Positive electrode for non-aqueous electrolyte secondary battery, method of manufacturing the same, method of inspecting the same, non-aqueous electrolyte secondary battery, and method of

Abstract

To provide a nonaqueous electrolyte secondary battery excellent in load characteristics and storage characteristics and its manufacturing method, a positive electrode capable of constituting the nonaqueous electrolyte secondary battery and its manufacturing method, and an inspection method of the positive electrode for manufacturing the nonaqueous electrolyte secondary battery.SOLUTION: The positive electrode for a non-aqueous electrolyte secondary battery of the present invention has a positive electrode mixture layer containing a positive electrode active material and a conductive auxiliary agent on one side or both sides of a current collector, wherein when an interfacial resistance between the positive electrode mixture layer and the current collector is R s (Ω cm2), a volume resistivity of the positive electrode mixture layer is ρ v (Ω cm), and a thickness of the positive electrode mixture layer is d (cm), R s / (ρ v * d) satisfies a specific range according to the thickness of the positive electrode mixture layer. In addition, the non-aqueous electrolyte secondary battery of the present invention includes a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and a non-aqueous electrolyte, in which the positive electrode is the positive electrode for a non-aqueous electrolyte secondary battery of the present invention.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a non-aqueous electrolyte secondary battery having excellent load characteristics and storage characteristics and a method for manufacturing the same, a positive electrode that can be used to form the non-aqueous electrolyte secondary battery and a method for manufacturing the same, and a method for inspecting a positive electrode for manufacturing a non-aqueous electrolyte secondary battery. [Background technology]

[0002] Non-aqueous electrolyte secondary batteries are used as power sources for portable electronic devices such as mobile phones and laptop computers, as well as for electric vehicles, and can contribute to achieving Goal 7 (Ensure access to affordable, reliable, sustainable and modern energy for all) and Goal 12 (Ensure sustainable consumption and production patterns) of the 17 Sustainable Development Goals (SDGs) established by the United Nations.

[0003] Furthermore, with the diversification of applications of non-aqueous electrolyte secondary batteries, there are cases where improvements in load characteristics, for example, are required.

[0004] In order to improve the load characteristics of a non-aqueous electrolyte secondary battery, for example, it is effective to reduce the resistance value of the electrodes.

[0005] Although not intended to improve the load characteristics of a battery, Patent Document 1 proposes that, in a lithium-ion battery electrode in which an electrode active material layer containing an electrode active material, a conductive additive, etc. is provided on at least one surface of a collector layer, the interface resistance between the electrode active material layer and the collector layer be set within a specific range. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] International Publication No. 2018 / 016528 Summary of the Invention [Problem to be solved by the invention]

[0007] One way to reduce the resistance of the electrode is to increase the amount of conductive additive, but this would result in a decrease in the storage characteristics of the battery. For these reasons, there is a need to develop a technology that can achieve both the load characteristics and storage characteristics of non-aqueous electrolyte secondary batteries.

[0008] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a non-aqueous electrolyte secondary battery having excellent load characteristics and storage characteristics, a method for manufacturing the same, a positive electrode that can constitute the non-aqueous electrolyte secondary battery, a method for manufacturing the same, and a method for inspecting a positive electrode for use in manufacturing a non-aqueous electrolyte secondary battery. [Means for solving the problem]

[0009] The positive electrode for a non-aqueous electrolyte secondary battery of the present invention has a positive electrode mixture layer containing a positive electrode active material and a conductive additive on one or both sides of a current collector, and the interface resistance between the positive electrode mixture layer and the current collector is Rs (Ωcm 2 ), the volume resistivity of the positive electrode mixture layer is ρv (Ωcm), and the thickness of the positive electrode mixture layer (the thickness per one side of the current collector; the same applies hereinafter to the "thickness of the positive electrode mixture layer" in this specification) is d (cm), Rs / (ρv×d) has the following value:

[0010] (1) When the thickness of the positive electrode mixture layer is 35 μm or more and less than 58 μm, Rs / (ρv×d) is 1.0±0.2. (2) When the thickness of the positive electrode mixture layer is 58 μm or more and less than 68 μm, Rs / (ρv×d) is 0.55 to 1.6. (3) When the thickness of the positive electrode mixture layer is 68 μm or more and 80 μm or less, Rs / (ρv×d) is 0.55 to 10.

[0011] The nonaqueous electrolyte secondary battery of the present invention comprises a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and a nonaqueous electrolyte, and is characterized in that the positive electrode is the positive electrode for the nonaqueous electrolyte secondary battery of the present invention.

[0012] Furthermore, the method for producing a positive electrode for a non-aqueous electrolyte secondary battery of the present invention is characterized in that, when a positive electrode mixture layer containing a positive electrode active material and a conductive additive is formed on one or both surfaces of a current collector, the thickness of the positive electrode mixture layer and Rs / (ρv×d) are adjusted to the value of (1), (2), or (3) above.

[0013] Furthermore, the method for producing a nonaqueous electrolyte secondary battery of the present invention is characterized in that, when producing a nonaqueous electrolyte secondary battery having a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and a nonaqueous electrolyte, the positive electrode for a nonaqueous electrolyte secondary battery produced by the method for producing a positive electrode for a nonaqueous electrolyte secondary battery of the present invention is used as the positive electrode.

[0014] Furthermore, the present invention provides a positive electrode for a non-aqueous electrolyte secondary battery having a positive electrode mixture layer containing a positive electrode active material and a conductive additive on one or both sides of a current collector, the positive electrode mixture layer having an interface resistance Rs (Ωcm) between the positive electrode mixture layer and the current collector. 2 ), the volume resistivity ρv (Ωcm) of the positive electrode mixture layer, and the thickness d (cm) of the positive electrode mixture layer to calculate the value of Rs / (ρv×d); and selecting nonaqueous electrolyte secondary batteries to which the positive electrode for nonaqueous electrolyte secondary batteries is applied based on the value of Rs / (ρv×d). [Effects of the Invention]

[0015] According to the present invention, it is possible to provide a non-aqueous electrolyte secondary battery having excellent load characteristics and storage characteristics and a method for manufacturing the same, a positive electrode that can constitute the non-aqueous electrolyte secondary battery and a method for manufacturing the same, and a method for inspecting a positive electrode for manufacturing a non-aqueous electrolyte secondary battery. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a plan view schematically illustrating an example of a nonaqueous electrolyte secondary battery of the present invention. [Figure 2] FIG. 2 is a cross-sectional view taken along line II in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0017] <Cathode for non-aqueous electrolyte secondary batteries> The positive electrode for a non-aqueous electrolyte secondary battery of the present invention (hereinafter, may be simply referred to as "positive electrode") has a positive electrode mixture layer containing a positive electrode active material and a conductive additive on one or both sides of a current collector, and the value of Rs / (ρv×d) falls within a specific range depending on the thickness of the positive electrode mixture layer.

[0018] As described above, when the resistance value of the positive electrode is reduced by a common method in order to improve the load characteristics of a non-aqueous electrolyte secondary battery, the storage characteristics of the battery are likely to be impaired. As a result of extensive research, the present inventors have found that when the interfacial resistance Rs between the positive electrode mixture layer and the current collector in the positive electrode and the product ρv×d of the volume resistivity (ρv) of the positive electrode mixture layer and the thickness (d) of the positive electrode mixture layer satisfy a specific relationship, a battery using this positive electrode can achieve both high levels of load characteristics and storage characteristics, and that the relationship between Rs and ρv×d that achieves both the load characteristics and storage characteristics of the battery varies depending on the thickness of the positive electrode mixture layer, thereby completing the present invention.

[0019] The positive electrode of the present invention has a positive electrode mixture layer containing a positive electrode active material and a conductive additive.

[0020] The positive electrode active material is not particularly limited as long as it is a positive electrode active material used in conventionally known non-aqueous electrolyte secondary batteries, that is, an active material capable of absorbing and releasing Li ions. Specific examples of the positive electrode active material include LiM x Mn 2-x Spinel-type lithium manganese composite oxide represented by LiO4 (wherein M is at least one element selected from the group consisting of Li, B, Mg, Ca, Sr, Ba, Ti, V, Cr, Fe, Co, Ni, Cu, Al, Sn, Sb, In, Nb, Mo, W, Y, Ru, and Rh, and 0.01≦x≦0.5), Li x Ni (1-y-z) Mn y M z O (2-k) F l(wherein M is at least one element selected from the group consisting of Co, Mg, Al, B, Ti, V, Cr, Fe, Cu, Zn, Zr, Mo, Sn, Ca, Sr, Ba, and W, and 0.8≦x≦1.2, 0≦y≦0.5, 0≦z≦0.5, k+l<1, -0.1≦k≦0.2, 0≦l≦0.1), a layered compound represented by LiCo 1-x M x Lithium cobalt composite oxide represented by LiNiO2 (wherein M is at least one element selected from the group consisting of Al, Mg, Ti, Zr, Fe, Ni, Cu, Zn, Ga, Ge, Nb, Mo, Sn, Sb, and Ba, and 0≦x≦0.5), 1-x M x Lithium nickel composite oxide represented by LiM02 (wherein M is at least one element selected from the group consisting of Al, Mg, Ti, Zr, Fe, Co, Cu, Zn, Ga, Ge, Nb, Mo, Sn, Sb, Mn, and Ba, and 0≦x≦0.5) 1-x N x olivine-type composite oxides represented by Li4Ti5O4 (wherein M is at least one element selected from the group consisting of Fe, Mn, and Co, and N is at least one element selected from the group consisting of Al, Mg, Ti, Zr, Ni, Cu, Zn, Ga, Ge, Nb, Mo, Sn, Sb, and Ba, and 0≦x≦0.5); 12 Among these, only one kind may be used, or two or more kinds may be used in combination.

[0021] Examples of the conductive additive for the positive electrode mixture layer include graphite; amorphous carbon materials such as carbon black (acetylene black, ketjen black, etc.) and carbon materials having amorphous carbon formed on the surface; fibrous carbon (vapor-grown carbon fiber, carbon fiber obtained by spinning pitch and then carbonizing it, etc.); carbon nanotubes (various multi-layer or single-layer carbon nanotubes); and the like. Only one of these may be used, or two or more may be used in combination.

[0022] The positive electrode mixture layer usually contains a binder, such as polyvinylidene fluoride (PVDF), polytetrafluoroethylene, polyacrylic acid, chitosan, styrene-butadiene rubber (SBR), or carboxymethyl cellulose (CMC).

[0023] In the positive electrode, the ratio "Rs / (ρv×d)" of the interfacial resistance (Rs) between the positive electrode mixture layer and the current collector to the product of the volume resistivity (ρv) of the positive electrode mixture layer and the thickness (d) of the positive electrode mixture layer (ρv×d) falls within a specific range as shown below, depending on the thickness of the positive electrode mixture layer. By using such a positive electrode, it is possible to achieve both high levels of load characteristics and storage characteristics of the nonaqueous electrolyte secondary battery.

[0024] (1) When the thickness of the positive electrode mixture layer is 35 μm or more (preferably 38 μm or more) and less than 58 μm, Rs / (ρv×d) is 1.0±0.2.

[0025] (2) When the thickness of the positive electrode mixture layer is 58 μm or more and less than 68 μm, Rs / (ρv×d) is 0.55 or more (preferably 0.8 or more) and 1.6 or less (preferably 1.26 or less).

[0026] (3) When the thickness of the positive electrode mixture layer is 68 μm or more and 80 μm or less, Rs / (ρv×d) is 0.55 or more (preferably 0.7 or more) and 10 or less (preferably 3.0 or less, more preferably 1.7 or less).

[0027] While it is unclear why adjusting the positive electrode to (1), (2), or (3) above can achieve both high load and storage characteristics in a nonaqueous electrolyte secondary battery, we believe the reason is as follows: In electrodes where the interfacial resistance between the current collector and the composite layer is sufficiently larger than the resistance of the composite layer (i.e., Rs / (ρv×d) is significantly larger than 1) or sufficiently smaller than the resistance of the composite layer (i.e., Rs / (ρv×d) is significantly smaller than 1), the conductive additive contained in the composite layer of the electrode is thought to be inefficient. In contrast, in electrodes where the interfacial resistance between the current collector and the composite layer is related to the resistance of the composite layer within a certain range (e.g., Rs / (ρv×d) is close to 1), the conductive additive contained in the composite layer of the electrode is thought to more efficiently conduct electrons to the current collector. Therefore, we speculate that adjusting the value of Rs / (ρv×d) within a specific range can improve the load characteristics without compromising the battery's storage characteristics.

[0028] It is essentially preferable that the value of Rs / (ρv×d) be close to 1.0, but it has been found that the thicker the positive electrode mixture layer, the more the effect of achieving both good load characteristics and good storage characteristics of the nonaqueous electrolyte secondary battery can be ensured, even if the value of Rs / (ρv×d) is somewhat different from 1.0, compared to when the value of Rs / (ρv×d) is farther from 1.0.

[0029] In the case of (1) above, Rs is actually 0.003 Ω cm 2 or more, and 0.005 Ωcm 2 In the above cases, manufacturing is easier. In addition, Rs in the case of (1) is 1.2 Ωcm. 2 Preferably, it is 0.8Ωcm or less. 2 More preferably, it is 0.5 Ωcm or less. 2In the case of (1), ρv is preferably 0.5 Ωcm or more, more preferably 1.0 Ωcm or more, and even more preferably 1.5 Ωcm or more, and is preferably 200 Ωcm or less, more preferably 140 Ωcm or less, even more preferably 90 Ωcm or less, and particularly preferably 70 Ωcm or less.

[0030] In the case of (2) above, Rs is actually 0.003 Ω cm 2 or more, and 0.005 Ωcm 2 In this case, manufacturing is easy and the resistance is 0.008Ωcm. 2 In the above case, manufacturing is easier. In addition, Rs in the case of (2) is 1.4 Ωcm. 2 Preferably, it is 0.9 Ωcm or less. 2 More preferably, it is 0.6 Ωcm or less. 2 More preferably, it is 0.4 Ωcm or less. 2 In the case of (2), ρv is preferably 0.4 Ωcm or more, more preferably 0.9 Ωcm or more, and even more preferably 1.4 Ωcm or more, and is preferably 200 Ωcm or less, more preferably 140 Ωcm or less, even more preferably 90 Ωcm or less, and especially preferably 70 Ωcm or less.

[0031] In the case of (3) above, Rs is actually 0.003 Ω cm 2 or more, and 0.005 Ωcm 2 In this case, manufacturing is easy and the resistance is 0.008Ωcm. 2 In the above cases, manufacturing is easier. In addition, Rs in the case of (3) is 1.6 Ωcm. 2 Preferably, it is 1.0 Ωcm or less. 2 More preferably, it is 0.7 Ωcm or less. 2 More preferably, it is 0.5 Ωcm or less. 2In the case of (3), ρv is preferably 0.4 Ωcm or more, more preferably 0.9 Ωcm or more, and even more preferably 1.4 Ωcm or more, and is preferably 200 Ωcm or less, more preferably 140 Ωcm or less, even more preferably 90 Ωcm or less, and especially preferably 70 Ωcm or less.

[0032] In the case of (1) above, the thickness of the positive electrode mixture layer is set to 35 μm or more because when the thickness of the positive electrode mixture layer is thin, such as less than 35 μm, the load characteristics and storage characteristics of the battery tend to be satisfactory.

[0033] In the case of (3) above, the thickness of the positive electrode mixture layer is set to 80 μm or less because, if the positive electrode mixture layer is thicker than this, it becomes difficult to adjust the value of Rs / (ρv×d) that can achieve both the load characteristics and storage characteristics of the battery. Furthermore, as will be described later, the positive electrode of the present invention is preferably produced via a process of applying to a current collector a positive electrode mixture-containing composition in which a positive electrode active material and a conductive additive are dispersed in a solvent, but it is not easy to form a positive electrode mixture layer with a thickness of more than 80 μm while adjusting the value of Rs / (ρv×d) using such a production method.

[0034] As described above, the thickness of the positive electrode mixture layer in this specification means the thickness per one surface of the current collector. However, in the case of a positive electrode having an undercoat layer, which will be described later, the thickness of the positive electrode mixture layer means the total thickness of the undercoat layer formed on the current collector and the positive electrode mixture layer formed thereon.

[0035] The thickness of the positive electrode mixture layer referred to in this specification means the average value (number average value) of thicknesses of the positive electrode mixture layer obtained at 10 arbitrary points in a field of view obtained by cutting out a cross section of the positive electrode and observing the cross section with a scanning electron microscope (SEM) at a magnification of 1000 times using an SEM scale.

[0036] Furthermore, Rs and ρv of the positive electrode referred to in this specification refer to values ​​determined by the following method. The thickness of the positive electrode mixture layer is determined by the above method, and the thickness of the current collector is also determined by the same method. Then, using an electrode resistance measurement system "RM2610 (trade name)" manufactured by Hioki E.E. Corporation, the thickness (μm) and resistivity (Ωcm) of the positive electrode current collector and the thickness (μm) of the positive electrode mixture layer are input, and then the positive electrode, which is the measurement sample, is set in the system, and the probe is lowered to start measurement, thereby determining the interfacial resistance: Rs (Ωcm) between the positive electrode mixture layer and the current collector. 2 ) and the volume resistivity ρv (Ωcm) of the positive electrode mixture layer are determined. During this measurement, the measurement speed is set to Normal, the voltage range is set to 0.5 V, and the maximum current value that makes the voltage V1 calculated by the system software 0.1 V or less is selected from among 50 mA, 10 mA, 1 mA, 100 μA, and 10 μA.

[0037] The resistivity (Ωcm) of the current collector input to the system is a known resistivity determined by the composition of the positive electrode current collector used. Furthermore, elemental analysis is performed on a current collector obtained from a portion of the positive electrode obtained from a battery to identify its composition, and the known resistivity is used. Furthermore, the positive electrode in the nonaqueous electrolyte secondary battery is removed from the outer casing of the discharged battery and washed multiple times with diethyl carbonate before the above measurements.

[0038] Furthermore, Rs / (ρv×d) of the positive electrode as referred to in this specification means the average value (number average value) of the remaining five values, obtained by measuring Rs and ρv at any 15 points on one measurement sample using the above-mentioned method and calculating Rs / (ρv×d), and then excluding the five points with the largest values ​​and the five points with the smallest values.

[0039] The current collector of the positive electrode can be made of a metal foil such as aluminum or stainless steel, punched metal, mesh, expanded metal, foamed metal, carbon sheet, etc. The thickness of the current collector is preferably 5 to 30 μm.

[0040] The positive electrode can be obtained, for example, by dispersing a positive electrode mixture containing a positive electrode active material, a conductive additive, and a binder in an organic solvent such as N-methyl-2-pyrrolidone (NMP) to prepare a slurry or paste-like positive electrode mixture-containing composition (the binder may be dissolved in the solvent), applying this to one or both sides of a current collector, drying it, and, if necessary, performing a pressing process such as calendaring.

[0041] During the manufacturing of the positive electrode, the value of Rs / (ρv×d) is adjusted to a value corresponding to the thickness of the positive electrode mixture layer. Generally, rapid drying during drying after coating the positive electrode mixture-containing composition on the current collector causes migration of the conductive additive in the coating film of the positive electrode mixture-containing composition, resulting in a tendency for the conductive additive content on the surface of the formed positive electrode mixture layer (the surface opposite the current collector) to be higher than in other portions of the positive electrode mixture layer. This phenomenon tends to cause the value of Rs / (ρv×d) to deviate from 1.0 and become larger. This phenomenon is particularly pronounced when the positive electrode mixture layer is thick. Therefore, by minimizing the uneven concentration of the conductive additive in the positive electrode mixture layer due to migration of the conductive additive in the coating film of the positive electrode mixture-containing composition during the drying process, it becomes possible to adjust the value of Rs / (ρv×d) to the above-mentioned range corresponding to the thickness of the positive electrode mixture layer.

[0042] Specifically, for example, when drying a coating of a positive electrode mixture-containing composition, in addition to drying at a constant temperature, methods include using multiple drying ovens to gradually increase the temperature of the ovens and dry slowly; leaving the evaporated solvent in the oven to delay drying of the surface; maintaining a uniform electrode temperature by preventing wind exposure to minimize drying of the surface; blowing wind from the opposite side of the coated surface to minimize drying of the surface; drying by radiant heat using electromagnetic waves such as far-infrared and near-infrared infrared rays; and applying heat directly to the uncoated side (foil side) using a guide roll or a metal plate like a hot plate. In particular, with a roll-to-roll method, the drying time can be easily adjusted by changing the length of the drying oven (the length of the path within the drying oven) and the coating speed. Furthermore, using multiple drying ovens to gradually increase the temperature of the drying ovens and dry slowly is effective in easily controlling unevenness in the concentration of the conductive additive in the positive electrode mixture layer.

[0043] It is also preferable to increase the viscosity of the positive electrode mixture-containing composition, which also reduces unevenness in the concentration of the conductive additive in the positive electrode mixture layer and allows the value of Rs / (ρv×d) to be adjusted within the range described above depending on the thickness of the positive electrode mixture layer. Furthermore, depending on the type of positive electrode mixture, for example, a solids concentration (total concentration of all components excluding the solvent) of the positive electrode mixture-containing composition of approximately 75 to 90 mass % is preferable because this prevents the conductive additive or binder from migrating to the surface of the wet coating film when the coating film of the positive electrode mixture-containing composition is dried. However, the method for adjusting Rs / (ρv×d) does not depend solely on the solids concentration.

[0044] Furthermore, the value of Rs / (ρv×d) can also be adjusted to fall within the above-described range according to the thickness of the positive electrode mixture layer by forming an undercoat layer containing a conductive additive on the surface of the current collector in advance and then forming a positive electrode mixture layer thereon by the above-described method (method using a positive electrode mixture-containing composition).

[0045] In this case, the conductive additive contained in the undercoat layer may be the same as the various conductive additives exemplified above as those that can be contained in the positive electrode mixture layer. The undercoat layer may be formed using only the conductive additive, but may also contain a binder together with the conductive additive, and the same binder as the various binders exemplified above as those that can be contained in the positive electrode mixture layer may be used.

[0046] The undercoat layer preferably has a thickness of 50 to 1000 nm. In the undercoat layer, the content of the conductive additive is, for example, 1 to 100 mass %, and the content of the binder is, for example, 0 to 99 mass %.

[0047] The undercoat layer can be formed by applying an undercoat layer-forming composition (the binder may be dissolved in the solvent) prepared by dispersing a conductive additive and an optional binder in an organic solvent such as NMP to the surface of a current collector and drying the composition. In the case of a positive electrode having an undercoat layer, a positive electrode mixture-containing composition is applied to the surface of the undercoat layer formed on the surface of the current collector, and the positive electrode mixture layer is formed by the method described above. Alternatively, the undercoat layer and the positive electrode mixture layer can be simultaneously formed by applying a positive electrode mixture-containing composition over the undercoat layer-forming composition (the coating film) applied to the surface of the current collector without drying it, and then drying the composition, and optionally performing a pressing process.

[0048] The content of the positive electrode active material in the positive electrode mixture layer is preferably 90 to 99.3 mass %.

[0049] Furthermore, the content of the conductive additive in the positive electrode mixture layer (including the amount of the conductive additive in the undercoat layer when the positive electrode has an undercoat layer) is preferably 0.2% by mass or more, more preferably 1.0% by mass or more, and even more preferably 1.5% by mass or more. It is preferably less than 9.5% by mass, more preferably less than 5.0% by mass, and even more preferably less than 4.2% by mass. Increasing the amount of conductive additive in the positive electrode mixture layer can reduce the resistance of the positive electrode mixture layer, which tends to improve the load characteristics of the battery but also tends to deteriorate the storage characteristics of the battery. However, in the positive electrode of the present invention, by setting the value of Rs / (ρv×d) within the above-described range corresponding to the thickness of the positive electrode mixture layer, it is possible to improve the load characteristics while suppressing deterioration in the storage characteristics of the battery by limiting the amount of conductive additive in the positive electrode mixture layer as described above.

[0050] Furthermore, the content of the binder in the positive electrode mixture layer (including the amount of binder contained in the undercoat layer when the positive electrode has an undercoat layer) is preferably 0.5 to 3 mass %.

[0051] If necessary, a lead body for electrically connecting the positive electrode to other components in the non-aqueous electrolyte secondary battery may be formed in a conventional manner.

[0052] <Nonaqueous electrolyte secondary battery> The non-aqueous electrolyte secondary battery of the present invention has a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and a non-aqueous electrolyte, and the positive electrode is the positive electrode for the non-aqueous electrolyte secondary battery of the present invention.

[0053] The negative electrode can have a structure in which a negative electrode mixture layer containing a negative electrode active material, a binder, and optionally a conductive additive, is provided on one or both sides of a current collector. Alternatively, a foil made of a metal such as Li or a Li alloy (e.g., a Li-Al alloy) that acts as the negative electrode active material can be used as is, or a negative electrode in which the foil is attached to one or both sides of a current collector can be used. Furthermore, a battery can be assembled using an Al foil or Al alloy foil as the negative electrode (negative electrode precursor), and charging can be performed to form a Li-Al alloy in the negative electrode by Li ions migrating from the positive electrode to the negative electrode.

[0054] In a negative electrode having a negative electrode mixture layer, the negative electrode active material can be a negative electrode active material used in the negative electrodes of conventionally known nonaqueous electrolyte secondary batteries, i.e., an active material capable of absorbing and releasing Li ions. Specific examples of such negative electrode active materials include graphite (natural graphite; artificial graphite obtained by graphitizing easily graphitizable carbons such as pyrolytic carbons, MCMB, and carbon fiber at 2800°C or higher; etc.), pyrolytic carbons, cokes, glassy carbons, fired bodies of organic polymer compounds, mesocarbon microbeads, carbon fiber, activated carbon, soft carbon, hard carbon, and other carbon materials; and particles of metals that can be alloyed with lithium (e.g., Si, Sn), and materials containing these metals (e.g., alloys, oxides, etc.). The negative electrode may use only one of the above-listed negative electrode active materials, or two or more of them in combination.

[0055] The binder for the negative electrode mixture layer may be the same as the various binders exemplified above as those usable for the positive electrode mixture layer. In addition, when a conductive additive is contained in the negative electrode mixture layer, the conductive additive may be the same as the various conductive additives exemplified above as those usable for the positive electrode mixture layer.

[0056] A negative electrode having a negative electrode mixture layer is manufactured, for example, by preparing a paste or slurry negative electrode mixture-containing composition by dispersing a negative electrode active material, a binder, and optionally a conductive additive in a solvent such as an organic solvent such as NMP or water (however, the binder may be dissolved in the solvent), applying this to one or both sides of a current collector, drying, and then, if necessary, performing a pressing process such as calendaring. However, the negative electrode is not limited to one manufactured by the above manufacturing method, and may be one manufactured by other methods.

[0057] Furthermore, if necessary, a lead body for electrically connecting the negative electrode to other members within the non-aqueous electrolyte secondary battery may be formed in a conventional manner.

[0058] The thickness of the negative electrode mixture layer is preferably, for example, 10 to 100 μm per side of the current collector. The composition of the negative electrode mixture layer preferably includes, for example, a negative electrode active material content of 85 to 99 mass % and a binder content of 1 to 10 mass %. When a conductive additive is contained in the negative electrode mixture layer, the amount of the conductive additive in the negative electrode mixture layer is preferably 0.5 to 10 mass %. When a negative electrode is formed using a foil of Li or a Li alloy, the thickness of the foil is preferably 8 to 20 μm.

[0059] The negative electrode current collector may be made of copper, copper alloy, nickel, or nickel alloy foil, punched metal, mesh, expanded metal, etc., but copper foil is usually used. The thickness of the negative electrode current collector is preferably, for example, 5 to 30 μm.

[0060] The separator for a non-aqueous electrolyte secondary battery should have sufficient strength and be capable of retaining a large amount of non-aqueous electrolyte, and can be a microporous membrane made of polyolefin such as polyethylene (PE) or polypropylene (PP). The microporous membrane constituting the separator may be, for example, one made of only PE or only PP, or may contain an ethylene-propylene copolymer, or may be a laminate of a microporous membrane made of PE and a microporous membrane made of PP.

[0061] Furthermore, the separator may be a laminated type separator composed of a porous layer mainly made of a resin with a melting point of 140°C or lower and a porous layer mainly made of a resin with a melting point of 150°C or higher or an inorganic filler with a heat resistance temperature of 150°C or higher. Here, "melting point" refers to the melting temperature measured using a differential scanning calorimeter (DSC) in accordance with the provisions of Japanese Industrial Standards (JIS) K 7121, and "heat resistance temperature of 150°C or higher" means that no deformation such as softening is observed at least at 150°C.

[0062] The thickness of the separator (a separator made of a microporous polyolefin film or the laminated separator) is more preferably 10 to 30 μm.

[0063] A nonaqueous liquid electrolyte (nonaqueous electrolyte solution) is usually used as the nonaqueous electrolyte of a nonaqueous electrolyte secondary battery. The nonaqueous electrolyte solution is prepared by dissolving an electrolyte salt such as a lithium salt in an organic solvent. The organic solvent is not particularly limited, but examples thereof include chain esters such as dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, and methyl propyl carbonate; cyclic esters with high dielectric constants such as ethylene carbonate, propylene carbonate, butylene carbonate, and vinylene carbonate; and mixed solvents of chain esters and cyclic esters. Mixed solvents of chain esters as the main solvent and cyclic esters are particularly suitable.

[0064] Examples of electrolyte salts that can be dissolved in an organic solvent to prepare a non-aqueous electrolyte include LiPF6, LiBF4, LiAsF6, LiSbF6, LiCF3SO3, LiC4F9SO3, LiCF3CO2, Li2C2F4(SO3)2, and LiC n F 2n+1SO3 (n≧2), LiN(RfSO2)(Rf'SO2), LiC(RfSO2)3, LiN(RfOSO2)2 (where Rf and Rf' are fluoroalkyl groups), etc. may be used alone or in combination. The concentration of the electrolyte salt in the nonaqueous electrolyte is not particularly limited, but is preferably 0.3 mol / L or more, more preferably 0.4 mol / L or more, and is preferably 1.7 mol / L or less, more preferably 1.5 mol / L or less.

[0065] In the nonaqueous electrolyte secondary battery, in addition to the nonaqueous electrolyte solution, a gel electrolyte obtained by gelling the nonaqueous electrolyte solution with a gelling agent made of a polymer or the like, or a known solid electrolyte can also be used as the nonaqueous electrolyte.

[0066] In the non-aqueous electrolyte secondary battery, the positive electrode and the negative electrode can be used in the form of a laminated electrode body in which they are laminated with a separator interposed therebetween, or in the form of a wound electrode body in which this laminated electrode body is wound.

[0067] 1 and 2 are diagrams schematically showing an example of a nonaqueous electrolyte secondary battery of the present invention, in which Fig. 1 is a plan view of the nonaqueous electrolyte secondary battery, and Fig. 2 is a cross-sectional view taken along line II in Fig. 1.

[0068] The nonaqueous electrolyte secondary battery 1 shown in Figures 1 and 2 houses an electrode assembly 2 in a laminate film exterior body 5 made of two metal laminate films, and the laminate film exterior body 5 is sealed at its outer periphery by heat-sealing the upper and lower metal laminate films.

[0069] The electrode body 2 is a laminated electrode body or a wound electrode body constructed by laminating a positive electrode for a non-aqueous electrolyte secondary battery of the present invention, a negative electrode, and a separator interposed therebetween, and the electrode body 2 and a non-aqueous electrolyte are enclosed in a laminate film outer casing 5.

[0070] In Figure 2, in order to avoid cluttering the drawing, the layers that make up the laminate film exterior body 5 and the components that make up the electrode body 2 (positive electrode, negative electrode, and separator) are not shown separately.

[0071] The positive electrode of the electrode body 2 is connected to a positive electrode external terminal 3 inside the battery 1, and although not shown, the negative electrode of the electrode body 2 is also connected to a negative electrode external terminal 4 inside the battery 1. One end of each of the positive electrode external terminal 3 and the negative electrode external terminal 4 is drawn out to the outside of the laminate film exterior body 5 so that they can be connected to external devices, etc.

[0072] A nonaqueous electrolyte secondary battery is manufactured by, for example, placing an electrode assembly, such as a laminated electrode assembly or a wound electrode assembly, into an exterior housing, injecting a nonaqueous electrolyte into the exterior housing to immerse the electrode assembly in the nonaqueous electrolyte, and then sealing the opening of the exterior housing. Examples of exterior housings that can be used include steel, aluminum, or aluminum alloy exterior cans, and exterior housings made of metal-deposited laminated films. More specific examples of batteries with exterior cans include flat (including coin and button) battery cases in which the exterior can and a sealing plate are crimped and sealed with a gasket or welded to each other; and cylindrical (cylindrical, rectangular, etc.) exterior cans with a bottom, in which a lid is placed over the opening and sealed with a gasket or by welding the exterior can and lid.

[0073] <Inspection method for positive electrodes for non-aqueous electrolyte secondary batteries> The value of Rs / (ρv×d) obtained for a positive electrode for a non-aqueous electrolyte secondary battery is an index of the load characteristics and storage characteristics of a non-aqueous electrolyte secondary battery having this positive electrode. Therefore, for a positive electrode for a non-aqueous electrolyte secondary battery, the interfacial resistance Rs (Ωcm) between the positive electrode mixture layer and the current collector is 2The inspection method of the present invention includes the steps of measuring the Rs / (ρv×d) value, the volume resistivity ρv (Ωcm) of the positive electrode mixture layer, and the thickness d (cm) of the positive electrode mixture layer to calculate the value of Rs / (ρv×d), and selecting nonaqueous electrolyte secondary batteries to which the positive electrode for nonaqueous electrolyte secondary batteries is applied based on the value of Rs / (ρv×d). Even if a positive electrode is determined by the inspection method of the present invention to have an Rs / (ρv×d) value that does not satisfy any of the above (1) to (3) and is therefore unusable for manufacturing the nonaqueous electrolyte secondary battery of the present invention, it can still be used for batteries that do not require high load characteristics, and can therefore be used for manufacturing such batteries. [Example]

[0074] The present invention will be described in detail below based on examples, but the present invention is not limited to these examples.

[0075] Example 1 <Preparation of positive electrode> Li 1.01 Ni 0.5 Co 0.2 Mn 0.3 O2 (positive electrode active material), acetylene black (conductive additive), and PVDF (binder) were mixed in a mass ratio of 94:4:2 and dispersed in NMP to prepare a positive electrode mixture-containing slurry (solid concentration excluding the solvent: 75 mass%).

[0076] This positive electrode mixture-containing slurry was intermittently applied to one side of a 15 μm-thick aluminum foil serving as a current collector. A drying furnace with three dryers was used, with the most upstream dryer 1 set to 110 °C, the middle dryer 2 set to 105 °C, and the most downstream dryer 3 set to 110 °C. A positive electrode mixture layer was formed by drying. The same procedure was then performed on the other side of the aluminum foil to form a positive electrode mixture layer on both sides of the aluminum foil. After drying, the aluminum foil was calendered to adjust the thickness of the positive electrode mixture layer to a total thickness of 95 μm. This was then cut to produce a long positive electrode. Furthermore, aluminum leads for extracting current were welded to the exposed portions of the aluminum foil to obtain a lead-attached positive electrode. The thickness of the positive electrode mixture layer in the resulting positive electrode was 40 μm per side of the current collector.

[0077] <Preparation of negative electrode> Graphite (negative electrode active material), CMC (binder), and SBR (binder) were mixed in a mass ratio of 96:2:2 and dispersed in water to prepare a paste containing a negative electrode mixture.

[0078] This negative electrode mixture-containing paste was intermittently applied to both sides of a 10 μm-thick copper foil current collector, dried, and then calendered to adjust the thickness of the negative electrode mixture layer to a total thickness of 102 μm. This was cut to prepare a long negative electrode. Furthermore, nickel leads for extracting current were welded to the exposed portions of the copper foil to obtain a lead-attached negative electrode. The thickness of the negative electrode mixture layer in the obtained negative electrode was 46 μm per side of the current collector.

[0079] <Preparation of non-aqueous electrolyte> LiPF6 was dissolved at a concentration of 1.0 mol / l in a solvent prepared by mixing ethylene carbonate and diethyl carbonate in a volume ratio of 3:7, and vinylene carbonate was further added in an amount to give a concentration of 2 mass % to prepare a non-aqueous electrolyte solution.

[0080] <Assembly of non-aqueous electrolyte secondary battery> The positive electrode and the negative electrode were stacked with a separator (a 16 μm thick, 40% porosity microporous membrane made of polyethylene) in between, and wound into a spiral to prepare a wound electrode body. The wound electrode body and the nonaqueous electrolyte solution were then enclosed in an aluminum laminate film exterior to prepare a nonaqueous electrolyte secondary battery.

[0081] Comparative Example 1 A positive electrode mixture-containing slurry was prepared in the same manner as in Example 1, except that the positive electrode active material, the conductive additive, and the binder were mixed in a mass ratio of 93:5:2 and the solid content concentration of the positive electrode mixture-containing slurry was adjusted to 72 mass %. A positive electrode was then fabricated in the same manner as in Example 1, except that this positive electrode mixture-containing slurry was used, and a nonaqueous electrolyte secondary battery was fabricated in the same manner as in Example 1, except that this positive electrode was used.

[0082] Comparative Example 2 A positive electrode was produced in the same manner as in Example 1, except that the coating film of the positive electrode mixture-containing slurry was dried using a drying furnace having three dryers, with the most upstream dryer 1 set to 105°C, the intermediate dryer 2 set to 110°C, and the most downstream dryer 3 set to 110°C. A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1, except that this positive electrode was used.

[0083] The nonaqueous electrolyte secondary batteries of Example 1 and Comparative Examples 1 and 2 were evaluated as follows.

[0084] [Low temperature load characteristic evaluation] The batteries of the examples and comparative examples were charged at a constant current of 0.5 C up to 4.2 V, and then at a constant voltage of 4.2 V, they were charged at a constant current of 0.02 C. Thereafter, each battery was discharged at a constant current of 1 C at room temperature (25°C) until the voltage reached 2.75 V, and the initial discharge capacity was measured.

[0085] Each discharged battery was charged in the same manner as the charging method described above, then placed in a thermostatic chamber adjusted to 0°C, and after the battery temperature had dropped, it was discharged at a constant current of 1 C until the voltage reached 2 V, and the discharge capacity (low-temperature 1 C discharge capacity) was measured. The low-temperature 1 C discharge capacity was then divided by the initial discharge capacity to evaluate the low-temperature load characteristics of each battery.

[0086] [85℃ storage characteristics evaluation] Five batteries from each of the examples and comparative examples were subjected to constant current charging and constant voltage charging under the same conditions as those used to measure the initial discharge capacity during the low-temperature load characteristic evaluation. After charging, each battery was sandwiched between two flat plates with an area sufficient to cover the entire flat surface of the exterior body, and a pressure of 0.5 N / cm was applied. 2 The thickness of the battery (thickness before storage) was measured using a gauge while applying a force of 100 kJ / s.

[0087] The batteries whose thickness before storage was measured were stored in a thermostatic chamber adjusted to 85°C for 24 hours, then removed and cooled at room temperature (25°C) for 3 hours, after which the thickness of the batteries (thickness after storage) was measured in the same manner as the thickness before storage.

[0088] The rate of change in battery thickness before and after storage was calculated using the following formula, and the average value for the five batteries was calculated to evaluate the storage characteristics of each battery. Thickness change rate (%) = 100 × (thickness after storage - thickness before storage) / thickness before storage

[0089] The evaluation results are shown in Table 1 together with the thickness of the positive electrode mixture layer in the positive electrode, Rs, ρv, and Rs / (ρv×d). In Table 1, the evaluation results for low-temperature load characteristics and 85°C storage characteristics are all shown as relative values, with the value for Example 1 being set at 100.

[0090] [Table 1]

[0091] As shown in Table 1, the battery of Example 1, which had a positive electrode with a positive electrode mixture layer thickness of 35 μm or more and less than 58 μm and an appropriate value of Rs / (ρv×d), achieved good results in both the low-temperature load characteristic evaluation and the 85°C storage characteristic evaluation, compared to the batteries of Comparative Examples 1 and 2, which used positive electrodes with inappropriate values ​​of Rs / (ρv×d), and thus achieved a high level of both load characteristic and storage characteristic.

[0092] Example 2 A positive electrode was produced in the same manner as in Example 1, except that the thickness of the positive electrode mixture layer on each side of the current collector was set to 46 μm.

[0093] A composite (negative electrode active material) in which the surface of SiO was coated with a carbon material (the amount of carbon material was 10 parts by mass per 100 parts by mass of SiO), graphite (negative electrode active material), CMC (binder), and SBR (binder) were mixed in a mass ratio of 3:93:2:2 and dispersed in water to prepare a paste containing a negative electrode mixture. Then, a negative electrode having a negative electrode mixture layer with a thickness of 46 μm per side of the current collector on both sides of the current collector was fabricated in the same manner as in Example 1, except that this paste containing a negative electrode mixture was used. A nonaqueous electrolyte secondary battery was fabricated in the same manner as in Example 1, except that the above-mentioned positive electrode and this negative electrode were used.

[0094] Comparative Example 3 A positive electrode was produced in the same manner as in Example 2 except that the same positive electrode mixture-containing slurry as used in Comparative Example 1 was used, and a nonaqueous electrolyte secondary battery was produced in the same manner as in Example 2 except that this positive electrode was used.

[0095] Comparative Example 4 A positive electrode was prepared in the same manner as in Example 2, except that the drying conditions for the coating film of the positive electrode mixture-containing slurry were the same as in Comparative Example 2. A nonaqueous electrolyte secondary battery was prepared in the same manner as in Example 2, except that this positive electrode was used.

[0096] For the nonaqueous electrolyte secondary batteries of Example 2 and Comparative Examples 3 and 4, low-temperature load characteristics and 85°C storage characteristics were evaluated using the same methods as for the battery of Example 1. These evaluation results are shown in Table 2 together with the thickness of the positive electrode mixture layer in the positive electrode, Rs, ρv, and Rs / (ρv×d). Note that in Table 2, the results of the low-temperature load characteristics evaluation and the 85°C storage characteristics evaluation are all shown as relative values ​​when the value for Example 2 is set to 100.

[0097] [Table 2]

[0098] As shown in Table 2, the battery of Example 2, which had a positive electrode with a positive electrode mixture layer thickness of 35 μm or more and less than 58 μm and an appropriate value of Rs / (ρv×d), achieved good results in both the low-temperature load characteristic evaluation and the 85°C storage characteristic evaluation, compared to the batteries of Comparative Examples 3 and 4, which used positive electrodes with inappropriate values ​​of Rs / (ρv×d), and thus achieved a high level of both load characteristic and storage characteristic.

[0099] Example 3 <Preparation of positive electrode> Li 1.01 Co 0.98 Mg 0.01 Al 0.01 O2 (positive electrode active material), acetylene black (conductive additive), and PVDF (binder) were mixed in a mass ratio of 97:1.9:1.1 and dispersed in NMP to prepare a positive electrode mixture-containing slurry (solid concentration excluding the solvent: 80 mass%).

[0100] This positive electrode mixture-containing slurry was intermittently applied to one side of a 10 μm-thick aluminum foil serving as a current collector. A drying furnace with three dryers was used, with the most upstream dryer 1 set to 110 °C, the middle dryer 2 set to 105 °C, and the most downstream dryer 3 set to 110 °C. A positive electrode mixture layer was formed by drying. The same procedure was then performed on the other side of the aluminum foil to form a positive electrode mixture layer on both sides of the aluminum foil. After drying, the aluminum foil was calendered to adjust the thickness of the positive electrode mixture layer to a total thickness of 116 μm. This was then cut to produce a long positive electrode. Furthermore, aluminum leads for extracting current were welded to the exposed portions of the aluminum foil to obtain a lead-attached positive electrode. The thickness of the positive electrode mixture layer in the resulting positive electrode was 53 μm per side of the current collector.

[0101] <Preparation of negative electrode> Graphite (negative electrode active material), CMC (binder), and SBR (binder) were mixed in a mass ratio of 96:2:2 and dispersed in water to prepare a paste containing a negative electrode mixture.

[0102] This negative electrode mixture-containing paste was intermittently applied to both sides of a 10 μm-thick copper foil current collector, dried, and then calendered to adjust the thickness of the negative electrode mixture layer to a total thickness of 148 μm. This was cut to prepare a long negative electrode. Furthermore, nickel leads for extracting current were welded to the exposed portions of the copper foil to obtain a lead-attached negative electrode. The thickness of the negative electrode mixture layer in the obtained negative electrode was 69 μm per side of the current collector.

[0103] A non-aqueous electrolyte secondary battery was fabricated in the same manner as in Example 1, except that the above positive electrode and negative electrode were used.

[0104] Example 4 A positive electrode was produced in the same manner as in Example 3, except that the coating film of the positive electrode mixture-containing slurry was dried using a drying furnace having three dryers, with the most upstream dryer 1 set to 110°C, the intermediate dryer 2 set to 110°C, and the most downstream dryer 3 set to 110°C. A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 3, except that this positive electrode was used.

[0105] Comparative Example 5 A positive electrode mixture containing a positive electrode active material, a conductive additive, and a binder mixed in a mass ratio of 96.5:2.4:1.1 was used, and a positive electrode mixture-containing slurry was prepared in the same manner as in Example 3, except that the solid content concentration was set to 78 mass %, and a positive electrode was fabricated in the same manner as in Example 4, except that this positive electrode mixture-containing slurry was used. Then, a nonaqueous electrolyte secondary battery was fabricated in the same manner as in Example 3, except that this positive electrode was used.

[0106] Comparative Example 6 A positive electrode was produced in the same manner as in Example 3, except that the coating film of the positive electrode mixture-containing slurry was dried using a drying furnace having three dryers, with the most upstream dryer 1 set to 105°C, the intermediate dryer 2 set to 110°C, and the most downstream dryer 3 set to 110°C. A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 3, except that this positive electrode was used.

[0107] For the nonaqueous electrolyte secondary batteries of Examples 3 and 4 and Comparative Examples 5 and 6, low-temperature load characteristics and 85°C storage characteristics were evaluated in the same manner as for the battery of Example 1, except that the end-of-charge voltage was changed to 4.4 V. These evaluation results are shown in Table 3 together with the thickness of the positive electrode mixture layer in the positive electrode, Rs, ρv, and Rs / (ρv×d). Note that in Table 3, the results of the low-temperature load characteristics evaluation and the 85°C storage characteristics evaluation are all shown as relative values ​​when the value for Example 3 is set to 100.

[0108] [Table 3]

[0109] As shown in Table 3, the batteries of Examples 3 and 4, which had a positive electrode with a positive electrode mixture layer thickness of 35 μm or more and less than 58 μm and a positive electrode with an appropriate Rs / (ρv×d) value, achieved good results in both the low-temperature load characteristic evaluation and the 85°C storage characteristic evaluation, compared to the batteries of Comparative Examples 5 and 6, which used positive electrodes with inappropriate Rs / (ρv×d) values, and thus achieved a high level of both load characteristic and storage characteristic.

[0110] Example 5 A nonaqueous electrolyte secondary battery was fabricated in the same manner as in Example 1, except that the negative electrode precursor was changed to an 80 μm Al foil. In the battery of Example 5, Li ions migrated from the positive electrode to Al on the negative electrode side by initial charging, resulting in a negative electrode containing a Li-Al alloy.

[0111] Comparative Example 7 A non-aqueous electrolyte secondary battery was fabricated in the same manner as in Example 5, except that the same positive electrode as that fabricated in Comparative Example 1 was used.

[0112] Comparative Example 8 A nonaqueous electrolyte secondary battery was fabricated in the same manner as in Example 5, except that the same positive electrode as that fabricated in Comparative Example 2 was used.

[0113] For the nonaqueous electrolyte secondary batteries of Example 5 and Comparative Examples 7 and 8, low-temperature load characteristics and 85°C storage characteristics were evaluated using the same methods as for the battery of Example 1. These evaluation results are shown in Table 4 together with the thickness of the positive electrode mixture layer in the positive electrode, Rs, ρv, and Rs / (ρv×d). In Table 4, the low-temperature load characteristics evaluation results and 85°C storage characteristics evaluation results are all shown as relative values ​​when the value for Example 5 is set to 100.

[0114] [Table 4]

[0115] As shown in Table 4, the battery of Example 5, which had a positive electrode with a positive electrode mixture layer thickness of 35 μm or more and less than 58 μm and an appropriate value of Rs / (ρv×d), achieved good results in both the low-temperature load characteristic evaluation and the 85°C storage characteristic evaluation, compared to the batteries of Comparative Examples 7 and 8, which used positive electrodes with inappropriate values ​​of Rs / (ρv×d), and thus achieved a high level of both load characteristic and storage characteristic.

[0116] Example 6 <Creating the positive electrode> Li 1.01 Co 0.98 Mg 0.01 Al 0.01 O2 and Li 1.01 Ni 0.86 Co 0.15 Al 0.04 A positive electrode active material prepared by mixing acetylene black (conductive additive), graphite (conductive additive), and PVDF (binder) in a mass ratio of 97.3:1.2:0.3:1.2 was mixed with acetylene black and O2 in a mass ratio of 85:15, and the mixture was dispersed in NMP to prepare a positive electrode mixture-containing slurry (solid concentration excluding the solvent: 79 mass%).

[0117] This positive electrode mixture-containing slurry was intermittently applied to one side of a 15 μm-thick aluminum foil serving as a current collector. A drying furnace with three dryers was used, with the most upstream dryer 1 set to 120 °C, the middle dryer 2 set to 110 °C, and the most downstream dryer 3 set to 120 °C. A positive electrode mixture layer was formed by drying. The same procedure was then performed on the other side of the aluminum foil to form a positive electrode mixture layer on both sides of the aluminum foil. After drying, the aluminum foil was calendered to adjust the thickness of the positive electrode mixture layer to a total thickness of 135 μm. This was then cut to produce a long positive electrode. Furthermore, aluminum leads for extracting current were welded to the exposed portions of the aluminum foil to obtain a lead-attached positive electrode. The thickness of the positive electrode mixture layer in the resulting positive electrode was 60 μm per side of the current collector.

[0118] <Preparation of negative electrode> The negative electrode mixture-containing paste prepared in the same manner as in Example 1 was intermittently applied to both sides of a 10 μm-thick copper foil serving as a current collector, dried, and then calendered to adjust the thickness of the negative electrode mixture layer to a total thickness of 146 μm. This was cut to prepare a long negative electrode. Furthermore, nickel lead pieces for extracting current were welded to the exposed portions of the copper foil to obtain a lead-attached negative electrode. The thickness of the negative electrode mixture layer in the obtained negative electrode was 68 μm per side of the current collector.

[0119] A non-aqueous electrolyte secondary battery was fabricated in the same manner as in Example 1, except that the above positive electrode and negative electrode were used.

[0120] Example 7 A positive electrode was fabricated in the same manner as in Example 6, except that the coating of the positive electrode mixture-containing slurry was dried using a drying furnace having three dryers, with the most upstream dryer 1 set to 115°C, the middle dryer 2 set to 110°C, and the most downstream dryer 3 set to 120°C, and the thickness of the positive electrode mixture layer in the positive electrode was 61 μm per side of the current collector. Then, a nonaqueous electrolyte secondary battery was fabricated in the same manner as in Example 6, except that this positive electrode was used.

[0121] Example 8 A positive electrode was fabricated in the same manner as in Example 6, except that the coating of the positive electrode mixture-containing slurry was dried using a drying furnace having three dryers, with the most upstream dryer 1 set to 110°C, the middle dryer 2 set to 110°C, and the most downstream dryer 3 set to 120°C, and the thickness of the positive electrode mixture layer in the positive electrode was 61 μm per side of the current collector. Then, a nonaqueous electrolyte secondary battery was fabricated in the same manner as in Example 6, except that this positive electrode was used.

[0122] Example 9 A positive electrode was fabricated in the same manner as in Example 6, except that the coating of the positive electrode mixture-containing slurry was dried using a drying furnace having three dryers, with the most upstream dryer 1 set to 110°C, the middle dryer 2 set to 115°C, and the most downstream dryer 3 set to 120°C, and the thickness of the positive electrode mixture layer in the positive electrode was 61 μm per side of the current collector. A nonaqueous electrolyte secondary battery was then fabricated in the same manner as in Example 6, except that this positive electrode was used.

[0123] Example 10 A positive electrode was fabricated in the same manner as in Example 6, except that the coating of the positive electrode mixture-containing slurry was dried using a drying furnace having three dryers, with the most upstream dryer 1 set to 105°C, the middle dryer 2 set to 115°C, and the most downstream dryer 3 set to 120°C, and the thickness of the positive electrode mixture layer in the positive electrode was 61 μm per side of the current collector. Then, a nonaqueous electrolyte secondary battery was fabricated in the same manner as in Example 6, except that this positive electrode was used.

[0124] Comparative Example 9 A positive electrode was produced in the same manner as in Example 6, except that the coating film of the positive electrode mixture-containing slurry was dried using a drying furnace having three dryers, with the most upstream dryer 1 set to 105°C, the intermediate dryer 2 set to 120°C, and the most downstream dryer 3 set to 120°C. A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 6, except that this positive electrode was used.

[0125] Comparative Example 10 A positive electrode mixture-containing slurry prepared in the same manner as in Example 6 was used, except that the ratio of the positive electrode active material, acetylene black (conductive additive), graphite (conductive additive), and PVDF (binder) was changed to a mass ratio of 96.8:1.7:0.3:1.2, and the solids concentration excluding the solvent was changed to 76 mass%. The coating film of the positive electrode mixture-containing slurry was dried using a drying furnace having three dryers, with the most upstream dryer 1 set to 105 ° C., the middle dryer 2 set to 115 ° C., and the most downstream dryer 3 set to 120 ° C. A positive electrode was produced in the same manner as in Example 6. Then, a nonaqueous electrolyte secondary battery was produced in the same manner as in Example 6, except that this positive electrode was used.

[0126] Example 11 A composition for forming an undercoat layer was prepared by dispersing vapor-grown carbon fiber (conductive additive) and chitosan (binder) in a mass ratio of 30:70 in NMP. The composition was applied to both sides of the same current collector (aluminum foil) as used in Example 1 and dried to form an undercoat layer with a thickness of 0.5 μm on each side of the current collector.

[0127] A positive electrode was fabricated in the same manner as in Example 6, except that the current collector on which the undercoat layer was formed was used, and the coating of the positive electrode mixture-containing slurry was dried using a drying furnace having three dryers, with the most upstream dryer 1 set to 110°C, the middle dryer 2 set to 115°C, and the most downstream dryer 3 set to 120°C. A nonaqueous electrolyte secondary battery was fabricated in the same manner as in Example 6, except that this positive electrode was used. The composition of the positive electrode mixture layer, including the undercoat layer, was 97.25% by mass of positive electrode active material, 1.55% by mass of conductive additive, and 1.20% by mass of binder.

[0128] Example 12 A positive electrode having an undercoat layer was produced in the same manner as in Example 11, except that the coating film of the positive electrode mixture-containing slurry was dried using a drying furnace having three dryers, with the most upstream dryer 1 set to 115°C, the intermediate dryer 2 set to 110°C, and the most downstream dryer 3 set to 120°C. A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 11, except that this positive electrode was used.

[0129] Example 13 A positive electrode having an undercoat layer was produced in the same manner as in Example 11, except that the coating film of the positive electrode mixture-containing slurry was dried using a drying furnace having three dryers, with the most upstream dryer 1 set to 120°C, the intermediate dryer 2 set to 110°C, and the most downstream dryer 3 set to 120°C. A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 11, except that this positive electrode was used.

[0130] Comparative Example 11 A positive electrode having an undercoat layer was produced in the same manner as in Example 11 except that the coating film of the positive electrode mixture-containing slurry was dried using a drying furnace having three dryers, with the most upstream dryer 1 set to 120°C, the intermediate dryer 2 set to 115°C, and the most downstream dryer 3 set to 120°C. A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 11 except that this positive electrode was used.

[0131] For the nonaqueous electrolyte secondary batteries of Examples 6 to 13 and Comparative Examples 9 to 11, low-temperature load characteristics and 85°C storage characteristics were evaluated using the same methods as for the battery of Example 1. These evaluation results are shown in Table 5 together with the thickness of the positive electrode mixture layer in the positive electrode, Rs, ρv, and Rs / (ρv×d). Note that in Table 5, the results of the low-temperature load characteristics evaluation and the 85°C storage characteristics evaluation are all shown as relative values ​​when the value for Example 6 is set to 100.

[0132] [Table 5]

[0133] As shown in Table 5, the batteries of Examples 6 to 13, which had a positive electrode mixture layer thickness of 58 μm or more and less than 68 μm and a positive electrode with an appropriate Rs / (ρv×d) value, achieved good results in both the low-temperature load characteristic evaluation and the 85°C storage characteristic evaluation, compared to the batteries of Comparative Examples 9 to 11, which used positive electrodes with inappropriate Rs / (ρv×d) values, and were able to achieve a high level of both load characteristic and storage characteristic.

[0134] Example 14 The coating film of the positive electrode mixture-containing slurry was dried using a drying furnace having three dryers, with the most upstream dryer 1 set to 115°C, the middle dryer 2 set to 110°C, and the most downstream dryer 3 set to 120°C, and the thickness of the positive electrode mixture layer was adjusted so that the total thickness of the positive electrode was 145 μm. A positive electrode was produced in the same manner as in Example 6. The thickness of the positive electrode mixture layer in the obtained positive electrode was 65 μm per side of the current collector.

[0135] A negative electrode was produced in the same manner as in Example 6, except that the thickness of the negative electrode mixture layer was adjusted so that the total thickness of the negative electrode was 154 μm. The thickness of the negative electrode mixture layer in the obtained negative electrode was 72 μm per side of the current collector.

[0136] A non-aqueous electrolyte secondary battery was fabricated in the same manner as in Example 1, except that the above positive electrode and negative electrode were used.

[0137] Example 15 A positive electrode was fabricated in the same manner as in Example 6, except that the coating of the positive electrode mixture-containing slurry was dried using a drying furnace having three dryers, with the most upstream dryer 1 set to 110°C, the middle dryer 2 set to 110°C, and the most downstream dryer 3 set to 120°C, and the thickness of the positive electrode mixture layer in the positive electrode was 64 μm per side of the current collector.A nonaqueous electrolyte secondary battery was fabricated in the same manner as in Example 14, except that this positive electrode was used.

[0138] Example 16 A positive electrode was fabricated in the same manner as in Example 6, except that the coating of the positive electrode mixture-containing slurry was dried using a drying furnace having three dryers, with the most upstream dryer 1 set to 110°C, the middle dryer 2 set to 115°C, and the most downstream dryer 3 set to 120°C, and the thickness of the positive electrode mixture layer in the positive electrode was 64 μm per side of the current collector.A nonaqueous electrolyte secondary battery was fabricated in the same manner as in Example 14, except that this positive electrode was used.

[0139] Example 17 A positive electrode was fabricated in the same manner as in Example 6, except that the coating of the positive electrode mixture-containing slurry was dried using a drying furnace having three dryers, with the most upstream dryer 1 set to 105°C, the middle dryer 2 set to 115°C, and the most downstream dryer 3 set to 120°C, and the thickness of the positive electrode mixture layer on the positive electrode was 64 μm per side of the current collector.A nonaqueous electrolyte secondary battery was fabricated in the same manner as in Example 14, except that this positive electrode was used.

[0140] Example 18 A positive electrode was fabricated in the same manner as in Example 6, except that the coating of the positive electrode mixture-containing slurry was dried using a drying furnace having three dryers, with the most upstream dryer 1 set to 105°C, the middle dryer 2 set to 110°C, and the most downstream dryer 3 set to 120°C, and the thickness of the positive electrode mixture layer in the positive electrode was 64 μm per side of the current collector.A nonaqueous electrolyte secondary battery was fabricated in the same manner as in Example 14, except that this positive electrode was used.

[0141] Comparative Example 12 A positive electrode was fabricated in the same manner as in Example 6, except that the coating of the positive electrode mixture-containing slurry was dried using a drying furnace having three dryers, with the most upstream dryer 1 set to 110°C, the middle dryer 2 set to 120°C, and the most downstream dryer 3 set to 120°C, and the thickness of the positive electrode mixture layer on the positive electrode was 64 μm per side of the current collector.A nonaqueous electrolyte secondary battery was fabricated in the same manner as in Example 14, except that this positive electrode was used.

[0142] Comparative Example 13 A positive electrode was fabricated in the same manner as in Example 14, except that the same positive electrode mixture-containing slurry as prepared in Comparative Example 10 was used, and the coating film of the positive electrode mixture-containing slurry was dried using a drying furnace having three dryers, with the most upstream dryer 1 set to 110°C, the middle dryer 2 set to 115°C, and the most downstream dryer 3 set to 120°C. Then, a nonaqueous electrolyte secondary battery was fabricated in the same manner as in Example 14, except that this positive electrode was used.

[0143] For the nonaqueous electrolyte secondary batteries of Examples 14 to 18 and Comparative Examples 12 and 13, low-temperature load characteristics and 85°C storage characteristics were evaluated using the same methods as for the battery of Example 1. These evaluation results are shown in Table 6 together with the thickness of the positive electrode mixture layer in the positive electrode, Rs, ρv, and Rs / (ρv×d). Note that in Table 6, the results of the low-temperature load characteristics evaluation and the 85°C storage characteristics evaluation are all shown as relative values ​​when the value for Example 14 is set to 100.

[0144] [Table 6]

[0145] As shown in Table 6, the batteries of Examples 14 to 18, which had a positive electrode mixture layer thickness of 58 μm or more and less than 68 μm and a positive electrode with an appropriate Rs / (ρv×d) value, achieved good results in both the low-temperature load characteristic evaluation and the 85°C storage characteristic evaluation, compared to the batteries of Comparative Examples 12 and 13, which used positive electrodes with inappropriate Rs / (ρv×d) values, and achieved a high level of both load characteristic and storage characteristic.

[0146] Example 19 A positive electrode was produced in the same manner as in Example 1, except that the coating film of the positive electrode mixture-containing slurry was dried using a drying furnace having three dryers, with the most upstream dryer 1 set to 125°C, the middle dryer 2 set to 120°C, and the most downstream dryer 3 set to 125°C, and that the thickness of the positive electrode mixture layer in the positive electrode was 76 μm per side of the current collector.

[0147] Furthermore, a negative electrode was fabricated in the same manner as in Example 1, except that the thickness of the negative electrode mixture layer was set to 89 μm per surface of the current collector.

[0148] A non-aqueous electrolyte secondary battery was fabricated in the same manner as in Example 1, except that the above positive electrode and negative electrode were used.

[0149] Example 20 A positive electrode was prepared in the same manner as in Example 19, except that the coating film of the positive electrode mixture-containing slurry was dried using a drying furnace having three dryers, with the most upstream dryer 1 set to 120°C, the intermediate dryer 2 set to 120°C, and the most downstream dryer 3 set to 125°C. A nonaqueous electrolyte secondary battery was prepared in the same manner as in Example 19, except that this positive electrode was used.

[0150] Example 21 A positive electrode was prepared in the same manner as in Example 19, except that the coating film of the positive electrode mixture-containing slurry was dried using a drying furnace having three dryers, with the most upstream dryer 1 set to 115°C, the intermediate dryer 2 set to 120°C, and the most downstream dryer 3 set to 125°C. A nonaqueous electrolyte secondary battery was prepared in the same manner as in Example 19, except that this positive electrode was used.

[0151] Example 22 A positive electrode was produced in the same manner as in Example 19, except that the coating film of the positive electrode mixture-containing slurry was dried using a drying furnace having three dryers, with the most upstream dryer 1 set to 105°C, the intermediate dryer 2 set to 120°C, and the most downstream dryer 3 set to 125°C. A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 19, except that this positive electrode was used.

[0152] Example 23 A positive electrode was produced in the same manner as in Example 19, except that the coating film of the positive electrode mixture-containing slurry was dried using a drying furnace having three dryers, with the most upstream dryer 1 set to 100°C, the intermediate dryer 2 set to 115°C, and the most downstream dryer 3 set to 125°C. A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 19, except that this positive electrode was used.

[0153] Example 24 A positive electrode was produced in the same manner as in Example 19, except that a positive electrode mixture-containing slurry prepared in the same manner as in Example 1 was used, except that the solid content concentration was set to 80% by mass, and the coating of the positive electrode mixture-containing slurry was dried using a drying furnace having three dryers, with the most upstream dryer 1 set to 125°C, the middle dryer 2 set to 125°C, and the most downstream dryer 3 set to 125°C. Then, a nonaqueous electrolyte secondary battery was produced in the same manner as in Example 19, except that this positive electrode was used.

[0154] Comparative Example 14 A positive electrode was fabricated in the same manner as in Example 19, except that the coating of the positive electrode mixture-containing slurry was dried using a drying furnace having three dryers, with the most upstream dryer 1 set to 100°C, the middle dryer 2 set to 110°C, and the most downstream dryer 3 set to 125°C, and the thickness of the positive electrode mixture layer in the positive electrode was set to 77 μm per side of the current collector.A nonaqueous electrolyte secondary battery was fabricated in the same manner as in Example 19, except that this positive electrode was used.

[0155] Comparative Example 15 A positive electrode was fabricated in the same manner as in Example 19, except that the same positive electrode mixture-containing slurry as prepared in Comparative Example 1 was used, the coating of the positive electrode mixture-containing slurry was dried using a drying furnace having three dryers, with the most upstream dryer 1 set to 115°C, the middle dryer 2 set to 120°C, and the most downstream dryer 3 set to 125°C, and the thickness of the positive electrode mixture layer in the positive electrode was 77 μm per side of the current collector. Then, a nonaqueous electrolyte secondary battery was fabricated in the same manner as in Example 19, except that this positive electrode was used.

[0156] For the nonaqueous electrolyte secondary batteries of Examples 19 to 24 and Comparative Examples 14 and 15, low-temperature load characteristics and 85°C storage characteristics were evaluated using the same methods as for the battery of Example 1. These evaluation results are shown in Table 7 together with the thickness of the positive electrode mixture layer in the positive electrode, Rs, ρv, and Rs / (ρv×d). In Table 7, the low-temperature load characteristics evaluation results and 85°C storage characteristics evaluation results are all shown as relative values ​​when the value for Example 19 is set to 100.

[0157] [Table 7]

[0158] As shown in Table 7, the batteries of Examples 19 to 24, which had a positive electrode mixture layer thickness of 68 μm or more and 80 μm or less and a positive electrode with an appropriate Rs / (ρv×d) value, achieved good results in both the low-temperature load characteristic evaluation and the 85°C storage characteristic evaluation, compared to the batteries of Comparative Examples 14 and 15, which used positive electrodes with inappropriate Rs / (ρv×d) values, and were able to achieve a high level of both load characteristic and storage characteristic.

[0159] Example 25 A positive electrode was produced in the same manner as in Example 1, except that the same positive electrode mixture-containing slurry prepared in Example 1 was used, and the coating film of the positive electrode mixture-containing slurry was dried using a drying furnace having three dryers, with the most upstream dryer 1 set to 125°C, the middle dryer 2 set to 120°C, and the most downstream dryer 3 set to 120°C, and the thickness of the positive electrode mixture layer in the positive electrode was 70 µm per side of the current collector.

[0160] A negative electrode was also produced in the same manner as in Example 1, except that the thickness of the negative electrode mixture layer was set to 81 μm per surface of the current collector.

[0161] A non-aqueous electrolyte secondary battery was fabricated in the same manner as in Example 1, except that the above positive electrode and negative electrode were used.

[0162] Example 26 A positive electrode was produced in the same manner as in Example 25, except that the coating film of the positive electrode mixture-containing slurry was dried using a drying furnace having three dryers, with the most upstream dryer 1 set to 120°C, the intermediate dryer 2 set to 115°C, and the most downstream dryer 3 set to 120°C. A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 25, except that this positive electrode was used.

[0163] Example 27 A positive electrode was produced in the same manner as in Example 25, except that the coating film of the positive electrode mixture-containing slurry was dried using a drying furnace having three dryers, with the most upstream dryer 1 set to 120°C, the intermediate dryer 2 set to 120°C, and the most downstream dryer 3 set to 120°C. A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 25, except that this positive electrode was used.

[0164] Example 28 A positive electrode was prepared in the same manner as in Example 1 except that the coating film of the positive electrode mixture-containing slurry was dried using a drying furnace having three dryers, with the most upstream dryer 1 set to 115°C, the middle dryer 2 set to 120°C, and the most downstream dryer 3 set to 120°C, and the thickness of the positive electrode mixture layer was set to 69 μm per side of the current collector. A nonaqueous electrolyte secondary battery was prepared in the same manner as in Example 19 except that this positive electrode was used.

[0165] Example 29 A positive electrode was produced in the same manner as in Example 25, except that the coating film of the positive electrode mixture-containing slurry was dried using a drying furnace having three dryers, with the most upstream dryer 1 set to 115°C, the intermediate dryer 2 set to 115°C, and the most downstream dryer 3 set to 120°C. Except for this, a nonaqueous electrolyte secondary battery was produced in the same manner as in Example 25, except that this positive electrode was used.

[0166] Comparative Example 16 A positive electrode was produced in the same manner as in Example 25, except that the coating film of the positive electrode mixture-containing slurry was dried using a drying furnace having three dryers, with the most upstream dryer 1 set to 110°C, the intermediate dryer 2 set to 115°C, and the most downstream dryer 3 set to 120°C. Except for this, a nonaqueous electrolyte secondary battery was produced in the same manner as in Example 25, except that this positive electrode was used.

[0167] Comparative Example 17 A positive electrode was produced in the same manner as in Example 25, except that the same positive electrode mixture-containing slurry as prepared in Comparative Example 1 was used, and the coating film of the positive electrode mixture-containing slurry was dried using a drying furnace having three dryers, with the most upstream dryer 1 set to 110°C, the middle dryer 2 set to 110°C, and the most downstream dryer 3 set to 125°C. Except for this, a nonaqueous electrolyte secondary battery was produced in the same manner as in Example 25.

[0168] Example 30 A current collector having an undercoat layer formed on both sides thereof, prepared in the same manner as in Example 11, was used, and the coating film of the positive electrode mixture-containing slurry was dried using a drying furnace having three dryers, with the most upstream dryer 1 set to 115°C, the middle dryer 2 set to 120°C, and the most downstream dryer 3 set to 120°C. A positive electrode having an undercoat layer was prepared in the same manner as in Example 25, except that this positive electrode was used. A nonaqueous electrolyte secondary battery was prepared in the same manner as in Example 25. The composition of the positive electrode mixture layer, including the undercoat layer, was 93.95% by mass of positive electrode active material, 4.05% by mass of conductive additive, and 2.0% by mass of binder.

[0169] Example 31 A positive electrode having an undercoat layer was produced in the same manner as in Example 30, except that the coating film of the positive electrode mixture-containing slurry was dried using a drying furnace having three dryers, with the most upstream dryer 1 set to 120°C, the middle dryer 2 set to 120°C, and the most downstream dryer 3 set to 120°C. A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 30, except that this positive electrode was used.

[0170] Example 32 A positive electrode having an undercoat layer was produced in the same manner as in Example 30, except that the coating film of the positive electrode mixture-containing slurry was dried using a drying furnace having three dryers, with the most upstream dryer 1 set to 120°C, the intermediate dryer 2 set to 115°C, and the most downstream dryer 3 set to 120°C. A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 30, except that this positive electrode was used.

[0171] Comparative Example 18 A positive electrode having an undercoat layer was produced in the same manner as in Example 30, except that the coating film of the positive electrode mixture-containing slurry was dried using a drying furnace having three dryers, with the most upstream dryer 1 set to 125°C, the middle dryer 2 set to 120°C, and the most downstream dryer 3 set to 120°C. A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 30, except that this positive electrode was used.

[0172] For the nonaqueous electrolyte secondary batteries of Examples 25 to 32 and Comparative Examples 16 to 18, low-temperature load characteristics and 85°C storage characteristics were evaluated using the same methods as for the battery of Example 1. These evaluation results are shown in Table 8 together with the thickness of the positive electrode mixture layer in the positive electrode, Rs, ρv, and Rs / (ρv×d). Note that in Table 8, the results of the low-temperature load characteristics evaluation and the 85°C storage characteristics evaluation are all shown as relative values ​​when the value for Example 25 is set to 100.

[0173] [Table 8]

[0174] As shown in Table 8, the batteries of Examples 25 to 32, which had a positive electrode mixture layer thickness of 68 μm or more and 80 μm or less and a positive electrode with an appropriate Rs / (ρv×d) value, achieved good results in both the low-temperature load characteristic evaluation and the 85°C storage characteristic evaluation, compared to the batteries of Comparative Examples 16 to 18, which used positive electrodes with inappropriate Rs / (ρv×d) values, and were able to achieve a high level of both load characteristic and storage characteristic.

[0175] The present invention can be implemented in other forms without departing from the spirit of the present invention. The embodiments disclosed in this application are merely examples, and the present invention is not limited to these embodiments. The scope of the present invention shall be interpreted in accordance with the appended claims rather than the description in the above specification, and all modifications within the scope of the claims are included in the scope of the claims. [Industrial Applicability]

[0176] As described above, the nonaqueous electrolyte secondary battery of the present invention has excellent load characteristics and storage characteristics, and by taking advantage of these characteristics, it can be preferably used in applications requiring particularly large current discharge, and can also be used in the same applications as those in which conventionally known nonaqueous electrolyte secondary batteries are used. Furthermore, the positive electrode for a nonaqueous electrolyte secondary battery of the present invention can constitute the nonaqueous electrolyte secondary battery of the present invention. [Explanation of symbols]

[0177] 1 Nonaqueous electrolyte secondary battery 2 Electrode body 3 Positive external terminal 4 Negative external terminal 5 Laminated film exterior

Claims

1. A positive electrode for a non-aqueous electrolyte secondary battery, comprising a positive electrode mixture layer containing a positive electrode active material and a conductive additive on one or both sides of a current collector, the thickness of the positive electrode mixture layer per one surface of the current collector is 35 μm or more and less than 58 μm, The interface resistance between the positive electrode mixture layer and the current collector is Rs (Ωcm ２ a volume resistivity of the positive electrode mixture layer is ρv (Ωcm), and a thickness of the positive electrode mixture layer is d (cm), where Rs / (ρv×d) is 1.0±0.

2.

2. 2. The positive electrode for a non-aqueous electrolyte secondary battery according to claim 1, wherein the thickness of the positive electrode mixture layer per one surface of the current collector is 38 μm or more and less than 58 μm.

3. A positive electrode for a non-aqueous electrolyte secondary battery, comprising a positive electrode mixture layer containing a positive electrode active material and a conductive additive on one or both sides of a current collector, the thickness of the positive electrode mixture layer per one surface of the current collector is 58 μm or more and less than 68 μm, The interface resistance between the positive electrode mixture layer and the current collector is Rs (Ωcm ２ a volume resistivity of the positive electrode mixture layer is ρv (Ωcm), and a thickness of the positive electrode mixture layer is d (cm), where Rs / (ρv×d) is 0.55 to 1.

6.

4. 4. The positive electrode for a non-aqueous electrolyte secondary battery according to claim 3, wherein the Rs / (ρv×d) is 0.8 to 1.

26.

5. A positive electrode for a non-aqueous electrolyte secondary battery, comprising a positive electrode mixture layer containing a positive electrode active material and a conductive additive on one or both sides of a current collector, the thickness of the positive electrode mixture layer per one surface of the current collector is 68 μm or more and 80 μm or less, The interface resistance between the positive electrode mixture layer and the current collector is Rs (Ωcm ２ a volume resistivity of the positive electrode mixture layer is ρv (Ωcm), and a thickness of the positive electrode mixture layer is d (cm), where Rs / (ρv×d) is 0.55 to 10.

6. 6. The positive electrode for a non-aqueous electrolyte secondary battery according to claim 5, wherein Rs / (ρv×d) is 0.55 to 3.

0.

7. 6. The positive electrode for a non-aqueous electrolyte secondary battery according to claim 5, wherein Rs / (ρv×d) is 0.7 to 1.

7.

8. A non-aqueous electrolyte secondary battery having a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and a non-aqueous electrolyte, A non-aqueous electrolyte secondary battery, wherein the positive electrode is the positive electrode for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 7.

9. 9. The nonaqueous electrolyte secondary battery according to claim 8, wherein the negative electrode comprises, in a charged state, an aluminum foil or an aluminum alloy foil and a Li-Al alloy formed by a reaction between the aluminum foil and Li ions released from the positive electrode.

10. When forming a positive electrode mixture layer containing a positive electrode active material and a conductive additive on one or both surfaces of a current collector, The thickness of the positive electrode mixture layer per one surface of the current collector is 35 μm or more and less than 58 μm, The interface resistance between the positive electrode mixture layer and the current collector is Rs (Ωcm ２ a volume resistivity of the positive electrode mixture layer is ρv (Ωcm), and a thickness of the positive electrode mixture layer is d (cm), the ratio Rs / (ρv×d) being adjusted to 1.0±0.

2.

11. When forming a positive electrode mixture layer containing a positive electrode active material and a conductive additive on one or both surfaces of a current collector, The thickness of the positive electrode mixture layer per one surface of the current collector is set to 58 μm or more and less than 68 μm, The interface resistance between the positive electrode mixture layer and the current collector is Rs (Ωcm ２ a volume resistivity of the positive electrode mixture layer is ρv (Ωcm), and a thickness of the positive electrode mixture layer is d (cm), the ratio Rs / (ρv×d) being adjusted to 0.55 to 1.

6.

12. When forming a positive electrode mixture layer containing a positive electrode active material and a conductive additive on one or both surfaces of a current collector, The thickness of the positive electrode mixture layer per one surface of the current collector is set to 68 μm or more and 80 μm or less, The interface resistance between the positive electrode mixture layer and the current collector is Rs (Ωcm ２ a volume resistivity of the positive electrode mixture layer is ρv (Ωcm), and a thickness of the positive electrode mixture layer is d (cm), the ratio Rs / (ρv×d) being adjusted to 0.55 to 10.

13. A method for producing a non-aqueous electrolyte secondary battery, comprising: a positive electrode; a negative electrode; a separator interposed between the positive electrode and the negative electrode; and a non-aqueous electrolyte, wherein the positive electrode is a positive electrode for a non-aqueous electrolyte secondary battery produced by the method for producing a positive electrode for a non-aqueous electrolyte secondary battery according to any one of claims 10 to 12.

14. A method for inspecting a positive electrode for a non-aqueous electrolyte secondary battery, the positive electrode having a positive electrode mixture layer containing a positive electrode active material and a conductive additive on one or both sides of a current collector, comprising: For the positive electrode for a non-aqueous electrolyte secondary battery, the interface resistance Rs (Ωcm) between the positive electrode mixture layer and the current collector ２ ), a volume resistivity ρv (Ωcm) of the positive electrode mixture layer, and a thickness d (cm) of the positive electrode mixture layer, and calculate a value of Rs / (ρv×d); and selecting nonaqueous electrolyte secondary batteries to which the positive electrode for nonaqueous electrolyte secondary batteries is applied based on the value of Rs / (ρv×d).

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