Lithium metal composite oxide, positive electrode active material for lithium secondary battery, positive electrode for lithium secondary battery, and lithium secondary battery

Abstract

The present invention relates to a lithium metal composite oxide having a layered structure, comprising at least Li, Ni, and an element X, wherein the element X is one or more elements selected from the group consisting of Co, Mn, Fe, Cu, Ti, Mg, Al, B, W, Mo, Nb, Zn, Sn, Zr, Ga, La, and V, and wherein the physical property values ​​determined from the nitrogen adsorption isotherm obtained by a gas adsorption method satisfy conditions (1) and (2).

Description

Technical Field

[0001] The present invention relates to a lithium metal composite oxide, a positive electrode active material for a lithium secondary battery, a positive electrode for a lithium secondary battery, and a lithium secondary battery.

[0002] This application claims priority based on Japanese Patent Application No. 2020-030445 filed in Japan on February 26, 2020, the contents of which are incorporated herein by reference. Background Art

[0003] Lithium secondary batteries are already being put into practical use not only in small power sources for mobile phones and laptop computers, but are also being used in medium- and large-sized power sources for applications such as automobiles and power storage. Lithium secondary batteries have a positive electrode containing a positive electrode active material. Lithium metal composite oxides are used as the positive electrode active material.

[0004] Known lithium metal composite oxides are composed of secondary particles formed by the aggregation of primary particles. The secondary particles, as aggregates, have numerous pores. The presence of numerous pores increases the contact area with the electrolyte, which can improve various battery performances.

[0005] When manufacturing lithium secondary batteries, a positive electrode active material comprising a lithium metal composite oxide is mixed with a conductive agent. Lithium metal composite oxide particles with a high proportion of secondary particles have a small surface area. Therefore, to ensure sufficient conductivity, the amount of conductive agent must be increased. This reduces the overall discharge capacity per unit mass and per unit volume of the battery.

[0006] Against this background, attempts have been made to control the pore distribution and specific surface area of ​​lithium metal composite oxides.

[0007] For example, Patent Document 1 describes a positive electrode active material for a non-aqueous electrolyte secondary battery, wherein, in a pore distribution measurement by a nitrogen adsorption method, the average volume of pores having an average diameter of 40 nm or less is 0.001 to 0.008 cm 3 / g is set as one of the components.

[0008] Patent Document 2 describes a positive electrode having a configuration in which the pore specific surface area (S1) measured by mercury intrusion porosimetry and the pore volume (V1) obtained by pore distribution measurement satisfy a specific formula.

[0009] Prior art literature

[0010] Patent Literature

[0011] Patent Document 1: JP-A-2007-257985

[0012] Patent Document 2: WO2012 / 111813A1 Summary of the Invention

[0013] Problems to be solved by the invention

[0014] However, batteries for vehicles such as electric vehicles are required not only to have a high capacity but also to exhibit high output characteristics, that is, high discharge rate characteristics.

[0015] In this specification, the discharge rate characteristics are evaluated using the discharge capacity when discharging at a constant current of 5CA and the discharge capacity when discharging at a constant current of 1CA, and the 5CA / 1CA discharge capacity retention ratio is calculated using the following formula.

[0016] A higher 5CA / 1CA discharge capacity retention rate means higher discharge rate characteristics and higher output power of the lithium secondary battery.

[0017] 5CA / 1CA discharge capacity retention rate (%)

[0018] =Discharge capacity at 5CA / Discharge capacity at 1CA×100

[0019] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a lithium metal composite oxide having high discharge rate characteristics and cycle characteristics, a positive electrode active material for a lithium secondary battery, a positive electrode for a lithium secondary battery, and a lithium secondary battery.

[0020] Means for solving problems

[0021] That is, the present invention includes the following inventions [1] to

[10] .

[0022] [1] A lithium metal composite oxide having a layered structure, comprising at least Li, Ni and an element X, wherein the element X is one or more elements selected from the group consisting of Co, Mn, Fe, Cu, Ti, Mg, Al, B, W, Mo, Nb, Zn, Sn, Zr, Ga, La and V, and wherein the physical properties determined by measuring the adsorption isotherm of nitrogen obtained by a gas adsorption method satisfy the following (1) and (2).

[0023] (1): The total pore volume V calculated from the nitrogen adsorption amount at a relative pressure (p / p0) of 0.99 in the nitrogen adsorption isotherm satisfies 0.005 cm 3 / g or less.

[0024] (2): The value of the following formula (A) satisfies 0.18 or more.

[0025] S / (V×1000) Formula (A)

[0026] (In formula (A), S is the specific surface area of ​​the lithium metal composite oxide obtained by the BET method (unit: m 2 V is the total pore volume of the lithium metal composite oxide (unit: cm) obtained from the nitrogen adsorption amount at a relative pressure (p / p0) of 0.99 in the adsorption isotherm. 3 / g))

[0027] [2] The lithium metal composite oxide according to [1], which satisfies the following formula (I).

[0028] Li[Li x (Ni (1-y-z-w) Co y Mn z M w ) 1-x ]O2 (I)

[0029] (wherein, -0.1≤x≤0.2, 0≤y≤0.4, 0≤z≤0.4, 0≤w≤0.1, y+z+w<1, and M represents one or more elements selected from the group consisting of Fe, Cu, Ti, Mg, Al, B, W, Mo, Nb, Zn, Sn, Zr, Ga, La, and V)

[0030] [3] The lithium metal composite oxide according to [1] or [2], wherein the 50% cumulative diameter, i.e., the average particle size D, obtained by particle size distribution measurement is 50 The thickness satisfies a range of 1 μm to 10 μm.

[0031] [4] The lithium metal composite oxide according to any one of [1] to [3], wherein in the nitrogen adsorption isotherm measurement and the desorption isotherm measured immediately after the adsorption isotherm, the area of ​​the region formed between the adsorption isotherm and the desorption isotherm in the range of relative pressure (p / p0) of 0.5 or more and 0.9 or less satisfies 0.02 cm 3 / g or less.

[0032] [5] The lithium metal composite oxide according to any one of [1] to [4], wherein the maximum value of the log differential pore volume in the pore distribution with a pore diameter of 200 nm or less determined by the nitrogen adsorption isotherm measurement satisfies 0.03 cm 3 / (g·nm) or less.

[0033] [6] The lithium metal composite oxide according to any one of [1] to [5], wherein the specific surface area S satisfies 0.1 m 2 / g or above and 1.5m 2 / g or less.

[0034] [7] The lithium metal composite oxide according to any one of [1] to [6], wherein the tap density satisfies 1.2 g / cm 3 Above and 2.5g / cm 3 the following.

[0035] [8] A positive electrode active material for a lithium secondary battery, comprising the lithium metal composite oxide according to any one of [1] to [7].

[0036] [9] A positive electrode for a lithium secondary battery, comprising the positive electrode active material for a lithium secondary battery according to [8].

[0037]

[10] A lithium secondary battery comprising the positive electrode for a lithium secondary battery according to [9].

[0038] Effects of the Invention

[0039] According to the present invention, a lithium metal composite oxide having high discharge rate characteristics and cycle characteristics, a positive electrode active material for a lithium secondary battery, a positive electrode for a lithium secondary battery, and a lithium secondary battery can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1A This is a diagram schematically showing the structure of an example of a lithium secondary battery.

[0041] Figure 1B This is a diagram schematically showing the structure of an example of a lithium secondary battery.

[0042] Figure 2 This is a graph showing the relationship between the nitrogen adsorption amount of the lithium metal composite oxide of Example 1 and the relative pressure.

[0043] Figure 3 This is a graph showing the relationship between the nitrogen adsorption amount of the lithium metal composite oxide of Comparative Example 3 and the relative pressure.

[0044] Figure 4 This is a schematic diagram showing a stacked body included in an all-solid-state lithium-ion battery.

[0045] Figure 5 This is a schematic diagram showing the overall structure of an all-solid-state lithium-ion battery. DETAILED DESCRIPTION

[0046] In this specification, a metal composite compound is hereinafter referred to as "MCC", a lithium metal composite oxide is hereinafter referred to as "LiMO", and a cathode active material for lithium secondary batteries is hereinafter referred to as "CAM".

[0047] <limo>

[0048] This embodiment is LiMO having a layered structure.

[0049] In one embodiment of the present invention, LiMO is formed only of primary particles.

[0050] In one embodiment of the present invention, LiMO is composed of secondary particles, which are aggregates of primary particles, and primary particles that exist independently of the secondary particles.

[0051] In one embodiment of the present invention, LiMO is in the form of powder.

[0052] In the present embodiment, “primary particles” refer to particles that appear to have no grain boundaries when observed at a viewing angle of 5000 to 20000 times using a scanning electron microscope or the like.

[0053] In the present embodiment, the “secondary particles” refer to particles formed by aggregation of the primary particles, and are particles having a spherical or substantially spherical shape.

[0054] When LiMO is composed of secondary particles, which are aggregates of primary particles, and primary particles existing independently of the secondary particles, the ratio of the number of primary particles contained in LiMO to the total number of secondary particles and primary particles is preferably 20% or greater, more preferably 30% or greater, and particularly preferably 50% or greater. The upper limit is not particularly limited, but is less than 100%, preferably 90% or less.

[0055] When calculating the number of primary particles, the primary particles constituting the secondary particles are not counted, and only the number of primary particles existing independently of the secondary particles is counted.

[0056] In the present embodiment, the ratio of the number of primary particles contained in LiMO to the total number of secondary particles and primary particles is determined by the following method.

[0057] First, LiMO is placed on a conductive sheet attached to a sample stage, and is dispersed so that primary particles and secondary particles, which are aggregates of the primary particles, exist independently without contacting each other.

[0058] Thereafter, the sample was irradiated with electron beams at an accelerating voltage of 20 kV using a scanning electron microscope (SEM, for example, JSM-5510 manufactured by JEOL Ltd.) for SEM observation.

[0059] Next, 200 particles were randomly extracted from an image (SEM photograph) obtained by SEM observation, and this number was set as the total number of secondary particles and the number of primary particles.

[0060] Next, the number of primary particles existing independently of the secondary particles included in the extracted 200 particles is calculated.

[0061] The obtained number of primary particles is divided by the total number of secondary particles and primary particles to calculate the ratio of the number of primary particles to the total number of secondary particles and primary particles.

[0062] The magnification of the SEM photograph may be any magnification that allows identification of the particle morphology of the target LiMO, and is preferably 1000 times or more and 30000 times or less.

[0063] <Calculation Method of the Content of Independent Primary Particles>

[0064] LiMO powder was observed using a scanning electron microscope at 20,000x magnification, and the number of independent primary and secondary particles within the observed field of view was counted. The number of primary particles was designated N1, and the number of secondary particles was designated N2. The primary particle ratio was calculated as N1 / (N1+N2)[%]. If the number of observable particles was less than 50, multiple fields of view were continuously observed until 50 particles were confirmed.

[0065] LiMO contains at least Li, Ni and element X.

[0066] The element X is one or more elements selected from the group consisting of Co, Mn, Fe, Cu, Ti, Mg, Al, B, W, Mo, Nb, Zn, Sn, Zr, Ga, La, and V.

[0067] The physical properties of LiMO determined from nitrogen adsorption isotherm measurements by a gas adsorption method satisfy (1) and (2).

[0068] By using a gas adsorption method using nitrogen gas, it is possible to measure microscopic pores having a pore diameter of 200 nm or less.

[0069] The term "pores" used herein refers to microscopic spaces that connect the outer surface of a secondary particle to the interior. These spaces are formed by the aggregation of primary particles. (1)

[0071] Specifically, as (1), the total pore volume V obtained from the nitrogen adsorption amount when the relative pressure, i.e., p / p0, is 0.99 in the nitrogen adsorption isotherm satisfies 0.005 cm 3 / g or less, preferably 0.004cm 3 / g or less, more preferably 0.0035cm 3 Hereinafter, the "total pore volume V" may be abbreviated as "V".

[0072] LiMO in which V is equal to or less than the above upper limit means that it contains secondary particles with few pores.

[0073] Ideally, V is preferably 0 cm 3 / g, but due to the relationship with the formula (A) in (2) described later, it is preferably more than 0 cm 3 / g, and as an example of the lower limit, 0.0001 cm 3 / g or more, 0.0002cm 3 / g or above.

[0074] The above-mentioned upper limit value and lower limit value of V can be arbitrarily combined.

[0075] As an example of the combination, V is 0 cm 3 / g or more and 0.005cm 3 / g or less, more than 0cm 3 / g and 0.005cm 3 / g or less, 0.0001cm 3 / g or more and 0.004cm 3 / g or less, 0.0002cm 3 / g or more and 0.003cm 3 / g or less.

[0076] [Determination of V]

[0077] The adsorption isotherm and desorption isotherm of nitrogen can be measured by the following method.

[0078] First, 10 g of LiMO was subjected to a vacuum degassing treatment at 150° C. for 8 hours using a vacuum heat treatment apparatus.

[0079] After the vacuum degassing treatment, the nitrogen adsorption isotherm and nitrogen desorption isotherm of LiMO at liquid nitrogen temperature (77 K) were measured using an adsorption isotherm and desorption isotherm measuring apparatus.

[0080] As the vacuum heat treatment apparatus, for example, BELSORP-vacII manufactured by Microtrac BEL Co., Ltd. can be used.

[0081] As an adsorption isotherm and desorption isotherm measuring apparatus, for example, BELSORP-mini manufactured by Microtrac BEL Co., Ltd. can be used.

[0082] The amount of nitrogen adsorbed per unit weight of LiMO in the adsorption isotherm was calculated as expressed in terms of the volume of gaseous nitrogen at standard temperature and pressure (STP).

[0083] The amount of nitrogen desorbed per unit weight of LiMO in the desorption isotherm was calculated as expressed in terms of the volume of gaseous nitrogen at standard temperature and pressure (STP).

[0084] The total pore volume is the nitrogen adsorption amount when the relative pressure of the adsorption isotherm, i.e., p / p0, is 0.99, which is set as Tcm 3 (STP) / g is calculated by the following formula.

[0085] In the following formula, the volume of 1 mol of gas under standard conditions is set to 22414 cm 3 , the molecular weight M of nitrogen is set to 28.013 g / mol, and the density ρ of nitrogen in the liquid phase is set to 0.808 g / cm 3 .

[0086] V(cm 3 / g)=T / 22414×M / ρ

[0087] A relative pressure close to 1, or 0.99, is near saturated vapor pressure. Therefore, it is believed that nitrogen is condensing in the pores through capillary condensation, essentially existing in a liquid phase. The total pore volume can be calculated by converting the amount of nitrogen assumed to be in a liquid phase into the standard gas volume. (2)

[0089] The value of the following formula (A) of LiMO satisfies 0.18 or more.

[0090] S / (V×1000) Formula (A)

[0091] (In formula (A), S is the specific surface area obtained by the BET method (unit: m 2 V is the total pore volume (unit: cm) obtained from the nitrogen adsorption amount at a relative pressure of 0.99 in the adsorption isotherm. 3 / g))

[0092] The value of formula (A) is preferably 0.20 or greater, more preferably 0.22 or greater, and particularly preferably 0.24 or greater. The upper limit of the value of formula (A) is not particularly limited, but is preferably less than 0.50.

[0093] When the value of formula (A) is greater than or equal to the above lower limit, it means that the proportion of particles having a specific surface area derived from outside the pores larger than the specific surface area derived from inside the pores of the secondary particles is high.

[0094] Here, the "specific surface area derived from within the pores" specifically refers to the specific surface area of ​​the walls within the pores. The "specific surface area derived from outside the pores" specifically refers to the specific surface area of ​​the surfaces of the primary particles or secondary particles.

[0095] The above-mentioned upper limit value and lower limit value of the value of formula (A) can be arbitrarily combined.

[0096] Examples of the combination include a value of formula (A) of 0.20 or more and less than 0.50, 0.22 or more and less than 0.50, and 0.24 or more and less than 0.50.

[0097] In formula (A), V is calculated using the method described in the above-mentioned [Measurement of V].

[0098] [Determination of S]

[0099] In formula (A), S is determined by measuring the nitrogen adsorption isotherm of LiMO. Specifically, the nitrogen adsorption amount measured up to a relative pressure of 0.4 is used to calculate the S by the BET multipoint method (unit: m 2 / g). The amount of nitrogen adsorption up to a relative pressure of 0.4 was measured in the process of reaching a relative pressure of 0.99 in the total pore volume measurement in (1).

[0100] LiMO satisfying (1) means that the pore volume is small, that is, the space formed by the aggregation of primary particles is small.

[0101] Furthermore, LiMO satisfying (2) means that, among the specific surface areas of primary particles or secondary particles, the ratio of the specific surface area derived from the inside of the pores is small, and the specific surface area derived from the outside of the pores is large.

[0102] This means that the amount of secondary particles, which are aggregates of primary particles, is small, and the amount of independently existing primary particles is large.

[0103] It is difficult for the conductive material to enter the interior of the pores having a size that satisfies (1). The conductive material that cannot enter the interior of the pores exists on the surface of the pores.

[0104] LiMO that satisfies (2) has a large surface area outside the pores, and can contact the conductive material on the surface of the primary particles or the surface of the secondary particles. Therefore, it is believed that the contact frequency between LiMO and the conductive material is likely to be sufficiently increased.

[0105] When LiMO of this embodiment is used as the positive electrode active material, the contact efficiency with the conductive agent is easily improved. Therefore, the interface resistance between the positive electrode active material and the conductive agent is reduced, and the discharge rate characteristics and cycle characteristics are improved.

[0106] Specific surface area S

[0107] S preferably meets 0.1m 2 / g or more, more preferably 0.2m 2 / g or more, more preferably 0.3m 2 / g or above.

[0108] S preferably meets 1.5m 2 / g or less, more preferably 1.2m 2 / g or less, particularly preferably satisfying 1.0m 2 / g or less.

[0109] The above upper and lower limits can be combined arbitrarily. As an example of the combination, S is 0.1m 2 / g or above and 1.5m 2 / g or less, 0.2m 2 / g or above and 1.2m 2 / g or less, 0.3m 2 / g or above and 1.0m 2 / g or less.

[0110] Composition

[0111] LiMO in this embodiment preferably satisfies the following formula (I).

[0112] Li[Li x (Ni (1-y-z-w) Co y Mn z M w ) 1-x ]O2 (I)

[0113] (wherein, -0.1≤x≤0.2, 0≤y≤0.4, 0≤z≤0.4, 0≤w≤0.1, y+z+w<1, and M represents one or more elements selected from the group consisting of Fe, Cu, Ti, Mg, Al, W, B, Mo, Nb, Zn, Sn, Zr, Ga, La, and V)

[0114] (About x)

[0115] From the perspective of obtaining a lithium secondary battery with good cycle characteristics, x in the composition formula (I) is preferably greater than 0, more preferably greater than 0.01, and further preferably greater than 0.02. In addition, from the perspective of obtaining a lithium secondary battery with a higher initial coulombic efficiency, x in the composition formula (I) is preferably less than 0.15, and more preferably less than 0.10.

[0116] It should be noted that the term "good cycle characteristics" in this specification refers to a characteristic in which the battery capacity decreases little by repeated charge and discharge, and means that the ratio of the capacity at re-measurement to the initial capacity is unlikely to decrease.

[0117] In this specification, the term "first coulombic efficiency" is calculated as "(first discharge capacity) / (first charge capacity) × 100 (%)." A secondary battery with a high first coulombic efficiency has a low irreversible capacity during the first charge and discharge, making it easier to achieve a higher capacity per unit volume and weight.

[0118] The upper limit and lower limit of x may be arbitrarily combined. In composition formula (I), x may be from -0.1 to 0.15, or from -0.1 to 0.10.

[0119] x may be greater than 0 and less than 0.20, greater than 0 and less than 0.15, or greater than 0 and less than 0.10.

[0120] x may be 0.01 or more and 0.20 or less, 0.01 or more and 0.15 or less, or 0.01 or more and 0.10 or less.

[0121] x may be 0.02 or more and 0.2 or less, 0.02 or more and 0.15 or less, or 0.02 or more and 0.10 or less.

[0122] x is preferably 0 <x≤0.20。

[0123] (About y)

[0124] In addition, from the perspective of obtaining a lithium secondary battery with low internal resistance, y in the composition formula (I) is preferably greater than 0, more preferably greater than 0.005, further preferably greater than 0.01, and particularly preferably greater than 0.05. In addition, from the perspective of obtaining a lithium secondary battery with high thermal stability, y in the composition formula (I) is more preferably less than 0.35, further preferably less than 0.33, and even more preferably less than 0.30.

[0125] The upper limit and lower limit of y may be arbitrarily combined. In composition formula (I), y may be 0 or more and 0.35 or less, 0 or more and 0.33 or less, or 0 or more and 0.30 or less.

[0126] y may be greater than 0 and less than 0.40, greater than 0 and less than 0.35, greater than 0 and less than 0.33, or greater than 0 and less than 0.30.

[0127] y may be 0.005 or more and 0.40 or less, 0.005 or more and 0.35 or less, 0.005 or more and 0.33 or less, or 0.005 or more and 0.30 or less.

[0128] y can be 0.01 or more and 0.40 or less, can be 0.01 or more and 0.35 or less, can be 0.01 or more and 0.33 or less, and can also be 0.01 or more and 0.30 or less.

[0129] y can be 0.05 or more and 0.40 or less, can be 0.05 or more and 0.35 or less, can be 0.05 or more and 0.33 or less, and can also be 0.05 or more and 0.30 or less.

[0130] y preferably satisfies 0 < y ≤ 0.40.

[0131] In the compositional formula (I), 0 < x ≤ 0.10 is satisfied, and more preferably 0 < y ≤ 0.40 is satisfied.

[0132] (Regarding z)

[0133] Furthermore, from the viewpoint of obtaining a lithium secondary battery with high cycle characteristics, z in the compositional formula (I) is preferably 0.01 or more, more preferably 0.02 or more, and further preferably 0.1 or more. Furthermore, from the viewpoint of obtaining a lithium secondary battery with high storage stability at high temperatures (for example, in an environment of 60 °C), z in the compositional formula (I) is preferably 0.39 or less, more preferably 0.38 or less, and further preferably 0.35 or less.

[0134] The upper limit value and the lower limit value of z can be arbitrarily combined. In the compositional formula (I), z can be 0 or more and 0.39 or less, can be 0 or more and 0.38 or less, and can also be 0 or more and 0.35 or less.

[0135] z can be 0.01 or more and 0.40 or less, can be 0.01 or more and 0.39 or less, can be 0.01 or more and 0.38 or less, and can also be 0.01 or more and 0.35 or less.

[0136] z can be 0.02 or more and 0.40 or less, can be 0.02 or more and 0.39 or less, can be 0.02 or more and 0.38 or less, and can also be 0.02 or more and 0.35 or less.

[0137] z can be 0.10 or more and 0.40 or less, can be 0.10 or more and 0.39 or less, can be 0.10 or more and 0.38 or less, and can also be 0.10 or more and 0.35 or less.

[0138] (Regarding w)

[0139] In addition, from the perspective of obtaining a lithium secondary battery with low internal resistance, w in the composition formula (I) is preferably greater than 0, more preferably greater than 0.0005, and even more preferably greater than 0.001. In addition, from the perspective of obtaining a lithium secondary battery with a large discharge capacity at a high current rate, w in the composition formula (I) is preferably less than 0.09, more preferably less than 0.08, and even more preferably less than 0.07.

[0140] The upper limit and lower limit of w may be arbitrarily combined. In composition formula (I), w may be 0 or more and 0.09 or less, 0 or more and 0.08 or less, or 0 or more and 0.07 or less.

[0141] w may be greater than 0 and less than 0.10, greater than 0 and less than 0.09, greater than 0 and less than 0.08, or greater than 0 and less than 0.07.

[0142] w may be 0.0005 or more and 0.10 or less, 0.0005 or more and 0.09 or less, 0.0005 or more and 0.08 or less, or 0.0005 or more and 0.07 or less.

[0143] w may be 0.001 or more and 0.10 or less, 0.001 or more and 0.09 or less, 0.001 or more and 0.08 or less, or 0.001 or more and 0.07 or less.

[0144] (About y+z+w)

[0145] Furthermore, from the viewpoint of obtaining a lithium secondary battery with a large battery capacity, y+z+w in composition formula (I) preferably satisfies 0.50 or less, more preferably satisfies 0.25 or less, and even more preferably satisfies 0.20 or less.

[0146] (About M)

[0147] M in composition formula (I) represents one or more elements selected from the group consisting of Fe, Cu, Ti, Mg, Al, W, B, Mo, Nb, Zn, Sn, Zr, Ga, La, and V.

[0148] In addition, from the viewpoint of obtaining a lithium secondary battery with high cycle characteristics, M in composition formula (I) is preferably selected from one or more elements in the group consisting of Ti, Mg, Al, W, B, and Zr, and more preferably selected from one or more elements in the group consisting of Al and Zr. In addition, from the viewpoint of obtaining a lithium secondary battery with high thermal stability, it is preferably selected from one or more elements in the group consisting of Ti, Al, W, B, and Zr.

[0149] An example of a preferred combination of x, y, z, and w is: x is 0.02 to 0.3, y is 0.05 to 0.30, z is 0.02 to 0.35, and w is 0 to 0.07. Examples include LiMO with x = 0.05, y = 0.20, z = 0.30, and w = 0; LiMO with x = 0.05, y = 0.08, z = 0.04, and w = 0; and LiMO with x = 0.25, y = 0.07, z = 0.02, and w = 0.

[0150] [Composition Analysis]

[0151] The composition analysis of LiMO was performed by dissolving the obtained LiMO powder in hydrochloric acid and then using an ICP emission spectrometer (SPS3000 manufactured by SII NanoTechnology Inc.).

[0152] Average particle size

[0153] The 50% cumulative diameter of LiMO, i.e. the average particle size D, is determined from the particle size distribution measurement. 50 It is preferably 1 μm or more and 10 μm or less. 50 The upper limit of the average particle size D is more preferably 8 μm or less, and further preferably 7 μm or less. 50 The lower limit of is more preferably 1.5 μm or more, and further preferably 2 μm or more.

[0154] The above D 50 The upper limit and lower limit of can be combined arbitrarily. As an example of combination, D 50 It is 1.5 μm or more and 8 μm or less, or 2 μm or more and 7 μm or less.

[0155] [Average particle size D 50 Determination of

[0156] The cumulative particle size of LiMO was measured using the following method. The "volume-based cumulative particle size" below can be measured using a method based on the laser diffraction scattering method. Particle size distribution measurement based on the laser diffraction scattering method is referred to as "laser diffraction particle size distribution measurement."

[0157] First, 0.1 g of LiMO powder was added to 50 ml of a 0.2 mass % sodium hexametaphosphate aqueous solution to obtain a dispersion in which the LiMO powder was dispersed.

[0158] Next, the obtained dispersion is measured for particle size distribution using a laser diffraction scattering particle size distribution analyzer to obtain a volume-based cumulative particle size distribution curve. The particle size distribution measurement range may be set to 0 μm or more and 2000 μm or less.

[0159] As a laser diffraction scattering particle size distribution measuring apparatus, for example, MICROTRAC MT3300EXII manufactured by Microtrac BEL Co., Ltd. can be used.

[0160] In the obtained cumulative particle size distribution curve, when the entire volume is set as 100%, the particle size value at the point where the cumulative volume from the fine particle side becomes 50% is set as the 50% cumulative volume particle size D. 50 (μm).

[0161] The area between the adsorption isotherm and the desorption isotherm

[0162] [Measurement of S1]

[0163] The area of ​​the region formed between the adsorption isotherm and the desorption isotherm in the range of relative pressure p / p0 of 0.5 or more and 0.9 or less is S1.

[0164] To determine S1, specifically, first, integration is performed within the relative pressure range of p / p0 being 0.5 or more and 0.9 or less to determine the areas of the desorption isotherm and the adsorption isotherm.

[0165] Next, the area of ​​the adsorption isotherm is subtracted from the area of ​​the desorption isotherm, and the difference is defined as S1.

[0166] S1 preferably satisfies 0.02cm 3 / g or less, more preferably 0.005cm 3 / g or less, particularly preferably satisfying 0.003cm 3 / g or less.

[0167] S1 preferably satisfies 0cm 3 / g or above.

[0168] As a combination of the upper limit and lower limit of S1, S1 is 0 cm 3 / g or more and 0.02cm 3 / g or less, 0cm 3 / g or more and 0.005cm 3 / g or less, 0cm 3 / g or more and 0.003cm 3 / g or less.

[0169] If the powder being measured has pores, the amount of nitrogen molecules adsorbed includes nitrogen molecules trapped in the pores in a condensed state through capillary condensation. Gas molecules trapped in the pores are less likely to escape even when the partial pressure is reduced. This results in a difference between the adsorption and desorption isotherms.

[0170] For example, if the pores of the powder being measured have a bottleneck shape, there is a difference in inner diameter between the widest portion of the pore space and the inner diameter of the bottleneck. The greater this difference in inner diameter, the greater the hysteresis observed between the adsorption isotherm and the desorption isotherm. In this specification, the bottleneck shape refers to the constricted portion of the pore. The bottleneck portion refers to the portion of the constricted portion of the pore with the smallest inner diameter.

[0171] On the other hand, LiMO not only has few micropores smaller than 200 nm, as measured by gas adsorption, within secondary particles, between primary particles not constituting secondary particles, and between secondary particles, but also has a low proportion of bottleneck-type pores. Specifically, the aforementioned difference in inner diameter is small, making it difficult for the adsorption isotherm and desorption isotherm to differ. Therefore, S1 is likely to be below the aforementioned upper limit.

[0172] Log differential pore volume

[0173] In the pore distribution of LiMO determined by nitrogen adsorption isotherm measurement, the maximum value of the log differential pore volume in the region with a pore diameter of 200 nm or less preferably satisfies 0.03 cm 3 / (g·nm) or less, more preferably 0.02cm 3 / (g·nm) or less, and more preferably 0.01cm 3 / (g·nm) or less.

[0174] The maximum value of the log differential pore volume can also be 0.001 cm 3 / (g·nm) or more, 0.002cm 3 / (g·nm) or more, 0.003cm 3 / (g·nm) or above.

[0175] The above upper limit values ​​and lower limit values ​​can be arbitrarily combined.

[0176] As an example of the combination, 0.001 cm 3 / (g·nm) or more and 0.03cm 3 / (g·nm) or less, 0.002cm 3 / (g·nm) or more and 0.02cm 3 / (g·nm) or less, 0.003cm 3 / (g·nm) or more and 0.01cm 3 / (g·nm) or less.

[0177] When the peak maximum value of the log differential pore volume is equal to or less than the upper limit, it means that the proportion of particles having a small number of fine pores and having a pore diameter of 200 nm or less as measured by a gas adsorption method is high.

[0178] [Measurement of the Peak Maximum Value of Log Differential Pore Volume]

[0179] The log differential pore volume was analyzed from the nitrogen adsorption isotherm using the BJH method. In the pore diameter region of 200 nm or less, the maximum value of the log differential pore volume peak was obtained from the cumulative curve of pore diameter and pore volume.

[0180] Tapped Density

[0181] The tap density of LiMO is preferably 1.2 g / cm 3 Above and 2.5g / cm 3 As the lower limit of the tap density, it is more preferably 1.4 g / cm 3 Above, particularly preferably 1.5 g / cm 3 In addition, the upper limit of the tap density is more preferably 2.3 g / cm 3 Below, particularly preferably 2.2 g / cm 3 The above upper limit value and the above lower limit value may be arbitrarily combined.

[0182] As an example of a combination, the tap density can be 1.4 g / cm 3 Above and 2.3g / cm 3 Below, 1.5g / cm 3 Above and 2.2g / cm 3 the following.

[0183] [Measurement method of tap density]

[0184] The tap density used is a value determined by the method described in JIS R 1628-1997.

[0185] (Layered structure)

[0186] The crystal structure of LiMO is a layered structure, more preferably a hexagonal crystal structure or a monoclinic crystal structure.

[0187] The crystal structure of the hexagonal crystal form belongs to any space group selected from the group consisting of 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, 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, P63 / mmc.

[0188] In addition, the crystal structure of the monoclinic crystal form belongs to any space group selected from the group consisting of P2, P21, C2, Pm, Pc, Cm, Cc, P2 / m, P21 / m, C2 / m, P2 / c, P21 / c, C2 / c.

[0189] Among them, in order to obtain a lithium secondary battery with a high discharge capacity, the crystal structure is particularly preferably a hexagonal crystal structure belonging to the space group R-3m or a monoclinic crystal structure belonging to C2 / m.

[0190] <Manufacturing method of LiMO>

[0191] The manufacturing method of LiMO of the present embodiment will be described.

[0192] The manufacturing method of LiMO preferably sequentially includes the following manufacturing methods (1), (2), and (3).

[0193] (1) Manufacturing process of the precursor of LiMO.

[0194] (2) Mixing process of obtaining a mixture by mixing the above precursor and a lithium compound.

[0195] (3) Process of firing the above mixture to obtain LiMO.

[0196] [(1) Manufacturing process of the precursor of LiMO]

[0197] First, the precursor of LiMO is manufactured.

[0198] The precursor is MCC, in which the metals constituting the target LiMO contain a metal other than lithium. Specifically, the MCC is nickel-containing MCC containing nickel as an essential metal and element X as an optional metal. A nickel-containing metal composite hydroxide or a nickel-containing metal composite oxide can be used as the nickel-containing MCC precursor.

[0199] The precursor can be produced by a generally known coprecipitation method. As the coprecipitation method, a batch coprecipitation method or a continuous coprecipitation method can be used.

[0200] Hereinafter, a nickel-cobalt-manganese metal composite hydroxide containing nickel, cobalt, and manganese as metals will be described in detail. The nickel-cobalt-manganese metal composite hydroxide may be referred to as a "metal composite hydroxide" below.

[0201] First, a coprecipitation method, particularly a continuous coprecipitation method described in JP-A 2002-201028, is used to react a nickel salt solution, a cobalt salt solution, a manganese salt solution, and a complexing agent to produce Ni (1-y-z) Co y Mn z A metal composite hydroxide represented by (OH)2 (wherein y+z=1).

[0202] The nickel salt that is the solute of the nickel salt solution is not particularly limited, and for example, any of nickel sulfate, nickel nitrate, nickel chloride, and nickel acetate can be used.

[0203] As the cobalt salt which is the solute of the cobalt salt solution, for example, any of cobalt sulfate, cobalt nitrate, cobalt chloride, and cobalt acetate can be used.

[0204] As the manganese salt which is the solute of the manganese salt solution, for example, any one of manganese sulfate, manganese nitrate, manganese chloride, and manganese acetate can be used.

[0205] The above metal salts are used with the above Ni (1-y-z) Co y Mn z The ratio of (OH)2 is used in accordance with the composition ratio.

[0206] That is, the molar ratio of nickel in the solute of nickel salt solution, cobalt in the solute of cobalt salt solution, and manganese in the solute of manganese salt solution is the same as Ni. (1-y-z) Co y Mn z The composition ratio of becomes (1-yz):y:z accordingly.

[0207] In addition, the solvent of the nickel salt solution, the cobalt salt solution, and the manganese salt solution is water.

[0208] The complexing agent is a compound that can form a complex with nickel ions, cobalt ions, and manganese ions in an aqueous solution.

[0209] Examples of the complexing agent include ammonium ion donors, hydrazine, ethylenediaminetetraacetic acid, nitrilotriacetic acid, uracildiacetic acid, and glycine. Examples of the ammonium ion donor include ammonium sulfate, ammonium chloride, ammonium carbonate, and ammonium fluoride.

[0210] In the production process of the precursor, a complexing agent may or may not be used.

[0211] When a complexing agent is used, the molar ratio of the complexing agent contained in the mixed solution comprising the nickel salt solution, the metal salt solution of element X, and the complexing agent to the total number of moles of the metal salt is, for example, greater than 0 and not more than 2.0.

[0212] The molar ratio of the amount of the complexing agent contained in the mixed solution containing the nickel salt solution, the cobalt salt solution, the manganese salt solution, and the complexing agent to the total number of moles of the metal salt is, for example, greater than 0 and 2.0 or less.

[0213] In the coprecipitation method, to adjust the pH of the mixture containing the nickel salt solution, the optional metal salt solution, and the complexing agent, an alkali metal hydroxide is added to the mixture before the pH of the mixture changes from alkaline to neutral. The alkali metal hydroxide is, for example, sodium hydroxide or potassium hydroxide.

[0214] In addition, the pH value in this specification is defined as the value measured when the temperature of the mixed solution is 40° C. The pH of the mixed solution is measured when the temperature of the mixed solution sampled from the reaction tank reaches 40° C.

[0215] When the temperature of the sampled mixed solution was lower than 40°C, the mixed solution was heated to 40°C and the pH was measured.

[0216] When the temperature of the sampled mixed liquid exceeded 40°C, the mixed liquid was cooled until it reached 40°C, and the pH was measured.

[0217] If a complexing agent is continuously supplied to the reaction tank in addition to the above nickel salt solution, cobalt salt solution and manganese salt solution, nickel, cobalt and manganese react to generate Ni (1-y-z) Co y Mn z (OH)2.

[0218] During the reaction, the temperature of the reaction vessel is controlled within a range of, for example, 20° C. to 80° C., preferably 30° C. to 70° C.

[0219] The pH value in the reaction tank is set within a range of pH 9 to pH 13, preferably pH 10 to pH 12.5, when the temperature of the aqueous solution is 40° C., and is controlled within ±0.5.

[0220] The contents of the reaction tank are stirred and mixed appropriately.

[0221] The reaction tank used in the continuous coprecipitation method may be a type of reaction tank that overflows in order to separate the formed reaction precipitate.

[0222] The reaction tank may also be in an inert atmosphere. If the reaction tank is in an inert atmosphere, metals in the mixed solution that are more easily oxidized than nickel will be less likely to aggregate before nickel. Therefore, a uniform metal composite hydroxide can be easily obtained.

[0223] Furthermore, the reaction tank may be provided with a moderate oxidizing atmosphere. The oxidizing atmosphere may be an oxygen-containing atmosphere obtained by mixing an oxidizing gas with an inert gas, or an oxidizing agent may be present in the inert gas atmosphere. By providing a moderate oxidizing atmosphere in the reaction tank, the transition metal contained in the mixed solution is moderately oxidized, making it easier to control the morphology of the metal composite oxide.

[0224] The oxygen or oxidizing agent in the oxidizing atmosphere may be present in sufficient amounts of oxygen atoms to oxidize the transition metal.

[0225] When the oxidizing atmosphere is an oxygen-containing atmosphere, the atmosphere in the reaction vessel can be controlled by, for example, aerating the reaction vessel with an oxidizing gas or bubbling the oxidizing gas through the mixed solution.

[0226] After the above reaction, the obtained reaction precipitate is washed and then dried to obtain a metal composite hydroxide as a precursor.

[0227] In addition, when impurities derived from the mixed solution remain in the reaction precipitate when washed with water alone, the reaction precipitate may be washed with weak acid water or an alkaline solution as needed. Examples of the alkaline solution include aqueous solutions containing sodium hydroxide and potassium hydroxide.

[0228] After the above reaction, the obtained reaction precipitate is washed and then dried to obtain a metal composite hydroxide as a nickel-cobalt-manganese composite compound.

[0229] In addition, when impurities derived from the mixed solution remain in the reaction precipitate when washed with water alone, the reaction precipitate may be washed with weak acid water or an alkaline solution as needed. Examples of the alkaline solution include aqueous solutions containing sodium hydroxide and potassium hydroxide.

[0230] It should be noted that, in the above examples, metal composite hydroxides were produced, but metal composite oxides can also be produced. For example, metal composite oxides can be produced by oxidizing metal composite hydroxides.

[0231] The drying time, from the start of heating to the end of temperature holding, is preferably set to a total time of 1 hour or more and 30 hours or less. The heating rate in the heating step to reach 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.

[0232] The maximum holding temperature in this specification refers to the maximum holding temperature of the atmosphere in the firing furnace during the firing process, and is the firing temperature during the firing process. In the case of this firing process having multiple heating steps, the maximum holding temperature refers to the highest temperature in each heating step.

[0233] The temperature increase rate in this specification is calculated from the time from the start of temperature increase to the maximum holding temperature in the firing device and the temperature difference from the temperature at the start of temperature increase to the maximum holding temperature in the firing furnace of the firing device.

[0234] As a method for isolating the precursor from the reaction precipitate, a method of dehydrating the slurry containing the reaction precipitate (coprecipitate slurry) by centrifugation, suction filtration, or the like is preferably used.

[0235] The coprecipitate obtained after the dehydration is preferably washed with water or an alkaline washing solution. In this embodiment, washing with an alkaline washing solution is preferred, and washing with a sodium hydroxide solution is more preferred. Alternatively, washing with a washing solution containing elemental sulfur may be used. Examples of such washing solutions containing elemental sulfur include aqueous solutions of potassium and sodium sulfates.

[0236] [(2) Mixing step of mixing the above-mentioned precursor with a lithium compound to obtain a mixture]

[0237] This step is a step of mixing a lithium compound and a precursor to obtain a mixture.

[0238] Lithium compounds

[0239] As the lithium compound, any one of lithium carbonate, lithium nitrate, lithium acetate, lithium hydroxide, lithium oxide, lithium chloride, and lithium fluoride can be used, or a mixture of two or more thereof can be used. Among these, any one or both of lithium hydroxide and lithium carbonate are preferred.

[0240] Furthermore, when lithium hydroxide contains lithium carbonate as an impurity, the content of lithium carbonate in the lithium hydroxide is preferably 5% by mass or less.

[0241] The method of mixing the precursor and the lithium compound will be described.

[0242] After the precursor is dried, it is mixed with the lithium compound. Drying conditions are not particularly limited, and examples thereof include any one of the following drying conditions 1) to 3).

[0243] 1) Conditions under which the precursor is not oxidized or reduced. Specifically, dry conditions under which an oxide remains an oxide, or dry conditions under which a hydroxide remains a hydroxide.

[0244] 2) The conditions under which the precursor is oxidized. Specifically, the dry conditions under which the hydroxide is oxidized to the oxide.

[0245] 3) Precursor reduction conditions: Specifically, the dry conditions for reduction from oxide to hydroxide.

[0246] Drying conditions 1) to 3) may be appropriately selected depending on whether the nickel-containing MCC to be produced is a nickel-containing metal composite hydroxide or a nickel-containing metal composite oxide.

[0247] To prevent oxidation or reduction, an inert gas such as nitrogen, helium, or argon may be used as the drying atmosphere. Oxygen or air may be used to oxidize the hydroxide.

[0248] Furthermore, as a condition for reducing the precursor, a reducing agent such as hydrazine or sodium sulfite may be used in an inert gas atmosphere.

[0249] After the precursor is dried, it can also be appropriately classified.

[0250] The above lithium compound and precursor are mixed in consideration of the composition ratio of the final target product. For example, when using nickel-cobalt-manganese metal composite hydroxide, the lithium compound and nickel-cobalt-manganese metal composite hydroxide are mixed in an amount of Li[Li r (Ni (1-y-z) Co y Mn z ) 1-r ]O2 (wherein, y+z=1) are mixed in a proportion corresponding to the composition ratio.

[0251] The mixture of the nickel-cobalt-manganese metal composite hydroxide and the lithium compound is calcined in the subsequent calcination step to obtain a lithium-nickel-cobalt-manganese metal composite oxide.

[0252] From the perspective of obtaining a uniform lithium-nickel-cobalt-manganese metal composite oxide, r is preferably greater than 0, more preferably 0.01 or greater, and even more preferably 0.02 or greater. Furthermore, from the perspective of obtaining a highly pure lithium-nickel-cobalt-manganese metal composite oxide, r is preferably 0.1 or less, more preferably 0.08 or less, and even more preferably 0.06 or less.

[0253] The upper limit value and the lower limit value of r described above can be arbitrarily combined.

[0254] [Step of calcining the mixture (3) to obtain LiMO]

[0255] The mixture of the lithium compound and the precursor is calcined.

[0256] The mixture of the lithium compound and the precursor is preferably fired in the presence of an inert flux.

[0257] By calcining the mixture in the presence of an inactive flux, the reaction of the mixture can be accelerated. The inactive flux may remain in the burned product after calcination, or it may be removed by washing the burned product with a cleaning solution. The burned product after calcination is preferably washed with pure water, an alkaline cleaning solution, or the like.

[0258] Generally, the higher the holding temperature, the larger the particle size tends to be. The holding temperature during calcination can be appropriately adjusted depending on the type of transition metal element, precipitant, and inert flux used, and their amount.

[0259] The calcination temperature may be set in consideration of the melting point of the inert flux described below, and is preferably set within a range of -200°C to +200°C, the melting point of the inert flux.

[0260] Specifically, the firing temperature is in the range of 200° C. to 1150° C., preferably 300° C. to 1050° C., and more preferably 500° C. to 1000° C.

[0261] The holding time during calcination may be appropriately adjusted according to the type of transition metal element, precipitant, and type and amount of inert flux used.

[0262] When the calcination temperature is at least the lower limit, LiMO having a strong crystal structure can be obtained. Furthermore, when the calcination temperature is at most the upper limit, lithium volatilization can be reduced.

[0263] The firing temperature in this specification refers to the temperature of the atmosphere in the firing furnace, and is the highest temperature of the holding temperature in the firing process (hereinafter sometimes referred to as the maximum holding temperature). In the case of a firing process with multiple heating processes, it refers to the temperature when heating at the highest holding temperature in each heating process.

[0264] Specifically, the time of holding at the above-mentioned calcination 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 to the above-mentioned calcination temperature is usually 50°C / hour or more and 400°C / hour or less, and the cooling rate from the above-mentioned calcination temperature to room temperature is usually 10°C / hour or more and 400°C / hour or less. In addition, as the calcination atmosphere, air, oxygen, nitrogen, argon or a mixture thereof can be used.

[0265] The temperature increase rate in the heating step to reach the maximum holding temperature is preferably 180° C. / hour or higher, more preferably 200° C. / hour or higher, and particularly preferably 250° C. / hour or higher.

[0266] The temperature increase rate in the heating step to reach the maximum holding temperature is calculated from the time from the start of temperature increase in the sintering apparatus to the time when the temperature reaches the holding temperature described later.

[0267] The inactive flux is not particularly limited as long as it is difficult to react with the mixture during firing. Examples thereof include fluorides of one or more elements (hereinafter referred to as "A") selected from the group consisting of Na, K, Rb, Cs, Ca, Mg, Sr, and Ba, chlorides of A, carbonates of A, sulfates of A, nitrates of A, phosphates of A, hydroxides of A, molybdates of A, and tungstates of A.

[0268] As fluorides of A, there can be listed NaF (melting point: 993°C), KF (melting point: 858°C), RbF (melting point: 795°C), CsF (melting point: 682°C), CaF2 (melting point: 1402°C), MgF2 (melting point: 1263°C), SrF2 (melting point: 1473°C) and BaF2 (melting point: 1355°C).

[0269] As chlorides of A, there can be listed NaCl (melting point: 801°C), KCl (melting point: 770°C), RbCl (melting point: 718°C), CsCl (melting point: 645°C), CaCl2 (melting point: 782°C), MgCl2 (melting point: 714°C), SrCl2 (melting point: 857°C) and BaCl2 (melting point: 963°C).

[0270] As carbonates of A, there can be listed Na2CO3 (melting point: 854°C), K2CO3 (melting point: 899°C), Rb2CO3 (melting point: 837°C), Cs2CO3 (melting point: 793°C), CaCO3 (melting point: 825°C), MgCO3 (melting point: 990°C), SrCO3 (melting point: 1497°C) and BaCO3 (melting point: 1380°C).

[0271] As sulfates of A, there are Na2SO4 (melting point: 884°C), K2SO4 (melting point: 1069°C), Rb2SO4 (melting point: 1066°C), Cs2SO4 (melting point: 1005°C), CaSO4 (melting point: 1460°C), MgSO4 (melting point: 1137°C), SrSO4 (melting point: 1605°C) and BaSO4 (melting point: 1580°C).

[0272] As nitrates of A, there are NaNO3 (melting point: 310°C), KNO3 (melting point: 337°C), RbNO3 (melting point: 316°C), CsNO3 (melting point: 417°C), Ca(NO3)2 (melting point: 561°C), Mg(NO3)2, Sr(NO3)2 (melting point: 645°C) and Ba(NO3)2 (melting point: 596°C).

[0273] As phosphates of A, there can be listed Na3PO4, K3PO4 (melting point: 1340°C), Rb3PO4, Cs3PO4, Ca3(PO4)2, Mg3(PO4)2 (melting point: 1184°C), Sr3(PO4)2 (melting point: 1727°C) and Ba3(PO4)2 (melting point: 1767°C).

[0274] As hydroxides of A, there can be listed NaOH (melting point: 318°C), KOH (melting point: 360°C), RbOH (melting point: 301°C), CsOH (melting point: 272°C), Ca(OH)2 (melting point: 408°C), Mg(OH)2 (melting point: 350°C), Sr(OH)2 (melting point: 375°C) and Ba(OH)2 (melting point: 853°C).

[0275] As molybdates of A, there are Na2MoO4 (melting point: 698°C), K2MoO4 (melting point: 919°C), Rb2MoO4 (melting point: 958°C), Cs2MoO4 (melting point: 956°C), CaMoO4 (melting point: 1520°C), MgMoO4 (melting point: 1060°C), SrMoO4 ​​(melting point: 1040°C) and BaMoO4 (melting point: 1460°C).

[0276] Examples of the tungstate of A include Na2WO4 (melting point: 687°C), K2WO4, Rb2WO4, Cs2WO4, CaWO4, MgWO4, SrWO4, and BaWO4.

[0277] Two or more of these inactive fluxes may also be used. When two or more are used, the melting point may also be lowered. Furthermore, among these inactive fluxes, as an inactive flux for obtaining LiMO with higher crystallinity, preferably any one of A's carbonates, A's sulfates, and A's chlorides, or a combination thereof. Furthermore, A is preferably any one or both of sodium (Na) and potassium (K). Specifically, among the above, particularly preferred inactive fluxes are one or more selected from the group consisting of NaOH, KOH, NaCl, KCl, Na2CO3, K2CO3, Na2SO4, and K2SO4.

[0278] As the inactive flux, potassium sulfate or sodium sulfate is preferred.

[0279] The fired product obtained after firing is preferably washed with pure water or an alkaline cleaning solution. The washing step can remove the inactive flux.

[0280] As the alkaline cleaning solution, for example, one or more anhydrous substances selected from the group consisting of LiOH (lithium hydroxide), Li2CO3 (lithium carbonate), and (NH4)2CO3 (ammonium carbonate) and aqueous solutions of their hydrates can be cited. In addition, ammonia can also be used as the base.

[0281] The temperature of the washing liquid used in washing is preferably 15° C. or lower, more preferably 10° C. or lower, and even more preferably 8° C. or lower. By controlling the temperature of the washing liquid to the above range without freezing, excessive dissolution of lithium ions from the crystal structure of the burned product into the washing liquid during washing can be suppressed.

[0282] In the washing step, as a method of bringing the washing liquid into contact with the burned product, the following methods can be mentioned.

[0283] 1) A method in which the burned material is added to the washing liquid and stirred.

[0284] 2) A method in which the washing liquid is set as spray water and applied to the burned material.

[0285] 3) A method in which the burned material is added to the washing liquid and stirred, and then the burned material is separated from the aqueous solution of each washing liquid. Subsequently, the washing liquid is set as spray water and applied to the separated burned material.

[0286] After washing, dehydration treatment is preferably performed to obtain a wet cake containing 15% by weight or more of water. As an example of the upper limit of the water content of the wet cake, it is preferably 30% by weight or less.

[0287] [Heat treatment process]

[0288] In this embodiment, the obtained wet cake is preferably subjected to heat treatment. If heat treatment is performed, the above-mentioned (1), (2) and other physical properties can be controlled within the range of this embodiment.

[0289] The total time for the heat treatment, from the start of heating to the end of temperature holding, is preferably set to 1 hour or more and 10 hours or less. The heating rate in the heating step to reach the maximum holding temperature is preferably 100°C / hour or more, more preferably 150°C / hour or more, and particularly preferably 200°C / hour or more.

[0290] The heat treatment temperature is preferably 500°C or higher, more preferably 600°C or higher, and particularly preferably 700°C or higher. It is preferably 900°C or lower, more preferably 850°C or lower, and particularly preferably 800°C or lower.

[0291] In the heat treatment step, the wet cake is preferably filled in a ceramic container and placed in a static state in a batch or continuous heating furnace for heat treatment. Alternatively, a rotary kiln can be used as the heating equipment, and the wet cake can be heat treated in a fluidized state within the furnace core tube.

[0292] As the atmospheric gas in contact with the wet cake during the heat treatment step, an oxidizing gas is preferably supplied. Air or oxygen can be used as the oxidizing gas. When air is used, the carbon dioxide concentration is preferably removed to less than 100 ppm.

[0293] By heat-treating a wet cake containing 15% or more water, the hot water partially dissolves the LiMO until the water is completely dried. This facilitates the disintegration of aggregation between primary particles, and the proportion of micropores smaller than 200 nm, as measured by gas adsorption, tends to decrease.

[0294] By performing the heat treatment under the above-described conditions after the washing step, the specific surface area of ​​LiMO and the physical property values ​​determined from nitrogen adsorption isotherm measurement by a gas adsorption method can be controlled within the ranges of the present embodiment.

[0295] Crushing process

[0296] After calcination, the obtained LiMO can also be crushed.

[0297] The crushing step is preferably carried out using an airflow mill, a collision mill with a classifying mechanism, a pin mill, a ball mill, a jet mill, a reverse jet mill with a classifying rotor, or the like.

[0298] <cam>

[0299] The CAM of this embodiment contains LiMO of this embodiment. In the CAM of this embodiment, the content of LiMO relative to the total mass of the CAM (100 mass%) is preferably 70 to 99 mass%, more preferably 80 to 98 mass%.

[0300] In this embodiment, the content ratio of LiMO relative to the total mass of the CAM is determined by irradiating the CAM with electron beams at an accelerating voltage of 20 kV using a SEM (e.g., JSM-5510 manufactured by JEOL Ltd.). The magnification of the SEM photograph is adjusted so that 200 to 400 particles of the target CAM are present in the SEM photograph. As an example, the magnification may be 1,000 to 30,000 times.

[0301] <Lithium Secondary Battery>

[0302] Next, the configuration of a lithium secondary battery will be described, and a positive electrode using CAM using LiMO of this embodiment as a positive electrode active material of the lithium secondary battery and a lithium secondary battery having the positive electrode will be described.

[0303] CAM preferably contains the above-mentioned LiMO, but may contain other components within a range that does not impair the effects of the present invention.

[0304] An example of a lithium secondary battery includes a positive electrode and a negative electrode, a separator sandwiched between the positive electrode and the negative electrode, and an electrolyte solution disposed between the positive electrode and the negative electrode.

[0305] Figure 1A 、 Figure 1B Schematic diagram showing an example of a lithium secondary battery according to the present embodiment. A cylindrical lithium secondary battery 10 according to the present embodiment is manufactured as follows.

[0306] First, if Figure 1A As shown in the figure, an electrode group 4 is made by stacking and winding a pair of strip-shaped separators 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 separator 1, positive electrode 2, separator 1, and negative electrode 3.

[0307] Then, if Figure 1B As shown in FIG, after the electrode group 4 and an insulator (not shown) are housed in a battery can 5, the bottom of the can is sealed, and an electrolyte 6 is impregnated into the electrode group 4, and the electrolyte is disposed between the positive electrode 2 and the negative electrode 3. Furthermore, the upper portion of the battery can 5 is sealed with a top insulator 7 and a sealing member 8, thereby manufacturing a lithium secondary battery 10.

[0308] Examples of the shape of the electrode group 4 include a columnar shape such as a circle, an ellipse, a rectangle, or a rectangle with rounded corners, in which the cross-sectional shape when the electrode group 4 is cut in a direction perpendicular to the winding axis is a circle, an ellipse, a rectangle, or a rectangle with rounded corners.

[0309] The shape of the lithium secondary battery having the electrode group 4 may be a shape specified in IEC60086 or JISC8500, which are battery standards specified by the International Electrotechnical Commission (IEC). Examples of such shapes include cylindrical and rectangular shapes.

[0310] Furthermore, lithium secondary batteries are not limited to the aforementioned wound-type configurations, but may also be stacked structures in which a positive electrode, a separator, a negative electrode, and a separator are repeatedly stacked. Examples of stacked lithium secondary batteries include coin-type batteries, button-type batteries, and paper-type (or sheet-type) batteries.

[0311] Hereinafter, each configuration will be described in sequence.

[0312] (positive electrode)

[0313] The positive electrode can be manufactured by first preparing a positive electrode mixture containing a positive electrode active material, a conductive material, and a binder, and then supporting the positive electrode mixture on a positive electrode current collector.

[0314] (Conductive material)

[0315] As the conductive material possessed by the positive electrode, a carbon material can be used. As the carbon material, graphite powder, carbon black (such as acetylene black), fibrous carbon materials, etc. can be listed. Since carbon black is a particulate and has a large surface area, by adding a small amount to the positive electrode mixture, the conductivity inside the positive electrode can be improved, and the charge and discharge efficiency and output characteristics can be improved. However, if too much is added, the bonding force between the positive electrode mixture and the positive electrode collector brought by the binder and the bonding force inside the positive electrode mixture are reduced, which instead becomes the reason for increasing the internal resistance.

[0316] The proportion of the conductive material in the positive electrode mixture is preferably 5 parts by mass or more and 20 parts by mass or less per 100 parts by mass of CAM. This proportion can also be reduced when using fibrous carbon materials such as graphitized carbon fibers and carbon nanotubes as the conductive material.

[0317] (Adhesive)

[0318] As the binder of the positive electrode, a thermoplastic resin can be used. Examples of the thermoplastic resin include polyimide resins; fluororesins 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.

[0319] These thermoplastic resins may be mixed and used in combination of two or more. By using a fluororesin and a polyolefin resin as binders, setting the ratio of the fluororesin to the total positive electrode mixture to 1% by mass or more and 10% by mass or less, and setting the ratio of the polyolefin resin to 0.1% by mass or more and 2% by mass or less, a positive electrode mixture having high adhesion to the positive electrode current collector and high internal bonding strength can be obtained.

[0320] (Positive electrode current collector)

[0321] As the positive electrode current collector of the positive electrode, a strip-shaped member formed of a metal material such as Al, Ni, or stainless steel can be used. Among them, a member formed of Al in a thin film shape is preferred due to its ease of processing and low cost.

[0322] As a method for supporting the positive electrode mixture on the positive electrode current collector, a method of press-molding the positive electrode mixture on the positive electrode current collector can be cited. Alternatively, the positive electrode mixture can be paste-formed using an organic solvent, the resulting paste of the positive electrode mixture can be applied to at least one side of the positive electrode current collector, dried, pressed, and bonded, thereby supporting the positive electrode mixture on the positive electrode current collector.

[0323] When the positive electrode mixture is formed into a paste, 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).

[0324] Examples of a method for applying the positive electrode mixture paste onto the positive electrode current collector include slot die coating, screen coating, curtain coating, doctor blade coating, gravure coating, and electrostatic spraying.

[0325] The positive electrode can be manufactured by the methods listed above.

[0326] (negative electrode)

[0327] The negative electrode of a lithium secondary battery can be doped and dedoped with lithium ions at a lower potential than the positive electrode. Examples include an electrode in which a negative electrode mixture containing a negative electrode active material is supported on a negative electrode current collector and an electrode composed solely of a negative electrode active material.

[0328] (Negative electrode active material)

[0329] Examples of the negative electrode active material of the negative electrode include carbon materials, chalcogenides (oxides, sulfides, etc.), nitrides, metals, or alloys, and materials capable of being doped and dedoped with lithium ions at a lower potential than the positive electrode.

[0330] Examples of carbon materials that can be used as the negative electrode active material include graphites such as natural graphite and artificial graphite, cokes, carbon black, pyrolytic carbons, carbon fibers, and calcined organic polymer compounds.

[0331] Examples of oxides that can be used as negative electrode active materials include SiO2, SiO2, and SiO2. x (where x is a positive real number) represented by silicon oxide; SnO2, SnO, etc. x (where x is a positive real number) tin oxide represented by Li4Ti5O 12 and other composite metal oxides containing lithium and titanium.

[0332] Examples of metals that can be used as the negative electrode active material include lithium metal, silicon metal, and tin metal.

[0333] As materials that can be used as negative electrode active materials, materials described in WO2019 / 098384A1 or US2020 / 0274158A1 can also be used.

[0334] These metals and alloys are processed into foils, for example, and are mainly used alone as electrodes.

[0335] Among the above-mentioned negative electrode active materials, it is preferred to use a carbon material having graphite such as natural graphite or artificial graphite as a main component, for reasons such as that the potential of the negative electrode does not substantially change from the uncharged state to the fully charged state during charging (potential flatness is good), the average discharge potential is low, and the capacity retention rate during repeated charge and discharge is high (cycle characteristics are good). As the shape of the carbon material, for example, it can be any one of a flake such as natural graphite, a spherical shape such as mesophase carbon microspheres, a fibrous shape such as graphitized carbon fiber, or an agglomerate of fine powder.

[0336] The negative electrode mixture may contain a binder as needed. Examples of the binder 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.

[0337] (Negative electrode current collector)

[0338] Examples of the negative electrode current collector of the negative electrode include strip-shaped members formed of metal materials such as Cu, Ni, and stainless steel. Among them, members formed of Cu in a thin film are preferred because they are difficult to alloy with lithium and are easy to process.

[0339] Examples of methods for supporting the negative electrode mixture on the negative electrode current collector include, similarly to the positive electrode, a method of using a press molding method, and a method of forming a paste using a solvent or the like, applying the paste to the negative electrode current collector, drying the paste, and then pressing and bonding the paste.

[0340] (diaphragm)

[0341] As the separator possessed by the lithium secondary battery, for example, a material having a form such as a porous film, a nonwoven fabric, or a woven fabric formed from a polyolefin resin such as polyethylene or polypropylene, a fluororesin, or a nitrogen-containing aromatic polymer can be used. In addition, a separator can be formed by using two or more of these materials, or by stacking these materials to form a separator. In addition, the separators described in JP-A-2000-030686 and US20090111025A1 can also be used.

[0342] In order to allow the electrolyte to permeate well during battery use (charge and discharge), the separator has an air permeability resistance (air permeability resistance) as determined by the Gurley method specified in JIS P 8117 of preferably 50 sec / 100 cc or more and 300 sec / 100 cc or less, more preferably 50 sec / 100 cc or more and 200 sec / 100 cc or less.

[0343] The porosity of the separator is preferably 30% by volume or more and 80% by volume or less, and more preferably 40% by volume or more and 70% by volume or less. The separator may be a laminate of separators having different porosities.

[0344] (Electrolyte)

[0345] The electrolyte solution of a lithium secondary battery contains an electrolyte and an organic solvent.

[0346] As the electrolyte contained in the electrolyte, lithium salts such as LiClO4, LiPF6, and LiBF4 can be listed, and a mixture of two or more of these can also be used. In addition, the electrolyte described in WO2019 / 098384A1 or US2020 / 0274158A1 can also be used. Among them, as the electrolyte, it is preferred to use a substance comprising at least one selected from the group consisting of LiPF6, LiAsF6, LiSbF6, LiBF4, LiCF3SO3, LiN(SO2CF3)2 and LiC(SO2CF3)3 containing fluorine.

[0347] In addition, as the organic solvent contained in the electrolyte solution, for example, propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, or an organic solvent described in WO2019 / 098384A1 or US2020 / 0274158A1 can be used.

[0348] As an organic solvent, it is preferred to use a mixture of two or more thereof. Among them, a mixed solvent containing carbonates is preferred, and a mixed solvent of cyclic carbonates and non-cyclic carbonates and a mixed solvent of cyclic carbonates and ethers are more preferred. As a mixed solvent of cyclic carbonates and non-cyclic carbonates, a mixed solvent containing ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate is preferred. The electrolyte using such a mixed solvent has the following many advantages: a wide operating temperature range; it is not easy to degrade even when charging and discharging at a high current rate; it is not easy to degrade even when used for a long time; and it is difficult to decompose even when a graphite material such as natural graphite or artificial graphite is used as the active material of the negative electrode.

[0349] Furthermore, as an electrolyte, an electrolyte containing a fluorine-containing lithium salt such as LiPF6 and an organic solvent having a fluorine substituent is preferably used, as this improves the safety of the resulting lithium secondary battery. A mixed solvent containing an ether having a fluorine substituent such as pentafluoropropyl methyl ether or 2,2,3,3-tetrafluoropropyldifluoromethyl ether and dimethyl carbonate is further preferred, as it exhibits a high capacity retention rate even during charge and discharge at high current rates.

[0350] Since the CAM having the above-described structure uses the LiMO of the present embodiment, the rate characteristics and cycle characteristics of the lithium secondary battery using the CAM can be improved.

[0351] Furthermore, since the positive electrode having the above-described structure includes the CAM having the above-described structure, the rate characteristics and cycle characteristics of the lithium secondary battery can be improved.

[0352] Furthermore, the lithium secondary battery having the above-described structure has the above-described positive electrode, and therefore has high rate characteristics and cycle characteristics.

[0353] <All-solid-state lithium-ion battery>

[0354] LiMO of this embodiment can also be used as a positive electrode active material for all-solid-state lithium-ion batteries.

[0355] The structure of the all-solid-state lithium-ion battery will be described, and the LiMO of this embodiment will be used as the positive electrode of the CAM of the all-solid-state lithium-ion battery and the all-solid-state lithium-ion battery having the positive electrode will be described. The all-solid-state lithium-ion battery of this embodiment is a secondary battery.

[0356] Figure 4 、 5 Schematic diagram showing an example of an all-solid-state lithium-ion battery according to this embodiment. Figure 4 Schematic diagram showing a stacked body included in the all-solid-state lithium-ion battery of this embodiment. Figure 5 Schematic diagram showing the overall structure of the all-solid-state lithium-ion battery of this embodiment.

[0357] The all-solid-state secondary battery 1000 includes a stack 100 having a positive electrode 110, a negative electrode 120, and a solid electrolyte layer 130, and an outer casing 200 for housing the stack 100. Alternatively, the all-solid-state lithium secondary battery 1000 may have a bipolar structure in which a positive electrode active material and a negative electrode active material are disposed on either side of a current collector. Specific examples of bipolar structures include those described in JP-A-2004-95400. The materials used to construct each component are described below.

[0358] The laminate 100 may also include an external terminal 113 connected to the positive electrode current collector 112 and an external terminal 123 connected to the negative electrode current collector 122 .

[0359] In the stack 100, the positive electrode 110 and the negative electrode 120 sandwich the solid electrolyte layer 130 so as not to short-circuit each other. Alternatively, the all-solid-state lithium-ion battery 1000 may include a separator, such as that used in conventional liquid-based lithium-ion secondary batteries, between the positive electrode 110 and the negative electrode 120 to prevent short-circuiting between the positive electrode 110 and the negative electrode 120.

[0360] The all-solid-state lithium-ion battery 1000 includes an insulator (not shown) that insulates the stacked body 100 from the outer casing 200 , and a sealing body (not shown) that seals the opening 200 a of the outer casing 200 .

[0361] The outer package 200 may be formed from a highly corrosion-resistant metal material such as aluminum, stainless steel, or nickel-plated steel. Alternatively, a container formed from a laminate film having at least one surface subjected to corrosion-resistant treatment and formed into a bag may be used.

[0362] Examples of the shape of the all-solid-state lithium-ion battery 1000 include a coin shape, a button shape, a paper shape (or a sheet shape), a cylindrical shape, and a square shape.

[0363] Although all-solid-state lithium-ion battery 1000 is shown as having a single stack 100 , the present invention is not limited thereto. All-solid-state lithium-ion battery 1000 may also be configured such that stack 100 serves as a unit cell and a plurality of unit cells (stacks 100 ) are enclosed within an outer casing 200 .

[0364] Hereinafter, each configuration will be described in sequence.

[0365] (positive electrode)

[0366] The positive electrode 110 includes a positive electrode active material layer 111 and a positive electrode current collector 112 .

[0367] The positive electrode active material layer 111 includes the positive electrode active material including the above-mentioned LiMO. Alternatively, the positive electrode active material layer 111 may include a solid electrolyte (second solid electrolyte), a conductive material, and a binder.

[0368] The positive electrode active material 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 includes a plurality of particles (positive electrode active material) containing LiMO crystals, and a solid electrolyte that is filled between the plurality of particles (positive electrode active material) and is in contact with the particles (positive electrode active material).

[0369] (Solid Electrolyte)

[0370] As the solid electrolyte that can be included in the positive electrode active material layer 111, a solid electrolyte having lithium ion conductivity and used in known all-solid-state batteries can be used. 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.

[0371] Examples of organic electrolytes include polymer solid electrolytes. Examples of the respective electrolytes include compounds described in WO2020 / 208872A1, US2016 / 0233510A1, US2012 / 0251871A1, and US2018 / 0159169A1. Examples include the following compounds.

[0372] In the present embodiment, an oxide-based solid electrolyte or a sulfide-based solid electrolyte is preferably used, and an oxide-based solid electrolyte is more preferably used.

[0373] (Oxide-based solid electrolyte)

[0374] Examples of oxide-based solid electrolytes include perovskite oxides, NASICON oxides, LISICON oxides, and garnet oxides. Specific examples of each oxide include compounds described in WO2020 / 208872A1, US2016 / 0233510A1, and US2020 / 0259213A1.

[0375] Examples of garnet-type oxides include Li7La3Zr2O 12 (LLZ) and other Li-La-Zr oxides.

[0376] The oxide-based solid electrolyte may be a crystalline material or an amorphous (amorphous) material. Examples of amorphous (amorphous) solid electrolytes include Li-BO compounds such as Li3BO3, Li2B4O7, and LiBO2. The oxide-based solid electrolyte preferably comprises an amorphous material.

[0377] (Sulfide-based solid electrolyte)

[0378] As sulfide-based solid electrolytes, there are Li2S-P2S5 compounds, Li2S-SiS2 compounds, Li2S-GeS2 compounds, Li2S-B2S3 compounds, LiI-Si2S-P2S5 compounds, LiI-Li2S-P2O5, LiI-Li3PO4-P2S5 compounds, Li 10 GeP2S 12 wait.

[0379] It should be noted that in this specification, the term "sulfide-based compound" is used as a general term for solid electrolytes primarily containing raw materials such as "Li2S" and "P2S5" as described above. For example, Li2S-P2S5-based compounds include solid electrolytes containing Li2S and P2S5 and further containing other raw materials. Furthermore, Li2S-P2S5-based compounds also include solid electrolytes with varying mixing ratios of Li2S and P2S5.

[0380] Examples of Li2S-P2S5 compounds include Li2S-P2S5, Li2S-P2S5-LiI, Li2S-P2S5-LiCl, Li2S-P2S5-LiBr, and Li2S-P2S5-LiI-LiBr.

[0381] As Li2S-SiS2 series compounds, there can be listed Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-SiS2-P2S5-LiCl, etc.

[0382] Examples of Li2S-GeS2 compounds include Li2S-GeS2, Li2S-GeS2-P2S5, and the like.

[0383] The sulfide-based solid electrolyte may be a crystalline material or an amorphous (amorphous) material. The sulfide-based solid electrolyte preferably includes an amorphous material.

[0384] Two or more solid electrolytes may be used in combination within a range not impairing the effects of the invention.

[0385] (Conductive materials and adhesives)

[0386] The conductive material that can be included in the positive electrode active material layer 111 can be the materials described in the above-mentioned "Conductive Material". The proportion of the conductive material in the positive electrode mixture can also be similarly applied to the proportion described in the above-mentioned "Conductive Material". Furthermore, the binder included in the positive electrode can be the materials described in the above-mentioned "Binder".

[0387] (Positive electrode current collector)

[0388] As the positive electrode current collector 112 included in the positive electrode 110 , the material described in the above-mentioned (Positive Electrode Current Collector) can be used.

[0389] As a method for supporting the positive electrode active material layer 111 on the positive electrode current collector 112, there is a method of press-molding the positive electrode active material layer 111 on the positive electrode current collector 112. For press-molding, cold pressing or hot pressing can be used.

[0390] In addition, a positive electrode mixture can be prepared by using an organic solvent to paste a mixture of a positive electrode active material, a solid electrolyte, a conductive material, and a binder, and the obtained positive electrode mixture is applied to at least one side of the positive electrode collector 112 and dried, pressed, and bonded, thereby supporting the positive electrode active material layer 111 on the positive electrode collector 112.

[0391] Alternatively, a positive electrode mixture may be prepared by using an organic solvent to form a paste of a mixture of a positive electrode active material, a solid electrolyte, and a conductive material, and the obtained positive electrode mixture may be applied to at least one side of the positive electrode collector 112 and dried and sintered, thereby supporting the positive electrode active material layer 111 on the positive electrode collector 112 .

[0392] As the organic solvent that can be used in the positive electrode mixture, the same organic solvents as those that can be used when the positive electrode mixture is formed into a paste as described in the above-mentioned (Positive Electrode Collector) can be used.

[0393] Examples of a method for applying the positive electrode mixture onto the positive electrode current collector 112 include a slot die coating method, a screen coating method, a curtain coating method, a doctor blade coating method, a gravure coating method, and an electrostatic spray method.

[0394] The positive electrode 110 can be manufactured by the above-listed methods.

[0395] (negative electrode)

[0396] The negative electrode 120 includes 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. Alternatively, the negative electrode active material layer 121 may contain a solid electrolyte and a conductive material. The negative electrode active material, negative electrode current collector, solid electrolyte, conductive material, and binder described above can be used.

[0397] (Solid electrolyte layer)

[0398] The solid electrolyte layer 130 includes the aforementioned solid electrolyte (first solid electrolyte). When the positive electrode active material layer 111 includes a solid electrolyte, the solid electrolyte (first solid electrolyte) constituting the solid electrolyte layer 130 and the solid electrolyte (second solid electrolyte) contained in the positive electrode active material layer 111 may be the same substance. The solid electrolyte layer 130 functions as a medium for conducting lithium ions and also as a separator that separates the positive electrode 110 and the negative electrode 120 to prevent short circuits.

[0399] 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.

[0400] Alternatively, the solid electrolyte layer 130 may be formed by applying a paste-like mixture containing a solid electrolyte to the surface of the positive electrode active material layer 111 of the positive electrode 110 and drying the mixture. Alternatively, the solid electrolyte layer 130 may be formed by press molding after drying and further pressing the mixture by cold isostatic pressing (CIP).

[0401] Furthermore, the solid electrolyte layer 130 can be formed by pre-forming a solid electrolyte into particles, stacking the solid electrolyte particles on the above-mentioned positive electrode active material sheet, and uniaxially pressing them in the stacking direction. The positive electrode active material sheet becomes the positive electrode active material layer 111 .

[0402] The positive electrode current collector 112 is further placed on the obtained stack of the positive electrode active material layer 111 and the solid electrolyte layer 130. The solid electrolyte layer 130 and the positive electrode 110 are formed by uniaxial pressing in the stacking direction and sintering.

[0403] Such positive electrode 110 is in contact with solid electrolyte layer 130. Solid electrolyte layer 130 includes a first solid electrolyte.

[0404] The positive electrode 110 includes a positive electrode active material layer 111 in contact with a solid electrolyte layer 130, and a positive electrode current collector 112 on which the positive electrode active material layer 111 is stacked. The positive electrode active material layer 111 includes a plurality of particles containing LiMO crystals (i.e., CAM as one embodiment of the present invention) and a solid electrolyte (second solid electrolyte) filled between the particles and in contact with the particles.

[0405] The solid electrolyte and particles contained in the positive electrode active material layer 111 are in contact with the solid electrolyte layer 130 . That is, the particles contained in the positive electrode active material layer 111 are in contact with the solid electrolyte contained in the positive electrode active material layer 111 and the solid electrolyte layer 130 .

[0406] It should be noted that all of the particles (positive electrode active material) contained in the positive electrode active material layer 111 do not necessarily need to be in contact with the solid electrolyte contained in the positive electrode active material layer 111 and the solid electrolyte layer 130 .

[0407] The positive electrode active material contained in the positive electrode active material layer 111 is in contact with the solid electrolyte contained in the positive electrode active material layer 111, thereby conducting electricity with the solid electrolyte contained in the positive electrode active material layer 111. Furthermore, the positive electrode active material contained in the positive electrode active material layer 111 is in contact with the solid electrolyte layer 130, thereby conducting electricity with the solid electrolyte layer 130. Furthermore, the solid electrolyte contained in the positive electrode active material layer 111 is in contact with the solid electrolyte layer 130, thereby conducting electricity with the solid electrolyte layer 130.

[0408] Through these, the positive electrode active material contained in the positive electrode active material layer 111 is directly or indirectly electrically connected to the solid electrolyte layer 130 .

[0409] The laminate 100 can be manufactured by laminating the negative electrode 120 using a known method on the solid electrolyte layer 130 provided on the positive electrode 110 as described above, with the negative electrode electrolyte layer 121 in contact with the surface of the solid electrolyte layer 130. Thus, the solid electrolyte layer 130 and the negative electrode active material layer 121 are in contact and electrically connected.

[0410] As described above, the obtained all-solid-state lithium-ion battery 100 is provided by having the solid electrolyte layer 130 in contact with the positive electrode 110 and the negative electrode 120 so as not to short-circuit the positive electrode 110 and the negative electrode 120. The provided all-solid-state lithium-ion battery 100 is connected to an external power source and charged by applying a negative potential to the positive electrode 110 and a positive potential to the negative electrode 120.

[0411] Furthermore, the charged all-solid-state lithium-ion battery 100 is discharged by connecting a discharge circuit to the positive electrode 110 and the negative electrode 120 and passing electricity through the discharge circuit.

[0412] According to the positive electrode active material for an all-solid-state lithium ion battery having the above-described structure, lithium ions can be smoothly transferred between the positive electrode and the solid electrolyte, thereby improving battery performance.

[0413] According to the electrode having the above-described structure, since it contains the above-described positive electrode active material for an all-solid-state lithium-ion battery, the battery performance of the all-solid-state lithium-ion battery can be improved.

[0414] The all-solid-state lithium-ion battery having the above-described configuration exhibits excellent battery performance because it includes a positive electrode active material containing the above-described lithium metal composite oxide.

[0415] While preferred embodiments of the present invention have been described above with reference to the accompanying drawings, the present invention is not limited to the examples described above. The shapes and combinations of the components shown in the above examples are merely examples and may be modified in various ways based on design requirements, etc., without departing from the spirit of the present invention.

[0416] Example

[0417] Next, the present invention will be described in further detail with reference to examples.

[0418] <Composition Analysis>

[0419] The composition analysis of LiMO produced by the method described later was performed by the method described in the above-mentioned [Composition Analysis].

[0420] <Measurement of (1)>

[0421] The total pore volume, ie, V, of LiMO produced by the method described later is measured by the method described in the above-mentioned [Measurement of V].

[0422] <Measurement of (2)>

[0423] The specific surface area S of LiMO produced by the method described later is measured by the method described in the above-mentioned [Measurement of S].

[0424] <Formula (A)>

[0425] The value of the following formula (A) was determined using the values ​​of V and S obtained above.

[0426] S / (V×1000) Formula (A)

[0427] <Measurement of the Area of ​​the Hysteresis Part of the Adsorption Isotherm and Desorption Isotherm>

[0428] The areas of the hysteresis parts of the adsorption isotherm and the desorption isotherm were measured by the method described in the above-mentioned [Measurement of S1].

[0429] <Measurement of Peak Maximum of Log Differential Pore Volume>

[0430] Find the peak maximum of the log differential pore volume by the method described in the above <Measurement of Peak Maximum of Log Differential Pore Volume>.

[0431] <Measurement of Average Particle Size>

[0432] Measure the cumulative volume particle size D 50 at 50% by the method described in the above <Measurement of Average Particle Size D 50 (μm).

[0433] <Measurement of Tap Density>

[0434] The tap density uses the value obtained by the method described in the above <Method for Measuring Tap Density>.

[0435] <Manufacture of Positive Electrode for Lithium Secondary Battery>

[0436] Add and knead LiMO, conductive material (acetylene black), and binder (PVdF) in a proportion such that the composition becomes LiMO:conductive material:binder = 92:5:3 (mass ratio) to prepare a paste-like positive electrode mixture. When preparing the positive electrode mixture, use N-methyl-2-pyrrolidone as an organic solvent.

[0437] Apply the obtained positive electrode mixture onto an Al foil with a thickness of 40 μm serving as a current collector, dry it at 60 °C for 1 hour, and perform vacuum drying at 150 °C for 8 hours to obtain a positive electrode for a lithium secondary battery. The electrode area of this positive electrode for a lithium secondary battery is set to 34.96 cm 2 .

[0438] <Manufacture of Lithium Secondary Battery (Coin-Type Half Cell)>

[0439] Perform the following operations inside a glove box under an argon atmosphere.

[0440] Place the positive electrode for a lithium secondary battery manufactured in <Manufacture of Positive Electrode for Lithium Secondary Battery> face down with the aluminum foil side on the lower cover of a component for a coin-type battery R2032 (manufactured by Takizawa Co., Ltd.), and place a separator (porous polyethylene membrane) on it. Inject 300 μl of electrolyte. The electrolyte used is an electrolyte 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.

[0441] Next, metallic lithium was used as the negative electrode, the negative electrode was placed on the upper side of the laminated film separator, a top cover was installed via a gasket, and the battery was caulked with a caulking machine to produce a lithium secondary battery (coin-type half-cell R2032, hereinafter sometimes referred to as a "half-cell").

[0442] [Charge and discharge test]

[0443] Using the half-cell produced by the above method, a discharge rate test and a cycle test were performed after initial charge and discharge to evaluate the discharge rate characteristics and the cycle characteristics.

[0444] The initial charge and discharge were performed at a test temperature of 25°C, with a constant current and constant voltage charge and discharge current of 0.2 CA. When 1-yzw ≥ 0.8 in the composition formula (I), the maximum charge voltage was set to 4.35V and the minimum discharge voltage was set to 2.8V. When 1-yzw < 0.8 in the composition formula (I), the maximum charge voltage was set to 4.3V and the minimum discharge voltage was set to 2.5V.

[0445] Discharge rate test

[0446] (In the case where 1-yzw≥0.8 in the composition formula (I))

[0447] Test temperature 25℃

[0448] Maximum charging voltage 4.35V, charging current 1CA, constant current and constant voltage charging

[0449] Minimum discharge voltage 2.8V, discharge current 1CA or 5CA, constant current discharge

[0450] (In the case where 1-yzw<0.8 in the composition formula (I))

[0451] Test temperature 25℃

[0452] Maximum charging voltage 4.3V, charging current 1CA, constant current and constant voltage charging

[0453] Minimum discharge voltage 2.5V, discharge current 1CA or 5CA, constant current discharge

[0454] The discharge capacity when discharged at a constant current of 1CA and the discharge capacity when discharged at a constant current of 5CA were used to calculate the 5CA / 1CA discharge capacity retention ratio as an indicator of discharge rate performance. A higher 5CA / 1CA discharge capacity retention ratio indicates better discharge rate performance and higher output power of the lithium secondary battery.

[0455] ··5CA / 1CA discharge capacity retention rate

[0456] 5CA / 1CA discharge capacity retention rate (%)

[0457] =Discharge capacity at 5CA / Discharge capacity at 1CA×100

[0458] Following the discharge rate test, a cycle test was performed, repeating 50 charge and discharge cycles under the following conditions.

[0459] Cyclic test

[0460] (In the case where 1-yzw≥0.8 in the composition formula (I))

[0461] Test temperature 25℃

[0462] Maximum charging voltage 4.35V, charging current 0.5CA, constant current and constant voltage charging

[0463] Minimum discharge voltage 2.8V, discharge current 1CA, constant current discharge

[0464] (In the case where 1-yzw<0.8 in the composition formula (I))

[0465] Test temperature 25℃

[0466] Maximum charging voltage 4.3V, charging current 1CA, constant current and constant voltage charging

[0467] Minimum discharge voltage 2.5V, discharge current 1CA, constant current discharge

[0468] The discharge capacity at the first cycle was set as the cycle initial capacity, and the value obtained by dividing the discharge capacity at the 50th cycle by the cycle initial capacity was calculated and set as the cycle retention rate.

[0469] A lithium secondary battery was produced by the methods described in the above-mentioned <Production of a positive electrode for a lithium secondary battery> and <Production of a lithium secondary battery (coin-type half cell)>.

[0470] Charge and discharge test

[0471] The cycle retention rate was measured using the prepared half-cell by the method described in the above-mentioned [Charge and Discharge Test].

[0472] Example 1

[0473] ·Manufacturing of LiMO1

[0474] After water was added to a reaction vessel equipped with a stirrer and an overflow tube, an aqueous sodium hydroxide solution was added, and nitrogen gas was introduced into the reaction vessel. The liquid temperature in the reaction vessel was maintained at 50°C.

[0475] An aqueous nickel sulfate solution, an aqueous cobalt sulfate solution, and an aqueous manganese sulfate solution are mixed in a ratio of nickel atoms, cobalt atoms, and manganese atoms of 0.60:0.20:0.20, and zirconium sulfate is further added in a ratio of Zr / (Ni+Co+Mn)=0.005 to obtain a raw material mixed solution 1.

[0476] Next, the raw material mixed solution 1 and an aqueous ammonium sulfate solution as a complexing agent were continuously added to the reaction tank under stirring.

[0477] A sodium hydroxide aqueous solution was added dropwise at appropriate times so that the pH of the solution in the reaction vessel became 11.9 (measured value when the liquid temperature of the aqueous solution was 40° C.), thereby obtaining a nickel-containing metal composite hydroxide.

[0478] The obtained nickel-containing metal composite hydroxide was washed and then dehydrated using a centrifuge.

[0479] Furthermore, washing, dehydration, isolation, and drying at 105° C. were performed to obtain a nickel-containing metal composite hydroxide 1.

[0480] Thereafter, the nickel-containing metal composite hydroxide 1, lithium hydroxide monohydrate powder, and potassium sulfate powder were mixed.

[0481] At this time, Li / (Ni+Co+Mn)=1.07 (mol / mol), and the mixing ratio of K and Li elements was weighed and mixed in a ratio of K2SO4 / (LiOH+K2SO4)=0.1 (mol / mol).

[0482] The mixture was fired at 650° C. for 5 hours in an oxygen atmosphere to obtain a fired product.

[0483] Afterwards, the burned material is broken into pieces.

[0484] After crushing, the mixture was calcined at 940°C for 5 hours in an oxygen atmosphere to obtain a calcined product. The calcined product was crushed to obtain a powder.

[0485] The obtained powder and pure water adjusted to a liquid temperature of 5° C. were mixed so that the weight ratio of the powder to the total amount became 0.3, thereby preparing a slurry.

[0486] The prepared slurry was stirred for 20 minutes and then dehydrated.

[0487] Furthermore, the powder was washed with pure water adjusted to a liquid temperature of 5° C. and sprayed with water twice the weight of the powder, followed by dehydration to obtain a wet cake 1 having a moisture content of 17.0% per unit weight.

[0488] The wet cake 1 was spread over a sagger, and the sagger was placed in a static state into a roller hearth furnace set at a maximum temperature of 760° C., whereby heat treatment was performed at 760° C. for 5 hours.

[0489] After the heat treatment, the molten metal was put into a pin mill operated at 16,000 rpm to be crushed to obtain LiMO1.

[0490] LiMO1 has a layered structure. As a result of composition analysis of LiMO1, in the composition formula (I), x=0.02, y=0.20, z=0.20, and w=0.004.

[0491] Comparative Example 1

[0492] After water was added to a reaction vessel equipped with a stirrer and an overflow tube, an aqueous sodium hydroxide solution was added, and nitrogen gas was introduced into the reaction vessel. The liquid temperature in the reaction vessel was maintained at 60°C.

[0493] A nickel sulfate aqueous solution, a cobalt sulfate aqueous solution, and a manganese sulfate aqueous solution were mixed at an atomic ratio of nickel atoms, cobalt atoms, and manganese atoms of 0.60:0.20:0.20 to obtain a raw material mixed solution 2.

[0494] Next, the raw material mixed solution 2 and an aqueous ammonium sulfate solution as a complexing agent were continuously added to the reaction tank under stirring. A sodium hydroxide solution was added dropwise at appropriate times so that the pH of the solution in the reaction tank reached 12.0 (measured at a temperature of 40° C.), thereby obtaining a nickel-containing metal composite hydroxide.

[0495] The obtained nickel-containing metal composite hydroxide was washed and then dehydrated using a centrifuge.

[0496] Furthermore, washing, dehydration, isolation, and drying at 105° C. were performed to obtain a nickel-containing metal composite hydroxide 2.

[0497] Thereafter, the nickel-containing metal composite hydroxide 2 is mixed with lithium carbonate powder and potassium sulfate powder.

[0498] At this time, Li / (Ni+Co+Mn)=1.26 (mol / mol), and the mixing ratio of K and Li elements was weighed and mixed in a ratio of K2SO4 / (2×Li2CO3+K2SO4)=0.1 (mol / mol).

[0499] The obtained mixture was calcined at 925° C. for 5 hours in an oxygen atmosphere to obtain a calcined product.

[0500] Thereafter, the obtained burned product is crushed to obtain powder.

[0501] The obtained powder and pure water adjusted to a liquid temperature of 5° C. were mixed so that the weight ratio of the powder to the total amount became 0.3, thereby preparing a slurry.

[0502] The prepared slurry was stirred for 20 minutes and then dehydrated.

[0503] Furthermore, the powder was washed with a spray of water twice the weight of the powder using pure water adjusted to a liquid temperature of 5° C., and then dehydrated to obtain a wet cake 2 having a water content of 18.3% per unit weight.

[0504] The wet cake 2 was spread over the entire sagger, placed in a vacuum dryer in a static state, and dried at a set temperature of 150° C. for 8 hours to obtain LiMO 2 .

[0505] As a result of the composition analysis of LiMO2, in the composition formula (I), x=0.00, y=0.20, z=0.20, and w=0.

[0506] Example 2

[0507] After water was added to a reaction vessel equipped with a stirrer and an overflow tube, an aqueous sodium hydroxide solution was added, and nitrogen gas was introduced into the reaction vessel. The liquid temperature in the reaction vessel was maintained at 70°C.

[0508] A nickel sulfate aqueous solution, a cobalt sulfate aqueous solution, and a manganese sulfate aqueous solution were mixed at an atomic ratio of nickel atoms, cobalt atoms, and manganese atoms of 0.91:0.05:0.04 to obtain a raw material mixed solution 3.

[0509] Then, the raw material mixed solution 3 was continuously added to the reaction vessel under stirring. Sodium hydroxide aqueous solution was added dropwise at appropriate times so that the pH of the solution in the reaction vessel reached 10.6 (measured value at a temperature of 40° C.) to obtain a nickel-containing metal composite hydroxide.

[0510] The obtained nickel-containing metal composite hydroxide was washed and then dehydrated using a centrifuge.

[0511] Thereafter, washing, dehydration, isolation, and drying at 105° C. were performed to obtain a nickel-containing metal composite hydroxide 3.

[0512] Then, the nickel-containing metal composite hydroxide 3 is mixed with lithium hydroxide monohydrate powder and potassium sulfate powder.

[0513] At this time, Li / (Ni+Co+Mn)=1.10 (mol / mol), and the mixing ratio of K and Li elements was weighed and mixed in a ratio of K2SO4 / (LiOH+K2SO4)=0.1 (mol / mol).

[0514] The mixture was fired at 650° C. for 5 hours in an oxygen atmosphere to obtain a fired product.

[0515] Thereafter, the obtained burned product is crushed.

[0516] After the crushing, the mixture was further calcined at 820° C. for 5 hours in an oxygen atmosphere to obtain a calcined product. The calcined product was crushed to obtain a powder.

[0517] The obtained powder and pure water adjusted to a liquid temperature of 5° C. were mixed so that the weight ratio of the powder to the total amount became 0.3, thereby preparing a slurry.

[0518] The prepared slurry was stirred for 20 minutes and then dehydrated. Furthermore, it was washed with pure water adjusted to 5°C and sprayed with twice the weight of the powder, and then dehydrated to obtain a wet cake 3 having a moisture content of 21.5% per unit weight.

[0519] The wet cake 3 was spread over a sagger, and the sagger was placed in a static state in a roller-hearth furnace set at a maximum temperature of 760°C for a heat treatment at 760°C for 5 hours. After the heat treatment, the cake was crushed in a pin mill operated at 16,000 rpm to obtain LiMO3.

[0520] LiMO3 has a layered structure. The results of composition analysis of LiMO3 show that in the composition formula (I), x=0.01, y=0.05, z=0.04, and w=0.

[0521] Comparative Example 2

[0522] The nickel-containing metal composite hydroxide 3 obtained in the process of Example 2 was mixed with lithium hydroxide monohydrate powder and potassium sulfate powder.

[0523] At this time, Li / (Ni+Co+Mn)=1.10 (mol / mol), and the mixing ratio of K and Li elements was weighed and mixed in a ratio of K2SO4 / (LiOH+K2SO4)=0.1 (mol / mol).

[0524] The mixture was calcined at 790° C. for 5 hours in an oxygen atmosphere to obtain a calcined product, which was then crushed to obtain a powder.

[0525] The obtained powder and pure water adjusted to a liquid temperature of 5° C. were mixed so that the weight of the powder relative to the total weight became 0.3, thereby preparing a slurry.

[0526] The prepared slurry was stirred for 20 minutes and then dehydrated. Furthermore, it was washed with pure water adjusted to 5°C and sprayed with water twice the weight of the powder, and then dehydrated to obtain a wet cake 4 having a water content of 25.4% per unit weight.

[0527] The wet cake 4 was spread over the entire sagger, and placed in a vacuum dryer in a static state. The temperature was set at 150° C. and dried for 8 hours to obtain LiMO 4 .

[0528] As a result of the composition analysis of LiMO4, in the composition formula (I), x=0.02, y=0.05, z=0.04, and w=0.

[0529] Example 3

[0530] After water was added to a reaction vessel equipped with a stirrer and an overflow tube, an aqueous sodium hydroxide solution was added, and nitrogen gas was introduced into the reaction vessel. The liquid temperature in the reaction vessel was maintained at 60°C.

[0531] Next, the raw material mixed solution 3 obtained in Example 2 and an aqueous ammonium sulfate solution as a complexing agent were continuously added to the reaction tank under stirring. A sodium hydroxide solution was added dropwise at appropriate times so that the pH of the solution in the reaction tank reached 11.9 (measured at a temperature of 40°C), thereby obtaining a nickel-containing metal composite hydroxide.

[0532] The obtained nickel-containing metal composite hydroxide was washed and then dehydrated using a centrifuge.

[0533] Thereafter, washing, dehydration, isolation, and drying at 105° C. were performed to obtain a nickel-containing metal composite hydroxide 4.

[0534] The nickel-containing metal composite hydroxide 4 is mixed with lithium hydroxide monohydrate powder and potassium sulfate powder.

[0535] At this time, Li / (Ni+Co+Mn)=1.10 (mol / mol), and the mixing ratio of K and Li elements was weighed and mixed in a ratio of K2SO4 / (LiOH+K2SO4)=0.1 (mol / mol).

[0536] The mixture was fired at 650° C. for 5 hours in an oxygen atmosphere to obtain a fired product.

[0537] The resulting burnt product is then crushed.

[0538] After the crushing, the mixture was further calcined at 820° C. for 5 hours in an oxygen atmosphere to obtain a calcined product. The calcined product was crushed to obtain a powder.

[0539] The obtained powder and pure water adjusted to a liquid temperature of 5° C. were mixed so that the weight ratio of the powder to the total amount became 0.3, thereby preparing a slurry.

[0540] The prepared slurry was stirred for 20 minutes and then dehydrated. Furthermore, it was washed with pure water adjusted to 5°C and sprayed with water twice the weight of the powder, and then dehydrated to obtain a wet cake 5 having a moisture content of 21.3% per unit weight.

[0541] The wet cake 5 was spread over a sagger, and the sagger was placed in a static state in a roller-hearth furnace set at a maximum temperature of 760°C for a heat treatment at 760°C for 5 hours. After the heat treatment, the cake was crushed in a pin mill operated at 16,000 rpm to obtain LiMO5.

[0542] LiMO5 has a layered structure. The results of composition analysis of LiMO5 show that in the composition formula (I), x=0.01, y=0.05, z=0.04, and w=0.

[0543] Comparative Example 3

[0544] After water was added to a reaction vessel equipped with a stirrer and an overflow pipe, an aqueous sodium hydroxide solution was added, and nitrogen gas was introduced into the reaction vessel. The liquid temperature in the reaction vessel was maintained at 55°C.

[0545] The nickel sulfate aqueous solution and the cobalt sulfate aqueous solution were mixed at an atomic ratio of nickel atoms to cobalt atoms of 0.89:0.11 to obtain a raw material mixed solution 4.

[0546] Next, the raw material mixed solution 4 and an aqueous ammonium sulfate solution as a complexing agent were continuously added to the reaction tank under stirring. Sodium hydroxide aqueous solution was added dropwise at appropriate times so that the pH of the solution in the reaction tank reached 11.8 (measured at a temperature of 40°C) to obtain a nickel-containing metal composite hydroxide.

[0547] The obtained nickel-containing metal composite hydroxide was washed and then dehydrated using a centrifuge.

[0548] Thereafter, washing, dehydration, isolation, and drying at 105° C. were performed to obtain a nickel-containing metal composite hydroxide 5.

[0549] The nickel-containing metal composite hydroxide 5 is mixed with lithium hydroxide monohydrate powder.

[0550] At this time, the components were weighed and mixed so as to satisfy a ratio of Li / (Ni+Co)=1.10 (mol / mol).

[0551] The mixture was calcined at 720° C. for 5 hours in an oxygen atmosphere to obtain a calcined product, which was then crushed to obtain a powder.

[0552] The obtained powder and pure water adjusted to a liquid temperature of 5° C. were mixed so that the weight ratio of the powder to the total amount became 0.3, thereby preparing a slurry.

[0553] The prepared slurry was stirred for 20 minutes and then dehydrated to obtain a wet cake 5 having a water content of 11.0% per unit weight.

[0554] The wet cake 5 was spread over a sagger and placed in a vacuum dryer in a static state. The temperature was set at 150° C. and dried for 8 hours. The moisture content per unit weight after drying was less than 0.1%.

[0555] Alumina powder was added to the dried powder at a ratio of Al / (Ni+Co) = 0.01 and mixed. The mixed powder was spread over a sagger and heat treated at 720°C for 5 hours in an oxygen atmosphere. After the heat treatment, LiMO6 was obtained by crushing.

[0556] As a result of the composition analysis of LiMO6, in the composition formula (I), x=-0.01, y=0.11, z=0.00, and w=0.01.

[0557] Table 1 below shows the composition ratios of Examples 1 to 3 and Comparative Examples 1 to 3, the types and contents of added elements, the total pore volume, the BET specific surface area, S / (V×1000), the average particle size, the tap density, the area of ​​the hysteresis portion of the adsorption isotherm and the desorption isotherm, the peak maximum value of the log differential pore volume, the discharge capacity retention rate, and the cycle retention rate.

[0558] Table 1

[0559]

[0560] As shown in Table 1, Examples 1 to 3 satisfying (1) and (2) had higher cycle retention rates and higher discharge capacity retention rates than Comparative Examples 1 to 3.

[0561] This is considered to be because Examples 1 to 3, in which the wet cake was subjected to a disintegration step after heat treatment, had fewer fine pores generated by aggregation of LiMO particles than Comparative Examples 1 to 3, which were subjected to a drying step.

[0562] Hysteresis of Adsorption Isotherm and Desorption Isotherm

[0563] Figure 2 The adsorption isotherm and desorption isotherm of nitrogen of LiMO of Example 1 are shown in FIG. Figure 2 As shown in , the adsorption isotherm and desorption isotherm of Example 1 are substantially consistent with each other, and no hysteresis is observed. Therefore, it can be confirmed that the LiMO of Example 1 has few micropores of 200 nm or less and a small proportion of bottleneck-type pores.

[0564] Figure 3 The nitrogen adsorption isotherm and desorption isotherm of LiMO of Comparative Example 3 are shown in FIG. Figure 3 As shown in , the hysteresis observed between the adsorption isotherm and the desorption isotherm of Comparative Example 3 is large. Therefore, it can be confirmed that the LiMO of Comparative Example 3 has many micropores of 200 nm or less and a large proportion of bottleneck-type pores.

[0565] Explanation of symbols

[0566] 1…Separator, 2…Positive electrode, 3…Negative electrode, 4…Electrode assembly, 5…Battery can, 6…Electrolyte, 7…Top insulator, 8…Seal, 10…Lithium secondary battery, 21…Positive electrode lead, 31…Negative electrode lead, 100…Layer stack, 110…Positive electrode, 111…Positive electrode active material layer, 112…Positive electrode current collector, 113…External terminal, 120…Negative electrode, 121…Negative electrode electrolyte layer, 122…Negative electrode current collector, 123…External terminal, 130…Solid electrolyte layer, 200…External packaging, 200a…Opening, 1000…All-solid-state lithium-ion battery< / cam> < / limo>

Claims

1. A lithium metal composite oxide, which is a lithium metal composite oxide having a layered structure, contains at least Li, Ni, and element X, where the element X is one or more elements selected from the group consisting of Co, Mn, Fe, Cu, Ti, Mg, Al, B, W, Mo, Nb, Zn, Sn, Zr, Ga, La, and V, the physical property values obtained by measuring the nitrogen adsorption isotherm by the gas adsorption method satisfy the following (1) and (2): (1): The total pore volume V calculated from the nitrogen adsorption amount when the relative pressure p / p0 is 0.99 in the nitrogen adsorption isotherm satisfies 0.005 cm 3 / g or less; (2): The value of the following formula (A) satisfies 0.18 or more, S / (V×1000) formula (A) In formula (A), S is the specific surface area of ​​the lithium metal composite oxide obtained by the BET method, and its unit is m 2 / g, V is the total pore volume of the lithium metal composite oxide obtained from the nitrogen adsorption amount at a relative pressure of 0.99 in the adsorption isotherm, and its unit is cm 3 / g, which satisfies the following formula (I), Li[Li x (Ni (1-y-z-w) Co y Mr z M w ) 1-x ]O2(I) in, 0<x≤0.2, 0≤y≤0.4, 0≤z≤0.35, 0≤w≤0.1, y + z + w<0.50, M represents one or more elements selected from the group consisting of Fe, Cu, Ti, Mg, Al, W, B, Mo, Nb, Zn, Sn, Zr, Ga, La, and V.

2. The lithium metal composite oxide according to claim 1, wherein x is 0.01 or more and 0.20 or less.

3. The lithium metal composite oxide according to claim 1 or 2, wherein The 50% cumulative diameter, i.e. the average particle size D, is obtained from the particle size distribution measurement. 50 The thickness satisfies a range of 1 μm to 10 μm.

4. The lithium metal composite oxide according to claim 3, wherein The 50% cumulative diameter, i.e. the average particle size D, is obtained from the particle size distribution measurement. 50 The thickness satisfies a range of 1.5 μm to 8 μm.

5. The lithium metal composite oxide according to claim 1 or 2, wherein In the nitrogen adsorption isotherm measurement and the desorption isotherm measured immediately after the adsorption isotherm, the area of ​​the region formed between the adsorption isotherm and the desorption isotherm in the relative pressure range of p / p0 of 0.5 or more and 0.9 or less satisfies 0.02 cm 3 / g or less.

6. The lithium metal composite oxide according to claim 1 or 2, wherein In the pore distribution obtained by measuring the nitrogen adsorption isotherm, the maximum value of the logarithmic differential pore volume is present in the region where the pore diameter is 200 nm or less, The maximum value satisfies 0.03 cm 3 / (g · nm) or less.

7. The lithium metal composite oxide according to claim 1 or 2, wherein The S meets 0.1m 2 / g or above and 1.5m 2 / g or less.

8. The lithium metal composite oxide according to claim 1 or 2, wherein The tap density meets 1.2g / cm 3 Above and 2.5g / cm 3 the following.

9. A positive electrode active material for a lithium secondary battery, which contains the lithium metal composite oxide according to any one of claims 1 to 8.

10. A positive electrode for a lithium secondary battery, which contains the positive electrode active material for a lithium secondary battery according to claim 9.

11. A lithium secondary battery, which has the positive electrode for a lithium secondary battery according to claim 10.

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