Nonaqueous electrolyte secondary battery and battery pack

Abstract

A non-aqueous electrolyte secondary battery which is characterized by being provided with an electrode body having a structure in which a positive electrode and a negative electrode are laminated with a separator interposed therebetween, the positive electrode active material being secondary particles in which primary particles are aggregated, and a sulfonic acid compound represented by formula (I) being present on the surface of the secondary particles, pressure of 8.00 * 10 <-2 > MPa or more is applied to the electrode body by applying pressure from the outside of the outer shell in the lamination direction of the positive electrode, the negative electrode, and the separator. (In the formula, A is a group 1 element or a group 2 element, R is a hydrocarbon group, and n is 1 or 2)

Description

Technical Field

[0001] This disclosure relates to non-aqueous electrolyte secondary batteries and battery packs having multiple non-aqueous electrolyte secondary batteries connected together. Background Technology

[0002] In recent years, the use of non-aqueous electrolyte secondary batteries in power supplies for electric vehicles and / or energy storage devices for the efficient utilization of natural energy has been expanding. The positive electrode has a significant impact on battery characteristics, including battery capacity, output characteristics, and cycle characteristics; therefore, extensive research has been conducted on the positive electrode. Patent Document 1 discloses a non-aqueous electrolyte secondary battery having a flat electrode body with a structure in which a positive and negative electrode are stacked with a separator between them. As the positive electrode active material, a lithium-containing transition metal composite oxide with compounds containing elements such as Al, Mg, Ti, Zr, and W attached to the particle surface is used. Furthermore, Patent Document 1 discloses that by applying a prescribed pressure to the flat portion of the non-aqueous electrolyte secondary battery from the outside, the expansion of the positive electrode active material is suppressed, thereby improving the battery's cycle characteristics.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent No. 6509989 Summary of the Invention

[0006] In non-aqueous electrolyte secondary batteries, achieving both high initial charge-discharge efficiency and excellent cycle characteristics is a crucial challenge. Existing technologies, including Patent Document 1, cannot adequately address this challenge, and there is still significant room for improvement.

[0007] The non-aqueous electrolyte secondary battery of this disclosure is characterized in that it is a non-aqueous electrolyte secondary battery having an electrode body and a housing for housing the electrode body. The electrode body has a structure in which a positive electrode and a negative electrode are stacked together with a separator between them. The positive electrode has a positive electrode core and a positive electrode agent layer formed on the surface of the positive electrode core and containing a positive electrode active material. The positive electrode active material contains a lithium-containing transition metal composite oxide with a layered structure, and the lithium-containing transition metal composite oxide is composed of the general formula Li... x Ni a Co b Mn c M d O 2-y(In the formula, 0.80 < x < 1.20, 0.75 < a ≤ 0.95, 0 ≤ b ≤ 0.15, 0 ≤ c ≤ 0.25, 0 ≤ d ≤ 0.10, 0 ≤ y < 0.05, a + b + c + d = 1, and M is at least one element selected from the group consisting of W, Mg, Mo, Nb, Ti, Si, Al, and Zr), and is a secondary particle formed by aggregation of primary particles. A sulfonic acid compound represented by formula (I) is present on the surface of the secondary particle. By applying pressure from the outside of the outer casing in the stacking direction of the positive electrode, negative electrode, and separator, a pressure of 8.00×10 -2 MPa or more is applied to the electrode body.

[0008]

[0009] (In formula (I), A is a Group I element or a Group II element, R is a hydrocarbon group, and n is 1 or 2.)

[0010] A battery pack according to one aspect of the present disclosure is characterized in that it includes a plurality of the above non-aqueous electrolyte secondary batteries, the plurality of non-aqueous electrolyte secondary batteries are arranged in the stacking direction of the positive electrode, negative electrode, and separator, and are mutually constrained in the arrangement direction.

[0011] According to the non-aqueous electrolyte secondary battery according to one aspect of the present disclosure, the initial charge-discharge efficiency and cycle characteristics can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 is a perspective view showing the appearance of a non-aqueous electrolyte secondary battery as an example of an embodiment.

[0013] Figure 2 is Figure 1 a cross-sectional view taken along line AA in

[0014] Figure 3 is a perspective view showing a battery pack as an example of an embodiment. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0015] The layered rock salt structure of the lithium-containing transition metal composite oxide has a transition metal layer such as Ni, a Li layer, and an oxygen layer. Li ions present in the Li layer reversibly enter and exit, thereby performing the charge-discharge reaction of the battery. Usually, a lithium-containing transition metal composite oxide of the lithium nickelate system containing Ni as a main component is known as a high-capacity positive electrode active material. From the viewpoint of increasing the capacity of the battery, the content rate of Ni in the lithium-containing transition metal composite oxide is preferably more than 75 mol% with respect to the total molar number of metal elements other than Li.

[0016] The inventors' research indicates that by presenting a sulfonic acid compound represented by formula (I) on the surface of secondary particles of a lithium-containing transition metal composite oxide used as the positive electrode active material, a non-aqueous electrolyte secondary battery with improved initial charge-discharge efficiency can be achieved. This is believed to be because the sulfonic acid compound reduces the reaction resistance in the positive electrode, making it possible to increase the depth of charge-discharge. However, the increased depth of charge-discharge due to the reduced reaction resistance introduces a new challenge: decreased cycle performance. This is presumably because the increased depth of charge-discharge leads to a larger volume change in the lattice of the positive electrode active material, resulting in particle breakage and side reactions between the broken positive electrode active material particles and the non-aqueous electrolyte.

[0017] Therefore, the inventors further conducted repeated studies and discovered that in a non-aqueous electrolyte secondary battery having an electrode body having a structure in which the positive and negative electrodes are stacked with a separator between them, using a lithium-containing transition metal composite oxide with a sulfonic acid compound attached to the surface of the secondary particles as the positive electrode active material, and applying an 8.00 × 10⁻⁶ ppm electrode material from the outside towards the stacking direction of the electrode plates... -2 A pressure exceeding MPa is achieved, enabling the development of non-aqueous electrolyte secondary batteries that improve initial charge-discharge efficiency and cycle characteristics while maintaining high capacity. This is presumably due to the application of a pressure of 8.00 × 10 MPa to the electrode body. -2 Pressures above MPa can suppress the breakage of positive electrode active material particles during charging and discharging, even when sulfonic acid compounds are present on the surface of secondary particles.

[0018] 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 the accompanying drawings. It should be noted that solutions formed by selectively combining the constituent elements of the various embodiments and variations described below are included within the scope of this disclosure. It should also be noted that the accompanying drawings referred to in the description of the embodiments are schematic illustrations, and sometimes the size ratios of the constituent elements depicted in the drawings differ from the actual objects. Furthermore, in this specification, "~" refers to the range including the upper and lower limits before and after "~".

[0019] Hereinafter, as a non-aqueous electrolyte secondary battery, a square battery in which the electrode body 11 is housed in a square battery casing 14, which serves as the outer casing, is exemplified. However, the outer casing of the battery is not limited to a square battery casing. The non-aqueous electrolyte secondary battery disclosed herein may also be a laminated battery having an outer casing composed of a laminate comprising a metal layer and a resin layer.

[0020] Figure 1 This is a perspective view showing a non-aqueous electrolyte secondary battery 10 as an example of an embodiment. Figure 2 yes Figure 1 A sectional view along line AA in the diagram. (Example) Figure 1 and Figure 2 As illustrated, the non-aqueous electrolyte secondary battery 10 includes an electrode body 11 and a non-aqueous electrolyte (not shown).

[0021] The electrode body 11 has a strip-shaped positive electrode 20, a strip-shaped negative electrode 21, and a separator 22 sandwiched between the positive electrode 20 and the negative electrode 21. The electrode body 11 has a wound structure in which the positive electrode 20 and the negative electrode 21 are wound into a spiral shape with the separator 22 in between. It should be noted that the structure of the electrode body 11 is not limited to the wound type, and can also be a stacked type in which multiple positive electrodes and multiple negative electrodes are alternately stacked one sheet with the separator in between.

[0022] The non-aqueous electrolyte secondary battery 10 has a square battery casing 14 that serves as a housing for the electrode body 11 and the non-aqueous electrolyte. The battery casing 14 is 8.00 × 10⁻⁶ cm², extending from the outside along the stacking direction α (hereinafter sometimes simply referred to as "stacking direction α") of the positive electrode 20, negative electrode 21, and separator 22. -2 The electrode body 11 is pressed with a pressure of 8.00 × 10 MPa or higher. Therefore, the electrode body 11 is pressed from both sides of the stacking direction α at a pressure of 8.00 × 10 MPa. -2 Pressing with a pressure of over MPa suppresses the breakage of the positive electrode active material particles constituting the positive electrode 20, as well as the side reactions between the broken positive electrode active material and the non-aqueous electrolyte. As a result, even in the presence of sulfonic acid compounds on the surface of the particles, cycling characteristics are improved.

[0023] In this embodiment, the non-aqueous electrolyte secondary battery 10 is modularized so that the electrode body 11 is pressed from both sides in the stacking direction α (see below). Figure 3 It should be noted that the expansion of the electrode body 11 during charging generates stress that causes the battery casing 14 to expand outward, and generates a reaction force that counteracts this stress.

[0024] The battery casing 14 is a square metal casing consisting of a roughly box-shaped casing body 15 and a sealing body 16 that blocks the opening of the casing body 15. A positive terminal 12, electrically connected to the positive electrode 20, and a negative terminal 13, electrically connected to the negative electrode 21, are provided on the sealing body 16. The lead of the positive electrode is directly connected to the positive terminal 12 or through other conductive members. The lead of the negative electrode is directly connected to the negative terminal 13 or through other conductive members. Hereinafter, for ease of explanation, the orientation of the positive terminal 12 and the negative terminal 13 will be referred to as the "lateral direction" of the battery casing 14, etc., and the direction orthogonal to the stacking direction α and the lateral direction will be referred to as the "vertical direction".

[0025] The outer casing 15 has a flat shape that is longer in the lateral and vertical directions than in the stacking direction α. ​​The outer casing 15 and the sealing body 16 are, for example, made of a metallic material with aluminum as the main component. To ensure insulation, an electrode holder may be mounted on its inner surface. The electrode holder is, for example, a plate with a thickness of 0.05 mm to 0.5 mm formed from resin such as polypropylene. The sealing body 16 has, for example, a generally rectangular shape that is longer in the lateral direction, and its periphery is fused to the periphery of the opening of the outer casing 15.

[0026] Through holes (not shown) are formed on both sides of the sealing body 16, through which the positive terminal 12 and the negative terminal 13 are inserted into the battery casing 14. The positive terminal 12 and the negative terminal 13 are fixed to the sealing body 16, for example, by insulating members 17 disposed in the through holes. It should be noted that a venting mechanism (not shown) is usually provided on the sealing body 16.

[0027] Figure 3 This is a perspective view of a battery pack 30 composed of multiple non-aqueous electrolyte secondary batteries 10. (See diagram below.) Figure 3 As illustrated, the battery pack 30 includes: a battery module 31 formed by arranging a plurality of non-aqueous electrolyte secondary batteries 10 in the stacking direction α, a plurality of spacers 32, and a pair of end plates 33. The spacers 32 are insulating members respectively sandwiched between adjacent non-aqueous electrolyte secondary batteries 10. The end plates 33 are members that press the battery module 31 from both sides in the stacking direction α with a predetermined force. The pressing force generated by the end plates 33 is 8.00 × 10⁻⁶. -2 MPa or above.

[0028] The battery pack 30 includes bind bars 35 and 36, which are fixed to a pair of end plates 33 that clamp the battery module 31 from both sides in the stacking direction α (the direction in which the multiple non-aqueous electrolyte secondary batteries 10 are arranged), and are used to bundle the batteries constituting the battery module 31. The bind bars 35 and 36 have the function of maintaining the bundled state of the batteries together with the end plates 33 and holding the batteries together. The bind bar 35 is installed on one lateral side of the battery module 31 along the stacking direction α, and the bind bar 36 is installed on the other lateral side of the battery module 31 along the stacking direction α.

[0029] In this embodiment, the orientation of identical non-aqueous electrolyte secondary batteries 10 is changed, and adjacent batteries are arranged with the lateral positions of their positive and negative terminals opposite to each other. In this case, the positive terminal 12 and the negative terminal 13 are arranged alternately along the stacking direction α. ​​The battery pack 30 includes a busbar 34 that electrically connects adjacent non-aqueous electrolyte secondary batteries 10 to each other. Figure 1 In the example shown, each non-aqueous electrolyte secondary battery 10 is connected in series via busbar 34, but the connection method of each battery is not limited to this.

[0030] In the battery pack 30, the non-aqueous electrolyte secondary batteries 10 constituting the battery module 31 are bundled and pressed together by fixing connecting rods 35 and 36 to a pair of end plates 33 and pressing each end plate 33 toward the battery module 31. The end plates 33 are, for example, plate-shaped bodies made of resin, and are formed to be slightly larger than the non-aqueous electrolyte secondary batteries 10. Bolt holes for fastening the connecting rods 35 and 36 are formed on the end plates 33, for example.

[0031] The following provides a detailed description of the positive electrode 20, negative electrode 21, separator 22, and non-aqueous electrolyte constituting the non-aqueous electrolyte secondary battery 10, and in particular, a detailed description of the positive electrode active material constituting the positive electrode 20.

[0032] [positive electrode]

[0033] The positive electrode 20 has a positive electrode core and a positive electrode additive layer formed on the surface of the positive electrode core. The positive electrode additive layer is preferably formed on both sides of the positive electrode core. The positive electrode core can be a foil of a metal stable within the potential range of the positive electrode 20, such as aluminum or an aluminum alloy, or a thin film of the metal disposed on its surface. The positive electrode additive layer may contain a positive electrode active material, a conductive agent, and a binder. The thickness of the positive electrode additive layer is, for example, 10 μm to 150 μm on one side of the positive electrode core. The positive electrode 20 can be manufactured, for example, by coating the surface of the positive electrode core with a positive electrode slurry containing a positive electrode active material, a conductive agent, and a binder, drying the coating, and then calendering it to form the positive electrode additive layer on both sides of the positive electrode core.

[0034] Conductive agents included in the positive electrode layer can include, for example, acetylene black (AB), carbon black (CB) such as Ketjen black, carbon nanotubes (CNT), graphene, graphite, and other carbon-based materials. One of these can be used alone, or two or more can be used in combination.

[0035] Examples of binders included in the positive electrode binder layer include fluorinated resins such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), polyimide resins, acrylic resins, and polyolefin resins. One of these can be used alone, or two or more can be used in combination.

[0036] The positive electrode active material contained in the positive electrode mixture layer includes: a lithium-containing transition metal complex oxide and a sulfonic acid compound present on the surface of the lithium-containing transition metal complex oxide. The lithium-containing transition metal complex oxide, for example, comprises secondary particles formed by the aggregation of primary particles. Here, the surface of the lithium-containing transition metal complex oxide refers to the surface of the secondary particles of the lithium-containing transition metal complex oxide or the interface where the primary particles contact each other. That is, the sulfonic acid compound is present on the surface of the secondary particles of the lithium-containing transition metal complex oxide or at the interface where the primary particles contact each other.

[0037] The particle size of the primary particles constituting the secondary particles of the lithium-containing transition metal composite oxide is, for example, 0.02 μm to 2 μm. The particle size of the primary particles is measured in the form of the diameter of the circumscribed circle in the particle image observed by a scanning electron microscope (SEM). The volume-based median particle size (D50) of the secondary particles of the lithium-containing transition metal composite oxide is, for example, 2 μm to 30 μm. D50 refers to the particle size at which the cumulative frequency in the volume-based particle size distribution reaches 50% from the smaller particle size end, and is also called the median diameter. The particle size distribution of the secondary particles of the lithium-containing transition metal composite oxide can be measured using a laser diffraction type particle size distribution measuring device (for example, manufactured by Micromeritics, MT3000II) with water as the dispersion medium.

[0038] The lithium-containing transition metal composite oxide has a layered rock salt structure. Examples of the layered rock salt structure of the lithium-containing transition metal composite oxide include a layered rock salt structure belonging to the space group R-3m, a layered rock salt structure belonging to the space group C2 / m, etc. From the viewpoints of high capacity and crystal structure stability, the lithium-containing transition metal composite oxide preferably has a layered rock salt structure belonging to the space group R-3m. The layered rock salt structure of the lithium-containing transition metal composite oxide may include a transition metal layer, a Li layer, and an oxygen layer.

[0039] The lithium-containing transition metal composite oxide is represented by the general formula Li x Ni a Co b Mn c M d O 2-y (where 0.80 < x < 1.20, 0.75 < a ≤ 0.95, 0 ≤ b ≤ 0.15, 0 ≤ c ≤ 0.25, 0 ≤ d ≤ 0.10, 0 ≤ y < 0.05, a + b + c + d = 1, and M is at least one element selected from the group consisting of W, Mg, Mo, Nb, Ti, Si, Al, and Zr). The content ratio of the elements constituting the lithium-containing transition metal composite oxide can be measured by an inductively coupled plasma emission spectroscopic analyzer (ICP-AES), an electron probe microanalyzer (EPMA), an energy dispersive X-ray analyzer (EDX), or the like.

[0040] By making the content ratio of Ni in the lithium-containing transition metal composite oxide exceed 75 mol% and be 95 mol% or less, a high-capacity battery can be obtained. The higher the content ratio of Ni, the higher-capacity battery can be obtained.

[0041] The Co content in lithium-containing transition metal composite oxides ranges from 0 mol% to 15 mol%, with Co being an arbitrary component. In other words, lithium-containing transition metal composite oxides can also be Co-free. By containing Co, lithium-containing transition metal composite oxides can improve the heat resistance of the battery.

[0042] The Mn content in lithium-containing transition metal composite oxides ranges from 0 mol% to 25 mol%, with Mn being an arbitrary component. In other words, lithium-containing transition metal composite oxides can also be Mn-free. The presence of Mn in lithium-containing transition metal composite oxides allows for crystal structure stabilization.

[0043] The content of M (M being at least one element selected from the group consisting of W, Mg, Mo, Nb, Ti, Si, Al, and Zr) in lithium-containing transition metal composite oxides ranges from 0 mol% to 10 mol%, and M is an arbitrary component. In other words, lithium-containing transition metal composite oxides may also not contain M.

[0044] A sulfonic acid compound represented by formula (I) exists on the surface of secondary particles containing lithium transition metal composite oxides.

[0045]

[0046] In the formula, A is a Group I or Group II element, R is a hydrocarbon group, and n is 1 or 2. A is preferably a Group I element. More preferably, A is Li or Na, and particularly preferably Li. The sulfonic acid compound can be present in a dotted manner, covering at least a portion of the surface of the secondary particles containing the lithium transition metal composite oxide, or it can be present in a manner covering the entire surface of the secondary particles. Additionally, the sulfonic acid compound can also be present on the surface of the primary particles containing the lithium transition metal composite oxide.

[0047] In formula (I), R is preferably an alkyl group. The alkyl group preferably has 5 or fewer carbon atoms, more preferably 3 or fewer. From the viewpoint of reducing reaction resistance, an example of preferred R is an alkyl group with 3 or fewer carbon atoms, wherein a methyl group is preferred. It should be noted that in R, some of the hydrogen atoms bonded to the carbon atoms can be replaced by fluorine. Furthermore, n in formula (I) is preferably 1.

[0048] Specific examples of sulfonic acid compounds include lithium methanesulfonate, lithium ethanesulfonate, lithium propanesulfonate, sodium methanesulfonate, sodium ethanesulfonate, magnesium methanesulfonate, and lithium fluoromethanesulfonate. Preferably, at least one compound is selected from the group consisting of lithium methanesulfonate, lithium ethanesulfonate, and sodium methanesulfonate, with lithium methanesulfonate being particularly preferred.

[0049] The sulfonic acid compound reduces the reaction resistance in the positive electrode 20. Furthermore, the reduced resistance allows for a deeper charge-discharge depth, improving the initial charge-discharge efficiency. This effect is achieved even in very small amounts of the sulfonic acid compound, but the amount of sulfonic acid compound present on the surface of the secondary particles of the lithium transition metal composite oxide is preferably 0.1% by mass or more, more preferably 0.3% by mass or more, relative to the mass of the lithium transition metal composite oxide. From the viewpoint of cycling characteristics, the amount of sulfonic acid compound present on the surface of the secondary particles of the lithium transition metal composite oxide is preferably 1.0% by mass or less, more preferably 0.8% by mass or less, relative to the mass of the lithium transition metal composite oxide. Therefore, the amount of sulfonic acid compound relative to the mass of the lithium transition metal composite oxide is preferably 0.1% to 1.0% by mass, more preferably 0.3% to 0.8% by mass.

[0050] The presence of sulfonic acid compounds on the surface of secondary particles of lithium transition metal composite oxides can be confirmed by Fourier transform infrared spectroscopy (FT-IR). In the infrared absorption spectra obtained by FT-IR, positive electrode active materials containing lithium methanesulfonate, for example, show an absorption rate of 1238 cm⁻¹. -1 1175cm -1 1065cm -1 785cm -1 There is an absorption peak nearby. 1238cm -1 1175cm -1 1065cm -1 The nearby peak originates from the SO stretching vibration of lithium methanesulfonate. 785 cm⁻¹ -1 The nearby peaks are caused by the CS stretching vibration of lithium methanesulfonate. It should be noted that for positive electrode active materials containing sulfonic acid compounds other than lithium methanesulfonate, their presence can also be confirmed by the absorption peaks originating from the sulfonic acid compounds in the infrared absorption spectrum.

[0051] In addition, the presence of sulfonic acid compounds can also be confirmed by X-ray photoelectron spectroscopy (XPS). In the spectra obtained by XPS, for positive electrode active materials containing lithium methanesulfonate, peaks with binding energies around 165–170 eV and intensities (c / s) of 200–1000 can be observed. It should be noted that the presence of sulfonic acid compounds on the surface of secondary particles containing lithium transition metal composite oxides can also be confirmed by ICP, atomic absorption spectrometry, synchrotron radiation XRD, and time-of-flight secondary ion mass spectrometry (TOF-SIMS).

[0052] The surface of primary particles containing lithium transition metal composite oxides may have a surface modification layer containing at least one element selected from Ca and Sr (hereinafter referred to as "M1"). This effectively suppresses the erosion and degradation of the lithium transition metal composite oxides caused by side reactions with the non-aqueous electrolyte, improving the charge-discharge cycle characteristics of the non-aqueous electrolyte secondary battery 10. Here, the surface of the primary particles includes the surface of the secondary particles; specifically, it refers to the surface of the secondary particles and the interface between the primary particles. The surface modification layer may exist in a dotted manner covering at least a portion of the surface of the primary particles, or it may exist in a manner covering the entire surface of the primary particles.

[0053] The total amount of M1 contained in the surface modification layer is preferably 1 mol% or less, more preferably 0.5 mol% or less, relative to the total molar amount of metal elements other than Li in the lithium-containing transition metal composite oxide. The lower limit of the total amount of M1 is, for example, 0.01 mol%.

[0054] In addition to M1, the surface modification layer may also contain at least one element selected from the group consisting of W, Mo, Ti, Si, Nb, and Zr (hereinafter referred to as "M2"). In this case, the corrosion and degradation of the lithium-containing transition metal composite oxide caused by side reactions with non-aqueous electrolytes can be more effectively suppressed. The total amount of M2 contained in the surface modification layer is 2 mol% or less, more preferably 1 mol% or less, and even more preferably 0.5 mol% or less, relative to the total molar amount of metal elements other than Li in the lithium-containing transition metal composite oxide. The lower limit of the total amount of M2 is, for example, 0.01 mol%.

[0055] The presence of a surface modification layer on the surface of primary particles of lithium transition metal composite oxides, the presence of M1 contained in the surface modification layer, and the presence of M2 contained in the surface modification layer can be confirmed by measuring the cross-section of secondary particles of lithium transition metal composite oxides using TEM-EDX (transmission microscopy-energy dispersive X-ray spectroscopy). Furthermore, the total amount of M1 and M2 can be determined, for example, by inductively coupled plasma (ICP) emission spectroscopy.

[0056] The surface of primary particles containing lithium transition metal composite oxides can also be coated with compounds containing M1 (hereinafter referred to as "M1 compounds") and compounds containing M2 (hereinafter referred to as "M2 compounds"). Examples of M1 compounds include oxides, hydroxides, carbonates, etc. Examples of M2 compounds include oxides, hydroxides, carbonates, sulfates, etc.

[0057] The surface of primary particles containing lithium transition metal composite oxides can also be fixed with a general formula M1. α M2 βO γ (where 1≤α≤2, 1≤β≤5, 4≤γ≤9, M1 is at least one element selected from Ca and Sr, and M2 is at least one element selected from W, Mo, Ti, Si, Nb and Zr) represents a compound (hereinafter referred to as "M1"). α M2 β O γ (Compounds). It should be noted that compounds M1, M2, and M1 can coexist on the surface of primary particles containing lithium transition metal composite oxides. α M2 β O γ Compounds.

[0058] M1 α M2 β O γ The presence of the compound can be confirmed using synchrotron X-ray diffraction. M1 α M2 β O γ The compound can be dispersed on the surface of primary and secondary particles of lithium transition metal composite oxides, or it can exist in a layered manner to extensively cover the surface of primary and secondary particles. That is, M1 exists both inside and on the surface of secondary particles. α M2 β O γ The compounds are widely present on the surface of the primary particles. Secondary particles containing lithium transition metal complex oxides, for example, are formed by the aggregation of five or more primary particles; the surface area of ​​the primary particles inside is larger than the surface area of ​​the secondary particles. For example, compared to the surface of the secondary particles, the interior contains more M1. α M2 β O γ Compounds.

[0059] As M1 α M2 β O γ Specific examples of compounds include CaWO4, CaMoO3, CaMoO4, CaTiO3, Ca2TiO4, CaSiO3, Ca2SiO4, CaNbO3, CaNb2O6, CaZrO3, CaZr4O9, SrWO4, SrMoO3, SrMoO4, SrTiO3, Sr2TiO4, SrSiO3, Sr2SiO4, SrNbO3, SrNb2O6, SrZrO3, and SrZr4O9.

[0060] Furthermore, nonmetallic compounds may also be present on the surface of primary particles containing lithium transition metal complex oxides. These nonmetallic compounds may, for example, contain one or more nonmetallic elements selected from the group consisting of P and B. Li can be cited as an example of a P-containing compound.3-x H x PO4 (0≤x≤3). Examples of compounds containing B include H3BO3, Li3BO3, and Li2B4O7.

[0061] In addition to the positive electrode active material described in this embodiment, the positive electrode additive layer may also contain other positive electrode active materials. Examples of other positive electrode active materials include lithium-containing transition metal composite oxides with a Ni content of 0 mol% or more and 75 mol% or less.

[0062] As an example of an implementation method, the positive electrode active material can be manufactured by the following method. It should be noted that the manufacturing method described herein is an example, and the manufacturing method of the positive electrode active material is not limited to this method.

[0063] The manufacturing process of the positive electrode active material includes: a synthesis process in which a metal oxide is mixed with a Li compound to obtain a mixture, and the mixture is calcined to obtain a lithium-containing transition metal composite oxide; a washing process in which the calcined material is washed with water and dehydrated to obtain a cake-shaped composition; a drying process in which the cake-shaped composition is dried to obtain a powder-shaped composition; and an addition process in which at least one of a sulfonic acid compound and a sulfonic acid solution is added to the cake-shaped composition or the powder-shaped composition.

[0064] In the synthesis process, for example, a metal oxide containing more than 75 mol% and less than 95 mol% Ni, 0 mol% to 15 mol% Co, 0 mol% to 25 mol% Mn and 0 mol% to 10 mol% M (M is at least one element selected from W, Mg, Mo, Nb, Ti, Si, Al and Zr) is mixed with a Li compound to obtain a mixture.

[0065] Metal oxides can be obtained, for example, by stirring a solution containing Ni and any metal element (Co, Mn, M, etc.) while adding an alkaline solution such as sodium hydroxide dropwise to adjust the pH to the alkaline side (e.g., 8.5–12.5), thereby causing a composite hydroxide containing Ni and any metal element to precipitate (co-precipitate). The composite hydroxide is then subjected to heat treatment. There are no particular limitations on the heat treatment temperature, for example, a range of 250°C to 600°C.

[0066] Examples of Li compounds include Li₂CO₃, LiOH, Li₂O₂, Li₂O, LiNO₃, LiNO₂, Li₂SO₄, LiOH·H₂O, LiH, and LiF. From the viewpoint of easily adjusting the above parameters to the ranges specified above, the mixing ratio of the metal oxide and the Li compound is preferably set to a ratio in which the total amount of metal elements in the metal oxide and the molar ratio of Li are in the range of 1:0.80 to 1:1.20, and more preferably in the range of 1:1.00 to 1:1.10.

[0067] Next, the synthesis process includes a calcination step of calcining the obtained mixture. The calcination step is, for example, a multi-stage calcination step, which includes at least: a first calcination step, calcining at 300°C to 680°C under an oxygen flow; and a second calcination step, calcining the product obtained in the first calcination step at a temperature exceeding 680°C under an oxygen flow. In the first calcination step, the temperature is increased to a first set temperature below 680°C at a first heating rate of 0.2°C / min to 4.5°C / min. In the second calcination step, the temperature is increased to a second set temperature below 900°C at a first heating rate of 0.5°C / min to 3.5°C / min. It should be noted that multiple heating rates can be set for each temperature range, as long as they are within the aforementioned range.

[0068] The holding time of the first set temperature in the first roasting step is preferably 5 hours or less, more preferably 3 hours or less. The holding time of the first set temperature refers to the time during which the first set temperature is maintained after it has been reached; the holding time can be zero. The holding time of the second set temperature in the second roasting step is preferably 1 hour to 10 hours, more preferably 1 hour to 5 hours. The holding time of the second set temperature refers to the time during which the second set temperature is maintained after it has been reached. The roasting of the mixture is, for example, carried out in an oxygen flow with an oxygen concentration of 60% or higher, with the oxygen flow rate set to 10 cm³ / s. 3 The roasting furnace operates at a rate of 0.2 mL / min to 4 mL / min and at a rate of 0.3 L / min or higher per 1 kg of mixture.

[0069] In the cleaning process, the lithium-containing transition metal composite oxide obtained in the synthesis process is washed with water and dehydrated to obtain a cake-like composition. Washing and dehydration can be carried out using known methods and conditions. The washing and dehydration should be performed within a range that prevents lithium from dissolving from the lithium-containing transition metal composite oxide and thus degrading battery characteristics.

[0070] In the drying process, the cake-like composition obtained in the cleaning process is dried to obtain a powder-like composition. The drying process can be carried out under a vacuum atmosphere. The drying conditions are, for example, 150°C to 400°C for 0.5 hours to 15 hours.

[0071] In the addition step, at least one of a sulfonic acid compound and a sulfonic acid solution is added to the cake-like composition obtained in the cleaning step or the powder-like composition obtained in the drying step. This allows the sulfonic acid compound to adhere to the surface of the lithium-containing transition metal complex oxide. Preferably, at least one of a sulfonic acid compound and a sulfonic acid solution is added to the cake-like composition. The added sulfonic acid compound can optionally be in powder or solution form. The sulfonic acid solution is, for example, a methanesulfonic acid solution obtained by dissolving methanesulfonic acid in water. Since a Li compound remains in the cake-like composition, and this residual Li compound dissolves in the water contained in the cake-like composition, a Li-containing sulfonic acid compound is formed even with the addition of the sulfonic acid solution. From the viewpoint of more easily obtaining the effects of this application, the Li compound or Li compound solution can be added together with the sulfonic acid solution to the cake-like composition or the powder-like composition, or a mixed solution pre-mixed with the Li compound or Li compound solution can be added to the cake-like composition or the powder-like composition. The Li compound is, for example, LiOH, and the Li compound solution is, for example, a LiOH solution obtained by dissolving LiOH in water. The amounts of Li compound and sulfonic acid solution added to the cake-like composition preferably satisfy a molar ratio of 0 ≤ Li compound / sulfonic acid ≤ 1.3. The amount of sulfonic acid compound or sulfonic acid added relative to the mass of the lithium-containing transition metal composite oxide is preferably 0.1% to 1% by mass, more preferably 0.3% to 0.8% by mass. The concentrations of the sulfonic acid solution and the sulfonic acid compound solution are, for example, 0.5% to 40% by mass. It should be noted that the addition process can be carried out at any stage, during, after, or during the cleaning process, or after the drying process, and the timing can be appropriately varied.

[0072] Metal compounds containing one or more metallic elements selected from the group consisting of Sr, Ca, W, Mo, Ti, Si, Nb, and Zr can be added at any stage during the synthesis process, after the synthesis process, during the cleaning process, after the cleaning process, during the drying process, after the drying process, or during the addition process, thereby adhering to the surface of lithium-containing transition metal composite oxides. Examples of Sr raw materials include Sr(OH)₂, Sr(OH)₂·8H₂O, SrO, SrCO₃, SrSO₄, and Sr(NO₃). 2、 SrCl2, SrAlO4, etc. Examples of raw materials for Ca include Ca(OH)2, CaO, CaCO3, CaSO4, and Ca(NO3). 2、CaCl2, CaAlO4, etc. As the W raw material, tungsten oxide (WO3), lithium tungstate (Li2WO4, Li4WO5, Li6W2O9), etc. can be cited. As the Mo raw material, MoO3, Li2MoO4 can be cited. As the Ti raw material, TiO2, Ti(OH)4 can be cited. As the Si raw material, SiO2, SiO can be cited. As the Nb raw material, Nb2O5, Nb2O5·nH2O, etc. can be cited. As the Zr raw material, Zr(OH)4, ZrO2, Zr(CO3)2, Zr(SO4)2·4H2O, etc. can be cited. It should be noted that these raw materials can be used by appropriately adjusting the moisture content, particle size, etc. of the hydrate through pulverization and / or drying.

[0073] [Negative electrode]

[0074] The negative electrode 21 has a negative electrode core and a negative electrode mixture layer formed on the surface of the negative electrode core. The negative electrode mixture layer is preferably formed on both sides of the negative electrode core. The negative electrode core can use foils of metals such as copper and copper alloys that are stable within the potential range of the negative electrode 21, thin films with this metal disposed on the surface layer, etc. The negative electrode mixture layer can contain a negative electrode active material and a binder. The thickness of the negative electrode mixture layer is, for example, 10 μm to 150 μm on one side of the negative electrode core. The negative electrode 21 can be manufactured, for example, by coating a negative electrode slurry containing a negative electrode active material, a binder, etc. on the surface of the negative electrode core, drying the coating film, and then performing rolling to form a negative electrode mixture layer on both sides of the negative electrode core.

[0075] As the negative electrode active material contained in the negative electrode mixture layer, there is no particular limitation as long as it can reversibly absorb and release lithium ions, and generally carbon materials such as graphite can be used. The graphite can be any of natural graphite such as flake graphite, massive graphite, earthy graphite, massive artificial graphite, graphitized mesophase carbon microspheres, etc. artificial graphite. In addition, as the negative electrode active material, metals alloyed with Li such as Si and Sn, metal compounds containing Si, Sn, etc., lithium titanium composite oxides, etc. can be used. In addition, materials with a carbon coating film provided thereon can also be used. For example, a Si-containing compound represented by SiO x (0.5 ≤ x ≤ 1.6), or a Si-containing compound in which Si fine particles are dispersed in a lithium silicate phase represented by Li 2y SiO (2+y) (0 < y < 2) can be used in combination with graphite.

[0076] Examples of binders included in the negative electrode binder layer include styrene-butadiene rubber (SBR), nitrile rubber (NBR), carboxymethyl cellulose (CMC) or its salts, polyacrylic acid (PAA) or its salts (PAA-Na, PAA-K, etc., and some neutralized salts), polyvinyl alcohol (PVA), etc. These can be used individually or in combination of two or more.

[0077] [Separator]

[0078] The separator 22 can be, for example, a porous sheet with ion permeability and insulation. Specific examples of porous sheets include microporous films, woven fabrics, and nonwoven fabrics. The preferred materials for the separator are polyolefins such as polyethylene and polypropylene, and cellulose. The separator 22 can be a single-layer structure or a multilayer structure. Furthermore, a resin layer with high heat resistance, such as aramid resin, or a filler layer containing inorganic compounds can be provided on the surface of the separator 22.

[0079] [Non-aqueous electrolytes]

[0080] Non-aqueous electrolytes possess ionic conductivity (e.g., lithium-ion conductivity). Non-aqueous electrolytes can be liquid electrolytes (electrolytes) or solid electrolytes.

[0081] Liquid electrolytes (electrolytes) may include, for example, a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent. Non-aqueous solvents may include, for example, 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 derivatives formed by substituting at least a portion of the hydrogen atoms of these solvents with halogen atoms such as fluorine. Examples of halogen-substituted derivatives include fluorocyclic carbonates such as fluoroethylene carbonate (FEC), fluorochain carbonates, and fluorochain carboxylic acid esters such as methyl fluoropropionate (FMP).

[0082] Examples of the aforementioned esters include cyclic carbonates such as ethylene carbonate (EC), propylene carbonate (PC), and butyl carbonate; chain carbonates 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 chain carboxylic acid esters such as methyl acetate, ethyl acetate, propyl acetate, methyl propionate (MP), and ethyl propionate (EP).

[0083] Examples of the aforementioned ethers include 1,3-dioxolane, 4-methyl-1,3-dioxolane, tetrahydrofuran, 2-methyltetrahydrofuran, propylene oxide, 1,2-epoxybutane, 1,3-dioxane, 1,4-dioxane, 1,3,5-trioxane, furan, 2-methylfuran, 1,8-eucalyptol, crown ethers, cyclic ethers, 1,2-dimethoxyethane, diethyl ether, dipropyl ether, diisopropyl ether, dibutyl ether, and dihexyl ether. Ethers, including ethyl vinyl ether, butyl vinyl ether, methyl phenyl ether, ethyl phenyl ether, butyl phenyl ether, pentyl phenyl 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, tetraethylene glycol dimethyl ether, and other chain ethers.

[0084] The preferred electrolyte salt is a lithium salt. Examples of lithium salts include LiClO4, LiBF4, LiPF6, LiAlCl4, LiSbF6, LiSCN, LiCF3SO3, LiCF3CO2, LiAsF6, and LiB2. 10 Cl 10 Examples of lithium salts include lower aliphatic carboxylic acids such as lithium Cl, LiBr, LiI, phosphates, borates, and imide salts. Examples of phosphates include lithium difluorophosphate (LiPO₂F₂), lithium difluorobis(oxalate)phosphate (LiDFBOP), and lithium tetrafluoro(oxalate)phosphate. Examples of borates include lithium bis(oxalate)borate (LiBOB) and lithium difluoro(oxalate)borate (LiDFOB). Examples of imide salts include lithium difluorosulfonylimide (LiN(FSO₂)₂), lithium bis(trifluoromethanesulfonylimide) (LiN(CF₃SO₂)₂), lithium trifluoromethanesulfonate nonafluorobutanesulfonylimide (LiN(CF₃SO₂)(C₄F₉SO₂)), and lithium bis(pentafluoroethanesulfonylimide) (LiN(C₂F₅SO₂)₂). Among these, LiPF₆ is preferred from the perspectives of ionic conductivity and electrochemical stability. The concentration of lithium salt can be less than 4 moles per 1L of non-aqueous solvent, less than 3 moles, preferably less than 1.8 moles, and more preferably 0.8 to 1.8 moles.

[0085] Non-aqueous electrolytes may contain additives. Examples of additives include unsaturated carbonates, acid anhydrides, phenolic compounds, benzene compounds, nitrile compounds, isocyanate compounds, sulcolone compounds, sulfuric acid compounds, borate ester compounds, phosphate ester compounds, and phosphite ester compounds.

[0086] Examples of unsaturated cyclic carbonates 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, vinyl ethylene carbonate, and divinyl ethylene carbonate. One type of unsaturated cyclic carbonate can be used alone, or two or more can be used in combination. Some hydrogen atoms in the unsaturated cyclic carbonate can be replaced by fluorine atoms. The anhydride can be an anhydride formed by the intermolecular condensation of multiple carboxylic acid molecules, preferably an anhydride of a polycarboxylic acid. Examples of anhydrides of polycarboxylic acids include succinic anhydride, maleic anhydride, and phthalic anhydride.

[0087] Examples of phenolic compounds include phenol and hydroxytoluene. Examples of benzene compounds include fluorobenzene, hexafluorobenzene, and cyclohexylbenzene (CHB).

[0088] Examples of nitrile compounds include adiponitrile, heptanonitrile, propionitrile, and succinic anionyl. Examples of isocyanate compounds include methyl isocyanate (MIC), diphenylmethane diisocyanate (MDI), hexamethylene diisocyanate (HDI), toluene diisocyanate (TDI), isophorone diisocyanate (IPDI), and cyclohexane dimethyl diisocyanate (BIMCH). Examples of sulcolone compounds include propane sulcolone and propene sulcolone. Examples of sulfuric acid compounds include ethylene sulfate, ethylene sulfite, dimethyl sulfate, and lithium fluorosulfate. Examples of borate compounds include trimethyl borate and tris(trimethylsilyl)borate. Examples of phosphate compounds include trimethyl phosphate and tris(trimethylsilyl) phosphate. Examples of phosphite compounds include trimethyl phosphite and tris(trimethylsilyl) phosphite.

[0089] As a solid electrolyte, examples include solid or gel-like polymer electrolytes and inorganic solid electrolytes. As an inorganic solid electrolyte, materials known in all-solid-state lithium-ion secondary batteries (e.g., oxide-based solid electrolytes, sulfide-based solid electrolytes, halogen-based solid electrolytes, etc.) can be used. Polymer electrolytes, for example, contain lithium salts and a matrix polymer, or contain a non-aqueous solvent, a lithium salt, and a matrix polymer. As a matrix polymer, for example, a polymer material that gels by absorbing a non-aqueous solvent is used. Examples of polymer materials include fluoropolymers, acrylic resins, and polyether resins.

[0090] Example

[0091] The present disclosure is further illustrated below by way of examples and comparative examples, but the present disclosure is not limited to the following examples.

[0092] <Example 1>

[0093] [Preparation of positive electrode active material]

[0094] The [Ni] obtained by coprecipitation method 0.90 Co 0.05 Mn 0.05 The complex hydroxide represented by [(OH)₂] was calcined at 500°C for 8 hours to obtain a metal oxide containing Ni, Co, and Mn. Next, LiOH and the above metal oxide were mixed in a molar ratio of Li to the total amount of Ni, Co, and Mn of 1.03:1 to obtain a mixture. This mixture was then subjected to an oxygen gas flow of 95% oxygen concentration (per 10 cm³). 2 The mixture was heated from room temperature to 650°C at a flow rate of 2 mL / min and 5 L / min per 1 kg of mixture, and then heated from 650°C to 780°C at a flow rate of 0.5°C / min, and held for 4 hours to obtain a lithium-containing transition metal composite oxide (synthesis step). Water was added to the lithium-containing transition metal composite oxide at a slurry concentration of 1500 g / L, stirred for 15 minutes, and filtered to obtain a cake-like composition (washing step). Powdered lithium methanesulfonate was added to the cake-like composition (addition step). The amount of lithium methanesulfonate added was 0.1% by mass relative to the total mass of the lithium-containing transition metal composite oxide. After the addition step, a drying step was performed under vacuum at 180°C for 2 hours to obtain the positive electrode active material of Example 1. It should be noted that the presence of lithium methanesulfonate on the surface of the positive electrode active material was confirmed by Fourier transform infrared spectroscopy (FT-IR).

[0095] [The production of the positive electrode]

[0096] 95 parts by weight of the above-mentioned positive electrode active material, 3 parts by weight of acetylene black (AB), and 2 parts by weight of polyvinylidene fluoride (PVDF) were mixed, and N-methyl-2-pyrrolidone (NMP) was added in appropriate amount to prepare a positive electrode slurry. Next, the positive electrode slurry was coated onto both sides of a positive electrode core made of aluminum foil. After the coating was dried, it was calendered using calendering rollers and cut into the specified electrode size to manufacture the positive electrode. It should be noted that an exposed portion of the positive electrode core surface is provided in a part of the positive electrode.

[0097] [Making the negative electrode]

[0098] A negative electrode slurry was prepared by mixing 98 parts by weight of artificial graphite, 1 part by weight of sodium carboxymethyl cellulose (CMC-Na), and 1 part by weight of styrene-butadiene rubber (SBR), with an appropriate amount of water added. Next, this negative electrode slurry was coated onto both sides of a negative electrode core made of copper foil. After the coating was dried, it was calendered using calendering rollers and cut into specified electrode sizes to fabricate the negative electrode. It should be noted that an exposed portion of the negative electrode core surface is provided on a portion of the negative electrode.

[0099] [Preparation of non-aqueous electrolytes]

[0100] Ethyl carbonate (EC), methyl ethyl carbonate (MEC), and dimethyl carbonate (DMC) were mixed in a volume ratio of 3:3:4. Lithium hexafluorophosphate (LiPF6) was dissolved in this mixed solvent to a concentration of 1.2 mol / L to prepare a non-aqueous electrolyte.

[0101] [Fabrication of the Experimental Battery Cell]

[0102] A positive electrode lead is installed on the exposed portion of the positive electrode, and a negative electrode lead is installed on the exposed portion of the negative electrode. The positive and negative electrodes are wound into a spiral shape with a polyolefin separator in between, and then pressed radially to form a flat, wound electrode body. This electrode body is housed in a shell made of aluminum laminate, and after injecting the aforementioned non-aqueous electrolyte, the opening of the shell is sealed to obtain the experimental battery cell.

[0103] [Evaluation of initial charge / discharge efficiency]

[0104] For the test battery cell, at a temperature of 25°C, it was charged at a constant current of 0.2 It until the battery voltage reached 4.3V, and then charged at a constant voltage of 4.3V until the current reached 0.01 It. After 1 hour, it was discharged at a constant current of 0.2 It until the battery voltage reached 2.5V. The charging capacity and discharging capacity at this time were measured, and the initial charge-discharge efficiency of the test battery cell was calculated using the following formula. It should be noted that in the test battery cell of Example 1, the energy from the outside... Figure 2 The test battery cell was pressed against both sides of the stacking direction α, and an 8.00 × 10⁻⁶ pressure was applied to the electrode body. -2 The above evaluation was conducted based on a pressure of MPa (structural pressure).

[0105] Initial charge / discharge efficiency = Discharge capacity / Charge capacity

[0106] [Evaluation of Cyclic Characteristics]

[0107] For the test battery cell, at a temperature of 25°C, it was charged to 4.3V with a constant current of 0.2It, and then charged to 0.02It with a constant voltage of 4.3V. Then, it was discharged to 2.5V with a constant current of 0.2It. This charge-discharge cycle was considered one cycle, and it was repeated 100 times. The capacity retention rate was calculated using the following formula. It should be noted that in the test battery cell of Example 1, the capacity retention rate was... Figure 2 The test battery cell was pressed against both sides of the stacking direction α, and an 8.00 × 10⁻⁶ pressure was applied to the electrode body. -2 The above evaluation was conducted based on a structural pressure of MPa.

[0108] Capacity retention rate = (Discharge capacity at 100th cycle / Discharge capacity at 1st cycle) × 100

[0109] <Example 2>

[0110] In the process of adding positive electrode active material, the amount of lithium methanesulfonate added was set to 0.3% by mass relative to the total mass of lithium transition metal composite oxide. Otherwise, the test battery cells were prepared and evaluated in the same manner as in Example 1.

[0111] <Example 3>

[0112] In the process of adding positive electrode active material, the amount of lithium methanesulfonate added was set to 0.5% by mass relative to the total mass of lithium transition metal composite oxide. Otherwise, the test battery cells were prepared and evaluated in the same manner as in Example 1.

[0113] <Example 4>

[0114] In the process of adding positive electrode active material, the amount of lithium methanesulfonate added was set to 0.8% by mass relative to the total mass of lithium transition metal composite oxide. Otherwise, the test battery cells were prepared and evaluated in the same manner as in Example 1.

[0115] <Example 5>

[0116] In the process of adding positive electrode active material, the amount of lithium methanesulfonate added was set to 1% by mass relative to the total mass of lithium transition metal composite oxide. Otherwise, the test battery cell was prepared and evaluated in the same manner as in Example 1.

[0117] <Example 6>

[0118] In the process of adding positive electrode active material, the amount of lithium methanesulfonate added is set to 0.5% by mass relative to the total mass of lithium-containing transition metal composite oxides. For the test battery cell, from Figure 2 Pressing on both sides of the stacking direction α, applying 1.30 × 10⁻⁶ to the electrode body. -1The structural pressure of MPa was used to evaluate the initial charge-discharge efficiency and cycle characteristics. Otherwise, test battery cells were fabricated and evaluated in the same manner as in Example 1.

[0119] <Example 7>

[0120] In the process of adding positive electrode active material, the amount of lithium methanesulfonate added is set to 0.5% by mass relative to the total mass of lithium-containing transition metal composite oxides. For the test battery cell, from Figure 2 Pressing on both sides of the stacking direction α, applying 5.70 × 10⁻⁶ to the electrode body. -1 The structural pressure of MPa was used to evaluate the initial charge-discharge efficiency and cycle characteristics. Otherwise, test battery cells were fabricated and evaluated in the same manner as in Example 1.

[0121] <Example 8>

[0122] In the process of adding positive electrode active material, the amount of lithium methanesulfonate added is set to 0.5% by mass relative to the total mass of lithium-containing transition metal composite oxides. For the test battery cell, from Figure 2 Pressing the two sides of the stacking direction α, a structural pressure of 1.30 MPa is applied to the electrode body to evaluate the initial charge-discharge efficiency and cycle characteristics. Otherwise, test battery cells are fabricated and evaluated in the same manner as in Example 1.

[0123] <Example 9>

[0124] In the process of adding the positive electrode active material, a lithium methanesulfonate solution, prepared by dissolving lithium methanesulfonate in pure water, was added instead of powdered lithium methanesulfonate. The amount of lithium methanesulfonate added was set to 0.5% by mass relative to the total mass of the lithium transition metal composite oxide. Otherwise, the test battery cell was prepared and evaluated in the same manner as in Example 1. It should be noted that the concentration of the added lithium methanesulfonate solution was 10% by mass, and the lithium methanesulfonate solution was added in the manner described above.

[0125] <Example 10>

[0126] In the process of adding the positive electrode active material, a methanesulfonic acid solution (made by dissolving methanesulfonic acid in pure water) was added instead of powdered lithium methanesulfonate. The amount of methanesulfonic acid added was set to 0.5% by mass relative to the total mass of the lithium transition metal composite oxide. Otherwise, the test battery cell was fabricated and evaluated in the same manner as in Example 1. It should be noted that the concentration of the added methanesulfonic acid solution was 10% by mass, and the amount of lithium methanesulfonate added was the same as described above. The presence of lithium methanesulfonate on the surface of the positive electrode active material was confirmed by Fourier transform infrared spectroscopy (FT-IR).

[0127] <Example 11>

[0128] In the process of adding the positive electrode active material, a solution containing methanesulfonic acid and LiOH (hereinafter, methanesulfonic acid + LiOH solution) obtained by dissolving methanesulfonic acid and LiOH in pure water at a molar ratio of 1:0.5 was added instead of powdered lithium methanesulfonate. The amount of lithium methanesulfonate added was set to 0.5% by mass relative to the total mass of the lithium transition metal composite oxide. Otherwise, the test battery cell was prepared and evaluated in the same manner as in Example 1. It should be noted that the concentration of the added methanesulfonic acid + LiOH solution was 10% by mass, and the amount of lithium methanesulfonate added was as described above.

[0129] <Example 12>

[0130] In the process of adding the positive electrode active material, a methanesulfonic acid + LiOH solution with a molar ratio of methanesulfonic acid to LiOH of 1:1 was added instead of powdered lithium methanesulfonate. The amount of lithium methanesulfonate added was set to 0.5% by mass relative to the total mass of the lithium transition metal composite oxide. Otherwise, the test battery cell was fabricated and evaluated in the same manner as in Example 1. It should be noted that the concentration of the added methanesulfonic acid + LiOH solution was 10% by mass, and the amount of lithium methanesulfonate added was the same as described above.

[0131] <Example 13>

[0132] In the process of adding positive electrode active material, powdered sodium methanesulfonate was added instead of powdered lithium methanesulfonate. The amount of sodium methanesulfonate added was set to 0.5% by mass relative to the total mass of lithium transition metal composite oxide. Otherwise, the test battery cell was prepared and evaluated in the same manner as in Example 1.

[0133] <Example 14>

[0134] In the process of adding positive electrode active material, powdered lithium ethanesulfonate was added instead of powdered lithium methanesulfonate. The amount of lithium ethanesulfonate added was set to 0.5% by mass relative to the total mass of the lithium transition metal composite oxide. Otherwise, the test battery cell was prepared and evaluated in the same manner as in Example 1.

[0135] <Comparative Example 1>

[0136] In the preparation of the positive electrode active material, no addition process was performed. The initial charge-discharge efficiency and cycle characteristics were evaluated without applying structural stress to the test battery cell. Otherwise, the test battery cell was prepared and evaluated in the same manner as in Example 1.

[0137] <Comparative Example 2>

[0138] In the preparation of the positive electrode active material, no addition process was performed. Otherwise, the test battery cells were prepared and evaluated in the same manner as in Example 1.

[0139] <Comparative Example 3>

[0140] In the process of adding positive electrode active material, the amount of lithium methanesulfonate added was set to 0.5% of the total mass of lithium transition metal composite oxide. The initial charge-discharge efficiency and cycle characteristics were evaluated without applying structural stress to the test battery cell. Otherwise, the test battery cell was prepared and evaluated in the same manner as in Example 1.

[0141] <Comparative Example 4>

[0142] In the process of adding positive electrode active material, the amount of lithium methanesulfonate added is set to 0.5% by mass relative to the total mass of lithium-containing transition metal composite oxides. For the test battery cell, from Figure 2 Pressing down on both sides of the stacking direction α, applying a 4.00 × 10⁻⁶ pressure to the electrode body. -2 The structural pressure of MPa was used to evaluate the initial charge-discharge efficiency and cycle characteristics. Otherwise, test battery cells were fabricated and evaluated in the same manner as in Example 1.

[0143] <Comparative Example 5>

[0144] In the process of adding positive electrode active material, 10% by mass of lithium succinate solution was added to replace powdered lithium methanesulfonate. The amount of lithium succinate added was set to 0.5% by mass relative to the total mass of lithium transition metal composite oxide. Otherwise, the test battery cell was prepared and evaluated in the same manner as in Example 1.

[0145] <Comparative Example 6>

[0146] In the process of adding positive electrode active material, 10% by mass of lithium oxalate solution was added to replace powdered lithium methanesulfonate. The amount of lithium oxalate added was set to 0.5% by mass relative to the total mass of lithium transition metal composite oxide. Otherwise, the test battery cells were prepared and evaluated in the same manner as in Example 1.

[0147] The initial charge-discharge efficiency and capacity retention of the test battery cells of Examples 1-14 and Comparative Examples 1-6 are shown in Table 1. Table 1 also shows the composition of the lithium transition metal composite oxide, the added compounds, the method of addition, the amount added, and the structural stress from external sources. The initial charge-discharge efficiency and capacity retention of the test battery cells of Examples 1-14 and Comparative Examples 1-6 shown in Table 1 are relative values ​​with the initial charge-discharge efficiency and capacity retention of the test battery cell of Comparative Example 1 set to 100. A higher initial charge-discharge efficiency value indicates better initial charge-discharge efficiency, and a higher capacity retention value indicates better cycle characteristics.

[0148] [Table 1]

[0149]

[0150] As shown in Table 1, the test battery cells of the embodiments showed improved initial charge-discharge efficiency and capacity retention compared to the test battery cells of the comparative examples. Additionally, an 8.00 × 10⁻⁶ ohmmeter was applied to the electrode body. -2 The test cell of Comparative Example 2, which had a structural pressure of over MPa and no sulfonic acid compounds on the surface of the secondary particles, showed a slight improvement in capacity retention compared to the test cell of Comparative Example 1, but no improvement in initial charge-discharge efficiency.

[0151] Furthermore, while the sulfonic acid compound was present on the surface, no 8.00 × 10⁻⁶ ppm was applied to the electrode body. -2 Compared to the test battery cell of Comparative Example 1, the test battery cells of Comparative Examples 3 and 4, which have a structural pressure of over MPa, exhibited a deterioration in capacity retention. This is presumably due to the presence of sulfonic acid compounds on the surface of the secondary particles, leading to a larger volume change in the lattice of the positive electrode active material, resulting in particle breakage and side reactions between the broken particles and the non-aqueous electrolyte. On the other hand, when comparing the test battery cells of the Examples with the test battery cell of Comparative Example 2, the test battery cells of the Examples showed improved capacity retention in addition to improved initial charge / discharge efficiency. That is, by applying a structural pressure of 8.00 × 10 MPa to the electrode body... -2 Structural pressures exceeding 8.00 MPa cause sulfonic acid compounds to be present on the surface of secondary particles, thereby improving capacity retention. This is presumably because, in addition to inhibiting the breakage of the positive electrode active material particles due to external structural pressure, the sulfonic acid compounds coat the surface of the positive electrode active material particles, thus suppressing side reactions between the particles and the non-aqueous electrolyte. In other words, when the external structural pressure is less than 8.00 × 10⁻⁶ MPa, the capacity retention is improved. -2In such cases, the positive electrode active material particles are prone to breakage, making it difficult to obtain the effect of covering the surface of the positive electrode active material particles with sulfonic acid compounds. Based on these results, it can be said that by having sulfonic acid compounds present on the surface of secondary particles and applying 8.00 × 10⁻⁶ ppm to the electrode body from the outside, -2 Pressures above MPa enable the provision of non-aqueous electrolyte secondary batteries that offer improved initial charge / discharge efficiency while exhibiting excellent cycle characteristics.

[0152] <Example 15>

[0153] In the synthesis process of the positive electrode active material, the composition of the composite hydroxide is changed to [Ni 0.80 Co 0.10 Mn 0.10 In the addition process, the amount of lithium methanesulfonate added was set to 0.5% by mass relative to the total mass of the lithium transition metal composite oxide. Otherwise, the test battery cells were prepared and evaluated in the same manner as in Example 1.

[0154] <Example 16>

[0155] In the synthesis process of the positive electrode active material, the composition of the composite hydroxide is changed to [Ni 0.90 Mn 0.05 Al 0.05 In the addition process, the amount of lithium methanesulfonate added was set to 0.5% by mass relative to the total mass of the lithium transition metal composite oxide. Otherwise, the test battery cells were prepared and evaluated in the same manner as in Example 1.

[0156] <Example 17>

[0157] In the synthesis process of the positive electrode active material, the composition of the composite hydroxide is changed to [Ni 0.82 Co 0.02 Mn 0.10 Al 0.06 In the addition process, the amount of lithium methanesulfonate added was set to 0.5% by mass relative to the total mass of the lithium transition metal composite oxide. Otherwise, the test battery cells were prepared and evaluated in the same manner as in Example 1.

[0158] <Comparative Example 7>

[0159] In the synthesis process of the positive electrode active material, the composition of the composite hydroxide is changed to [Ni 0.80 Co 0.10 Mn 0.10 (OH)2 was not added. Otherwise, the test battery cells were made and evaluated in the same manner as in Example 1.

[0160] <Comparative Example 8>

[0161] In the synthesis process of the positive electrode active material, the composition of the composite hydroxide is changed to [Ni 0.90 Co 0.05 Mn 0.05 (OH)2 was not added. Otherwise, the test battery cells were made and evaluated in the same manner as in Example 1.

[0162] <Comparative Example 9>

[0163] In the synthesis process of the positive electrode active material, the composition of the composite hydroxide is changed to [Ni 0.82 Co 0.02 Mn 0.10 Al 0.06 (OH)2 was not added. Otherwise, the test battery cells were made and evaluated in the same manner as in Example 1.

[0164] The initial charge-discharge efficiency and capacity retention of the test battery cells of Examples 15-17 and Comparative Examples 7-9 are shown separately in Tables 2-4. Tables 2-4 also show the composition of the lithium transition metal composite oxide, the added compounds, the method of addition, the amount added, and the structural stress from external sources. The initial charge-discharge efficiency and capacity retention of the test battery cell of Example 15 shown in Table 2 are values ​​relative to the initial charge-discharge efficiency and capacity retention of the test battery cell of Comparative Example 7, which are set to 100. Similarly, the initial charge-discharge efficiency and capacity retention of the test battery cell of Example 16 shown in Table 3 are values ​​relative to the initial charge-discharge efficiency and capacity retention of the test battery cell of Comparative Example 8, which are set to 100. Furthermore, the initial charge-discharge efficiency and capacity retention of the test battery cell of Example 17 shown in Table 4 are values ​​relative to the initial charge-discharge efficiency and capacity retention of the test battery cell of Comparative Example 9, which are set to 100. Similar to Table 1, a higher initial charge / discharge efficiency value indicates better initial charge / discharge efficiency, and a higher capacity retention value indicates better cycle characteristics.

[0165] [Table 2]

[0166]

[0167] [Table 3]

[0168]

[0169] [Table 4]

[0170]

[0171] As shown in Tables 2-4, the test battery cells of the embodiments showed improved initial charge-discharge efficiency and capacity retention compared to the test battery cells of the comparative examples. That is, the effects of this disclosure are achieved even when the composition of the metal oxide is changed.

[0172] <Example 18>

[0173] In the preparation of the positive electrode active material, the test battery cell was prepared in the same manner as in Example 1, except for the following changes.

[0174] (1) In the synthesis process, the composition of the composite hydroxide is made as [Ni 0.90 Co 0.05 Mn 0.05 After obtaining a metal oxide by reacting [Ca(OH)2], Ca(OH)2 and WO3 are added to the metal oxide in a molar ratio of Ca to the total amount of Ni, Co, and Mn of 0.25 mol% and W to the total amount of Ni, Co, and Mn of 0.5 mol%. Then, lithium hydroxide monohydrate (LiOH·H2O) is mixed in a molar ratio of Li to the total amount of Ni, Co, Mn, Ca, and W of 1.03:1 to obtain a mixture.

[0175] (2) In the addition process, the amount of lithium methanesulfonate added is set to 0.5% of the total mass of the lithium transition metal composite oxide.

[0176] For the prepared positive electrode active material, TEM-EDX observation of the interface between the primary particles and the secondary particles within the secondary particles confirmed the presence of a surface modification layer containing Ca and W. Furthermore, synchrotron X-ray diffraction analysis identified compounds present in the positive electrode active material, confirming the presence of CaWO4.

[0177] <Comparative Example 10>

[0178] In the preparation of the positive electrode active material, no addition process was performed. Otherwise, the test battery cells were prepared and evaluated in the same manner as in Example 17.

[0179] The initial charge-discharge efficiency and capacity retention of the test battery cells of Example 18 and Comparative Example 10 are shown in Table 5. Table 5 also shows the composition of the lithium transition metal composite oxide, the added compounds, the method of addition, the amount added, and the structural stress from external sources. The initial charge-discharge efficiency and capacity retention of the test battery cell of Example 18 shown in Table 5 are relative values ​​with the initial charge-discharge efficiency and capacity retention of the test battery cell of Comparative Example 10 set to 100. Similar to Table 1, a higher initial charge-discharge efficiency value indicates better initial charge-discharge efficiency, and a higher capacity retention value indicates better cycle characteristics.

[0180] [Table 5]

[0181]

[0182] As shown in Table 5, the test battery cell of Example 18 showed improved initial charge-discharge efficiency and capacity retention compared to the test battery cell of Comparative Example 10. That is, the effects of this disclosure are achieved even when a surface modification layer containing Ca and W is present on the surface of the primary particles.

[0183] <Comparative Example 11>

[0184] The experimental battery cells were fabricated in the same manner as in Example 1, except as described below, for the preparation of the positive electrode active material.

[0185] The [Ni] obtained by coprecipitation method 0.90 Co 0.05 Mn 0.05 The complex hydroxide represented by [(OH)₂] was calcined at 500°C for 8 hours to obtain a metal oxide. Then, LiOH and the above metal oxide were mixed in a molar ratio of Li to Ni, Co, and Mn of 1.03:1 to obtain a mixture. This mixture was then subjected to an oxygen flow of 95% (per 10 cm⁻¹) 2 The mixture was heated from room temperature to 650°C at a flow rate of 2 mL / min and 5 L / min per 1 kg of mixture, and then heated from 650°C to 780°C at a heating rate of 0.5°C / min and held for 4 hours to obtain a lithium-containing transition metal composite oxide.

[0186] Next, 1000g of the aforementioned lithium-containing transition metal composite oxide was added to 3.0L of pure water and stirred to prepare a suspension. Then, 875mL of a solution prepared by dissolving 3.15g of erbium nitrate pentahydrate [Er(NO3)3·5H2O] in 200mL of pure water was added to this suspension. At this point, to adjust the pH of the suspension to 9.0, a 10% by mass aqueous solution of nitric acid or a 10% by mass aqueous solution of sodium hydroxide was added as appropriate.

[0187] Next, after the addition of the erbium nitrate pentahydrate solution, the mixture was filtered, further washed with water, and then dried at 120°C to obtain a powder with erbium hydroxide adhering as a surface compound on a portion of the surface of the lithium transition metal composite oxide. The powder was analyzed using ICP emission spectroscopy, and the amount of erbium compound adhering to the lithium transition metal composite oxide was found to be 0.50% by mass (erbium elemental conversion). The powder was then heat-treated in air at 300°C for 5 hours to prepare the positive electrode active material. The heat-treated erbium compound was essentially erbium hydroxide oxide.

[0188] <Comparative Example 12>

[0189] In the fabrication of the positive electrode, aluminum hydroxide was used instead of erbium hydroxide as the attached compound, and heat treatment was performed at 400°C. Otherwise, the test cell was fabricated and evaluated in the same manner as Comparative Example 11. The attached aluminum hydroxide almost entirely transformed into oxide after heat treatment. It should be noted that the powder obtained was analyzed using an ICP emission spectrometer, and the results showed that the amount of aluminum compound attached, converted to aluminum elemental composition, was 0.50% by mass relative to the lithium-containing transition metal composite oxide.

[0190] <Comparative Example 13>

[0191] In the fabrication of the positive electrode, magnesium hydroxide was used instead of erbium hydroxide as the attached compound, and heat treatment was performed at 400°C. Otherwise, the test cell was fabricated and evaluated in the same manner as Comparative Example 11. The attached magnesium hydroxide almost entirely transformed into oxide after heat treatment. It should be noted that the powder obtained was analyzed using an ICP emission spectrometer, and the results showed that the amount of attached magnesium compound, converted to magnesium elemental mass, was 0.50% by mass relative to the lithium-containing transition metal composite oxide.

[0192] <Comparative Example 14>

[0193] In the fabrication of the positive electrode, zirconium hydroxide was used instead of erbium hydroxide as the attached compound, and heat treatment was performed at 400°C. Otherwise, the test cell was fabricated and evaluated in the same manner as in Comparative Example 11. The attached zirconium hydroxide almost entirely transformed into oxide after heat treatment. It should be noted that the powder obtained was analyzed using an ICP emission spectrometer, and the results showed that the amount of zirconium compound attached, converted to zirconium oxide, was 0.50% by mass relative to the lithium-containing transition metal composite oxide.

[0194] <Comparative Example 15>

[0195] In the positive electrode active material addition process, tungsten oxide was added instead of lithium methanesulfonate. Otherwise, the test battery cell was fabricated in the same manner as in Example 1. It should be noted that the powder obtained was measured using an ICP emission spectrometer, and the result showed that the amount of tungsten compound attached, calculated as tungsten elemental, was 0.50% by mass relative to the lithium-containing transition metal composite oxide.

[0196] The initial charge-discharge efficiency and capacity retention of the test battery cells of Examples 3 and Comparative Examples 11-15 are shown in Table 6. Table 6 also shows the composition of the lithium transition metal composite oxide, the added compounds, the method of addition, the amount added, and the structural stress from external sources. The initial charge-discharge efficiency and capacity retention of the test battery cells shown in Table 6 are relative values ​​with the initial charge-discharge efficiency and capacity retention of the test battery cell of Comparative Example 1 set to 100. Similar to Table 1, a higher initial charge-discharge efficiency value indicates better initial charge-discharge efficiency, and a higher capacity retention value indicates better cycle characteristics.

[0197] [Table 6]

[0198]

[0199] As shown in Table 6, the test battery cell of Example 3 showed improved initial charge-discharge efficiency and capacity retention compared to the test battery cell of the comparative example. That is, the initial charge-discharge efficiency and capacity retention were significantly improved when sulfonic acid compounds were present on the surface of the secondary particles compared to when Er-containing compounds, Al-containing compounds, Mg-containing compounds, Zr-containing compounds, and W-containing compounds were present on the surface of the particles.

[0200] This disclosure is further illustrated by the following embodiments.

[0201] Option 1: A non-aqueous electrolyte secondary battery comprising an electrode body and a housing for the electrode body, wherein the electrode body has a structure in which a positive electrode and a negative electrode are stacked separated by a separator, the positive electrode having a positive electrode core and a positive electrode agent layer formed on the surface of the positive electrode core and containing a positive electrode active material, the positive electrode active material comprising a lithium-containing transition metal composite oxide having a layered structure, the lithium-containing transition metal composite oxide being composed of the general formula Li x Ni a Co b Mn c M d O 2-y(In the formula, 0.80 < x < 1.20, 0.75 < a ≤ 0.95, 0 ≤ b ≤ 0.15, 0 ≤ c ≤ 0.25, 0 ≤ d ≤ 0.10, 0 ≤ y < 0.05, a + b + c + d = 1, and M is at least one element selected from the group consisting of W, Mg, Mo, Nb, Ti, Si, Al, and Zr), and is a secondary particle formed by aggregation of primary particles. A sulfonic acid compound represented by the formula (I) is present on the surface of the secondary particle. By applying pressure from the outside of the outer casing in the stacking direction of the positive electrode, negative electrode, and separator, a pressure of 8.00 × 10 -2 MPa or more is applied to the electrode body.

[0202]

[0203] (In the formula (I), A is an element of Group I or Group II, R is a hydrocarbon group, and n is 1 or 2.)

[0204] Solution 2: The non-aqueous electrolyte secondary battery according to Solution 1, wherein the aforementioned A is an element of Group I.

[0205] Solution 3: The non-aqueous electrolyte secondary battery according to Solution 1 or 2, wherein the aforementioned A is Li.

[0206] Solution 4: The non-aqueous electrolyte secondary battery according to any one of Solutions 1 to 3, wherein the aforementioned R is an alkyl group.

[0207] Solution 5: The non-aqueous electrolyte secondary battery according to any one of Solutions 1 to 4, wherein the aforementioned R is a methyl group.

[0208] Solution 6: The non-aqueous electrolyte secondary battery according to any one of Solutions 1 to 5, wherein, in the positive electrode active material, the amount of the sulfonic acid compound present on the surface of the lithium-containing transition metal composite oxide is 0.1% by mass or more and 1% by mass or less relative to the mass of the lithium-containing transition metal composite oxide.

[0209] Solution 7: The non-aqueous electrolyte secondary battery according to any one of Solutions 1 to 6, wherein a surface modification layer containing at least one element selected from Ca and Sr is present on the surface of the primary particle.

[0210] Solution 8: A battery pack comprising a plurality of non-aqueous electrolyte secondary batteries according to any one of Solutions 1 to 7. The plurality of non-aqueous electrolyte secondary batteries are arranged in the stacking direction of the positive electrode, negative electrode, and separator, and are mutually constrained in the arrangement direction.

[0211] Explanation of Reference Numerals

[0212] 10 Non-aqueous electrolyte secondary battery, 11 Electrode body, 12 Positive terminal, 13 Negative terminal, 14 Battery casing (outer shell), 15 Casing body, 16 Sealing body, 17 Insulating component, 20 Positive electrode, 21 Negative electrode, 22 Separator, 30 Battery pack, 31 Battery module, 32 Spacer, 33 End plate, 34 Busbar, 35, 36 Connecting rod.

Claims

1. A non-aqueous electrolyte secondary battery, comprising an electrode body and a housing for receiving the electrode body, wherein the electrode body has a structure in which a positive electrode and a negative electrode are stacked together with a separator in between. The positive electrode has a positive electrode core and a positive electrode mixture layer formed on the surface of the positive electrode core and containing positive electrode active material. The positive electrode active material comprises a lithium-containing transition metal composite oxide with a layered structure. The lithium-containing transition metal composite oxide is represented by the general formula Li x Ni a Co b Mn c M d O 2-y and is a secondary particle formed by aggregation of primary particles. In the general formula, 0.80 < x < 1.20, 0.75 < a ≤ 0.95, 0 ≤ b ≤ 0.15, 0 ≤ c ≤ 0.25, 0 ≤ d ≤ 0.10, 0 ≤ y < 0.05, a + b + c + d = 1, and M is at least one element selected from the group consisting of W, Mg, Mo, Nb, Ti, Si, Al, and Zr. A sulfonic acid compound represented by formula (I) is present on the surface of the secondary particles. By applying pressure from the outside of the outer casing towards the stacking direction of the positive electrode, negative electrode, and separator, an 8.00 × 10⁻⁶ pressure is applied to the electrode body. -2 Pressure above MPa In formula (I), A is a group I element or a group II element, R is a hydrocarbon group, and n is 1 or 2.

2. The non-aqueous electrolyte secondary battery according to claim 1, wherein, A is a group 1 element.

3. The non-aqueous electrolyte secondary battery according to claim 1, wherein, A is Li.

4. The non-aqueous electrolyte secondary battery according to claim 1, wherein, R is an alkyl group.

5. The non-aqueous electrolyte secondary battery according to claim 1, wherein, R is a methyl group.

6. The non-aqueous electrolyte secondary battery according to claim 1, wherein, In the positive electrode active material, the amount of the sulfonic acid compound present on the surface of the lithium-containing transition metal composite oxide is 0.1% by mass or more and 1% by mass or less, relative to the mass of the lithium-containing transition metal composite oxide.

7. The non-aqueous electrolyte secondary battery according to claim 1, wherein, The surface of the primary particles contains a surface modification layer containing at least one element selected from Ca and Sr.

8. A battery pack comprising a plurality of non-aqueous electrolyte secondary batteries as described in any one of claims 1 to 7. Multiple non-aqueous electrolyte secondary batteries are arranged in the stacking direction of the positive electrode, negative electrode and separator, and are mutually constrained in the arrangement direction.

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