Positive electrode active material for non-aqueous electrolyte secondary battery, and non-aqueous electrolyte secondary battery

Abstract

This positive electrode active material for a nonaqueous electrolyte secondary battery contains a lithium-containing composite oxide. The lithium-containing composite oxide is represented by the general formula LixNiaMnbM1cM2dO2 (where 0.80 ≦ x ≦ 1.2, 0.50 ≦ a ≦ 0.95, 0.05 ≦ b ≦ 0.50, 0 ≦ c ≦ 0.20, a + b + c = 1, and 0 ≦ d ≦ 0.10, M1 is at least one element selected from between Co and Al, and M2 is at least one metal element excluding Li, Ni, and Mn). In a powder X-ray diffraction pattern of the lithium-containing composite oxide, the value related to the difference between a peak position 2θ012 on a (012) plane and a peak position 2θ018 on a (018) plane expressed as [(2θ018 - 2θ012) - 0.5031 × a] is in the range of 25.60 to 31.05.

Description

Positive electrode active material for non-aqueous electrolyte secondary batteries and non-aqueous electrolyte secondary batteries

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

[0002] In non-aqueous electrolyte secondary batteries such as lithium-ion secondary batteries, the positive electrode active material greatly affects battery performance such as input / output characteristics, capacity, and durability, and therefore, much research has been conducted on positive electrode active materials. Generally, lithium-containing composite oxides containing transition metal elements such as Ni and Mn are used as positive electrode active materials. The types and amounts of elements contained in the lithium-containing composite oxide, as well as the crystal structure of the composite oxide, greatly affect battery performance, so appropriate design and control of these are important. For example, Patent Document 1 describes a general formula Li １＋ｘ Ni １－ｙ－ｚ Co ｙ Al ｚ O ２ A positive electrode active material is disclosed comprising composite oxide particles having a composition expressed as (where 0 ≤ x ≤ 0.1, 0.1 ≤ y ≤ 0.4, 0.02 ≤ z ≤ 0.1). This positive electrode active material is characterized in that the difference in Bragg angles between the (110) plane and the (018) plane in the powder X-ray diffraction pattern of the composite oxide particles is [0.29 × (y + z) + 0.172] degrees or more, and the 10% cumulative frequency particle size of the composite oxide particles is 1 μm or more.

[0003] Japanese Patent Publication No. 2002-222648

[0004] Incidentally, non-aqueous electrolyte secondary batteries are in demand for even higher capacity, for example, from the standpoint of their application as power sources for vehicle propulsion. In the example described in Patent Document 1, the initial discharge capacity of the prototype positive electrode evaluation battery is stated to be 160 mAh / g or more, but the charging capacity has not been considered, and there is room for improvement.

[0005] The objective of the disclosed technology is to provide a positive electrode active material for a non-aqueous electrolyte secondary battery and a non-aqueous electrolyte secondary battery that can contribute to increasing capacity.

[0006] The positive electrode active material for a non-aqueous electrolyte secondary battery according to one aspect of the present disclosure is a positive electrode active material for a non-aqueous electrolyte secondary battery containing a lithium-containing composite oxide, and the lithium-containing composite oxide has the general formula Li ｘ Ni ａ Mn ｂ M1 ｃ M2 ｄ O ２ (where 0.80 ≤ x ≤ 1.2, 0.50 ≤ a ≤ 0.95, 0.05 ≤ b ≤ 0.50, 0 ≤ c ≤ 0.20, a + b + c = 1, 0 ≤ d ≤ 0.10, M1 is at least one element of Co and Al, and M2 is at least one metal element other than Li, Ni, and Mn), and the value [(2θ ０１２ of the peak position of the (012) plane and the peak position 2θ ０１８ of the (018) plane in the powder X-ray diffraction pattern of the lithium-containing composite oxide)[(2θ ０１８ - 2θ ０１２ ) - 0.5031 × a] is 25.60 or more and 31.05 or less.

[0007] According to the positive electrode active material for a non-aqueous electrolyte secondary battery according to the present disclosure, it is possible to contribute to increasing the capacity of the non-aqueous electrolyte secondary battery.

[0008] It is an axial cross-sectional view of a non-aqueous electrolyte secondary battery which is an example of an embodiment. It is a powder X-ray diffraction pattern of the lithium-containing composite oxide of Example 1. For the lithium-containing composite oxides of Examples 1 to 14 and Comparative Examples 1 to 3, a graph plotting the value of the 3-cycle integrated charge capacity against the value of the 018 - 012 peak position difference 2θ ０１８ - 2θ ０１２ . For the lithium-containing composite oxides of Examples 10 to 14, a graph plotting the value of the 018 - 012 peak position difference 2θ ０１８ - 2θ ０１２ against the Ni ratio a. For the lithium-containing composite oxides of Examples 1 to 14 and Comparative Examples 1 to 3, a graph plotting the value of the 3-cycle integrated charge capacity against the value [(2θ ０１８ - 2θ ０１２ ) - 0.5031 × a] of the 018 - 012 peak position difference.

[0009] Hereinafter, with reference to the drawings, a positive electrode active material for a non-aqueous electrolyte secondary battery (hereinafter also simply referred to as "positive electrode active material") and an example of an embodiment of a non-aqueous electrolyte secondary battery using the positive electrode active material will be described in detail. Note that configurations obtained by selectively combining the components of the multiple embodiments and modified examples described below are included within the scope of this disclosure.

[0010] ≪Non-aqueous electrolyte secondary battery≫ In the following, 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 battery outer casing is not limited to a cylindrical shape. 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 non-aqueous electrolyte secondary battery designs may be applied.

[0011] Figure 1 is an axial cross-sectional view of a cylindrical non-aqueous electrolyte secondary battery 10, which is an example of an embodiment. As shown in Figure 1, the non-aqueous electrolyte secondary battery 10 comprises a wound electrode body 14, a non-aqueous electrolyte, 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. Hereafter, for the sake of convenience 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."

[0012] 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 isolates the positive electrode 11 and the negative electrode 12 from each other. 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 short direction of the positive electrode 11 and the negative electrode 12 is the axial direction. That is, the end faces of the positive electrode 11 and the negative electrode 12 in the short direction form the end faces in the axial direction of the electrode body 14.

[0013] 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.

[0014] 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.

[0015] 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. 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 peripheral edges. When the internal pressure of the battery rises due to abnormal heat generation, the lower valve body 24 deforms and breaks, 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 breaks, and gas is discharged from the opening of the cap 27.

[0016] 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.

[0017] <Positive Electrode> The positive electrode 11 has a positive electrode core and a positive electrode mixture layer disposed on the positive electrode core. The positive electrode core can be made of a metal foil that is stable within the potential range of the positive electrode 11, such as aluminum, aluminum alloy, stainless steel, or titanium, or a film with the metal disposed on its surface.

[0018] The positive electrode mixture layer preferably comprises a positive electrode active material, a conductive agent, and a binder, and is provided on both sides of the positive electrode core. The positive electrode 11 can be manufactured, for example, by applying a positive electrode mixture slurry containing a positive electrode active material, a conductive agent, and a binder onto the positive electrode core, drying the coating film, and then compressing it to form the positive electrode mixture layer on both sides of the positive electrode core.

[0019] Examples of conductive agents included in the positive electrode mixture layer include carbon black such as acetylene black and Ketjenblack, graphite, carbon nanotubes (CNTs), carbon nanofibers, graphene, metal fibers, metal powders, and conductive whiskers. One type of conductive agent may be used alone, or multiple types may be used in combination. The content of the conductive agent is not particularly limited, but is, for example, 0.1% by mass or more and 5% by mass or less relative to the mass of the positive electrode mixture layer.

[0020] Examples of binders included in the positive electrode mixture layer include fluororesins such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVDF), olefin resins such as polyethylene, polypropylene, ethylene-propylene-isoprene copolymer and ethylene-propylene-butadiene copolymer, and acrylic resins such as polyacrylonitrile (PAN), polyimide, polyamide, and ethylene-acrylic acid copolymer. These resins may also be used in combination with carboxymethylcellulose (CMC) or its salts, polyethylene oxide (PEO), etc. The binder may be used alone or in combination of multiple types. The binder content is not particularly limited, but is, for example, 0.1% to 5% by mass relative to the mass of the positive electrode mixture layer.

[0021] [Lithium-containing composite oxide] The positive electrode active material according to this embodiment includes a lithium-containing composite oxide.

[0022] The lithium-containing composite oxide of this embodiment is a composite oxide that contains Li, Ni, Mn, optionally any metal element M1, and optionally any additive element M2.

[0023] Lithium-containing composite oxides have the general formula Li ｘ Ni ａ Mn ｂ M1 ｃ M2 ｄ O ２ It is expressed as follows: where 0.80 ≤ x ≤ 1.2, 0.50 ≤ a ≤ 0.95, 0.05 ≤ b ≤ 0.50, 0 ≤ c ≤ 0.20, a + b + c = 1, and 0 ≤ d ≤ 0.10. M1 is at least one element from Co and Al. M2 is at least one metallic element other than Li, Ni and Mn. The content of the elements constituting the lithium-containing composite oxide can be measured by inductively coupled plasma atomic emission spectrometer (ICP-AES), electron beam microanalyzer (EPMA), or energy dispersive X-ray spectrometer (EDX), etc.

[0024] The ratio of Li to the total number of moles of Ni, Mn, and M1, i.e., the molar ratio of Li x, is 0.80 ≤ x ≤ 1.2, preferably 1 ≤ x ≤ 1.15, and more preferably 1.05 ≤ x ≤ 1.11, from the viewpoint of improving charging capacity.

[0025] The ratio of Ni to the total number of moles of Ni, Mn, and M1, i.e., the molar ratio of Ni a (also called "Ni ratio a"), is 0.50 ≤ a ≤ 0.95, preferably 0.60 ≤ a ≤ 0.92, more preferably 0.70 ≤ a ≤ 0.90, and particularly preferably 0.78 ≤ a ≤ 0.90, from the viewpoint of improving charging capacity.

[0026] The ratio of Mn to the total number of moles of Ni, Mn, and M1, i.e., the molar ratio b of Mn, is 0.05 ≤ b ≤ 0.50, preferably 0.08 ≤ b ≤ 0.40, and more preferably 0.10 ≤ b ≤ 0.35, from the viewpoint of improving charging capacity.

[0027] M1 is at least one element from Co and Al, and is an optional component. The ratio of M1 to the total number of moles of Ni, Mn, and M1, i.e., the molar ratio c of M1, is 0 ≤ c ≤ 0.20, preferably 0 ≤ c ≤ 0.10. By containing Co, the lithium-containing composite oxide can improve the heat resistance of the battery. Furthermore, by containing Al, the lithium-containing composite oxide can stabilize its crystal structure.

[0028] M2 is at least one metallic element other than Li, Ni, and Mn. M2 is an optional component and does not need to be included in the lithium-containing composite oxide, but its inclusion is preferable from the viewpoint of improving battery performance. It is preferable that M2 is at least one metallic element other than Li, Ni, Mn, and M1. It is even more preferable that M2 is at least one metallic element selected from the group consisting of Ca, Sr, Zr, Mo, W, V, Nb, Ta, Sb, and Bi. The ratio of M2 to the total number of moles of Ni, Mn, and M1, i.e., the molar ratio d of M2, is preferably 0 ≤ d ≤ 0.10 and 0 ≤ d ≤ 0.02. M2 may be contained inside the particles of the lithium-containing composite oxide or may be present on the particle surface.

[0029] Lithium-containing composite oxides may be composed of primary particles or secondary particles formed by the aggregation of primary particles. Primary particles are single particles without grain boundaries within them, while secondary particles are formed by the aggregation of, for example, two to 10,000 primary particles. The particle state of lithium-containing composite oxides can be confirmed by observing the particles using a scanning electron microscope (e.g., Hitachi High-Tech SU8600). Although not intended to be limiting, examples of volume-based median diameters (D50) of lithium-containing composite oxides are 1 to 30 μm or 3 to 20 μm. D50 is the particle size at which the volume integrated value in the particle size distribution measured by laser diffraction scattering method becomes 50%.

[0030] The positive electrode active material may include positive electrode active materials other than the lithium-containing composite oxide of this embodiment, to the extent that it does not impair the purpose of this disclosure. Multiple types of positive electrode active materials can be used in the non-aqueous electrolyte secondary battery 10, for example, depending on the required battery performance. Even when positive electrode active materials other than the lithium-containing composite oxide of this embodiment are used in combination as the positive electrode active material, the above-mentioned high capacity effect can be obtained depending on the content of the lithium-containing composite oxide of this embodiment. The ratio of the mass of the lithium-containing composite oxide of this embodiment to the total mass of the positive electrode active material may be, for example, 80% by mass or more, and may be 90% by mass or more.

[0031] [Powder X-ray Diffraction Pattern of Lithium-Containing Composite Oxide] The lithium-containing composite oxide of this embodiment satisfies the predetermined requirements regarding the difference in diffraction peak positions of two predetermined lattice planes that appear in the powder X-ray diffraction pattern obtained by powder X-ray diffraction measurement. In this specification, the diffraction peak of the (hkl) plane is referred to as the "hkl peak," and the diffraction angle 2θ of the said diffraction peak is referred to as the "peak position 2θ." ｈｋｌ " or "2θ ｈｋｌ It is sometimes referred to as "". Also, (h １ k １ l １ ) Peak position of the surface 2θ ｈ１ｋ１ｌ１ and (h ２ k ２ l ２ ) Peak position of the surface 2θ ｈ２ｋ２ｌ２ The difference between this and "h２ k ２ l ２ -h １ k １ l １ "Peak position difference" or "2θ" ｈ２ｋ２ｌ２ -2θ ｈ１ｋ１ｌ１ It is sometimes referred to as "..."

[0032] - Powder X-ray Diffraction Measurement Method - Powder X-ray diffraction measurement of lithium-containing composite oxides can be performed 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).

[0033] The measurement conditions using the above-mentioned X-ray diffractometer are as follows:

[0034] X-ray source: CuKα Tube voltage: 40kV Tube current: 15mA Divergent slit (DS): 1 / 4° Scattering slit (SS): 13mm (open) Receiving slit (RS): 13mm (open) Scan axis: 2θ / θ Scanning method: Continuous 2θ scan range: 10-80° Scan speed: 10° / min Step size: 0.02° In the data obtained from the above powder X-ray diffraction measurement, the scan angle 2θ is set to x, and the data is fitted using the symmetric pseudo-Voigt function shown in equation (1) below. With this fitting, the peak intensity A and peak position μ (=2θ) of each diffraction peak are obtained. ｈｋｌ ), the half-width σ and the composite ratio α are obtained.

[0035]

[0036] Based on the peak position μ of each lattice plane obtained by fitting, the peak position difference between two predetermined lattice planes is calculated. When calculating the peak position difference, instrument errors are removed based on the measurement results of a standard sample. Specifically, for example, the angle standard is determined by using the results of measurements of the NIST LaB6 660b standard sample, with only the 2θ scan range changed to 10-140° from the above conditions. Based on the lattice constant of the NIST LaB6 660b standard sample, the instrument function Δ(2θ) = t ０ +t １ / tan2θ+t ２The cosθ value was calculated. The instrument error in this device was Δ(2θ) = -0.041 + (-0.021) / tan2θ + 0.05 × cosθ. In addition, Kα2 removal was performed using the Rachinger method (W.A. Rachinger, J. Sci. Instrum, 25, 254 (1948)) when calculating the peak position difference.

[0037] The fitting using this symmetric pseudo-Voigt function, the derivation of the instrument function, and the Kα2 removal can be implemented, for example, by using a computer (e.g., a personal computer) equipped with a CPU, ROM, RAM, HDD, and various interfaces. For example, this can be done by installing the solver function of Microsoft Excel and the nonlinear fitting function of Lightstone's Origin on this computer, or by installing dedicated software for analysis (e.g., Rigaku Corporation's X-ray analysis integrated software SmartLab Studio II, "RIETAN-FP" program (F. Izumi and K. Momma, Solid State Phenom., 130, 15-20 (2007))) and running this software to perform the aforementioned processes.

[0038] As an example of the obtained powder X-ray diffraction pattern, Figure 2 shows the powder X-ray diffraction pattern of the lithium-containing composite oxide of Example 1, which will be described later. As shown in Figure 2, multiple diffraction peaks were observed that belong to each lattice plane, including the (003), (101), (006), (012), (104), and (018) planes.

[0039] - Relationship between the peak position difference of important peaks and charging capacity - The inventors of this application have proposed the general formula Li ｘ Ni ａ Mn ｂ M1 ｃ M2 ｄ O ２Powder X-ray diffraction measurements were performed on lithium-containing composite oxides having various elemental proportions where the values ​​of x, a, b, c, and d are not limited to the above range. As a result, a proportional correlation was found between the peak position difference of important diffraction peaks in the powder X-ray diffraction pattern, such as the 003 peak, 101 peak, 006 peak, 012 peak, 104 peak, and 018 peak, and the charging capacity.

[0040] As a specific example, Figure 3 shows the peak position 2θ of the (012) plane obtained by the method described above for the lithium-containing composite oxides of Examples 1 to 14 and Comparative Examples 1 to 3, which will be described later. ０１２ and the peak position 2θ of the (018) plane ０１８ The difference between 2θ ０１８ -2θ ０１２ This is a graph plotting the value of the 3-cycle cumulative charging capacity against the value of (see Table 3 below). As shown in Figure 3, the 018-012 peak position difference 2θ ０１８ -2θ ０１２ A larger value tends to correlate with a larger charging capacity.

[0041] - Influence of Ni molar ratio a - The inventors of this application have also found that an increase in the Ni ratio a contributes to an increase in charging capacity.

[0042] Figure 4 shows the lithium-containing composite oxides of Examples 10 to 14 described later, with respect to the Ni ratio a, and the peak position difference of 018-012 θ. ０１８ -2θ ０１２ This is a graph plotting the values ​​of . Note that the lithium-containing composite oxides of Examples 10 to 14 do not contain metal element M1 and additive element M2, and are samples prepared by the same manufacturing method but with different Ni ratios a. When a linear function was fitted to the results in Figure 4, the change in Ni ratio a was found to be due to the difference in peak position 2θ from its slope. ０１８ -2θ ０１２ The change resulting from this (also referred to in this specification as the "correction coefficient for the Ni ratio a") was found to be 0.5031. From this, the peak position difference 2θ ０１８ -2θ ０１２By correcting the value using a correction coefficient related to the Ni ratio a, the relationship between the peak position difference and the charging capacity can be evaluated more accurately by eliminating the influence of the Ni ratio a.

[0043] Furthermore, based on the powder X-ray diffraction patterns and charging capacity data of the lithium-containing composite oxides of Examples 10 to 14, correction coefficients for the Ni ratio a were calculated for peak position differences other than the 018-012 peak position difference (see Table 2 below).

[0044] - Values ​​related to peak position difference - Figure 5 shows the values ​​related to the 018-012 peak position difference [(2θ) for lithium-containing composite oxides of Examples 1 to 14 and Comparative Examples 1 to 3. ０１８ -2θ ０１２ This graph plots the charging capacity value against [-0.5031 × a]. Note that the value related to the peak position difference is the value obtained by correcting the peak position difference value with the correction coefficient for the Ni ratio a mentioned above. As shown in Figure 5, it was found that the charging capacity value tends to increase as the value related to the peak position difference increases.

[0045] From the results in Figure 5, the lithium-containing composite oxide according to this embodiment has a value related to the difference in the position of the 018-012 peaks in the powder X-ray diffraction pattern [(2θ ０１８ -2θ ０１２ ) - 0.5031 × a] is 25.60 or more and 31.05 or less, preferably 25.60 or more and 30.00 or less.

[0046] This improves the stability of the crystal structure of lithium-containing composite oxides, thereby improving battery performance. 018-012 Values ​​related to peak position difference [(2θ ０１８ -2θ ０１２ If the value of [-0.5031 × a] is below the lower limit, sufficient battery performance may not be obtained. Furthermore, considering the crystal structure of lithium-containing composite oxides, it is considered practically difficult to prepare lithium-containing composite oxides that exceed the upper limit.

[0047] Furthermore, it is preferable that the values ​​relating to the peak position difference originating from other grid planes also satisfy the following conditions.

[0048] That is, the peak position 2θ of the (104) plane １０４ and the aforementioned 2θ０１８ The value related to the peak position difference from [((2θ ０１８ -2θ １０４ ) - 0.3749×a] is preferably 19.61 or more and 29.49 or less, and more preferably 19.61 or more and 25.00 or less.

[0049] The peak position 2θ of the (101) plane １０１ and the 2θ ０１８ The value related to the difference from [((2θ ０１８ -2θ １０１ ) - 0.5877×a] is preferably 27.19 or more and 45.55 or less, and more preferably 27.19 or more and 40.00 or less.

[0050] The peak position 2θ of the (003) plane ００３ and the peak position 2θ of the (006) plane ００６ The value related to the difference from [((2θ ００６ -2θ ００３ ) - 0.2292×a] is preferably 19.01 or more and 25.49 or less, and more preferably 19.01 or more and 23.00 or less.

[0051] The peak position 2θ of the (003) plane ００３ and the 2θ ０１８ The value related to the difference from [((2θ ０１８ -2θ ００３ ) - 0.1139×a] is preferably 45.45 or more and 49.29 or less, more preferably 45.46 or more and 49.29 or less, and even more preferably 45.46 or more and 47.00 or less.

[0052] The 2θ ０１２ and the peak position 2θ of the (104) plane １０４ The value related to the difference from [((2θ １０４ -2θ ０１２ ) - 0.1282×a] is preferably 5.99 or more and 11.87 or less, more preferably 6.00 or more and 11.87 or less, and even more preferably 6.00 or more and 10.00 or less.

[0053] The peak position 2θ of the (003) plane ００３ and the peak position 2θ of the (104) plane １０４ The value related to the difference from [((2θ１０４ -2θ ００３ )+0.2611×a] is preferably 25.82 or more and 30.11 or less, more preferably 25.86 or more and 30.11 or less, and even more preferably 25.86 or more and 28.00 or less.

[0054] - Value depending on the plane indices hkl - Although the reason for the correlation between the value related to the peak position difference and the charge capacity is not clear, it is considered that the stabilization of the crystal structure is involved as one of the factors.

[0055] The lithium-containing composite oxide of the present embodiment has a hexagonal crystal structure. In the case of a hexagonal crystal, from the Bragg's equation of the following formula (2) and the interplanar spacing d in the hexagonal crystal of the following formula (3), as a value depending on the plane indices hkl, (sinθ ｈｋｌ ００３ ) ２ / {(sinθ ０１８ ) ２ -(sinθ ０１２ ) ２} can be calculated. In a perfect hexagonal crystal, it is known that this value depending on the plane indices hkl becomes a constant 0.15.

[0056] Bragg's equation: 2d ｈｋｌ sinθ ｈｋｌ =λ...(2) However, in the formula (2), d ｈｋｌ is the interplanar spacing and λ is the X-ray wavelength.

[0057]

[0058] However, in the formula (3), a and c are the lattice constants of the hexagonal crystal and are different from the Ni ratio and the molar ratio of M1. That is, based on the peak position information of the powder X-ray diffraction pattern of the lithium-containing composite oxide, the value depending on the above-mentioned plane indices hkl is calculated, and the deviation amount from 0.15 which is the reference value of the hexagonal crystal is calculated. Thereby, the strain from the perfect hexagonal crystal in the crystal structure of the lithium-containing composite oxide can be evaluated.

[0059] In the lithium-containing composite oxide according to the present embodiment, although not intended to be limiting, the above deviation amount is, in absolute value, 2×10 －3 ​Preferably, it is 3.5 × 10 －４ The following is more preferable: The smaller the above deviation, the closer the crystal structure becomes to a perfect hexagonal crystal, leading to greater stability and thus contributing to improved battery performance.

[0060] [Method for Producing Lithium-Containing Composite Oxides] The lithium-containing composite oxide of this embodiment can be produced, for example, by the method described below. Note that the manufacturing method described herein is just one example, and the method for producing lithium-containing composite oxides is not limited to this method. The method for producing lithium-containing composite oxides includes, for example, a mixing step, a calcination step, a washing step, and a drying step.

[0061] In the mixing step, a Li compound is mixed with a metal hydroxide containing Ni, Mn, and optionally any metal element M1, and optionally a compound containing additive element M2. The resulting mixture is then fired in the next firing step to obtain a fired product.

[0062] Examples of Li 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.

[0063] Metal hydroxides can be obtained by generally known methods, such as the coprecipitation method. When using the coprecipitation method, for example, an alkaline solution such as sodium hydroxide is added dropwise while stirring a solution of Ni, Mn, and optionally any metal element M1 (e.g., nitrate), and the pH is adjusted to the alkaline side (e.g., 8.5 to 12.5). In this way, the metal hydroxide is precipitated (coprecipitation). Alternatively, a metal oxide obtained by calcining a metal hydroxide may be used. The calcination temperature may be lower than that of the calcination process described later. Specifically, for example, 600°C or lower is preferred, and 300 to 500°C is also acceptable.

[0064] The Li compound and the metal hydroxide are mixed in a ratio that satisfies the molar ratios of x, a to c described above.

[0065] Compounds containing the additive element M2 can be, for example, oxides, hydroxides, chlorides, carbonates, sulfates, or phosphates containing the additive element M2. Compounds containing the additive element M2 may also be composite compounds containing other metal elements such as Li in addition to the additive element M2. By adjusting the presence or absence and content of these additives, the crystal structure of the lithium-containing composite oxide, i.e., the peak positions of each lattice plane in the powder X-ray diffraction pattern, can be adjusted.

[0066] In the firing process, the mixture obtained in the mixing process is fired, for example, under an oxygen atmosphere (under a gas flow with an oxygen concentration of 80% or more). The firing process may be multi-stage firing. An example of multi-stage firing is to set the heating rate in the temperature range of 450°C to 680°C to 1.0°C / min to 5.5°C / min, and the maximum temperature reached to 850°C to 1100°C. The heating rate from 680°C to the maximum temperature may be 0.1°C / min to 3.5°C / min. The holding time at the maximum temperature may be 1 hour to 30 hours.

[0067] In the washing step, the calcined product obtained in the calcination step is washed with water and dehydrated to obtain a cake-like composition. Washing and dehydration can be carried out by known methods and conditions. A compound containing additive element M2 may be added to the water used for washing or to the obtained cake-like composition. That is, the compound containing additive element M2 may be added in the washing step, either in addition to or instead of the mixing step. By adjusting the presence or absence and content of these additives, the crystal structure of the lithium-containing composite oxide, i.e., the peak positions of each lattice plane in the powder X-ray diffraction pattern, can be adjusted.

[0068] In the drying step, the cake-like composition obtained in the washing step is dehydrated, dried, and crushed as necessary to obtain a powder-like composition. The drying step may be carried out under a vacuum atmosphere. For example, the drying temperature is 150°C to 400°C, and the drying time is 0.5 hours to 15 hours. Note that the washing and drying steps may be omitted.

[0069] <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.

[0070] 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 ｘ Si-containing compounds represented by (0.5 ≤ x ≤ 1.6), or Li ２ｙ SiO （２＋ｙ） A Si-containing compound in which fine Si particles are dispersed in a lithium silicate phase represented by (0 < y < 2) may be used in combination with graphite.

[0071] Examples of binders included in the negative electrode mixture layer include styrene-butadiene rubber (SBR), nitrile-butadiene rubber (NBR), carboxymethylcellulose (CMC) or its salts, polyacrylic acid (PAA) or its salts (PAA-Na, PAA-K, etc., or partially neutralized salts), and polyvinyl alcohol (PVA). These may be used individually or in combination of two or more types.

[0072] <Separator> The separator 13 is made of a porous sheet having ion permeability and insulating properties. Specific examples of porous sheets include microporous thin films, woven fabrics, and nonwoven fabrics. Suitable materials for the separator 13 include polyethylene, polyolefins such as polypropylene, and cellulose. The separator 13 may have a single-layer structure or a multi-layer structure. In addition, a heat-resistant resin layer, such as aramid resin, may be formed on the surface of the separator 13.

[0073] 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 inorganic fillers include oxides containing metal elements such as Ti, Al, Si, and Mg, and phosphoric acid compounds. The filler layer can be formed by coating the surface of the positive electrode 11, the negative electrode 12, or the separator 13 with a slurry containing the filler.

[0074] <Non-aqueous electrolytes> Non-aqueous electrolytes have ionic conductivity (for example, lithium ion conductivity). Non-aqueous electrolytes may be liquid electrolytes (electrolytes) or solid electrolytes.

[0075] 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).

[0076] 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).

[0077] 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-dimethoxyethaneethyl 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.

[0078] 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.

[0079] 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.

[0080] 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.

[0081] Examples of phenolic compounds include phenol and hydroxytoluene. Examples of benzene compounds include fluorobenzene, hexafluorobenzene, and cyclohexylbenzene (CHB).

[0082] 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.

[0083] 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.

[0084] The present disclosure will be further illustrated by the following examples, but the present disclosure is not limited to these examples.

[0085] <<Sample Preparation>> Lithium-containing composite oxides for Examples 1-14 and Comparative Examples 1-3 shown in Table 1 were prepared. These lithium-containing composite oxides were then used as positive electrode active materials to manufacture secondary batteries. In Table 1, the ratio of the added element M2 to the total number of moles of Ni, Mn, and M1 is shown in mole percent (molar ratio × 100).

[0086]

[0087] <Example 1> [Preparation of positive electrode active material] Ni obtained by coprecipitation method ａ Mn ｂ (OH) ２ The powder was calcined in air at a heating rate of 5.0°C / min from room temperature to 150°C, and then calcined again at a heating rate of 1.0°C / min to 400°C to obtain a Ni,Mn-containing composite oxide. LiOH, Ni,Mn-containing composite oxide, and WO ３ And, Nb ２ O ５ And Ca(OH) ２ The materials were mixed in a molar ratio of Li:Total amount of Ni and Mn (a+b):W:Nb:Ca = x:1:0.002:0.002:0.0025 to obtain a mixture (mixing step). This mixture was calcined in two stages under an oxygen stream with an oxygen concentration of 90% or more (flow rate of 0.15 L / min to 0.35 L / min per 1 L of furnace volume). Specifically, the temperature was raised from room temperature to 670°C over 5 hours, and then raised from 670°C to 860°C at a rate of 1°C / min. After that, it was held at 860°C for 5 hours to obtain a calcined product (calcination step). The obtained calcined product was washed with water to remove excess lithium (washing step), dehydrated, dried, and then crushed to obtain a lithium-containing composite oxide (drying step). The obtained lithium-containing composite oxide was used as the positive electrode active material.

[0088] [Preparation of the positive electrode] The above positive electrode active material, acetylene black (AB), and polyvinylidene fluoride were mixed in a mass ratio of 92:5:3, 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. An exposed portion was provided on a part of the positive electrode in which the surface of the positive electrode core was exposed.

[0089] [Preparation of Non-Aqueous Electrolyte] Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) were mixed in a volume ratio of 20:5:75. 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 1.35 mol / liter.

[0090] [Preparation of Test Cell] A positive electrode lead was attached to the exposed portion of the positive electrode, and a negative electrode lead was attached to the lithium metal foil serving as the negative electrode. A wound electrode body was then constructed by spirally winding the positive and negative electrodes together via a polyolefin separator. This electrode body was then housed in an outer casing made of aluminum laminate sheet, and after injecting the non-aqueous electrolyte, the opening of the outer casing was sealed to obtain a test cell for a secondary battery.

[0091] <Example 2> In the preparation of the positive electrode active material, a test cell was prepared in the same manner as in Example 1, except for the following procedure. That is, the values ​​of a and b were set to the values ​​shown in Table 1, and LiOH, Ni,Mn-containing composite oxide, and WO ３ And, Nb ２ O ５ And Ca(OH) ２ And, ZrO ２ The two were mixed in a molar ratio such that the total amount of Li, Ni, and Mn (a+b): W:Nb:Ca:Zr = x:1:0.003:0.003:0.001:0.002 to obtain a mixture.

[0092] <Example 3> In the preparation of the positive electrode active material, a test cell was prepared in the same manner as in Example 1, except for the following procedure. That is, the values ​​of a and b were set to the values ​​shown in Table 1, and LiOH, Ni,Mn-containing composite oxide, and Sb ２ O ３ And, Ta ２ O ５ The two were mixed in a molar ratio such that the total amounts of Li, Ni, and Mn (a+b):Sb:Ta = x:1:0.003:0.00025 to obtain a mixture.

[0093] <Example 4> In the preparation of the positive electrode active material, a test cell was prepared in the same manner as in Example 1, except for the following procedure. That is, the values ​​of a and b were set to the values ​​shown in Table 1, and LiOH, Ni,Mn-containing composite oxide, and WO ３ And, Nb ２ O ５ And, Bi ２ O ３ The two were mixed in a molar ratio such that the total amount of Li, Ni, and Mn (a+b): W:Nb:Bi = x:1:0.005:0.001:0.001 to obtain a mixture.

[0094] <Example 5> In the preparation of the positive electrode active material, a test cell was prepared in the same manner as in Example 1, except for the following procedure. That is, the values ​​of a and b were set to the values ​​shown in Table 1, and LiOH, Ni,Mn-containing composite oxide, and WO ３ And, Sb ２ O ３ And Ca(OH) ２ The two were mixed in a molar ratio such that Li:Total amount of Ni and Mn (a+b):W:Sb:Ca = x:1:0.005:0.003:0.0025 to obtain a mixture. Furthermore, when washing the calcined product with water, nitric acid (Sr) was added to the water used for washing so that in the obtained lithium-containing composite oxide, the total amount of Ni and Mn (a+b):Sr = 1:0.00025.

[0095] <Example 6> In the preparation of the positive electrode active material, a test cell was prepared in the same manner as in Example 1, except for the following procedure. That is, the values ​​of a and b were set to the values ​​shown in Table 1, and LiOH, Ni,Mn-containing composite oxide, and WO ３ And, MoO ３The two were mixed in a molar ratio such that the total amount of Li, Ni, and Mn (a+b):W:Mo = x:1:0.005:0.0025 to obtain a mixture.

[0096] <Example 7> In the preparation of the positive electrode active material, a test cell was prepared in the same manner as in Example 1, except for the following procedure. That is, the values ​​of a and b were set to the values ​​shown in Table 1, and LiOH, Ni,Mn-containing composite oxide, and V ２ O ５ The two were mixed in a molar ratio such that the total amount of Li, Ni, and Mn (a+b):V = x:1:0.005 to obtain a mixture.

[0097] <Examples 8 and 9> Test cells were prepared in the same manner as in Example 1, except that the positive electrode active material was prepared using the following procedure.

[0098] Ni obtained by coprecipitation method ａ Mn ｂ Co ｃ (OH) ２ The powder was calcined in air at a heating rate of 5.0°C / min from room temperature to 150°C, and then calcined again at a heating rate of 1.0°C / min to 400°C to obtain a Ni, Mn, Co-containing composite oxide. LiOH, Ni, Mn, Co-containing composite oxide, and WO ３ The materials were mixed in a molar ratio of Li:Ni, Mn, and Co (a+b+c):W = x:1:0.006 to obtain a mixture. This mixture was calcined in two stages under an oxygen stream with an oxygen concentration of 90% or more (flow rate of 0.15 L / min to 0.35 L / min per 1 L of furnace volume). Specifically, the temperature was raised from room temperature to 670°C over 5 hours, and then raised from 670°C to 860°C at a rate of 1°C / min. After that, it was held at 860°C for 5 hours to obtain the calcined product. The obtained calcined product was washed with water to remove excess lithium, dehydrated, dried, and then crushed to obtain a lithium-containing composite oxide. The obtained lithium-containing composite oxide was used as the positive electrode active material.

[0099] <Examples 10-14> Test cells were prepared in the same manner as in Example 1, except that the positive electrode active material was prepared using the following procedure.

[0100] Ni obtained by coprecipitation method ａ Mn ｂ (OH)２ The powder was calcined in air at a heating rate of 5.0°C / min from room temperature to 150°C, and then calcined again at a heating rate of 1.0°C / min to 400°C to obtain a Ni,Mn-containing composite oxide. LiOH and the Ni,Mn-containing composite oxide were mixed in a molar ratio of Li:Ni and Mn total amount (a+b) = x:1 to obtain a mixture. This mixture was calcined in two stages under an oxygen stream with an oxygen concentration of 90% or more (flow rate of 0.15 L / min to 0.35 L / min per 1 L of furnace volume). Specifically, the temperature was raised from room temperature to 670°C over 5 hours, and then raised from 670°C to 860°C at a rate of 1°C / min. After that, it was held at 860°C for 5 hours to obtain the calcined product. The obtained calcined product was washed with water to remove excess lithium, dehydrated, dried, and then crushed to obtain a lithium-containing composite oxide. The obtained lithium-containing composite oxide was used as the positive electrode active material.

[0101] <Comparative Example 1> In the preparation of the positive electrode active material, a test cell was prepared in the same manner as in Example 1, except for the following procedure. That is, the values ​​of a and b were set to the values ​​shown in Table 1, and LiOH, Ni,Mn-containing composite oxide, and Al ２ O ３ And, TiO ２ The two were mixed in a molar ratio such that the total amount of Li, Ni, and Mn (a+b):Al:Ti = x:1:0.02:0.01 to obtain a mixture.

[0102] <Comparative Example 2> In the preparation of the positive electrode active material, a test cell was prepared in the same manner as in Example 1, except for the following procedure. That is, the values ​​of a and b were set to the values ​​shown in Table 1, and LiOH, Ni, Mn-containing composite oxide, and Fe ２ O ３ And, B ２ O ３ The two were mixed in a molar ratio such that the total amount of Li, Ni, and Mn (a+b): Fe:B = x:1:0.03:0.005 to obtain a mixture.

[0103] <Comparative Example 3> In the preparation of the positive electrode active material, a test cell was prepared in the same manner as in Example 1, except for the following procedure. That is, the values ​​of a and b were set to the values ​​shown in Table 1, and LiOH, Ni,Mn-containing composite oxide, and TiO ２ And, B ２ O３ The two were mixed in a molar ratio such that the total amount of Li, Ni, and Mn (a+b):Ti:B = x:1:0.03:0.005 to obtain a mixture.

[0104] <<Powder X-ray Diffraction Measurement>> The lithium-containing composite oxides of each example and each comparative example were subjected to the powder X-ray diffraction measurement described above.

[0105] Correction coefficients for each peak position difference and Ni ratio a were calculated from the powder X-ray diffraction patterns of the lithium-containing composite oxides of each example and comparative example using the method described above. Then, values ​​for each peak position difference were determined using these correction coefficients. These results are shown in Tables 2 and 3.

[0106]

[0107]

[0108] Furthermore, the deviation from the hexagonal standard value of 0.15 was calculated from the powder X-ray diffraction patterns of the lithium-containing composite oxides of each example and comparative example using the method described above. The results are shown in Table 4.

[0109]

[0110] ≪Evaluation of Charging and Discharging Capacity≫ The fabricated test cell was charged to 4.5V (against Li metal) with a constant current of 0.2C at a temperature of 25°C, and then charged to 0.02C with a constant voltage of 4.5V. After that, it was discharged to 2.5V with a constant current of 0.2C. This charge-discharge cycle was performed three times, and the discharge capacity of the third cycle was measured. The charging capacity was calculated as the cumulative charging capacity over three cycles using the following formula. The results are shown in Table 3 and Figures 3 to 5 above.

[0111] 3-cycle cumulative charge capacity = (1st cycle charge capacity - 1st cycle discharge capacity) + (2nd cycle charge capacity - 2nd cycle discharge capacity) + (3rd cycle charge capacity) <Discussion> As shown in Table 3 and Figure 5, in Examples 1 to 14, where the value related to the 018-012 peak position difference satisfies the above-mentioned numerical range, the 3-cycle cumulative charge capacity was 235.0 mAh / g or higher, which is a higher value for the 3-cycle cumulative charge capacity compared to Comparative Examples 1 to 3, which do not satisfy the above-mentioned numerical range. In addition, the discharge capacity in the 3rd cycle was also high in the examples, generally 200.0 mAh / g or higher. From this, it can be seen that high capacity can be achieved in secondary batteries using the positive electrode active material containing lithium-containing composite oxide according to this embodiment. Furthermore, it was found that high battery capacity can generally be obtained when the values ​​related to each peak position difference other than the value related to the 018-012 peak position difference satisfy the above-mentioned range.

[0112] Furthermore, as shown in Table 4, it was found that the deviation from the hexagonal standard value of 0.15 tended to be smaller in many examples than in the comparative examples. This suggests that adjusting the peak position difference and the values ​​related to each peak position difference may stabilize the crystal structure, potentially contributing to higher capacity secondary batteries.

[0113] This disclosure is further illustrated by the following embodiments.

[0114] Configuration 1: A positive electrode active material for a non-aqueous electrolyte secondary battery comprising a lithium-containing composite oxide, wherein the lithium-containing composite oxide has the general formula Li ｘ Ni ａ Mn ｂ M1 ｃ M2 ｄ O ２ (wherein the formula, 0.80 ≤ x ≤ 1.2, 0.50 ≤ a ≤ 0.95, 0.05 ≤ b ≤ 0.50, 0 ≤ c ≤ 0.20, a + b + c = 1, 0 ≤ d ≤ 0.10, M1 is at least one element from Co and Al, and M2 is at least one metallic element other than Li, Ni and Mn), and the peak position 2θ of the (012) plane in the powder X-ray diffraction pattern of the lithium-containing composite oxide is given by (wherein the formula, 0.80 ≤ x ≤ 1.2, 0.50 ≤ a ≤ 0.95, 0.05 ≤ b ≤ 0.50, 0 ≤ c ≤ 0.20, a + b + c = 1, 0 ≤ d ≤ 0.10, M1 is at least one element from Co and Al, and M2 is at least one metallic element other than Li, Ni and Mn), and the peak position 2θ of the (012) plane in the powder X-ray diffraction pattern of the lithium-containing composite oxide. ０１２and the peak position 2θ of the (018) plane ０１８ The value relating to the difference between [(2θ) ０１８ -2θ ０１２ A positive electrode active material for a non-aqueous electrolyte secondary battery, wherein the ratio of [-0.5031 × a] is 25.60 or more and 31.05 or less.

[0115] Configuration 2: Peak position 2θ of the (104) plane in the powder X-ray diffraction pattern. １０４ and the aforementioned 2θ ０１８ The value relating to the difference between [(2θ) ０１８ -2θ １０４ A positive electrode active material for a non-aqueous electrolyte secondary battery according to configuration 1, wherein [-0.3749 × a] is 19.61 or more and 29.49 or less.

[0116] Configuration 3: Peak position 2θ of the (101) plane in the powder X-ray diffraction pattern. １０１ and the aforementioned 2θ ０１８ The value relating to the difference between [(2θ) ０１８ -2θ １０１ A positive electrode active material for a non-aqueous electrolyte secondary battery according to configuration 1 or configuration 2, wherein [-0.5877 × a] is 27.19 or more and 45.55 or less.

[0117] Configuration 4: Peak position 2θ of the (003) plane in the powder X-ray diffraction pattern. ００３ (006) Peak position 2θ ００６ The value relating to the difference between [(2θ) ００６ -2θ ００３ A positive electrode active material for a non-aqueous electrolyte secondary battery, as described in any one of configurations 1 to 3, wherein [-0.2292 × a] is 19.01 or more and 25.49 or less.

[0118] Configuration 5: Peak position 2θ of the (003) plane in the powder X-ray diffraction pattern. ００３ and the aforementioned 2θ ０１８ The value relating to the difference between [(2θ) ０１８ -2θ ００３ A positive electrode active material for a non-aqueous electrolyte secondary battery, as described in any one of configurations 1 to 4, wherein [-0.1139 × a] is 45.46 or more and 49.29 or less.

[0119] Configuration 6: The 2θ in the powder X-ray diffraction pattern ０１２ (104) Peak position 2θ １０４The value relating to the difference between [(2θ) １０４ -2θ ０１２ A positive electrode active material for a non-aqueous electrolyte secondary battery according to any one of configurations 1 to 5, wherein [-0.1282 × a] is 6.00 or more and 11.87 or less.

[0120] Configuration 7: Peak position 2θ of the (003) plane in the powder X-ray diffraction pattern. ００３ (104) Peak position 2θ １０４ The value relating to the difference between [(2θ) １０４ -2θ ００３ A positive electrode active material for a non-aqueous electrolyte secondary battery according to any one of configurations 1 to 6, wherein [a] + 0.2611 × a] is 25.86 or more and 30.11 or less.

[0121] Configuration 8: The positive electrode active material for a non-aqueous electrolyte secondary battery according to any one of Configurations 1 to 7, wherein M2 is at least one metallic element selected from the group consisting of Ca, Sr, Zr, Mo, W, V, Nb, Ta, Sb, and Bi.

[0122] Configuration 9: A non-aqueous electrolyte secondary battery comprising a positive electrode containing the positive electrode active material for non-aqueous electrolyte secondary batteries described in any one of Configurations 1 to 8, a negative electrode, and a non-aqueous electrolyte.

[0123] 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 positive electrode active material for a non-aqueous electrolyte secondary battery containing a lithium-containing composite oxide, wherein the lithium-containing composite oxide has the general formula Li ｘ Ni ａ Mn ｂ M1 ｃ M2 ｄ O ２ (where 0.80 ≤ x ≤ 1.2, 0.?? ≤ a ≤ 0.95, 0.05 ≤ b ≤ 0.50, 0 ≤ c ≤ 0.20, a + b + c = 1, 0 ≤ d ≤ 0.10, M1 is at least one element of Co and Al, and M2 is at least one metal element other than Li, Ni, and Mn), and the value [(2θ ０１２ of the peak position of the (012) plane and 2θ ０１８ of the peak position of the (018) plane in the powder X-ray diffraction pattern of the lithium-containing composite oxide) - 2θ ０１８ - 2θ ０１２ ) - 0.5031 × a] is 25.60 or more and 31.05 or less. A positive electrode active material for a non-aqueous electrolyte secondary battery. It should be noted that there seems to be an unclear value "0.??" in the formula in the original text which needs to be confirmed and corrected for a more accurate translation.

2. Peak position 2θ of the (104) plane in the powder X-ray diffraction pattern. １０４ and the aforementioned 2θ ０１８ The value relating to the difference between [(2θ) ０１８ -2θ １０４ The positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 1, wherein [-0.3749 × a] is 19.61 or more and 29.49 or less.

3. Peak position 2θ of the (101) plane in the powder X-ray diffraction pattern. １０１ and the aforementioned 2θ ０１８ The value relating to the difference between [(2θ) ０１８ -2θ １０１ The positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 1, wherein [-0.5877 × a] is 27.19 or more and 45.55 or less.

4. Peak position 2θ of the (003) plane in the powder X-ray diffraction pattern. ００３ (006) Peak position 2θ ００６ The value relating to the difference between [(2θ) ００６ -2θ ００３ The positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 1, wherein [-0.2292 × a] is 19.01 or more and 25.49 or less.

5. Peak position 2θ of the (003) plane in the powder X-ray diffraction pattern. ００３ and the aforementioned 2θ ０１８ The value relating to the difference between [(2θ) ０１８ -2θ ００３ The positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 1, wherein [-0.1139 × a] is 45.46 or more and 49.29 or less.

6. The 2θ in the powder X-ray diffraction pattern. ０１２ (104) Peak position 2θ １０４ The value relating to the difference between [(2θ) １０４ -2θ ０１２ The positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 1, wherein [-0.1282 × a] is 6.00 or more and 11.87 or less.

7. Peak position 2θ of the (003) plane in the powder X-ray diffraction pattern. ００３ (104) Peak position 2θ １０４ The value relating to the difference between [(2θ) １０４ -2θ ００３ The positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 1, wherein [a] + 0.2611 × a] is 25.86 or more and 30.11 or less.

8. The positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 1, wherein M2 is at least one metallic element selected from the group consisting of Ca, Sr, Zr, Mo, W, V, Nb, Ta, Sb, and Bi.

9. 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 any one of claims 1 to 8, a negative electrode, and a non-aqueous electrolyte.

Images