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 that can provide a lithium secondary battery that can be charged as desired and has excellent thermal stability.SOLUTION: A positive electrode active material for a lithium secondary battery having a layered structure, includes at least Li, Ni, and an element X, and the element X is one or more elements selected from the group consisting of Ti and Zr, and when the peak which is present between 520 cm-1 and 560 cm-1 obtained by peak fitting using a Lorentzian function on a Raman spectrum obtained by Raman spectroscopy with an excitation wavelength of 532 nm is P1, and the peak which is present between 560 cm-1 and 600 cm-1 is P2, the ratio of the maximum peak intensity I1 of P1 to the maximum peak intensity I2 of P2 is 1.25 or more and 3.00 or less.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 technology]

[0002] A positive electrode active material for lithium secondary batteries is used for the positive electrode that constitutes the lithium secondary battery.

[0003] For example, Patent Document 1 discloses a positive electrode active material for a non-aqueous electrolyte secondary battery containing a lithium transition metal composite oxide, which exhibits a Raman spectrum of 550 to 650 cm -1 The maximum value in the range of I 600 450~520cm -1 The maximum value in the range of I 490 The ratio (I 490 / I 600 ) is 0.45 or more. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP-B-7031108 Summary of the Invention [Problem to be solved by the invention]

[0005] As the application fields of lithium secondary batteries expand, there is a demand for not only the ability to charge as desired but also improved thermal stability.

[0006] An object of the present invention is to obtain a positive electrode active material for a lithium secondary battery that can provide a lithium secondary battery that is capable of desired charging and has excellent thermal stability.

[0007] Another object of the present invention is to provide a positive electrode for a lithium secondary battery and a lithium secondary battery containing the above-mentioned positive electrode active material for a lithium secondary battery. [Means for solving the problem]

[0008] The present invention encompasses the following [1] to [6]. [1] A positive electrode active material for a lithium secondary battery having a layered structure, containing at least Li, Ni, and an element X, wherein the element X is one or more elements selected from the group consisting of Ti and Zr, and a peak at 520 cm obtained by peak fitting using a Lorentz function to a Raman spectrum obtained by Raman spectroscopy at an excitation wavelength of 532 nm. -1 More than 560cm -1 The peak present below 560 cm is P1. -1 More than 600cm -1 A positive electrode active material for a lithium secondary battery, wherein, when the peaks present below are designated as P2, the ratio of the maximum peak intensity I1 of P1 to the maximum peak intensity I2 of P2 is 1.25 or more and 3.00 or less. [2] The half-width of the P1 is 40 cm -1 Over 57cm -1 The positive electrode active material for a lithium secondary battery according to [1], which is as follows: [3] In the Raman spectrum, 300 cm -1 More than 700cm -1 When the spectrum below is S1, the half width of S1 is 135 cm -1 over 170cm -1 The positive electrode active material for a lithium secondary battery according to [1] or [2], which is: [4] A positive electrode active material for a lithium secondary battery according to any one of [1] to [3], which is represented by the following formula (I): Li a (Ni (1-y-z-w) M1 y M2 z X w ) 1-a ]O2(I) (In formula (I), -0.1 ≤ a ≤ 0.2, 0 ≤ y ≤ 0.9, 0 ≤ z ≤ 0.9, 0 < w ≤ 0.1, y + z + w < 1, M1 is one or more elements selected from the group consisting of Co and Mn, M2 is one or more elements selected from the group consisting of Fe, Cu, Mg, Al, W, Mo, Nb, Zn, Sn, Ga, B and V, and X is one or more elements selected from the group consisting of Ti and Zr.) [5] The 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 [4]. [6] A lithium secondary battery having the positive electrode for a lithium secondary battery according to [5]. [Effect of the Invention]

[0009] According to the present invention, it is possible to obtain a positive electrode active material for a lithium secondary battery that can enable desired charging and has excellent thermal stability. Furthermore, it is possible to provide a positive electrode for a lithium secondary battery and a lithium secondary battery containing such a positive electrode active material for a lithium secondary battery. [Brief Description of the Drawings]

[0010] [Figure 1] It is a schematic diagram showing an example of a lithium secondary battery. [Figure 2] It is a schematic diagram showing an example of an all-solid-state lithium secondary battery. [Mode for Carrying Out the Invention]

[0011] In the present specification, the metal composite compound (Metal Composite Compound) is hereinafter referred to as "MCC", and the positive electrode active material for a lithium secondary battery (Cathode Active Material for lithium secondary batteries) is hereinafter referred to as "CAM".

[0012] "Ni" does not refer to nickel metal but refers to nickel atoms. Similarly, "Co", "Li", etc. each refer to cobalt atoms, lithium atoms, etc. The lithium secondary battery refers to a lithium ion secondary battery.

[0013] When a numerical range is stated as, for example, "1-10 μm" or "1 to 10 μm," it means a range from 1 μm to 10 μm, including the lower limit of 1 μm and the upper limit of 10 μm.

[0014] Regarding the ranges of values ​​in this specification, the upper and lower limits can be combined in any way. The respective numerical ranges of the properties, compositions, and manufacturing conditions can be combined in any desired manner.

[0015] [Evaluation of thermal stability] In this specification, "excellent thermal stability" means that the amount of oxygen released per unit time is equal to or less than a certain value, and specifically means that the oxygen release rate measured by the following method is equal to or less than 1.1 mass% / min.

[0016] -Method for measuring oxygen release rate First, a lithium secondary battery containing CAM is fabricated as follows.

[0017] [Preparation of positive electrodes for lithium secondary batteries] A paste-like positive electrode mixture is prepared by mixing and kneading CAM, a conductive material (acetylene black), and a binder (PVdF) in a mass ratio of CAM:conductive material:binder = 92:5:3. N-methyl-2-pyrrolidone is used as the organic solvent when preparing the positive electrode mixture.

[0018] The resulting positive electrode mixture is applied to a 20 μm thick Al foil as a current collector and dried in vacuum at 150°C for 8 hours to obtain a positive electrode for a lithium secondary battery. The electrode area of ​​this positive electrode for a lithium secondary battery is 1.65 cm2. 2 Let's say.

[0019] [Fabrication of lithium secondary batteries] The following operations are carried out in a glove box under an argon atmosphere. The above-mentioned positive electrode for the lithium secondary battery was placed with the aluminum foil side facing down on the bottom cover of a coin-type battery R2032 part (manufactured by Hosen Co., Ltd.), and a polypropylene monolayer film separator (25 μm thick) was placed on top of it. 265 μl of electrolyte was poured into this. The electrolyte was a 30:35:35 (volume ratio) mixture of ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate, with LiPF6 dissolved at a ratio of 1 mol / L. Next, metallic lithium is used as the negative electrode and placed on the separator, and the top lid is placed on the negative electrode via a gasket, and the battery is crimped with a crimping machine to prepare a lithium secondary battery (coin-type half cell R2032).

[0020] This lithium secondary battery was charged to 220 mAh / g at a constant current and constant voltage under conditions of a test temperature of 25°C and a charging current of 0.1 CA. Here, "the desired charge was possible" in this specification means that charging to 220 mAh / g was possible. The positive electrode removed from the charged lithium secondary battery was then washed with dimethyl carbonate in a glove box under an argon gas atmosphere to remove any electrolyte adhering to the positive electrode. The washed positive electrode was then dried to remove any cleaning solution adhering to the positive electrode. The positive electrode active material layer coated on the Al foil of the positive electrode was then scraped off using ceramic tweezers to obtain a sample. The sample was then analyzed using the following [thermogravimetric analysis method].

[0021] Thermogravimetric analysis method The thermogravimetric analyzer used may be STA7300 manufactured by Hitachi High-Tech Science Corporation. Sample weighing is performed on the balance beam of the STA7300. Approximately 5 mg of sample is weighed out, placed in a platinum measuring container, and set in the measuring device. The temperature is raised from 40°C to 350°C at a rate of 5°C / min under a nitrogen flow of 5 ml / min to obtain a TG curve. The oxygen release rate is determined from the weight change in the obtained TG curve.

[0022] <Positive electrode active material for lithium secondary batteries> The CAM of this embodiment contains at least Li, Ni, and an element X, and has a layered structure. The element X is one or more elements selected from the group consisting of Ti and Zr. The CAM may contain an element M1 and may further contain an element M2. The element M1 is one or more elements selected from the group consisting of Co and Mn, and the element M2 is one or more elements selected from the group consisting of Fe, Cu, Mg, Al, W, Mo, Nb, Zn, Sn, Ga, B, and V.

[0023] The CAM was obtained by peak fitting the Raman spectrum obtained by Raman spectroscopy at an excitation wavelength of 532 nm using a Lorentzian function. -1 More than 560cm -1 The peak present below 560 cm is P1. -1 More than 600cm -1 When the peaks present below are designated as P2, the ratio of the maximum peak intensity I1 of P1 to the maximum peak intensity I2 of P2 (hereinafter referred to as I1 / I2) is 1.25-3.00. I1 / I2 is preferably 1.30 or more, more preferably 1.35 or more. I1 / I2 is preferably 2.75 or less, more preferably 2.25 or less. Examples of I1 / I2 include 1.30-2.75 or 1.35-2.25.

[0024] Raman spectroscopy can identify the vibrational modes of the atomic groups contained in CAM and obtain information about the bonding state. In the Raman spectrum, each peak appears at a position (wavenumber band) corresponding to the vibrational mode of each atomic group in CAM.

[0025] P1 is a peak due to bonds between element X, oxygen atoms, and element Me. That is, P1 is due to bonds between two elements X, an oxygen atom, and element Me, or bonds between two elements Me, an oxygen atom, and element X (hereinafter sometimes referred to as XO-Me bonds), and bonds between three elements X and an oxygen atom (hereinafter sometimes referred to as XOX bonds). P2 is due to the bond between an oxygen atom and three elements Me (hereinafter, sometimes referred to as Me-O-Me bond). Here, the element Me is an element other than Li, the element X, and an oxygen atom among the elements constituting CAM, and is, for example, at least one element selected from the group consisting of the above element M1, the above element M2, and Ni.

[0026] The Raman spectra compare the stretching vibrations of XO-Me bonds, XOX bonds, and Me-O-Me bonds. Because the bonds being compared are similar, I1 and I2 correlate with the amount of bonding. CAMs with I1 / I2 in the above ranges have a variety of XO-Me bonds, XOX bonds, and Me-O-Me bonds.

[0027] For example, when the element Me is Ni and Mn and the element X is one type (Ti or Zr), there are five possible combinations of the element X and the element Me contained in the XO-Me bond: The combinations of element X and element Me contained in the XO-Me bond are: (Ni, Ni, X), (Ni, Mn, X), (Ni, X, X), (Mn, Mn, X), and (Mn, X, X).

[0028] Furthermore, for example, when the element Me is Ni and Mn, there are the following four combinations of the three elements Me in the Me-O-Me bond. Three elements Me in Me-O-Me bonds: (Ni, Ni, Ni), (Ni, Ni, Mn), (Ni, Mn, Mn), (Mn, Mn, Mn)

[0029] The expression "there is diversity in the XO-Me bond, the XOX bond, and the Me-O-Me bond" means that the CAM does not have only one kind of the above combinations of XO-Me bond, XOX bond, and Me-O-Me bond, but has multiple kinds of bonds with different combinations. The expression "the CAM has multiple kinds of Me-O-Me bonds with different combinations" means, for example, that the element Me has two or more kinds of bonds selected from the group consisting of (Ni, Ni, Ni), (Ni, Ni, Mn), (Ni, Mn, Mn), and (Mn, Mn, Mn). CAMs with diverse XO-Me bonds, XOX bonds, and Me-O-Me bonds tend to have a low oxygen release rate because the temperature and speed at which oxygen atoms bonded to element Me or element X are released as oxygen molecules tend to vary. This makes it possible to provide a lithium secondary battery that can be charged as desired and has excellent thermal stability.

[0030] [Raman spectroscopy] The Raman spectrum can be obtained, for example, using a laser Raman microscope (manufactured by Nanophoton, model number RAMANTouch), a single spectrometer, and an electronically cooled CCD detector, under the following conditions: excitation wavelength 532 nm, slit width 50 μm, diffraction grating 600 gr / mm, output 5 mW, irradiation time 300 seconds, and accumulation count 10 times.

[0031] In the Raman spectroscopic analysis, the CAM may be measured, or the positive electrode having the CAM may be measured. When performing the Raman spectroscopic analysis on the positive electrode, it is preferable to irradiate the surface of the positive electrode on which the CAM is applied with a laser. In the examples and comparative examples described later, the CAM is measured.

[0032] The Raman spectrum is a graph in which the vertical axis represents the scattered light intensity in arbitrary units and the horizontal axis represents the Raman shift wave number (cm -1 ) is the spectrum expressed as

[0033] The obtained Raman spectrum is analyzed by the following procedure.

[0034] [Analysis method] (Analysis 1) (1) Perform baseline correction of the obtained Raman spectrum. For baseline correction, a piecewise linear function may be used to correct the background. (2) After baseline correction, the maximum peak value is normalized to 1. (3) 300-700cm -1 The selected spectrum is designated as S1, and the width at half height of the peak of S1 is designated as the half width (full width at half maximum) of S1. Here, when S1 has multiple maximum values, the width at half the height of the peak with the maximum height is defined as the half-width of S1. (4) 520cm -1 More than 560cm -1 Peaks present below 560 cm -1 More than 600cm -1 The peak present at 470 cm -1 More than 520cm -1 Peaks present below 430 cm -1 Over 470cm -1 For peaks present below , peak fitting is performed using a Lorentzian function. The Lorentzian function is defined by the following equation (1). In this case, the above four peaks are fitted in a single process. For peak fitting, Python's BFGS algorithm is used. F(x)=A / (1+(x-x0) 2 / γ 2 ) ...Formula (1) (In Equation (1), A is the peak intensity, and x is the Raman shift wave number (cm -1 ), γ corresponds to the half-width at half maximum of the peak (half the value of the half-width at half maximum). x0 means the Raman shift wave number when the peak intensity is maximum. (5) 520 cm obtained by the above peak fitting -1 More than 560cm -1 The peak present below 560 cm is P1. -1 More than 600cm -1 The peaks present below are designated as P2, and the peak intensity I1 of P1 and the peak intensity I2 of P2 are calculated. (6) Calculate I1 / I2, which is the ratio of I1 to I2.

[0035] (Analysis 2) The width at half the height of the peak of P1 is defined as the half width (full width at half maximum) of P1. Here, "half the height of the peak" means half the height from the peak top to the baseline.

[0036] The half-width of P1 obtained by the above (Analysis 2) is 40 cm -1More than 45cm is preferable. -1 More than 47cm is preferable. -1 More preferably, the full width at half maximum of P1 is 57 cm -1 The following is preferred: The half-width of P1 is, for example, 40-57 cm -1 , 45-57cm -1 , or 47-57cm -1 etc. A CAM with a P1 half-width in the above range means that it has many peaks due to XO-Me bonds and XOX bonds. Such CAM has a variety of XO-Me bonds, XOX bonds, and Me-O-Me bonds, which means that the temperature and speed at which oxygen atoms bonded to element Me or element X are released as oxygen molecules tend to vary, resulting in a low oxygen release rate. This makes it possible to provide a lithium secondary battery that is capable of desired charging and has excellent thermal stability.

[0037] The half-width of S1 obtained from the above (Analysis 1) is 135 cm -1 More than 140cm is preferable. -1 More than 145cm is preferable. -1 More preferably, the half-width of S1 is 170 cm -1 Preferably under 168cm -1 Less than 165cm is preferable -1 The following is even more preferred: The half-width of S1 is, for example, 135-170 cm -1 , 140-168cm -1 , or 145-165cm -1 etc. A CAM having an S1 half-width in the above range means that the CAM has many peaks due to XO-Me bonds and XOX bonds in its Raman spectrum. For the same reasons as above, such a CAM tends to have a low oxygen release rate, and can provide a lithium secondary battery that is capable of desired charging and has excellent thermal stability.

[0038] The CAM is preferably represented by the following formula (I). Li[Li a (Ni (1-y-z-w) M1 y M2 z X w ) 1-a O2 (I) (In formula (I), -0.1 ≦ a ≦ 0.2, 0 ≦ y ≦ 0.9, 0 ≦ z ≦ 0.9, 0 < w ≦ 0.1, y + z + w < 1. M1 is one or more elements selected from the group consisting of Co and Mn. M2 is one or more elements selected from the group consisting of Fe, Cu, Mg, Al, W, Mo, Nb, Zn, Sn, Ga, B, and V. X is one or more elements selected from the group consisting of Ti and Zr.)

[0039] From the viewpoint of enabling desired charging and having excellent thermal stability, a is more preferably -0.05 or more, and further preferably 0 or more. Also, a is more preferably 0.15 or less, and further preferably 0.10 or less. a is, for example, -0.05 - 0.15, 0 - 0.10.

[0040] From the viewpoint of enabling desired charging and having excellent thermal stability, y is more preferably 0.05 or more, and further preferably 0.10 or more. Also, y is more preferably 0.8 or less, and further preferably 0.7 or less. y is, for example, 0.05 - 0.9, 0.10 - 0.7.

[0041] From the viewpoint of enabling desired charging and having excellent thermal stability, z may be 0 or may be 0.1 or more. Also, z is more preferably 0.8 or less, and further preferably 0.7 or less. z is, for example, 0 - 0.8, 0 - 0.7, 0.1 - 0.7.

[0042] From the viewpoint of enabling desired charging and having excellent thermal stability, w is more preferably 0.001 or more. Also, w is more preferably 0.08 or less, and further preferably 0.06 or less. w is, for example, 0.001 - 0.08, 0.001 - 0.06.

[0043] From the viewpoints of enabling desired charging and achieving better thermal stability, y+z+w exceeds 0, is preferably 0.05 or more, and is further preferably 0.1 or more, and is further preferably 0.6 or less, and is further preferably 0.3 or less. y+z+w is, for example, 0.05-0.6, 0.1-0.3.

[0044] M2 is preferably one or more elements selected from the group consisting of Mg, Al, W, Nb, Zn, B, and Sn. Even when CAM contains element M2, the above P1 and P2 peaks appear.

[0045] [Composition analysis] The composition of CAM is analyzed by dissolving CAM powder in hydrochloric acid and then measuring the composition using an ICP emission spectrometer. As the ICP emission spectrometer, for example, Optima 7300 manufactured by PerkinElmer Co., Ltd. can be used.

[0046] CAM has a layered structure, and from the viewpoints of enabling desired charging and improving thermal stability, it more preferably has a hexagonal crystal structure or a monoclinic crystal structure.

[0047] The hexagonal crystal structure is P3, P31, P32, R3, P-3, R-3, P312, P321, P3112, P3121, P3212, P3221, R32, P3m1, P 31m, P3c1, P31c, R3m, R3c, P-31m, P-31c, P-3m1, P-3c1, R-3m, R-3c, P6, P61, P65, P62, P64, P63 , P-6, P6 / m, P63 / m, P622, P6122, P6522, P6222, P6422, P6322, P6mm, P6cc, P63cm, P63mc, P-6m2, P-6c2, P-62m, P-62c, P6 / mmm, P6 / mcc, P63 / mcm, and P63 / mmc.

[0048] Furthermore, the monoclinic crystal structure belongs to any one space group selected from the group consisting of P2, P21, C2, Pm, Pc, Cm, Cc, P2 / m, P21 / m, C2 / m, P2 / c, P21 / c, and C2 / c.

[0049] From the viewpoint of obtaining a lithium secondary battery that can be charged as desired and has excellent thermal stability, it is more preferable that CAM has a hexagonal crystal structure belonging to the space group R-3m or a monoclinic crystal structure belonging to the space group C2 / m.

[0050] [How to confirm the crystal structure] The crystal structure of CAM can be confirmed by observation using a powder X-ray diffraction measurement device (for example, Ultima IV manufactured by Rigaku Corporation).

[0051] <CAM manufacturing method> The method for producing CAM includes a step of obtaining MCC and a step of obtaining CAM. The steps of obtaining MCC and CAM will be described below in this order.

[0052] [Process for obtaining MCC] First, prepare an MCC containing at least Ni and element X. The MCC may be any of a metal composite hydroxide, a metal composite oxide, and a mixture thereof. Hereinafter, the manufacturing method will be described in detail using an MCC containing Ni, Mn, and an element X as an example.

[0053] MCC can be produced by a co-precipitation method, which can be a batch co-precipitation method or a continuous co-precipitation method.

[0054] For example, by the continuous coprecipitation method described in JP-A-2002-201028, a nickel salt solution, a manganese salt solution, a metal salt solution of element X, and optionally a complexing agent are reacted to obtain Ni (1-y-w) Mn y X w A metal composite hydroxide represented by (OH)2 (y and w are the same as those in the above formula (I)) is produced.

[0055] As the nickel salt that is the solute of the nickel salt solution, for example, one or more of nickel sulfate, nickel nitrate, nickel chloride, and nickel acetate can be used.

[0056] As the manganese salt that is the solute of the manganese salt solution, for example, one or more of manganese sulfate, manganese nitrate, manganese chloride, and manganese acetate can be used.

[0057] As the metal salt of element X, which is the solute of the metal salt solution of element X, for example, titanium sulfate or zirconium sulfate can be used.

[0058] In this embodiment, a metal salt solution of element X is simultaneously wet-mixed with a nickel salt solution and a manganese salt solution to produce a mixed raw material solution. Through this process, the half-widths of I1 / I2, P1, and S1 can be adjusted to the above-mentioned ranges.

[0059] The metal salt solution of element X, the nickel salt solution, and the manganese salt solution are mixed in such a ratio that the molar ratio of Ni in the solute of the nickel salt solution, Mn in the solute of the manganese salt solution, and element X in the solute of the metal salt solution of element X corresponds to (1-yw):y:w.

[0060] In this process, the metal salt solution of element X and the manganese salt solution are mixed in such a ratio that the molar ratio (y / w) of Mn to element X is 1.05 or greater, more preferably 1.5 or greater, and even more preferably 3.0 or greater. If y / w is less than 1.05, i.e., if the metal salt solution of element X is mixed in an amount that is in excess of the manganese salt solution or the same amount as the manganese salt solution, impurities derived from element X that are not dissolved in the resulting metal composite hydroxide are likely to be generated. Using MCC containing such impurities may hinder charging of the lithium secondary battery, making it impossible to perform the desired charging. When the process is carried out under conditions where y / w is within the above-mentioned range, the generation of the above-mentioned impurities is suppressed, and the half-widths of I1 / I2, P1, and S1 can be adjusted to the above-mentioned ranges, resulting in the production of a lithium secondary battery that is capable of the desired charging and has excellent thermal stability.

[0061] In producing the mixed raw material solution, it is sufficient that y / w is within the above-mentioned range, and it is believed that the effects of the present invention can be achieved even if the y / w in formula (I) of the obtained CAM is not 1.05 or more. For example, CAM in which y / w in formula (I) is not 1.05 or more may be produced by adding a raw material containing Mn or element X in a process subsequent to the MCC production process.

[0062] The solvent of the nickel salt solution, manganese salt solution, and metal salt solution of element X is water. That is, the nickel salt solution, manganese salt solution, and metal salt solution of element X are aqueous solutions.

[0063] The pH of the mixed raw material liquid is 3 or less. By mixing a nickel salt solution, a manganese salt solution, and a metal salt solution of element X so that the pH of the mixed raw material solution is 3 or less, element X becomes less likely to oxidize and can be uniformly solid-dissolved with Ni and Mn. Here, "element X is less likely to oxidize" means that when an aqueous solution of a metal salt of element X is used, oxides of element X, in which ions of element X are oxidized, are less likely to be produced. As a result, MCC is obtained that has a variety of XO-Me bonds, XOX bonds, and Me-O-Me bonds, and CAM produced using such MCC as a raw material also has a variety of XO-Me bonds, XOX bonds, and Me-O-Me bonds. In other words, CAM can be obtained whose half-widths of I1 / I2, P1, and S1 are within the above-mentioned ranges. The pH of the mixed raw material solution can be adjusted by adjusting the types and concentrations of the nickel salt solution, the manganese salt solution, and the metal salt solution of element X. Alternatively, after preparing a mixed raw material solution having a pH of more than 3, an acid such as hydrochloric acid or sulfuric acid may be added to adjust the pH to a desired value.

[0064] The complexing agent is a compound capable of forming a complex with nickel ions, manganese ions, and ions of element X in an aqueous solution. Examples include ammonium ion donors, hydrazine, ethylenediaminetetraacetic acid, nitrilotriacetic acid, uracildiacetic acid, and glycine.

[0065] The amount of complexing agent contained in the mixed liquid containing the mixed raw material liquid and the complexing agent is, for example, a molar ratio of more than 0 and 2 or less to the total number of moles of metal salts (nickel salt, manganese salt, metal salt of element X).

[0066] Next, an alkaline solution is added to the mixture. The alkaline solution may be, for example, an aqueous solution of an alkali metal hydroxide. The alkali metal hydroxide may be, for example, sodium hydroxide or potassium hydroxide.

[0067] At this time, the alkaline solution is added so that the pH value in the reaction tank becomes preferably 9 to 13, more preferably 9.5 to 12.5, and even more preferably 10 to 12.

[0068] The pH value in this specification is defined as the value measured when the temperature of the mixed liquid or mixed raw material liquid is 30° C. If the temperature of the mixed liquid or mixed raw material liquid is not 30° C., the pH is measured after cooling or heating the mixed liquid or mixed raw material liquid sampled from the reaction tank to 30° C.

[0069] During the reaction, the temperature of the reaction vessel is controlled within the range of, for example, 20 to 80°C, preferably 30 to 70°C.

[0070] The materials in the reaction vessel are mixed by suitable stirring. The reaction vessel used in the continuous coprecipitation method may be a type that allows the formed reaction precipitate to overflow for separation.

[0071] In addition to controlling the above conditions, various gases, for example, inert gases such as nitrogen, argon, and carbon dioxide, oxidizing gases such as air and oxygen, or mixtures thereof may be supplied into the reaction vessel. Among the above, mixed gases are preferred from the viewpoint of facilitating adjustment of the oxygen concentration in the oxygen-containing gas.

[0072] After the above reaction, the resulting reaction precipitate is washed with water, and then dehydrated, isolated, and dried as appropriate to obtain MCC, a metal composite hydroxide. After drying, MCC may be classified as appropriate.

[0073] In the above example, a metal composite hydroxide is produced as MCC, but a metal composite oxide may also be prepared.

[0074] The metal composite oxide can be produced by oxidizing the metal composite hydroxide. The oxidation temperature is preferably 400 to 700° C. The oxidation time, which is the total time from the start of temperature increase to the end of temperature maintenance after the temperature is reached, is preferably 1 to 30 hours.

[0075] [CAM obtaining process] The process for obtaining CAM includes a mixing step of mixing MCC with a lithium compound, and a firing step of firing the resulting mixture.

[0076] ·Mixing process MCC and a lithium compound are mixed. The lithium compound may be at least one of lithium carbonate, lithium nitrate, lithium acetate, lithium hydroxide, lithium hydroxide hydrate, lithium oxide, lithium chloride, and lithium fluoride. Of these, lithium hydroxide, lithium hydroxide hydrate, and lithium carbonate, or a mixture thereof, is preferred.

[0077] The lithium compound and MCC are mixed in consideration of the composition ratio of the final target product to obtain a mixture of the lithium compound and MCC. The amount (molar ratio) of Li contained in the lithium compound relative to the total amount of elements other than oxygen contained in MCC (e.g., Ni, M1, element M2, element X) is preferably 0.9 to 1.25, more preferably 0.91 to 1.20, and even more preferably 0.92 to 1.15.

[0078] Firing process By firing the mixture of MCC and a lithium compound, crystals grow and CAM is obtained.

[0079] The firing may be a single firing or may include multiple firing steps. In the firing step, it is preferable to carry out pre-firing and then main firing at a temperature higher than that of the pre-firing.

[0080] The temperature during the calcination is, for example, in the range of 200 to 800°C, preferably 400 to 800°C, and more preferably 450 to 700°C.

[0081] The temperature during the main firing is preferably 600 to 1200°C, more preferably 650 to 1100°C, and even more preferably 700 to 1000°C.

[0082] In the firing step, the holding time at the pre-firing or main firing temperature is, for example, 0.1 to 20 hours, preferably 0.5 to 10 hours, The rate of temperature increase to the pre-firing or main firing temperature is, for example, 50 to 400°C / hour, and the rate of temperature decrease from the pre-firing or main firing temperature to room temperature is, for example, 10 to 400°C / hour.

[0083] The temperature rise rate in this specification is calculated from the time from when the temperature rise starts until the firing temperature is reached in the firing device, and the temperature difference from the temperature at which the temperature rise starts in the firing device to the firing temperature.

[0084] In the firing step, dry air, an oxygen atmosphere, an inert atmosphere, or a mixture of these may be used depending on the desired composition. In this embodiment, an oxygen atmosphere is preferred.

[0085] The calcination apparatus used for calcination is not particularly limited, and may be, for example, a continuous static calcination furnace or a fluidized bed calcination furnace. Examples of the continuous static calcination furnace include a tunnel kiln and a roller hearth kiln. Examples of the fluidized bed calcination furnace include a rotary kiln.

[0086] The fired product obtained in the firing step may be washed with a cleaning solution such as pure water or an alkaline cleaning solution.

[0087] The fired product after washing may be dried as appropriate.

[0088] Through the above steps, a CAM is obtained.

[0089] <Lithium secondary battery> A positive electrode for a lithium secondary battery suitable for use with the above-mentioned CAM will be described below. 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 a positive electrode will be described.

[0090] An example of a suitable lithium secondary battery for use with the above-mentioned CAM has a positive electrode, a negative electrode, a separator sandwiched between the positive electrode and the negative electrode, and an electrolyte solution disposed between the positive electrode and the negative electrode.

[0091] 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.

[0092] First, as shown in the partially 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 stacked in this order: separator 1, positive electrode 2, separator 1, negative electrode 3, and then wound to form an electrode group 4.

[0093] The positive electrode 2 includes, for example, a positive electrode active material layer 2a containing CAM and a positive electrode current collector 2b having the positive electrode active material layer 2a formed on one surface thereof. 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.

[0094] 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, and can be manufactured in the same manner as the positive electrode 2.

[0095] Next, the electrode group 4 and an insulator (not shown) are placed in the battery can 5, the bottom of the can is sealed, the electrode group 4 is impregnated with an electrolyte solution 6, and the electrolyte is disposed between the positive electrode 2 and the negative electrode 3. Furthermore, the top of the battery can 5 is sealed with a top insulator 7 and a sealing member 8, whereby a lithium secondary battery 10 can be manufactured.

[0096] The shape of the electrode group 4 can be, for example, a columnar shape such that the cross section of the electrode group 4 cut perpendicular to the winding axis is a circle, an ellipse, a rectangle, or a rectangle with rounded corners.

[0097] The shape of a lithium secondary battery having such an electrode group 4 can be any shape specified by IEC60086, a standard for batteries established by the International Electrotechnical Commission (IEC), or JIS C 8500. Examples of shapes include a cylindrical shape and a rectangular shape.

[0098] Furthermore, the lithium secondary battery is not limited to the above-mentioned wound type configuration, and may be a laminated type configuration in which a laminated structure of a positive electrode, a separator, a negative electrode, and a separator is repeatedly stacked. Examples of laminated lithium secondary batteries include so-called coin type batteries, button type batteries, and paper type (or sheet type) batteries.

[0099] The positive electrode, separator, negative electrode, and electrolyte constituting the lithium secondary battery can be, for example, the configuration, materials, and manufacturing method described in

[0113] to

[0140] of WO2022 / 113904A1.

[0100] <All-solid-state lithium secondary battery> The CAM of this embodiment can be used as a CAM for an all-solid-state lithium secondary battery.

[0101] 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. The all-solid-state lithium secondary battery 1000 may also have a bipolar structure in which a CAM and a negative electrode active material are disposed on both sides of a current collector. A specific example of a bipolar structure is the structure described in JP-A-2004-95400.

[0102] 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-mentioned CAM and solid electrolyte. The positive electrode active material layer 111 may also contain a conductive material and a binder.

[0103] 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. The negative electrode active material layer 121 may also contain a solid electrolyte and a conductive material.

[0104] 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.

[0105] The all-solid-state lithium secondary battery 1000 further includes an insulator (not shown) that insulates the laminate 100 from the exterior body 200 , and a sealing body (not shown) that seals the opening 200 a of the exterior body 200 .

[0106] A container molded from a highly corrosion-resistant metal material such as aluminum, stainless steel, or nickel-plated steel can be used as exterior body 200. Alternatively, a container formed into a bag shape from a laminate film with corrosion resistance applied to at least one surface can also be used as exterior body 200.

[0107] The all-solid-state lithium secondary battery 1000 may have any shape, such as a coin shape, a button shape, a paper shape (or a sheet shape), a cylindrical shape, a square shape, or a laminate shape (pouch shape).

[0108] The all-solid-state lithium secondary battery 1000 is illustrated as having one laminate 100 as an example, 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 (laminated bodies 100) are sealed inside an exterior body 200.

[0109] For the all-solid-state lithium secondary battery, for example, the configuration, materials, and manufacturing method described in

[0151] to

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

[0110] Furthermore, the positive electrode having the above-described configuration has the CAM having the above-described configuration, and therefore is capable of desired charging and has excellent thermal stability.

[0111] Furthermore, the lithium secondary battery having the above-described structure has the above-described positive electrode, and therefore can be charged as desired and has excellent thermal stability.

[0112] While the preferred embodiments of the present invention have been described above with reference to the accompanying drawings, the present invention is not limited to these examples. The shapes and combinations of the components shown in the above examples are merely examples, and various modifications can be made based on design requirements, etc., without departing from the spirit of the present invention. [Example]

[0113] Next, the present invention will be described in more detail with reference to examples.

[0114] <Method for measuring oxygen release rate> The oxygen release rate was measured by the method described in the above [Evaluation of thermal stability].

[0115] <Raman spectroscopy> The Raman spectroscopy was carried out by the method described above in [Raman spectroscopy]. The obtained spectra were analyzed by the methods described above in (Analysis 1) and (Analysis 2), respectively, to obtain I1 / I2, half-width of P1, and half-width of S1.

[0116] <Composition analysis> The composition of the CAM was analyzed by the method described above in [Composition Analysis].

[0117] <Confirmation of crystal structure> The crystal structure of CAM was confirmed according to the above [Method for confirming crystal structure].

[0118] Example 1 (CAM1 manufacturing) Water was placed in a reaction vessel equipped with a stirrer and an overflow pipe, and then an aqueous solution of sodium hydroxide was added thereto, and the liquid temperature was maintained at 50°C.

[0119] A mixed raw material solution 1 was prepared by mixing an aqueous nickel sulfate solution, an aqueous manganese sulfate solution, and an aqueous titanium sulfate solution in a molar ratio of Ni, Mn, and Ti of 0.8:0.2:0.01 to have a pH of 1.9 (measurement temperature: 30°C).

[0120] Next, in the reaction vessel, an aqueous ammonium sulfate solution was continuously added as a complexing agent to the mixed raw material liquid 1 under stirring. Furthermore, an aqueous sodium hydroxide solution was added dropwise at appropriate times under the condition that the pH of the mixed liquid in the reaction vessel became 12 (measurement temperature: 30°C), and a reaction precipitate 1 was obtained.

[0121] The resulting reaction precipitate 1 was washed, dehydrated using a centrifuge, isolated, and dried at 105°C for 20 hours to obtain MCC1, a metal composite hydroxide.

[0122] Lithium hydroxide monohydrate powder was weighed out in a proportion such that the molar ratio of Li / (Ni+Mn+Ti)=1.05, and mixed with MCC1 to obtain mixture 1.

[0123] Mixture 1 was pre-baked in an oxygen atmosphere at 650°C for 5 hours, and then further baked in an oxygen atmosphere at 850°C for 5 hours, and washed with pure water to obtain CAM1. Composition analysis of CAM1 revealed that in formula (I), a = 0.02, y = 0.20, z = 0, w = 0.01, M1 = Mn, and X = Ti.

[0124] (CAM1 evaluation) CAM1 had a layered structure. The I1, I2, I1 / I2, half-width of P1, half-width of S1, and oxygen release rate of CAM are shown in Table 1. The same is true for the following examples.

[0125] <Example 2> (CAM2 Manufacturing) Water was placed in a reaction vessel equipped with a stirrer and an overflow pipe, and then an aqueous solution of sodium hydroxide was added thereto, and the liquid temperature was maintained at 50°C.

[0126] A mixed raw material solution 2 was prepared by mixing an aqueous solution of nickel sulfate, an aqueous solution of manganese sulfate, and an aqueous solution of titanium sulfate in a molar ratio of Ni, Mn, and Ti of 0.8:0.15:0.05 to a pH of 1.3 (measurement temperature: 30°C).

[0127] CAM2 was obtained in the same manner as in Example 1, except that mixed raw material liquid 2 was used instead of mixed raw material liquid 1 and lithium hydroxide monohydrate powder was weighed out in a proportion such that the molar ratio was Li / (Ni+Mn+Ti) = 1.15. CAM2 had a layered structure. Composition analysis of CAM2 showed that in formula (I), a = 0.06, y = 0.16, z = 0, w = 0.05, M1 = Mn, and X = Ti.

[0128] Example 3 (CAM3 manufacturing) Water was placed in a reaction vessel equipped with a stirrer and an overflow pipe, and then an aqueous solution of sodium hydroxide was added thereto, and the liquid temperature was maintained at 50°C.

[0129] A mixed raw material solution 3 was prepared by mixing an aqueous nickel sulfate solution, an aqueous manganese sulfate solution, and an aqueous zirconium sulfate solution in a molar ratio of Ni, Mn, and Zr of 0.8:0.2:0.01 to a pH of 2.3 (measurement temperature: 30°C).

[0130] CAM3 was obtained in the same manner as in Example 1, except that mixed raw material liquid 3 was used instead of mixed raw material liquid 1 and lithium hydroxide monohydrate powder was weighed out in a molar ratio of Li / (Ni+Mn+Zr) = 1.05. CAM3 had a layered structure. Composition analysis of CAM3 showed that in formula (I), a = 0.02, y = 0.19, z = 0, w = 0.01, M1 = Mn, and X = Zr.

[0131] <Comparative Example 1> (CAM-C1 manufacturing) Water was placed in a reaction vessel equipped with a stirrer and an overflow pipe, and then an aqueous solution of sodium hydroxide was added thereto, and the liquid temperature was maintained at 50°C.

[0132] A mixed raw material liquid C1 was prepared by mixing an aqueous nickel sulfate solution and an aqueous manganese sulfate solution in a molar ratio of Ni to Mn of 0.8:0.2 to a pH of 4.8 (measurement temperature: 30° C.).

[0133] Next, an aqueous solution of ammonium sulfate was continuously added as a complexing agent to the mixed raw material solution C1 in the reaction vessel under stirring. An aqueous solution of sodium hydroxide was added dropwise at appropriate times under the condition that the pH of the mixed solution in the reaction vessel became 10.9 (measurement temperature: 30°C), and a reaction precipitate C1 was obtained.

[0134] The resulting reaction precipitate C1 was washed, dehydrated using a centrifuge, isolated, and dried at 105°C for 20 hours to obtain a metal composite hydroxide, MCC-C1.

[0135] Lithium hydroxide monohydrate powder was weighed out in a molar ratio of Li / (Ni+Mn)=1.05 and mixed with MCC-C1 to obtain a mixture C1.

[0136] The mixture C1 was pre-baked in an oxygen atmosphere at 650°C for 5 hours, and then further baked in an oxygen atmosphere at 850°C for 5 hours. After washing with pure water, CAM-C1 was obtained.

[0137] (CAM-C1 evaluation) CAM-C1 had a layered structure. As a result of composition analysis of CAM-C1, in formula (I), a = -0.01, y = 0.20, z = 0, w = 0, and M1 = Mn. I1, I2, I1 / I2, half-width of P1, half-width of S1, and oxygen release rate of CAM are shown in Table 2. The following comparative examples are also similarly shown in Table 2.

[0138] <Comparative Example 2> (CAM-C2 manufacturing) Lithium hydroxide monohydrate powder and titanium oxide powder were weighed out relative to the Ni and Mn contained in MCC-C1 in a molar ratio of Li:(Ni+Mn):Ti=1.05:1:0.01, and mixed with MCC-C1 to obtain mixture C2.

[0139] CAM-C2 was obtained by the same procedure as in Comparative Example 1, except that mixture C2 was used instead of mixture C1. CAM-C2 had a layered structure. Composition analysis of CAM-C2 revealed that in formula (I), a = -0.01, y = 0.20, z = 0, w = 0.01, M1 = Mn, and X = Ti.

[0140] <Comparative Example 3> (CAM-C3 manufacturing) Lithium hydroxide monohydrate powder and zirconium oxide powder were weighed out relative to the Ni and Mn contained in MCC-C1 in a molar ratio of Li:(Ni+Mn):Zr=1.05:1:0.01, and mixed with MCC-C1 to obtain mixture C3.

[0141] CAM-C3 was obtained by the same procedure as in Comparative Example 1, except that mixture C3 was used instead of mixture C1. CAM-C3 had a layered structure. Composition analysis of CAM-C3 revealed that in formula (I), a = -0.06, y = 0.19, z = 0, w = 0.01, M1 = Mn, and X = Zr.

[0142] <Comparative Example 4> (CAM-C4 manufacturing) Water was placed in a reaction vessel equipped with a stirrer and an overflow pipe, and then an aqueous solution of sodium hydroxide was added thereto, and the liquid temperature was maintained at 50°C. A titanium sulfate aqueous solution was mixed with the mixed raw material liquid C1 in a molar ratio of Ti / (Ni+Mn)=0.01 to prepare a mixed raw material liquid C4 having a pH of 8.4 (measurement temperature: 30° C.).

[0143] CAM-C4 was obtained in the same manner as in Example 1, except that mixed raw material liquid C4 was used instead of mixed raw material liquid 1. CAM-C4 had a layered structure. Composition analysis of CAM-C4 revealed that in formula (I), a = -0.01, y = 0.19, z = 0, w = 0.01, M1 = Mn, and X = Ti.

[0144] <Comparative Example 5> (CAM-C5 manufacturing) Water was placed in a reaction vessel equipped with a stirrer and an overflow pipe, and then an aqueous solution of sodium hydroxide was added thereto, and the liquid temperature was maintained at 50°C.

[0145] A mixed raw material solution C5 was prepared by mixing an aqueous solution of nickel sulfate, an aqueous solution of manganese sulfate, and an aqueous solution of titanium sulfate in a molar ratio of Ni, Mn, and Ti of 0.8:0.2:0.01, and then adding an aqueous solution of sodium hydroxide to the mixed solution to adjust the pH to 5.8 (measurement temperature: 30°C).

[0146] CAM-C5 was obtained in the same manner as in Example 1, except that mixed raw material liquid C5 was used instead of mixed raw material liquid 1. CAM-C5 had a layered structure. As a result of composition analysis of CAM-C5, in formula (I), a = 0.02, y = 0.20, z = 0, w = 0.01, M1 = Mn, and X = Ti.

[0147] <Comparative Example 6> (CAM-C6 manufacturing) Water was placed in a reaction vessel equipped with a stirrer and an overflow pipe, and then an aqueous solution of sodium hydroxide was added thereto, and the liquid temperature was maintained at 50°C.

[0148] A mixed raw material solution C6 was prepared by mixing an aqueous solution of nickel sulfate, an aqueous solution of manganese sulfate, and an aqueous solution of titanium sulfate in a ratio of Ni:Mn:Ti of 0.9:0.05:0.05 to a pH of 1.4 (measurement temperature: 30°C).

[0149] CAM-C6 was obtained in the same manner as in Example 1, except that mixed raw material liquid C6 was used instead of mixed raw material liquid 1. CAM-C6 had a layered structure. Composition analysis of CAM-C6 revealed that in formula (I), a = -0.02, y = 0.05, z = 0, w = 0.05, M1 = Mn, and X = Ti.

[0150] [Table 1]

[0151] [Table 2]

[0152] As shown in Table 1 above, when MCC was used as a raw material for element X, which had undergone a process of simultaneously wet-mixing a metal salt solution of element X with other solutions (a nickel sulfate aqueous solution and a manganese sulfate aqueous solution) at a predetermined ratio so that the pH was 3 or less to produce a mixed raw material solution, CAM was obtained whose I1 / I2, half-width of P1, and half-width of S1 were within the ranges of the present invention. A lithium secondary battery using the obtained CAM could be charged up to 220 mAh / g, and its oxygen release rate was 1.1 mass% / min or less. In other words, the battery was capable of desired charging and had excellent thermal stability.

[0153] On the other hand, the CAM of Comparative Example 1 did not contain element X, and therefore the P1 peak intensity was small, and the I1 / I2 ratio was less than 1.25. Furthermore, since there was no peak derived from element X, the half-width of S1 was also small. Although the lithium secondary battery using this CAM was able to be charged as desired, the oxygen release rate exceeded 1.1% by mass / min, and the thermal stability was poor.

[0154] The CAMs of Comparative Examples 2 and 3, which were obtained by adding TiO2 or ZrO2 in the mixing step, had a small P1 peak intensity and an I1 / I2 ratio of less than 1.25. Although the lithium secondary battery using this CAM was able to charge as desired, the oxygen release rate exceeded 1.1 mass% / min and the thermal stability was poor. This is believed to be due to the small amount of element X in solid solution.

[0155] The CAM of Comparative Example 4, in which Ti(SO4)2 was added after mixing the nickel salt solution and the manganese salt solution, exhibited a small P1 peak intensity and an I1 / I2 ratio of less than 1.25. Although the lithium secondary battery using this CAM was able to charge as desired, the oxygen release rate exceeded 1.1 mass% / min, and the thermal stability was poor. This is believed to be due to the small amount of element X in solid solution.

[0156] The CAM of Comparative Example 5 obtained using a mixed raw material solution having a pH exceeding 5 had an I1 / I2 ratio of less than 1.25. Furthermore, the lithium secondary battery using the obtained CAM could not be charged up to 220 mAh / g even when constant-current / constant-voltage charging was performed under the conditions described in the above [Evaluation of Thermal Stability], and the desired charging performance for the battery was not possible. Furthermore, since charging up to 220 mAh / g was not possible, the oxygen release rate could not be measured. This is thought to be because the raw material containing element X precipitated, preventing element X from forming a solid solution.

[0157] The CAM of Comparative Example 6, obtained by mixing a manganese sulfate aqueous solution and a titanium sulfate aqueous solution at a Mn to Ti ratio of less than 1.05 during production of the mixed raw material solution, had an I1 / I2 ratio exceeding 3.00. A lithium secondary battery using the obtained CAM could not be charged up to 220 mAh / g even when subjected to constant-current, constant-voltage charging under the conditions described in the above [Evaluation of thermal stability], and the desired charging performance for the battery was not possible. Furthermore, since charging up to 220 mAh / g was not possible, the oxygen release rate could not be measured. This is thought to be because, during production of the mixed raw material solution, an excess amount of titanium sulfate aqueous solution was added compared to the manganese salt solution, resulting in the generation of Ti-derived impurities that could not form a solid solution in the resulting metal composite hydroxide. [Explanation of symbols]

[0158] 1: separator, 2: positive electrode, 2a: positive electrode active material layer, 2b: positive electrode current collector layer, 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 having a layered structure, comprising at least Li, Ni, and an element X, the element X is one or more elements selected from the group consisting of Ti and Zr, The Raman spectrum obtained by Raman spectroscopy at an excitation wavelength of 532 nm was peak-fitted using a Lorentz function. －１ 560cm or more －１ The peak present below P1, 560 cm －１ More than 600cm －１ A positive electrode active material for a lithium secondary battery, wherein, when a peak present below is designated as P2, the maximum peak intensity I1 of P1 relative to the maximum peak intensity I2 of P2 is 1.25 or more and 3.00 or less.

2. The half width of P1 is 40 cm －１ Over 57cm －１ The positive electrode active material for a lithium secondary battery according to claim 1, wherein:

3. In the Raman spectrum, －１ More than 700cm －１ When the spectrum below is designated as S1, the half width of S1 is 135 cm －１ 170cm or more －１ The positive electrode active material for a lithium secondary battery according to claim 1 or 2, wherein:

4. The positive electrode active material for a lithium secondary battery according to claim 1 or 2, which is represented by the following formula (I): Li[i ａ (e) （１－ｙ－ｚ－ｗ） 71 ｙ 72 ｚ 8 ｗ ) ) １－ａ )) ２ (9) (In formula (I), −0.1≦a≦0.2, 0≦y≦0.9, 0≦z≦0.9, 0<w≦0.1, and y+z+w<1; M1 is one or more elements selected from the group consisting of Co and Mn; M2 is one or more elements selected from the group consisting of Fe, Cu, Mg, Al, W, Mo, Nb, Zn, Sn, Ga, B, and V; and X is one or more elements selected from the group consisting of Ti and Zr.)

5. 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.

6. A lithium secondary battery comprising the positive electrode for lithium secondary batteries according to claim 5.

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