WO2023249013A1

WO2023249013A1 - Positive electrode active material for lithium secondary battery, positive electrode for lithium secondary battery, lithium secondary battery, and method for producing positive electrode active material for lithium secondary battery

Info

Publication number: WO2023249013A1
Application number: PCT/JP2023/022772
Authority: WO
Inventors: 信吾橘; 亮栗木
Original assignee: 住友化学株式会社
Priority date: 2022-06-22
Filing date: 2023-06-20
Publication date: 2023-12-28
Also published as: JP2024001397A

Abstract

Provided is a positive electrode active material for a lithium secondary battery and the like, whereby it is possible to suppress the generation of gas and to easily achieve a lithium secondary battery having excellent rate characteristics. The positive electrode active material for a lithium secondary battery according to the present invention is such that a water vapor adsorption amount Va0.5 when a relative pressure p/p0 is 0.5 in an adsorption isotherm according to a water vapor adsorption method, a water vapor adsorption amount Va0.9 when the relative pressure p/p0 is 0.9 in the adsorption isotherm according to the water vapor adsorption method, and a water vapor adsorption amount Vd0.5 when the relative pressure p/p0 is 0.5 in a desorption isotherm according to the water vapor adsorption method satisfy a relationship of "(Vd0.5 - Va0.5)/Va0.9 ≤ 0.90", a BET specific surface area Sm measured by a nitrogen adsorption method satisfies a relationship of "Sm ≤ 0.8 m2/g", and a mass ratio W1 of lithium hydroxide and a mass ratio W2 of lithium carbonate satisfy a relationship of "W2/W1 ≤ 1.40".

Description

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

The present invention relates to a positive electrode active material for a lithium secondary battery, a positive electrode for a lithium secondary battery, a lithium secondary battery, and a method for producing a positive electrode active material for a lithium secondary battery.

In a lithium secondary battery, an electrolyte (such as a non-aqueous electrolyte or a solid electrolyte) is placed between a positive electrode and a negative electrode. In a lithium secondary battery, charging and discharging are performed by moving lithium ions between a positive electrode and a negative electrode via an electrolyte.

In a lithium secondary battery, the positive electrode is produced using, for example, a lithium metal composite oxide as a positive electrode active material. A positive electrode active material for a lithium secondary battery is produced, for example, by firing a mixture of a metal composite compound, which is a precursor of a lithium metal composite oxide, and a lithium compound.

In the above firing, the lithium compound tends to remain as a residue in the lithium metal composite oxide. The residue of the lithium compound is, for example, unreacted material of lithium hydroxide as a raw material, lithium carbonate contained as an impurity in lithium hydroxide as a raw material, and lithium carbonate produced as a by-product during calcination. The residual lithium compound becomes a cause of gas generation in the lithium secondary battery.

For this reason, it has been proposed to perform a water washing treatment (for example, see Patent Document 1) on a positive electrode active material in which a lithium compound remains as a residue in a lithium metal composite oxide.

Japanese Patent Application Publication No. 2007-273108 JP 2021-39933 Publication JP 2018-14322 Publication JP2009-99462A Japanese Patent Application Publication No. 2002-348121

Conventionally, it has not been easy to realize a lithium secondary battery that suppresses gas generation and has excellent rate characteristics.

Therefore, the present invention provides a positive electrode active material for a lithium secondary battery, a positive electrode for a lithium secondary battery, and a lithium secondary battery, which can suppress gas generation and easily realize a lithium secondary battery with excellent rate characteristics. The present invention aims to provide a method for producing a positive electrode active material for a lithium secondary battery.

The present invention has the following aspects.
[1]
A lithium metal composite oxide with a layered structure containing Li element, Ni element, and element M;
A positive electrode active material for a lithium secondary battery, comprising: a lithium compound containing lithium hydroxide and lithium carbonate;
The element M is at least one selected from the group consisting of Co, Mn, Fe, Cu, Ti, Mg, Ca, Ba, Al, Zn, Sn, Zr, Nb, B, Si, S, and P. is an element,
In the adsorption isotherm of the water vapor adsorption method, the water vapor adsorption amount Va _0.5 when the relative pressure p/p ₀ between the water vapor pressure p and the saturated vapor pressure p ₀ is 0.5, in the adsorption isotherm of the water vapor adsorption method Water vapor adsorption amount Va _0.9 when the relative pressure p/p ₀ is 0.9, and water vapor when the relative pressure p/p ₀ is 0.5 in the desorption isotherm of the water vapor adsorption method. The adsorption amount Vd _0.5 satisfies the relationship shown in the following (formula A),
The BET specific surface area Sm measured by the nitrogen adsorption method satisfies the relationship shown in the following (formula B), and
The mass proportion W1 of the lithium hydroxide and the mass proportion W2 of the lithium carbonate satisfy the relationship shown in the following (Formula C),
Positive electrode active material for lithium secondary batteries.
(Vd _0.5 - Va _0.5 )/Va _0.9 ≦0.90 (Formula A)
Sm≦0.8m ² /g (Formula B)
W2/W1≦1.40 (Formula C)
[2]
The lithium metal composite oxide is
Represented by the following (compositional formula I),
The positive electrode active material for a lithium secondary battery according to [1].
Li[Li _m (Ni _(1-x-y) C _x M1 _y ) _1-m ] O ₂ ... (compositional formula I)
(In (compositional formula I), M1 is at least one member selected from the group consisting of Mn, Fe, Cu, Ti, Mg, Ca, Ba, Al, Zn, Sn, Zr, B, Si, S, and P. m, x, and y satisfy the relationships shown in -0.1≦m≦0.2, 0≦x≦0.5, 0<y≦0.7, and x+y<1 .)
[3]
The BET specific surface area Sm satisfies the relationship shown in the following formula (B1),
The positive electrode active material for a lithium secondary battery according to [1] or [2].
0.2m ² /g≦Sm≦0.7m ² /g (Formula B1)
[4]
The mass proportion W2 of the lithium carbonate satisfies the relationship shown in the following formula (D),
The positive electrode active material for a lithium secondary battery according to any one of [1] to [3].
W2≦0.70% by mass (Formula D)
[5]
The eluted lithium amount W3 of the positive electrode active material for lithium secondary batteries, measured by neutralization titration method, satisfies the relationship shown in the following formula (E),
The positive electrode active material for a lithium secondary battery according to any one of [1] to [4].
W3≦0.50% by mass (Formula E)
[6]
In the diffraction pattern of powder X-ray diffraction measured with CuKα rays, the crystal strain calculated from the diffraction pattern in which the diffraction angle 2θ is within the range of 10° or more and 90° or less is 0.10° or less.
The positive electrode active material for a lithium secondary battery according to any one of [1] to [5].
[7]
The average pore diameter measured by nitrogen adsorption method is 150 nm or less,
The positive electrode active material for a lithium secondary battery according to any one of [1] to [6].
[8]
The pore volume measured by nitrogen adsorption method is 0.0005 cm ³ /g or more and 0.0150 cm ³ /g or less,
The positive electrode active material for a lithium secondary battery according to any one of [1] to [7].
[9]
50% cumulative volume particle size _D50 is 3 μm or more and 30 μm or less,
The positive electrode active material for a lithium secondary battery according to any one of [1] to [8].
[10]
Having a positive electrode active material for a lithium secondary battery according to any one of [1] to [9],
Positive electrode for lithium secondary batteries.
[11]
Having the positive electrode for a lithium secondary battery according to [10],
Lithium secondary battery.
[12]
A method for producing a positive electrode active material for a lithium secondary battery, the method comprising:
a preparation step of preparing a fired powder of a metal composite compound that is a precursor of a lithium metal composite oxide and a lithium compound;
a humidification step of performing a humidification treatment on the baked powder prepared in the preparation step;
a drying step of producing the positive electrode active material for a lithium secondary battery by performing a drying treatment on the fired powder subjected to the humidification treatment in the humidification step,
In the humidification step, the humidification process is performed in an atmosphere where the dew point is 50 ° C. or more and 90 ° C. or less and the CO ₂ concentration is 200 ppm or less.
A method for producing a positive electrode active material for a lithium secondary battery.
[13]
In the humidification step, the humidification process is performed in an atmosphere with a temperature of 80° C. or higher and 400° C. or lower.
The method for producing a positive electrode active material for a lithium secondary battery according to [12].
[14]
In the drying step, the drying process is performed in an atmosphere with a temperature of 100° C. or higher and 400° C. or lower.
The method for producing a positive electrode active material for a lithium secondary battery according to [12] or [13].

According to the present invention, a positive electrode active material for a lithium secondary battery, a positive electrode for a lithium secondary battery, and a lithium secondary battery are capable of suppressing gas generation and easily realizing a lithium secondary battery with excellent rate characteristics. , and a method for producing a positive electrode active material for a lithium secondary battery.

FIG. 1A is a diagram schematically showing a positive electrode active material produced in a related art (a state before being subjected to water washing treatment or humidification treatment). FIG. 1B is a diagram schematically showing a positive electrode active material produced in the related technology (state after washing with water). FIG. 1C is a diagram schematically showing a positive electrode active material produced in the related art (a state after performing a known humidification treatment). FIG. 2 is a diagram showing an example of an adsorption isotherm and a desorption isotherm. FIG. 3 is a flow diagram outlining a manufacturing method for manufacturing a positive electrode active material for a lithium secondary battery according to an embodiment. FIG. 4 is a schematic diagram showing an example of a lithium secondary battery. FIG. 5 is a schematic diagram showing an example of an all-solid lithium secondary battery. FIG. 6 is a diagram showing adsorption isotherms and desorption isotherms used in determining water retention parameters for (Example 1) and (Example C1).

An example of an embodiment of the present invention will be described below.

In this specification, abbreviations are used as appropriate for terms. Specifically, metal composite compounds are indicated using the abbreviation "MCC" (Metal Composite Compound). Lithium metal composite oxide is indicated using the abbreviation "LiMO" (Lithium Metal composite Oxide). The positive electrode active material for lithium secondary batteries is indicated using the abbreviation "CAM" (Cathode Active Material for lithium secondary batteries). Regarding the numerical range, for example, when it is described as "5-15 μm", it means the range from 5 μm to 15 μm, and means the numerical range including the lower limit of 5 μm and the upper limit of 15 μm.

FIGS. 1A to 1C are diagrams schematically showing CAMs according to related technology. FIG. 1A shows the CAM before being subjected to water washing or humidification. FIG. 1B shows the CAM after being subjected to water washing treatment. FIG. 1C shows the CAM after humidification treatment.

As shown in FIG. 1A, in the CAM before being subjected to water washing treatment or humidification treatment, lithium compound 61 remains in lithium metal composite oxide (LiMO) 51. In addition, among the positive electrode active materials before being subjected to water washing or humidification, LiMO51 has active sites 71 (areas surrounded by solid ellipses in the figure) that have high water retention and can cause side reactions. There is.

When this CAM is subjected to water washing treatment, the residual lithium compound 61 is removed from the LiMO 51, and the amount of the remaining lithium compound 61 is reduced, as shown in FIG. 1B. As a result, gas generation and the like can be suppressed in the lithium secondary battery. In addition, when water washing is performed, active sites 71 in LiMO51 that have high water retention and can cause side reactions can be inactivated by contact with water (in the figure, the active sites 71 are surrounded by broken ellipses). area). However, when the water washing treatment is performed, the BET specific surface area increases as the amount of lithium compound 61 remaining on the surface of LiMO 51 decreases. As a result, during the charge/discharge cycle of a lithium secondary battery, many side reactions tend to occur on the surface of LiMO51, resulting in the formation of a resistance layer made of side reaction products and surface deterioration, resulting in insufficient rate characteristics. It may happen.

On the other hand, when a known humidification process is performed, the active sites 71 can be inactivated by contact with water, as shown in FIG. (Illustrated by the area enclosed by a dashed oval). Furthermore, when the known humidification treatment is performed, unlike the case of water washing treatment, the amount of lithium compound 61 remaining on the surface of LiMO 51 does not decrease, so it is possible to suppress an excessive increase in the BET specific surface area. As a result, a lithium secondary battery with excellent rate characteristics can be obtained. However, in the implementation of the known humidification process, the residual amount of the lithium compound 61 is the same before and after the humidification process, so it may not be possible to sufficiently suppress gas generation in the lithium secondary battery. The CAM of this embodiment can suppress gas generation and manufacture a lithium secondary battery with excellent rate characteristics.

[A]CAM
In this embodiment, the CAM includes LiMO and a lithium compound. That is, in CAM, a lithium compound remains as a residue in LiMO. Each part constituting the above-mentioned CAM will be sequentially explained.

[A-1] LiMO
In the above CAM, LiMO includes at least Li element, Ni element, and element M. Element M is at least one element selected from the group consisting of Co, Mn, Fe, Cu, Ti, Mg, Ca, Ba, Al, Zn, Sn, Zr, Nb, B, Si, S, and P. It is. Element M is preferably at least one element selected from the group consisting of Co, Mn, Al, Zr, Nb and B.

Specifically, LiMO is preferably represented by the following (compositional formula I).

Li[Li _m (Ni _(1-x-y) C _x M1 _y ) _1-m ] O ₂ ... (compositional formula I)

In (compositional formula I), element M1 is selected from the group consisting of Mn, Fe, Cu, Ti, Mg, Ca, Ba, Al, Zn, Sn, Zr, Nb, B, Si, S, and P. At least one element. That is, the element M1 is an element other than the Co element among the above-mentioned elements M. Element M1 is preferably at least one element selected from the group consisting of Mn, Al, Zr, Nb, and B.

Furthermore, in (compositional formula I), each of m, x, and y preferably satisfies the relationships shown in (formula Ia) to (formula Id) below.

-0.1≦m≦0.2 (Formula Ia)
0≦x≦0.5 (Formula Ib)
0<y≦0.7...(Formula Ic)
x+y<1...(Formula Id)

In (compositional formula I), when the value of m is equal to or greater than the lower limit of the range shown in (formula Ia), the rate characteristics of the lithium secondary battery can be improved. Furthermore, in (compositional formula I), when the value of m is equal to or less than the upper limit of the range shown in (formula Ia), the initial coulombic efficiency of the lithium secondary battery can be improved. Furthermore, in (compositional formula I), m is more preferably −0.03 or more, and particularly preferably 0 or more. Furthermore, m is more preferably 0.1 or less, particularly preferably 0.07 or less. The range of m is more preferably −0.03≦m≦0.1, and particularly preferably 0≦m≦0.07.

In (compositional formula I), when the value of x satisfies the relationship shown in (formula Ib), the internal resistance of the lithium secondary battery can be reduced and the rate characteristics can be improved. Furthermore, in (compositional formula I), x is more preferably 0.01 or more, particularly preferably 0.02 or more. Furthermore, x is more preferably 0.4 or less, particularly preferably 0.3 or less. The range of x is more preferably 0.01≦x≦0.4, and particularly preferably 0.02≦x≦0.3.

In (compositional formula I), when the value of y satisfies the relationship shown in (formula Ic), the cycle maintenance rate of the lithium secondary battery can be improved. Further, in (compositional formula I), y is more preferably 0.0002 or more, particularly preferably 0.0005 or more. Furthermore, y is more preferably 0.6 or less, particularly preferably 0.5 or less. The range of y is more preferably 0.0002≦y≦0.6, and particularly preferably 0.0005≦y≦0.5.

In (compositional formula I), the initial capacity of the lithium secondary battery can be improved by making the sum (x+y) of the value of x and the value of y satisfy the relationship shown in (formula Id). In addition, in order to suppress the internal resistance of the lithium secondary battery from increasing and the rate characteristics from decreasing, the sum of the value of x and the value of y (x+y) is preferably 0.01 or more. . Further, in (compositional formula I), (x+y) is more preferably less than 0.6, particularly preferably 0.5 or less, and even more preferably 0.25 or less. The range of (x+y) is 0<x+y<1, more preferably 0.01≦x+y<0.6, particularly preferably 0.01≦x+y≦0.5, and 0.01≦x+y≦0. 25 is more preferred.

(Measurement of composition)
The composition of LiMO can be determined, for example, by measuring CAM using an ICP emission spectrometer (Optima 7300 (manufactured by PerkinElmer, Inc.), etc.). Note that m in (compositional formula I) may include Li derived from a lithium compound in addition to Li derived from LiMO. Before measuring the composition, the sample is dissolved in acid or alkali depending on the element to be measured.

The above LiMO has a layered structure.

The crystal structure of LiMO is preferably a layered rock salt structure, more preferably a hexagonal crystal structure or a monoclinic crystal structure. Specifically, the hexagonal crystal structure is P3, P3 ₁ , P3 ₂ , R3, P-3, R-3, P312, P321, P3 ₁ 12, P3 ₁ 21, P3 ₂ 12, P3 ₂ 21 , R32, P3m1, P31m, P3c1, P31c, R3m, R3c, P-31m, P-31c, P-3m1, P-3c1, R-3m, R-3c, P6, P6 ₁ , P6 ₅ , P6 ₂ , P6 ₄ , P6 ₃ , P-6, P6/m, P6 ₃ /m, P622, P6 ₁ 22, P6 ₅ 22, P6 ₂ 22, P6 ₄ 22, P6 ₃ 22, P6 mm, P6 cc, P6 ₃ cm, P6 ₃ mc, P-6m2, P-6c2, P-62m, P-62c, P6/mmm, P6/mcc, P6 ₃ /mcm, and P6 ₃ /mmc. Ru. The monoclinic crystal structure is P2, P2 ₁ , C2, Pm, Pc, Cm, Cc, P2/m, P2 ₁ /m, C2/m, P2/c, P2 ₁ /c, and C2 It belongs to one space group selected from the group consisting of /c. Among the above, the crystal structure of LiMO is hexagonal, which belongs to space group R-3m, or C2/m, in order to obtain a lithium secondary battery with high discharge capacity and excellent rate characteristics. A monoclinic type is particularly preferred.

The crystal structure of LiMO can be calculated by performing CAM powder X-ray diffraction measurement using CuKα as a radiation source and measuring the diffraction angle 2θ in the range of 10-90°. Specifically, this can be confirmed by observation using a powder X-ray diffraction measurement device (for example, Ultima IV manufactured by Rigaku Co., Ltd.).

[A-2] Lithium Compound In the above CAM, the lithium compound is a residue left in LiMO during the production of the CAM, and includes lithium hydroxide and lithium carbonate.

Specifically, the lithium compound that is the residue is the unreacted material of the raw material lithium hydroxide, the lithium carbonate contained as an impurity in the raw material lithium hydroxide, and the carbonate produced as a byproduct during calcination. Lithium etc.

[A-3] Characteristics of CAM CAM is a powder made up of a plurality of particles. Although details will be described later, the CAM powder is a fired powder.

The CAM powder may be composed only of secondary particles that are aggregated primary particles, or may be a mixture of both primary particles and secondary particles. For example, the CAM powder may include LiMO, which is a secondary particle, and primary particles of a lithium compound.

Note that the above-mentioned "primary particles" are particles that do not have grain boundaries in appearance when the CAM is observed with a field of view of 1000 times or more and 30000 times or less using a microscope (such as a scanning electron microscope). The above-mentioned "secondary particles" are aggregates of primary particles.

The above CAM satisfies (Requirement 1), (Requirement 2), and (Requirement 3) shown below. By satisfying (Requirement 1), (Requirement 2), and (Requirement 3), the above-mentioned CAM can easily realize a lithium secondary battery that suppresses gas generation and has excellent rate characteristics.

[A-3-1] (Requirement 1) Water retention parameter The above CAM is based on the adsorption isotherm of the water vapor adsorption method when the relative pressure p/p ₀ between the water vapor pressure p and the saturated vapor pressure p ₀ is 0.5. Water vapor adsorption amount Va _0.5 , water vapor adsorption amount Va _0.9 when the relative pressure p/p ₀ is 0.9 in the adsorption isotherm of the water vapor adsorption method, and relative pressure p in the desorption isotherm of the water vapor adsorption method. The water vapor adsorption amount Vd _0.5 when /p ₀ is 0.5 satisfies the relationship (requirement 1) shown in (Formula A) below.

(Vd _0.5 - Va _0.5 )/Va _0.9 ≦0.90 (Formula A)

(Vd _0.5 - Va _0.5 )/Va _0.9 defines a water retention parameter indicating water retention, and means that as the value decreases, it becomes harder to retain water. When the relationship shown in (Formula A) is satisfied, active sites in CAM that are likely to cause side reactions are effectively inactivated by contact with water. This is thought to be because Ni, which is active on the CAM surface, becomes inactivated by forming a NiO-OH structure upon contact with water. Therefore, a lithium secondary battery manufactured using a CAM that satisfies the relationship shown in (Formula A) can sufficiently suppress gas generation.

From the viewpoint shown above, it is more preferable that the water retention parameter satisfies formula (A1).

(Vd _0.5 - Va _0.5 )/Va _0.9 ≦0.85 (Formula A1)

Note that the water vapor pressure p and the saturated vapor pressure p ₀ at the time of measurement are values when the temperature is 25°C. Va _0.5 , Va _0.9 , and Vd _0.5 are amounts (unit: cm ³ (STP)/g) that a sample of CAM adsorbs water vapor per unit mass (for example, 1 g).

(Measurement of water retention parameters)
The adsorption isotherm and the desorption isotherm are obtained by changing the relative pressure p/p ₀ condition and measuring the amount of water vapor adsorbed by the sample. The amount of water vapor adsorption is measured by performing a water vapor adsorption method using a vapor adsorption measuring device. The vapor adsorption measuring device is, for example, "BELSORP (registered trademark)-18" manufactured by Microtrac Bell Co., Ltd., and the amount of water vapor adsorption is measured under the following measurement conditions.

・Filled sample amount: 0.5g
・Sample pretreatment conditions: 5 hours treatment at 200℃ under vacuum ・Thermostatic chamber temperature: 50℃
・Adsorption temperature: 25℃
・Saturated vapor pressure: 3.169kPa
・Adsorption equilibrium time: 500 seconds

FIG. 2 is a diagram showing an example of an adsorption isotherm and a desorption isotherm. In FIG. 2, the horizontal axis is the relative pressure p/p ₀ , and the vertical axis is the water vapor adsorption amount V (cm ³ (STP)/g). In FIG. 2, the adsorption isotherm is shown as a solid line, and the desorption isotherm is shown as a broken line.

As shown in FIG. 2, in this embodiment, the adsorption isotherm (solid line) is the locus of the water vapor adsorption amount V measured when p/ _po is increased to 0.9. In the adsorption isotherm, V increases as p/ _po increases. On the other hand, in this embodiment, the desorption isotherm (dashed line) is obtained by increasing p/ _po to a point exceeding 0.9 in order to obtain an adsorption isotherm, and then lowering it from that point. This is the trajectory of V to be measured. In the desorption isotherm, V decreases as p/ _po decreases.

As can be seen from FIG. 2, the adsorption isotherm and desorption isotherm do not match. For example, V when p/ _po is 0.5 in the adsorption isotherm (i.e., Va _0.5 ) is V (i.e., Vd 0.5 ) when p/ _po is 0.5 in the desorption isotherm _{. 5} ) (Va _0.5 < Vd _0.5 ). That is, the value obtained by subtracting Va _0.5 from Vd _0.5 is greater than zero (Vd _0.5 - Va _0.5 >0). Thus, hysteresis exists between adsorption and desorption of water vapor.

(Vd _0.5 - Va _0.5 )/Va _0.9 is the value obtained by subtracting Va _0.5 from Vd _0.5 (Vd _0.5 - Va _0.5 ) when the amount of water vapor adsorption is at its maximum. It is a value divided by Va _0.9 , which is an index indicating the degree of hysteresis, that is, a water retention parameter (water retention index), and means that as the value becomes smaller, it becomes harder to retain water.

The lower limit value of (Vd _0.5 - Va _0.5 )/Va _0.9 is not particularly limited, but (Vd _0.5 - Va _0.5 )/Va _0.9 >0 may be satisfied, (Vd _0.5 - Va _0.5 )/Va _0.9 >0.1. The above range of (Vd _0.5 - Va _0.5 )/Va _0.9 is preferably 0<(Vd _0.5 - Va _0.5 )/Va _0.9 ≦0.90, and 0<(Vd _0.5 −Va _0.5 )/Va _0.9 ≦0.85 is more preferable, and 0.1<(Vd _0.5 −Va _0.5 )/Va _0.9 ≦0.85 is particularly preferable.

[A-3-2] (Requirement 2) BET specific surface area Sm
In the above CAM, the BET specific surface area Sm measured by the nitrogen adsorption method satisfies the relationship (requirement 2) shown in the following (Formula B).

Sm≦0.8m ² /g (Formula B)

When the relationship shown in (Formula B) is satisfied, the resistance layer and surface deterioration due to side reactions on the CAM surface are less likely to occur, so side reactions occur on the CAM surface during the charge/discharge cycle of the lithium secondary battery. This can be sufficiently suppressed. As a result, the rate characteristics of the lithium secondary battery can be improved. From the viewpoint shown above, it is preferable that Sm satisfies 0.2 m ² /g≦Sm≦0.8 m ² /g.

From the viewpoint shown above, it is more preferable that Sm satisfies the relationship shown in the following formula (B1).

0.2m ² /g≦Sm≦0.7m ² /g (Formula B1)

When the lower limit of (Formula B1) or more is satisfied, there are sufficient surface reaction fields of CAM, and the rate characteristics of the lithium secondary battery can be improved.

(Measurement of Sm)
Sm is a value measured by the BET (Brunauer, Emmett, Teller) method. In the measurement of Sm, nitrogen gas is used as the adsorption gas. The BET specific surface area (unit: m ² /g) can be determined by drying 1 g of CAM at a temperature of 105° C. for 30 minutes in a nitrogen atmosphere, and then using a BET specific surface area meter (for example, Macsorb (registered) manufactured by Mountech Co., Ltd.). Trademark)).

[A-3-3] (Requirement 3) W2/W1
In the above CAM, the mass proportion W1 of lithium hydroxide and the mass proportion W2 of lithium carbonate satisfy the relationship (requirement 3) shown in the following (Formula C).

W2/W1≦1.40...(Formula C)

When the relationship shown in (Formula C) is satisfied, the amount of lithium carbonate among the lithium compounds contained in the CAM is not excessive compared to the amount of lithium hydroxide. As a result of various studies, it has been found that lithium carbonate is more likely to contribute to the amount of gas generated (cc/g) resulting from side reactions in a lithium secondary battery than lithium hydroxide. A CAM that satisfies the above (Formula C) indicates that the mass proportion of lithium carbonate contained in the lithium compound is low. Therefore, gas generation can be sufficiently suppressed in the lithium secondary battery.

From the above viewpoint, it is more preferable that W1 and W2 satisfy the relationship shown in the following formula (C1).

W2/W1≦1.00...(Formula C1)

Although the lower limit value of W2/W1 is not particularly limited, it may be W2/W1≧0 or W2/W1>0. The above range of W2/W1 is, for example, 0≦W2/W1≦1.40, 0≦W2/W1≦1.00, 0<W2/W1≦1.40, 0<W2/W1≦1.00. Can be mentioned.

In the above CAM, W2 preferably satisfies the relationship shown in the following formula (D).

W2≦0.70% by mass...(Formula D)

By satisfying (Formula D), gas generation due to side reactions of lithium carbonate can be suppressed.

From the above viewpoint, it is more preferable that the relationship shown in the following formula (D1) is satisfied.

W2≦0.60% by mass...(Formula D1)

The lower limit of W2 is not particularly limited, but may be W2≧0% by mass or W2>0% by mass. The range of W2 is, for example, 0 mass%≦W2≦0.70 mass%, 0 mass%≦W2≦0.60 mass%, 0 mass%<W2≦0.70 mass%, 0 mass%<W2≦ An example is 0.60% by mass.

Further, in the CAM, it is preferable that the amount of eluted lithium W3 measured by neutralization titration satisfies the relationship shown in the following formula (E).
It is preferable.

W3≦0.50% by mass...(Formula E)

By satisfying (Formula E), gas generation due to side reactions of the lithium compound can be suppressed.

From the above viewpoint, it is more preferable that the relationship shown in the following formula (E1) is satisfied.

W3≦0.40% by mass...(Formula E1)

The lower limit value of W3 is not particularly limited, but W3>0% by mass may be satisfied. The range of W3 is particularly preferably 0% by mass<W3≦0.50% by mass, and even more preferably 0% by mass≦W3≦0.40% by mass.

(Neutralization titration method)
The above W1 and W2 are measured by neutralization titration method.

When measuring W1 and W2, first, 5 g of CAM and 100 g of pure water are placed in a 100 mL polypropylene container to prepare a slurry. After a stirring bar is placed inside a container containing the slurry, the slurry is stirred for 5 minutes while the container is sealed. After stirring is complete, filter the slurry.

Then, hydrochloric acid having a concentration of 0.1 mol/L is continuously added dropwise to 60 g of the filtrate obtained by filtering the slurry. Hydrochloric acid is added dropwise using an automatic titrator (AT-610, manufactured by Kyoto Denshi Kogyo Co., Ltd.) until the pH reaches 4.0. At this time, in the filtrate to which hydrochloric acid was added dropwise, the titration amount A [mL] of hydrochloric acid when the pH becomes 8.3±0.1, and the titration amount A [mL] of hydrochloric acid when the pH becomes 4.5±0.1. Find the amount B [mL].

After that, W1 and W2 are calculated using (Formula b) and (Formula c) below. In addition, in (formula b) and (formula c), the molecular weight of lithium hydroxide and the molecular weight of lithium carbonate are calculated with the atomic weights as H: 1.000, Li: 6.941, C: 12, O: 16. (that is, the molecular weight of lithium hydroxide: 23.941, the molecular weight of lithium carbonate: 73.882).

W1 [mass%] = {0.1×(2A-B)/1000}×{23.941/(20×60/100)}×100 (Formula b)
W2 [mass%] = {0.1×(B-A)/1000}×{73.882/(20×60/100)}×100 (formula c)

Then, from the results of W1 and W2 calculated above, W3 can be found using (formula d).

W3 [mass%] = W2 x (2 x 6.941/73.882) + W1 x (6.941/23.941)... (formula d)

[A-3-4] Other properties [A-3-4-1] Crystal strain The above CAM has a diffraction angle 2θ within the range of 10-90° in the diffraction pattern of powder X-ray diffraction measured with CuKα rays. It is preferable that the crystal strain calculated from the diffraction pattern included in is 0.10° or less. This facilitates the diffusion of lithium ions in the planar direction of the layered structure of LiMO included in the CAM, reducing the diffusion resistance of lithium ions and improving the rate characteristics.

From the viewpoint shown above, it is more preferable that the crystal strain is 0.08° or less.

Crystal strain is measured by powder X-ray diffraction. Powder X-ray diffraction is performed using an X-ray diffraction apparatus (eg, Bruker D8 Advance) under the following measurement conditions.

(Measurement condition)
・Sampling width: 0.02
・Scan speed: 4°/min

Powder X-ray diffraction is performed using CuKα rays under the conditions that the measurement range of the diffraction angle 2θ is 10° or more and 90° or less. Then, crystal strain can be determined by analyzing the diffraction pattern obtained by performing powder X-ray diffraction using the Rietveld analysis method. Rietveld analysis is a method of comparing an actually measured powder X-ray diffraction pattern with a simulation pattern from a crystal structure model, and optimizing the crystal structure parameters in the crystal structure model so that the difference between the two is minimized. Optimization of crystal strain is performed using a layered rock salt crystal structure (Li _1-n _Men ) (Me _1-n _Lin ) O ₂ as an initial crystal structure model.

[A-3-4-2] Average pore diameter/pore volume The average pore diameter of the CAM measured by the nitrogen adsorption method described above is preferably 150 nm or less. Thereby, a decrease in electrode density can be prevented and a battery with high energy density can be obtained. In addition, it can have sufficient electrolyte permeability and retention, and can improve rate characteristics.

From the viewpoint shown above, the average pore diameter is more preferably 100 nm or less, particularly preferably 60 nm or less. Moreover, it is preferable that the above-mentioned average pore diameter is 10 nm or more. The average pore diameter range is more preferably 10-150 nm, particularly preferably 10-100 nm, and even more preferably 10-60 nm.

Further, the pore volume of the CAM measured by the nitrogen adsorption method is preferably 0.0005-0.015 cm ³ /g. When the pore volume is at least the lower limit of the above range, sufficient electrolyte permeability and retention can be achieved, and rate characteristics can be improved. Further, when the pore volume is less than or equal to the upper limit of the above range, the density of the CAM is improved and the energy density is likely to be improved.

From the viewpoint shown above, the lower limit of the pore volume is more preferably 0.001 cm ³ /g, and the upper limit is more preferably 0.010 cm ³ /g. Examples of the range of the pore volume mentioned above include 0.001-0.015 cm ³ /g, ^{0.0005-0.010 cm 3} /g, and ^{0.0010.010 cm 3} /g.

The average pore diameter and pore volume are calculated based on the pore diameter distribution obtained by analyzing the adsorption isotherm and desorption isotherm obtained by implementing the nitrogen adsorption method using the BJH (Barrett-Joyner-Halenda) method. Ru. The BJH method is a method in which the pore shape is assumed to be cylindrical, and analysis is performed based on a relational expression (Kelvin equation) between the pore diameter and the relative pressure of nitrogen that causes capillary condensation. The pore size distribution determined from the desorption isotherm is derived from bottleneck-shaped pores.

When measuring the above-mentioned adsorption isotherm and desorption isotherm, first, using a vacuum heat treatment device (for example, BELSORP-vacII manufactured by Microtrac Bell Co., Ltd.), the temperature is set at 150°C for 8 hours. Vacuum degassing is performed on a 10 g sample. After performing the vacuum degassing process, the adsorption isotherm and desorption isotherm of nitrogen are obtained at the temperature of liquid nitrogen (77K) using a measuring device (for example, BELSORP-mini manufactured by Microtrac Bell Co., Ltd.). The amount of nitrogen adsorbed by the sample per unit mass in the adsorption isotherm and the desorption isotherm is calculated as expressed by the volume of nitrogen gas in the standard temperature and pressure (STP).

[A-3-4-3] 50% cumulative volume particle size D ₅₀
The 50% cumulative volume particle size D ₅₀ (hereinafter sometimes referred to as D ₅₀ ) of the CAM is preferably 3 to 30 μm. By having _D50 within this range, the bulk density can be increased, and therefore the packing density can be increased. As a result, in the positive electrode for a lithium secondary battery, the contact area between the CAM particles and the conductive material particles increases, and the conductivity improves, so that the rate characteristics of the lithium secondary battery can be improved. The _D50 of the CAM is more preferably 5 μm or more, particularly preferably 7 μm or more, and even more preferably 8 μm or more. _D50 is more preferably 25 μm or less, particularly preferably 23 μm or less, and even more preferably 20 μm or less. D ₅₀ is more preferably 5-25 μm, particularly preferably 7-23 μm, even more preferably 8-20 μm.

The above _D50 is measured by laser diffraction scattering method. Specifically, when measuring _D50 , first, a dispersion liquid in which CAM powder is dispersed is obtained. The dispersion liquid is prepared by introducing 0.1 g of CAM powder into 50 ml of an aqueous sodium hexametaphosphate solution (concentration: 0.2% by mass). Next, by measuring the particle size distribution of the powder in the dispersion liquid using a laser diffraction scattering particle size distribution measuring device (for example, Microtrac MT3300EXII manufactured by Microtrac Bell Co., Ltd.), a volume-based cumulative particle size distribution curve is obtained. get. D ₅₀ (μm) corresponds to the value of the particle diameter at the time of 50% accumulation from the microparticle side in the cumulative particle size distribution curve.

[B] Method for manufacturing CAM A method for manufacturing the above-mentioned CAM will be described.

FIG. 3 is a flow diagram outlining the manufacturing method for manufacturing the CAM according to the embodiment.

When producing the above CAM, as shown in FIG. 3, a preparation step (ST10), a humidification step (ST20), and a drying step (ST30) are sequentially performed.

[B-1] Preparation process (ST10)
In the preparation step (ST10), a fired powder of MCC, which is a precursor of LiMO, and a lithium compound is prepared.

Specifically, the composition of MCC includes Ni element, Co element, and the above element M1 in a molar ratio represented by the following (Formula II).

[Ni]:[Co]:[M1]=(1-x-y):x:y (Formula II)

In (Formula II), each of x and y preferably satisfies the relationships shown below (Formula IIb) to (Formula IId). )same as).

0≦x≦0.5 (Formula IIb)
0<y≦0.7...(Formula IIc)
x+y<1...(Formula IId)

[B-1-1] MCC
MCC is, for example, a metal composite hydroxide, a metal composite oxide, or a mixture thereof.

The metal composite hydroxide is produced, for example, by a known batch coprecipitation method or continuous coprecipitation method. Hereinafter, a method for producing the metal composite hydroxide containing Ni, Co, and Al as the metal elements will be explained in detail by taking as an example.

Specifically, a nickel salt solution, a cobalt salt solution, an aluminum salt solution, and a complexing agent are reacted by a continuous coprecipitation method described in JP-A-2002-201028. As a result, a metal composite hydroxide (Ni _(1-x-y) Co _x Al _y (OH) ₂ ) containing Ni element, Co element, and element M1 in the molar ratio expressed by the above (Formula II) is produced. is manufactured.

The nickel salt that is the solute of the nickel salt solution is, for example, at least one of nickel sulfate, nickel nitrate, nickel chloride, and nickel acetate.

The cobalt salt that is the solute of the cobalt salt solution is, for example, at least one of cobalt sulfate, cobalt nitrate, cobalt chloride, and cobalt acetate.

The aluminum salt that is the solute of the aluminum salt solution is, for example, at least one of aluminum sulfate, aluminum nitrate, aluminum chloride, and aluminum acetate.

The above metal salts are mixed in proportion. That is, in the mixed solution containing the metal salt, the molar ratio of each element corresponds to the above (Formula II). Water is used here as a solvent.

A complexing agent may be used in the manufacturing process of the metal composite hydroxide. In this case, the amount of the complexing agent is such that, for example, the molar ratio to the total number of moles of metal salts (nickel salt, cobalt salt, and aluminum salt) is greater than 0 and less than or equal to 2.0.

The complexing agent is a material that can form complexes with nickel ions, cobalt ions, and aluminum ions in an aqueous solution. Complexing agents include, for example, ammonium ion donors (such as ammonium hydroxide, ammonium sulfate, ammonium chloride, ammonium carbonate, or ammonium fluoride), hydrazine, ethylenediaminetetraacetic acid, nitrilotriacetic acid, uracil diacetic acid, and glycine. At least one type.

In the coprecipitation method, the pH value of a mixed solution containing a nickel salt solution, a cobalt salt solution, an aluminum salt solution, and a complexing agent is adjusted. For this reason, an alkali metal hydroxide is added to the mixed solution before the pH of the mixed solution changes from alkaline to neutral. Alkali metal hydroxides are, for example, sodium hydroxide or potassium hydroxide.

Note that here, the pH value is measured when the temperature of the liquid mixture 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. If the temperature of the sampled mixture is not 40°C, the pH is measured after heating or cooling the mixture to 40°C.

In addition to the above nickel salt solution, cobalt salt solution, and aluminum salt solution, a complexing agent is continuously supplied to the reaction tank to cause a reaction, and Ni _(1-x-y) C _x Al _y (OH) ₂ is generated.

Here, the temperature of the reaction tank is controlled, for example, within the range of 20-80°C, preferably within the range of 30-70°C.

Furthermore, during the reaction, the pH value in the reaction tank is controlled within the range of, for example, 9-13.

Then, the reaction precipitate formed in the reaction tank is neutralized while being stirred. The time for neutralizing the reaction precipitate is, for example, in the range of 1 to 20 hours.

As the reaction tank used in the continuous coprecipitation method, a type of reaction tank in which overflow occurs can be used in order to separate the formed reaction precipitate.

When manufacturing metal composite hydroxides using a batch coprecipitation method, a reaction tank without an overflow pipe or a mechanism in which the overflowing reaction precipitate is concentrated in a concentrating tank connected to the overflow pipe and circulated back to the reaction tank. A device etc. having the following characteristics is used.

Here, various gases (for example, an inert gas such as nitrogen, argon, or carbon dioxide, an oxidizing gas such as air or oxygen, or a mixed gas thereof) may be supplied into the reaction tank.

After the above reaction is completed, the neutralized reaction precipitate is washed and isolated. Isolation is performed, for example, by dehydrating a slurry containing the reaction precipitate by centrifugation, suction filtration, or the like.

Then, the isolated reaction precipitate is dried and sieved as necessary to obtain a metal composite hydroxide.

It is preferable to wash the reaction precipitate using water or an alkaline washing liquid. In washing the reaction precipitate, it is preferable to use an alkaline washing liquid, and it is particularly preferable to use an aqueous sodium hydroxide solution as the alkaline washing liquid. Further, cleaning may be performed using a cleaning liquid containing elemental sulfur. The cleaning liquid containing elemental sulfur is an aqueous solution of potassium or sodium sulfate.

Note that in the above example, a metal composite hydroxide is produced as the MCC, but a metal composite oxide may also be prepared.

A metal composite oxide is produced, for example, by heating a metal composite hydroxide. The heating step may be performed multiple times as necessary. In the heating process, the heating temperature means the set temperature of the heating device, and when performing multiple heating processes, the heating temperature means the temperature of the process heated at the highest holding temperature among the multiple heating processes. .

The heating temperature is preferably in the range of 400-700°C, more preferably in the range of 450-680°C. As a result, the metal composite hydroxide is sufficiently oxidized and a metal composite oxide having a BET specific surface area within an appropriate range is obtained.

The time for maintaining the heating temperature in the heating step is preferably in the range of 0.1 to 20 hours, more preferably in the range of 0.5 to 10 hours. The rate of temperature increase until the heating temperature described above is reached is, for example, in the range of 50-400° C./hour. Further, the heat treatment is performed in an atmosphere containing air, oxygen, nitrogen, argon, or a mixed gas thereof.

The interior of the heating device may be an oxygen-containing atmosphere containing a moderate amount of oxygen. The oxygen-containing atmosphere may be a mixed gas atmosphere of an inert gas and an oxidizing gas, or may be a state in which an oxidizing agent is present in an inert gas atmosphere. As a result, the transition metal contained in the metal composite hydroxide is appropriately oxidized, making it easier to control the form of the metal composite oxide.

The oxygen-containing atmosphere only needs to contain a sufficient amount of oxygen atoms to oxidize the transition metal.

When the oxygen-containing atmosphere is a mixed gas atmosphere containing an inert gas and an oxidizing gas, the atmosphere inside the heating device can be controlled by passing an oxidizing gas into the heating device, or by introducing an oxidizing gas into the mixed liquid. This is carried out by bubbling, etc.

The oxidizing agent to be present in the oxygen-containing atmosphere includes peroxides such as hydrogen peroxide, peroxide salts such as permanganates, perchlorates, hypochlorites, nitric acid, halogens, or ozone.

[B-1-2] Lithium compounds Lithium compounds used in the production of LiMO include, for example, lithium carbonate, lithium nitrate, lithium acetate, lithium hydroxide, lithium hydroxide hydrate, lithium oxide, lithium chloride, and fluoride. At least one of lithium. Among these, it is preferable to use lithium hydroxide, lithium hydroxide hydrate, a mixture of lithium hydroxide and lithium carbonate, or a mixture of lithium hydroxide hydrate and lithium carbonate as the lithium compound. Further, when lithium hydroxide contains lithium carbonate, the content of lithium carbonate in lithium hydroxide is preferably 5% by mass or less.

[B-1-3] Mixing The above MCC and lithium compound are mixed in a proportion that takes into account the composition ratio of the final target product.

[B-1-4] Firing Then, a fired product is produced by performing a firing process on the mixture of MCC and a lithium compound.

The firing temperature is preferably in the range of 650-1000°C, more preferably in the range of 680-900°C, and particularly preferably in the range of 700-850°C. When the firing temperature is 650° C. or higher, a CAM having a strong crystal structure can be obtained. Further, when the firing temperature is 1000° C. or less, volatilization of lithium ions on the surface of the CAM particles can be reduced.

Furthermore, by adjusting the holding time of the firing process, the primary particle diameter of the obtained CAM can be controlled. As the holding time becomes longer, the primary particle diameter tends to increase and the BET specific surface area tends to decrease. The above retention time is adjusted as appropriate depending on the type of transition metal element used and the type and amount of the precipitant.

Specifically, the holding time of the firing treatment is preferably 0.5 to 50 hours, more preferably 1 to 20 hours. When the retention time of the firing treatment is 50 hours or less, it is possible to substantially suppress the battery performance from deteriorating due to volatilization of lithium ions. When the holding time of the firing treatment is 0.5 hours or more, crystal development is sufficient and battery performance is unlikely to deteriorate.

The heating rate until the firing temperature is reached is preferably 80°C/hour or more, more preferably 100°C/hour or more, and particularly preferably 150°C/hour or more. The rate of temperature increase until the firing temperature is reached is calculated from the time from the time when temperature raising is started until the firing temperature is reached in the firing apparatus.

It is preferable that the firing process has a plurality of firing stages at different firing temperatures. For example, the firing process preferably includes a first firing stage and a second firing stage in which firing is performed at a higher temperature than the first firing stage. Additionally, the firing process may include firing stages with different firing temperatures and firing times.

The firing process is performed in an atmosphere containing air, oxygen, nitrogen, argon, a mixed gas of these, or the like, depending on the desired composition.

The mixture of MCC and lithium compound may be calcined in the presence of an inert melting agent. The inert melting agent is added to an extent that does not impair the initial capacity of a battery using CAM, and may remain in the fired product. As the inert melting agent, for example, those described in WO2019/177032A1 can be used.

Note that the mixture may be subjected to a temporary calcination treatment before being subjected to the above calcination treatment. The temporary firing process is performed at a temperature lower than the firing temperature in the firing process. The firing temperature of the temporary firing process is, for example, in the range of 400°C or higher and lower than 700°C. The pre-firing process may be performed multiple times.

The firing device used during temporary firing is not particularly limited, and is, for example, a continuous firing furnace or a fluidized fluidized firing furnace. The continuous firing furnace is, for example, a tunnel furnace or a roller hearth kiln. The fluidized kiln is, for example, a rotary kiln.

[B-1-5] Crushing The fired product obtained by the above firing is crushed. As a result, fired powder is produced from the fired product.

The crushing process may be performed multiple times. For example, in the case of sequentially performing the first firing stage and the second firing stage, the first crushing process is performed after the first firing stage, and then the second firing stage is performed. You may perform a 2nd crushing process after implementation.

[B-2] Humidification process (ST20)
Next, in the humidification process (ST20), the fired powder prepared in the preparation process (ST10) is subjected to a humidification process.

In the humidification step (ST20), it is preferable to perform the humidification process in an atmosphere with a dew point of 50-90°C. In carrying out the humidification process, if the dew point is equal to or higher than the above lower limit, sufficient humidification process can be carried out. In addition, when the dew point is below the above upper limit, the amount of water that comes into contact with the CAM is small, and it is difficult to generate large amounts of lithium hydroxide or lithium carbonate as a residue when Li is extracted from the inside of the CAM. , gas generation in lithium secondary batteries can be sufficiently suppressed.

From this point of view, the dew point of the humidification treatment is more preferably 60°C or higher, and particularly preferably 80°C or lower. The dew point range of the humidification treatment is 60-90°C, 50-80°C, and 60-80°C.

Moreover, in the humidification process (ST20), it is preferable to perform the humidification process in an atmosphere where the CO ₂ concentration is 200 ppm or less. Moreover, in the humidification process, when the CO ₂ concentration is below the above upper limit value, the amount of lithium carbonate in the CAM is difficult to increase.

From such a viewpoint, the CO ₂ concentration in the humidification treatment is more preferably 100 ppm or less, particularly preferably 50 ppm or less.

In the humidification step (ST20), the humidification process is preferably performed in an atmosphere with a temperature of 80-400°C.
In the humidification process, when the temperature is equal to or higher than the above lower limit, the moisture that has come into contact with the CAM evaporates appropriately, and the problem of clumping during the humidification process is less likely to occur. Moreover, when the temperature is below the above upper limit value, it is possible to prevent the CAM from being re-sintered and the crystallite diameter from increasing excessively. As a result, it is possible to prevent the diffusion resistance of lithium ions within the crystal structure from increasing and to suppress deterioration of rate characteristics.

From this point of view, the temperature of the humidification treatment is more preferably 90°C or higher, particularly preferably 100°C or higher, and even more preferably 300°C or lower. The temperature range for the humidification treatment includes 80-300°C, 90-400°C, 100-400°C, and 100-300°C.

In the humidification step (ST20), the treatment time is preferably 0.1 to 5 hours. In the humidification process, if the process time is equal to or longer than the above lower limit, sufficient humidification process can be performed. In addition, if the processing time is below the above upper limit, the amount of water that comes into contact with the CAM is small, and it is difficult to generate a large amount of lithium hydroxide or lithium carbonate as a residue when Li is extracted from the inside of the CAM. Therefore, gas generation in the lithium secondary battery can be sufficiently suppressed.

From this point of view, the humidification treatment time is more preferably 0.2-2.5 hours, particularly preferably 0.3-2 hours.

[B-3] Drying process (ST30)
In the drying step (ST30), a CAM is produced by drying the fired powder that has been humidified in the humidifying step (ST20).

In the drying step (ST30), it is preferable to perform the drying process in an atmosphere with a temperature of 100 to 400°C. The temperature of the drying process is preferably at least the lower limit of the above range in order to prevent the charging capacity of the lithium secondary battery from decreasing due to moisture remaining in the CAM before the drying process. Therefore, the lower limit of the temperature of the drying treatment is more preferably 110°C, particularly preferably 120°C. Further, the temperature of the drying treatment is preferably at most the upper limit of the above range in order to prevent the rate characteristics from deteriorating due to re-sintering of the CAM. Therefore, the upper limit of the temperature of the drying treatment is more preferably 350°C, particularly preferably 300°C. The temperature range for the drying treatment includes 100-350°C, 110-350°C, and 120-300°C.

Note that drying is performed by, for example, reduced pressure drying, vacuum drying, air blowing, heating, or a combination thereof. Reduced pressure drying and vacuum drying are carried out, for example, at 100-200° C. under a pressure of 0.3 atmospheres or less. Drying by air blowing is performed using, for example, a hot air dryer.

In the drying step (ST30), the treatment time is preferably 0.1 hour or more. In the drying treatment, if the treatment time is equal to or longer than the above lower limit, the drying treatment can be sufficiently carried out.

From this point of view, the processing time of the drying treatment is more preferably 0.5 hours or more, and particularly preferably 1.0 hours or more.

Further, in the drying step (ST30), it is preferable to perform the drying process in an atmosphere where the CO ₂ concentration is 200 ppm or less. Further, in the drying process, when the CO ₂ concentration is below the above upper limit value, the increase in lithium carbonate in the CAM can be suppressed, and the generation of gas in the lithium secondary battery can be sufficiently suppressed.

From such a viewpoint, the CO ₂ concentration in the drying treatment is more preferably 100 ppm or less, particularly preferably 50 ppm or less.

The CAM can be manufactured by adjusting the processing conditions in the humidification step (ST20) and the drying step (ST30).

[C] Lithium Secondary Battery An example of a lithium secondary battery positive electrode having the CAM of this embodiment and a lithium secondary battery including the lithium secondary battery positive electrode will be described. Hereinafter, the positive electrode for a lithium secondary battery may be referred to as a positive electrode.

An example of a suitable lithium secondary battery in which LiMO manufactured by the manufacturing method of the present embodiment is used as a CAM includes a positive electrode and a negative electrode, a separator sandwiched between the positive electrode and the negative electrode, and a separator between the positive electrode and the negative electrode. It has an electrolyte placed therein.

FIG. 4 is a schematic diagram showing an example of a lithium secondary battery. For example, the cylindrical lithium secondary battery 10 is manufactured as follows.

First, as shown in the partially enlarged view of FIG. 4, a pair of band-shaped separators 1, a band-shaped positive electrode 2 with a positive electrode lead 21 installed at one end, and a band-shaped negative electrode 3 with a negative electrode lead 31 installed at one end. and prepare. Then, the electrode group 4 is produced by winding a laminate in which the separator 1, the positive electrode 2, the separator 1, and the negative electrode 3 are laminated in this order.

As an example, the positive electrode 2 includes a positive electrode active material layer 2a containing CAM, and a positive electrode current collector 2b on which the positive electrode active material layer 2a is formed over one surface. Such a positive electrode 2 can be manufactured by first preparing a positive electrode mixture containing CAM, a conductive material, and a binder, and then supporting the positive electrode mixture on one surface of the positive electrode current collector 2b to form the positive electrode active material layer 2a. .

Examples of the negative electrode 3 include an electrode in which a negative electrode mixture containing a negative electrode active material (not shown) is supported on a negative electrode current collector, and an electrode made of a negative electrode active material alone; It can be manufactured by

Next, after the electrode group 4 and the insulator (not shown) are housed in the battery can 5, the bottom of the battery can 5 is sealed. Then, by impregnating the electrode group 4 with the electrolytic solution 6 in the battery can 5, an electrolyte (not shown) is interposed between the positive electrode 2 and the negative electrode 3. Thereafter, the top of the battery can 5 is sealed with the top insulator 7 and the sealing body 8. Thereby, the lithium secondary battery 10 is completed.

The shape of the electrode group 4 is a columnar shape in which the cross-sectional shape when the electrode group 4 is cut in a direction perpendicular to the winding axis is, for example, a circle, an ellipse, a rectangle, or a rectangle with rounded corners. The shape of

Further, as the shape of the lithium secondary battery having such an electrode group 4, a shape defined by IEC60086, which is a standard established by the International Electrotechnical Commission (IEC), or JIS C 8500 can be adopted. For example, the shape may be cylindrical or square.

Furthermore, the lithium secondary battery is not limited to the above-mentioned wound type configuration, but may have a laminated type configuration in which a laminated structure of a positive electrode, a separator, a negative electrode, and a separator are repeatedly stacked. Examples of stacked lithium secondary batteries include so-called coin-type batteries, button-type batteries, and paper-type (or sheet-type) batteries.

For the positive electrode, separator, negative electrode, and electrolyte that constitute the lithium secondary battery, for example, the configurations, materials, and manufacturing methods described in [0113] to [0140] of WO2022/113904A1 can be used.

[D] All-solid-state lithium secondary battery An all-solid-state lithium secondary battery will be described as an example of a lithium secondary battery including a positive electrode for a lithium secondary battery formed using the CAM of this embodiment.

FIG. 5 is a schematic diagram showing an example of an all-solid-state lithium secondary battery. As shown in FIG. 5, the all-solid-state lithium secondary battery 1000 includes a laminate 100 having a positive electrode 110, a negative electrode 120, and a solid electrolyte layer 130, and an exterior body 200 that houses the laminate 100. The all-solid-state lithium secondary battery 1000 may have a bipolar structure in which a CAM and a negative electrode active material are arranged on both sides of a current collector. A specific example of the bipolar structure is, for example, the structure described in JP-A-2004-95400.

The positive electrode 110 has a positive electrode active material layer 111 and a positive electrode current collector 112. The positive electrode active material layer 111 includes the above-mentioned CAM and solid electrolyte. Further, the positive electrode active material layer 111 may contain a conductive material and a binder.

The negative electrode 120 has a negative electrode active material layer 121 and a negative electrode current collector 122. The negative electrode active material layer 121 includes a negative electrode active material. Further, the negative electrode active material layer 121 may include a solid electrolyte and a conductive material.

The laminate 100 may have 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. In addition, the all-solid-state lithium secondary battery 1000 may include a separator between the positive electrode 110 and the negative electrode 120.

The all-solid-state lithium secondary battery 1000 further includes an insulator (not shown) that insulates the stacked body 100 and the exterior body 200, and a sealing body (not shown) that seals the opening 200a of the exterior body 200.

The exterior body 200 is a container made of a highly corrosion-resistant metal material such as aluminum, stainless steel, or nickel-plated steel. Further, the exterior body 200 may be a container made of a bag-shaped laminated film that has been subjected to anti-corrosion treatment on at least one surface.

Examples of the shape of the all-solid-state lithium secondary battery 1000 include a coin shape, a button shape, a paper shape (or sheet shape), a cylindrical shape, a square shape, and a laminate shape (pouch shape).

The all-solid-state lithium secondary battery 1000 has, for example, one stacked body 100, but is not limited to this. The all-solid-state lithium secondary battery 1000 may have a configuration in which the laminate 100 is used as a unit cell, and a plurality of unit cells (the laminate 100) are sealed inside an exterior body 200.

For the all-solid lithium secondary battery, for example, the configurations, materials, and manufacturing methods described in [0151] to [0181] of WO2022/113904A1 can be used.

The present invention has the following aspects.
[21]
LiMO with a layered structure containing Li element, Ni element, and the element M;
A CAM comprising: a lithium compound containing lithium hydroxide and lithium carbonate;
The Va _0.5 , the Va _0.9 , and the Vd _0.5 satisfy the relationship shown in the following (Formula A'),
The Sm satisfies the relationship shown in the following (Formula B'), and
A CAM in which the W1 and the W2 satisfy the relationship shown in the following (Formula C1').
0<(Vd _0.5 - Va _0.5 )/Va _0.9 ≦0.85 (Formula A')
0.2m ² /g≦Sm≦0.8m ² /g (Formula B')
0≦W2/W1≦1.00...(Formula C1')
[22]
The CAM according to [21], wherein the LiMO is represented by the above (compositional formula I).
[23]
The CAM according to [21] or [22], wherein the Sm satisfies the relationship shown in formula (B1) below.
0.2m ² /g≦Sm≦0.7m ² /g (Formula B1)
[24]
The CAM according to any one of [21] to [23], wherein W2 satisfies the relationship shown in the following formula (D1').
0 mass%≦W2≦0.60 mass%...(formula D1')
[25]
The CAM according to any one of [21] to [24], wherein W3 satisfies the relationship shown in formula (E1') below.
0 mass% or more ≦W3≦0.40 mass% ... (Formula E1')
[26]
The CAM according to any one of [21] to [25], wherein the crystal strain is 0.08° or less.
[27]
The CAM according to any one of [21] to [26], wherein the average pore diameter is 10 to 100 nm.
[28]
The CAM according to any one of [21] to [27], wherein the pore volume is 0.001-0.010 cm ³ /g.
[29]
The CAM according to any one of [21] to [28], wherein the _D50 is 8-20 μm.
[30]
A positive electrode for a lithium secondary battery, comprising the CAM according to any one of [21] to [29].
[31]
A lithium secondary battery, comprising the positive electrode for a lithium secondary battery according to [30].
[32]
A method for manufacturing a CAM, the method comprising:
A preparation step of preparing a fired powder of MCC, which is a precursor of LiMO, and a lithium compound;
a humidification step of performing a humidification treatment on the baked powder prepared in the preparation step;
a drying step of producing the CAM by performing a drying treatment on the fired powder that has been subjected to the humidification treatment in the humidification step,
In the humidification process, the humidification process is performed in an atmosphere with a dew point of 50-90°C and a CO ₂ concentration of 50 ppm or less.
[33]
The method for manufacturing a CAM according to [32], wherein in the humidification process, the humidification process is performed in an atmosphere having a temperature of 90 to 400°C.
[34]
The method for producing a CAM according to [32] or [33], wherein in the drying step, the drying process is performed in an atmosphere at a temperature of 100 to 350°C.

Examples and comparative examples will be described below using Table 1. In Table 1, (Example 1) to (Example 3) correspond to Examples, and (Example C1) to (Example C3) correspond to Comparative Examples.

In Table 1, "humidification processing conditions" are the conditions when the humidification processing was performed in the humidification process (ST20), and "drying processing conditions" are the conditions when the drying processing was performed in the drying process (ST30). be.

[1] Preparation of CAM sample The procedure for preparing the CAM sample according to each example will be explained in order.

(Example 1)
In (Example 1), first, a powder of nickel cobalt aluminum metal composite oxide was produced as MCC, which is a precursor of LiMO.

First, water was put into a reaction tank equipped with a stirrer and an overflow pipe, and then an aqueous sodium hydroxide solution was added into the reaction tank. At this time, the temperature of the solution was maintained at 50° C. in the reaction tank. Then, a mixed solution was prepared by mixing a nickel sulfate aqueous solution, a cobalt sulfate aqueous solution, and an aluminum sulfate aqueous solution at a ratio in which the molar ratio of Ni, Co, and Al was 88:9:3. In addition, an ammonium sulfate aqueous solution was prepared as a complexing agent.

Then, the above mixed solution and an aqueous ammonium sulfate solution were continuously added into the reaction tank while stirring. At this time, an aqueous sodium hydroxide solution was added dropwise so that the pH of the mixed solution became 11.6 (liquid temperature at the time of measurement: 40° C.) in the reaction tank. This gave a reaction precipitate.

Thereafter, the reaction precipitate was washed with water, isolated by dehydration using a centrifuge, and dried at 105°C to obtain a metal composite hydroxide.

Then, the metal composite hydroxide was heated in the air at a temperature of 650° C. for 5 hours, and then cooled to room temperature. As a result, MCC, which is a nickel cobalt aluminum metal composite oxide, was obtained.

Next, lithium hydroxide monohydrate powder prepared as a lithium compound and MCC were mixed. Here, the value obtained by dividing the molar amount of Li element [Li] by the sum of the molar amount of Ni element [Ni], the molar amount of Co element [Co], and the molar amount of Al element [Al] is 1. Mixing was performed so that the ratio was .06 (that is, [Li]/([Ni]+[Co]+[Al])=1.06).

Next, the mixture of MCC and lithium hydroxide monohydrate was fired. The firing was carried out at a temperature of 740° C. for 5 hours in an oxygen atmosphere.

Next, the fired product obtained by the above firing was crushed using a stone mill crusher to obtain fired powder (preparation step (ST10) in FIG. 3).

Next, the above baked powder was subjected to humidification treatment (humidification step (ST20) in FIG. 3).

The humidification process was performed under the humidification process conditions shown in Table 1. Specifically, 150 g of fired powder was subjected to humidification treatment under the conditions that the treatment temperature was 300° C. and the treatment time was 1 hour. At this time, air was circulated so that the dew point was 60° C. and the CO ₂ concentration was less than 1 ppm.

Next, the fired powder subjected to the humidification treatment was subjected to a drying treatment (drying step (ST30) in FIG. 3).

The drying process was performed under the drying process conditions shown in Table 1. Specifically, the drying process was performed at a process temperature of 300° C. and a process time of 1 hour. At this time, air was circulated so that the dew point was −30° C. or less and the CO ₂ concentration was less than 1 ppm. As a result, the CAM sample in (Example 1) was completed.

(Example 2), (Example 3)
In (Example 2) and (Example 3), as shown in Table 1, the humidification process was performed under different processing times from those in (Example 1). Specifically, the processing time of (Example 2) is 0.3 hours, and the processing time of (Example 3) is 2 hours. Except for this point, in (Example 2) and (Example 3), the CAM samples were completed as in (Example 1).

(Example C1)
In (Example C1), as shown in Table 1, unlike (Example 1), etc., humidification treatment and drying treatment were not performed. That is, in (Example C1), the fired powder obtained before performing the humidification process in (Example 1) was used as a CAM sample.

(Example C2)
In (Example C2), as shown in Table 1, humidification treatment was not carried out similarly to (Example C1). In (Example C2), the baked powder obtained before the humidification process in (Example 1) was washed with water, and after the washing process, a drying process was performed.

In (Example C2), the water washing treatment and drying treatment were carried out under the following conditions.
[Water washing treatment conditions]
-Water washing treatment was carried out by dispersing 50 g of baked powder in 50 g of pure water and stirring for 20 minutes. The baked powder after washing with water was recovered by vacuum filtration.
[Drying processing conditions]
- Drying treatment was carried out by drying the baked powder after washing with water under reduced pressure at 120° C. for 10 hours.

As described above, in (Example C2), a CAM sample was completed in the same manner as in (Example 1), except that the humidification process was not performed and the water washing process and drying process were performed sequentially.

(Example C3)
In (Example C3), as shown in Table 1, humidification treatment and drying treatment were performed under different conditions from (Example 1).

Specifically, in (Example C3), the humidification process was performed in the same manner as in (Example 1), except that the atmospheric gas was air with a CO ₂ concentration of 400 ppm, as shown in the humidification process conditions in Table 1. carried out.

In (Example C3), the drying process was carried out in the same manner as in (Example 1), except that the atmospheric gas was air with a CO ₂ concentration of 400 ppm, as shown in the drying process conditions in Table 1.

Thus, in (Example C3), a CAM sample was completed in the same manner as in (Example 1) except that the humidification treatment conditions were different from those in (Example 1).

[2] Physical property evaluation As shown in Table 1, physical property evaluation corresponding to (requirement 1) to (requirement 3) described above was performed for the CAM samples prepared for each example as described above.

[2-1] Water retention parameter [=(Vd _0.5 - Va _0.5 )/Va _0.9 ]
Specifically, as shown in Table 1, the water retention parameter [=(Vd _0.5 - Va _0.5 )/Va _0.9 ] was determined for each example as a physical property evaluation corresponding to (requirement 1). Ta.

The water retention parameter [=(Vd _0.5 - Va _0.5 )/Va _0.9 ] is determined by water vapor adsorption using the water vapor adsorption method for each sample as explained above (measurement of water retention parameter). It was determined by measuring the amount and obtaining an adsorption isotherm and a desorption isotherm from the results.

FIG. 6 is a diagram showing adsorption isotherms and desorption isotherms used in determining water retention parameters for (Example 1) and (Example C1). In FIG. 6, the horizontal axis is the relative pressure p/p ₀ , and the vertical axis is the water vapor adsorption amount V (cm ³ (STP)/g). In FIG. 6, as in FIG. 2, the adsorption isotherm is shown by a solid line, and the desorption isotherm is shown by a broken line.

In (Example 1) and (Example C1), water retention parameters were determined using the adsorption isotherm and desorption isotherm shown in FIG. Although illustration of other examples is omitted, water retention parameters were similarly determined using adsorption isotherms and desorption isotherms.

[2-2] BET specific surface area Sm
As shown in Table 1, the BET specific surface area Sm was determined for each example as a physical property evaluation corresponding to the above-mentioned (requirement 2).

The measurement of Sm was carried out by the nitrogen adsorption method using nitrogen gas as the adsorption gas, as explained above (Measurement of Sm).

[2-3] W2/W1, W3
As shown in Table 1, as a physical property evaluation corresponding to the above-mentioned (requirement 3), the value (W2/W1) and W3, which are obtained by dividing the mass proportion W2 of lithium carbonate by the mass proportion W1 of lithium hydroxide, and W3 are calculated for each example. I asked for it.

W1, W2, and W3 were measured by the method described above (neutralization titration method).

Note that Table 1 also lists the results for W1 and W2. Table 1 also shows the results of W3. Furthermore, in Table 1, the values of x, y, and m in (compositional formula I) of LiMO (=Li[Li _m (Ni _(1-x-y) Co _x M1 _y ) _1-m ]O ₂ ) It shows. In addition, the results of determining crystal strain, average pore diameter, pore volume, and _D50 for CAM are shown. These compositions and physical properties were measured by the methods described above (Measurement of composition) and [A-3-4]. Further, as a result of powder X-ray diffraction measurement, the LiMO in the CAM obtained in (Example 1) to (Example 3) and (Example C1) to (Example C3) had a layered structure.

[3] Battery Evaluation As described above, for the CAM samples produced in each example, battery evaluation was performed as shown in Table 1.

When performing battery evaluation, a positive electrode for a lithium secondary battery was produced from the CAM sample of each example, and then a lithium secondary battery was produced using the produced positive electrode for a lithium secondary battery. Thereafter, as shown in Table 1, the float charge and rate characteristics of the manufactured lithium secondary battery were measured.

[3-1] Production of positive electrode for lithium secondary battery When producing a positive electrode for lithium secondary battery, first, a paste-like positive electrode mixture was prepared. The positive electrode mixture was prepared by kneading the mixture of the CAM produced in each example, the conductive material, and the binder. Here, acetylene black was used as the conductive material, and PVdF was used as the binder. Then, each material was mixed in the following proportions. When preparing the positive electrode mixture, N-methyl-2-pyrrolidone was used as an organic solvent.

・CAM: 92 parts by mass ・Conductive material: 5 parts by mass ・Binder: 3 parts by mass

Then, the paste-like positive electrode mixture prepared as described above was applied to a current collector (aluminum foil having a thickness of 40 μm). Thereafter, the current collector coated with the positive electrode mixture was vacuum-dried for 8 hours in an atmosphere at a temperature of 150° C., thereby completing a positive electrode for a lithium secondary battery. Here, the electrode area of the positive electrode for a lithium secondary battery was 1.65 cm ² .

[3-2] Fabrication of lithium secondary battery When fabricating a lithium secondary battery, first, the positive electrode for lithium secondary battery fabricated as described above is attached to parts for coin-type battery R2032 (manufactured by Hosen Co., Ltd.). ) was placed on the top of the lower lid. When installing it on the lower lid, the aluminum foil surface of the positive electrode for a lithium secondary battery was directed downward. Then, a laminated film separator was installed on the upper surface of the lower lid on which the positive electrode for a lithium secondary battery was installed. Here, a laminated film separator having a thickness of 16 μm and having a heat-resistant porous layer laminated on a polyethylene porous film was used.

Next, 300 μl of electrolyte was injected into the inside of the above part. Here, as the electrolyte, a solution in which LiPF ₆ was dissolved in a mixed solution of various substances in the proportions shown below was used. The electrolytic solution was prepared so that the concentration of LiPF ₆ was 1 mol/l.

・Ethylene carbonate: 30 parts by volume ・Dimethyl carbonate: 35 parts by volume ・Ethyl methyl carbonate: 35 parts by volume

Next, a negative electrode was placed above the separator. Here, metallic lithium was used as the negative electrode. Then, the upper cover was installed via the gasket, and the upper cover was caulked using a caulking machine. As a result, a coin-shaped half cell R2032 was produced as a lithium secondary battery.

[3-3] Float test As an index for evaluating the amount of gas generated within the battery, the amount of float electricity was measured. The float charge is the charge observed when an irreversible reaction occurs with the electrolyte at the particle interface. The larger the value of the float electrical quantity observed, the greater the amount of gas generated.

Specifically, the float electrical quantity was measured under the following conditions.
・Test temperature: 60℃
・Maximum charging voltage: 4.3V, charging current: 0.2CA
・Constant voltage holding time 60 hours

In the float test, the integrated amount of electricity during the constant voltage holding time after shifting to the 4.3V constant voltage mode was calculated as the float amount of electricity (mAh/g). In the evaluation of the float test, when the float electrical quantity was 6.0 mAh/g or less, it was determined that the float electrical quantity was small.

[3-4] Rate characteristics [(1C/0.2C) discharge capacity]
The rate characteristic is the ratio (%) of the discharge capacity when the charge/discharge rate is 1C to the discharge capacity when the charge/discharge rate is 0.2C. Regarding the evaluation of rate characteristics, when the rate characteristics were 95% or more, it was determined that the rate characteristics were high.

Specifically, the rate characteristics were measured under the following conditions.
(Rate characteristic measurement conditions)
(0.2C discharge capacity)
・Test temperature: 25℃
・Maximum charging voltage: 4.3V, charging current: 0.2CA, constant current constant voltage charging, ends at 0.05CA current value ・Minimum discharging voltage: 2.5V, discharging current: 0.2CA, constant current discharge ( 1C discharge capacity)
・Processing temperature: 25℃
・Maximum charging voltage: 4.3V, charging current: 1CA, constant current constant voltage charging, ends at 0.05CA current value ・Minimum discharging voltage: 2.5V, discharging current: 1CA, constant current discharge

[4] Summary The "physical property evaluation" and "battery evaluation" of each example will be explained.

[4-1] Regarding the results of (Example 1) to (Example 3) (Example 1) to (Example 3) are as shown in the "Physical property evaluation" column of Table 1. It satisfies all of the relationships of formula A), the above (formula B) defined as (requirement 2), and the above (formula C) defined as (requirement 3).

Therefore, as shown in the "Battery evaluation" column of Table 1, (Example 1) to (Example 3) satisfy the relationship between (Formula A) and (Formula C) specified as (Requirement 1), so the float electric Since the value of the quantity is small and the relationship of (Formula B) defined as (Requirement 2) is satisfied, the value of the rate characteristic is high.

[4-2] Regarding the results of (Example C1) On the other hand, as shown in the "Physical property evaluation" column of Table 1, (Example C1) shows that the relationship of (formula A) specified as (requirement 1) is Not satisfied. The value calculated by (Formula A) is a water retention parameter, and the water retention parameter of (Example C1) is higher than the water retention parameters of (Example 1) to (Example 3). Therefore, (Example C1) retains water more easily than (Example 1) to (Example 3), so the active sites where side reactions are likely to occur in lithium secondary batteries are more likely to occur than (Example 1) to (Example 3). more than As a result, in (Example C1), as shown in the "Battery Evaluation" column of Table 1, the float electricity amount was large.

In (Example C1), unlike (Example 1) to (Example 3), humidification processing and drying processing were not performed. The humidification process inactivates active sites that are likely to cause side reactions in a lithium secondary battery through contact with water. From this, if humidification treatment is not performed as in (Example C1), it is not possible to inactivate the active sites that tend to cause side reactions in lithium secondary batteries, and the relationship in (Formula A) is It is possible that you will not be satisfied.

[4-3] Regarding the results of (Example C2) As can be seen from the results shown in the "Physical property evaluation" column of Table 1, (Example C2) satisfies the relationship of (Formula B) specified as (Requirement 2). do not have. (Formula B) specifies Sm, and Sm in (Example C2) is higher than Sm in (Example 1) to (Example 3). Therefore, in (Example C2), side reactions occurring on the surface of the CAM during charging and discharging of a lithium secondary battery cannot be suppressed more than in (Example 1) to (Example 3). As a result, as shown in the "Battery Evaluation" column of Table 1, (Example C2) has a low rate characteristic value.

In (Example C2), unlike (Example 1) to (Example 3), a water washing process is performed instead of a humidification process. Similar to the humidification process, the water washing process inactivates active sites that are likely to cause side reactions in a lithium secondary battery through contact with water. However, when performing the water washing treatment, the lithium compound remaining at the grain boundaries of LiMO and filling the pores is excessively removed. For this reason, if the water washing process is performed as in (Example C2), it will be difficult to satisfy the relationship (Equation B). It is thought that many reactions occur and the value of the rate characteristic becomes low.

[4-4] About the results of (Example C3) As can be seen from the results shown in the "Physical property evaluation" column of Table 1, (Example C3) does not satisfy the relationship of (formula C) specified as (requirement 3). . (Formula C) defines W2/W1, and the value of W2/W1 in (Example C3) is larger than in (Example 1) to (Example 3). Therefore, (Example C3) is unable to suppress gas generation in the lithium secondary battery more than (Example 1) to (Example 3). As a result, in (Example C3), as shown in the "Battery Evaluation" column of Table 1, the float electricity amount was large.

In (Example C3), humidification processing is performed similarly to (Example 1) to (Example 3). However, in (Example 1) to (Example 3), the humidification process is performed in an atmosphere where the CO ₂ concentration is 200 ppm or less (less than 1 ppm), whereas in (Example C3), the CO ₂ concentration is Humidification processing is performed in an atmosphere exceeding 200 ppm (400 ppm). As a result, in (Example C3), W2 is particularly large among the lithium compounds remaining on the surface of the CAM, and it is considered that the relationship of (Formula C) is not satisfied.

DESCRIPTION OF SYMBOLS 1... Separator, 2... Positive electrode, 3... Negative electrode, 4... Electrode group, 5... Battery can, 6... Electrolyte, 7... Top insulator, 8... Sealing body, 10... Lithium secondary battery, 21... Positive electrode lead, 31 ...Negative electrode lead, 51... Lithium metal composite oxide, 61... Lithium compound, 71... Active point, 100... Laminate, 110... Positive electrode, 111... Positive electrode active material layer for lithium secondary battery, 112... Positive electrode current collector, 113... External terminal, 120... Negative electrode, 121... Negative electrode active material layer, 122... Negative electrode current collector, 123... External terminal, 130... Solid electrolyte layer, 200... Exterior body, 200a... Opening, 1000... All solid lithium secondary next battery

Claims

A lithium metal composite oxide with a layered structure containing Li element, Ni element, and element M;
A positive electrode active material for a lithium secondary battery, comprising: a lithium compound containing lithium hydroxide and lithium carbonate;
The element M is at least one selected from the group consisting of Co, Mn, Fe, Cu, Ti, Mg, Ca, Ba, Al, Zn, Sn, Zr, Nb, B, Si, S, and P. is an element,
In the adsorption isotherm of the water vapor adsorption method, the water vapor adsorption amount Va 0.5 when the relative pressure p/p 0 between the water vapor pressure p and the saturated vapor pressure p 0 is 0.5, in the adsorption isotherm of the water vapor adsorption method Water vapor adsorption amount Va 0.9 when the relative pressure p/p 0 is 0.9, and water vapor when the relative pressure p/p 0 is 0.5 in the desorption isotherm of the water vapor adsorption method. The adsorption amount Vd 0.5 satisfies the relationship shown in the following (formula A),
The BET specific surface area Sm measured by the nitrogen adsorption method satisfies the relationship shown in the following (formula B), and
The mass proportion W1 of the lithium hydroxide and the mass proportion W2 of the lithium carbonate satisfy the relationship shown in the following (Formula C),
Positive electrode active material for lithium secondary batteries.
(Vd 0.5 - Va 0.5 )/Va 0.9 ≦0.90 (Formula A)
Sm≦0.8m 2 /g (Formula B)
W2/W1≦1.40 (Formula C)
The lithium metal composite oxide is
Represented by the following (compositional formula I),
The positive electrode active material for a lithium secondary battery according to claim 1.
Li[Li m (Ni (1-x-y) C x M1 y ) 1-m ] O 2 ... (compositional formula I)
(In (compositional formula I), M1 is at least one selected from the group consisting of Mn, Fe, Cu, Ti, Mg, Ca, Ba, Al, Zn, Nb, Sn, Zr, B, Si, S, and P. is one type of element, and m, x, and y have the relationships shown in -0.1≦m≦0.2, 0≦x≦0.5, 0<y≦0.7, and x+y<1. satisfied.)
The Sm satisfies the relationship shown in the following formula (B1),
The positive electrode active material for a lithium secondary battery according to claim 1 or 2.
0.2m 2 /g≦Sm≦0.7m 2 /g (Formula B1)
The W2 satisfies the relationship shown in the following formula (D),
The positive electrode active material for a lithium secondary battery according to claim 1 or 2.
W2≦0.70% by mass (Formula D)
The eluted lithium amount W3 of the positive electrode active material for lithium secondary batteries, measured by neutralization titration method, satisfies the relationship shown in the following formula (E),
The positive electrode active material for a lithium secondary battery according to claim 1 or 2.
W3≦0.50% by mass (Formula E)
In the diffraction pattern of powder X-ray diffraction measured with CuKα rays, the crystal strain calculated from the diffraction pattern in which the diffraction angle 2θ is within the range of 10° or more and 90° or less is 0.10° or less.
The positive electrode active material for a lithium secondary battery according to claim 1 or 2.
The positive electrode active material for a lithium secondary battery according to claim 1 or 2, wherein the average pore diameter measured by a nitrogen adsorption method is 150 nm or less.
The pore volume measured by nitrogen adsorption method is 0.0005 cm 3 /g or more and 0.0150 cm 3 /g or less,
The positive electrode active material for a lithium secondary battery according to claim 1 or 2.
50% cumulative volume particle size D50 is 3 μm or more and 30 μm or less,
The positive electrode active material for a lithium secondary battery according to claim 1 or 2.
Comprising the positive electrode active material for a lithium secondary battery according to claim 1 or 2,
Positive electrode for lithium secondary batteries.
It has a positive electrode for a lithium secondary battery according to claim 10,
Lithium secondary battery.
A method for producing a positive electrode active material for a lithium secondary battery, the method comprising:
a preparation step of preparing a fired powder of a metal composite compound that is a precursor of a lithium metal composite oxide and a lithium compound;
a humidification step of performing a humidification treatment on the baked powder prepared in the preparation step;
a drying step of producing the positive electrode active material for a lithium secondary battery by performing a drying treatment on the fired powder subjected to the humidification treatment in the humidification step,
In the humidification step, the humidification process is performed in an atmosphere where the dew point is 50 ° C. or more and 90 ° C. or less and the CO 2 concentration is 200 ppm or less.
A method for producing a positive electrode active material for a lithium secondary battery.
In the humidification step, the humidification process is performed in an atmosphere with a temperature of 80° C. or higher and 400° C. or lower.
The method for producing a positive electrode active material for a lithium secondary battery according to claim 12.
In the drying step, the drying process is performed in an atmosphere with a temperature of 100° C. or higher and 400° C. or lower.
The method for producing a positive electrode active material for a lithium secondary battery according to claim 12 or 13.