface of the LiMO particle and the region extending from the outermost surface toward the center of the particle to a depth of approximately 10 nm.

[0123] As a composite phase, phases with lithium-ion conductivity can be listed.

[0124] Composite phases are phases with compositions different from CAMs. Examples include composite metal oxides that contain Li and element X but do not contain element M.

[0125] The composite phase is considered to be the sum of the ionicly conductive phase and the resistive phase. As mentioned above, if the value of "Cx / Cy" is less than 10, the ionicly conductive phase becomes more readily formed in the surface region of the particles contained in the CAM, thus increasing the contribution of the ionicly conductive phase, and the composite phase behaves as the ionicly conductive phase.

[0126] On the other hand, if the value of "Cx / Cy" exceeds 10, a resistive phase that hinders the movement of lithium ions becomes more likely to form in the surface region of the particles contained in the CAM. Therefore, the contribution of the resistive phase increases, and the composite phase exhibits a resistive phase.

[0127] LiMO preferably contains at least lithium atoms, Ni, and one or more elements selected from the group consisting of elements M and Al. Element M is one or more elements selected from the group consisting of Co, Mn, Fe, Cu, Mo, Zn, Ga, and V. Furthermore, the composite phase preferably contains element X, and more preferably contains element X and carbon atoms.

[0128] The CAM having LiMO and the composite phase is preferably a substance represented by the following compositional formula (I) and further containing carbon atoms.

[0129] Li[Li m (Ni (1-n-p) X n M p ) 1-m O2(I)

[0130] (Where -0.1≤m≤0.2, 0<p<0.6, and 0<n≤0.2. Element M is one or more elements selected from the group consisting of Co, Mn, Fe, Cu, Mo, Zn, Ga, and V.)

[0131] In composition (I), from the viewpoint of improving cycle characteristics, m is preferably -0.001 or more, more preferably -0.0015 or more, and particularly preferably -0.002 or more. Furthermore, from the viewpoint of obtaining a lithium secondary battery with high discharge rate characteristics, m is preferably 0.1 or less, more preferably 0.08 or less, and particularly preferably 0.06 or less.

[0132] The upper and lower limits of m can be combined arbitrarily.

[0133] The preferred value of m is -0.001≤m≤0.1, and more preferably -0.002≤m≤0.06.

[0134] In the composition formula (I), from the viewpoint of obtaining a lithium secondary battery with high discharge rate characteristics, it is preferable that 0 < n + p < 0.6, more preferably that 0 < n + p ≤ 0.5, further preferably that 0 < n + p ≤ 0.25, and even more preferably that 0 < n + p ≤ 0.2.

[0135] In composition formula (I), from the viewpoint of obtaining a lithium secondary battery with low internal resistance, p is more preferably 0.05 or more, and particularly preferably 0.08 or more. Furthermore, from the viewpoint of obtaining a lithium secondary battery with high thermal stability, p is preferably 0.5 or less, and particularly preferably 0.4 or less.

[0136] The upper and lower limits of p can be combined arbitrarily. As examples of combinations, p can be 0.05 or higher and 0.5 or lower, or 0.08 or higher and 0.4 or lower.

[0137] In composition (I), from the viewpoint of improving cycle characteristics, n is more preferably 0.0002 or more, particularly preferably 0.0005 or more. Furthermore, it is preferably 0.15 or less, more preferably 0.13 or less, and particularly preferably 0.1 or less.

[0138] The upper and lower limits of n can be combined arbitrarily.

[0139] The preferred value for n is 0.0002 ≤ n ≤ 0.15.

[0140] The preferred combination of x, n and p is 0 ≤ m ≤ 0.1, 0.08 ≤ p ≤ 0.4, and 0.0002 ≤ n ≤ 0.15.

[0141] [Composition Analysis]

[0142] Compositional analysis of CAM or LiMO can be performed by dissolving the obtained CAM or LiMO powder in hydrochloric acid and then using an ICP emission spectrometer.

[0143] As an ICP emission spectroscopy analysis device, for example, the SPS3000 manufactured by SII Nano Technology Co., Ltd. can be used.

[0144] In this embodiment, the composition of the composite phase can be confirmed by STEM-EDX elemental line analysis of particle cross-sections using CAM, inductively coupled plasma optical emission analysis, and electron beam microscopy. The crystal structure of the composite phase can be confirmed by powder X-ray diffraction and electron beam diffraction.

[0145] The preferred BET specific surface area for CAM is 2.0 m². 2 / g or less, more preferably 1.8m 2 / g or less, more preferably 1.5m 2 / g or less, especially preferably 1.3m 2 / g or less. Furthermore, the preferred BET specific surface area is 0.1m². 2 / g or more, preferably 0.2m 2 / g or more, with 0.3m being particularly preferred. 2 / g or more.

[0146] If the BET specific surface area is below the upper limit mentioned above, the volumetric capacity density of the lithium secondary battery tends to be higher. Furthermore, if it is above the lower limit mentioned above, the discharge rate characteristics of the lithium secondary battery tend to be higher.

[0147] The upper and lower limits of the BET specific surface area can be combined arbitrarily. As an example of a combination, the BET specific surface area could be 0.1 m². 2 / g or more and 2.0m 2 / g or less, 0.2m 2 / g or more and 1.8m 2 / g or less, 0.3m 2 / g or more and 1.5m 2 / g or less, 0.3m 2 / g or more and 1.3m 2 / g or less.

[0148] [Determination of BET specific surface area]

[0149] The BET specific surface area of ​​CAM can be measured using a BET specific surface area measuring device. For example, Macsorb (registered trademark) manufactured by MOUNTECH can be used as a BET specific surface area measuring device. When measuring the BET specific surface area of ​​powdered CAM, as a pretreatment, drying at 105°C for 30 minutes under a nitrogen atmosphere is preferred.

[0150] (Layered structure)

[0151] In this embodiment, the crystal structure of CAM is a layered structure, more preferably a hexagonal crystal structure or a monoclinic crystal structure.

[0152] The hexagonal crystal structure is assigned to the following crystal groups: P3, P31, P32, R3, P-3, R-3, P312, P321, P3112, P3121, P3212, P3221, R32, P3m1, P31m, P3c1, P31c, R3m, R3c, P-31m, P-31c, P-3m1, P-3c1, R-3m, R-3c, P6, P61, P65, P Any space group formed by the group consisting of P62, P64, P63, P-6, P6 / m, P63 / m, P622, P6122, P6522, P6222, P6422, P6322, P6mm, P6cc, P63cm, P63mc, P-6m2, P-6c2, P-62m, P-62c, P6 / mmm, P6 / mcc, P63 / mcm, and P63 / mmc.

[0153] Furthermore, the crystal structure of the monoclinic form belongs to any one of the space groups selected from the group consisting of P2, P21, C2, Pm, Pc, Cm, Cc, P2 / m, P21 / m, C2 / m, P2 / c, P21 / c, and C2 / c.

[0154] In order to obtain lithium secondary batteries with high initial discharge capacity, the crystal structure is particularly preferred to be a hexagonal crystal structure belonging to space group R-3m or a monoclinic crystal structure belonging to C2 / m.

[0155] Methods for determining crystal structure

[0156] The crystal structure of CAM can be determined by observation using a powder X-ray diffraction apparatus (such as Rigaku Ultima IV manufactured by Rigaku Corporation).

[0157] <CAM Manufacturing Method 1>

[0158] The CAM manufacturing method of this embodiment is a method of sequentially performing the manufacturing process of MCC, the manufacturing process of LiMO, and the manufacturing process of CAM.

[0159] In the manufacture of LiMO, firstly, an MCC containing a metal element other than lithium, namely Ni, and an element M as an optional metal and Al as an optional metal is prepared.

[0160] Next, the MCC containing Ni, element M, and Al is preferably calcined with a lithium compound. The MCC containing Ni, element M, and Al is preferably a metal composite hydroxide containing Ni, element M, and Al, or a metal composite oxide containing Ni, element M, and Al.

[0161] (Manufacturing process of MCC)

[0162] MCC can be manufactured using either the commonly known batch coprecipitation method or the continuous coprecipitation method. The following detailed description uses a metal complex hydroxide containing Ni, Co, and Al as an example to illustrate its manufacturing method.

[0163] First, Ni is produced by reacting nickel salt solution, cobalt salt solution, aluminum salt solution, and complexing agent through a co-precipitation method, particularly the continuous method described in JP-A-2002-201028. a Co b Al c (OH)2 (where a+b+c=1) represents a metal complex hydroxide.

[0164] The nickel salt used as the solute in the above-mentioned nickel salt solution is not particularly limited, but for example, any one or more of nickel sulfate, nickel nitrate, nickel chloride and nickel acetate can be used.

[0165] The cobalt salt, or cobalt salt, can be one or more of the following: cobalt sulfate, cobalt nitrate, cobalt chloride, and cobalt acetate.

[0166] The solute used in the above aluminum salt solution is the aluminum salt, such as aluminum sulfate or sodium aluminate.

[0167] The above metal salts are used in conjunction with the above Ni. a Co b Al c The (OH)2 is used in a proportion corresponding to its composition. Furthermore, water is used as a solvent.

[0168] A complexing agent is a compound that can form a complex with Ni, Co, and Al ions in aqueous solution. Examples include ammonium ion donors (ammonium salts such as ammonium hydroxide, ammonium sulfate, ammonium chloride, ammonium carbonate, and ammonium fluoride), hydrazine, ethylenediaminetetraacetic acid, nitric acid triacetic acid, uracil diacetic acid, and glycine. The solution may also be without a complexing agent. In cases where a complexing agent is included, the amount of the complexing agent in the mixture containing the nickel salt solution, cobalt salt solution, manganese salt solution, and the complexing agent is, for example, a molar ratio relative to the total number of moles of the metal salts greater than 0 and less than 2.0.

[0169] In the coprecipitation method, to adjust the pH of the mixture containing nickel salt solution, cobalt salt solution, manganese salt solution, and complexing agent, an alkaline aqueous solution is added to the mixture before the pH changes from alkaline to neutral. Sodium hydroxide or potassium hydroxide can be used as the alkaline aqueous solution.

[0170] It should be noted that the pH value in this specification is defined as the value measured when the temperature of the mixture is 40°C. The pH of the mixture is measured when the temperature of the mixture sampled from the reaction tank reaches 40°C.

[0171] If the temperature of the sampled mixture is below 40°C, the mixture is heated until it reaches 40°C, at which point the pH is measured.

[0172] If the temperature of the sampled mixture is above 40°C, the mixture is cooled and the pH is measured when it reaches 40°C.

[0173] If a complexing agent is continuously supplied to the reaction tank in addition to the aforementioned nickel salt solution, cobalt salt solution, and aluminum salt solution, then Ni, Co, and Al react to form Ni. a Co b Al c (OH)2.

[0174] During the reaction, the temperature of the reaction tank is controlled within a range of, for example, above 20°C and below 80°C, preferably above 30°C and below 70°C.

[0175] Furthermore, during the reaction, the pH value in the reaction tank is controlled within a range, for example, pH 9 or higher and pH 13 or lower, preferably pH 11 or higher and pH 13 or lower.

[0176] The substances in the reaction tank can be stirred and mixed appropriately.

[0177] The reaction tanks used in continuous coprecipitation methods can be of the overflow type, which is used to separate the reaction precipitates formed.

[0178] The reaction vessel can also contain an inert atmosphere. An inert atmosphere can suppress the aggregation of elements that are more easily oxidized than nickel, resulting in a homogeneous metal composite hydroxide.

[0179] In addition, an inert atmosphere can be maintained in the reaction tank, and in the presence of a moderate oxygen-containing atmosphere or oxidant.

[0180] Increasing the amount of transition metal oxidation results in a larger specific surface area. The oxygen in the oxygen-containing gas or the oxidizing agent only needs to contain enough oxygen atoms to oxidize the transition metal. As long as a large amount of oxygen atoms is not introduced, the inert atmosphere within the reaction vessel can be maintained. It should be noted that when controlling the atmosphere within the reaction vessel using a specific gas, simply introducing the prescribed gas into the reaction vessel or directly bubbling the reaction liquid is sufficient.

[0181] In addition to controlling the conditions mentioned above, various gases, such as inert gases like nitrogen, argon, and carbon dioxide, oxidizing gases like air and oxygen, or mixtures thereof, can be supplied to the reaction tank to control the oxidation state of the obtained reaction products.

[0182] As compounds for oxidizing the obtained reaction products, peroxides such as hydrogen peroxide, peroxide salts such as permanganate, perchlorate, hypochlorite, nitric acid, halogen, ozone, etc. can be used.

[0183] As compounds to reduce the obtained reaction products, organic acids such as oxalic acid and formic acid, sulfites, hydrazine, etc., can be used.

[0184] After the above reaction, the obtained reaction product is washed with water and dried to obtain MCC. In this embodiment, nickel-cobalt-aluminum metal composite hydroxide can be obtained as MCC. In addition, if impurities from the mixture remain in the reaction product after washing with water alone, the reaction product can be washed with weak acid water or an alkaline solution containing sodium hydroxide or potassium hydroxide as needed.

[0185] It should be noted that in the above example, nickel-cobalt-aluminum metal composite hydroxide was manufactured as an MCC, but nickel-cobalt-aluminum metal composite oxide can also be prepared.

[0186] For example, nickel-cobalt-aluminum metal composite oxides can be prepared by calcining nickel-cobalt-aluminum metal composite hydroxides. The calcination time is preferably set to a total time of 1 hour or more and 30 hours or less, from the start of heating to the attainment and holding of the temperature. The heating rate for reaching the maximum holding temperature is preferably 180°C / hour or more, more preferably 200°C / hour or more, and particularly preferably 250°C / hour or more.

[0187] The maximum holding temperature mentioned in this specification is the highest temperature at which the atmosphere inside the firing furnace is held during the firing process; it refers to the firing temperature during the firing process. In the case of a formal firing process with multiple heating steps, the maximum holding temperature refers to the highest temperature in each heating step.

[0188] The heating rate in this manual is calculated from the time from the start of heating in the firing apparatus to the time until the maximum holding temperature is reached, and the temperature difference in the firing furnace of the firing apparatus from the initial temperature to the maximum holding temperature.

[0189] (LiMO manufacturing process)

[0190] After drying the above-mentioned MCC, it is mixed with lithium compounds.

[0191] LiMO is obtained by calcining a mixture containing MCC and lithium compounds.

[0192] As a lithium compound, any one or more of lithium carbonate, lithium nitrate, lithium acetate, lithium hydroxide, lithium hydroxide hydrate, and lithium oxide can be used in combination.

[0193] Among these lithium compounds, lithium hydroxide or lithium acetate reacts with carbon dioxide in the air and may contain a few percent lithium carbonate.

[0194] In this embodiment, the drying conditions for the MCC are not particularly limited. When the MCC is a metal composite oxide or a metal hydroxide, the drying conditions can be any of the conditions described in 1) to 3) below.

[0195] 1) Conditions under which metal composite oxides or metal composite hydroxides are not oxidized or reduced. Specifically, drying conditions for metal composite oxides to maintain their metal composite oxide state, and drying conditions for metal composite hydroxides to maintain their metal composite hydroxide state.

[0196] 2) Conditions for the oxidation of metal complex hydroxides. Specifically, the drying conditions for the oxidation of metal complex hydroxides into metal complex oxides.

[0197] 3) Conditions for the reduction of metal complex oxides. Specifically, the drying conditions under which metal complex oxides are reduced to metal complex hydroxides.

[0198] To set conditions in which metal composite oxides or metal composite hydroxides are not oxidized or reduced, it is sufficient to use inert gases such as nitrogen, helium, and argon in a dry atmosphere.

[0199] To set the conditions for the oxidation of metal complex hydroxides, oxygen or air is simply used in a dry atmosphere.

[0200] Furthermore, to set the conditions for the reduction of metal composite oxides, it is sufficient to use reducing agents such as hydrazine or sodium sulfite in a dry, inert gas atmosphere.

[0201] After drying, MCC can also be appropriately graded.

[0202] In the manufacturing method of CAM, it is preferable not to perform the process of crushing MCC. That is, it is preferable to mix uncrushed MCC with lithium compound. CAM obtained using uncrushed MCC has a lower BET specific surface area and higher sphericity compared to CAM obtained using crushed MCC. Therefore, when adding the compound containing element X (described later), element X becomes easier to distribute uniformly by using LiMO, which has a low BET specific surface area and high sphericity.

[0203] The composition ratio of the final target compound is considered when using the above lithium compound and MCC. For example, when using a nickel-cobalt-aluminum metal composite hydroxide as the MCC, the lithium compound is combined with this metal composite hydroxide to form a compound with LiNi. a Co b Al c The composition ratio of O2 (where a+b+c=1) is used in a corresponding proportion. Furthermore, in the CAM, which is the final target, if the molar ratio of Li contained in the lithium compound to the metal element contained in the MCC is 1.1 or less, it is easy to control the Cy and Cz of the obtained CAM within the preferred range of this embodiment.

[0204] Lithium-nickel-cobalt-aluminum metal composite oxides can be obtained by calcining a mixture of nickel-cobalt-aluminum metal composite hydroxide and lithium compounds. It should be noted that the calcination process utilizes dry air, an oxygen atmosphere, or an inert atmosphere, depending on the desired composition.

[0205] The firing process can be a single firing or it can involve multiple firing stages.

[0206] In cases involving multiple firing stages, the firing process at the highest temperature is recorded as the final firing. A pre-firing at a lower temperature than the final firing can be performed before the final firing. Furthermore, a post-firing at a lower temperature than the final firing can be performed after the final firing.

[0207] From the viewpoint of promoting the growth of LiMO particles, the firing temperature (maximum holding temperature) for formal firing is preferably 600°C or higher, more preferably 650°C or higher, and particularly preferably 700°C or higher. Furthermore, from the viewpoint of preventing crack formation in LiMO particles and maintaining particle strength, it is preferably 1200°C or lower, more preferably 1100°C or lower, and particularly preferably 1000°C or lower.

[0208] The upper and lower limits of the maximum holding temperature during the formal firing can be combined arbitrarily.

[0209] Examples of combinations include temperatures above 600°C and below 1200°C, temperatures above 650°C and below 1100°C, and temperatures above 700°C and below 1000°C.

[0210] If the formal firing is carried out at a temperature above 600°C, it is easy to control the Cy and Cz of the obtained CAM within the preferred range of this embodiment.

[0211] The firing temperature for pre-firing or post-firing only needs to be lower than the firing temperature for the formal firing. For example, a range of 350°C or higher and 800°C or lower can be listed.

[0212] The holding temperature during firing can be adjusted appropriately according to the type of transition metal element used, the type and amount of precipitant and inert flux.

[0213] Furthermore, the holding time at the aforementioned holding temperature can be 0.1 hours or more and 20 hours or less, preferably 0.5 hours or more and 10 hours or less. The heating rate up to the aforementioned holding temperature is typically 50°C / hour or more and 400°C / hour or less, and the cooling rate from the aforementioned holding temperature to room temperature is typically 10°C / hour or more and 400°C / hour or less. Additionally, the firing atmosphere can be atmospheric gas, oxygen, nitrogen, argon, or a mixture thereof.

[0214] (CAM manufacturing process)

[0215] CAM can be obtained by mixing the LiMO obtained in the above process with a compound containing element X and then subjecting it to heat treatment.

[0216] Examples of compounds containing element X include lithium compounds, oxides, hydroxides, carbonates, nitrates, sulfates, ammonium salts, halides, and oxalates. Oxides containing element X are preferred.

[0217] Examples of compounds containing element X include aluminum oxide, aluminum hydroxide, aluminum sulfate, aluminum chloride, boron oxide, boric acid, lithium borate, niobium oxide, lithium niobate, titanium oxide, titanium hydroxide, tungsten oxide, tungstic acid, tungsten chloride, ammonium dihydrogen phosphate, phosphorus pentoxide, phosphate, lithium phosphate, zirconium oxide, magnesium oxide, magnesium sulfate, tin oxide, etc., with aluminum oxide, aluminum hydroxide, boron oxide, boric acid, niobium oxide, lithium niobate, titanium oxide, tungsten oxide, ammonium dihydrogen phosphate, lithium borate, and lithium phosphate being preferred.

[0218] The amount of compound containing element X is adjusted according to the type of element X, in a manner that the molar amount of element X is in a ratio to the total molar amount of metal elements other than Li contained in LiMO, and is within a preferred range.

[0219] For example, in the manufacturing process of CAM, when using a compound containing at least one of the group consisting of Ti, Nb, P, Zr, Mg, Sn, W and B as element X, the molar amount of element X relative to the total molar amount of metal elements other than lithium atoms contained in LiMO is preferably 1.0 mol% or more and 5.5 mol% or less.

[0220] Furthermore, in the manufacturing process of CAM, when using a compound containing Al as element X, the molar amount of element X relative to the total molar amount of metal elements other than Li contained in LiMO is preferably 1.0 mol% or more and 8.0 mol% or less, more preferably 1.0 mol% or more and 5.5 mol% or less.

[0221] To effectively form an ion-conducting composite phase on the surface of LiMO, the 50% cumulative volumetric particle size D of the compound containing element X is required. 50 The μm is preferably 90 μm or less, more preferably 80 μm or less. Furthermore, the D of compounds containing element X... 50 Preferably, the micrometer size is 0.02 μm or larger, and more preferably 0.05 μm or larger.

[0222] D 50 The upper and lower limits can be combined arbitrarily. Examples of combinations include 0.02μm and above and 90μm and 0.05μm and above and 80μm.

[0223] When using a compound containing at least one element X selected from the group consisting of Al, Ti, Nb, Zr, Mg, Sn, and W, the D of the compound containing element X... 50 More preferably, the micrometer is 0.02 μm or more and 20 μm or less, and even more preferably, it is 0.05 μm or more and 14 μm or less.

[0224] When using a compound containing at least one of the groups chosen from B and P as element X, the D of the compound containing element X... 50 Preferably, the micrometer is 0.02 μm or more and 90 μm or less, more preferably 0.02 μm or more and 80 μm or less.

[0225] If D is used 50 If the compound containing element X is within the range described above, then the Cx, Cy, and Cz of the obtained CAM can be controlled within the preferred range of this embodiment.

[0226] [D of compounds containing element X] 50 [Determination method]

[0227] 50% cumulative volume particle size D of compounds containing element X 50 The determination can be performed using either a wet or dry method as described below. In this embodiment, compounds containing B or P as element X are determined using a dry method. Furthermore, compounds containing elements other than B and P as element X are determined using a wet method.

[0228] (Wet assay method)

[0229] The wet assay method is described below.

[0230] Specifically, firstly, 2g of the powder containing element X is added to 50ml of a 0.2% by mass sodium hexametaphosphate aqueous solution to obtain a dispersion containing the powder containing element X.

[0231] Next, the particle size distribution of the obtained dispersion was measured using a laser diffractometer to obtain a cumulative particle size distribution curve based on volume. Then, in the obtained cumulative particle size distribution curve, the particle size at 50% accumulation from the microparticle side is the 50% cumulative volume particle size D. 50 (μm). As a laser diffraction particle size analyzer, for example, the Malvern MS2000 can be used.

[0232] (Dry method for determination)

[0233] The dry method for determination is as follows.

[0234] Specifically, firstly, 2g of powder containing element X was used to determine the dry particle size distribution using a laser diffractometer, obtaining a volume-based cumulative particle size distribution curve. In the obtained cumulative particle size distribution curve, the particle size at 50% accumulation from the microparticle side is the 50% cumulative volume particle size D. 50 (μm). As a laser diffraction particle size analyzer, for example, the Malvern MS2000 can be used.

[0235] The compound containing element X and LiMO are mixed uniformly until the aggregates of the compound containing element X or the aggregates of LiMO disappear. The mixing apparatus is not limited as long as it can uniformly mix the compound containing element X and LiMO; for example, a Loedige mixer is preferred.

[0236] Furthermore, by mixing a compound containing element X with LiMO in water or an atmosphere containing water and carbon dioxide, a composite phase with ion conductivity can be formed more firmly on the surface of LiMO.

[0237] By mixing the compound containing element X and LiMO in water or an atmosphere containing water and carbon dioxide, a composite phase with ion conductivity can be formed more firmly on the surface of LiMO.

[0238] When heat treatment is performed on a mixture of a compound containing element X and LiMO, the heat treatment conditions may vary depending on the type of compound containing element X. Examples of heat treatment conditions include the heat treatment temperature and the holding time.

[0239] In this process, when using a compound containing at least one of the group consisting of Ti, Nb, Zr, Mg, Sn, W and B as element X, it is preferable to perform heat treatment in a temperature range of 300°C or higher and 650°C or lower for 4 hours or higher and 10 hours or lower.

[0240] In this process, when using a compound containing Al as element X, the heat treatment temperature is preferably between 300°C and 600°C, and the heat treatment time is between 4 and 10 hours.

[0241] If the heat treatment temperature is higher than the range mentioned above, the compound containing element X may diffuse into the LiMO crystal structure, reducing the stability of the crystal structure. If the heat treatment holding time is shorter than 4 hours, the diffusion of the compound containing element X may be insufficient, preventing the uniform formation of an ion-conducting composite phase.

[0242] In the process of adding a compound containing element X, the molar amount of element X relative to the total molar amount of metal elements other than Li contained in LiMO, the firing temperature, and the 50% cumulative volume particle size D are adjusted according to the type of compound containing element X being added. 50 It is easy to control the Cx and Cx / Cy of the obtained CAM within the preferred range of this embodiment.

[0243] <CAM Manufacturing Method 2>

[0244] The manufacturing method 2 of CAM includes the following steps (a), (b) and (c) in sequence.

[0245] Step (a): A step of mixing a metal composite compound containing at least Ni with a lithium compound and calcining it to obtain a lithium metal composite oxide.

[0246] Step (b): A step of mixing the above-mentioned lithium metal composite oxide with a compound containing element X in a ratio of at least 1.0 mol% to at least 5.5 mol% of the total molar amount of element X relative to the total molar amount of metal elements other than lithium atoms contained in the above-mentioned lithium metal composite oxide to obtain a mixture. Element X is one or more elements selected from the group consisting of Al, Ti, Nb, B, W, Zr, Mg, Sn, and P, and the 50% cumulative volume particle size D of the compound containing element X is... 50 (μm) is greater than 0.02μm and less than 90μm.

[0247] Step (c): A step of heat-treating the above mixture in an oxygen-containing atmosphere at a temperature of 200°C or higher and 600°C or lower.

[0248] Process (a)

[0249] Step (a) is the same as the LiMO manufacturing step in the above-described CAM manufacturing method 1. In CAM manufacturing method 2, as a change from the LiMO manufacturing step in the above-described CAM manufacturing method 1, it is preferable to include a step of mixing MCC with a lithium compound and calcining it, and then crushing the resulting calcined material using a stone mill crusher.

[0250] It can also include a process of crushing the calcined product obtained after one firing of MCC and lithium compounds using a stone mill crusher.

[0251] Alternatively, the first calcined product obtained after calcining MCC and lithium compounds once can be crushed using a stone mill crusher, and the second calcined product obtained by calcining the crushed product can be further crushed using a stone mill crusher.

[0252] For example, the conditions for crushing using a stone mill crusher can be listed as a rotation speed of 1000 rpm or more and 3000 rpm or less, and a clearance of 50 μm or more and 200 μm or less.

[0253] By using the above conditions to break the calcined material, it becomes easier to obtain CAMs that satisfy (1) and (2) and CAMs that satisfy (1) and (3).

[0254] Process (b) and Process (c)

[0255] Steps (b) and (c) are the same as the CAM manufacturing steps in the above-described CAM manufacturing method 1, except that the heat treatment temperature of the mixture is different.

[0256] In step (b), when using a compound containing at least one of the group consisting of Ti, Nb, Zr, Mg, Sn, W, and B as element X, the heat treatment conditions preferably involve setting the heat treatment temperature to a range of 200°C or higher and 650°C or lower, more preferably 200°C or higher and 600°C or lower. The heat treatment time is preferably 4 hours or higher and 10 hours or lower.

[0257] In step (b), when using a compound containing Al as element X, the heat treatment conditions preferably involve setting the heat treatment temperature to a range of 200°C or higher and 600°C or lower. The heat treatment time is preferably set to a range of 4 hours or higher and 10 hours or lower.

[0258] If the heat treatment temperature is higher than the range mentioned above, the compound containing element X may diffuse into the LiMO crystal structure, reducing the stability of the crystal structure. If the heat treatment holding time is shorter than 4 hours, the diffusion of the compound containing element X may be insufficient, preventing the uniform formation of an ion-conducting composite phase.

[0259] Step (b) preferably includes a step of mixing the covering material containing element X and LiMO in water or an atmosphere containing water and carbon dioxide. When mixing in an atmosphere containing water and carbon dioxide, the moisture content in the atmosphere is preferably 40% or more in terms of relative humidity.

[0260] Step (b) preferably includes a step of mixing the coating material containing element X with LiMO and then holding the mixture in water or an atmosphere containing water and carbon dioxide. The holding time after mixing is preferably 0.5 hours or more and 3 hours or less.

[0261] <Lithium-ion secondary batteries>

[0262] Next, the structure of the lithium secondary battery will be explained, and the positive electrode (hereinafter, sometimes referred to as the positive electrode) of the lithium secondary battery using the CAM of this embodiment, and the lithium secondary battery having the positive electrode will also be explained.

[0263] The CAM of this embodiment preferably includes the CAM of this embodiment as described above, but may also contain other components without impairing the effects of the present invention.

[0264] An example of a preferred lithium secondary battery using the CAM of this embodiment includes a positive electrode and a negative electrode, a separator sandwiched between the positive and negative electrodes, and an electrolyte disposed between the positive and negative electrodes.

[0265] Figure 1A , Figure 1B This is a schematic diagram illustrating an example of a lithium secondary battery. The cylindrical lithium secondary battery 10 is manufactured as shown below.

[0266] First, such as Figure 1A As shown, an electrode assembly 4 is formed by stacking and winding a pair of strip-shaped diaphragms 1, a strip-shaped positive electrode 2 with a positive electrode lead 21 at one end, and a strip-shaped negative electrode 3 with a negative electrode lead 31 at one end in the order of diaphragm 1, positive electrode 2, diaphragm 1, and negative electrode 3.

[0267] Next, as Figure 1B As shown, after accommodating the electrode assembly 4 and an insulator (not shown) in the battery can 5, the bottom of the can is sealed, the electrolyte 6 is impregnated into the electrode assembly 4, and the electrolyte is disposed between the positive electrode 2 and the negative electrode 3. Furthermore, by sealing the upper part of the battery can 5 with a top insulator 7 and a sealing body 8, a lithium secondary battery 10 can be manufactured.

[0268] As for the shape of the electrode assembly 4, for example, the cross-sectional shape when the electrode assembly 4 is cut perpendicularly to the winding axis can be a circle, an ellipse, a rectangle, or a columnar shape such as a rectangle with rounded corners.

[0269] Furthermore, the shape of the lithium secondary battery having such an electrode assembly 4 can adopt the shape specified in the battery standards defined by the International Electrotechnical Commission (IEC), namely IEC 60086 or JIS C 8500. For example, cylindrical, square, and other shapes can be listed.

[0270] Furthermore, lithium secondary batteries are not limited to the above-mentioned wound type structure, but can also be a stacked type structure obtained by repeatedly overlapping the positive electrode, separator, negative electrode, and separator. Examples of stacked lithium secondary batteries include so-called coin-type batteries, button-type batteries, and paper-type (or sheet-type) batteries.

[0271] The following sections will explain each component in turn.

[0272] (positive electrode)

[0273] The positive electrode of this embodiment can be manufactured by first preparing a positive electrode mixture containing CAM, conductive material and adhesive, and then loading the positive electrode mixture onto the positive electrode current collector.

[0274] (Conductive materials)

[0275] Carbon materials can be used as the conductive material for the positive electrode. Examples of carbon materials include graphite powder, carbon black (such as acetylene black), and fibrous carbon materials.

[0276] The proportion of conductive material in the positive electrode mixture is preferably 5 parts by mass and 20 parts by mass or less per 100 parts by mass of the positive electrode active material. This proportion can also be reduced when using fibrous carbon materials such as graphitized carbon fibers and carbon nanotubes as conductive materials.

[0277] (Adhesive)

[0278] Thermoplastic resins can be used as the binder in the positive electrode. Examples of such thermoplastic resins include polyimide resins; fluorinated resins such as polyvinylidene fluoride (hereinafter sometimes referred to as PVdF) and polytetrafluoroethylene; polyolefin resins such as polyethylene and polypropylene; and resins described in WO2019 / 098384A1 or US2020 / 0274158A1.

[0279] These thermoplastic resins can also be used in combination of two or more. By using fluoropolymer and polyolefin resin as binders, and setting the proportion of fluoropolymer relative to the total positive electrode binder to 1% by mass or more and 10% by mass or less, and setting the proportion of polyolefin resin to 0.1% by mass or more and 2% by mass or less, a positive electrode binder with high adhesion to the positive electrode current collector and high bonding strength within the positive electrode binder can be obtained.

[0280] (Positive current collector)

[0281] As the positive current collector of the positive electrode, a strip-shaped component made of metal materials such as Al, Ni, and stainless steel can be used. Among these, considering ease of processing and low cost, Al is preferred as the forming material and the component is processed into a thin film.

[0282] One method for loading a positive electrode agent onto a positive current collector is to press-form the positive electrode agent onto the positive current collector. Alternatively, the positive electrode agent can be pasted using an organic solvent, the resulting paste can be applied to at least one side of the positive current collector and dried, then pressed and bonded, thereby loading the positive electrode agent onto the positive current collector.

[0283] When the positive electrode mixture is paste-formed, the organic solvents that can be used include amine solvents such as N,N-dimethylaminopropylamine and diethylenetriamine; ether solvents such as tetrahydrofuran; ketone solvents such as methyl ethyl ketone; ester solvents such as methyl acetate; and amide solvents such as dimethylacetamide and N-methyl-2-pyrrolidone (hereinafter sometimes referred to as NMP).

[0284] Methods for applying a paste of positive electrode agent to the positive electrode current collector include, for example, slot extrusion coating, screen coating, curtain coating, scraper coating, gravure coating, and electrostatic spraying.

[0285] The positive electrode can be manufactured using the methods listed above.

[0286] (negative electrode)

[0287] The negative electrode of a lithium secondary battery only needs to be able to dope and dedope lithium ions at a lower potential than the positive electrode. Examples include electrodes formed by a negative electrode mixture containing negative electrode active material supported on a negative electrode current collector, and electrodes formed solely by negative electrode active material.

[0288] (Negative electrode active material)

[0289] Examples of negative electrode active materials include carbon materials, chalcogenides (oxides, sulfides, etc.), nitrides, metals or alloys, and materials that can be doped and dedoped with lithium ions at a lower potential than that of the positive electrode.

[0290] Carbon materials that can be used as negative electrode active materials include natural graphite, artificial graphite, coke, carbon black, thermally decomposed carbon, carbon fiber, and sintered organic polymer compounds.

[0291] As oxides that can be used as negative electrode active materials, examples include SiO2 and SiO (e.g., SiO2). x (where x is a positive real number) represents the silicon oxide SnO2 and SnO equation SnO x (where x is a positive real number) represents the tin oxide; Li4Ti5O 12 And metal composite oxides containing lithium and titanium, such as LiVO2.

[0292] In addition, lithium metal, silicon metal, and tin metal can be listed as metals that can be used as negative electrode active materials.

[0293] The materials described in WO2019 / 098384A1 or US2020 / 0274158A1 can also be used as materials that can be used as negative electrode active materials.

[0294] These metals or alloys, for example, after being processed into foil, are primarily used as electrodes on their own.

[0295] Among the aforementioned negative electrode active materials, carbon materials with graphite as the main component, such as natural graphite or artificial graphite, are preferred because their potential remains essentially unchanged from an uncharged state to a fully charged state during charging (good potential flatness), their average discharge potential is low, and their capacity retention rate during repeated charge and discharge (good cycle characteristics). The shape of the carbon material can be, for example, any of the following: flakes like natural graphite, spheres like mesophase carbon microspheres, fibrous forms like graphitized carbon fibers, or aggregates of micropowder.

[0296] The aforementioned negative electrode compound may also contain an adhesive as needed. Examples of adhesives include thermoplastic resins, specifically PVdF, thermoplastic polyimide, carboxymethyl cellulose (hereinafter, sometimes referred to as CMC), styrene-butadiene rubber (hereinafter, sometimes referred to as SBR), polyethylene, and polypropylene.

[0297] (Negative current collector)

[0298] As a negative electrode current collector, examples include strip-shaped components made of metallic materials such as Cu, Ni, and stainless steel. Among these, considering the difficulty in forming alloys with lithium and the ease of processing, components made of Cu and processed into thin films are preferred.

[0299] As a method for loading the negative electrode agent onto such a negative current collector, similar to the case of the positive electrode, methods such as press molding, paste formation using solvents and coating onto the negative current collector, drying, pressing, and bonding can be listed.

[0300] (Septum)

[0301] As a separator in a lithium-ion secondary battery, materials such as porous membranes, nonwoven fabrics, or woven fabrics formed from polyolefin resins such as polyethylene and polypropylene, fluoropolymers, or nitrogen-containing aromatic polymers can be used. Furthermore, two or more of these materials can be used to form the separator, or these materials can be layered to form the separator. Additionally, separators described in JP-A-2000-030686 or US20090111025A1 can also be used.

[0302] In this embodiment, in order to allow good permeability of the electrolyte during battery use (charging and discharging), the gas permeability resistance of the separator obtained by the Gurley method specified in JIS P8117 is preferably 50 seconds / 100cc or more and 300 seconds / 100cc or less, more preferably 50 seconds / 100cc or more and 200 seconds / 100cc or less.

[0303] Furthermore, the porosity of the diaphragm is preferably 30% by volume or more and 80% by volume or less, more preferably 40% by volume or more and 70% by volume or less. The diaphragm may also be a component obtained by laminating diaphragms with different porosities.

[0304] (electrolyte)

[0305] The electrolyte in a lithium secondary battery contains electrolytes and organic solvents.

[0306] Examples of electrolytes included in the electrolyte solution include lithium salts such as LiClO4, LiPF6, and LiBF4, or mixtures of two or more of these. Alternatively, electrolytes described in WO2019 / 098384A1 or US2020 / 0274158A1 may be used. Preferably, the electrolyte used is one containing at least one fluorine-containing electrolyte selected from the group consisting of LiPF6, LiAsF6, LiSbF6, LiBF4, LiCF3SO3, LiN(SO2CF3)2, and LiC(SO2CF3)3.

[0307] In addition, as an organic solvent contained in the above-mentioned electrolyte, for example, propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, WO2019 / 098384A1 or US2020 / 0274158A1 can be used.

[0308] As organic solvents, it is preferable to use a mixture of two or more of them, and more preferably a mixed solvent of cyclic carbonates and non-cyclic carbonates or a mixed solvent of cyclic carbonates and ethers. As a mixed solvent of cyclic carbonates and non-cyclic carbonates, a mixed solvent comprising ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate is preferred.

[0309] Furthermore, as an electrolyte, since the safety of the resulting lithium secondary battery is improved, it is preferable to use an electrolyte containing fluorine-containing lithium salts such as LiPF6 and organic solvents with fluorine substituents.

[0310] Furthermore, the positive electrode with the above-described configuration can improve the cycle characteristics of lithium secondary batteries because it has the aforementioned CAM configuration.

[0311] Furthermore, lithium secondary batteries with the above-described configuration, having the aforementioned positive electrode, become secondary batteries with high cycle characteristics.

[0312] <All-solid-state lithium-ion secondary batteries>

[0313] Next, the structure of the all-solid-state lithium secondary battery will be described, and the positive electrode of the CAM using one embodiment of the present invention as the all-solid-state lithium secondary battery, and the all-solid-state lithium secondary battery having the positive electrode will also be described.

[0314] Figure 2 , 3 This is a schematic diagram illustrating an example of an all-solid-state lithium-ion secondary battery. Figure 2 This is a schematic diagram illustrating the stacked structure of an all-solid-state lithium-ion secondary battery. Figure 3 This is a schematic diagram showing the overall structure of an all-solid-state lithium-ion secondary battery.

[0315] The all-solid-state lithium-ion secondary battery 1000 has a laminate 100 comprising a positive electrode 110, a negative electrode 120, and a solid electrolyte layer 130, and an outer packaging 200 for housing the laminate 100. Furthermore, the all-solid-state lithium secondary battery 1000 can also be a bipolar structure in which a current collector (CAM) and a negative electrode active material are disposed on both sides of the current collector. As a specific example of a bipolar structure, the structure described in JP-A-2004-95400 can be cited.

[0316] The materials that make up the various components are described below.

[0317] The laminate 100 may also have an external terminal 113 connected to the positive current collector 112 and an external terminal 123 connected to the negative current collector 122.

[0318] In the laminate 100, the positive electrode 110 and the negative electrode 120 sandwich the solid electrolyte layer 130 in a manner that prevents them from short-circuiting. In addition, the all-solid-state lithium-ion secondary battery 1000 may also have a separator used in conventional liquid lithium-ion secondary batteries between the positive electrode 110 and the negative electrode 120 to prevent short circuits between the positive electrode 110 and the negative electrode 120.

[0319] The all-solid-state lithium-ion secondary battery 1000 has an insulator (not shown) that insulates the laminate 100 from the outer packaging 200, and a seal (not shown) that seals the opening 200a of the outer packaging 200.

[0320] The outer packaging 200 can be a container formed from a highly corrosion-resistant metal material such as aluminum, stainless steel, or nickel-plated steel. Alternatively, a container formed by processing a laminated film with at least one side treated for corrosion resistance into a bag shape can also be used.

[0321] The shapes of the all-solid-state lithium-ion secondary battery 1000 can include, for example, coin type, button type, paper type (or sheet type), cylindrical type, square type, etc.

[0322] The diagram illustrates an all-solid-state lithium-ion secondary battery 1000 having one stack 100, but it is not limited to this. The all-solid-state lithium-ion secondary battery 1000 may also be configured such that the stack 100 is used as a unit cell and multiple unit cells (stack 100) are sealed inside the outer packaging 200.

[0323] The following sections will explain each component in turn.

[0324] (positive electrode)

[0325] The positive electrode 110 has a positive electrode active material layer 111 and a positive electrode current collector 112.

[0326] The positive electrode active material layer 111 includes the CAM described above as one aspect of the present invention. Alternatively, the positive electrode active material layer 111 may also include a solid electrolyte (second solid electrolyte), a conductive material, and a binder.

[0327] The CAM contained in the positive electrode active material layer 111 is in contact with the second solid electrolyte contained in the positive electrode active material layer 111. Specifically, the positive electrode active material layer 111 contains a plurality of particles (CAM) containing LiMO crystals, and a solid electrolyte filling the spaces between the plurality of particles (CAM) and in contact with the particles (CAM).

[0328] (Solid electrolyte)

[0329] The solid electrolyte that can be used as the positive electrode active material layer 111 can be a solid electrolyte that has lithium-ion conductivity and is known to be used in all-solid-state batteries. Examples of such solid electrolytes include inorganic electrolytes and organic electrolytes. Examples of inorganic electrolytes include oxide-based solid electrolytes, sulfide-based solid electrolytes, and hydride-based solid electrolytes. Examples of organic electrolytes include polymer-based solid electrolytes.

[0330] As electrolytes, compounds described in WO2020 / 208872A1, US2016 / 0233510A1, US2012 / 0251871A1, and US2018 / 0159169A1 can be listed, for example, the following compounds.

[0331] In this embodiment, an oxide-based solid electrolyte or a sulfide-based solid electrolyte is preferred, and an oxide-based solid electrolyte is more preferred.

[0332] (Oxide-based solid electrolyte)

[0333] Examples of oxide-based solid electrolytes include perovskite oxides, NASICON oxides, LISICON oxides, and garnet oxides. Specific examples of each oxide can be found in compounds described in WO2020 / 208872A1, US2016 / 0233510A1, and US2020 / 0259213A1.

[0334] As a garnet-type oxide, Li7La3Zr2O can be listed as an example. 12 Li-La-Zr oxides such as (LLZ) are examples of such oxides.

[0335] Oxide-based solid electrolytes can be crystalline or amorphous. Examples of amorphous solid electrolytes include Li-BO compounds such as Li3BO3, Li2B4O7, and LiBO2. Oxide-based solid electrolytes preferably contain amorphous materials.

[0336] (Sulfide-based solid electrolyte)

[0337] As sulfide-based solid electrolytes, examples include Li₂S-P₂S₅ compounds, Li₂S-SiS₂ compounds, Li₂S-GeS₂ compounds, Li₂S-B₂S₃ compounds, LiI-Si₂S-P₂S₅ compounds, LiI-Li₂S-P₂O₅ compounds, LiI-Li₃PO₄-P₂S₅ compounds, and Li 10 GeP2S 12 wait.

[0338] It should be noted that in this specification, the term "system compound" referring to sulfide-based solid electrolytes is used as a general term for solid electrolytes that primarily contain raw materials such as "Li2S" and "P2S5" as described before "system compound". For example, the term "Li2S-P2S5 system compound" includes solid electrolytes that primarily contain Li2S and P2S5, and further contain other raw materials. Furthermore, the term "Li2S-P2S5 system compound" also includes solid electrolytes in which the mixing ratio of Li2S and P2S5 varies.

[0339] As compounds in the Li2S-P2S5 series, examples include Li2S-P2S5, Li2S-P2S5-LiI, Li2S-P2S5-LiCl, Li2S-P2S5-LiBr, and Li2S-P2S... 5- LiI-LiBr, etc.

[0340] Examples of Li2S-SiS2 compounds include Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, and Li2S-SiS2-P2S5-LiCl.

[0341] Examples of Li2S-GeS2 compounds include Li2S-GeS2 and Li2S-GeS2-P2S5.

[0342] Sulfide-based solid electrolytes can be either crystalline or amorphous materials.

[0343] Two or more solid electrolytes may be used together without impairing the effectiveness of the invention.

[0344] (Conductive materials and adhesives)

[0345] As the conductive material in the positive electrode active material layer 111, the materials described in the above-described (conductive material) section can be used. Furthermore, the proportion of the conductive material in the positive electrode mixture can also be the proportion described in the above-described (conductive material) section. Additionally, as the binder in the positive electrode, the materials described in the above-described (binder) section can be used.

[0346] (Positive current collector)

[0347] The positive current collector 112 of the positive electrode 110 can be made of the material described above (positive current collector).

[0348] One method for loading the positive electrode active material layer 111 onto the positive electrode current collector 112 is to press-form the positive electrode active material layer 111 onto the positive electrode current collector 112. For press-forming, cold pressing or hot pressing can be used.

[0349] Alternatively, a positive electrode paste can be prepared by using an organic solvent to paste a mixture of positive electrode active material, solid electrolyte, conductive material and adhesive. The obtained positive electrode paste is then coated on at least one surface of the positive electrode current collector 112 and dried, pressed and bonded, thereby enabling the positive electrode active material layer 111 to be supported on the positive electrode current collector 112.

[0350] Alternatively, a positive electrode paste can be prepared by using an organic solvent to paste a mixture of positive electrode active material, solid electrolyte and conductive material. The obtained positive electrode paste is then coated on at least one surface of the positive electrode current collector 112 and dried and sintered, thereby enabling the positive electrode active material layer 111 to be supported on the positive electrode current collector 112.

[0351] The organic solvent that can be used in the positive electrode mixture is the same organic solvent that can be used in the case of pasteurizing the positive electrode mixture as described above in (positive electrode current collector).

[0352] Methods for coating the positive electrode agent onto the positive electrode current collector 112 include, for example, slit extrusion coating, screen coating, curtain coating, scraper coating, gravure coating, and electrostatic spraying.

[0353] The positive electrode 110 can be manufactured using the methods listed above.

[0354] (negative electrode)

[0355] The negative electrode 120 has a negative electrode active material layer 121 and a negative electrode current collector 122. The negative electrode active material layer 121 contains a negative electrode active material. In addition, the negative electrode active material layer 121 may also contain a solid electrolyte and a conductive material. The negative electrode active material, negative electrode current collector, solid electrolyte, conductive material, and binder may be the substances described above.

[0356] (Solid electrolyte layer)

[0357] The solid electrolyte layer 130 has the aforementioned solid electrolyte.

[0358] The solid electrolyte layer 130 can be formed by depositing an inorganic solid electrolyte on the surface of the positive electrode active material layer 111 of the positive electrode 110 by sputtering.

[0359] Furthermore, the solid electrolyte layer 130 can be formed by coating the surface of the positive electrode active material layer 111 of the positive electrode 110 with a paste-like mixture containing solid electrolyte and then drying it. Alternatively, after drying, it can be pressed and further pressed by cold isostatic pressing (CIP) to form the solid electrolyte layer 130.

[0360] The laminate 100 can be manufactured by laminating a negative electrode 120 in a manner where the surface of the negative electrode active material layer 121 is in contact with the surface of the solid electrolyte layer 130, which is disposed on the positive electrode 110 as described above, using a known method.

[0361] With the CAM structure described above, lithium ion transfer can proceed smoothly between the positive electrode and the solid electrolyte, thus improving battery performance.

[0362] The electrode structure described above, having the aforementioned positive electrode active material for all-solid-state lithium-ion batteries, can improve the battery performance of all-solid-state lithium-ion batteries.

[0363] [Methods for determining initial discharge capacity and cycle maintenance rate]

[0364] <Fabrication of the positive electrode for lithium secondary batteries>

[0365] A paste-like positive electrode compound was prepared by adding and mixing CAM obtained using the manufacturing method described later, a conductive material (acetylene black), and a binder (PVdF) in a ratio of CAM:conductive material:binder = 92:5:3 (mass ratio). N-methyl-2-pyrrolidone was used as the organic solvent in the preparation of the positive electrode compound.

[0366] The obtained positive electrode mixture was coated onto a 40 μm thick Al foil to serve as the current collector and then vacuum-dried at 150°C for 8 hours to obtain a positive electrode for lithium secondary batteries. The electrode area of ​​this positive electrode for lithium secondary batteries was set to 1.65 cm². 2 .

[0367] <Making a Lithium Secondary Battery (Coin-Shaped Half-Battery)>

[0368] Perform the following operations inside a glove box under an argon atmosphere.

[0369] The positive electrode for a lithium-ion secondary battery, prepared as described in "Preparation of Positive Electrode for Lithium-ion Secondary Batteries," is placed with the aluminum foil side down on the lower cover of a component for a coin-type battery R2032 (manufactured by Hosen Co., Ltd.), and a separator (a porous polyethylene membrane) is placed on top. 300 μl of electrolyte is then injected. The electrolyte is a solution obtained by dissolving LiPF6 in a 30:35:35 (volume ratio) mixture of ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate at a ratio of 1.0 mol / L.

[0370] Next, using metallic lithium as the negative electrode, the negative electrode was placed on top of the laminated membrane separator, and the top cover was placed on top of it with a gasket. The lithium secondary battery (coin-type half-cell R2032, hereinafter sometimes referred to as "half-cell") was then fabricated by using a seam sealing machine.

[0371] <Charge and Discharge Test>

[0372] Using the half-cells prepared by the above method, first charge-discharge efficiency tests and cycle tests were conducted to evaluate the first discharge capacity and cycle capacity retention rate as indicators of the performance of the secondary battery.

[0373] • First charge and discharge test

[0374] At a test temperature of 25℃, the current setting value for both charging and discharging was set to 0.2CA, and constant current and constant voltage charging and constant current discharging were performed respectively.

[0375] The maximum charging voltage is set to 4.35V, and the minimum discharging voltage is set to 2.8V.

[0376] Cyclic test

[0377] The cyclic test followed immediately after the initial charge-discharge test, with the test temperature set at 25°C. The number of charge-discharge cycles was set to 50. The current setting was set to 1CA, and constant current-constant voltage charging and constant current discharging were performed respectively.

[0378] Charging: Current setting 1CA, maximum voltage 4.35V, constant voltage and constant current charging.

[0379] Discharge: Battery setting 1CA, minimum voltage 2.8V, constant current discharge.

[0380] • Circulatory maintenance rate

[0381] The cycle capacity retention rate is defined by the discharge capacity of the first cycle and the discharge capacity of the 50th cycle in the cyclic test, using the following formula. The higher the cycle capacity retention rate, the more the capacity reduction of the battery after repeated charge and discharge is suppressed, and therefore, it is a more preferred battery performance.

[0382] Cycle maintenance rate (%) =

[0383] Discharge capacity of the 50th cycle (mAh / g) / Discharge capacity of the 1st cycle (mAh / g) × 100

[0384] Example

[0385] Next, the present invention will be further described in detail through embodiments.

[0386] <Composition Analysis>

[0387] The compositional analysis of the CAM manufactured by the method described later is carried out by the method described in the above [Compositional Analysis].

[0388] <BET Specific Surface Area Measurement>

[0389] The BET specific surface area of ​​CAM is determined by the method described in [Determination of BET Specific Surface Area] above.

[0390] <D of compounds containing element X> 50 Measurement>

[0391] 50% cumulative volume particle size D of compounds containing element X 50 Through the above [compounds containing element X, D] 50 The determination shall be performed using the method described in the [Determination Method]. Compounds containing B or P as element X shall be determined by a dry method. Furthermore, compounds containing elements X other than B and P shall be determined by the following wet method.

[0392] The wet assay method is implemented as described above (wet assay method).

[0393] The dry method for determination is carried out as described above (dry method for determination).

[0394] <X-ray photoelectron spectroscopy (XPS)>

[0395] The measurements using XPS were performed using the methods described in the section on [X-ray photoelectron spectroscopy analysis].

[0396] · Determination of Cx

[0397] For the spectrum of element X (as the spectral peaks of element X, aluminum 2p, titanium 2p, niobium 3d, boron 1s, tungsten 4f, zirconium 3d, magnesium 2p, tin 3d, and phosphorus 2p), the abundance (mass%) of each element is calculated from the peak area of ​​each element's spectrum.

[0398] • Cy determination

[0399] The amount of carbon atoms present (mass%) is calculated based on the peak area of ​​the C1s spectrum, which has a bonding energy peak at 290±5 eV.

[0400] Combustion-Infrared Absorption Method

[0401] · Determination of Cz

[0402] The amount of carbon atoms (mass%) contained in the entire CAM particles was calculated using the combustion-infrared absorption method.

[0403] Combustion-infrared absorption spectrometry was performed using an EMIA-810W. Measurements were conducted in an oxygen stream at a combustion temperature of 1400°C. After combustion began, analysis was performed for 60 seconds, and the composition of the carbon-containing gas produced was determined using an infrared detector to calculate the amount of carbon atoms present.

[0404] <Calculation of Cx / Cy>

[0405] The ratio of Cx to Cy, Cx / Cy, can be calculated using the Cx and Cy values ​​obtained through the above method.

[0406] <Calculation of Cy / Cz>

[0407] The ratio of Cy to Cz, i.e., Cy / Cz, is calculated using the Cy and Cz values ​​obtained through the above method.

[0408] <Methods for determining initial discharge capacity and cycle maintenance>

[0409] As indicators of secondary battery performance, the initial discharge capacity and cycle capacity retention are evaluated. Specifically, the initial discharge capacity and cycle capacity retention are measured using the methods described in the above-mentioned [Methods for Determining Initial Discharge Capacity and Cycle Capacity Retention].

[0410] Example 1

[0411] 1. Manufacturing of CAM-1

[0412] After adding water to the reaction tank equipped with a stirrer and an overflow pipe, add an aqueous solution of sodium hydroxide and maintain the liquid temperature at 50°C.

[0413] A mixed raw material solution was prepared by mixing nickel sulfate aqueous solution, cobalt sulfate aqueous solution and aluminum sulfate aqueous solution in an atomic ratio of Ni to Co to Al of 88:9:3.

[0414] Next, the mixed raw material solution and ammonium sulfate aqueous solution were continuously added to the reaction tank under stirring as a complexing agent. Sodium hydroxide aqueous solution was added dropwise as needed to maintain the pH of the solution in the reaction tank at 11.6 (measured at a liquid temperature of 40°C), thus obtaining nickel-cobalt-aluminum composite hydroxide particles.

[0415] Nickel-cobalt-aluminum composite hydroxide 1 was obtained by washing the particles of nickel-cobalt-aluminum composite hydroxide, dehydrating them with a centrifuge, separating them, and drying them at 105°C.

[0416] Nickel-cobalt-aluminum composite hydroxide 1 and lithium hydroxide monohydrate powder were weighed and mixed in a molar ratio of Li / (Ni+Co+Al)=1.03.

[0417] Subsequently, it was calcined at 650°C for 5 hours in an oxygen atmosphere, then pulverized using a stone mill, and further calcined at 760°C for 5 hours in an oxygen atmosphere. It was then pulverized again using a stone mill to obtain LiMO-1 powder.

[0418] The obtained LiMO-1 was reacted with a compound containing element X, namely niobium oxide (D). 50 =1.30 μm) were mixed at a ratio of 5.1 mol% of the molar amount of element X relative to the total molar amount of metal elements other than Li in LiMO-1. CAM-1 was obtained by heat treatment at 500 °C for 5 hours under an oxygen atmosphere, resulting in a composite phase containing Nb as element X on the surface of the LiMO powder containing Ni, Co, and Al.

[0419] 2. Evaluation of CAM-1

[0420] Compositional analysis of CAM-1 yielded results of m = 0.03, n = 0.08, p = 0.09, with element M being Co and elements X being Al and Nb.

[0421] The results of Cx, Cy, Cz, Cx / Cy, Cy / Cz, initial discharge capacity and cycle maintenance rate of CAM-1 are recorded in Tables 1-2.

[0422] Example 2

[0423] The compound containing element X is designated as titanium dioxide (D). 50 =2.5μm), and mixed at a ratio of 4.1 mol% of the molar amount of element X relative to the total molar amount of metal elements other than Li in LiMO-1, otherwise the same operation as in Example 1 is performed.

[0424] CAM-2 was obtained by heat treatment at 500°C for 5 hours in an oxygen atmosphere. The surface of the LiMO-1 powder containing Ni, Co and Al has a composite phase containing Ti as element X.

[0425] 2. Evaluation of CAM-2

[0426] Compositional analysis of CAM-2 yielded results of m = 0.04, n = 0.07, and p = 0.09. Element M was Co, and elements X were Al and Ti.

[0427] The results of Cx, Cy, Cz, Cx / Cy, Cy / Cz, initial discharge capacity and cycle maintenance rate of CAM-2 are recorded in Tables 1-2.

[0428] Example 3

[0429] The compound containing element X is designated as ammonium dihydrogen phosphate (D). 50 =75.6μm), and mixed at a ratio of 4.4 mol% of the molar amount of element X relative to the total molar amount of metal elements other than Li in LiMO-1, otherwise the same operation as in Example 1 was performed.

[0430] CAM-3 was obtained by heat treatment at 600°C for 5 hours in an oxygen atmosphere. The surface of LiMO-1 powder containing Ni, Co and Al has a composite phase containing P as element X.

[0431] 2. Evaluation of CAM-3

[0432] Compositional analysis of CAM-3 yielded results of m = 0.03, n = 0.05, and p = 0.09. Element M was Co, and elements X were Al and P.

[0433] The results of Cx, Cy, Cz, Cx / Cy, Cy / Cz, initial discharge capacity and cycle maintenance rate of CAM-3 are recorded in Tables 1-2.

[0434] Example 4

[0435] The compound containing element X is designated as tungsten oxide (D). 50=3.17μm), and mixed at a ratio of 5.1 mol% of the molar amount of element X relative to the total molar amount of metal elements other than Li in LiMO-1, otherwise the same operation as in Example 1 was performed.

[0436] CAM-4 was obtained by heat treatment at 500°C for 5 hours in an oxygen atmosphere. The surface of the LiMO powder containing Ni, Co and Al has a composite phase containing W as element X.

[0437] 2. Evaluation of CAM-4

[0438] Compositional analysis of CAM-4 yielded results of m = 0.03, n = 0.06, p = 0.09, with element M being Co and elements X being Al and W.

[0439] The results of Cx, Cy, Cz, Cx / Cy, Cy / Cz, initial discharge capacity and cycle maintenance rate of CAM-4 are recorded in Tables 1-2.

[0440] Example 5

[0441] The compound containing element X is designated as boric acid (D). 50 =16.3μm), and mixed at a ratio of 4.6 mol% of the molar amount of element X relative to the total molar amount of metal elements other than Li in LiMO-1, otherwise the same operation as in Example 1 was performed.

[0442] CAM-5 was obtained by heat treatment at 400°C for 5 hours in an oxygen atmosphere. The powder containing Ni, Co and Al has a composite phase containing B as element X on its surface.

[0443] 2. Evaluation of CAM-5

[0444] Compositional analysis of CAM-5 yielded results of m = 0.04, n = 0.06, and p = 0.09. Element M was Co, and elements X were Al and B.

[0445] The results of Cx, Cy, Cz, Cx / Cy, Cy / Cz, initial discharge capacity and cycle maintenance rate of CAM-5 are recorded in Tables 1-2.

[0446] Example 6

[0447] The compound containing element X is designated as aluminum oxide (D). 50 =3.5μm), and mixed at a ratio of 5.1 mol% of the molar amount of element X relative to the total molar amount of metal elements other than Li in LiMO-1, otherwise the same operation as in Example 1 is performed.

[0448] CAM-6 was obtained by heat treatment at 600°C for 5 hours in an oxygen atmosphere. The surface of the LiMO-1 powder containing Ni, Co and Al has a composite phase containing Al as element X.

[0449] 2. Evaluation of CAM-6

[0450] Compositional analysis of CAM-6 yielded results of m = -0.002, n = 0.07, p = 0.09, with element M being Co and element X being Al.

[0451] The results of Cx, Cy, Cz, Cx / Cy, Cy / Cz, initial discharge capacity and cycle maintenance rate of CAM-6 are recorded in Tables 1-2.

[0452] Example 7

[0453] The compound containing element X is designated as titanium dioxide (D). 50 =15.1μm), and mixed at a ratio of 1.1 mol% of the molar amount of element X relative to the total molar amount of metal elements other than Li in LiMO-1, otherwise the same operation as in Example 1 is performed.

[0454] CAM-7 was obtained by heat treatment at 500°C for 5 hours in an oxygen atmosphere. The surface of the LiMO-1 powder containing Ni, Co and Al has a composite phase containing Ti as element X.

[0455] 2. Evaluation of CAM-7

[0456] Compositional analysis of CAM-7 yielded results of m = 0.04, n = 0.06, and p = 0.09. Element M was Co, and elements X were Al and Ti.

[0457] The results of Cx, Cy, Cz, Cx / Cy, Cy / Cz, initial discharge capacity and cycle maintenance rate of CAM-7 are recorded in Tables 1-2.

[0458] Comparative Example 1

[0459] The compound containing element X is designated as titanium dioxide (D). 50 =2.53μm), and mixed at a ratio of 4.6 mol% of the molar amount of element X relative to the total molar amount of metal elements other than Li in LiMO-1, otherwise the same operation as in Example 1 was performed.

[0460] CAM-8 was obtained by heat treatment at 700°C for 5 hours in an oxygen atmosphere. The surface of the LiMO-1 powder containing Ni, Co and Al has a composite phase containing Ti as element X.

[0461] 2. Evaluation of CAM-8

[0462] Compositional analysis of CAM-8 yielded results of m = 0.01, n = 0.07, and p = 0.09. Element M was Co, and elements X were Al and Ti.

[0463] The results of Cx, Cy, Cz, Cx / Cy, Cy / Cz, initial discharge capacity and cycle maintenance rate of CAM-8 are recorded in Tables 1-2.

[0464] Comparative Example 2

[0465] The compound containing element X is designated as niobium oxide (D). 50 =1.30μm), and mixed at a ratio of 6.1 mol% of the molar amount of element X relative to the total molar amount of metal elements other than Li in LiMO-1, otherwise the same operation as in Example 1 was performed.

[0466] CAM-9 was obtained by heat treatment at 700°C for 5 hours in an oxygen atmosphere. The powder containing Ni, Co and Al has a composite phase containing Nb as element X on its surface.

[0467] 2. Evaluation of CAM-9

[0468] Compositional analysis of CAM-9 yielded results of m = -0.04, n = 0.12, and p = 0.09. Element M was Co, and elements X were Al and Nb.

[0469] The results of Cx, Cy, Cz, Cx / Cy, Cy / Cz, initial discharge capacity and cycle maintenance rate of CAM-9 are recorded in Tables 1-2.

[0470] Comparative Example 3

[0471] The compound containing element X is designated as alumina (particle size D). 50 =3.5μm), and mixed at a ratio of 8.5 mol% of the molar amount of element X relative to the total molar amount of metal elements other than Li in LiMO-1, otherwise the same operation as in Example 1 is performed.

[0472] CAM-10 was obtained by heat treatment at 600°C for 5 hours in an oxygen atmosphere. The powder containing Ni, Co and Al has a composite phase containing Al as element X on its surface.

[0473] 2. Evaluation of CAM-10

[0474] Compositional analysis of CAM-10 yielded results of m = -0.05, n = 0.12, and p = 0.09, with element M being Co and element X being Al.

[0475] The results of Cx, Cy, Cz, Cx / Cy, Cy / Cz, initial discharge capacity and cycle maintenance rate of CAM-10 are recorded in Tables 1-2.

[0476] Example 8

[0477] The compound containing element X is designated as magnesium oxide (D). 50 =0.1μm), and mixed at a ratio of 4.7 mol% of the molar amount of element X relative to the total molar amount of metal elements other than Li in LiMO-1, otherwise the same operation as in Example 1 is performed.

[0478] CAM-11 was obtained by heat treatment at 400°C for 5 hours in an oxygen atmosphere. The powder containing Ni, Co and Al has a composite phase containing Mg as element X on its surface.

[0479] 2. Evaluation of CAM-11

[0480] Compositional analysis of CAM-11 yielded results of m = 0.04, n = 0.05, and p = 0.09. Element M was Co, and elements X were Al and Mg.

[0481] The results of Cx, Cy, Cz, Cx / Cy, Cy / Cz, initial discharge capacity and cycle maintenance rate of CAM-11 are recorded in Tables 1-2.

[0482] Example 9

[0483] The compound containing element X is designated as magnesium sulfate (D). 50 =1.9μm), and mixed at a ratio of 4.7 mol% of the molar amount of element X relative to the total molar amount of metal elements other than Li in LiMO-1, otherwise the same operation as in Example 1 was performed.

[0484] CAM-12 was obtained by heat treatment at 400°C for 5 hours in an oxygen atmosphere. The surface of the LiMO-1 powder containing Ni, Co and Al has a composite phase containing Mg as element X.

[0485] 2. Evaluation of CAM-12

[0486] Compositional analysis of CAM-12 yielded results of m = 0.05, n = 0.04, and p = 0.09. Element M was Co, and elements X were Al and Mg.

[0487] The results of Cx, Cy, Cz, Cx / Cy, Cy / Cz, initial discharge capacity and cycle maintenance rate of CAM-12 are recorded in Tables 1-2.

[0488] [Table 1]

[0489]

[0490]

[0491] Symbol Explanation

[0492] 1: Separator, 2: Positive electrode, 3: Negative electrode, 4: Electrode assembly, 5: Battery can, 6: Electrolyte, 7: Top insulator, 8: Sealing body, 10: Lithium secondary battery, 21: Positive electrode lead, 31: Negative electrode lead, 100: Laminated body, 110: Positive electrode, 111: Positive electrode active material layer, 112: Positive electrode current collector, 113: External terminal, 120: Negative electrode, 121: Negative electrode active material layer, 122: Negative electrode current collector, 123: External terminal, 130: Solid electrolyte layer, 200: Outer packaging, 200a: Opening, 1000: All-solid-state lithium-ion secondary battery.

Claims

1. A positive electrode active material for a lithium secondary battery, comprising at least Li, Ni, element X and carbon atoms, wherein element X is one or more elements selected from the group consisting of Al, Ti, Nb, B, W, Zr, Mg, Sn and P, and satisfies (1) and (3) below, Cz satisfies 0 < Cz ≤ 0.4, and Cy satisfies 0 < Cy ≤ 50. (1) 0.1≤Cx / Cy≤10 (3) 0 < Cy / Cz ≤ 375 In (1) or (3), Cx represents the mass percentage of element X, determined by X-ray photoelectron spectroscopy. Cy is the mass percentage of the carbon atom present in the C1s spectrum obtained by X-ray photoelectron spectroscopy, calculated from the peak area of ​​the peak with a bonding energy of 290±5 eV. The peak with a bonding energy of 290±5 eV represents a carbon atom in the carbonate group. Cz represents the mass percentage of the carbon atoms present, determined by combustion-infrared absorption spectrometry. The positive electrode active material of the lithium secondary battery is represented by the following formula (I), and further contains carbon atoms. Li[Li m (Ni （1-n-p） X n M p ) 1-m ]O2 (I) in, -0.1≤m≤0.2, 0<p<0.6 and 0<n≤0.2; element M is one or more elements selected from the group consisting of Co, Mn, Fe, Cu, Mo, Zn, Ga and V.

2. The positive electrode active material for lithium secondary batteries according to claim 1, wherein, 0 < Cy / Cz ≤ 100.

3. The positive electrode active material for lithium secondary batteries according to claim 1, wherein, 10≤Cy / Cz≤159.

2.

4. The positive electrode active material for lithium secondary batteries according to claim 1, wherein, 25≤Cy / Cz≤350.

5. The positive electrode active material for lithium secondary batteries according to claim 1, wherein, 25.0≤Cy / Cz≤332.

3.

6. The positive electrode active material for lithium secondary batteries according to any one of claims 1 to 5, wherein, 0.2≤Cx / Cy≤9.

0.

7. The positive electrode active material for lithium secondary batteries according to any one of claims 1 to 5, wherein, 2.6≤Cx / Cy≤6.

15.

8. The positive electrode active material for lithium secondary batteries according to any one of claims 1 to 5, wherein, 0.88≤Cx / Cy≤1.

1.

9. The positive electrode active material for lithium secondary batteries according to any one of claims 1 to 5, wherein, The value of Cy is 4.6 ≤ Cy ≤ 40.

10. The positive electrode active material for lithium secondary batteries according to any one of claims 1 to 5, wherein, The value of Cz is 0.03 ≤ Cz ≤ 0.

35.

11. The positive electrode active material for lithium secondary batteries according to any one of claims 1 to 5, wherein, The value of Cz is 0.05 ≤ Cz ≤ 0.

3.

12. The positive electrode active material for lithium secondary batteries according to any one of claims 1 to 5, wherein, The value of Cx is 0 < Cx ≤ 95.

13. The positive electrode active material for lithium secondary batteries according to any one of claims 1 to 5, wherein, 0≤m≤0.1, 0.08≤p≤0.4 and 0.0002≤n≤0.

15.

14. The positive electrode active material for lithium secondary batteries according to any one of claims 1 to 5, wherein, The positive electrode active material for the lithium secondary battery comprises a lithium metal composite oxide and a composite phase. The lithium metal composite oxide contains Li, Ni, and one or more elements selected from the group consisting of elements M and Al. The composite phase contains element X, wherein element M is one or more elements selected from the group consisting of Co, Mn, Fe, Cu, Mo, Zn, Ga, and V.

15. The positive electrode active material for lithium secondary batteries according to any one of claims 1 to 5, wherein the BET specific surface area is 2.0 m². 2 / g or less.

16. A positive electrode for a lithium secondary battery, comprising the positive electrode active material for a lithium secondary battery as described in any one of claims 1 to 15.

17. A lithium secondary battery having a positive electrode for a lithium secondary battery as described in claim 16.

18. A method for manufacturing a positive electrode active material for a lithium secondary battery according to any one of claims 1 to 15, comprising the following steps (a), (b) and (c) in sequence. Step (a): A step of mixing a metal composite compound containing at least Ni with a lithium compound and calcining it to obtain a lithium metal composite oxide; Step (b): A step of mixing the lithium metal composite oxide with a compound containing element X in a ratio of at least 1.0 mol% to less than 5.5 mol% of the total molar amount of element X relative to the total molar amount of metal elements other than lithium atoms contained in the lithium metal composite oxide to obtain a mixture; wherein element X is one or more elements selected from the group consisting of Al, Ti, Nb, B, W, Zr, Mg, Sn, and P, and the 50% cumulative volumetric particle size D of the compound containing element X is... 50 The size is greater than 0.02 μm and less than 90 μm; Step (c): A step of heat-treating the mixture in an oxygen-containing atmosphere at a temperature of 200°C or higher and 600°C or lower.

19. The method for manufacturing the positive electrode active material for lithium secondary batteries according to claim 18, wherein, The process (a) includes the steps of mixing a metal composite compound with a lithium compound and calcining it, and crushing the resulting calcined material using a stone mill crusher.

20. The method for manufacturing a positive electrode active material for a lithium secondary battery according to claim 18 or 19, wherein, The process (b) includes a step of mixing the covering material containing element X with a lithium metal composite oxide in water or an atmosphere containing water and carbon dioxide.

21. The method for manufacturing a positive electrode active material for a lithium secondary battery according to claim 18 or 19, wherein, The process (b) includes mixing a covering material containing element X with a lithium metal composite oxide and maintaining the mixture in water or an atmosphere containing water and carbon dioxide.

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