Non-aqueous electrolyte secondary batteries

Abstract

This non-aqueous electrolyte secondary battery comprises an electrode body, an exterior body which has a prescribed exterior shape and which houses the electrode body, and a sealing body which seals an opening at the upper end of the exterior body. A positive electrode included in the electrode body includes a positive electrode current collector and a positive electrode mixture layer which is formed on the surface of the positive electrode current collector and which includes a positive electrode active material and a conductive agent. The positive electrode active material contains a lithium-containing complex oxide. The lithium-containing complex oxide has a layered rock salt structure, contains substantially no Co, and contains at least Ni and Mn. The Ni content in the lithium-containing complex oxide is not less than 70 mol% with respect to the total number of moles of metal elements excluding Li. The basis weight of the positive electrode mixture layer is not less than 250 g / m2. Three or more positive electrode leads are drawn out in the electrode body.

Description

[Technical Field]

[0001] The present disclosure relates to a non-aqueous electrolyte secondary battery. [Background technology]

[0002] In recent years, non-aqueous electrolyte secondary batteries have been widely used as high-output, high-capacity secondary batteries. These batteries include a positive electrode, a negative electrode, and a non-aqueous electrolyte, and are charged and discharged by transferring Li ions between the positive electrode and the negative electrode. Patent Document 1 discloses a secondary battery in which current collecting members are disposed above and below an electrode body having multiple protruding tabs, thereby improving the battery's output characteristics while reducing the cost of the current collecting members. Patent Document 1 also describes a lithium-containing composite oxide containing two or more elements selected from Co, Ni, and Mn as a positive electrode active material. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5747082 Summary of the Invention [Problem to be solved by the invention]

[0004] Patent Document 1 discloses a positive electrode active material containing Ni, Mn, and Co. One possible design is to increase the Ni content of the lithium-containing composite oxide contained in the positive electrode active material to obtain a high battery capacity, while decreasing the Co content to reduce manufacturing costs. However, since decreasing the Co content decreases electronic conductivity, secondary batteries using high-Ni lithium-containing composite oxides that are substantially free of Co may experience increased battery resistance and reduced output characteristics. The technology in Patent Document 1 does not take into consideration the balancing of reduced battery resistance and reduced costs, and there is still room for improvement.

[0005] Therefore, an object of the present disclosure is to provide a nonaqueous electrolyte secondary battery that has improved output characteristics while suppressing costs. [Means for solving the problem]

[0006] A nonaqueous electrolyte secondary battery according to one embodiment of the present disclosure includes: an electrode assembly in which a strip-shaped positive electrode and a strip-shaped negative electrode are wound with a separator interposed therebetween; a cylindrical exterior body having an outer diameter of 25 mm or more and a bottom; and a sealing body that houses the electrode assembly and is connected to the negative electrode and seals the opening at the top end of the exterior body and is connected to the positive electrode. The positive electrode includes a positive electrode current collector and a positive electrode mixture layer that is formed on the surface of the positive electrode current collector and contains a positive electrode active material and a conductive agent. The positive electrode active material includes a lithium-containing composite oxide. The lithium-containing composite oxide has a layered rock salt structure and contains substantially no Co and at least Ni and Mn. The Ni content in the lithium-containing composite oxide is 70 mol % or more relative to the total number of moles of metal elements excluding Li. The positive electrode mixture layer has a basis weight of 250 g / m. 2 As described above, the electrode assembly is characterized in that three or more positive electrode leads are led out from the electrode assembly.

[0007] A nonaqueous electrolyte secondary battery according to one embodiment of the present disclosure includes: an electrode assembly in which a strip-shaped positive electrode and a strip-shaped negative electrode are wound with a separator interposed therebetween; a cylindrical exterior body having an outer diameter of 25 mm or more and a bottom; and a sealing body that houses the electrode assembly and is connected to the negative electrode and seals the opening at the top end of the exterior body and is connected to the positive electrode. The positive electrode includes a positive electrode current collector and a positive electrode mixture layer that is formed on the surface of the positive electrode current collector and contains a positive electrode active material and a conductive agent. The positive electrode active material includes a lithium-containing composite oxide. The lithium-containing composite oxide has a layered rock salt structure and contains substantially no Co and at least Ni and Mn. The Ni content in the lithium-containing composite oxide is 70 mol % or more relative to the total number of moles of metal elements excluding Li. The positive electrode mixture layer has a basis weight of 250 g / m. 2 As described above, the positive electrode protruding above the negative electrode and separator in the electrode assembly is connected to a positive electrode current collector, and the positive electrode current collector and the sealing body are connected by a positive electrode lead. [Effects of the Invention]

[0008] According to a nonaqueous electrolyte secondary battery according to one aspect of the present disclosure, both improved output characteristics and reduced costs can be achieved. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a longitudinal cross-sectional view of a nonaqueous electrolyte secondary battery according to an embodiment of the present invention; [Figure 2] 2 is a front view showing a positive electrode and a negative electrode constituting an electrode body provided in the nonaqueous electrolyte secondary battery of FIG. 1 in a developed state. [Figure 3] 1A and 1B are plan views showing the positions where positive electrode leads are arranged on the upper surface of the electrode body, where (a) shows an example where they are arranged in a substantially linear radial direction, and (b) shows an example where they are arranged at substantially equal angles. [Figure 4] FIG. 2 is a longitudinal cross-sectional view of a nonaqueous electrolyte secondary battery according to another embodiment. [Figure 5] 4 is a perspective view of an electrode assembly included in the nonaqueous electrolyte secondary battery of FIG. 3, showing the configuration of a positive electrode, a negative electrode, and a separator in a state in which the vicinity of the outer end of the roll is unrolled. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0010] The layered rock salt structure of the lithium-containing composite oxide contains a transition metal layer such as Ni, a Li layer, and an oxygen layer, and the charge / discharge reaction of the battery progresses as Li ions present in the Li layer reversibly enter and exit. In the lithium-containing composite oxide, if the Ni content is increased from the viewpoint of high capacity while the Co content is reduced from the viewpoint of cost reduction, the electronic conductivity of the lithium-containing composite oxide itself decreases, which may increase the resistance of the battery and deteriorate the output characteristics. As a result of extensive research, the present inventors have found that it is possible to achieve a battery with an outer diameter of 25 mm or more and a basis weight of 250 g / m2 of the positive electrode mixture layer while adjusting the composition of the lithium-containing composite oxide. 2It has been found that by connecting the positive electrode and the sealing member in a predetermined manner, it is possible to achieve both improved output characteristics and reduced costs. By adjusting the composition of the lithium-containing composite oxide, it is possible to improve the battery capacity while suppressing costs. Furthermore, by connecting the positive electrode and the sealing member in a predetermined manner, the output characteristics of the secondary battery are improved. Furthermore, when the outer diameter of the battery is 25 mm or more and the basis weight of the positive electrode mixture layer is 250 g / m 2 By doing so, it is possible to reduce the cost of the secondary battery having the above-described configuration. Here, the cost means the cost per unit battery capacity when manufacturing the secondary battery.

[0011] An example of an embodiment of a nonaqueous electrolyte secondary battery according to the present disclosure will be described in detail below with reference to FIGS. 1 to 3. In the following description, specific shapes, materials, numerical values, directions, etc. are examples for facilitating understanding of the present invention and can be appropriately changed according to the specifications of the nonaqueous electrolyte secondary battery. Furthermore, when multiple embodiments and modified examples are included in the following description, it is assumed from the beginning that their characteristic features will be used in appropriate combination. Furthermore, when the term "approximately" is used in this specification, it is used in the same sense as the term "roughly," and the requirement of "approximately" is met if the two or more are substantially the same.

[0012] FIG. 1 is a longitudinal cross-sectional view of a nonaqueous electrolyte secondary battery 10 according to an embodiment. The secondary battery 10 shown in FIG. 1 includes an electrode assembly 14 and an electrolyte (not shown) housed in an outer casing 15. The electrode assembly 14 has a wound structure in which a strip-shaped positive electrode 11 and a strip-shaped negative electrode 12 are wound with a separator 13 interposed therebetween. Examples of nonaqueous solvents (organic solvents) for the electrolyte include carbonates, lactones, ethers, ketones, and esters, and two or more of these solvents can be mixed. When two or more solvents are mixed, a mixed solvent containing a cyclic carbonate and a chain carbonate is preferably used. For example, cyclic carbonates include ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate (BC), and chain carbonates include dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC). The electrolyte salt of the electrolyte solution may be LiPF, LiBF, LiCF, SO, or a mixture thereof. The amount of electrolyte salt dissolved in the non-aqueous solvent may be, for example, 0.5 mol / L to 2.0 mol / L. For ease of explanation, the following description will refer to the sealing body 16 side as "top" and the bottom side of the exterior body 15 as "bottom."

[0013] The sealing body 16 seals the opening at the top end of the exterior body 15, sealing the interior of the secondary battery 10. Insulating plates 17 and 18 are provided above and below the electrode body 14. The positive electrode lead 19 extends vertically through a through-hole in the insulating plate 17 and connects the filter 22, which is the bottom plate of the sealing body 16, to the positive electrode 11 included in the electrode body 14. This connects the positive electrode 11 to the sealing body 16, and in the secondary battery 10, the cap 26, which is the top plate of the sealing body 16 and is electrically connected to the filter 22, serves as the positive electrode terminal. The positive electrode lead 19 is, for example, an aluminum lead. On the other hand, the negative electrode lead 20 extends through a through-hole in the insulating plate 18 to the bottom side of the exterior body 15 and is welded to the inner bottom surface of the exterior body 15. This connects the negative electrode 12 to the exterior body 15, and in the secondary battery 10, the exterior body 15 serves as the negative electrode terminal. The negative electrode lead 20 is, for example, a nickel lead.

[0014] Three positive electrode leads 19 are extended from the electrode body 14. The number of positive electrode leads 19 extended from the electrode body 14 may be three or more. This reduces the connection resistance between the positive electrode 11 and the sealing body 16, thereby improving the output characteristics of the secondary battery 10. As the number of positive electrode leads 19 increases, the connection resistance is reduced but the cost increases. Therefore, from the viewpoint of achieving both the effect of reducing the connection resistance and cost, the number of positive electrode leads 19 is preferably three to ten, more preferably three to eight, and particularly preferably three to six. The three or more positive electrode leads 19 extended from the electrode body 14 may be connected to the sealing body 16 directly or via a known current collecting member. The manner of connection between the negative electrode 12 and the outer casing 15 is not particularly limited, and the connection may be made via multiple negative electrode leads 20.

[0015] The exterior body 15 has a bottomed cylindrical shape with an outer diameter of 25 mm or more. The outer diameter of the exterior body 15 is preferably 30 mm or more, and more preferably 35 mm or more. The outer diameter of the exterior body 15 may be 38 mm or more, 40 mm or more, 45 mm or more, or 50 mm or more. The outer diameter of the exterior body 15 may be, for example, 60 mm or less. Within this range, the output characteristics of the secondary battery 10 can be maintained while reducing costs. The thickness of the exterior body 15 is, for example, 0.1 mm to 2 mm, and the inner diameter of the exterior body 15 is preferably 24 mm or more, more preferably 29 mm or more, and particularly preferably 34 mm or more. The inner diameter of the exterior body 15 may be 37 mm or more, 39 mm or more, 44 mm or more, or 49 mm or more. The exterior body 15 is, for example, a metal exterior can. A gasket 27 is provided between the exterior body 15 and the sealing body 16, ensuring the airtightness of the interior of the secondary battery 10. The exterior body 15 has a grooved portion 21 that is formed, for example, by pressing the side surface from the outside and that supports the sealing body 16. The grooved portion 21 is preferably formed in an annular shape along the circumferential direction of the exterior body 15, and supports the sealing body 16 on its upper surface.

[0016] The sealing body 16 includes a filter 22, a lower valve body 23, an insulating member 24, an upper valve body 25, and a cap 26, which are stacked in this order from the electrode body 14 side. Each component of the sealing body 16 has, for example, a disk or ring shape, and all components except for the insulating member 24 are electrically connected to each other. The lower valve body 23 and the upper valve body 25 are connected to each other at their respective centers, with the insulating member 24 interposed between their respective peripheral edges. If the internal pressure of the battery increases due to abnormal heat generation, for example, the lower valve body 23 may break, causing the upper valve body 25 to bulge toward the cap 26 and separate from the lower valve body 25, thereby cutting off the electrical connection between them. If the internal pressure continues to increase, the upper valve body 25 may break, and gas may be released from the opening 26a of the cap 26.

[0017] Next, a connection between the positive electrode 11 and the positive electrode lead 19 will be described with reference to Fig. 2. Fig. 2 is a front view showing the positive electrode 11 and the negative electrode 12 in a developed state, which constitute the electrode body 14 provided in the secondary battery 10 of Fig. 1. The positive electrode 11 has a positive electrode current collector 30 and a positive electrode mixture layer 32 formed on the surface of the positive electrode current collector 30, and the negative electrode 12 has a negative electrode current collector 40 and a negative electrode mixture layer 42 formed on the surface of the negative electrode current collector 40.

[0018] 2, the positive electrode 11 may have, at its upper end, a positive electrode current collector exposed portion 34 where the positive electrode current collector 30 is exposed, and the positive electrode lead 19 may be connected to the positive electrode current collector exposed portion 34. This allows the positive electrode lead 19 to be stably connected to the positive electrode current collector 30, so that the area of ​​the positive electrode mixture layer 32 can be increased while ensuring the area of ​​the positive electrode current collector exposed portion 34, thereby improving the output characteristics of the secondary battery 10.

[0019] Next, the arrangement of the positive electrode lead 19 will be described with reference to Figures 3(a) and 3(b). Figures 3(a) and 3(b) are both plan views showing the position where the positive electrode lead 19 is arranged on the upper surface of the electrode body 14.

[0020] 3(a), the positive electrode leads 19 may be arranged in a substantially straight line in the radial direction, which makes it easier to bundle the positive electrode leads 19 and to join the positive electrode leads 19 to the filter 22. The positive electrode leads 19 may be joined to the filter 22 at multiple locations.

[0021] 3(b), the positive electrode leads 19 may be arranged at substantially equal angles, which makes it easier for each of the multiple positive electrode leads 19 to be joined to the filter 22 without being obstructed by the other positive electrode leads 19.

[0022] Another embodiment of the nonaqueous electrolyte secondary battery according to the present disclosure will be described in detail below with reference to Figures 4 and 5. In the following embodiment, the same components as those in the embodiment shown in Figure 1 are designated by the same reference numerals as those in the embodiment shown in Figure 1, and descriptions thereof will be omitted. In the following embodiment, descriptions of the same effects and modifications as those in the embodiment shown in Figure 1 will be omitted.

[0023] FIG. 4 is a diagram corresponding to FIG. 1 of another example of the embodiment. As shown in FIG. 4, the positive electrode 11 included in the electrode assembly 14 is connected to a positive electrode current collecting member 50, and the positive electrode current collecting member 50 and the sealing body 16 are connected by a positive electrode lead 19. This connects the positive electrode 11 and the sealing body 16, and in the secondary battery 10, the cap 26, which is the top plate of the sealing body 16 electrically connected to the filter 22, serves as the positive electrode terminal. Furthermore, the negative electrode 12 included in the electrode assembly 14 is connected to a negative electrode current collecting member 52, and the negative electrode current collecting member 52 and the exterior body 15 are connected by a negative electrode lead 20. This connects the negative electrode 12 and the exterior body 15, and in the secondary battery 10, the exterior body 15 serves as the negative electrode terminal. Note that the manner of connection between the negative electrode 12 and the exterior body 15 is not particularly limited, and may be, for example, connected by a negative electrode lead 20 as in the embodiment shown in FIG. 1.

[0024] The positive electrode current collecting member 50 is not particularly limited in terms of material, shape, etc., as long as it can be connected to the positive electrode 11 and the sealing member 16, but may be, for example, a disk-shaped member made of aluminum. The positive electrode current collecting member 50 may have one or more holes at any position from the viewpoint of, for example, electrolyte circulation. The negative electrode current collecting member 52 is not particularly limited in terms of material, shape, etc., as long as it can be connected to the negative electrode 12 and the outer casing 15, but may be, for example, a disk-shaped member made of nickel. The negative electrode current collecting member 52 may have one or more holes at any position from the viewpoint of, for example, electrolyte circulation.

[0025] Next, the configuration of the electrode assembly 14 will be described with reference to FIG. 5. FIG. 5 is a perspective view of the electrode assembly 14 in the secondary battery 10 shown in FIG. 4, showing the configuration of the positive electrode 11, negative electrode 12, and separator 13 in a state in which the vicinity of the outer end of the wound electrode is unrolled. In the electrode assembly 14, the positive electrode 11 protrudes upward beyond the negative electrode 12 and separator 13. This allows the positive electrode 11 to be connected to a positive electrode current collector 50. As shown in FIG. 5, the positive electrode 11 may have a positive electrode current collector exposed portion 34 at its upper end where the positive electrode current collector 30 is exposed. This allows the positive electrode 11 and the positive electrode current collector 50 to be more reliably connected. On the other hand, the negative electrode 12 protrudes downward beyond the positive electrode 11 and separator 13. This allows the negative electrode 12 to be connected to a negative electrode current collector 52. As shown in FIG. 5, the negative electrode 12 has a negative electrode current collector 40 exposed at its lower end. negative electrode The negative electrode 12 may have a current collector exposed portion 44. This allows the negative electrode 12 and the negative electrode current collecting member 52 to be connected more reliably.

[0026] The positive electrode 11, negative electrode 12, and separator 13 that constitute the electrode assembly 14 will be described in detail below, with particular reference to the positive electrode 11. The positive electrode 11, negative electrode 12, and separator 13 described below can be applied to any of the above-described embodiments.

[0027] [Positive electrode] The positive electrode 11 includes a positive electrode current collector 30 and a positive electrode mixture layer 32 formed on the surface of the positive electrode current collector 30. The positive electrode mixture layer 32 is preferably formed on both sides of the positive electrode current collector 30. The positive electrode current collector 30 can be made of a foil of a metal, such as aluminum or an aluminum alloy, that is stable within the potential range of the positive electrode 11, or a film with such a metal disposed on its surface. The positive electrode mixture layer 32 contains a positive electrode active material and a conductive agent. The positive electrode 11 can be produced, for example, by applying a positive electrode slurry containing a positive electrode active material, a conductive agent, etc. to the surface of the positive electrode current collector 30, drying the coating, and then compressing it to form the positive electrode mixture layer 32 on both sides of the positive electrode current collector 30.

[0028] The weight of the positive electrode mixture layer 32 is 250 g / m 2 This makes it possible to reduce the cost of the secondary battery 10. The weight of the positive electrode mixture layer 32 is 400 g / m 2 The thickness of the positive electrode mixture layer 32 on one side of the positive electrode current collector 30 is, for example, 10 μm to 150 μm.

[0029] The conductive agent contained in the positive electrode mixture layer 32 includes carbon fiber. The content of carbon fiber in the positive electrode mixture layer 32 may be 0.01 part by mass to 1 part by mass per 100 parts by mass of the positive electrode active material. It is believed that the inclusion of carbon fiber in the positive electrode mixture layer 32 in the above-mentioned predetermined amount ensures a conductive path in the positive electrode mixture layer 32 and contributes to improving durability. If the carbon fiber content is less than 0.01 part by mass, the conductive path in the positive electrode mixture layer 32 is not sufficiently ensured. If the carbon fiber content exceeds 1 part by mass, the movement of the electrolyte in the positive electrode mixture layer 32 is likely to be hindered. In either case, durability is likely to decrease.

[0030] Examples of carbon fibers include known materials used as conductive agents in batteries, such as carbon nanotubes (CNTs), carbon nanofibers (CNFs), vapor-grown carbon fibers (VGCFs), electrospun carbon fibers, polyacrylonitrile (PAN)-based carbon fibers, and pitch-based carbon fibers.

[0031] The outermost diameter of the carbon fibers is preferably 1 nm to 20 nm, and more preferably 1.5 nm to 10 nm, from the viewpoints of improving the electrical conductivity of the carbon fibers themselves and ensuring a conductive path in the positive electrode mixture layer 32 by adding a small amount of carbon fibers due to the improved electrical conductivity. The outermost diameter of the carbon fibers is the average value of the outer diameters of 50 random carbon fibers measured with a field emission scanning electron microscope (FE-SEM) or a transmission electron microscope (TEM).

[0032] The fiber length of the carbon fibers is preferably 0.1 μm to 20 μm, more preferably 1 μm to 10 μm, and particularly preferably 1 μm to 5 μm, in order to ensure a conductive path between the active materials in the positive electrode mixture layer 32. The fiber length of the carbon fibers is the average length of 50 random carbon fibers measured with a field emission scanning electron microscope (FE-SEM).

[0033] Among the carbon fibers exemplified above, it is preferable that the carbon fiber contains a carbon nanotube, for example, in terms of further suppressing capacity loss due to charge / discharge cycles. Examples of carbon nanotubes include single-walled carbon nanotubes, double-walled carbon nanotubes, and multi-walled carbon nanotubes. Single-walled carbon nanotubes (SWCNTs) are carbon nanostructures in which one layer of graphene sheets forms a cylindrical shape. Double-walled carbon nanotubes are carbon nanostructures in which two layers of graphene sheets are concentrically stacked to form a cylindrical shape. Multi-walled carbon nanotubes are carbon nanostructures in which three or more layers of graphene sheets are concentrically stacked to form a cylindrical shape. Note that a graphene sheet refers to a layer in which carbon atoms in sp2 hybrid orbitals that form graphite crystals are located at the vertices of a regular hexagon. The shape of the carbon nanotube is not limited. Examples of such shapes include a needle shape, a cylindrical tube shape, a fishbone shape (fishbone or cup stacked type), a playing card shape (platelet), and a coil shape.

[0034] The carbon nanotubes contained in the positive electrode mixture layer 32 preferably include single-walled carbon nanotubes. Generally, a smaller amount of single-walled carbon nanotubes than multi-walled carbon nanotubes is required to form a conductive path in the positive electrode mixture layer 32. Therefore, it is believed that the inclusion of a small amount of single-walled carbon nanotubes in the positive electrode mixture layer 32 facilitates the movement of the non-aqueous solvent and electrolyte in the positive electrode mixture layer 32. Note that the positive electrode mixture layer 32 may include not only single-walled carbon nanotubes but also double-walled carbon nanotubes or multi-walled carbon nanotubes.

[0035] The conductive agent contained in the positive electrode mixture layer 32 includes amorphous carbon. Examples of amorphous carbon include carbon materials such as carbon black (CB), acetylene black (AB), ketjen black, and graphite. These may be used alone or in combination of two or more. The content of amorphous carbon in the positive electrode mixture layer 32 may be 1 to 3 parts by mass per 100 parts by mass of the positive electrode active material. By containing amorphous carbon in the positive electrode mixture layer 32 in the above-mentioned predetermined amount, the conductivity between the positive electrode active material particles is increased, which may improve the output characteristics of the battery.

[0036] The positive electrode active material contained in the positive electrode mixture layer 32 includes a lithium-containing composite oxide. The lithium-containing composite oxide is, for example, a secondary particle formed by aggregation of a plurality of primary particles. The particle size of the primary particles constituting the secondary particles is, for example, 0.05 μm to 1 μm. The particle size of the primary particles is measured as the diameter of a circumscribed circle in a particle image observed with a scanning electron microscope (SEM).

[0037] The volume-based median diameter (D50) of the secondary particles of the lithium-containing composite oxide is, for example, 1 μm to 30 μm, preferably 3 μm to 20 μm. D50 refers to the particle size at which the cumulative frequency of the smallest particle size in the volume-based particle size distribution is 50%, and is also called the median diameter. The particle size distribution of the composite oxide (Z) can be measured using a laser diffraction particle size distribution analyzer (e.g., MT3000II, manufactured by Microtrack Bell Corporation) with water as the dispersion medium.

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

[0039] The lithium-containing composite oxide contains at least Ni and Mn and is substantially free of Co. Here, "substantially free of Co" means that the lithium-containing composite oxide contains only 0.01 mol % or less of Co relative to the total amount of metal elements excluding Li. Since Co is expensive, not containing it substantially can reduce material costs.

[0040] The content of Ni in the lithium-containing composite oxide is preferably 70 mol % or more, and more preferably 70 mol % to 95 mol %, relative to the total number of moles of metal elements excluding Li. This allows a battery with a high capacity to be obtained. The proportion of Ni relative to the total number of moles of metal elements excluding Li in the lithium-containing composite oxide is particularly preferably 80 mol % or more. This allows a battery with a higher capacity to be obtained. Generally, a high Ni content may reduce safety, but the inclusion of Mn can improve safety. In addition, Mn is an inexpensive element. This allows a battery with a high capacity to be obtained at low cost without reducing battery safety, even if the Ni content is high.

[0041] Lithium-containing composite oxides are represented by the general formula Li a Ni x Al y Mn z M1 w O 2-b(wherein 0.95≦a≦1.05, 0.7≦x≦0.95, 0≦y≦0.1, 0≦z≦0.3, 0≦w≦0.1, 0≦b≦0.05, x+y+z+w=1, and M1 contains at least one element selected from Fe, Ti, Si, Nb, Zr, Mo, W, and Zn). The positive electrode active material may contain a lithium-containing composite oxide other than that represented by the above general formula or other compounds, as long as the object of the present disclosure is not impaired. The molar fraction of the metal element contained in the entire particles of the lithium-containing composite oxide is measured by inductively coupled plasma (ICP) atomic emission spectroscopy.

[0042] A chalcogen compound such as an oxide, sulfate, or niobate, or a halogen compound such as a fluoride may be attached to the surface of the lithium-containing composite oxide. This stabilizes the surface state of the lithium-containing composite oxide through electronic interaction. The amount of the chalcogen compound and halogen compound attached to the surface of the lithium-containing composite oxide is preferably 0.05 mol % to 0.50 mol % relative to the total number of moles of metal elements excluding Li in the lithium-containing composite oxide. Examples of chalcogen compounds include CaO, SrO, Al2O3, ZrO2, TiO2, Li2SO4, LiNbO3, CaTiO3, BaTiO3, Li3BO3, Li2WO4, Li4WO5, and Li6W2O9. Examples of halogen compounds include LiF.

[0043] The surface of the lithium-containing composite oxide to which the chalcogen compound or the halogen compound is attached means the surface of the secondary particles of the lithium-containing composite oxide. The chalcogen compound and the halogen compound may be attached to the surface of the primary particles of the lithium-containing composite oxide. For example, the chalcogen compound and the halogen compound may be present uniformly over the entire surface of the lithium-containing composite oxide, or may be present only partially. The presence of the chalcogen compound and the halogen compound on the surface of the lithium-containing composite oxide can be confirmed by energy dispersive X-ray spectroscopy (TEM-EDX).

[0044] Next, an example of a method for producing a positive electrode active material will be described.

[0045] The method for producing a positive electrode active material includes, for example, a first step of obtaining a composite oxide containing Ni and an arbitrary metal element, a second step of mixing the composite oxide obtained in the first step with a Li compound to obtain a mixture, and a third step of firing the mixture.

[0046] In the first step, for example, an alkaline solution such as sodium hydroxide is added dropwise to a stirred solution of a metal salt containing the essential metal elements Ni and Mn and an optional metal element such as Al, and the pH is adjusted to the alkaline side (e.g., 8.5 to 12.5), thereby precipitating (co-precipitating) a composite hydroxide containing Ni, Mn, and the optional metal element, and the composite hydroxide is calcined to obtain a composite oxide containing Ni, Mn, and the optional metal element. The calcination temperature is not particularly limited, but may be, for example, in the range of 300°C to 600°C.

[0047] In the second step, the composite oxide obtained in the first step is mixed with a Li raw material to obtain a mixture. Examples of Li raw materials include Li2CO3, LiOH, Li2O2, Li2O, LiNO3, LiNO2, Li2SO4, LiOH·H2O, LiH, and LiF. The mixing ratio of the composite oxide and the Li raw material may be appropriately determined so that the desired ratio of each element is obtained in the lithium-containing composite oxide. The molar ratio of Li to metal elements other than Li is preferably in the range of 1:0.9 to 1:1.3. In the second step, when mixing the composite oxide obtained in the first step with a Li compound, a raw material of a chalcogen compound or a halogen compound to be adhered to the surface of the lithium-containing composite oxide may be added. Examples of chalcogen compound raw materials include Ca(OH)2, CaO, CaCO3, CaSO4, Ca(NO3)2, Sr(OH)2, Sr(OH)2·8H2O, SrO, SrCO3, SrSO4, Sr(NO3)2, Al(OH)3, Al2O3, Zr(OH)4, ZrO2, Ti(OH)4, TiO2, Nb(OH)5, etc. Examples of halogen compound raw materials include LiF and CaF2.

[0048] In the third step, the mixture obtained in the second step is fired under an oxygen atmosphere to obtain the lithium-containing composite oxide according to this embodiment. In the third step, the heating rate from 450°C to 680°C may be in the range of more than 0.1°C / min to 5.5°C / min, and the maximum temperature may be in the range of 700°C to 850°C. The heating rate from above 680°C to the maximum temperature may be, for example, 0.1°C / min to 3.5°C / min. The holding time at the maximum temperature may be 1 hour to 10 hours. The third step may be a multi-stage firing, and a plurality of first and second heating rates may be set for each temperature range as long as they are within the above-specified ranges.

[0049] In the manufacturing method of this embodiment, in order to improve battery capacity and safety, the lithium-containing composite oxide powder obtained in the third step may be washed with water. This water washing can be carried out by known methods and conditions, and it may be carried out within a range where lithium elutes from the lithium-containing composite oxide and the battery characteristics do not deteriorate.

[0050] Regarding Li2SO4, Li3BO3, Li2WO4, Li4WO5 and Li6W2O9 among the chalcogen compounds, and AlF3 among the halogen compounds, by subjecting the lithium-containing composite oxide powder obtained in the third step to a coating treatment by known methods and conditions, a lithium-containing composite oxide having Li2SO4 or AlF3 on the surface of the lithium-containing composite oxide can be obtained.

[0051] The positive electrode active material layer 32 may further contain Li2NiO2. Li2NiO2 contains a large amount of Li and functions as a Li replenisher that supplies Li ions to the negative electrode 12 during the first charge and discharge. Li2NiO2 may have a structure identified as the space group Immm.

[0052] When the mass of the positive electrode active material contained in the positive electrode active material layer 32 is 100 parts by mass, the mass of Li2NiO2 contained in the positive electrode active material layer 32 may be 1 part by mass to 10 parts by mass. If the mass of Li2NiO2 contained in the positive electrode active material layer 32 is 1 part by mass or more, a sufficient amount of Li ions can be supplied to the negative electrode. Also, as described later, at least a part of Li2NiO2 changes to a compound represented by the general formula Li a Ni 2-a O2 (0 < a ≤ 0.5). When the mass of Li2NiO2 contained in the positive electrode active material layer 32 exceeds 10 parts by mass, the contribution of the compound represented by the general formula Li a Ni 2-a O2 (0 < a ≤ 0.5) to the charge-discharge capacity is smaller than that of the lithium-containing composite oxide, so the battery capacity decreases.

[0053] Part or all of Li2NiO2 after the first charge and discharge is, for example, the general formula Li a Ni 2-aIt changes to a compound represented by O2(0 < a ≤ 0.5). That is, the positive electrode mixture layer 32 further has the general formula Li a Ni 2-a It may contain a compound represented by O2(0 < a ≤ 0.5). Li a Ni 2-a The compound represented by O2(0 < a ≤ 0.5) releases and stores Li ions during charge and discharge and functions as a positive electrode active material.

[0054] The mass of the compound represented by Li a Ni 2-a O2(0 < a ≤ 0.5) contained in the positive electrode mixture layer 32 may be 0.1 part by mass to 5 parts by mass when the positive electrode active material contained in the positive electrode mixture layer 32 is 100 parts by mass. When the mass of the compound represented by the general formula Li a Ni 2-a O2(0 < a ≤ 0.5) contained in the positive electrode mixture layer 32 is 0.1 part by mass or more, a sufficient amount of Li ions can be supplied to the negative electrode. Also, when the mass of the compound represented by the general formula Li a Ni 2-a O2(0 < a ≤ 0.5) contained in the positive electrode mixture layer 32 exceeds 5 parts by mass, the contribution of the compound represented by the general formula Li a Ni 2-a O2(0 < a ≤ 0.5) to the charge-discharge capacity is smaller than that of the lithium-containing composite oxide, so the battery capacity decreases.

[0055] The positive electrode mixture layer 32 may further contain a binder. Examples of the binder include fluorine-based polymers, rubber-based polymers, etc. Examples of the fluorine-based polymer include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), or modified products thereof, etc. Examples of the rubber-based polymer include ethylene-propylene-isoprene copolymer, ethylene-propylene-butadiene copolymer, etc. These may be used alone or in combination of two or more.

[0056] [Negative electrode] The negative electrode 12 has a negative electrode current collector 40 and a negative electrode mixture layer 42 formed on the surface of the negative electrode current collector 40. The negative electrode mixture layer 42 is preferably formed on both sides of the negative electrode current collector 40. For the negative electrode current collector 40, a foil of a metal stable within the potential range of the negative electrode 12 such as copper or a copper alloy, a film having such a metal disposed on the surface layer, etc. can be used. The negative electrode mixture layer 42 may contain a negative electrode active material, a binder, etc. The negative electrode 12 can be produced, for example, by applying a negative electrode slurry containing a negative electrode active material, a binder, etc. on the surface of the negative electrode current collector 40, drying the coating film, and then rolling it to form the negative electrode mixture layer 42 on both sides of the negative electrode current collector 40.

[0057] The negative electrode active material contained in the negative electrode mixture layer 42 is not particularly limited as long as it can reversibly occlude and release lithium ions, and generally, a carbon material such as graphite is used. The graphite may be any of natural graphite such as flaky graphite, massive graphite, and earthy graphite, artificial massive graphite, and artificial graphite such as graphitized mesophase carbon microbeads. Also, as the negative electrode active material, a metal that alloys with Li such as Si or Sn, a metal compound containing Si or Sn, a lithium titanium composite oxide, etc. may be used. Further, those provided with a carbon coating may be used. For example, a Si-containing compound represented by SiO x (0.5 ≦ x ≦ 1.6), or Li 2y SiO (2+y) A Si-containing compound in which fine particles of Si are dispersed in a lithium silicate phase represented by (0 < y < 2), etc. may be used in combination with graphite.

[0058] For the binder contained in the negative electrode mixture layer 42, similar to the case of the positive electrode 11, a fluororesin, PAN, polyimide, acrylic resin, polyolefin, etc. can also be used, but it is preferable to use styrene-butadiene rubber (SBR). Also, the negative electrode mixture layer 42 may contain CMC or its salt, polyacrylic acid (PAA) or its salt, polyvinyl alcohol (PVA), etc.

[0059] [Separator] The separator 13 may be, for example, a porous sheet having ion permeability and insulating properties. Specific examples of the porous sheet include a microporous thin film, a woven fabric, and a nonwoven fabric. Suitable materials for the separator include polyolefins such as polyethylene and polypropylene, and cellulose. The separator 13 may have a single-layer structure or a laminated structure. Furthermore, the surface of the separator 13 may be provided with a highly heat-resistant resin layer such as an aramid resin, or a filler layer containing an inorganic compound filler. [Example]

[0060] Hereinafter, the present disclosure will be further described with reference to examples and comparative examples, but the present disclosure is not limited to the following examples.

[0061] [Preparation of positive electrode active material] Example 1 [Ni 0.70 Al 0.06 Mn 0.24 The composite hydroxide represented by ](OH)2 was calcined at 500°C for 8 hours to form the composite oxide (Ni 0.70 Al 0.06 Mn 0.24 O2) was obtained (first step). Next, LiOH and the above composite oxide were mixed so that the molar ratio of Li to the total amount of Ni, Al, and Mn was 1.03:1 to obtain a mixture (second step). This mixture was placed under an oxygen flow (10 cm) with an oxygen concentration of 95%. 3 The mixture was fired at a temperature increase rate of 2.0°C / min from room temperature to 650°C, and then at a temperature increase rate of 0.5°C / min from 650°C to 780°C, under a flow rate of 2 mL / min per kg of mixture and 5 L / min per kg of mixture, to obtain a positive electrode active material (third step). The positive electrode active material was analyzed using an ICP emission spectrometer, and LiNi 0.70 Al 0.06 Mn 0.24 It was confirmed that the compound was a lithium-containing composite oxide represented by O2.

[0062] [Preparation of positive electrode] 100 parts by mass of the positive electrode active material, 0.1 parts by mass of carbon nanotubes (having an outermost diameter (φ) of 1.5 nm and a fiber length (L) of 12 μm) as a conductive agent, and 2 parts by mass of polyvinylidene fluoride as a binder were mixed, and this mixture was further mixed with N-methyl-2-pyrrolidone (NMP) to prepare a positive electrode slurry. Next, the slurry was applied to a positive electrode current collector made of aluminum foil with a thickness of 15 μm at a basis weight of 250 g / m. 2 After drying the coating, the coating was rolled with a pressure roller and cut to a predetermined electrode size that could be housed in an outer casing with an outer diameter of 50 mm, thereby obtaining a positive electrode having a positive electrode mixture layer formed on both sides of the positive electrode current collector. Note that an exposed portion where the surface of the positive electrode current collector was exposed was provided at the upper end of the positive electrode.

[0063] [Preparation of negative electrode] Natural graphite was used as the negative electrode active material. The negative electrode active material, carboxymethylcellulose sodium (CMC-Na), and styrene-butadiene rubber (SBR) were mixed in an aqueous solution at a solids mass ratio of 100:1:1 to prepare a negative electrode slurry. The negative electrode slurry was applied to both sides of a negative electrode current collector made of copper foil, and the coating was dried. The coating was then rolled using a rolling roller and cut to a predetermined electrode size to obtain a negative electrode in which a negative electrode mixture layer was formed on both sides of the negative electrode current collector. An exposed portion where the surface of the negative electrode current collector was exposed was provided at the inner end of the negative electrode.

[0064] [Preparation of non-aqueous electrolyte] Ethylene carbonate (EC), methyl ethyl carbonate (MEC), and dimethyl carbonate (DMC) were mixed in a volume ratio of 3:3:4. Lithium hexafluorophosphate (LiPF6) was dissolved in the mixed solvent to a concentration of 1.2 mol / L to prepare a nonaqueous electrolyte.

[0065] [Test cell construction] As shown in Figure 3(a), six aluminum leads were attached to the exposed portion of the positive electrode at approximately equal intervals so that they were arranged in a row in the radial direction of the electrode assembly. One nickel lead was attached to the exposed portion of the negative electrode. The positive and negative electrodes were spirally wound with a polyolefin separator interposed between them to produce a wound electrode assembly. This electrode assembly was housed inside an exterior case with an outer diameter of 50 mm, and the nonaqueous electrolyte was poured into it. The upper opening of the exterior case was then sealed with a sealing member to obtain a test cell.

[0066] [Cost evaluation] The cost of the above test cell was evaluated. The cost is the cost per unit battery capacity. The battery capacity was evaluated by charging at a constant current of 0.3 It at a temperature of 25°C until the battery voltage reached 4.2 V, and then by constant voltage charging at 4.2 V until the current value reached 1 / 50 It. Then, by constant current discharging at a constant current of 0.5 It until the battery voltage reached 2.5 V. The cost was calculated from the material cost of the test cell.

[0067] [Internal resistance measurement] The test cell was charged at a constant current of 0.3 It at a temperature of 25°C until the cell voltage reached 4.2 V, and then charged at a constant voltage of 4.2 V until the current value reached 1 / 50 It. Subsequently, a constant current discharge of 1.0 It was performed for 10 seconds, and the internal resistance was calculated by dividing the voltage drop by the current value.

[0068] <Example 2> In the preparation of the positive electrode active material, the composition of the lithium-containing composite oxide is LiNi 0.75 Mn 0.25 In the preparation of the positive electrode, the conductive agent was changed from 0.1 parts by mass of carbon nanotubes to 1.5 parts by mass of acetylene black, and the weight was 275 g / m 2The test cell was obtained in the same manner as in Example 1, except that the positive electrode slurry was applied so that the positive electrode was in a predetermined electrode size that could be housed in an exterior body having an outer diameter of 45 mm, and the positive electrode was cut into a predetermined electrode size that could be housed in an exterior body having an outer diameter of 45 mm, and that in producing the test cell, as shown in FIG. 4, the positive electrode and the sealing body were connected via a positive electrode current collecting member, and the negative electrode and the exterior body were connected via a negative electrode current collecting member, and the electrode body was housed in an exterior body having an outer diameter of 45 mm.

[0069] Example 3 In the preparation of the positive electrode active material, the composition of the lithium-containing composite oxide is LiNi 0.80 Mn 0.20 In the preparation of the positive electrode, the weight was set to 300 g / m 2 The test cell was obtained in the same manner as in Example 1, except that the positive electrode slurry was applied so that the positive electrode was in a predetermined electrode size that could be housed in an outer casing having an outer diameter of 40 mm, and the positive electrode was obtained by cutting the positive electrode into a predetermined electrode size that could be housed in an outer casing having an outer diameter of 40 mm, and that in producing the test cell, the electrode body was housed in an outer casing having an outer diameter of 40 mm so that the three aluminum leads were arranged at approximately equal angles, as shown in FIG. 3(b).

[0070] Example 4 In the preparation of the positive electrode active material, the composition of the lithium-containing composite oxide is LiNi 0.80 Al 0.055 Mn 0.145 In the preparation of the positive electrode, the weight was set to 325 g / m 2 and in producing the test cell, the number of aluminum leads was changed to three.

[0071] <Example 5> In the preparation of the positive electrode active material, the composition of the lithium-containing composite oxide is LiNi 0.85 Al 0.06 Mn 0.09 In the preparation of the positive electrode, the weight was set to 350 g / m 2The test cell was obtained in the same manner as in Example 1, except that the positive electrode slurry was applied so that the positive electrode was in a predetermined electrode size that could be housed in an exterior body having an outer diameter of 45 mm, and the positive electrode was cut into a predetermined electrode size that could be housed in an exterior body having an outer diameter of 45 mm, and that in producing the test cell, as shown in FIG. 4, the positive electrode and the sealing body were connected via a positive electrode current collecting member, and the negative electrode and the exterior body were connected via a negative electrode current collecting member, and the electrode body was housed in an exterior body having an outer diameter of 45 mm.

[0072] Example 6 In the preparation of the positive electrode active material, the composition of the lithium-containing composite oxide is LiNi 0.90 Al 0.05 Mn 0.05 A test cell was obtained in the same manner as in Example 1, except that the conductive agent was changed from 0.1 parts by mass of carbon nanotubes to 1.5 parts by mass of acetylene black, and 5 parts by mass of LiNiO was added to prepare a positive electrode slurry, which was then cut to a predetermined electrode size to be housed in an outer casing having an outer diameter of 40 mm, and a test cell was obtained by changing the number of aluminum leads to four, and the electrode body was housed in an outer casing having an outer diameter of 40 mm.

[0073] Example 7 In the preparation of the positive electrode active material, the composition of the lithium-containing composite oxide is LiNi 0.925 Al 0.055 Mn 0.02 In the preparation of the positive electrode, 5 parts by mass of LiNiO was further added to prepare a positive electrode slurry with a weight of 300 g / m. 2 The test cell was obtained in the same manner as in Example 1, except that the positive electrode slurry was applied to the electrode so that the positive electrode slurry would be in a predetermined size that could be housed in an exterior body having an outer diameter of 35 mm, and the electrode was cut to a predetermined electrode size that could be housed in an exterior body having an outer diameter of 35 mm, and that in producing the test cell, as shown in FIG. 4, the positive electrode and the sealing body were connected via a positive electrode current collecting member, and the negative electrode and the exterior body were connected via a negative electrode current collecting member, and the electrode body was housed in an exterior body having an outer diameter of 35 mm.

[0074] Example 8 In the preparation of the positive electrode active material, the composition of the lithium-containing composite oxide is LiNi 0.925 Al 0.05Mn 0.025 In the preparation of the positive electrode, the weight was set to 325 g / m 2 and in preparing the test cell, the positive electrode and the sealing body were connected via a positive electrode current collecting member, and the negative electrode and the outer casing were connected via a negative electrode current collecting member, as shown in FIG. 4, to obtain a test cell in the same manner as in Example 1.

[0075] <Comparative Example 1> A test cell was obtained in the same manner as in Example 1, except that the number of aluminum leads was changed to one in the fabrication of the test cell.

[0076] <Comparative Example 2> In the production of the positive electrode, the weight is 200 g / m 2 A test cell was obtained in the same manner as in Example 1, except that the positive electrode slurry was applied so that the positive electrode slurry was

[0077] <Comparative Example 3> A test cell was obtained in the same manner as in Example 1, except that in preparing the positive electrode, the positive electrode was cut to a predetermined electrode size that could be housed in an outer casing with an outer diameter of φ18 mm, and in preparing the test cell, the electrode body was housed in an outer casing with an outer diameter of φ18 mm.

[0078] <Comparative Example 4> In preparing the test cell, the connection between the positive electrode and the sealing body and the negative electrode and the outer casing was changed from the connection shown in FIG. 4 to the connection shown in FIG. 3(a), and the number of positive electrode leads was changed to one. A test cell was obtained in the same manner as in Example 2.

[0079] <Comparative Example 5> In the production of the positive electrode, the weight was 190 g / m 2 A test cell was obtained in the same manner as in Example 2, except that the positive electrode slurry was applied so that the positive electrode was 0.01 mm thick.

[0080] <Comparative Example 6> A test cell was obtained in the same manner as in Example 2, except that in preparing the positive electrode, the positive electrode was obtained by cutting it to a predetermined electrode size that could be housed in an outer casing with an outer diameter of φ21 mm, and in preparing the test cell, the electrode body was housed in an outer casing with an outer diameter of φ21 mm.

[0081] <Comparative Example 7> A test cell was obtained in the same manner as in Example 3, except that the number of aluminum leads was changed to one in the fabrication of the test cell.

[0082] <Comparative Example 8> In the production of the positive electrode, the weight is 200 g / m 2 A test cell was obtained in the same manner as in Example 3, except that the positive electrode slurry was applied so that the positive electrode slurry was

[0083] <Comparative Example 9> A test cell was obtained in the same manner as in Example 3, except that in preparing the positive electrode, the positive electrode was obtained by cutting it to a predetermined electrode size that could be housed in an outer casing with an outer diameter of φ21 mm, and in preparing the test cell, the electrode body was housed in an outer casing with an outer diameter of φ21 mm.

[0084] <Comparative Example 10> A test cell was obtained in the same manner as in Example 4, except that the number of aluminum leads was changed to one in the fabrication of the test cell.

[0085] <Comparative Example 11> In the production of the positive electrode, the weight is 200 g / m 2 A test cell was obtained in the same manner as in Example 4, except that the positive electrode slurry was applied so that the positive electrode slurry was

[0086] <Comparative Example 12> A test cell was obtained in the same manner as in Example 4, except that in preparing the positive electrode, the positive electrode was obtained by cutting it to a predetermined electrode size that could be housed in an outer casing with an outer diameter of φ21 mm, and in preparing the test cell, the electrode body was housed in an outer casing with an outer diameter of φ21 mm.

[0087] <Comparative Example 13> In preparing the test cell, the test cell was obtained in the same manner as in Example 5, except that the connection mode between the positive electrode and the sealing body and the negative electrode and the outer casing was changed from the mode shown in FIG. 4 to the mode shown in FIG. 3(a), and the number of positive electrode leads was changed to one.

[0088] <Comparative Example 14> In the production of the positive electrode, the weight was 225 g / m 2 A test cell was obtained in the same manner as in Example 5, except that the positive electrode slurry was applied so that the positive electrode was

[0089] <Comparative Example 15> A test cell was obtained in the same manner as in Example 5, except that in preparing the positive electrode, the positive electrode was cut to a predetermined electrode size that could be housed in an outer casing with an outer diameter of φ21 mm, and in preparing the test cell, the electrode body was housed in an outer casing with an outer diameter of φ21 mm.

[0090] <Comparative Example 16> A test cell was obtained in the same manner as in Example 6, except that the number of aluminum leads was changed to one in the production of the test cell.

[0091] <Comparative Example 17> In the production of the positive electrode, the weight was 225 g / m 2 A test cell was obtained in the same manner as in Example 6, except that the positive electrode slurry was applied so that the positive electrode slurry was

[0092] <Comparative Example 18> A test cell was obtained in the same manner as in Example 6, except that in preparing the positive electrode, the positive electrode was cut to a predetermined electrode size that could be housed in an outer casing with an outer diameter of φ18 mm, and in preparing the test cell, the electrode body was housed in an outer casing with an outer diameter of φ18 mm.

[0093] <Comparative Example 19> In preparing the test cell, the connection mode between the positive electrode and the sealing body and the negative electrode and the outer casing was changed from the mode shown in FIG. 4 to the mode shown in FIG. 3(a), and the number of positive electrode leads was changed to one. A test cell was obtained in the same manner as in Example 7.

[0094] <Comparative Example 20> In the production of the positive electrode, the weight was 225 g / m 2 A test cell was obtained in the same manner as in Example 7, except that the positive electrode slurry was applied so that the positive electrode slurry was

[0095] <Comparative Example 21> A test cell was obtained in the same manner as in Example 7, except that in preparing the positive electrode, the positive electrode was cut to a predetermined electrode size that could be housed in an outer casing having an outer diameter of φ21 mm, and in preparing the test cell, the electrode body was housed in an outer casing having an outer diameter of φ21 mm.

[0096] <Comparative Example 22> In preparing the test cell, the connection between the positive electrode and the sealing body and the negative electrode and the outer casing was changed from the connection shown in FIG. 4 to the connection shown in FIG. 3(a), and the number of positive electrode leads was changed to one. A test cell was obtained in the same manner as in Example 8.

[0097] <Comparative Example 23> In the production of the positive electrode, the weight was 225 g / m 2 A test cell was obtained in the same manner as in Example 8, except that the positive electrode slurry was applied so that the positive electrode was

[0098] <Comparative Example 24> A test cell was obtained in the same manner as in Example 8, except that in preparing the positive electrode, the positive electrode was obtained by cutting it to a predetermined electrode size that could be housed in an outer casing with an outer diameter of φ18 mm, and in preparing the test cell, the electrode body was housed in an outer casing with an outer diameter of φ18 mm.

[0099] <Reference example 1> In the preparation of the positive electrode active material, the composition of the lithium-containing composite oxide is Ni 0.82 Co 0.15 Al 0.03 In the preparation of the positive electrode, the conductive agent was changed from 0.1 parts by mass of carbon nanotubes to 1.5 parts by mass of acetylene black, and the weight was 350 g / m 2A test cell was obtained in the same manner as in Example 1, except that the positive electrode slurry was applied so that the positive electrode was in a size that could be accommodated in an outer casing having an outer diameter of 45 mm, and the positive electrode was obtained by cutting the positive electrode into a predetermined electrode size that could be accommodated in an outer casing having an outer diameter of 45 mm, and that in producing the test cell, the number of aluminum leads was changed to four, and the electrode body was accommodated in an outer casing having an outer diameter of 45 mm.

[0100] <Reference example 2> A test cell was obtained in the same manner as in Reference Example 1, except that the number of aluminum leads was changed to one in the production of the test cell.

[0101] <Reference example 3> In the production of the positive electrode, the weight was 225 g / m 2 and in preparing the test cell, the positive electrode and the sealing body were connected via a positive electrode current collecting member, and the negative electrode and the outer casing were connected via a negative electrode current collecting member, as shown in FIG. 4, to obtain a test cell in the same manner as in Reference Example 1.

[0102] Tables 1 to 9 show the cost and internal resistance of the test cells of the examples, comparative examples, and reference examples. Tables 1 to 9 also show the composition of the lithium-containing composite oxide (the ratio of each metal element to the total number of moles of metal elements excluding Li), the battery outer diameter, the basis weight of the positive electrode mixture layer, the amount of carbon nanotubes (CNTs), acetylene black (AB), and Li2NiO2 added to the positive electrode mixture layer, the current collection mode of the positive electrode (the mode shown in FIG. 3(a) is referred to as "single row," the mode shown in FIG. 3(b) is referred to as "uniform," and the mode shown in FIG. 4 is referred to as "current collecting member"), and the number of aluminum leads. The costs of the test cells of Comparative Examples 1 to 3 shown in Table 1 are evaluated relative to Example 1. A score of ◯ indicates a cost equivalent to or lower than Example 1, a score of △ indicates a cost 50% or less higher than Example 1, and an score of × indicates a cost more than 50% higher than Example 1. The internal resistances of the test cells of Comparative Examples 1 to 3 are expressed relative to the internal resistance of the test cell of Example 1, which is set at 100.

[0103] The costs of the test cells of Comparative Examples 4 to 6 shown in Table 2 are relative evaluations based on that of Example 2. The internal resistances of the test cells of Comparative Examples 4 to 6 are expressed relative to the internal resistance of the test cell of Example 2, which is set at 100.

[0104] The costs of the test cells of Comparative Examples 7 to 9 shown in Table 3 are relative evaluations based on Example 3. The internal resistances of the test cells of Comparative Examples 7 to 9 are expressed relative to the internal resistance of the test cell of Example 3, which is set to 100.

[0105] The costs of the test cells of Comparative Examples 10 to 12 shown in Table 4 are relative evaluations based on that of Example 4. The internal resistances of the test cells of Comparative Examples 10 to 12 are expressed relative to the internal resistance of the test cell of Example 4, which is set to 100.

[0106] The costs of the test cells of Comparative Examples 13 to 15 shown in Table 5 are relative evaluations based on that of Example 5. The internal resistances of the test cells of Comparative Examples 13 to 15 are expressed relative to the internal resistance of the test cell of Example 5, which is set at 100.

[0107] The costs of the test cells of Comparative Examples 16 to 18 shown in Table 6 are relative evaluations based on that of Example 6. The internal resistances of the test cells of Comparative Examples 16 to 18 are expressed relative to the internal resistance of the test cell of Example 6, which is set at 100.

[0108] The costs of the test cells of Comparative Examples 19 to 21 shown in Table 7 are relative evaluations based on that of Example 7. The internal resistances of the test cells of Comparative Examples 19 to 21 are also expressed relative to the internal resistance of the test cell of Example 7, which is set at 100.

[0109] The costs of the test cells of Comparative Examples 22 to 24 shown in Table 8 are relative evaluations based on that of Example 8. The internal resistances of the test cells of Comparative Examples 22 to 24 are expressed relative to the internal resistance of the test cell of Example 8, which is set at 100.

[0110] The costs of the test cells of Reference Examples 1 to 3 shown in Table 9 are relative evaluations based on Reference Example 1. The internal resistances of the test cells of Reference Examples 1 to 3 are expressed relative to the internal resistance of the test cell of Reference Example 1, which is set to 100.

[0111] [Table 1]

[0112] [Table 2]

[0113] [Table 3]

[0114] [Table 4]

[0115] [Table 5]

[0116] [Table 6]

[0117] [Table 7]

[0118] [Table 8]

[0119] [Table 9]

[0120] In all of Tables 1 to 8, the Examples are able to achieve both cost reduction and reduced internal resistance compared to the Comparative Examples. [Explanation of symbols]

[0121] 10 secondary battery, 11 positive electrode, 12 negative electrode, 13 separator, 14 electrode body, 15 exterior body, 16 sealing body, 17, 18 insulating plate, 19 positive electrode lead, 20 negative electrode lead, 21 grooved portion, 22 filter, 23 lower valve body, 24 insulating member, 25 upper valve body, 26 cap, 26a opening, 27 gasket, 30 positive electrode current collector, 32 positive electrode mixture layer, 34 positive electrode exposed portion, 40 negative electrode current collector, 42 negative electrode mixture layer, 44 negative electrode exposed portion, 50 positive electrode current collector, 52 negative electrode current collector

Claims

1. an electrode assembly in which a strip-shaped positive electrode and a strip-shaped negative electrode are wound with a separator interposed therebetween; a cylindrical exterior body with an outer diameter of 25 mm or more and a bottom that houses the electrode assembly and is connected to the negative electrode; a sealing body that seals an opening at an upper end of the exterior body and is connected to the positive electrode, the positive electrode includes a positive electrode current collector and a positive electrode mixture layer formed on a surface of the positive electrode current collector and containing a positive electrode active material and a conductive agent; the positive electrode active material includes a lithium-containing composite oxide, the lithium-containing composite oxide having a layered rock salt structure, substantially not containing Co, and containing at least Ni and Mn; the content of Ni in the lithium-containing composite oxide is 70 mol% or more with respect to the total number of moles of metal elements excluding Li, The basis weight of the positive electrode mixture layer is 250 g / m ２ That's all, a non-aqueous electrolyte secondary battery, wherein three or more positive electrode leads are led out from the electrode assembly;

2. The nonaqueous electrolyte secondary battery according to claim 1 , wherein the positive electrode leads are arranged in a substantially linear row in the radial direction on the upper surface of the electrode body.

3. 2. The nonaqueous electrolyte secondary battery according to claim 1, wherein the positive electrode leads are disposed at a substantially uniform angle on the upper surface of the electrode assembly.

4. 4. The nonaqueous electrolyte secondary battery according to claim 1, wherein the positive electrode has, at an upper end thereof, a positive electrode current collector exposed portion where the positive electrode current collector is exposed, and the positive electrode lead is connected to the positive electrode current collector exposed portion.

5. an electrode assembly in which a strip-shaped positive electrode and a strip-shaped negative electrode are wound with a separator interposed therebetween; a cylindrical exterior body with an outer diameter of 25 mm or more and a bottom that houses the electrode assembly and is connected to the negative electrode; a sealing body that seals an opening at an upper end of the exterior body and is connected to the positive electrode, the positive electrode includes a positive electrode current collector and a positive electrode mixture layer formed on a surface of the positive electrode current collector and containing a positive electrode active material and a conductive agent; the positive electrode active material includes a lithium-containing composite oxide, the lithium-containing composite oxide having a layered rock salt structure, substantially not containing Co, and containing at least Ni and Mn; the content of Ni in the lithium-containing composite oxide is 70 mol% or more with respect to the total number of moles of metal elements excluding Li, The basis weight of the positive electrode mixture layer is 250 g / m ２ That's all, the positive electrode protruding above the negative electrode and the separator in the electrode assembly is connected to a positive electrode current collecting member, and the positive electrode current collecting member and the sealing body are connected by a positive electrode lead.

6. 6. The nonaqueous electrolyte secondary battery according to claim 1, wherein the conductive agent contains carbon fiber, and the content of the carbon fiber in the positive electrode mixture layer is 0.01 parts by mass to 1 part by mass with respect to 100 parts by mass of the positive electrode active material.

7. 7. The nonaqueous electrolyte secondary battery according to claim 1, wherein the conductive agent contains amorphous carbon, and the content of the amorphous carbon contained in the positive electrode mixture layer is 1 part by mass to 3 parts by mass per 100 parts by mass of the positive electrode active material.

8. 8. The nonaqueous electrolyte secondary battery according to claim 1, wherein the content of Ni in the lithium-containing composite oxide is 70 mol % to 95 mol % with respect to the total number of moles of metal elements excluding Li.

9. The positive electrode mixture layer further contains Li ２ NiO ２ The non-aqueous electrolyte secondary battery according to any one of claims 1 to 8, comprising:

10. Li contained in the positive electrode mixture layer ２ NiO ２ 10. The nonaqueous electrolyte secondary battery according to claim 9, wherein the mass of the positive electrode active material contained in the positive electrode mixture layer is 1 part by mass to 10 parts by mass, where the mass of the positive electrode active material contained in the positive electrode mixture layer is 100 parts by mass.

11. The positive electrode mixture layer further comprises a compound represented by the general formula Li ａ Ni ２－ａ O ２ 11. The nonaqueous electrolyte secondary battery according to claim 1, containing a compound represented by the formula (0<a≦0.5).

12. The positive electrode mixture layer contains ａ Ni ２－ａ O ２ 12. The nonaqueous electrolyte secondary battery according to claim 11, wherein the mass of the compound represented by (0<a≦0.5) is 0.1 parts by mass to 5 parts by mass, relative to 100 parts by mass of the positive electrode active material contained in the positive electrode mixture layer.

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