Nonaqueous electrolyte secondary battery and manufacturing method

Abstract

To provide a nonaqueous electrolyte secondary battery in which an increase in internal resistance is suppressed and which has good fusing properties, and a method for manufacturing the nonaqueous electrolyte secondary battery.SOLUTION: In a nonaqueous electrolyte secondary battery in which a positive electrode active material layer contains a positive electrode active material represented by the formula (1), when the specific surface area of the negative electrode active material layer is S, the average boron content of boron contained in the negative electrode active material layer is M1 (mass %), and the boron content in a central portion of the negative electrode active material layer is M2 (mass %), the relationship formulas (a) and (b) are satisfied.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a non-aqueous electrolyte secondary battery, and more particularly to a method for manufacturing a non-aqueous electrolyte secondary battery.

Background Art

[0002] Japanese Patent Application Laid-Open No. 2022-112207 (Patent Document 1) proposes a non-aqueous electrolyte secondary battery using a lithium composite oxide having a high nickel content as a positive electrode active material layer.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When a lithium composite oxide having a high nickel content is used for the positive electrode active material layer, it is possible to increase the capacity of a non-aqueous electrolyte secondary battery (hereinafter also referred to as a battery). However, when conductive foreign matter is mixed into the battery, it has been found that the heat of reaction between the positive electrode plate and the electrolytic solution tends to be generated easily by the following steps (1) to (3). (1) A current (short-circuit current) flows through the conductive foreign matter to generate heat. (2) Along with the heat generation in the above (1), the negative electrode plate and the electrolytic solution react to generate heat. (3) The positive electrode and the electrolytic solution react to generate heat. In addition, when the battery size is relatively large, the short-circuit current increases, and as a result, the heat of reaction between the positive electrode plate and the electrolytic solution tends to be generated easily.

[0005] In order to suppress the reaction heat between the positive electrode plate and the electrolytic solution, there is a demand for an improvement in the fusing performance that shuts off the short-circuit current by the melting and spreading of the positive electrode substrate (such as a metal foil). The shorter the time from the occurrence of a short circuit to the occurrence of fusing, the better the fusing performance. Although the fusing property tends to improve when a film is formed by the electrolytic solution on the surface of the positive electrode active material, the internal resistance of the battery increases, and as a result, the output characteristics tend to deteriorate.

[0006] An object of the present disclosure is to provide a non-aqueous electrolyte secondary battery and a method for manufacturing a non-aqueous electrolyte secondary battery in which an increase in internal resistance is suppressed and which has good fusing properties.

Means for Solving the Problems

[0007] The present invention provides the following non-aqueous electrolyte secondary battery and method for manufacturing a non-aqueous electrolyte secondary battery. [1] Including an electrode body and an electrolytic solution, The electrode body includes a positive electrode plate and a negative electrode plate, The positive electrode plate includes a positive electrode active material layer, The negative electrode plate includes a negative electrode active material layer, The positive electrode active material layer has the formula (1): Li (1+x) Ni y Ti z Me (1-y-z) O 2 [In formula (1), Me includes two or more selected from the group consisting of Mn, Co, and Al, Satisfies the relationships of 0 < x < 0.1, 0.8 < y < 0.85, 0 ≤ z < 0.03] And includes a positive electrode active material represented by The negative electrode active material layer includes a negative electrode active material, When the specific surface area of the negative electrode active material layer is S, the average boron content of boron contained in the negative electrode active material layer is M1 (mass%), and the boron content of the central portion of the negative electrode active material layer is M2 (mass%), the following relational expression: (a) M1 / S ≤ 0.1 (b) M2 ≥ 0.05 A non-aqueous electrolyte secondary battery that satisfies. [2] The total opposing area of the electrode body is 3 m 2 or more, The non-aqueous electrolyte secondary battery according to [1], wherein the length of the short side of the shape of one continuous negative electrode active material layer in the negative electrode plate in a plan view is 80 mm or more and 400 mm or less. [3] The following relational expression: (c) 2 ≦ S ≦ 4 The non-aqueous electrolyte secondary battery according to [1], which further satisfies. [4] The non-aqueous electrolyte secondary battery according to [1], wherein the graphite content in the negative electrode active material is 99% by mass or more. [5] A method for manufacturing a non-aqueous electrolyte secondary battery, comprising: a step of inserting an electrode body into an exterior body, a step of injecting an electrolytic solution, and an activation step, wherein the electrode body includes a positive electrode plate and a negative electrode plate, the positive electrode plate includes a positive electrode active material layer, the negative electrode plate includes a negative electrode active material layer, the positive electrode active material layer has the formula (1): Li (1+x) Ni y Ti z Me (1-y-z) O 2 [In formula (1), Me includes two or more selected from the group consisting of Mn, Co, and Al, satisfying the relationships of 0 < x < 0.1, 0.8 < y < 0.85, and 0 ≦ z < 0.03] and includes a positive electrode active material represented by, the negative electrode active material layer includes a negative electrode active material, when the specific surface area of the negative electrode active material layer is S, the average boron content of boron contained in the negative electrode active material layer is M1 (mass%), and the boron content of the central portion of the negative electrode active material layer is M2 (mass%), the following relational expression: (a) M1 / S ≦ 0.1 (b) M2 ≧ 0.05 A method for manufacturing a non-aqueous electrolyte secondary battery that satisfies.

Advantages of the Invention

[0008] According to the present disclosure, it is possible to provide a non-aqueous electrolyte secondary battery in which an increase in internal resistance is suppressed and which has good fusing properties, and a method for manufacturing the non-aqueous electrolyte secondary battery.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Embodiments for Carrying Out the Invention

[0010] Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to the following embodiments. In all the following drawings, the scale is appropriately adjusted for easy understanding of each component, and the scale of each component shown in the drawings does not necessarily match the scale of the actual component. In the description of each of the following embodiments, the same or corresponding parts in the drawings are denoted by the same reference numerals, and the description thereof will not be repeated.

[0011] <Non-aqueous electrolyte secondary battery> FIG. 1 is a schematic diagram showing an example of the configuration of a battery in the present embodiment. The battery 100 can be used for any application. The battery 100 may be used, for example, as a main power source or a power assist power source in an electric vehicle. A battery module or a battery pack may be formed by connecting a plurality of batteries 100.

[0012] The battery 100 includes an exterior body 90. The exterior body 90 is rectangular (flat cuboid shape). However, the rectangular shape is just an example. The exterior body 90 can have any form. The exterior body 90 may be, for example, cylindrical or pouch-shaped. The exterior body 90 may be made of, for example, an Al alloy. The exterior body 90 houses the electrode body 50 and an electrolytic solution (not shown). The exterior body 90 may include, for example, a sealing plate 91 and an exterior can 92. The sealing plate 91 closes the opening of the exterior can 92. For example, the sealing plate 91 and the exterior can 92 may be joined by laser welding.

[0013] A positive electrode terminal 81 and a negative electrode terminal 82 are provided on the sealing plate 91. A liquid injection port and a gas discharge valve may be further provided on the sealing plate 91. The electrolytic solution can be injected into the interior of the exterior body 90 through the liquid injection port. The electrode body 50 is connected to the positive electrode terminal 81 by a positive electrode current collector member 71. The positive electrode current collector member 71 may be, for example, an Al plate or the like. The electrode body 50 is connected to the negative electrode terminal 82 by a negative electrode current collector member 72. The negative electrode current collector member 72 may be, for example, a Cu plate or the like.

[0014] FIG. 2 is a schematic diagram showing an example of the configuration of the electrode body in the present embodiment. The electrode body 50 is a wound type. The electrode body 50 includes a positive electrode plate 10, a separator 30, and a negative electrode plate 20. That is, the battery 100 includes the positive electrode plate 10, the negative electrode plate 20, and the electrolytic solution. The positive electrode plate 10, the separator 30, and the negative electrode plate 20 are all strip-shaped sheets. The electrode body 50 may include a plurality of separators 30. The electrode body 50 is formed by laminating the positive electrode plate 10, the separator 30, and the negative electrode plate 20 in this order and winding them in a spiral shape. One of the positive electrode plate 10 or the negative electrode plate 20 may be sandwiched between the separators 30. Both the positive electrode plate 10 and the negative electrode plate 20 may be sandwiched between the separators 30. The electrode body 50 may be formed into a flat shape after winding. Note that the wound type is just an example. The electrode body 50 may be, for example, a stacked type.

[0015] The total opposing area of the electrode body 50 is, for example, 3 m 2The above may be applicable. As shown in FIG. 2, the electrode body 50 has a structure in which the positive electrode plate 10 and the negative electrode plate 20 are laminated with each other via the separator 30, so that portions facing the negative electrode plate 20 on one or both sides of the positive electrode plate 10, and portions facing the positive electrode plate 10 on one or both sides of the negative electrode plate 20 are formed. The total facing area of the electrode body 50 refers to the sum of the area of the portion of the positive electrode plate 10 facing the negative electrode plate 20 and the area of the portion of the negative electrode plate 20 facing the positive electrode plate 10. The total facing area of the electrode body 50 may be, for example, 3 m 2 above 10 m 2 and below may be applicable.

[0016] (Positive Electrode Plate) The positive electrode plate 10 includes a positive electrode substrate 11 and a positive electrode active material layer 12. The positive electrode substrate 11 is a conductive sheet. The positive electrode substrate 11 may be, for example, an Al alloy foil or the like. The positive electrode substrate 11 may have a thickness of, for example, 10 μm to 30 μm. The positive electrode active material layer 12 is disposed on the surface of the positive electrode substrate 11. The positive electrode active material layer 12 may be disposed on only one side of the positive electrode substrate 11, for example. The positive electrode active material layer 12 may be disposed on both the front and back surfaces of the positive electrode substrate 11, for example. In the width direction of the positive electrode plate 10 (the X-axis direction in FIG. 2), the positive electrode substrate 11 may be exposed at one end. A positive electrode current collecting member 71 may be joined to the exposed portion of the positive electrode substrate 11.

[0017] For example, an intermediate layer (not shown) may be formed between the positive electrode active material layer 12 and the positive electrode substrate 11. In the present embodiment, even if there is an intermediate layer, the positive electrode active material layer 12 is regarded as being disposed on the surface of the positive electrode substrate 11. The intermediate layer may be thinner than the positive electrode active material layer 12. The intermediate layer may have a thickness of, for example, 0.1 μm to 10 μm. The intermediate layer may contain, for example, a conductive material, an insulating material, or the like.

[0018] (Positive Electrode Active Material Layer) The positive electrode active material layer 12 contains a positive electrode active material. The positive electrode active material is represented by the following formula (1): Li (1+x) Ni y Ti z Me (1-y-z) O 2 [In formula (1), Me contains two or more selected from the group consisting of Mn, Co, and Al, satisfying the relationships of 0 < x < 0.1, 0.8 < y < 0.85, and 0 ≤ z < 0.03] and contains a layered metal oxide represented by

[0019] The layered metal oxide represented by formula (1) preferably satisfies the relationships of 0 < x < 0.2, 0.8 < y < 0.84, and 0.01 < z < 0.03 from the viewpoint of fusing property.

[0020] The layered metal oxide represented by formula (1) may contain at least one selected from the group consisting of Zr, B, Mg, Fe, Cu, Zn, Sn, Na, K, Ba, Sr, Ca, W, Mo, Nb, Si, V, Cr, and Ge.

[0021] The positive electrode active material is a particle group. The particle group can include a first positive electrode active material particle group and a second positive electrode active material particle group. The first positive electrode active material particle group consists of a plurality of first positive electrode active material particles. The second positive electrode active material particle group consists of a plurality of second positive electrode active material particles. The first positive electrode active material particles and the second positive electrode active material particles can have any shape. The first positive electrode active material particles and the second positive electrode active material particles may be, for example, spherical, columnar, massive, etc.

[0022] The plurality of first positive electrode active material particles may have an average particle diameter (D50) of, for example, 10 μm to 20 μm. The plurality of second positive electrode active material particles may have an average particle diameter (D50) of, for example, 0.5 μm to 9 μm. The average particle diameter (D50) in this specification is the particle diameter at which the cumulative frequency from the smaller particle diameter in the volume-based particle size distribution reaches 50%. The volume-based particle size distribution can be measured by a laser diffraction particle size distribution measuring device.

[0023] The first positive electrode active material particles and the second positive electrode active material particles each independently contain a positive electrode active material represented by formula (1). The first positive electrode active material particles and the second positive electrode active material particles may each independently have an arbitrary crystal structure. The first positive electrode active material particles and the second positive electrode active material particles may each independently have, for example, a layered structure, a spinel structure, an olivine structure, or the like. The first positive electrode active material particles and the second positive electrode active material particles may have substantially the same chemical composition. The first positive electrode active material particles and the second positive electrode active material particles may have different chemical compositions from each other.

[0024] As long as the positive electrode active material layer 12 contains a positive electrode active material, it may further contain additional components. In addition to the positive electrode active material, the positive electrode active material layer 12 may contain, for example, a conductive material and a binder. The conductive material may contain any components. The conductive material may contain, for example, at least one selected from the group consisting of carbon black, graphite, vapor-grown carbon fiber (VGCF), carbon nanotube (CNT), and graphene flakes. The blending amount of the conductive material may be, for example, from 0.1 parts by mass to 10 parts by mass with respect to 100 parts by mass of the positive electrode active material. The binder may contain any components. The binder may contain, for example, at least one selected from the group consisting of polyvinylidene fluoride (PVdF), poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP), polytetrafluoroethylene (PTFE), and polyacrylic acid (PAA). The blending amount of the binder may be, for example, from 0.1 parts by mass to 10 parts by mass with respect to 100 parts by mass of the positive electrode active material. The positive electrode active material layer 12 may contain, for example, by mass fraction, 80% to 99% of the positive electrode active material, 0.1% to 10% of the conductive material, and the balance of the binder.

[0025] The positive electrode active material layer 12 may have a thickness of, for example, 10 μm to 200 μm. The positive electrode active material layer 12 may have a thickness of, for example, 50 μm to 150 μm. The positive electrode active material layer 12 may have a thickness of, for example, 50 μm to 100 μm.

[0026] The positive electrode active material layer 12 may have a high density. The positive electrode active material layer 12 may have a density, for example, of from 3.3 g / cm 3 to 3.9 g / cm 3 . The positive electrode active material layer 12 may have a density, for example, of from 3.4 g / cm 3 to 3.7 g / cm 3 . The positive electrode active material layer 12 may have a density, for example, of from 3.4 g / cm 3 to 3.6 g / cm 3 . The density of the active material layer in this specification indicates the apparent density.

[0027] The positive electrode plate 10 is manufactured by forming the positive electrode active material layer 12 by applying a positive electrode slurry to the surface of the positive electrode substrate 11, then rolling the positive electrode active material layer 12 and the positive electrode substrate 11 to produce a raw sheet, and then cutting the raw sheet to a predetermined planar size according to the specifications of the battery 100. The positive electrode slurry is prepared by mixing a positive electrode active material and additional components.

[0028] (Negative electrode plate) The negative electrode plate 20 may include, for example, a negative electrode substrate 21 and a negative electrode active material layer 22. The negative electrode substrate 21 is a conductive sheet. The negative electrode substrate 21 may be, for example, a Cu alloy foil or the like. The negative electrode substrate 21 may have a thickness of, for example, from 5 μm to 30 μm. The negative electrode active material layer 22 may be disposed on the surface of the negative electrode substrate 21. The negative electrode active material layer 22 may be disposed on only one side of the negative electrode substrate 21, for example. The negative electrode active material layer 22 may be disposed on both the front and back surfaces of the negative electrode substrate 21, for example. In the width direction of the negative electrode plate 20 (the X-axis direction in FIG. 2), the negative electrode substrate 21 may be exposed at one end. A negative electrode current collector member 72 may be joined to the exposed portion of the negative electrode substrate 21.

[0029] (Negative electrode active material layer) The negative electrode active material layer 22 contains a negative electrode active material. The negative electrode active material may contain any components. The negative electrode active material may contain at least one selected from the group consisting of, for example, graphite, soft carbon, hard carbon, silicon, silicon oxide, silicon-based alloy, tin, tin oxide, tin-based alloy, and lithium titanium composite oxide. The graphite may be natural graphite or artificial graphite.

[0030] The negative electrode active material layer 22 further contains boron (B). When the specific surface area of the negative electrode active material layer 22 is S, the average boron content of boron contained in the negative electrode active material layer 22 is M1 (mass %), and the boron content of the central portion of the negative electrode active material layer 22 is M2 (mass %), the following relational expressions: (a) M1 / S ≤ 0.1 (b) M2 ≥ 0.05 are satisfied. The above central portion is the central portion in the negative electrode plate plane when the negative electrode plate is viewed from the plan view direction.

[0031] When the electrode body 50 is viewed from the plane direction of the electrode plate, the central portion in the electrode plate plane tends to be difficult for the electrolytic solution to penetrate. For example, in a rectangular battery, since the electrolytic solution is injected from a surface other than the plane direction of the electrode plate constituting the electrode body (any one of the four short side surfaces, generally the liquid injection hole on the lid side), the electrolytic solution tends not to penetrate into the central portion of the electrode plate in the electrode plate plane. As a result, the amount of the film formed by the electrolytic solution on the surface of the active material decreases, and the fusing property tends to deteriorate. Also, if an attempt is made to increase the amount of the film in the central portion of the electrode body 50, the amount of the film becomes too large, and as a result, the internal resistance of the battery tends to increase. However, by satisfying the relational expressions (a) and (b), it becomes possible to provide a battery with a balanced resistance and fusing property. The central portion of the negative electrode plate can be a region with a radius of 20 mm from the center of the negative electrode plate plane when the electrode body 50 is viewed from the Y-axis direction.

[0032] Examples of methods for satisfying the relational expressions (a) and (b) include, for example, selection of the type of additive contained in the electrolytic solution and adjustment of the concentration, adjustment of the specific surface area, thickness, and density of the negative electrode active material layer 22, selection of the type of negative electrode active material, and adjustment of the content. After the activation process described later, the battery 100 can satisfy the relational expressions (a) and (b).

[0033] M1 may be, for example, 0.1 to 0.5% by mass, preferably 0.15 to 3% by mass. M2 may be, for example, 0.05 to 0.3% by mass, preferably 0.09 to 0.2% by mass. M1 and M2 are measured according to the method described in the column of the examples described later. M2 may be the boron content at the center in the negative electrode active material layer of the outermost layer portion in the case of a wound electrode body. M1 may be the average value of the boron contents at nine in-plane locations in the negative electrode active material layer of the outermost layer portion in the case of a wound electrode body. Further, M2 may be the boron content at the center in the negative electrode active material layer of the outermost layer in the case of a laminated electrode body. M1 may be the average value of the boron contents at nine in-plane locations in the negative electrode active material layer of the outermost layer in the case of a laminated electrode body.

[0034] The negative electrode active material layer 22 satisfies the following relational expression: (c) 2 ≤ S ≤ 4 The specific surface area S of the negative electrode active material layer 22 is measured according to the method described in the column of the examples described later.

[0035] In addition to the negative electrode active material, the negative electrode active material layer 22 may further contain, for example, a binder or the like as other components. The negative electrode active material layer 22 may contain, for example, by mass fraction, 95% to 99.5% of the negative electrode active material and the balance of the binder. The binder may contain any component. The binder may contain at least one selected from the group consisting of, for example, carboxymethyl cellulose (CMC) and styrene butadiene rubber (SBR). When the negative electrode active material layer 22 contains graphite, the graphite content in the negative electrode active material is preferably 99% by mass or more. The specific surface area of the negative electrode active material may be, for example, 0.5 to 5 m 2 / g.

[0036] The negative electrode active material layer 22 may have a thickness of, for example, 10 μm to 200 μm.

[0037] The negative electrode active material layer 22 can have a high density. The negative electrode active material layer 22 may have a density of, for example, 1.0 g / cm 3 to 2.0 g / cm 3 The negative electrode active material layer 22 may have a density of, for example, 1.2 g / cm 3 to 1.7 g / cm 3 The negative electrode active material layer 22 may have a density of, for example, 1.3 g / cm 3 to 1.6 g / cm 3 The negative electrode active material layer 22 may have a density of, for example, 1.3 g / cm

[0038] The negative electrode plate 20 is manufactured by forming the negative electrode active material layer 22 by applying a negative electrode slurry to the surface of the negative electrode substrate 21, then rolling the negative electrode active material layer 22 and the negative electrode substrate 21 to produce a raw sheet, and then cutting it to a predetermined planar size according to the specifications of the battery 100. The negative electrode slurry is prepared by mixing a negative electrode active material and other components.

[0039] The shape of one continuous negative electrode active material layer in the negative electrode plate 20 in plan view may be, for example, rectangular. The length of the short side of the shape of one continuous negative electrode active material layer in the negative electrode plate 20 in plan view (the length of L in FIG. 2) may be, for example, 80 mm or more and 400 mm or less.

[0040] (Separator) At least a part of the separator 30 is interposed between the positive electrode plate 10 and the negative electrode plate 20. The separator 30 separates the positive electrode plate 10 and the negative electrode plate 20. The separator 30 may have a thickness of, for example, 10 μm to 30 μm.

[0041] Separator 30 is a porous sheet. Separator 30 permeates the electrolyte. Separator 30 may have an air permeability of, for example, from 100 s / 100 mL to 400 s / 100 mL. The "air permeability" in this specification indicates the "Air Resistance" defined in "JIS P 8117:2009". The air permeability is measured by the Gurley test method.

[0042] Separator 30 is electrically insulating. Separator 30 may contain, for example, a polyolefin-based resin or the like. Separator 30 may consist essentially of, for example, a polyolefin-based resin. The polyolefin-based resin may contain at least one selected from the group consisting of, for example, polyethylene (PE) and polypropylene (PP). Separator 30 may have, for example, a single-layer structure. Separator 30 may consist essentially of, for example, a PE layer. Separator 30 may have, for example, a multilayer structure. Separator 30 may be formed, for example, by laminating a PP layer, a PE layer, and a PP layer in this order. A heat-resistant layer or the like may be formed on the surface of Separator 30.

[0043] (Electrolyte) The electrolyte contains a solvent and a supporting electrolyte. The solvent is aprotic. The solvent may contain any components. The solvent may contain, for example, at least one selected from the group consisting of ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), 1,2-dimethoxyethane (DME), methyl formate (MF), methyl acetate (MA), methyl propionate (MP), and γ-butyrolactone (GBL).

[0044] The supporting electrolyte is dissolved in the solvent. The supporting electrolyte is, for example, LiPF 6 、LiBF 4 、and LiN(FSO 2 ) 2It may contain at least one selected from the group consisting of. The supporting electrolyte may have a molar concentration of, for example, from 0.5 mol / L to 2.0 mol / L. The supporting electrolyte may have a molar concentration of, for example, from 0.8 mol / L to 1.2 mol / L.

[0045] The electrolytic solution may further contain an optional additive. For example, the electrolytic solution may contain an additive in a mass fraction of from 0.01% to 5%. The additive may be, for example, at least one selected from the group consisting of vinylene carbonate (VC), lithium difluorophosphate (LiPO 2 F 2 ), lithium fluorosulfonate (FSO 3 Li) and lithium bis(oxalato)borate (LiBOB). The electrolytic solution preferably contains LiBOB. When the electrolytic solution contains LiBOB, the content of LiBOB in the electrolytic solution may be, for example, 0.1 to 1.5% by mass.

[0046] <Method for manufacturing a battery> As shown in FIG. 3, the method for manufacturing a battery according to the present embodiment includes a step (A) of inserting an electrode body into an exterior body, a step (B) of injecting an electrolytic solution, and an activation step (C).

[0047] In the step (A) of inserting the electrode body into the exterior body, the electrode body 50 is housed in the exterior body 90. The electrode body 50 can be connected to the positive electrode terminal 81 by the positive electrode current collector member 71. The electrode body 50 can be connected to the negative electrode terminal 82 by, for example, the negative electrode current collector member 72.

[0048] In the step (B) of injecting the electrolytic solution, the electrolytic solution is injected into the exterior body 90. The electrolytic solution is impregnated into the electrode body 50. After the injection of the electrolytic solution, the exterior body 90 is sealed.

[0049] In the activation step (C), the battery 100 is activated. For example, the battery 100 is charged in a constant current-constant voltage (CC-CV) mode, and after a predetermined time has elapsed, it is discharged in a constant current (CC-CV) mode. More specifically, in a temperature environment of 25°C, 0.2 mA / cm 2The current causes charging in a constant current mode until the positive electrode potential reaches 4.30 V (vs. Li + / Li), and then charging is continued in a constant voltage mode until the current reaches 0.04 mA / cm 2 . Thereafter, with a 10-minute pause in between, discharging is carried out in a constant current mode with a current of 0.2 mA / cm 2 until the positive electrode potential reaches 2.5 V (vs. Li + / Li).

[0050] From the above, the battery 100 is manufactured. The manufactured battery 100 satisfies the relational expressions (a) and (b) as described above, thereby suppressing an increase in internal resistance and having good fusing properties.

Example

[0051] Hereinafter, the present invention will be described in more detail with reference to examples. In the examples, “%” and “parts” are mass % and parts by mass, respectively, unless otherwise specified.

[0052] <Example 1> (Manufacture of positive electrode plate) A mixed powder of a positive electrode active material was prepared by mixing large particles and small particles composed of lithium nickel composite oxide (Li 1.03 Ni 0.82 Co 0.05 Mn 0.11 O 2 ). The mixing ratio was “large particles / small particles = 6 / 4 (mass ratio)”. The D50 of the large particles was 17 μm, and the D50 of the small particles was 4 μm. A positive electrode slurry was prepared by mixing 97.6 parts by mass of the mixed powder, 1.5 parts by mass of a conductive material (carbon black), 0.9 parts by mass of a binder (PVdF), and a predetermined amount of a dispersion medium (N-methyl-2-pyrrolidone). The positive electrode slurry was applied to the surface of a positive electrode substrate (Al foil) at 350 (g / m 2) was applied in an application amount and dried, whereby a positive electrode active material layer was formed. The positive electrode active material layer was compressed by a rolling machine. As a result, a positive electrode raw sheet with a density of the positive electrode active material layer of 3.5 (g / cc) was manufactured. The positive electrode raw sheet was cut into a predetermined size to manufacture a positive electrode plate. A tab terminal (Al thin plate) was joined to the positive electrode plate.

[0053] (Manufacture of negative electrode plate) 98 parts by mass of a negative electrode active material (graphite, D50 = 17 μm, specific surface area = 1.2 m 2 / g), 1 part by mass of CMC, 1 part by mass of SBR, and a predetermined amount of a dispersion medium (water) were mixed to prepare a negative electrode slurry. The negative electrode slurry was applied to the surface of a negative electrode substrate (Cu foil) at an application amount of 225 (g / m 2 ) and dried, whereby a negative electrode active material layer with a specific surface area S of 2 (m 2 / g) was formed. The negative electrode active material layer was compressed by a rolling machine. As a result, a negative electrode raw sheet with a density of the negative electrode active material layer of 1.5 (g / cc) was manufactured. The negative electrode raw sheet was cut into a predetermined size to manufacture a negative electrode plate. A tab terminal (Ni thin plate) was joined to the negative electrode plate.

[0054] (Assembly) As a separator, a porous sheet made of polyolefin was prepared. The positive electrode plate, the separator, and the negative electrode plate were laminated so that the separator was interposed between the positive electrode plate and the negative electrode plate. By winding this, a wound electrode body was formed. As an exterior body, a pouch made of an Al laminate film was prepared. The electrode body was housed in the exterior body.

[0055] (Injection of electrolyte) An electrolyte was prepared. The electrolyte contained the following components. The electrolyte was injected into the exterior body in an amount of 2 (g / Ah). The exterior body was sealed. Thus, a test cell was manufactured.

[0056] Solvent: EC / EMC = 3 / 7 (volume ratio) Supporting electrolyte: LiPF 6 (1 mol / L) Additive: LiBOB (0.5% by mass fraction)

[0057] (Activation) Initial charge and discharge were carried out under a temperature environment of 25°C. With a current of 0.2 mA / cm 2 , the test cell was charged in a constant current mode until the positive electrode potential reached 4.30 V (vs. Li + / Li). Subsequently, the test cell was charged in a constant voltage mode until the current reached 0.04 mA / cm 2 . After a 10-minute pause, with a current of 0.2 mA / cm 2 , the test cell was discharged in a constant current mode until the positive electrode potential reached 2.5 V (vs. Li + / Li). In this example, in all test cells, the initial single-pole filling capacity was 80 Ah / m at the positive electrode 2 , 85 Ah / m at the negative electrode 2 , and the initial single-pole discharge capacity was 73.6 Ah / m at the positive electrode 2 , 78.2 Ah / m at the negative electrode 2 . Note that the current [mA / cm 2 in this example is normalized by the area of the positive electrode plate.

[0058] The following evaluations were performed on the test cells fabricated as described above. The results are shown in Table 1.

[0059] (Internal Resistance) Under a temperature environment of 25°C, the SOC (State of Charge) of the test cell was adjusted to 50% by constant current-constant voltage (CC-CV) charging (CC current = 1 / 3C, CV voltage = 3.7V, 1 / 20C cut-off). Subsequently, the temperature was adjusted by holding at -30°C for 5 hours or more. The cell was discharged for 10 seconds at current values of 0.1C, 0.2C, 0.3C, 0.4C, 0.5C, and 0.6C respectively, and the voltage was measured. After the voltage measurement at each current value, it was charged at 0.05C according to the discharge capacity, and after the SOC change was suppressed, it was paused for 30 minutes. The resistance was calculated by linear approximation from the I-V plot. In this example, the internal resistance of Comparative Example 1 is defined as 100. If the internal resistance is 120 or less, it is considered that the output characteristics are good.

[0060] (Boron content) The test cell was charged (0.05C, 4.2V cut-off) and discharged (0.05C, 3.0V cut-off), and then disassembled. As shown in FIG. 4, a wound electrode body having tabs 13 and 23, having a length L in the width direction of the active material layer, and having an upper R portion (curved portion on the upper side of the wound body) and a lower R portion (curved portion on the lower side of the wound body) was taken out. Tab 13 is a portion (base material) where no positive electrode active material layer is formed on the positive electrode plate, and tab 23 is a portion (base material) where no positive electrode active material layer is formed on the negative electrode plate. As shown in FIG. 5, a central region M2 was cut out from a portion corresponding to the outermost layer of the negative electrode plate in the taken-out negative electrode plate. Then, the negative electrode active material was peeled off in 10 ml of water, and a sample for measuring the boron content was collected. The center of the central region M2 was a region with a radius of 20 mm centered on the midpoint of L and h. L is the length of the short side of the negative electrode active material layer, and h is the distance between the apex of the upper R portion and the apex of the lower R portion of the electrode body in the negative electrode active material layer. 10 mL of hydrochloric acid was added to the water containing the sample for measuring the boron content, and heat treatment was performed at 80° C. for 30 minutes. The obtained aqueous solution was filtered through filter paper, water was added to the filter paper deposit, and the filter paper adherent was also recovered. Then, the volume of the recovered aqueous solution was made 100 mL, B-ICP measurement was performed, and the boron content M2 (mass %) of the central portion of the negative electrode active material layer was determined by the external calibration curve method.

[0061] Next, in the same manner as in the central region M2, the boron content was measured for the remaining 8 regions other than M2 surrounded by a circle shown in FIG. 4, and the average value of the boron content obtained from the 9 regions including M2 was defined as the average boron content M1 (mass %) of boron contained in the negative electrode active material layer.

[0062] (Specific surface area) The BET specific surface area of the negative electrode plate taken out from the electrode body disassembled in the measurement of the boron content was measured by the nitrogen adsorption method.

[0063] (Penetration test) The test cell was charged. The test battery was connected to the data logger. The data logger has a voltage measurement function and a current measurement function. A nail (manufactured by Daito Hunt Co., Ltd., round nail, body diameter = 3 mm) was prepared. The nail was inserted into the test battery. When a voltage drop was confirmed, the insertion of the nail was stopped. After the nail was stopped, the voltage and current were measured until a voltage rise was detected. The voltage drop is considered to indicate the occurrence of a short circuit. The voltage rise after the voltage drop is considered to indicate that the positive electrode substrate (Al foil) around the nail melted and spread due to the Joule heat of the short circuit, and the current was interrupted. The calorific value was calculated from the voltage, current, and time until the voltage rise was detected. The smaller the calorific value, the better the fusing performance is considered to be. In Table 1, the case where the calorific value is less than 35 W is indicated as ○, and the case where the calorific value is 35 W or more is indicated as ×.

[0064] <Examples 2 to 3 and Comparative Examples 1 to 5> As shown in Table 1, the test cells were each manufactured in the same manner as in Example 1, except that the composition ratio of the positive electrode active material, the type and specific surface area of the negative electrode active material, the specific surface area of the negative electrode active material layer, the content of LiBOB in the electrolytic solution, and the boron content were changed. The results are shown in Table 1.

[0065]

Table 1

[0066] In Examples 1 to 3, the increase in resistance was suppressed, and good results were obtained in the nail penetration test.

Explanation of Symbols

[0067] 10 Positive electrode plate, 11 Positive electrode substrate, 12 Positive electrode active material layer, 13, 23 Tab, 20 Negative electrode plate, 21 Negative electrode substrate, 22 Negative electrode active material layer, 30 Separator, 50 Electrode body, 71 Positive electrode current collector member, 72 Negative electrode current collector member, 81 Positive electrode terminal, 82 Negative electrode terminal, 90 Outer package, 91 Sealing plate, 92 Outer can, 100 Battery, M2 Central portion.

Claims

1. comprising an electrode body and an electrolytic solution, wherein the electrode body includes a positive electrode plate and a negative electrode plate, the positive electrode plate includes a positive electrode active material layer, the negative electrode plate includes a negative electrode active material layer, the positive electrode active material layer contains a positive electrode active material represented by formula (1): Li （１＋ｘ） Ni ｙ Ti ｚ Me （１－ｙ－ｚ） O ２ [In formula (1), Me includes two or more selected from the group consisting of Mn, Co, and Al, satisfying the relationships of 0 < x < 0.1, 0.8 < y < 0.85, and 0 ≦ z < 0.03] the negative electrode active material layer contains a negative electrode active material, when the specific surface area of the negative electrode active material layer is S, the average boron content of boron contained in the negative electrode active material layer is M1 (mass %), and the boron content of the central portion of the negative electrode active material layer is M2 (mass %), the following relational expressions: (a) M1 / S ≦ 0.1 (b) M2 ≧ 0.05 are satisfied, a non-aqueous electrolyte secondary battery.

2. The non-aqueous electrolyte secondary battery according to claim 1, wherein the length of the short side of the shape in plan view of one continuous negative electrode active material layer in the negative electrode plate is 80 mm or more and 400 mm or less. The electrode body has a total facing area of 3 m ２ or more, and

3. The non-aqueous electrolyte secondary battery according to claim 1, further satisfying the following relational expression: (c) 2 ≦ S ≦ 4

4. The non-aqueous electrolyte secondary battery according to claim 1, wherein the graphite content in the negative electrode active material is 99 mass % or more.

5. A method for manufacturing a non-aqueous electrolyte secondary battery, comprising: a step of inserting an electrode body into an exterior body, a step of injecting an electrolytic solution, and an activation step, wherein the electrode body includes a positive electrode plate and a negative electrode plate, the positive electrode plate includes a positive electrode active material layer, the negative electrode plate includes a negative electrode active material layer, the positive electrode active material layer contains a positive electrode active material represented by formula (1): [In formula (1), Me includes two or more selected from the group consisting of Mn, Co, and Al, Li （１＋ｘ） Ni ｙ Ti ｚ Me （１－ｙ－ｚ） O ２ satisfying the relationships of 0 < x < 0.1, 0.8 < y < 0.85, and 0 ≦ z < 0.03] the negative electrode active material layer contains a negative electrode active material, when the specific surface area of the negative electrode active material layer is S, the average boron content of boron contained in the negative electrode active material layer is M1 (mass %), and the boron content of the central portion of the negative electrode active material layer is M2 (mass %), the following relational expressions: (a) M1 / S ≦ 0.1 (b) M2 ≧ 0.05 are satisfied, a method for manufacturing a non-aqueous electrolyte secondary battery. ​ ​ ​

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