Method for producing positive electrode active material for non-aqueous electrolyte secondary battery, positive electrode active material for non-aqueous electrolyte secondary battery, non-aqueous electrolyte secondary battery

Abstract

The present invention is a method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery, the method including: a first sintering step in which heat treatment is applied to a nickel-containing hydroxide; a mixing step in which a sintered material obtained from the first sintering step and a lithium-containing compound are mixed together; and a second sintering step in which heat treatment is applied to a mixed material obtained from the mixing step at a temperature of 600-900°C. The method is characterized in that: the nickel-containing hydroxide is represented by the composition formula Ni(1 − x − y − z)Mn × AlyMz(OH)2 (where 0 < x < 0.03, 0 ≤ y ≤ 0.05, 0 ≤ z < 0.1, and x + y + z ≤ 0.1); and the heating temperature in the first sintering step is 350-600°C.

Description

Method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery, positive electrode active material for a non-aqueous electrolyte secondary battery, and non-aqueous electrolyte secondary battery

[0001] This disclosure relates to a method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery, a positive electrode active material for a non-aqueous electrolyte secondary battery, and a non-aqueous electrolyte secondary battery.

[0002] Secondary batteries such as lithium-ion batteries are widely used in applications requiring high capacity, high durability, and high output, such as automotive and energy storage applications. The positive electrode active material, which is a major component of non-aqueous electrolyte secondary batteries, greatly affects these performance characteristics, and therefore, much research has been conducted on positive electrode active materials. For example, Patent Document 1 discloses a method for producing a positive electrode active material, which involves oxidizing a hydroxide containing Ni and Mn at a temperature of 600°C or higher and 1100°C or lower, mixing the obtained oxide with a Li-containing compound, and then firing it.

[0003] Patent No. 5008328

[0004] In recent years, lithium transition metal composite oxides with high Ni content have attracted attention as positive electrode active materials that enable higher battery capacity. However, when lithium transition metal composite oxides with high Ni content are used as positive electrode active materials, battery resistance tends to increase. Furthermore, when Mn is added to lithium transition metal composite oxides with high Ni content, for example, to improve heat resistance, the spinel phase tends to precipitate. Therefore, depending on the manufacturing conditions, crystallinity may decrease, leading to a decrease in battery capacity or increased resistance. Thus, when using lithium transition metal composite oxides with high Ni content, it is an important challenge to achieve high battery capacity while simultaneously reducing resistance and improving thermal stability.

[0005] A method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery, according to one aspect of the present disclosure, comprises: a first calcination step of heat-treating a Ni-containing hydroxide; a mixing step of mixing the calcined product obtained in the first calcination step with a Li-containing compound; and a second calcination step of heat-treating the mixture obtained in the mixing step at a temperature of 600°C or higher and 900°C or lower, wherein the Ni-containing hydroxide has the compositional formula Ni （１－ｘ－ｙ－ｚ） Mn ｘ Al ｙM ｚ (OH) ２ (0 < x < 0.03, 0 ≤ y ≤ 0.05, 0 ≤ z < 0.1, x + y + z ≤ 0.1, M is at least one element selected from the group consisting of Co, Ti, Nb, Si, Mo, Zr, V, Fe, Mg, Cr, Cu, Sn, Ta, W, Na, K, Ba, Sr, Bi, Be, Zn, Ca, and B), and the heating temperature in the first firing step is 350°C or higher and 600°C or lower.

[0006] Further, the positive electrode active material for a non-aqueous electrolyte secondary battery, which is one aspect of the present disclosure, has a composition formula LiNi （１－ｘ－ｙ－ｚ） Mn ｘ Al ｙ M ｚ O ２ (0 < x < 0.03, 0 ≤ y ≤ 0.05, 0 ≤ z < 0.1, x + y + z ≤ 0.1, M is at least one element selected from the group consisting of Co, Ti, Nb, Si, Mo, Zr, V, Fe, Mg, Cr, Cu, Sn, Ta, W, Na, K, Ba, Sr, Bi, Be, Zn, Ca, and B), and is a positive electrode active material for a non-aqueous electrolyte secondary battery containing a lithium transition metal composite oxide. In the volume-based particle size distribution of the particles of the lithium transition metal composite oxide, the particle size at which the cumulative frequency becomes 10% from the smaller particle size is defined as D10, the particle size at which the cumulative frequency becomes 50% from the smaller particle size is defined as D50, and the particle size at which the cumulative frequency becomes 90% from the smaller particle size is defined as D90. When the value of {(D90 - D10) / D50} is 0.9 or less, and in the X-ray diffraction pattern obtained by powder X-ray diffraction of the lithium transition metal composite oxide, the integrated intensity I of peak A appearing in the range of 2θ = 43° ± 1° Ａ with respect to the integrated intensity I of peak B appearing in the range of 35° ± 1° Ｂ The ratio (I Ｂ / I Ａ ) is 0.1 or less.

[0007] Further, a non-aqueous electrolyte secondary battery, which is one aspect of the present disclosure, includes a positive electrode containing the above positive electrode active material, a negative electrode, and a non-aqueous electrolyte.

[0008] According to a method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery, which is one aspect of this disclosure, a positive electrode active material can be obtained that can achieve high battery capacity while also achieving low resistance and improved thermal stability.

[0009] This is an axial cross-sectional view of a non-aqueous electrolyte secondary battery, which is an example of an embodiment.

[0010] The present disclosure provides a method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery, comprising: a crystallization step to obtain a Ni-containing hydroxide; a first calcination step to heat-treat and oxidize the Ni-containing hydroxide; a mixing step to mix the calcined product obtained in the first calcination step with a Li-containing compound; a second calcination step to heat-treat the mixture obtained in the mixing step; a water washing step to wash the calcined product obtained in the second calcination step with water; and a drying step to dry the wet powder obtained in the water washing step to obtain a lithium transition metal composite oxide.

[0011] [Crystallization Process] In the crystallization process, for example, while stirring a solution of a metal salt containing Ni, Mn, and an arbitrary metal element (Al, Co, etc.), an alkaline solution such as sodium hydroxide is added dropwise to adjust the pH to the alkaline side (for example, 8.5 or higher and 12.5 or lower), thereby precipitating (coprecipitation) a composite hydroxide (Ni-containing hydroxide) containing Ni, Mn, and an arbitrary metal element. However, the method for producing the Ni-containing hydroxide is not limited to this.

[0012] Here, the Ni-containing hydroxide has the compositional formula Ni （１－ｘ－ｙ－ｚ） Mn ｘ Al ｙ M ｚ (OH) ２ This is represented by (0 < x < 0.03, 0 ≤ y ≤ 0.05, 0 ≤ z < 0.1, x + y + z ≤ 0.1, where M is at least one element selected from the group consisting of Co, Ti, Nb, Si, Mo, Zr, V, Fe, Mg, Cr, Cu, Sn, Ta, W, Na, K, Ba, Sr, Bi, Be, Zn, Ca, and B). The content of the elements constituting the Ni-containing hydroxide can be measured by inductively coupled plasma atomic emission spectrometer (ICP-AES).

[0013] The Ni content of the Ni-containing hydroxide is 90 mol% or more, and may be 91 mol% or more, or 92 mol% or more, relative to the total number of moles of metal elements. The higher the Ni content, the easier it is to achieve higher battery capacity. The upper limit of the Ni content of the Ni-containing hydroxide is, for example, 99 mol%, from the viewpoint of including a predetermined amount of Mn and achieving high heat resistance.

[0014] The Mn content of Ni-containing hydroxide is preferably more than 0 mol% and less than 3 mol%, more preferably 0.5 mol% or more and less than 3 mol%, and more preferably 1 mol% or more and less than 3 mol%, relative to the total number of moles of metal elements. In other words, Mn is an essential component in Ni-containing hydroxide. By including more than 0 mol% and less than 3 mol% of Mn, when the final lithium transition metal composite oxide is used as the positive electrode, a battery with high capacity, low resistance, and excellent thermal stability can be realized. In other words, in lithium transition metal composite oxides with a high Ni content, if Mn is not included, or if the Mn content is 3 mol% or more, for example, the battery capacity tends to decrease or the battery resistance tends to increase.

[0015] The Al content in Ni-containing hydroxide is preferably between 0 mol% and 5 mol%, more preferably between 0 mol% and 3 mol%, and more preferably between 0 mol% and 2 mol%, relative to the total number of moles of metal elements. In other words, Al is an optional component in Ni-containing hydroxide. The inclusion of Al in the final lithium transition metal composite oxide makes it easier to stabilize the crystal structure. As a result, for example, it becomes easier to achieve higher capacity batteries.

[0016] The content of M (where M is at least one element selected from the group consisting of Co, Ti, Nb, Si, Mo, Zr, V, Fe, Mg, Cr, Cu, Sn, Ta, W, Na, K, Ba, Sr, Bi, Be, Zn, Ca, and B) in the Ni-containing hydroxide is preferably 0 mol% or more and less than 10 mol%, preferably 0 mol% or more and 7 mol% or less, and more preferably 0 mol% or more and 5 mol% or less, relative to the total number of moles of metal elements. In other words, in the Ni-containing hydroxide, M is an optional component. Among the above M, it is preferable that it contains Co. The lithium transition metal composite oxide finally obtained contains Co, which can improve, for example, the battery resistance.

[0017] [First Firing Process] In the first firing process, the Ni-containing hydroxide obtained in the crystallization process is heat-treated to obtain a fired product. At this time, the heating temperature in the first firing process is set to 350°C or higher and 600°C or lower. This oxidizes the Ni-containing hydroxide, and a Ni-containing oxide is obtained. Then, in the second firing process, a mixture of the Ni-containing oxide and the Li-containing compound is heat-treated to obtain a lithium transition metal composite oxide with a stabilized crystal structure.

[0018] The heating temperature in the first firing step may be 350°C or higher, but it may also be 370°C or higher, or even 400°C or higher. If the heating temperature in the first firing step is less than 350°C, the Ni-containing hydroxide obtained in the crystallization step will not be sufficiently oxidized, and the crystallinity of the final lithium transition metal composite oxide will tend to deteriorate. As a result, the battery capacity may decrease, and the thermal stability may decrease. In addition, the cycle characteristics may deteriorate due to the deterioration of crystallinity.

[0019] The heating temperature in the first firing process may be 600°C or lower, but may also be 570°C or lower, or 550°C or lower. If the heating temperature in the first firing process is too high, the spinel phase is more likely to precipitate. This is particularly pronounced when Mn is included in lithium transition metal composite oxides with a high Ni content. As a result, a decrease in battery capacity and increased resistance are likely to occur. Therefore, the heating temperature in the first firing process should be 350°C or higher and 600°C or lower, but may also be 370°C or higher and 570°C or lower, or 400°C or higher and 550°C or lower. Note that the heating temperature refers to the maximum temperature during heat treatment.

[0020] In the first firing process, firing is performed under an oxygen stream. The heating rate is, for example, 0.2°C / min or more and 15.0°C / min or less. When the heating rate is within the above range, the crystal structure is more easily stabilized. As a result, it becomes easier to achieve high capacity while simultaneously lowering resistance and improving cycle characteristics. Note that multiple heating rates may be set for each temperature range, and there may be one or more uniform heating zones within each temperature range.

[0021] The heating time (holding time) at the maximum temperature may be, for example, 1 hour or more and 15 hours or less, or 2 hours or more and 10 hours or less. When the heating time at the maximum temperature is within the above range, the crystal structure becomes more stable.

[0022] In the first calcination step, other compounds may be added to the Ni-containing hydroxide and heat treatment may be performed. Examples of compounds to be added include compounds containing at least one of phosphates, sulfates, oxides, hydroxides, and chlorides, which contain at least one element selected from the group consisting of Sr, Ti, Bi, Zr, Ba, Nb, Mg, Ca, V, Al, Mo, and W. An example of such a compound is Sr(OH) ２ SrO, SrCl ２ , TiO ２ , Ti(OH) ４ , Bi ２ O ４ , Bi(OH) ３ , ZrSO ４ , ZrO ２ , BaO, Ba(OH)２ , Nb ２ O ５ , Nb(OH) ２ , MgO, Mg(OH) ２ MgCl ２ , CaO, Ca(OH) ２ CaCl ２ , VO, V ２ O ５ Al ２ O ３ Al(OH) ３ Al ２ (SO) ４、 NaAl(OH) ４ AlPO ４ MoO ２ WO ３ WS ２ These are some examples. The compounds may be used individually or in combination of two or more. Furthermore, these compounds may be added during the mixing process described later.

[0023] Here, the maximum peak value of the X-ray diffraction pattern obtained by powder X-ray diffraction of the Ni-containing hydroxide obtained in the crystallization process is I. １ The maximum peak value of the X-ray diffraction pattern obtained by powder X-ray diffraction of the calcined product obtained in the first calcination process is I ２ Let it be so. In that case, {(I ２ -I １ ) / (I ２ +I １ The value expressed as )} (hereinafter sometimes referred to as the "degree of oxidation of the fired product") is preferably 0.9 or higher, and more preferably 0.95 or higher.

[0024] The above {(I ２ -I １ ) / (I ２ +I １The value represented by )} indicates the proportion of oxides (Ni-containing oxides) in the calcined product after the first calcination process. As the value approaches 1, it means that the proportion of oxides is increasing and the proportion of hydroxides is decreasing. As a result of the inventors' investigations, it was found that by performing the second calcination process at a predetermined temperature while ensuring that the oxidation degree of the calcined product is 0.9 or higher, a lithium transition metal composite oxide with a more stable crystal structure can be obtained.

[0025] The X-ray diffraction patterns of the Ni-containing hydroxide and the calcined product after the first calcination process are obtained using a desktop X-ray diffractometer (manufactured by Rigaku Corporation, product name "MiniFlex 600"). The diffracted X-rays are detected by a high-speed one-dimensional detector (D / teX Ultra 2). The measurement conditions for the X-ray diffractometer are as follows: X-ray source: CuKα ray Tube voltage: 40kV Tube current: 15mA Divergent slit (DS): 0.625° Scattering slit (SS): 13mm (open) Receiving slit (RS): 8mm Scan axis: 2θ / θ Scanning method: Continuous 2θ scan range: 10-80° Scan speed: 10° / min Step width: 0.02°

[0026] [Mixing Process] In the mixing process, the calcined product (Ni-containing oxide) obtained in the first calcination process is mixed with a Li-containing compound. Examples of Li-containing compounds include Li ２ CO ３ LiOH, Li ２ O ２ Li ２ O, LiNO ３ LiNO ２ Li ２ SO ４ LiOH H ２ Examples include O, LiH, and LiF. The mixing ratio of the calcined product and the Li-containing compound is preferably such that the molar ratio of the total amount of metal elements in the calcined product to Li is in the range of 1:0.8 to 1.2, and is particularly preferably 1:1.0 to 1.1.

[0027] [Second firing process] In the second firing process, the mixture obtained in the mixing process is heat-treated to obtain a fired product. At this time, the heating temperature in the second firing process is set to 600°C or higher and 900°C or lower. By setting the heating temperature in the first firing process to 350°C or higher and 600°C or lower, and the heating temperature in the second firing process to 600°C or higher and 900°C or lower, a lithium transition metal composite oxide with a stabilized crystal structure can be obtained.

[0028] In the second firing process, firing is carried out under an oxygen stream, similar to the first firing process. The heating rate during firing may be, for example, 0.2°C / min or more and 15.0°C / min or less, or 0.3°C / min or more and 10.0°C / min or less. The firing time (holding time) at the maximum temperature may be, for example, 1 hour or more and 10 hours or 2 hours or more and 8 hours or less. Multiple heating rates may be set for each temperature range, and there may be one or more uniform heating zones within each temperature range.

[0029] [Water Washing Process] In the water washing process, the slurry obtained by mixing the calcined product obtained in the second calcination process with water or an aqueous solution is stirred and washed with water. Before the water washing process, unreacted Li-containing compounds (e.g., lithium carbonate, etc.) used during mixing may remain on the particle surface of the calcined product. By performing the water washing process, unreacted Li-containing compounds remaining on the particle surface of the lithium transition metal composite oxide can be removed.

[0030] Washing is carried out by known methods. For example, the calcined material and water or an aqueous solution are placed in a reaction vessel equipped with a stirring device and stirred. In the washing process, the slurry produced in the washing process is separated into solid and liquid to obtain a cake-like wet powder. The method of solid-liquid separation is not particularly limited and is carried out by known methods. For example, a suction filter, centrifuge, or filter press can be used for solid-liquid separation.

[0031] [Drying Process] In the drying process, the wet powder obtained in the washing process is dried to obtain dry powder (lithium transition metal composite oxide). In the drying process, for example, from the viewpoint of suppressing deterioration of battery characteristics when used as a positive electrode active material, it is preferable to dry until the moisture content is 1.0% by mass or less. The drying conditions are preferably such that the drying is performed at a temperature of 100°C or higher and 300°C or lower. The drying time is preferably 0.5 hours or more.

[0032] A non-aqueous electrolyte secondary battery to which the positive electrode active material produced by the above manufacturing method is applied can be obtained, for example, by housing an electrode body, in which electrodes (positive electrode, negative electrode) and a separator are stacked or wound together, in an outer casing such as an outer can or laminate together with a non-aqueous electrolyte.

[0033] Hereinafter, an example of an embodiment of the non-aqueous electrolyte secondary battery according to this disclosure will be described in detail with reference to Figure 1. Figure 1 is an axial cross-sectional view of a cylindrical non-aqueous electrolyte secondary battery, which is an example of an embodiment. Hereinafter, a cylindrical battery in which a wound electrode body 14 is housed in a bottomed cylindrical outer casing 16 is given as an example of a non-aqueous electrolyte secondary battery, but the outer casing of the battery is not limited to a cylindrical outer casing. The non-aqueous electrolyte secondary battery according to this disclosure may be, for example, a prismatic battery with a prismatic outer casing, a coin-type battery with a coin-type outer casing, or a pouch-type battery with an outer casing made of a laminate sheet including a metal layer and a resin layer. Furthermore, the electrode body is not limited to a wound type, and may be a laminated electrode body in which a plurality of positive electrodes and a plurality of negative electrodes are alternately stacked with a separator in between. Furthermore, the design of the non-aqueous electrolyte secondary battery according to this disclosure is not limited to the example design of the non-aqueous electrolyte secondary battery, and known designs of non-aqueous electrolyte secondary batteries may be applied.

[0034] As shown in Figure 1, the non-aqueous electrolyte secondary battery 10 comprises a wound electrode body 14, a non-aqueous electrolyte (not shown), and an outer casing 16 that houses the electrode body 14 and the non-aqueous electrolyte. The electrode body 14 includes a positive electrode 11, a negative electrode 12, and a separator 13, and has a wound structure in which the positive electrode 11 and the negative electrode 12 are wound in a spiral shape via the separator 13. The outer casing 16 is a bottomed cylindrical metal container with one side open in the axial direction, and the opening of the outer casing 16 is sealed by a sealing body 17. For the sake of explanation, the side of the battery with the sealing body 17 will be referred to as "upper," and the bottom side of the outer casing 16 will be referred to as "lower."

[0035] The positive electrode 11, negative electrode 12, and separator 13 constituting the electrode body 14 are all rectangular elongated bodies that are alternately stacked in the radial direction of the electrode body 14 by being wound in a spiral shape in the longitudinal direction. The separator 13 separates the positive electrode 11 and the negative electrode 12 from each other. The negative electrode 12 is formed to be slightly larger in dimensions than the positive electrode 11 in order to prevent lithium deposition. That is, the negative electrode 12 is formed to be longer in both the longitudinal and transverse directions than the positive electrode 11. The two separators 13 are formed to be at least slightly larger in dimensions than the positive electrode 11 and are arranged, for example, to sandwich the positive electrode 11. The electrode body 14 includes a positive electrode lead 20 connected to the positive electrode 11 by welding or the like, and a negative electrode lead 21 connected to the negative electrode 12 by welding or the like. In the electrode body 14, the longitudinal direction of the positive electrode 11 and the negative electrode 12 is the winding direction, and the transverse direction of the positive electrode 11 and the negative electrode 12 is the axial direction. In other words, the end faces in the short direction of the positive electrode 11 and the negative electrode 12 form the axial end faces of the electrode body 14.

[0036] Insulating plates 18 and 19 are positioned above and below the electrode body 14, respectively. In the example shown in Figure 1, the positive electrode lead 20 extends through a through-hole in the insulating plate 18 towards the sealing body 17, and the negative electrode lead 21 extends outside the insulating plate 19 towards the bottom of the outer casing 16. The positive electrode lead 20 is connected to the lower surface of the internal terminal plate 23 of the sealing body 17 by welding or the like, and the cap 27, which is the top plate of the sealing body 17 and is electrically connected to the internal terminal plate 23, becomes the positive electrode terminal. The negative electrode lead 21 is connected to the bottom inner surface of the outer casing 16 by welding or the like, and the outer casing 16 becomes the negative electrode terminal.

[0037] A gasket 28 is provided between the outer casing 16 and the sealing body 17 to ensure airtightness inside the battery. The outer casing 16 has a grooved portion 22 formed on its side surface, which protrudes inward to support the sealing body 17. The grooved portion 22 is preferably formed in an annular shape along the circumferential direction of the outer casing 16, and its upper surface supports the sealing body 17. The sealing body 17 is fixed to the upper part of the outer casing 16 by the grooved portion 22 and the open end of the outer casing 16 which is crimped to the sealing body 17.

[0038] The sealing body 17 has a structure in which an internal terminal plate 23, a lower valve body 24, an insulating member 25, an upper valve body 26, and a cap 27 are stacked in order from the electrode body 14 side, and functions as a safety valve. Each component constituting the sealing body 17 has, for example, a disc shape or a ring shape, and each component except the insulating member 25 is electrically connected to one another. The lower valve body 24 and the upper valve body 26 are connected at their respective centers, with the insulating member 25 interposed between their respective peripheries. When the internal pressure of the battery rises due to abnormal heat generation, the lower valve body 24 deforms and ruptures, pushing the upper valve body 26 towards the cap 27, thereby interrupting the current path between the lower valve body 24 and the upper valve body 26. If the internal pressure rises further, the upper valve body 26 ruptures, and gas is discharged from the opening of the cap 27.

[0039] The following describes in detail the positive electrode 11, negative electrode 12, separator 13, and non-aqueous electrolyte that constitute the non-aqueous electrolyte secondary battery 10, with particular emphasis on the positive electrode 11.

[0040] [Positive Electrode] The positive electrode 11 includes, for example, a positive electrode core and a positive electrode mixture layer formed on the surface of the positive electrode core. Preferably, the positive electrode mixture layer is formed on both sides of the positive electrode core. The positive electrode core can be made of a metal foil that is stable in the potential range of the positive electrode 11, such as aluminum or an aluminum alloy, or a film with the metal arranged on its surface. The thickness of the positive electrode core is, for example, 10 μm or more and 30 μm or less.

[0041] The positive electrode mixture layer includes, for example, a positive electrode active material, a conductive agent, and a binder. The thickness of the positive electrode mixture layer is, for example, 10 μm or more and 150 μm or less on one side of the positive electrode core. The positive electrode 11 can be manufactured, for example, by applying a positive electrode mixture slurry containing the positive electrode active material, conductive agent, etc., to the surface of the positive electrode core, drying the coating film, and then rolling it to form the positive electrode mixture layer on both sides of the positive electrode core.

[0042] Examples of conductive agents included in the positive electrode mixture layer include carbon black (CB), acetylene black (AB), Ketjenblack, carbon nanotubes (CNT), graphene, and other carbon-based particles such as graphite. These may be used individually or in combination of two or more types.

[0043] Examples of binders included in the positive electrode mixture layer include fluorine-based resins such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVDF), polyimide resins, acrylic resins, polyolefin resins, and polyacrylonitrile (PAN). These may be used individually or in combination of two or more types.

[0044] The positive electrode mixture layer contains a positive electrode active material with the composition formula LiNi （１－ｘ－ｙ－ｚ） Mn ｘ Al ｙ M ｚ O ２ The lithium transition metal composite oxide is represented by (0 < x < 0.03, 0 ≤ y ≤ 0.05, 0 ≤ z < 0.1, x + y + z ≤ 0.1, where M is at least one element selected from the group consisting of Co, Ti, Nb, Si, Mo, Zr, V, Fe, Mg, Cr, Cu, Sn, Ta, W, Na, K, Ba, Sr, Bi, Be, Zn, Ca, and B). The content of the elements constituting the lithium transition metal composite oxide can be measured by inductively coupled plasma atomic emission spectrometer (ICP-AES).

[0045] Lithium transition metal composite oxides are composed of secondary particles formed by the aggregation of primary particles. The particle size of the primary particles constituting the secondary particles of lithium transition metal composite oxides is, for example, between 0.02 μm and 2 μm. The particle size of the primary particles is measured as the diameter of the circumscribed circle in the particle image observed by a scanning electron microscope (SEM). The average particle diameter of the secondary particles of lithium transition metal composite oxides is, for example, between 2 μm and 30 μm. Here, the average particle diameter refers to the volume-based median diameter (D50). D50 refers to the particle size at which the cumulative frequency of the smallest particle size accounts for 50% in the volume-based particle size distribution, and is also called the median diameter. The particle size distribution of the secondary particles of lithium transition metal composite oxides can be measured using a laser diffraction particle size distribution analyzer (for example, Microtrac-Bell MT3000II) with water as the dispersion medium.

[0046] Here, in the volume-based particle size distribution of secondary particles of lithium transition metal composite oxide, D10 is defined as the particle size at which the cumulative frequency of the smallest particle size reaches 10%, and D50 is defined as the particle size at which the cumulative frequency of the smallest particle size reaches 90%. In this case, the value of {(D90 - D10) / D50} is preferably 0.9 or less, and preferably 0.88 or less. In other words, the volume-based particle size distribution of secondary particles of lithium transition metal composite oxide has a sharp distribution. This makes it possible to improve the packing density of the positive electrode active material (lithium transition metal composite oxide) in the positive electrode mixture layer, for example, and makes it easier to achieve higher battery capacity.

[0047] The above value of {(D90 - D10) / D50} is greatly influenced by the heating temperatures of the first and second firing processes. In particular, the value of {(D90 - D10) / D50} can be reduced by setting the heating temperature of the first firing process to 350°C or higher and 600°C or lower. On the other hand, if the heating temperature of the first firing process is less than 350°C, the Ni-containing hydroxide is not sufficiently oxidized in the first firing process, and the value of {(D90 - D10) / D50} tends to be large. Also, if the heating temperature of the first firing process exceeds 600°C, the Ni-containing oxide particles tend to form neckings with each other during the first firing process, and the value of {(D90 - D10) / D50} tends to be large.

[0048] The lithium transition metal composite oxide has a layered structure. Examples of the layered structure of the lithium transition metal composite oxide include a layered structure belonging to the space group R-3m, a layered structure belonging to the space group C2 / m, and the like. From the viewpoints of increasing the capacity and stabilizing the crystal structure, the lithium transition metal composite oxide preferably has a layered structure belonging to the space group R-3m.

[0049] Further, in the X-ray diffraction pattern obtained by powder X-ray diffraction of the lithium transition metal composite oxide, the integrated intensity I of peak A appearing in the range of 2θ of 43° ± 1° Ａ with respect to the integrated intensity I of peak B appearing in the range of 35° ± 1° Ｂ The ratio (I Ｂ / I Ａ ) is 0.1 or less. Here, peak A appearing in the range of 43° ± 1° is a peak caused by the (104) plane of LiNiO ２ etc. having a layered structure, and peak B appearing in the range of 35° ± 1° is presumed to be a peak caused by the (311) plane of LiMn ２ O ４ etc. having a spinel structure. Therefore, by setting the ratio (I Ｂ / I Ａ ) to 0.1 or less, the crystal structure of the lithium transition metal composite oxide is likely to be stabilized. As a result, while achieving a high capacity of the battery, the cycle characteristics and thermal stability can be improved.

[0050] The ratio (I Ｂ / I Ａ ) is greatly affected by the heating temperatures of the first firing step and the second firing step. In particular, by setting the heating temperature of the first firing step to 600°C or less, the spinel phase is less likely to precipitate, and the ratio (I Ｂ / I Ａ ) can be set to 0.1 or less. In other words, when the heating temperature of the first firing step exceeds 600°C, the ratio (I Ｂ / I Ａ ) exceeds 0.1. The ratio (I Ｂ / I Ａ ) is preferably 0.08 or less, and more preferably 0.06 or less.

[0051] Furthermore, the X-ray diffraction pattern of lithium transition metal composite oxides can be measured in the same way as the X-ray diffraction patterns of Ni-containing hydroxides and calcined products after the first calcination process described above. Also, the integrated intensity I of the X-ray diffraction peak can be measured. Ａ and I Ｂ This can be calculated, for example, using software included with the X-ray diffraction apparatus (e.g., PDXL, included with the powder X-ray diffractometer manufactured by Rigaku Corporation). In that case, the integrated intensity I of the X-ray diffraction peak is calculated. Ａ and I Ｂ This can be obtained, for example, by calculating the area from the height and full width at half maximum of each diffraction peak.

[0052] [Negative Electrode] The negative electrode 12 may, for example, have a negative electrode core and a negative electrode mixture layer formed on the surface of the negative electrode core, or a metallic Li foil may be used as the negative electrode 12. Alternatively, the negative electrode 12 may have a negative electrode core, and lithium metal may be deposited on the surface of the negative electrode core by charging. When the negative electrode 12 has a negative electrode mixture layer, it is preferable that the negative electrode mixture layer is formed on both sides of the negative electrode core. For the negative electrode core, a foil of a metal that is stable in the potential range of the negative electrode 12, such as copper or a copper alloy, or a film with the metal arranged on the surface layer, can be used. The thickness of the negative electrode core is, for example, 5 μm or more and 30 μm or less. The negative electrode mixture layer includes, for example, a negative electrode active material and a binder. The thickness of the negative electrode mixture layer is, for example, 10 μm or more and 150 μm or less on one side of the negative electrode core. The negative electrode 12 can be manufactured, for example, by applying a negative electrode mixture slurry containing a negative electrode active material, a binder, etc., to the surface of the negative electrode core, drying the coating, and then rolling it to form a negative electrode mixture layer on both sides of the negative electrode core.

[0053] The negative electrode active material contained in the negative electrode mixture layer is not particularly limited as long as it can reversibly intercept and release lithium ions, and generally carbon materials such as graphite are used. The graphite may be any of the following: natural graphite such as flake graphite, lump graphite, or clay graphite; lump artificial graphite; or artificial graphite such as graphitized mesophase carbon microbeads. In addition, metals that alloy with Li such as Si and Sn, metal compounds containing Si and Sn, or lithium titanium composite oxides may be used as the negative electrode active material. Furthermore, materials with a carbon coating may also be used. For example, SiO ｘAn Si-containing compound represented by (0.5 ≦ x ≦ 1.6), or Li ２ｙ SiO （２＋ｙ） An Si-containing compound in which fine particles of Si are dispersed in a lithium silicate phase represented by (0 < y < 2) may be used in combination with graphite.

[0054] Examples of the binder contained in the negative electrode mixture layer include styrene-butadiene rubber (SBR), nitrile-butadiene rubber (NBR), carboxymethyl cellulose (CMC) or its salt, polyacrylic acid (PAA) or its salt (PAA-Na, PAA-K, etc., and a partially neutralized salt may also be used), polyvinyl alcohol (PVA), and the like. These may be used alone or in combination of two or more.

[0055] [Separator] A porous sheet having ion permeability and insulation is used for the separator 13. Specific examples of the porous sheet include a microporous thin film, a woven fabric, a non-woven fabric, and the like. As the material of the separator 13, polyolefins such as polyethylene and polypropylene, cellulose, and the like are suitable. The separator 13 may have a single-layer structure or a multilayer structure. Further, a resin layer having high heat resistance such as an aramid resin may be formed on the surface of the separator 13.

[0056] A filler layer containing an inorganic filler may be formed at the interface between the separator 13 and at least one of the positive electrode 11 and the negative electrode 12. Examples of the inorganic filler include oxides containing metal elements such as Ti, Al, Si, Mg, and phosphate compounds. The filler layer can be formed by applying a slurry containing the filler to the surface of the positive electrode 11, the negative electrode 12, or the separator 13.

[0057] [Non-aqueous electrolyte] The non-aqueous electrolyte has ion conductivity (for example, lithium ion conductivity). The non-aqueous electrolyte may be a liquid electrolyte (electrolyte solution) or a solid electrolyte.

[0058] A liquid electrolyte (electrolyte solution) includes, for example, a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent. Examples of non-aqueous solvents include esters, ethers, nitriles such as acetonitrile, amides such as dimethylformamide, and mixtures of two or more of these. The non-aqueous solvent may contain halogen-substituted solvents in which at least some of the hydrogen atoms in the solvent are replaced with halogen atoms such as fluorine. Examples of halogen-substituted solvents include fluorinated cyclic carbonate esters such as fluoroethylene carbonate (FEC), fluorinated linear carbonate esters, and fluorinated linear carboxylic acid esters such as methyl fluoropropionate (FMP).

[0059] Examples of the above esters include cyclic carbonate esters such as ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate; linear carbonate esters such as dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), methyl propyl carbonate, ethyl propyl carbonate, and methyl isopropyl carbonate; cyclic carboxylic acid esters such as γ-butyrolactone (GBL) and γ-valerolactone (GVL); and linear carboxylic acid esters such as methyl acetate, ethyl acetate, propyl acetate, methyl propionate (MP), and ethyl propionate (EP).

[0060] Examples of the above ethers include 1,3-dioxolane, 4-methyl-1,3-dioxolane, tetrahydrofuran, 2-methyltetrahydrofuran, propylene oxide, 1,2-butylene oxide, 1,3-dioxane, 1,4-dioxane, 1,3,5-trioxane, furan, 2-methylfuran, 1,8-cineole, cyclic ethers such as crown ethers, 1,2-dimethoxyethane, diethyl ether, dipropyl ether, diisopropyl ether, dibutyl ether, dihexyl ether, ethyl vinyl ether, butyl vinyl ether, and methylphenyl ether. Examples include chain ethers such as ethylphenyl ether, butylphenyl ether, pentylphenyl ether, methoxytoluene, benzyl ethyl ether, diphenyl ether, dibenzyl ether, o-dimethoxybenzene, 1,2-diethoxyethane, 1,2-dibutoxyethane, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol dibutyl ether, 1,1-dimethoxymethane, 1,1-diethoxyethane, triethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether.

[0061] The electrolyte salt is preferably a lithium salt. A suitable lithium salt is LiClO ４ LiBF ４ LiPF ６ LiAlCl ４ LiSbF ６ , LiSCN, LiCF ３ SO ３ LiCF ３ CO ２ LiAsF ６ LiB １０ Cl １０ Examples include lithium lower aliphatic carboxylates, LiCl, LiBr, LiI, phosphates, borates, and imide salts. Examples of phosphates include lithium difluorophosphate (LiPO4). ２ F ２Examples include lithium difluorobis(oxalato)phosphate (LiDFOBP), lithium tetrafluoro(oxalato)phosphate, etc. Examples of borates include lithium bis(oxalato)borate (LiBOB), lithium difluoro(oxalato)borate (LiDFOB), etc. Examples of imide salts include lithium bisfluorosulfonylimide (LiN(FSO)). ２ ) ２ ), bistrifluoromethanesulfonate lithium (LiN(CF ３ SO ２ ) ２ ), trifluoromethanesulfonic acid nonafluorobutanesulfonic acid lithium (LiN(CF ３ SO ２ ) (C ４ F ９ SO ２ )), bispentafluoroethanesulfonate lithium (LiN(C) ２ F ５ SO ２ ) ２ ) etc. are used. Of these, LiPF is used from the viewpoint of ionic conductivity, electrochemical stability, etc. ６ It is preferable to use the following. The concentration of the lithium salt may be, for example, 4 moles or less per liter of non-aqueous solvent, or 3 moles or less, preferably 1.8 moles or less, and more preferably 0.8 moles or more and 1.8 moles or less.

[0062] Non-aqueous electrolytes may contain additives. Examples of additives include unsaturated carbonate esters, acid anhydrides, phenol compounds, benzene compounds, nitrile compounds, isocyanate compounds, sultone compounds, sulfuric acid compounds, borate ester compounds, phosphate ester compounds, and phosphite ester compounds.

[0063] Examples of unsaturated cyclic carbonate esters include vinylene carbonate, 4-methylvinylene carbonate, 4,5-dimethylvinylene carbonate, 4-ethylvinylene carbonate, 4,5-diethylvinylene carbonate, 4-propylvinylene carbonate, 4,5-dipropylvinylene carbonate, 4-phenylvinylene carbonate, 4,5-diphenylvinylene carbonate, vinylethylene carbonate, and divinylethylene carbonate. Unsaturated cyclic carbonate esters may be used individually or in combination of two or more. Some hydrogen atoms in the unsaturated cyclic carbonate esters may be substituted with fluorine atoms. The acid anhydride may be an anhydride formed by the intermolecular condensation of multiple carboxylic acid molecules, but it is preferable that it be an acid anhydride of a polycarboxylic acid. Examples of polycarboxylic acid acid anhydrides include succinic anhydride, maleic anhydride, and phthalic anhydride.

[0064] Examples of phenolic compounds include phenol and hydroxytoluene. Examples of benzene compounds include fluorobenzene, hexafluorobenzene, and cyclohexylbenzene (CHB).

[0065] Examples of nitrile compounds include adiponitrile, pimelonitrile, propionitrile, and succinonitrile. Examples of isocyanate compounds include methyl isocyanate (MIC), diphenylmethane diisocyanate (MDI), hexamethylene diisocyanate (HDI), toluene diisocyanate (TDI), isophorone diisocyanate (IPDI), and bisisocyanate methylcyclohexane (BIMCH). Examples of sultone compounds include propanesultone and propensultone. Examples of sulfate compounds include ethylene sulfate, ethylene sulfite, dimethyl sulfate, and lithium fluorosulfate. Examples of borate ester compounds include trimethylborate and tris(trimethylsilyl)borate. Examples of phosphate ester compounds include trimethylphosphate and tris(trimethylsilyl)phosphate. Examples of phosphite ester compounds include trimethylphosphite and tris(trimethylsilyl)phosphite.

[0066] As the solid electrolyte, for example, a solid or gel-like polymer electrolyte, an inorganic solid electrolyte, etc., can be used. As the inorganic solid electrolyte, materials known for all-solid-state lithium-ion secondary batteries, etc. (for example, oxide-based solid electrolytes, sulfide-based solid electrolytes, halogen-based solid electrolytes, etc.) can be used. The polymer electrolyte includes, for example, a lithium salt and a matrix polymer, or a non-aqueous solvent, a lithium salt and a matrix polymer. As the matrix polymer, for example, a polymer material that absorbs a non-aqueous solvent and gels is used. Examples of polymer materials include fluororesins, acrylic resins, polyether resins, etc.

[0067] The present disclosure will be further explained below with reference to examples and comparative examples, but the present disclosure is not limited to the following examples. <Example 1> [Preparation of positive electrode active material] By coprecipitation method [Ni ０．９２ Co ０．０５ Mn ０．０２ Al ０．０１ ] (OH) ２A Ni-containing hydroxide represented by [formula] was obtained (crystallization step). The obtained Ni-containing hydroxide was heated at 350°C for 6 hours under an oxygen stream to obtain a calcined product (Ni-containing oxide) which is a cathode active material precursor containing Ni, Co, and Mn (first calcination step). Subsequently, the above Ni-containing oxide and lithium hydroxide (LiOH) as a Li-containing compound were mixed to obtain a mixture (mixing step). Then, the obtained mixture was heated from room temperature to 750°C at a heating rate of 5.0°C / min under an oxygen stream and held at 750°C (maximum temperature) for 4 hours to calcinate (second calcination step).

[0068] Subsequently, the calcined product obtained in the second calcination step was added to water, and the mixture was washed with water at a stirring speed of 300 rpm for 10 minutes. The mixture was then dewatered using a filter press to obtain wet powder (washing step). The obtained wet powder was then dried under a vacuum atmosphere at 200°C for 2 hours to obtain the positive electrode active material (lithium transition metal composite oxide) of Example 1 (drying step).

[0069] The X-ray diffraction patterns of Ni-containing hydroxide and the calcined product obtained in the first calcination step were measured, and the maximum peak value I of the X-ray diffraction pattern of Ni-containing hydroxide was determined. １ , and the maximum peak value I of the X-ray diffraction pattern of the calcined product obtained in the first calcination step. ２ We calculated each of them. And {(I ２ -I １ ) / (I ２ +I １ The degree of oxidation of the fired product was calculated from the formula shown. As a result, the degree of oxidation of the fired product in Example 1 was 0.99.

[0070] Furthermore, when the X-ray diffraction pattern of the lithium transition metal composite oxide of Example 1 was measured, it showed a peak A appearing in the range of 43°±1° for 2θ, while it did not show a peak B appearing in the range of 35°±1°. This is presumed to be because the heating temperature in the first firing step was low, and the spinel phase hardly precipitated. Integrated intensity I of peak A Ａ The integral intensity I of peak B Ｂ The ratio (I Ｂ / I Ａ The value was 0.00.

[0071] [Preparation of the positive electrode] The above positive electrode active material, acetylene black (AB), and polyvinylidene fluoride were mixed in a mass ratio of 85:10:5, and N-methyl-2-pyrrolidone (NMP) was used as a dispersion medium to prepare a positive electrode slurry. Next, the positive electrode slurry was applied to a positive electrode core made of aluminum foil, the coating was dried and compressed, and then the positive electrode core was cut to a predetermined electrode size to obtain a positive electrode in which positive electrode slurry layers were arranged on both sides of the positive electrode core.

[0072] [Preparation of Non-Aqueous Electrolyte] Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) were mixed in a volume ratio of 3:3:4. Lithium hexafluoride phosphate (LiPF) was added to this mixed solvent. ６ A non-aqueous electrolyte was prepared by dissolving the substance to a concentration of 1.2 mol / liter.

[0073] [Preparation of Test Cell] A lithium metal foil was used as the negative electrode, and the positive and negative electrodes were arranged facing each other via a separator to form an electrode body. This electrode body and the non-aqueous electrolyte were placed in a coin-shaped outer casing, and the opening of the outer casing was sealed with a gasket and a sealing body to produce a test cell (non-aqueous electrolyte secondary battery).

[0074] [Evaluation of Initial Discharge Capacity] Under a temperature environment of 25°C, the battery was charged with a constant current at 0.1C up to 4.3V, and then charged with a constant voltage at 4.3V down to 0.01C. After that, it was discharged with a constant current at 0.1C down to 2.5V, and the initial discharge capacity was measured.

[0075] [Evaluation of Reaction Resistance] Under a temperature environment of 25°C, a Solartron 1255B (manufactured by Solartron Corporation) was charged at a constant voltage of 4.3V (vsLi) with a current equivalent to 0.01C. After that, the AC impedance was measured with an applied voltage of 10mV and a measurement frequency range of 0.01 to 200kHz, and the value of the reaction resistance was determined from the Nyquist plot (arc of approximately 100Hz to 0.01Hz).

[0076] [Evaluation of Thermal Stability] Under a temperature environment of 25°C, the cells were charged with a constant current at 0.1C up to 4.3V, and then charged with a constant voltage at 4.3V until the temperature dropped to 0.01C. After that, the cells were placed in a constant temperature bath at 130°C, and the battery temperature was measured using a thermocouple attached to the flat surface of the battery.

[0077] <Example 2> In the preparation of the positive electrode active material, a test cell was prepared and evaluated in the same manner as in Example 1, except that the heating temperature in the first firing step was changed from 350°C to 400°C.

[0078] <Example 3> In the preparation of the positive electrode active material, a test cell was prepared and evaluated in the same manner as in Example 1, except that the heating temperature in the first firing step was changed from 350°C to 500°C.

[0079] <Example 4> In the preparation of the positive electrode active material, a test cell was prepared and evaluated in the same manner as in Example 1, except that the heating temperature in the first firing step was changed from 350°C to 550°C.

[0080] <Example 5> In the preparation of the positive electrode active material, a test cell was prepared and evaluated in the same manner as in Example 1, except that the heating temperature in the first firing step was changed from 350°C to 600°C.

[0081] <Example 6> In the preparation of the positive electrode active material, the composition of the Ni-containing hydroxide is set to [Ni ０．９１ Co ０．０５ Mn ０．０２ Al ０．０２ ] (OH) ２ Except for changing the heating temperature in the first firing step from 350°C to 500°C, a test cell was prepared and evaluated in the same manner as in Example 1.

[0082] <Example 7> In the preparation of the positive electrode active material, the composition of the Ni-containing hydroxide is set to [Ni ０．９２ Co ０．０５ Mn ０．０１ Al ０．０２ ] (OH) ２ Except for changing the heating temperature in the first firing step from 350°C to 500°C, a test cell was prepared and evaluated in the same manner as in Example 1.

[0083] <Comparative Example 1> In the preparation of the positive electrode active material, the composition of the Ni-containing hydroxide is [Ni０．９０ Co ０．０５ Mn ０．０５ ] (OH) ２ Except for changing the heating temperature in the first firing step from 350°C to 180°C, a test cell was prepared and evaluated in the same manner as in Example 1.

[0084] <Comparative Example 2> In the preparation of the positive electrode active material, the test cell was prepared and evaluated in the same manner as in Example 1, except that the heating temperature in the first firing step was changed from 350°C to 180°C.

[0085] <Comparative Example 3> In the preparation of the positive electrode active material, the test cell was prepared and evaluated in the same manner as in Example 1, except that the heating temperature in the first firing step was changed from 350°C to 300°C.

[0086] <Comparative Example 4> In the preparation of the positive electrode active material, the test cell was prepared and evaluated in the same manner as in Example 1, except that the heating temperature in the first firing step was changed from 350°C to 700°C.

[0087] Furthermore, when the X-ray diffraction pattern of the lithium transition metal composite oxide of Comparative Example 4 was measured, it showed a peak A appearing in the range of 43°±1° for 2θ, and a peak B appearing in the range of 35°±1°. This is presumed to be due to the high heating temperature in the first firing process, which caused the spinel phase to precipitate. Integrated intensity of peak A Ａ The integral intensity I of peak B Ｂ The ratio (I Ｂ / I Ａ The value was 0.11.

[0088] Table 1 shows the initial discharge capacity, reaction resistance, and battery temperature of the test cells for Examples 1-7 and Comparative Examples 1-4. Table 1 also shows the composition of the Ni-containing hydroxide, firing conditions, degree of oxidation of the fired product, the {(D90-D10) / D50} value, and the ratio (I) for Examples 1-7 and Comparative Examples 1-1. Ｂ / I ＡThe following are also shown. Note that the initial discharge capacity, reaction resistance, and battery temperature shown in Table 1 are expressed relatively, with the initial discharge capacity, reaction resistance, and battery temperature of Comparative Example 1 set to 100. A larger initial discharge capacity value indicates higher capacity, a smaller reaction resistance value indicates lower resistance, and a smaller battery temperature value indicates better thermal stability.

[0089] In addition to the items mentioned above, Table 1 also shows the ratio of the mass of the final cathode active material to the total mass of the Ni-containing oxide and Li-containing compound mixed in the mixing process (hereinafter referred to as the "yield ratio"). A higher yield ratio improves the productivity of the cathode active material manufacturing process. The yield ratios shown in Table 1 are expressed relatively, with the yield ratio of Comparative Example 1 set to 100. A higher value indicates better productivity.

[0090]

[0091] As shown in Table 1, the test cell of the example shows improved initial discharge capacity, reduced reaction resistance, and lower battery temperature compared to the test cell of the comparative example. In other words, the test cell of the example achieves high battery capacity while also achieving low resistance and improved thermal stability. This is presumed to be because a lithium transition metal composite oxide with a stable crystal structure was obtained by using a Ni-containing hydroxide containing more than 0 mol% and less than 3 mol%, setting the heating temperature in the first firing step to 350°C or higher and 600°C or lower, and the heating temperature in the second firing step to 600°C or higher and 900°C or lower.

[0092] This disclosure is further illustrated by the following embodiments. Configuration 1: A method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery, comprising: a first calcination step of heat-treating a Ni-containing hydroxide; a mixing step of mixing the calcined product obtained in the first calcination step with a Li-containing compound; and a second calcination step of heat-treating the mixture obtained in the mixing step at a temperature of 600°C or higher and 900°C or lower, wherein the Ni-containing hydroxide has the compositional formula Ni （１－ｘ－ｙ－ｚ） Mn ｘ Al ｙ M ｚ (OH) ２A method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery, wherein the composition formula is represented by (0 < x < 0.03, 0 ≤ y ≤ 0.05, 0 ≤ z < 0.1, x + y + z ≤ 0.1, and M is at least one element selected from the group consisting of Co, Ti, Nb, Si, Mo, Zr, V, Fe, Mg, Cr, Cu, Sn, Ta, W, Na, K, Ba, Sr, Bi, Be, Zn, Ca, and B), and the heating temperature in the first firing step is 350°C or higher and 600°C or lower. Configuration 2: A method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to Configuration 1, wherein in the composition formula, element M contains Co. Configuration 3: A method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to Configuration 1 or 2, wherein in the composition formula, 0.01 ≤ x < 0.03, 0 ≤ y ≤ 0.02, and 0 ≤ z ≤ 0.05 are satisfied. Configuration 4: Composition formula LiNi （１－ｘ－ｙ－ｚ） Mn ｘ Al ｙ M ｚ O ２ A positive electrode active material for a non-aqueous electrolyte secondary battery comprising a lithium transition metal composite oxide represented by (0 < x < 0.03, 0 ≤ y ≤ 0.05, 0 ≤ z < 0.1, x + y + z ≤ 0.1, where M is at least one element selected from the group consisting of Co, Ti, Nb, Si, Mo, Zr, V, Fe, Mg, Cr, Cu, Sn, Ta, W, Na, K, Ba, Sr, Bi, Be, Zn, Ca, and B), wherein the particle size of the lithium transition metal composite oxide particles is based on volume. In the distribution, when D10 is defined as the particle size at which the cumulative frequency from the smallest particle size accounts for 10%, D50 as the particle size at which the cumulative frequency from the smallest particle size accounts for 50%, and D90 as the particle size at which the cumulative frequency from the smallest particle size accounts for 90%, the value of {(D90 - D10) / D50} is 0.9 or less, and the integrated intensity I of peak A that appears in the range of 2θ = 43° ± 1° in the X-ray diffraction pattern obtained by powder X-ray diffraction of the lithium transition metal composite oxide is 0.9 or less. Ａ The integral intensity I of peak B, which appears in the range of 35°±1° for 2θ. Ｂ The ratio (I Ｂ / I Ａ ) is a positive electrode active material for a non-aqueous electrolyte secondary battery having a value of 0.1 or less. Configuration 5: A non-aqueous electrolyte secondary battery comprising a positive electrode containing the positive electrode active material for a non-aqueous electrolyte secondary battery described in Configuration 4, a negative electrode, and a non-aqueous electrolyte.

[0093] 10 Non-aqueous electrolyte secondary battery, 11 Positive electrode, 12 Negative electrode, 13 Separator, 14 Electrode body, 16 Outer casing, 17 Sealing body, 18, 19 Insulating plate, 20 Positive electrode lead, 21 Negative electrode lead, 22 Grooved section, 23 Internal terminal plate, 24 Lower valve body, 25 Insulating member, 26 Upper valve body, 27 Cap, 28 Gasket.

Claims

1. A method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery, comprising: a first calcination step of heat-treating a Ni-containing hydroxide; a mixing step of mixing the calcined product obtained in the first calcination step with a Li-containing compound; and a second calcination step of heat-treating the mixture obtained in the mixing step at a temperature of 600°C or higher and 900°C or lower, wherein the Ni-containing hydroxide has the compositional formula Ni （１－ｘ－ｙ－ｚ） Mn ｘ Al ｙ M ｚ (OH) ２ A method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery, wherein the positive electrode active material is represented by (0 < x < 0.03, 0 ≤ y ≤ 0.05, 0 ≤ z < 0.1, x + y + z ≤ 0.1, M is at least one element selected from the group consisting of Co, Ti, Nb, Si, Mo, Zr, V, Fe, Mg, Cr, Cu, Sn, Ta, W, Na, K, Ba, Sr, Bi, Be, Zn, Ca, and B), and the heating temperature in the first firing step is 350°C or higher and 600°C or lower.

2. The method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 1, wherein in the composition formula, element M contains Co.

3. A method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 1, wherein the composition formula satisfies 0.01 ≤ x < 0.03, 0 ≤ y ≤ 0.02, and 0 ≤ z ≤ 0.

05.

4. Composition LiNi （１－ｘ－ｙ－ｚ） Mn ｘ Al ｙ M ｚ O ２ (0 < x < 0.03, 0 ≤ y ≤ 0.05, 0 ≤ z < 0.1, x + y + z ≤ 0.1, M is at least one element selected from the group consisting of Co, Ti, Nb, Si, Mo, Zr, V, Fe, Mg, Cr, Cu, Sn, Ta, W, Na, K, Ba, Sr, Bi, Be, Zn, Ca, and B) is a positive electrode active material for a non-aqueous electrolyte secondary battery. In the volume-based particle size distribution of the particles of the lithium transition metal composite oxide, the particle size at which the cumulative frequency becomes 10% from the smaller particle size is defined as D10, the particle size at which the cumulative frequency becomes 50% from the smaller particle size is defined as D50, and the particle size at which the cumulative frequency becomes 90% from the smaller particle size is defined as D90. When { (D90 - D10) / D50} is 0.9 or less, in the X-ray diffraction pattern obtained by powder X-ray diffraction of the lithium transition metal composite oxide, the integrated intensity I of peak A appearing in the range of 2θ = 43° ± 1° Ａ with respect to the integrated intensity I of peak B appearing in the range of 2θ = 35° ± 1° Ｂ ratio (I Ｂ / I Ａ ) is 0.1 or less, a positive electrode active material for a non-aqueous electrolyte secondary battery.

5. A non-aqueous electrolyte secondary battery comprising a positive electrode containing the positive electrode active material for a non-aqueous electrolyte secondary battery described in claim 4, a negative electrode, and a non-aqueous electrolyte.

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