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

Abstract

To provide a positive electrode active material for a lithium secondary battery which can attain a lithium secondary battery with a low resistance in a low charge state, a positive electrode for a lithium secondary battery including the positive electrode active material for a lithium secondary battery, and a lithium secondary battery.SOLUTION: The positive electrode active material for a lithium secondary battery contains Li, Mn, and Ni, and satisfies the following requirements (1) and (2): (1) the structure is a layered structure; and (2) I2 / I1 is 0.22 or more and 0.45 or less when P1 denotes a peak of 580-610 cm-1, P2 denotes a peak of 4215-455 cm-1, the peak intensity of P1 is denoted by I1, and the peak intensity of P2 is denoted by I2 in the Raman spectral analysis of an excitation wavelength 532nm.SELECTED DRAWING: None

Description

Technical Field

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

Background Art

[0002] The battery performance of a lithium secondary battery varies depending on its composition and crystal state. Therefore, research has been conducted on the physical properties of a positive electrode active material for a lithium secondary battery that can achieve a lithium secondary battery with better battery performance.

[0003] Patent Document 1 discloses an all-solid-state secondary battery including a positive electrode and a negative electrode, and a solid electrolyte disposed therebetween, wherein LiNi having a Raman scattering intensity ratio I / I of 2.81 ≦ I / I ≦ 6.35 at 638 cm and 660 cm is included in the positive electrode as a positive electrode active material. It is disclosed that the output is increased by using an all-solid-state secondary battery having such a configuration. -1 of Raman scattering intensity as I 1 and the Raman scattering intensity at 660 cm as I -1 When 2 the ratio I 1 / I 2 is 1 / I 2 ≦ 6.35 0.5 Mn 1.5 O 4

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] As the application fields of lithium secondary batteries progress, lithium secondary batteries are required to have low resistance in a low state of charge. The present invention has been made in view of the above circumstances, and an object thereof is to provide a positive electrode active material for a lithium secondary battery capable of achieving a lithium secondary battery having a low resistance in a low state of charge, a positive electrode for a lithium secondary battery including the positive electrode active material for a lithium secondary battery, and a lithium secondary battery.

Means for Solving the Problems

[0006] The present invention is as follows [1] to [9]. [1] A positive electrode active material for a lithium secondary battery, which contains Li, Mn, and Ni and satisfies the following requirements (1) and (2). (1) It has a layered structure. (2) In Raman spectroscopic analysis with an excitation wavelength of 532 nm, the peak at 580 to 610 cm -1 is defined as P1, the peak at 415 to 455 cm -1 is defined as P2, the peak intensity of the said P1 is I 1 , and the peak intensity of the said P2 is I 2 , when I 2 / I 1 is 0.22 or more and 0.45 or less. [2] The positive electrode active material for a lithium secondary battery according to [1], wherein when the full width at half maximum of the said P1 is F1 and the full width at half maximum of the said P2 is F2, F2 / F1 is 0.5 or more and 2.0 or less. [3] The positive electrode active material for a lithium secondary battery according to [1] or [2], which is represented by the following compositional formula (I). Li 1+a Ni x Mn y M b O 2 (I) [In the said compositional formula (I), 0 ≦ a ≦ 0.5, 0 < x < 1, 0 < y < 1, a + x + y + b = 1, and 0 ≦ b < 1 are satisfied, and M is at least one element selected from the group consisting of Co, W, Nb, Mo, Ta, P, B, Ti, Zr, and Al.] [4] The positive electrode active material for a lithium secondary battery according to any one of [1] to [3], wherein the BET specific surface area is 0.2 m 2 / g or more and 3 m 2 / g or less. [5] D which is the 50% cumulative volume particle size 50 is 2 μm or more and 30 μm or less, and the positive electrode active material for a lithium secondary battery according to any one of [1] to [4]. [6] In powder X-ray diffraction measurement using CuKα rays, the peak intensity X of the peak existing in the range of 2θ = 18.7 ± 1° 1 with respect to the peak intensity X of the peak existing in the range of 2θ = 20.7 ± 1° 2 is the ratio of X 2 / X 1 is 0.005 or more and 0.06 or less, and the positive electrode active material for a lithium secondary battery according to any one of [1] to [5]. [7] The I 1 is 200 cm -1 or more and 1000 cm -1 or less, and the positive electrode active material for a lithium secondary battery according to any one of [1] to [6], which is the highest among the peak intensities obtained within the range. [8] A positive electrode for a lithium secondary battery containing the positive electrode active material for a lithium secondary battery according to any one of [1] to [7]. [9] A lithium secondary battery containing the positive electrode for a lithium secondary battery according to [8].

Advantages of the Invention

[0007] According to the present invention, it is possible to provide a positive electrode active material for a lithium secondary battery capable of achieving a lithium secondary battery having a low resistance in a low state of charge, and a positive electrode for a lithium secondary battery and a lithium secondary battery containing the positive electrode active material for a lithium secondary battery.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Modes for Carrying Out the Invention

[0009] The definitions of the terms in this specification are as follows. A metal composite compound is hereinafter also referred to as "MCC". A cathode active material for lithium secondary batteries is hereinafter also referred to as "CAM". "Ni" indicates not a single nickel metal but the Ni element. The notations of other elements such as Co and Mn are the same. When a numerical range is described, for example, as "0.2 to 2 m 2 / g", it means a range from 0.2 m 2 / g to 2 m 2 / g, and means a numerical range including the lower limit value of 0.2 m 2 / g and the upper limit value of 2 m 2 / g. A lithium secondary battery means one in which an electrolyte (such as a non-aqueous electrolyte or a solid electrolyte) is disposed between a positive electrode and a negative electrode, and charging and discharging are performed by lithium ions moving between the positive electrode and the negative electrode through the electrolyte.

[0010] The measurement methods for each parameter of CAM in this specification are as follows.

[0011] (Raman spectroscopic parameters) The Raman spectroscopic parameters of CAM can be measured using a laser Raman microscope (for example, manufactured by Nanophoton Co., Ltd., RAMANtouch). As measurement conditions, an excitation wavelength of 532 nm, a slit width of 50 μm, and a diffraction grating of 600 gr / mm can be adopted. Based on the obtained Raman spectrum, by analysis using a mixed function of a Gaussian function and a Lorentz function (least squares method), peaks in the range of 580 to 610 cm -1 are identified as P1, and peaks in the range of 415 to 455 cm -1 are identified as P2, and the peak intensity I 1 and full width at half maximum F1 of P1, and the peak intensity I 2 and full width at half maximum F2 of P2 can be obtained.

[0012] (Composition) The composition of each element of the CAM can be measured by inductively coupled plasma optical emission spectrometry (ICP). For example, after dissolving the CAM in hydrochloric acid, the amount of each element can be measured using an inductively coupled plasma optical emission spectrometer (for example, SPS3000 manufactured by Shimadzu Nanotechnology Co., Ltd.).

[0013] (BET specific surface area) The BET specific surface area of the CAM (unit: m 2 / g) can be measured by the BET (Brunauer, Emmett, Teller) method. In the measurement of the BET specific surface area, nitrogen gas is used as the adsorption gas. For example, after drying 1 g of the CAM powder at 105 °C for 30 minutes in a nitrogen atmosphere, it can be measured using a BET specific surface area meter (for example, Macsorb (registered trademark) manufactured by Mountech Co., Ltd.).

[0014] (50% cumulative volume particle size D 50 ) The 50% cumulative volume particle size of the CAM (unit: μm, hereinafter sometimes referred to as "D 50 ") can be obtained from the particle size distribution of the CAM measured by the laser diffraction scattering method. Specifically, 0.1 g of the CAM powder is put into 50 ml of a 0.2 mass% sodium hexametaphosphate aqueous solution to obtain a dispersion in which the powder is dispersed. Next, the particle size distribution of the obtained dispersion is measured using a laser diffraction scattering particle size distribution measuring device (for example, Mastersizer 2000 manufactured by Malvern Instruments) to obtain a cumulative particle size distribution curve based on volume. In the obtained cumulative particle size distribution curve, the value of the particle diameter at 50% cumulative from the fine particle side is D 50 .

[0015] (XRD pattern, X 2 / X 1 measurement) The XRD pattern of CAM can be obtained by powder X-ray diffraction measurement. Specifically, using a powder X-ray diffractometer (for example, Ultima IV manufactured by Rigaku Corporation), fill the powder of CAM onto a dedicated substrate, and using a Cu-Kα radiation source, perform measurement under the conditions of diffraction angle 2θ = 10° to 90°, sampling width 0.02°, and scan speed 4° / min to obtain the XRD pattern. Then, using the integrated powder X-ray analysis software JADE, calculate the peak intensity X of the peak existing in the range of 2θ = 18.7 ± 1° in the said XRD pattern 1 and the peak intensity X of the peak existing in the range of 2θ = 20.7 ± 1° 2 . At this time, remove the background by setting the average value of the peak intensity at 2θ = 10.25° ± 0.25° to 0. The value obtained by dividing X 2 by X 1 is X 2 / X 1 .

[0016] (Resistance in the low state of charge) Fabricate a lithium secondary battery using CAM and measure the resistance in the low state of charge.

[0017] <Fabrication of the positive electrode for the lithium secondary battery> Add CAM, a conductive material (acetylene black), and a binder (PVdF) in a composition of CAM:conductive material:binder = 92:5:3 (mass ratio) and knead to prepare a paste-like positive electrode mixture. When preparing the positive electrode mixture, use N-methyl-2-pyrrolidone as the organic solvent.

[0018] Apply the obtained positive electrode mixture onto an Al foil with a thickness of 40 μm serving as a current collector and perform vacuum drying at 150°C for 8 hours to obtain a positive electrode for the lithium secondary battery. The electrode area of this positive electrode for the lithium secondary battery is 1.65 cm 2 .

[0019] <Fabrication of the lithium secondary battery> Perform the following operations inside a glove box under an argon atmosphere. Place the above-described positive electrode for a lithium secondary battery with the aluminum foil side facing down on the lower lid of a coin-type battery R2032 part (manufactured by Takizawa Co., Ltd.), and place a laminated film separator (16 μm thick) in which a heat-resistant porous layer is laminated on a porous polyethylene film thereon. Inject 300 μl of an electrolytic solution here. The electrolytic solution is a liquid in which LiPF 6 is dissolved to a concentration of 1 mol / l in a mixed solution of ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate at a volume ratio of 30:35:35. Next, use metallic lithium as the negative electrode, place it on the upper side of the separator, cover it with an upper lid through a gasket, and crimp it with a crimping machine to fabricate a lithium secondary battery (coin-type half cell R2032).

[0020] The resistance in the low state of charge is defined as the value measured under the following measurement conditions using the fabricated lithium secondary battery. In this specification, the low state of charge is defined as a charge rate of 15%.

[0021] ·Measurement conditions Counter electrode (negative electrode): Lithium electrode foil Test temperature: 25°C Pre-measurement treatment: Set the discharge capacity at 1C in the voltage range of an upper limit voltage of 4.5 V and a lower limit voltage of 2.5 V to 100%, charge to 4.5 V, and then perform constant current discharge at 1C so that the remaining capacity of the lithium secondary battery becomes 15%. Further, measure the open circuit voltage when no current is applied to the lithium secondary battery after the pre-measurement treatment. Measurement of resistance: Apply constant currents of 2 mA, 4 mA, 8 mA, and 16 mA to the lithium secondary battery after the pre-measurement treatment, measure the voltage value 10 seconds after the start of current application, and calculate the voltage drop ΔV with respect to the open circuit voltage. Calculate the resistance Rx of the lithium secondary battery from the linear function formula ΔV = Rx×ΔI of the voltage drop ΔV with respect to the current ΔI.

[0022] ≪Positive electrode active material for lithium secondary battery≫ CAM contains Li, Mn, and Ni. CAM satisfies the following requirements (1) and (2). (1) It has a layered structure. (2) In the Raman spectroscopic analysis with an excitation wavelength of 532 nm, the peak at 580 - 610 cm -1 is designated as P1, the peak at 415 - 455 cm -1 is designated as P2, the peak intensity of the said P1 is I 1 , and when the peak intensity of the said P2 is I 2 , I 2 / I 1 is 0.22 - 0.45.

[0023] <Requirement (1)> The crystal structure of CAM is a layered structure. The crystal structure of CAM is preferably a layered rock - salt type structure, and more preferably a hexagonal crystal structure or a monoclinic crystal structure.

[0024] The hexagonal crystal structure belongs to any one of the space groups selected from the group consisting of 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, P6mm, P6cc, 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.

[0025] Also, 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 belongs to any one space group selected from the group consisting of C2 / c.

[0026] Among these, in order to obtain a lithium secondary battery with low resistance in a low state of charge, the crystal structure of CAM is more preferably a hexagonal crystal structure belonging to the space group R-3m or a monoclinic crystal structure belonging to C2 / m.

[0027] (Confirmation of crystal structure) The crystal structure of CAM can be confirmed by a powder X-ray diffractometer (for example, UltimalV manufactured by Rigaku Corporation).

[0028] <Requirement (2)> CAM contains LiMeO 2 (Me is a metal element and includes Ni and Mn). In LiMeO 2 , Li 2 MnO 3 may be included as an impurity. According to the study by the present inventors, the resistance of Li 2 MnO 3 in a low state of charge was found to be higher than that of LiMeO 2 . Therefore, in CAM containing LiMeO 2 having a layered structure, reducing or eliminating the content of Li 2 MnO 3 is considered to be effective in reducing the resistance of the lithium secondary battery in a low state of charge.

[0029] P1 is a peak derived from the Mn-O bond of LiMeO 2 (Me is a metal element and includes Ni and Mn) contained in CAM, and I 1 is considered to represent the amount of the Mn-O bond. That is, I 1 is considered to substantially represent the amount of LiMnO 2 . P2 is Li contained in CAM2 MnO 3 is a peak derived from the Mn-O bond in the domain, and I 2 is considered to represent the amount of the Mn-O bond. That is, I 2 is substantially Li 2 MnO 3 is considered to represent the amount of the domain. That is, I 2 / I 1 is substantially the amount of LiMnO 2 in CAM relative to Li 2 MnO 3 is considered to be a parameter indicating the amount of the domain.

[0030] CAM contains LiMeO 2 as a main component and a trace amount of Li 2 MnO 3 domains. As described above, since the Li 2 MnO 3 domains tend to have a higher resistance in a lower state of charge than LiMeO 2 does, when the Li 2 MnO 3 domains are included, the contribution of the increase in resistance due to the physical properties of this Li 2 MnO 3 domains becomes large, and it is expected that the resistance in the lower state of charge will increase.

[0031] However, according to the study by the inventors of the present application, when the amount of Li 2 MnO 3 domains is optimized, it has been found that the resistance in the lower state of charge is lower than that of CAM consisting only of LiMeO 2 MnO 3 without the Li 2 domains. The effect of the decrease in resistance in this lower state of charge is considered to be achieved by the following mechanism.

[0032] Li 2 MnO 3 without the Li 2In the case of a CAM consisting only of [Li], the diffusion of lithium ions is considered to occur only in the two-dimensional direction within the layers of the layered structure. On the other hand, for a CAM having Li 2 MnO 3 domains, the diffusion of lithium ions is considered to occur not only in the two-dimensional direction within the layers of the layered structure but also in the three-dimensional direction between different layers where Li 2 MnO 3 domains exist. When the diffusion of lithium ions occurs in the three-dimensional direction between layers, it is considered that the migration path of lithium ions increases and the resistance in the low state of charge decreases.

[0033] On the other hand, as described above, since the Li 2 MnO 3 domains tend to have a higher resistance in the low state of charge than LiMeO 2 , if the amount of Li 2 MnO 3 domains is too large, the contribution of the increase in resistance due to the physical properties of the Li 2 MnO 3 domains becomes large, and it is considered that the resistance in the low state of charge increases. That is, the inventors of the present application have found that there is an optimal range for the amount of Li 2 MnO 3 domains contained in the CAM, and have found that this optimal range can be represented by a predetermined range of I 2 / I 1 .

[0034] I 2 / I 1 is preferably 0.23 or more, more preferably 0.24 or more. I 2 / I 1 is preferably 0.42 or less, more preferably 0.40 or less. I 2 / I 1 is preferably 0.23 to 0.42, more preferably 0.24 to 0.40. I 2 / I 1 is equal to or higher than the lower limit value of the above range, lithium ions existing in different layers 2MnO 3 It is considered that the resistance in the low state of charge is reduced by promoting the three-dimensional diffusion of lithium ions between domains (layers). I 2 / I 1 If is equal to or less than the upper limit value of the above range, LiMeO 2 has a higher resistance in the low state of charge than Li 2 MnO 3 The amount of the domain does not become too large, and the contribution of the increase in resistance due to the physical properties of the Li 2 MnO 3 domain becomes small, and it is considered that the increase in resistance in the low state of charge is suppressed.

[0035] I 1 is preferably the highest among the peak intensities obtained within the range of 200 to 1000 cm -1 . When I 1 is the highest, it means that the main crystal structure of CAM belongs to the hexagonal crystal structure assigned to the space group R-3m. Also, I 1 When is the highest, it means that the Mn-O bond in LiMeO 2 contributes to the stability of the structure. As a result, the increase in resistance in the low state of charge is likely to be suppressed.

[0036] When the full width at half maximum of P1 is F1 and the full width at half maximum of P2 is F2, F2 / F1 is preferably 0.5 or more, more preferably 0.8 or more, and even more preferably 1.0 or more. F2 / F1 is preferably 2.0 or less, more preferably 1.9 or less, even more preferably 1.8 or less, and particularly preferably 1.6 or less. F2 / F1 is preferably 0.5 to 2.0, more preferably 0.8 to 1.9, even more preferably 1.0 to 1.8, and particularly preferably 1.0 to 1.6. When F2 / F1 is equal to or greater than the lower limit value, Li present in different layers 2 MnO 3It is considered that the resistance in the low state of charge decreases due to the promotion of three-dimensional diffusion of lithium ions between domains (layers). When F2 / F1 is equal to or less than the above upper limit value, the resistance in a lower state of charge is higher than that of LiMeO 2 The amount of Li 2 MnO 3 domains does not increase too much, and the contribution of the increase in resistance due to the physical properties of the Li 2 MnO 3 domains becomes small, and it is considered that the increase in resistance in the low state of charge is suppressed.

[0037] F1 is preferably 20 cm -1 or more, more preferably 30 cm -1 or more, and even more preferably 40 cm -1 or more. F1 is preferably 80 cm -1 or less, more preferably 70 cm -1 or less, and even more preferably 60 cm -1 or less. F1 is preferably 20 to 80 cm -1 more preferably 30 to 70 cm -1 even more preferably 40 to 60 cm -1 or more. When F1 is equal to or greater than the above lower limit value, the size of LiMeO 2 is small, the lithium ion migration distance is short, and the resistance in the low state of charge is likely to decrease. When F1 is equal to or less than the above upper limit value, the bond strain is suppressed, lithium ions can easily move in the structure of CAM, and the resistance in the low state of charge is likely to decrease.

[0038] F2 is preferably 20 cm -1 or more, more preferably 30 cm -1 or more, and even more preferably 40 cm -1 or more. F2 is preferably 100 cm -1 or less, more preferably 90 cm -1 or less, and even more preferably 80 cm -1 or less. F2 is preferably 20 to 100 cm -1It is preferably 30 to 90 cm -1 It is more preferably 40 to 80 cm -1 It is even more preferably. When F2 is equal to or greater than the lower limit value, Li present in different layers 2 MnO 3 The three-dimensional diffusion of lithium ions between domains (interlayers) is promoted, so that the resistance in the low state of charge is likely to decrease. When F2 is equal to or less than the upper limit value, the resistance of Li 2 in a lower state of charge is higher than that of LiMeO 2 MnO 3 The amount of domains does not become too large, and the contribution of the increase in resistance due to the physical properties of the Li 2 MnO 3 domains is likely to be small. As a result, an increase in resistance in the low state of charge is likely to be suppressed.

[0039] In addition to the above requirements (1) and (2), it is preferable that the CAM satisfies the following physical properties.

[0040] The BET specific surface area of the CAM is preferably 0.2 m 2 / g or more, more preferably 0.4 m 2 / g or more, and even more preferably 0.5 m 2 / g or more. The BET specific surface area is preferably 3 m 2 / g or less, more preferably 2.8 m 2 / g or less, and even more preferably 2.4 m 2 / g or less. The BET specific surface area is preferably 0.2 to 3 m 2 / g, more preferably 0.4 to 2.8 m 2 / g, and even more preferably 0.5 to 2.4 m 2 / g. When the BET specific surface area is equal to or greater than the lower limit value, a reaction area where charge and discharge reactions occur can be sufficiently ensured, and the resistance in the low state of charge is likely to decrease. When the BET specific surface area is equal to or less than the upper limit value, the decomposition of the electrolyte or solid electrolyte on the surface of the CAM in the charged state is suppressed, and the resistance caused by the decomposition film can be suppressed.

[0041] D of CAM 50 is preferably 2 μm or more, more preferably 2.5 μm or more, and even more preferably 3.0 μm or more. D 50 is preferably 30 μm or less, more preferably 15 μm or less, and even more preferably 10 μm or less. D 50 is preferably 2 to 30 μm, more preferably 2.5 to 15 μm, and even more preferably 3.0 to 10 μm. D 50 When it is within the above range, lithium ions can easily diffuse into the particles in CAM, and the resistance in the low state of charge can be reduced.

[0042] In powder X-ray diffraction measurement using CuKα rays, the peak intensity X 1 relative to the peak intensity X 2 The ratio X 2 / X 1 is preferably 0.005 or more, and more preferably 0.01 or more. X 2 / X 1 is preferably 0.06 or less, and more preferably 0.05% or less. X 2 / X 1 is preferably 0.005 to 0.06, and more preferably 0.01 to 0.05. X 2 / X 1 When it is within the above range, it becomes a crystal structure in which lithium ions can easily move, and the resistance in the low state of charge is likely to decrease.

[0043] <Composition> CAM may further contain an M element. Examples of the M element include at least one element selected from the group consisting of Co, W, Nb, Mo, Ta, P, B, Ti, Zr, and Al.

[0044] When CAM contains the above elements, the resulting CAM forms a stable crystal structure in which lithium ions can be desorbed and inserted.

[0045] (Composition formula) The CAM is preferably represented by the following compositional formula (I). Li 1+a Ni x Mn y M b O 2 (I) In the above compositional formula (I), 0 ≦ a ≦ 0.5, 0 < x < 1, 0 < y < 1, a + x + y + b = 1, and 0 ≦ b < 1 are satisfied, and M is the above M element.

[0046] a is preferably 0.05 or more, more preferably 0.10 or more. a is preferably 0.45 or less, more preferably 0.40 or less, and even more preferably 0.38 or less. The above upper and lower limit values of a can be arbitrarily combined. When a is equal to or greater than the above lower limit value, the discharge capacity can be improved. When a is equal to or less than the above upper limit value, the resistance in the low state of charge can be reduced, and the cycle retention rate can be improved. a is preferably from 0 to 0.45, more preferably from 0.05 to 0.40, and even more preferably from 0.10 to 0.38.

[0047] x is preferably 0.01 or more, more preferably 0.05 or more, and even more preferably 0.10 or more. x is preferably 0.90 or less, more preferably 0.80 or less, even more preferably 0.7 or less, still more preferably 0.60 or less, and particularly preferably 0.45 or less. The above upper and lower limit values of x can be arbitrarily combined. When x is equal to or greater than the above lower limit value, the resistance in the low state of charge can be reduced, and the discharge capacity can be improved. When x is equal to or less than the above upper limit value, the cycle retention rate can be improved. x is, for example, preferably from 0.01 to 0.70, more preferably from 0.05 to 0.60, and even more preferably from 0.10 to 0.45.

[0048] y is preferably 0.10 or more, more preferably 0.20 or more, and still more preferably 0.30 or more. y is preferably 0.80 or less, more preferably 0.70 or less, and still more preferably 0.60 or less. The above upper and lower limit values of y can be arbitrarily combined. When y is equal to or greater than the lower limit value, the discharge capacity can be improved. When x is equal to or less than the upper limit value, the cycle retention rate can be improved. y is preferably from 0.10 to 0.80, more preferably from 0.20 to 0.70, and still more preferably from 0.30 to 0.60.

[0049] When the CAM contains the M element, b is preferably 0.02 or more, more preferably 0.05 or more. b is preferably 0.5 or less, more preferably 0.4 or less, and still more preferably 0.3 or less. The above upper and lower limit values of b can be arbitrarily combined. When b is equal to or greater than the lower limit value, the cycle retention rate can be improved. When b is equal to or less than the upper limit value, the discharge capacity can be improved. Also, b may be 0. b is preferably from 0 to 0.5, more preferably from 0.02 to 0.5, still more preferably from 0.05 to 0.4, and particularly preferably from 0.05 to 0.3.

[0050] When b is greater than 0, from the viewpoint of the cycle retention rate, M is preferably at least one element selected from the group consisting of Co, W, Nb, Mo, Ta, P, B, and Al, and more preferably at least one element selected from the group consisting of Co, W, Nb, Mo, and Al.

[0051] <Manufacturing method of CAM> The manufacturing method of CAM includes an MCC manufacturing step of manufacturing MCC, a mixing step of mixing the obtained MCC and a lithium compound, and a firing step of firing the obtained mixture.

[0052] (MCC manufacturing step) The MCC may be any of metal composite hydroxides, metal composite oxides, and mixtures thereof. The MCC production process includes reacting a solution of metal salts of Ni and Mn, a complexing agent, and an alkaline solution. In this case, the resulting MCC becomes a metal composite hydroxide. The metal composite hydroxide can be produced by a known batch coprecipitation method or a continuous coprecipitation method. The MCC contains Ni, Mn, and M in a molar ratio represented by the following formula (I’) as an example. M is, for example, Co or Al. Ni:Mn:M = x’:y’:b’ (I’) In the formula (I’), x’, y’, and b’ can be set to satisfy x, y, and b of the composition formula (I), respectively.

[0053] Hereinafter, a method for producing MCC containing Ni and Mn will be described as an example. Specifically, by the continuous coprecipitation method described in JP-A-2002-201028, a nickel salt solution, a manganese salt solution, and a complexing agent are reacted to produce a metal composite hydroxide represented by x’ Mn y’ (OH) 2 The nickel salt as the solute of the nickel salt solution is not particularly limited, and for example, at least one of nickel sulfate, nickel nitrate, nickel chloride, and nickel acetate can be used.

[0054] As the manganese salt as the solute of the manganese salt solution, for example, at least one of manganese sulfate, manganese nitrate, manganese chloride, and manganese acetate can be used.

[0055]

[0056] When producing MCC containing metal elements (such as Co and Al) other than Ni and Mn, sulfates, nitrates, chlorides, or acetates of the metal elements can also be used as the solute.

[0057] The above metal salts are the above Ni x’ Mn y’ (OH) 2 ​It is used in a proportion corresponding to the composition ratio. That is, the amounts of the respective metal salts are defined such that the molar ratio of Ni and Mn in the mixed raw material liquid containing the metal salt corresponds to x':y' of the formula (I'). Further, water can be used as the solvent. When y' is within the range of the formula (I'), X of CAM 2 / X 1 is likely to be within the above range.

[0058] First, an aqueous sodium hydroxide solution, a buffer solution such as ammonium sulfate, or water is introduced into the reaction vessel. Next, the mixed raw material liquid is dropped into the reaction vessel. At this time, the dropping rate of the mixed raw material liquid with respect to the total volume of the solution (buffer solution, water, etc.) contained in the reaction vessel before dropping the mixed raw material liquid is preferably 0.15 to 2.5 g / min / L, more preferably 0.2 to 2.0 g / min / L, and even more preferably 0.3 to 1.0 g / min / L. When the dropping rate is equal to or higher than the lower limit value of the above range, local pH fluctuations occur moderately, and Li 2 MnO 3 domains are likely to be formed. When the dropping rate is equal to or lower than the upper limit value of the above range, local pH fluctuations do not become too large, and Ni and Mn are less likely to precipitate simultaneously when the mixed raw material liquid comes into contact with the buffer solution. Therefore, Li 2 MnO 3 domains are likely to be formed. As a result, I 2 / I 1 CAM within the above range can be obtained. Further, when the dropping rate is within the above range, D of CAM 50 is likely to be within the above range. The total concentration of the metal elements contained in the mixed raw material liquid with respect to the total volume of the mixed raw material liquid is, for example, 10 to 200 g / L.

[0059] The complexing agent is capable of forming a complex with nickel ions and manganese ions in an aqueous solution. Examples thereof include ammonium ion donors such as ammonium hydroxide, ammonium sulfate, ammonium chloride, ammonium carbonate, or ammonium fluoride, hydrazine, ethylenediaminetetraacetic acid, nitrilotriacetic acid, uracildiacetic acid, and glycine, with ammonium ion donors being preferred.

[0060] In the production process of the metal composite hydroxide, the complexing agent may or may not be used. When the complexing agent is used, the amount of the complexing agent contained in the mixed solution containing the nickel salt solution, the manganese salt solution, and the complexing agent is preferably such that the molar ratio to the total number of moles of the metal salts (nickel salt and manganese salt) is greater than 0 and 2 or less.

[0061] In the coprecipitation method, in order to adjust the pH value of the mixed solution containing the nickel salt solution, the manganese salt solution, and the complexing agent, an alkaline solution is added to the mixed solution before the pH of the mixed solution changes from alkaline to neutral. Examples of the alkaline solution include aqueous solutions of alkali metal hydroxides. Examples of the alkali metal hydroxide include sodium hydroxide or potassium hydroxide.

[0062] Note that the pH value in this specification is the value measured when the temperature of the mixed solution is 40°C. When the temperature of the mixed solution sampled from the reaction tank is not 40°C, the mixed solution is heated or cooled to 40°C to measure the pH.

[0063] In addition to the above nickel salt solution and manganese salt solution, when the complexing agent is continuously supplied to the reaction tank, Ni and Mn react to form Ni x’ Mn y’ (OH) 2 is generated.

[0064] The reaction temperature is preferably 20 to 80°C, more preferably 25 to 75°C, and even more preferably 30 to 70°C. When the reaction temperature is within the above range, it is easy to obtain a CAM where F1 is within the range of this embodiment.

[0065] The pH value in the reaction tank is preferably 9 to 13, more preferably 9.5 to 12.5, and even more preferably 10 to 12. When the pH value is within the above range, it is easy to obtain the CAM in which the above F1 and F2 / F1 are within the range of the present embodiment.

[0066] The reaction precipitate formed in the reaction tank is neutralized while being stirred. The neutralization time of the reaction precipitate is, for example, 1 to 20 hours.

[0067] As the reaction tank used in the continuous coprecipitation method, a type of reaction tank that overflows to separate the formed reaction precipitate can be used.

[0068] When producing a metal composite hydroxide by the batch coprecipitation method, examples of the reaction tank include a reaction tank not equipped with an overflow pipe, and a device having a mechanism for concentrating the overflowed reaction precipitate in a concentrating tank connected to the overflow pipe and circulating it back to the reaction tank.

[0069] Various gases, for example, inert gases such as nitrogen, argon or carbon dioxide, oxidizing gases such as air or oxygen, or a mixed gas thereof may be supplied into the reaction tank.

[0070] The reaction temperature, pH, and dropping rate of the mixed raw material solution described above greatly affect the crystal structure of the finally obtained CAM and the amount of the Li 2 MnO 3 domain. Therefore, in order to satisfy the above requirements (1) and (2), it is preferable to appropriately adjust various conditions. In this embodiment, it is preferable that the reaction temperature is 30 to 70°C, the pH value in the reaction tank is 10 to 12, and the dropping rate of the mixed raw material liquid is 0.15 - 2.5 g / min / L. More preferably, the reaction temperature is 25 to 75°C, the pH value in the reaction tank is 9.5 to 12.5, and the dropping rate of the mixed raw material liquid is 0.2 to 2.0 g / min / L. Even more preferably, the reaction temperature is 30 to 70°C, the pH value in the reaction tank is 10 to 12, and the dropping rate of the mixed raw material liquid is 0.3 to 1.0 g / min / L. By setting such reaction conditions, it becomes easier to obtain a CAM that satisfies the above requirements (1) and (2).

[0071] After the above reaction, the neutralized reaction precipitate is washed with water and then isolated. For isolation, a method of dehydrating the slurry containing the reaction precipitate, such as centrifugation or suction filtration, is used.

[0072] The isolated reaction precipitate is dried and sieved as necessary to obtain a metal composite hydroxide containing Ni and Mn.

[0073] The washing of the reaction precipitate is preferably carried out with a washing liquid such as water, weak acid water, or an alkaline cleaning liquid. In this embodiment, it is preferable to wash with an alkaline cleaning liquid, and more preferably to wash with an aqueous sodium hydroxide solution or an aqueous potassium hydroxide solution. It is preferable to wash with a washing liquid having a mass 10 times or more the mass of the reaction precipitate. Also, the temperature of the washing liquid used is preferably 30°C or higher. Furthermore, if the washing is carried out batchwise, it is preferably carried out 2 or more times. In addition, after washing with weak acid water or an alkaline cleaning liquid, it is preferable to further wash with water so that the compounds derived from the above solution do not remain in the reaction precipitate.

[0074] The drying temperature is preferably 80 to 250°C, and more preferably 90 to 230°C. The drying time is preferably 0.5 to 24 hours, and more preferably 1 to 20 hours. The drying pressure may be normal pressure or reduced pressure.

[0075] When manufacturing a metal composite oxide as the MCC, the metal composite hydroxide may be heated to obtain the metal composite oxide. The heating temperature in this specification means the set temperature of the heating device. When there are a plurality of heating steps, among each heating step, it means the temperature of the step heated at the highest temperature.

[0076] The heating temperature is preferably 400 to 700 °C, and more preferably 450 to 680 °C. When the heating temperature is within the above range, the metal composite hydroxide is sufficiently oxidized, and a metal composite oxide having an appropriate range of BET specific surface area can be obtained.

[0077] The time for maintaining at the heating temperature may be 0.1 to 20 hours, and preferably 0.5 to 10 hours. The heating rate to the heating temperature is, for example, 50 to 400 °C / hour. Also, as the heating atmosphere, air, oxygen, nitrogen, argon, or a mixed gas thereof can be used.

[0078] The inside of the heating device may be an appropriate oxygen-containing atmosphere. 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 under an inert gas atmosphere. When the inside of the heating device is an appropriate oxygen-containing atmosphere, the transition metal contained in the metal composite hydroxide is appropriately oxidized, and it becomes easier to control the form of the metal composite oxide.

[0079] For the oxygen or oxidizing agent in the oxygen-containing atmosphere, it is sufficient that there are sufficient oxygen atoms to oxidize the transition metal.

[0080] When the oxygen-containing atmosphere is a mixed gas atmosphere of an inert gas and an oxidizing gas, the control of the atmosphere inside the heating device can be performed by methods such as introducing an oxidizing gas into the heating device or bubbling an oxidizing gas into the mixed liquid.

[0081] As the oxidizing agent, peroxides such as hydrogen peroxide, peroxide salts such as permanganate, perchlorate, hypochlorite, nitric acid, halogen, or ozone can be used.

[0082] Through the above steps, MCC can be manufactured.

[0083] In addition, when manufacturing a CAM containing at least one element selected from the group consisting of W, Nb, Mo, Ta, P, B, Ti, and Zr as the M element, a spraying and mixing step of spraying a solution containing a compound containing the M element onto the MCC while mixing the MCC obtained by the above method, and a drying step of drying the MCC onto which the solution containing the compound containing the M element has been sprayed may be included.

[0084] (Mixing step) Mix the MCC and the lithium compound. As the lithium compound, at least one of lithium carbonate, lithium nitrate, lithium acetate, lithium hydroxide, lithium hydroxide hydrate, lithium oxide, lithium chloride, and lithium fluoride can be used. Among these, either one of lithium hydroxide and lithium carbonate or a mixture thereof is preferable.

[0085] Mix the MCC and the lithium compound in consideration of the composition ratio of the final product to obtain a mixture of the MCC and the lithium compound. The amount of Li (molar ratio) to the total amount 1 of the metal elements contained in the MCC is preferably 0.98 to 1.80, more preferably 1.05 to 1.70, and even more preferably 1.10 to 1.60. When the amount of Li is within the above range, the X 2 / X 1 of the CAM is likely to be within the above range.

[0086] (Firing step) Fire the obtained mixture. By firing the mixture, the crystals of the CAM grow.

[0087] The firing temperature in this specification means the temperature of the atmosphere in the firing apparatus, which is the highest temperature of the holding temperature (the highest holding temperature). When the firing step has a plurality of firing stages, the firing temperature means the temperature of the stage fired at the highest holding temperature among the respective firing stages.

[0088] The firing temperature is preferably 500 to 1200 °C, more preferably 600 to 1100 °C, even more preferably 650 to 1050 °C, and particularly preferably 650 °C to 1000 °C. When the firing temperature is at least the lower limit value of the above range, CAM having a strong crystal structure can be obtained. Further, when the firing temperature is at most the upper limit value of the above range, the volatilization of lithium ions on the particle surface of CAM can be reduced. When the firing temperature is within the above range, the F2, F2 / F1, and BET specific surface area of CAM are likely to be within the above ranges.

[0089] The holding time in firing is preferably 1 to 50 hours, and more preferably 2 to 20 hours. When the holding time in firing is at most the upper limit value of the above range, the volatilization of lithium ions is suppressed, and the deterioration of battery performance is suppressed. When the holding time in firing is at least the lower limit value of the above range, the growth of crystals is promoted, and the deterioration of battery performance is suppressed. When the holding time in firing is within the above range, the F2, F2 / F1, and BET specific surface area of CAM are likely to be within the above ranges.

[0090] In the firing step, the heating rate until reaching the maximum holding temperature is preferably 80 °C / hour or more, more preferably 100 °C / hour or more, and even more preferably 150 °C / hour or more. The heating rate until reaching the maximum holding temperature is calculated in the firing apparatus from the time when heating is started to the time when the holding temperature is reached.

[0091] The firing step preferably has a plurality of firing stages with different firing temperatures. For example, it preferably has a first firing stage and a second firing stage with firing at a higher temperature than the first firing stage. Further, it may have firing stages with different firing temperatures and firing times.

[0092] As the firing atmosphere, air, oxygen, nitrogen, argon, or a mixed gas thereof, etc. is used according to the desired composition, and an oxygen-containing atmosphere is preferred.

[0093] The mixture of MCC and the lithium compound may be fired in the presence of an inert melting agent. The inert melting agent is added to such an extent that the initial capacity of the battery using CAM is not impaired and may remain in the fired product. As the inert melting agent, for example, the inert melting agent described in WO2019 / 177032A1 can be used.

[0094] The firing apparatus used during firing is not particularly limited, and for example, either a continuous stationary firing furnace or a fluidized firing furnace may be used. Examples of the continuous stationary firing furnace include a tunnel furnace or a roller hearth kiln. As the fluidized firing furnace, a rotary kiln may be used.

[0095] By firing the mixture of MCC and the lithium compound as described above, CAM is obtained.

[0096] <Lithium secondary battery> The positive electrode for a lithium secondary battery using the CAM of this embodiment will be described. Hereinafter, the positive electrode for a lithium secondary battery may be referred to as the positive electrode. Furthermore, a lithium secondary battery suitable for use as the positive electrode will be described.

[0097] An example of the lithium secondary battery using the CAM of this embodiment has a positive electrode and a negative electrode, a separator sandwiched between the positive electrode and the negative electrode, and an electrolytic solution disposed between the positive electrode and the negative electrode.

[0098] FIG. 1 is a schematic diagram showing an example of a lithium secondary battery. For example, a cylindrical lithium secondary battery 10 is manufactured as follows.

[0099] First, as shown in the partial enlarged view of FIG. 1, a pair of strip-shaped separators 1, a strip-shaped positive electrode 2 having a positive electrode lead 21 at one end, and a strip-shaped negative electrode 3 having a negative electrode lead 31 at one end are laminated in the order of separator 1, positive electrode 2, separator 1, negative electrode 3 and wound to form an electrode group 4.

[0100] The positive electrode 2 has, as an example, 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 on one side. Such a positive electrode 2 can be manufactured by first preparing a positive electrode mixture containing CAM, a conductive material, and a binder, and forming the positive electrode active material layer 2a by supporting the positive electrode mixture on one side of the positive electrode current collector 2b.

[0101] The negative electrode 3 can include, as an example, 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 composed of only the negative electrode active material, and can be manufactured by the same method as the positive electrode 2.

[0102] Next, after accommodating the electrode group 4 and an insulator (not shown) in the battery can 5, the bottom of the can is sealed, the electrode group 4 is impregnated with the electrolyte 6, and an electrolyte is disposed between the positive electrode 2 and the negative electrode 3. Further, the lithium secondary battery 10 can be manufactured by sealing the upper part of the battery can 5 with a top insulator 7 and a sealing body 8.

[0103] Examples of the shape of the electrode group 4 include a columnar shape such that the cross-sectional shape when the electrode group 4 is cut in a direction perpendicular to the winding axis is a circle, an ellipse, a rectangle, or a rectangle with rounded corners.

[0104] Also, as the shape of the lithium secondary battery having such an electrode group 4, the shape defined by IEC60086, which is a standard for batteries defined by the International Electrotechnical Commission (IEC), or JIS C 8500 can be adopted. For example, shapes such as a cylindrical shape or a rectangular shape can be mentioned.

[0105] Furthermore, the lithium secondary battery is not limited to the above-described wound type configuration, and may be a stacked type configuration in which a stacked structure of a positive electrode, a separator, a negative electrode, and a separator is repeatedly stacked. Examples of the stacked type lithium secondary battery include a so-called coin type battery, a button type battery, or a paper type (or sheet type) battery.

[0106] Regarding the positive electrode, separator, negative electrode, and electrolytic solution 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.

[0107] <All-solid-state lithium secondary battery> The CAM of this embodiment can be used as the CAM of an all-solid-state lithium secondary battery.

[0108] FIG. 2 is a schematic diagram showing an example of an all-solid-state lithium secondary battery. The all-solid-state lithium secondary battery 1000 shown in FIG. 2 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. Further, the all-solid-state lithium secondary battery 1000 may have a bipolar structure in which the CAM and the negative electrode active material are disposed on both sides of the current collector. As a specific example of the bipolar structure, for example, the structure described in JP-A-2004-95400 can be mentioned.

[0109] 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 contains the above-described CAM and solid electrolyte. Further, the positive electrode active material layer 111 may contain a conductive material and a binder.

[0110] The negative electrode 120 has a negative electrode active material layer 121 and a negative electrode current collector 122. The negative electrode active material layer 121 contains a negative electrode active material. Further, the negative electrode active material layer 121 may contain a solid electrolyte and a conductive material.

[0111] 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 have a separator between the positive electrode 110 and the negative electrode 120.

[0112] The all-solid-state lithium secondary battery 1000 further has an insulator (not shown) that insulates the laminate 100 and the exterior body 200 and a sealing body (not shown) that seals the opening 200a of the exterior body 200.

[0113] As the exterior body 200, a container formed of a highly corrosion-resistant metal material such as aluminum, stainless steel, or nickel-plated steel can be used. Also, as the exterior body 200, a container obtained by processing a laminate film having corrosion-resistant processing on at least one surface into a bag shape can be used.

[0114] 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 rectangular shape, or a laminate shape (pouch shape).

[0115] As an example, a form having one laminate 100 is illustrated for the all-solid-state lithium secondary battery 1000, but the present embodiment 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 (laminates 100) are sealed inside the exterior body 200.

[0116] Regarding the all-solid-state lithium secondary battery, for example, the configurations, materials, and manufacturing methods described in

[0151] to

[0181] of WO2022 / 113904A1 can be used.

[0117] Another aspect of the present invention includes the following aspects. [A1] A CAM containing Li, Mn, and Ni and satisfying the above requirement (1) and the following requirement (2)-1. (2)-1 The I 2 / I 1 is 0.24 to 0.40. [A2] The CAM according to [A1], wherein F2 / F1 is 1.0 to 1.8. [A3] The CAM according to [A1] or [A2], which is represented by the composition formula (I). [A4] The CAM according to any one of [A1] to [A3], having a BET specific surface area of 0.5 to 2.4 m 2 / g. [A5] The D 50The CAM according to any one of [A1] to [A4], wherein the [dimension] is 3.0 to 10 μm. [A6] The above X 2 / X 1 The CAM according to any one of [A1] to [A5], wherein [the ratio] is 0.005 to 0.06. [A7] The above I 1 is 200 to 1000 cm -1 The CAM according to any one of [A1] to [A6], which has the highest intensity among the peaks obtained within the following range. [A8] The CAM according to any one of [A1] to [A7], wherein F2 / F1 is 1.0 to 1.6. [A9] A positive electrode for a lithium secondary battery containing the CAM according to any one of [A1] to [A8]. [A10] A lithium secondary battery containing the positive electrode for a lithium secondary battery according to [A9].

Example

[0118] Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited thereto.

[0119] <Measurement of various parameters of CAM> The measurement of various parameters of the CAM manufactured by the method described below was performed by the measurement methods described above for (Raman spectroscopic analysis parameters), (BET specific surface area), (composition), (50% cumulative volume particle size D 50 ), (XRD pattern, X 2 / X 1 measurement), and (confirmation of crystal structure).

[0120] <Measurement of resistance in a low state of charge> The resistance of the lithium secondary battery in a low state of charge was measured by the method described above for (resistance in a low state of charge). When the resistance is 33.0 Ω or less, it is evaluated that the resistance in the low state of charge is low.

[0121] [Example 1] After adding water into a reaction tank equipped with a rotary stirring device having stirring blades and an overflow pipe, an aqueous sodium hydroxide solution was added, and the liquid temperature was maintained at 30 °C (reaction temperature).

[0122] An aqueous nickel sulfate solution, an aqueous cobalt sulfate solution, and an aqueous manganese sulfate solution were mixed so that the molar ratio of Ni:Co:Mn was 17:17:66 to prepare a mixed raw material liquid 1.

[0123] Under a nitrogen flow, in the reaction tank, while stirring, the mixed raw material liquid 1 and an aqueous ammonium sulfate solution as a complexing agent were continuously added. An aqueous sodium hydroxide solution was appropriately dropped so that the pH of the mixed liquid in the reaction tank became 11.7 (measurement temperature: 40 °C) to obtain a reaction precipitate 1. The dropping rate of the mixed raw material liquid 1 with respect to the total volume of the solution in the reaction tank was 1.0 g / min / L.

[0124] The reaction precipitate 1 was washed with water. After washing, it was dehydrated with a centrifuge, further washed with water, dehydrated, isolated, and dried at 105 °C for 20 hours to obtain MCC1, a metal composite hydroxide containing Ni, Co, and Mn.

[0125] Lithium hydroxide was weighed so that the amount (molar ratio) of Li to the total amount 1 of Ni, Co, and Mn contained in MCC1 was 1.50. MCC1 and lithium hydroxide were mixed to obtain a mixture 1.

[0126] Next, the obtained mixture 1 was calcined at 900 °C for 10 hours in an oxygen atmosphere to obtain CAM1. Various parameters of CAM1 are shown in Table 1 (hereinafter, Examples 2 to 4 and Comparative Examples 1 and 2 are also shown in the same manner). Note that a, x, y, and b in the composition in Table 1 are values corresponding to the composition formula (I).

[0127] Using the obtained CAM1, a lithium secondary battery was fabricated, and the resistance in a low state of charge was measured. The results are shown in Table 1 (hereinafter, Examples 2 to 4 and Comparative Examples 1 and 2 are also shown in the same manner).

[0128] [Example 2] After putting water into a reaction tank equipped with a rotary stirring device having stirring blades and an overflow pipe, an aqueous sodium hydroxide solution was added, and the liquid temperature was maintained at 30 °C (reaction temperature).

[0129] An aqueous nickel sulfate solution and an aqueous manganese sulfate solution were mixed so that the molar ratio of Ni:Mn was 50:50 to prepare a mixed raw material liquid 2.

[0130] Under nitrogen flow, the mixed raw material liquid 2 and an aqueous ammonium sulfate solution as a complexing agent were continuously added to the reaction tank with stirring. An aqueous sodium hydroxide solution was appropriately dropped so that the pH of the mixed liquid in the reaction tank became 11.7 (measurement temperature: 40 °C) to obtain a reaction precipitate 2. The dropping rate of the mixed raw material liquid 2 with respect to the total volume of the solution in the reaction tank was 0.4 g / min / L.

[0131] The reaction precipitate 2 was washed with water. After washing, it was dehydrated with a centrifuge, further washed with water, dehydrated, isolated, and dried at 105 °C for 20 hours to obtain MCC2, a metal composite hydroxide containing Ni and Mn.

[0132] Lithium hydroxide was weighed so that the amount (molar ratio) of Li to the total amount 1 of Ni and Mn contained in MCC2 was 1.30. MCC2 and lithium hydroxide were mixed to obtain a mixture 2.

[0133] Next, the obtained mixture 2 was calcined at 650 °C for 5 hours in an oxygen atmosphere, and then at 1000 °C for 5 hours to obtain CAM2.

[0134] [Example 3] After putting water into a reaction tank equipped with a rotary stirring device having stirring blades and an overflow pipe, an aqueous sodium hydroxide solution was added, and the liquid temperature was maintained at 30 °C (reaction temperature). Under nitrogen flow, the above-mentioned mixed raw material liquid 2 and an aqueous ammonium sulfate solution as a complexing agent were continuously added to the reaction tank with stirring. An aqueous sodium hydroxide solution was appropriately dropped so that the pH of the mixed liquid in the reaction tank became 11.7 (measurement temperature: 40 °C) to obtain a reaction precipitate 3. The dropping rate of the mixed raw material liquid 2 with respect to the volume of the solution in the reaction tank was set to 1.0 g / min / L.

[0135] The reaction precipitate 3 was washed with water. After washing, it was dehydrated with a centrifuge, further washed with water, dehydrated, isolated, and dried at 105 °C for 20 hours to obtain MCC3, a metal composite hydroxide containing Ni and Mn. Lithium hydroxide was weighed so that the amount (molar ratio) of Li to the total amount 1 of Ni and Mn contained in MCC3 would be 1.15. MCC3 and lithium hydroxide were mixed to obtain a mixture 3.

[0136] Next, the obtained mixture 3 was calcined at 650 °C for 5 hours in an oxygen atmosphere, and then calcined at 1000 °C for 5 hours to obtain CAM3.

[0137] [Example 4] Lithium hydroxide was weighed so that the amount (molar ratio) of Li to the total amount 1 of Ni, Co, and Mn contained in MCC1 would be 1.5. MCC1 and lithium hydroxide were mixed to obtain a mixture 4.

[0138] Using the mixture 4, it was calcined in the same manner as in Example 1 to obtain CAM4.

[0139] [Comparative Example 1] CAM5 was obtained in the same manner as in Example 3, except that the dropping rate of the mixed raw material liquid 2 with respect to the total volume of the solution in the reaction tank was set to 0.1 g / min / L.

[0140] [Comparative Example 2] After putting water into a reaction tank equipped with a rotary stirring device having a stirring blade and an overflow pipe, an aqueous sodium hydroxide solution was added, and the liquid temperature was maintained at 40 °C (reaction temperature).

[0141] Under a nitrogen flow, the above mixed raw material solution 2 and an aqueous ammonium sulfate solution as a complexing agent were continuously added to the reaction tank with stirring. An aqueous sodium hydroxide solution was added dropwise in a timely manner so that the pH of the mixed solution in the reaction tank became 11.7 (measurement temperature: 40 °C), and reaction precipitate 6 was obtained. The dropping rate of the mixed raw material solution 6 with respect to the total volume of the solution in the reaction tank was 2.8 g / min / L.

[0142] The reaction precipitate 6 was washed with an aqueous sodium hydroxide solution having a mass 20 times that of the reaction precipitate 6 (sodium hydroxide concentration: 5% by mass). After washing, it was dehydrated with a centrifuge, further washed with water, dehydrated, isolated, and dried at 105 °C for 20 hours to obtain MCC6, a metal composite hydroxide containing Ni and Mn.

[0143] CAM6 was obtained in the same manner as in Example 3 except that MCC6 was used.

[0144]

Table 1

[0145] All of CAM1 to 6 have a layered structure, and their main crystal structure was attributed to the space group R-3m. In CAM1 to 6, the I 1 was the highest among the peak intensities obtained within the range of 200 - 1000 cm -1 .

[0146] It was found that in the lithium secondary battery manufactured using the CAMs of Examples 1 to 4 that satisfy Requirements (1) and (2), the resistance in the low state of charge is lower than that of the lithium secondary battery manufactured using the CAMs of Comparative Examples 1 and 2 that do not satisfy Requirement (2).

Explanation of Symbols

[0147] 1... separator, 2... positive electrode, 2a... positive electrode active material layer, 2b... positive electrode current collector, 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, 100... laminate, 110... positive electrode, 111... positive electrode active material layer, 112... positive electrode current collector, 113... external terminal, 120... negative electrode, 121... negative electrode active material layer, 122... negative electrode current collector, 123... external terminal, 130... solid electrolyte layer, 200... exterior body, 200a... opening, 1000... all-solid-state lithium secondary battery

Claims

1. A positive electrode active material for a lithium secondary battery contains Li, Mn, and Ni, and satisfies the following requirements (1) and (2): (1) It has a layered structure. (2) In Raman spectroscopy with an excitation wavelength of 532 nm, －１ The peak is P1, 415-455 cm －１ The peak intensity of P1 is I １ , and the peak intensity of P2 is I ２ When I ２ / I １ is equal to or greater than 0.22 and equal to or less than 0.

45.

2. 2. The positive electrode active material for a lithium secondary battery according to claim 1, wherein F2 / F1 is 0.5 or more and 2.0 or less, where F1 is a half width of P1 and F2 is a half width of P2.

3. 3. The positive electrode active material for a lithium secondary battery according to claim 1 or 2, which is represented by the following composition formula (I): Li １＋ａ Ni ｘ Mn ｙ M ｂ O ２ (I) [In the composition formula (I), 0≦a≦0.5, 0<x<1, 0<y<1, a+x+y+b=1, and 0≦b<1 are satisfied, and M is at least one element selected from the group consisting of Co, W, Nb, Mo, Ta, P, B, Ti, Zr, and Al.]

4. BET specific surface area is 0.2m ２ / g or more 3m ２ The positive electrode active material for a lithium secondary battery according to claim 1 or 2, wherein the Mo content is 1 / g or less.

5. 50% cumulative volume particle size D ５０ The positive electrode active material for a lithium secondary battery according to claim 1 or 2, wherein the average particle size is 2 μm or more and 30 μm or less.

6. In powder X-ray diffraction measurement using CuKα radiation, the peak intensity X of the peak present in the range of 2θ = 18.7 ± 1 ° is １ The peak intensity X of the peak existing in the range of 2θ=20.7±1° ２ The ratio of X ２ / X １ The positive electrode active material for a lithium secondary battery according to claim 1 or 2, wherein is 0.005 or more and 0.06 or less.

7. I １ is 200 cm －１ More than 1000cm －１ 3. The positive electrode active material for a lithium secondary battery according to claim 1, which has the highest peak intensity obtained within the following ranges:

8. A positive electrode for a lithium secondary battery comprising the positive electrode active material for a lithium secondary battery according to claim 1 or 2.

9. A lithium secondary battery comprising the positive electrode for lithium secondary batteries according to claim 8.

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