Electric storage device

Abstract

The electricity storage element includes a positive electrode, a negative electrode, a separator, and an electrolyte solution. The content (Vemc) of ethyl methyl carbonate in the electrolyte solution is 26.5-45.0 vol%. The ethylene carbonate content Vec in the electrolyte solution is 9.0-33.5 vol%. The content (Vdmc) of dimethyl carbonate in the electrolyte solution is 29.5-41.0 vol%. The diethyl carbonate content (Vdec) in the electrolyte solution is 0.0-0.2 vol%. The content (Vpc) of propylene carbonate in the electrolyte solution is 0.0-10.5 vol%. The content Vfec of fluoroethylene carbonate in the electrolyte solution is at least 0.0 vol%. The total of Vemc, Vec, Vdmc, Vdec, Vpc, and Vfec is 97.0 to 100 vol%.

Description

Technical Field

[0001] The present disclosure relates to an electric storage element. Background Art

[0002] Electricity storage devices such as lithium-ion secondary batteries are widely used as power sources for mobile devices such as mobile phones and notebook computers, as well as hybrid vehicles, etc. In recent years, there has been an increasing demand for large-scale electricity storage devices for stationary electricity storage devices and electric vehicles, and electricity storage devices are required to have high performance that combines high capacity with safety.

[0003] Using lithium cobalt oxide (LiCoO 2 ) As a positive electrode active material, lithium-ion secondary batteries have a high capacity. Since lithium cobalt oxide is easy to synthesize, it is widely used as a positive electrode active material. However, there are only a limited number of cobalt producing countries and the market price of cobalt is high. Therefore, materials that replace part of the cobalt in lithium cobalt oxide with nickel or manganese are being widely studied. In particular, replacing cobalt with nickel increases the capacity. Therefore, Li(Ni,Co)O in which part of the cobalt in lithium cobalt oxide is replaced by nickel is being studied. 2 As an alternative material to lithium cobalt oxide.

[0004] However, as the amount of nickel replacing cobalt increases, Li(Ni,Co)O 2 It behaves similarly to lithium nickel oxide (LiNiO 2 That is, as the amount of nickel replacing cobalt increases, Li(Ni,Co)O 2 The structure becomes unstable, and the cycle characteristics and temperature characteristics of the lithium-ion secondary battery deteriorate.

[0005] The following cited document 1 discloses a non-aqueous secondary battery, wherein the positive electrode active material layer comprises Li(Ni, Mn, Co)O 2 The positive electrode active material layer and the negative electrode active material layer each have a porosity within a specific range, the permeability of the separator is also within a specific range, and the electrolyte solution contains at least one selected from dimethyl carbonate, ethyl methyl carbonate and diethyl carbonate and ethylene carbonate. Reference 1 discloses that the non-aqueous secondary battery having these characteristics has excellent charge and discharge characteristics and high capacity at a large current.

[0006] The following reference 2 discloses a non-aqueous secondary battery, comprising: 2The invention discloses that the non-aqueous secondary battery having these characteristics has excellent rapid charge and discharge characteristics, charge and discharge cycle characteristics, and storage characteristics.

[0007] Prior art literature

[0008] Patent Literature

[0009] Patent Document 1: International Publication No. 2015 / 041167

[0010] Patent Document 2: International Publication No. 2015 / 037522 Summary of the invention

[0011] Problems to be solved by the invention

[0012] However, there is room for improvement in the cycle characteristics of conventional power storage devices at high temperatures.

[0013] One aspect of the present disclosure aims to provide a power storage device having excellent cycle characteristics.

[0014] Means used to solve problems

[0015] For example, one aspect of the present disclosure relates to the following power storage element.

[0016] [1] An electric storage element, wherein:

[0017] Including positive electrode, negative electrode, separator and electrolyte solution,

[0018] The positive electrode includes a first current collector and a first active material layer covering at least a portion of a main surface of the first current collector.

[0019] The negative electrode includes a second current collector and a second active material layer covering at least a portion of a main surface of the second current collector.

[0020] The first active material layer and the second active material layer face each other,

[0021] The separator is a porous insulator and is disposed between the first active material layer and the second active material layer.

[0022] The electrolyte solution is impregnated in the separator and is in contact with the first active material layer and the second active material layer.

[0023] The content Vemc of ethyl methyl carbonate (1) in the electrolyte solution is 26.5 volume % or more and 45.0 volume % or less,

[0024] The content Vec of ethylene carbonate (2) in the electrolyte solution is 9.0 volume % or more and 33.5 volume % or less,

[0025] The content Vdmc of dimethyl carbonate (3) in the electrolyte solution is 29.5 volume % or more and 41.0 volume % or less,

[0026] The content Vdec of diethyl carbonate (4) in the electrolyte solution is 0.0 volume % or more and 0.2 volume % or less,

[0027] The content Vpc of propylene carbonate (5) in the electrolyte solution is 0.0 volume % or more and 10.5 volume % or less,

[0028] The content Vfec of fluoroethylene carbonate (8) in the electrolyte solution is 0.0 volume % or more,

[0029] The total of Vemc, Vec, Vdmc, Vdec, Vpc, and Vfec is 97.0 volume % or more and 100 volume % or less.

[0030] [2] The energy storage device according to [1], wherein

[0031] Vemc is 27.0 volume % or more and 31.0 volume % or less,

[0032] Vec is 29.0 volume % or more and 33.0 volume % or less,

[0033] Vdmc is 37.0 volume % or more and 41.0 volume % or less,

[0034] Vdec is 0.02 volume % or more and 0.20 volume % or less,

[0035] The total of Vemc, Vec, Vdmc, and Vdec is 97.0% by volume or more and 100% by volume or less.

[0036] [3] The energy storage device according to [2], wherein

[0037] Vemc is smaller than Vec.

[0038] [4] The energy storage device according to [2] or [3], wherein

[0039] The content of vinylene carbonate (6) in the electrolyte solution is 0.03 mass % or more and 0.20 mass % or less.

[0040] [5] The energy storage device according to any one of [2] to [4], wherein

[0041] The content of propane sultone (7) in the electrolyte solution is 0.05 mass % or more and 0.20 mass % or less.

[0042] [6] The energy storage device according to [1], wherein

[0043] Vemc is 40.5 volume % or more and 44.5 volume % or less,

[0044] Vec is 9.3 volume % or more and 13.3 volume % or less,

[0045] Vdmc is 29.5 volume % or more and 33.5 volume % or less,

[0046] Vpc is 4.0 volume % or more and 8.0 volume % or less,

[0047] Vfec is 6.2 volume % or more and 10.8 volume % or less,

[0048] The total of Vemc, Vec, Vdmc, Vpc, and Vfec is greater than or equal to 97.0 volume % and less than or equal to 100 volume %.

[0049] [7] The energy storage device according to [6], wherein

[0050] The content of vinylene carbonate (6) in the electrolyte solution is 0.01 mass % or more and 0.10 mass % or less.

[0051] [8] The power storage element according to [6] or [7], wherein

[0052] The content of adiponitrile (9) in the electrolyte solution is 0.70 mass % or more and 4.70 mass % or less.

[0053] [9] The energy storage device according to [1], wherein

[0054] The electrolyte in the electrolyte solution comprises lithium hexafluorophosphate,

[0055] The total concentration of the electrolyte in the electrolyte solution is 1.05 mol / L or more and 1.60 mol / L or less.

[0056]

[10] The energy storage device according to [1], wherein

[0057] The electrolyte in the electrolyte solution comprises lithium hexafluorophosphate,

[0058] The total concentration of the electrolyte in the electrolyte solution is 1.21 mol / L or more and 1.41 mol / L or less.

[0059]

[11] The energy storage device according to any one of [2] to [5], wherein

[0060] The electrolyte in the electrolyte solution comprises lithium hexafluorophosphate,

[0061] The total concentration of the electrolyte in the electrolyte solution is 1.05 mol / L or more and 1.20 mol / L or less.

[0062]

[12] The power storage device according to any one of [6] to [8], wherein

[0063] The electrolyte in the electrolyte solution comprises lithium hexafluorophosphate,

[0064] The total concentration of the electrolyte in the electrolyte solution is 1.42 mol / L or more and 1.60 mol / L or less.

[0065]

[13] The energy storage device according to [1], wherein

[0066] The first active material layer contained in the positive electrode includes a metal oxide.

[0067] The metal oxides contain lithium, nickel, manganese and cobalt.

[0068] The amount of nickel in a metal oxide is expressed as [Ni] mol.

[0069] The amount of manganese in a metal oxide is denoted as [Mn] mol.

[0070] The amount of cobalt in a metal oxide is denoted as [Co] mol.

[0071] Among [Ni], [Mn] and [Co], [Ni] is the largest.

[0072] [Ni] / [Mn] is 1.55 or more and 2.15 or less,

[0073] [Ni] / [Co] is 2.20 or more and 2.60 or less.

[0074]

[14] The power storage device according to any one of [2] to [5] and

[11] , wherein

[0075] The first active material layer contained in the positive electrode includes a metal oxide.

[0076] The metal oxides contain lithium, nickel, manganese and cobalt.

[0077] The amount of nickel in a metal oxide is expressed as [Ni] mol.

[0078] The amount of manganese in a metal oxide is denoted as [Mn] mol.

[0079] The amount of cobalt in a metal oxide is denoted as [Co] mol.

[0080] Among [Ni], [Mn] and [Co], [Ni] is the largest.

[0081] [Ni] / [Mn] is 1.67 or more and 1.84 or less,

[0082] [Ni] / [Co] is 2.21 or more and 2.41 or less.

[0083]

[15] The energy storage device according to

[14] , wherein

[0084] The first active material layer included in the positive electrode further contains titanium and zirconium.

[0085]

[16] The energy storage element according to

[15] , wherein

[0086] The content of titanium in the first active material layer is expressed as TiO 2 The conversion is 0.084 mol% or more and 0.184 mol% or less.

[0087]

[17] The energy storage element according to

[15] or

[16] , wherein

[0088] The content of zirconium in the first active material layer is expressed as ZrO 2 The conversion is 0.095 mol% or more and 0.195 mol% or less.

[0089]

[18] The power storage device according to any one of [6] to [8] and

[12] , wherein

[0090] The first active material layer contained in the positive electrode includes a metal oxide.

[0091] The metal oxides contain lithium, nickel, manganese and cobalt.

[0092] The amount of nickel in a metal oxide is expressed as [Ni] mol.

[0093] The amount of manganese in a metal oxide is denoted as [Mn] mol.

[0094] The amount of cobalt in a metal oxide is denoted as [Co] mol.

[0095] Among [Ni], [Mn] and [Co], [Ni] is the largest.

[0096] [Ni] / [Mn] is 1.95 or more and 2.15 or less,

[0097] [Ni] / [Co] is 2.38 or more and 2.58 or less.

[0098]

[19] The power storage device according to any one of

[13] to

[18] , wherein

[0099] The first active material layer included in the positive electrode further includes at least one element selected from the group consisting of sodium, aluminum, chlorine, phosphorus, and sulfur.

[0100]

[20] The energy storage device according to [1], wherein

[0101] The first active material layer contained in the positive electrode includes a metal oxide.

[0102] The metal oxides contain lithium, nickel, manganese and cobalt.

[0103] The amount of nickel in a metal oxide is expressed as [Ni] mol.

[0104] The amount of manganese in a metal oxide is denoted as [Mn] mol.

[0105] The amount of cobalt in a metal oxide is denoted as [Co] mol.

[0106] Among [Ni], [Mn] and [Co], [Ni] is the largest.

[0107] [Ni] / [Mn] is 3.00 or more and 8.00 or less,

[0108] [Ni] / [Co] is 3.00 or more and 8.00 or less.

[0109]

[21] The power storage device according to any one of [1] to [8], wherein

[0110] The power storage element is a lithium ion secondary battery, a sodium ion secondary battery, a potassium ion secondary battery, a magnesium ion secondary battery or a calcium ion secondary battery.

[0111] Effects of the Invention

[0112] According to one aspect of the present disclosure, it is possible to provide a power storage element having excellent cycle characteristics. BRIEF DESCRIPTION OF THE DRAWINGS

[0113] Figure 1 A schematic cross section of an electric storage element (lithium ion secondary battery) according to an embodiment of the present disclosure is shown. Figure 1 The cross-section shown is approximately perpendicular to the major surfaces of each of the positive electrode, the negative electrode, and the separator. DETAILED DESCRIPTION

[0114] For example, one aspect of the present disclosure relates to the following power storage element.

[0115] [1] An electric storage element, wherein:

[0116] Including positive electrode, negative electrode, separator and electrolyte solution,

[0117] The positive electrode includes a first current collector and a first active material layer covering at least a portion of a main surface of the first current collector.

[0118] The negative electrode includes a second current collector and a second active material layer covering at least a portion of a main surface of the second current collector.

[0119] The first active material layer and the second active material layer face each other,

[0120] The separator is a porous insulator and is disposed between the first active material layer and the second active material layer.

[0121] The electrolyte solution is impregnated in the separator and is in contact with the first active material layer and the second active material layer.

[0122] The content Vemc of ethyl methyl carbonate (1) in the electrolyte solution is 26.5 volume % or more and 45.0 volume % or less,

[0123] The content Vec of ethylene carbonate (2) in the electrolyte solution is 9.0 volume % or more and 33.5 volume % or less,

[0124] The content Vdmc of dimethyl carbonate (3) in the electrolyte solution is 29.5 volume % or more and 41.0 volume % or less,

[0125] The content Vdec of diethyl carbonate (4) in the electrolyte solution is 0.0 volume % or more and 0.2 volume % or less,

[0126] The content Vpc of propylene carbonate (5) in the electrolyte solution is 0.0 volume % or more and 10.5 volume % or less,

[0127] The content Vfec of fluoroethylene carbonate (8) in the electrolyte solution is 0.0 volume % or more,

[0128] The total of Vemc, Vec, Vdmc, Vdec, Vpc, and Vfec is 97.0 volume % or more and 100 volume % or less.

[0129] [2] The energy storage device according to [1], wherein

[0130] Vemc is 27.0 volume % or more and 31.0 volume % or less,

[0131] Vec is 29.0 volume % or more and 33.0 volume % or less,

[0132] Vdmc is 37.0 volume % or more and 41.0 volume % or less,

[0133] Vdec is 0.02 volume % or more and 0.20 volume % or less,

[0134] The total of Vemc, Vec, Vdmc, and Vdec is 97.0% by volume or more and 100% by volume or less.

[0135] [3] The energy storage device according to [2], wherein

[0136] Vemc is smaller than Vec.

[0137] [4] The energy storage device according to [2] or [3], wherein

[0138] The content of vinylene carbonate (6) in the electrolyte solution is 0.03 mass % or more and 0.20 mass % or less.

[0139] [5] The energy storage device according to any one of [2] to [4], wherein

[0140] The content of propane sultone (7) in the electrolyte solution is 0.05 mass % or more and 0.20 mass % or less.

[0141] [6] The energy storage device according to [1], wherein

[0142] Vemc is 40.5 volume % or more and 44.5 volume % or less,

[0143] Vec is 9.3 volume % or more and 13.3 volume % or less,

[0144] Vdmc is 29.5 volume % or more and 33.5 volume % or less,

[0145] Vpc is 4.0 volume % or more and 8.0 volume % or less,

[0146] Vfec is 6.2 volume % or more and 10.8 volume % or less,

[0147] The total of Vemc, Vec, Vdmc, Vpc, and Vfec is greater than or equal to 97.0 volume % and less than or equal to 100 volume %.

[0148] [7] The energy storage device according to [6], wherein

[0149] The content of vinylene carbonate (6) in the electrolyte solution is 0.01 mass % or more and 0.10 mass % or less.

[0150] [8] The power storage element according to [6] or [7], wherein

[0151] The content of adiponitrile (9) in the electrolyte solution is 0.70 mass % or more and 4.70 mass % or less.

[0152] [9] The energy storage device according to [1], wherein

[0153] The electrolyte in the electrolyte solution comprises lithium hexafluorophosphate,

[0154] The total concentration of the electrolyte in the electrolyte solution is 1.05 mol / L or more and 1.60 mol / L or less.

[0155]

[10] The energy storage device according to [1], wherein

[0156] The electrolyte in the electrolyte solution comprises lithium hexafluorophosphate,

[0157] The total concentration of the electrolyte in the electrolyte solution is 1.21 mol / L or more and 1.41 mol / L or less.

[0158]

[11] The energy storage device according to any one of [2] to [5], wherein

[0159] The electrolyte in the electrolyte solution comprises lithium hexafluorophosphate,

[0160] The total concentration of the electrolyte in the electrolyte solution is 1.05 mol / L or more and 1.20 mol / L or less.

[0161]

[12] The power storage device according to any one of [6] to [8], wherein

[0162] The electrolyte in the electrolyte solution comprises lithium hexafluorophosphate,

[0163] The total concentration of the electrolyte in the electrolyte solution is 1.42 mol / L or more and 1.60 mol / L or less.

[0164]

[13] The energy storage device according to [1], wherein

[0165] The first active material layer contained in the positive electrode includes a metal oxide.

[0166] The metal oxides contain lithium, nickel, manganese and cobalt.

[0167] The amount of nickel in a metal oxide is expressed as [Ni] mol.

[0168] The amount of manganese in a metal oxide is denoted as [Mn] mol.

[0169] The amount of cobalt in a metal oxide is denoted as [Co] mol.

[0170] Among [Ni], [Mn] and [Co], [Ni] is the largest.

[0171] [Ni] / [Mn] is 1.55 or more and 2.15 or less,

[0172] [Ni] / [Co] is 2.20 or more and 2.60 or less.

[0173]

[14] The power storage device according to any one of [2] to [5] and

[11] , wherein

[0174] The first active material layer contained in the positive electrode includes a metal oxide.

[0175] The metal oxides contain lithium, nickel, manganese and cobalt.

[0176] The amount of nickel in a metal oxide is expressed as [Ni] mol.

[0177] The amount of manganese in a metal oxide is denoted as [Mn] mol.

[0178] The amount of cobalt in a metal oxide is denoted as [Co] mol.

[0179] Among [Ni], [Mn] and [Co], [Ni] is the largest.

[0180] [Ni] / [Mn] is 1.67 or more and 1.84 or less,

[0181] [Ni] / [Co] is 2.21 or more and 2.41 or less.

[0182]

[15] The energy storage device according to

[14] , wherein

[0183] The first active material layer included in the positive electrode further contains titanium and zirconium.

[0184]

[16] The energy storage element according to

[15] , wherein

[0185] The content of titanium in the first active material layer is expressed as TiO 2 The conversion is 0.084 mol% or more and 0.184 mol% or less.

[0186]

[17] The energy storage element according to

[15] or

[16] , wherein

[0187] The content of zirconium in the first active material layer is expressed as ZrO 2 The conversion is 0.095 mol% or more and 0.195 mol% or less.

[0188]

[18] The power storage device according to any one of [6] to [8] and

[12] , wherein

[0189] The first active material layer contained in the positive electrode includes a metal oxide.

[0190] The metal oxides contain lithium, nickel, manganese and cobalt.

[0191] The amount of nickel in a metal oxide is expressed as [Ni] mol.

[0192] The amount of manganese in a metal oxide is denoted as [Mn] mol.

[0193] The amount of cobalt in a metal oxide is denoted as [Co] mol.

[0194] Among [Ni], [Mn] and [Co], [Ni] is the largest.

[0195] [Ni] / [Mn] is 1.95 or more and 2.15 or less,

[0196] [Ni] / [Co] is 2.38 or more and 2.58 or less.

[0197]

[19] The power storage device according to any one of

[13] to

[18] , wherein

[0198] The first active material layer included in the positive electrode further includes at least one element selected from the group consisting of sodium, aluminum, chlorine, phosphorus, and sulfur.

[0199]

[20] The energy storage device according to [1], wherein

[0200] The first active material layer contained in the positive electrode includes a metal oxide.

[0201] The metal oxides contain lithium, nickel, manganese and cobalt.

[0202] The amount of nickel in a metal oxide is expressed as [Ni] mol.

[0203] The amount of manganese in a metal oxide is denoted as [Mn] mol.

[0204] The amount of cobalt in a metal oxide is denoted as [Co] mol.

[0205] Among [Ni], [Mn] and [Co], [Ni] is the largest.

[0206] [Ni] / [Mn] is 3.00 or more and 8.00 or less,

[0207] [Ni] / [Co] is 3.00 or more and 8.00 or less.

[0208]

[21] The power storage device according to any one of [1] to [8], wherein

[0209] The power storage element is a lithium ion secondary battery, a sodium ion secondary battery, a potassium ion secondary battery, a magnesium ion secondary battery or a calcium ion secondary battery.

[0210] Hereinafter, as one embodiment of the present disclosure, a lithium ion secondary battery as a type of power storage element will be described with reference to the drawings. However, the present disclosure is not limited to the following embodiment.

[0211] (Overview of lithium-ion secondary battery)

[0212] like Figure 1 As shown, the lithium ion secondary battery 100 involved in this embodiment includes a positive electrode 10, a negative electrode 20, a separator 18, an electrolyte solution 19, a positive electrode lead 62, a negative electrode lead 60 and a shell 50. The positive electrode 10, the negative electrode 20, the separator 18 and the electrolyte solution 19 constitute a storage unit 30. The shell 50 that accommodates the storage unit 30 is sealed. The storage unit 30 is electrically insulated from the inner wall of the shell 50. The positive electrode lead 62 and the negative electrode lead 60 are electrically insulated from each other and from the shell 50. The positive electrode 10, the negative electrode 20 and the separator 18 can each be a plate, a layer, a laminate or a film. The lithium ion secondary battery 100 may also include a plurality of storage units 30.

[0213] The positive electrode 10 includes a first current collector 12 (positive electrode current collector) and a first active material layer 14 (positive electrode active material layer) covering a portion or the entirety of the main surface of the first current collector 12. The first active material layer 14 may also cover only one of a pair of main surfaces (front surface and back surface) possessed by the first current collector 12. The first active material layer 14 may also cover both sides of a pair of main surfaces possessed by the first current collector 12. "Main surface" refers to the surface with the largest area among the multiple surfaces possessed by a polyhedron (such as the first current collector 12). The first end of the positive lead 62 is electrically connected to the positive electrode 10 (first current collector 12), and the second end of the positive lead 62 is arranged on the outside of the shell 50.

[0214] The negative electrode 20 includes a second current collector 22 (negative electrode current collector) and a second active material layer 24 (negative electrode active material layer) covering a portion or the entirety of the main surface of the second current collector 22. The second active material layer 24 may cover only one of a pair of main surfaces (front surface and back surface) of the second current collector 22. The second active material layer 24 may cover both of a pair of main surfaces of the second current collector 22. One end of the negative electrode lead 60 is electrically connected to the negative electrode 20 (second current collector 22), and the other end of the negative electrode lead 60 is disposed outside the case 50.

[0215] The first active material layer 14 and the second active material layer 24 are opposite to each other. The separator 18 is a porous insulator and is disposed between the first active material layer 14 and the second active material layer 24. In other words, the separator 18 is sandwiched between the positive electrode 10 and the negative electrode 20 to separate the positive electrode 10 and the negative electrode 20. The electrolyte solution 19 is impregnated in the separator 18 and is in contact with the first active material layer 14 and the second active material layer 24. The electrolyte solution 19 and the electrolyte in the electrolyte solution 19 pass through the separator 18 through the pores formed in the separator 18.

[0216] Feature (A): The content Vemc of ethyl methyl carbonate (1) in the electrolyte solution 19 is 26.5 volume % or more and 45.0 volume % or less.

[0217] Feature (B): The content Vec of ethylene carbonate (2) in the electrolyte solution 19 is 9.0 volume % or more and 33.5 volume % or less.

[0218] Feature (C): The content Vdmc of dimethyl carbonate (3) in the electrolyte solution 19 is 29.5% by volume or more and 41.0% by volume or less.

[0219] Feature (D): The content Vdec of diethyl carbonate (4) in the electrolyte solution 19 is 0.0 volume % or more and 0.2 volume % or less.

[0220] Feature (E): The content Vpc of propylene carbonate (5) in the electrolyte solution 19 is 0.0 volume % or more and 10.5 volume % or less.

[0221] Feature (F): The content Vfec of fluoroethylene carbonate (8) in the electrolyte solution 19 is 0.0 volume % or more.

[0222] Feature (G): The total of Vemc, Vec, Vdmc, Vdec, Vpc, and Vfec is 97.0% by volume or more and 100% by volume or less.

[0223] In addition, in the present disclosure, in order to simplify the description related to the composition of the electrolyte solution 19, the symbols of Vemc, Vec, Vdmc, Vdec, Vpc, Vfec, and Vfec are used.

[0224] Ethyl methyl carbonate (1), ethylene carbonate (2), dimethyl carbonate (3), diethyl carbonate (4), propylene carbonate (5) and fluoroethylene carbonate (8) are all organic solvents (non-aqueous solvents) that dissolve electrolytes.

[0225] When the total of Vemc, Vec, Vdmc, Vdec, Vpc and Vfec is less than 100% by volume, the remainder after removing ethyl methyl carbonate (1), ethylene carbonate (2), dimethyl carbonate (3), diethyl carbonate (4), propylene carbonate (5) and fluoroethylene carbonate (8) from the electrolyte solution 19 may be at least one of other organic solvents, electrolytes, various additives and inevitable impurities. For example, the electrolyte solution 19 may further contain additives such as vinylene carbonate (6), propane sultone (7), and adiponitrile (9).

[0226] Since the electrolyte solution 19 has characteristics (A), (B), (C), (D), (E), (F) and (G), the cycle characteristics of the lithium ion secondary battery 100 used at high temperatures (for example, temperatures above 60°C) are improved. Cycle characteristics refer to the property of suppressing the reduction in capacity that occurs with repeated charge and discharge of the lithium ion secondary battery 100. "Cycle characteristics" can also be renamed as "capacity retention rate". "Improvement in cycle characteristics" can also be renamed as "increase in capacity retention rate". In addition, Vfec can be greater than 0.0 volume % and less than 11.0 volume %.

[0227] When the total of Vemc, Vec, Vdmc, Vdec, Vpc, and Vfec is less than 97.0 vol % and the content Vemc of ethyl methyl carbonate (1) is too small, the viscosity of the electrolyte solution 19 increases, and thus the conductivity tends to decrease.

[0228] When the total of Vemc, Vec, Vdmc, Vdec, Vpc, and Vfec is less than 97.0 vol % and the content Vec of ethylene carbonate (2) is too small, the relative dielectric constant of the electrolyte solution 19 tends to decrease.

[0229] When the total of Vemc, Vec, Vdmc, Vdec, Vpc, and Vfec is less than 97.0 vol % and the content Vdmc of dimethyl carbonate (3) is too small, the viscosity of the electrolyte solution 19 increases, and thus there is a tendency for the conductivity to decrease.

[0230] The electrolyte in the electrolyte solution 19 may include lithium hexafluorophosphate (LiPF 6 ), the total concentration of the electrolyte in the electrolyte solution 19 may be 1.05 mol / L or more and 1.60 mol / L or less, or 1.21 mol / L or more and 1.41 mol / L or less. 6When the total concentration of the electrolytes is within the above range, the cycle characteristics of the lithium-ion secondary battery 100 at high temperatures can be easily improved. The conductivity of the electrolyte solution 19 varies depending on the concentration of the electrolyte. When the concentration of the electrolyte is too low, sufficient conductivity cannot be obtained, and when the concentration of the electrolyte is too high, the conductivity will also decrease. The concentration of the electrolyte at which the conductivity becomes extremely high will vary depending on the type or mixing ratio of the electrolyte and the solvent. The electrolyte solution 19 in the present disclosure exhibits particularly high conductivity in the range of 1.05 mol / L or more and 1.60 mol / L or less. The electrolyte in the electrolyte solution 19 is not limited to LiPF 6 For example, the electrolyte may be selected from LiPF 6 、LiClO 4 , LiBF 4 、LiCF 3 SO 3 、LiCF 3 CF 2 SO 3 、LiC(CF 3 SO 2 ) 3 、LiN(CF 3 SO 2 ) 2 、LiN(CF 3 CF 2 SO 2 ) 2 、LiN(CF 3 SO 2 )(C 4 F 9 SO 2 )、LiN(CF 3 CF 2 CO) 2 and at least one lithium compound (lithium salt) of LiBOB.

[0231] The first active material layer 14 (active material layer for positive electrode) may contain a metal oxide as an active material, and the metal oxide may contain lithium, nickel, manganese and cobalt. The amount of nickel in the metal oxide is marked as [Ni] mol. The amount of manganese in the metal oxide is marked as [Mn] mol. The amount of cobalt in the metal oxide is marked as [Co] mol. Among [Ni], [Mn] and [Co], [Ni] may be the largest. [Ni] / [Mn] may be greater than 1.55 and less than 2.15, and [Ni] / [Co] may be greater than 2.20 and less than 2.60. Alternatively, [Ni] / [Mn] may be greater than 3.00 and less than 8.00, and [Ni] / [Co] may be greater than 3.00 and less than 8.00. The inventors' research results found that when the first active material layer 14 contains a metal oxide in which a portion of the cobalt in lithium cobalt oxide is replaced by manganese and nickel, the cycle characteristics of the lithium-ion secondary battery 100 at high temperature can be easily improved by using an electrolyte solution 19 having characteristics (A), (B), (C), (D), (E), (F) and (G).

[0232] In the case where [Ni] / [Mn] and [Ni] / [Co] of the metal oxide contained in the first active material layer 14 are respectively within the above ranges, the cycle characteristics of the lithium ion secondary battery 100 including the electrolyte solution 19 at high temperatures are easily improved.

[0233] For example, the metal oxide contained in the first active material layer 14 may be represented by the following Chemical Formula 1.

[0234] LiNi x Mn y Co z M a O 2 (1)

[0235] The units of x, y, z and a in Chemical Formula 1 are each molar. x, y, z and a in Chemical Formula 1 satisfy x+y+z+a=1. x in Chemical Formula 1 satisfies 0<x<1. y in Chemical Formula 1 satisfies 0<y<1. z in Chemical Formula 1 satisfies 0<z<1. a in Chemical Formula 1 satisfies 0≤a<1. M in Chemical Formula 1 is at least one element selected from Al, Mg, Nb, Ti, Cu, Zn and Cr. x / y calculated from x and y in Chemical Formula 1 is equal to [Ni] / [Mn]. x / z calculated from x and z in Chemical Formula 1 is equal to [Ni] / [Co].

[0236] The positive electrode active material contained in the first active material layer 14 is not limited to the metal oxide represented by Chemical Formula 1. For example, the positive electrode active material contained in the first active material layer 14 may be selected from LiNi xCo y Mn z M a O 2 、 lithium nickelate (LiNiO 2 ), lithium manganate (LiMnO 2 ), lithium cobaltate (LiCoO 2 ), lithium manganese spinel (LiMn 2 O 4 ), lithium vanadium compound (LiV 2 O 5 ), olivine-type LiMPO 4 (where M in LiMPO 4 is at least one element selected from Co, Ni, Mn, Fe, Mg, Nb, Ti, Al, and Zr or VO), lithium titanate (Li 4 Ti 5 O 12 ), and LiNi x Co y Al z O 2 (where x, y, and z in LiNi x Co y Al z O 2 satisfy 0.9 < x + y + z < 1.1), and at least one of the lithium compounds thereof.

[0237] The first active material layer 14 may further contain at least one element selected from sodium, aluminum, chlorine, phosphorus, and sulfur. For example, at least one element selected from sodium, aluminum, chlorine, phosphorus, and sulfur may be an inevitable impurity derived from at least one of the separator 18 and the electrolyte solution 19. For example, sodium in the first active material layer 14 may be derived from the electrolyte, the active material for the positive electrode, or the impurity sodium contained together with lithium in these raw materials. For example, aluminum in the first active material layer 14 may be the aluminum contained in the separator 18 in contact with the first active material layer 14. For example, through side reactions associated with the charge and discharge of the lithium ion secondary battery 100 (the lithium ion secondary battery 100 before the housing 50 is sealed) before leaving the factory, excess gas may be generated from the electrolyte solution 19, and an SEI film (Solid Electrolyte Interphase film) may be formed on the surface of the first active material layer 14. Along with these side reactions, chlorine, phosphorus, or sulfur derived from the electrolyte solution 19 may be incorporated into the first active material layer 14.

[0238] The first active material layer 14 may further include at least one selected from the following conductive materials (conductive aids): conductive carbon such as graphite, acetylene black and carbon black; metal powders such as copper, nickel, stainless steel and iron; conductive polymers such as polyacetylene, polyaniline, polypyrrole, polythiophene and polyphenylene; and conductive oxides such as ITO.

[0239] The first active material layer 14 may further include a binder. For example, the binder may be at least one compound selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-hexafluoropropylene type fluororubber (VDF-HFP type fluororubber), vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene type fluororubber (VDF-HFP-TFE type fluororubber), polyethylene, polypropylene, polyethylene terephthalate, aromatic polyamide, cellulose, styrene-butadiene rubber, isoprene rubber, butadiene rubber, ethylene-propylene rubber, styrene-butadiene-styrene block copolymer and its hydrogenated product, styrene-ethylene-butadiene-styrene copolymer, styrene-isoprene-styrene block copolymer and its hydrogenated product, syndiotactic 1,2-polybutadiene, ethylene-vinyl acetate copolymer, propylene-α-olefin copolymer, and conductive polymer.

[0240] For example, the negative electrode active material contained in the second active material layer 24 may be at least one selected from the following compounds: natural graphite, artificial graphite, carbon materials such as non-graphitizable carbon, graphitizable carbon, and low-temperature calcined carbon; metals that form compounds with lithium (such as Al and Sn), amorphous compounds such as tin oxide; lithium titanate (Li 4 Ti 5 O 12 ) and TiO 2 . The negative electrode active material may be a simple substance of silicon, an alloy containing silicon, or a compound containing silicon (oxide or silicate, etc.). For example, the silicon-containing alloy may contain at least one element selected from tin (Sn), nickel (Ni), copper (Cu), iron (Fe), cobalt (Co), manganese (Mn), zinc (Zn), indium (In), silver (Ag), titanium (Ti), germanium (Ge), bismuth (Bi), antimony (Sb) and chromium (Cr). For example, the silicon-containing compound may contain at least one element selected from boron (B), nitrogen (N), oxygen (O) and carbon (C). For example, the negative electrode active material containing silicon may be selected from SiB 4 、SiB 6 Mg 2 Si、Ni 2 Si、TiSi 2 、MoSi 2 、CoSi 2 、NiSi 2 、CaSi2 CrSi 2 , Cu 5 Si、FeSi 2 、MnSi 2 、NbSi 2 、TaSi 2 、VSi 2 , WSi 2 、ZnSi 2 、SiC、Si 2 N 2 、Si 2 N 2 O、SiO X (SiO X The negative electrode active material may be fibers (such as nanowires) containing silicon or particles (such as nanoparticles) containing silicon.

[0241] The second active material layer 24 may further include at least one conductive material (conductive aid). The second active material layer 24 may further include at least one binder (adhesive).

[0242] The first current collector 12 (current collector for the positive electrode) may be a known conductor. The second current collector 22 (current collector for the negative electrode) may also be a known conductor. For example, the first current collector 12 and the second current collector 22 may be metal foils made of copper or aluminum, respectively. The surfaces of the first current collector 12 and the second current collector 22 may be treated by plating. For example, the surface of each current collector treated by plating may contain nickel. In addition to nickel, the surface of each current collector treated by plating may also contain at least one element selected from carbon, phosphorus and tungsten. For example, the positive lead 62 and the negative lead 60 may be metals such as copper or aluminum.

[0243] For example, the porous separator 18 may be a nonwoven fabric, a film, or a laminate. For example, the separator 18 may be composed of a polymer having electrical insulation properties. For example, the separator 18 may contain at least one polymer selected from polyethylene, polypropylene, polyolefin, polyester, and cellulose.

[0244] For example, the housing 50 may be made of a metal such as aluminum or stainless steel. The housing 50 may be made of a laminated film formed of a metal layer and a resin layer.

[0245] There is no particular limitation on the use of storage elements such as the lithium-ion secondary battery 100. For example, the storage element can be used for: power supplies for mobile devices such as mobile phones, smart watches, and laptop computers; power sources for transportation equipment such as electric vehicles and hybrid vehicles; and stationary storage devices. The size and shape of the lithium-ion secondary battery 100 can be changed according to various uses and are not limited. For example, the thickness of each of the first current collector 12 and the second current collector 22 can be more than a few μm and less than tens of μm. For example, the thickness of each of the first active material layer 14 and the second active material layer 24 can be more than a few μm and less than hundreds of μm. For example, the thickness of the separator 18 can be more than a few μm and less than hundreds of μm. The sizes of the main surfaces of the first current collector 12, the separator 18, and the second current collector 22 can be substantially the same as each other. For example, the width of the main surface of each of the first current collector 12, the separator 18, and the second current collector 22 can be more than tens of mm and less than hundreds of mm. For example, when the lithium ion secondary battery 100 is a wound-type battery, the maximum width of each main surface of the first current collector 12 , the separator 18 , and the second current collector 22 may be approximately several thousand mm.

[0246] For example, the volatile components in the electrolyte solution 19 can be analyzed and determined by high performance gas chromatography (High Performance Gas Chromatography) and mass spectrometry. For example, the supporting salt (electrolyte) can be analyzed and determined by coupled plasma (Inductively Coupled Plasma) emission spectrometry. For example, the non-volatile components in the electrolyte solution 19 can be analyzed and determined by NMR (Nuclear Magnetic Resonance). For example, the composition of each active material layer and each collector can be analyzed and determined by methods such as inductively coupled plasma emission spectrometry.

[0247] [Lithium ion secondary battery including electrolyte solution A]

[0248] Hereinafter, a lithium ion secondary battery including electrolyte solution A as a specific example of electrolyte solution 19 is described. Electrolyte solution A corresponds to a part of the multiple examples described in [2] to [5],

[11] and

[14] to

[17] described above and in Tables 3, 4, 8, 10 and 11 described later.

[0249] The content Vemc of ethyl methyl carbonate (1) in the electrolyte solution A may be 27.0% by volume or more and 31.0% by volume or less.

[0250] The content Vec of ethylene carbonate (2) in the electrolyte solution A may be 29.0% by volume or more and 33.0% by volume or less.

[0251] The content Vdmc of dimethyl carbonate (3) in the electrolyte solution A may be 37.0% by volume or more and 41.0% by volume or less.

[0252] The content Vdec of diethyl carbonate (4) in the electrolyte solution A may be 0.02% by volume or more and 0.20% by volume or less.

[0253] The total of Vemc, Vec, Vdmc, and Vdec in the electrolyte solution A may be 97.0% by volume or more and 100% by volume or less.

[0254] By including the electrolyte solution A in the lithium ion secondary battery, the cycle characteristics of the lithium ion secondary battery at high temperatures are easily improved.

[0255] In the electrolyte solution A, Vemc may be smaller than Vec. In the case where Vemc is smaller than Vec in the electrolyte solution A, the cycle characteristics of the lithium ion secondary battery including the electrolyte solution A at high temperature are easily improved.

[0256] The content Mvc of vinylene carbonate (6) in the electrolyte solution can be greater than 0.03 mass % and less than 0.20 mass %. Through vinylene carbonate (6), a thin SEI film is easily formed on the surface of the negative electrode (second active material layer), which easily suppresses the decomposition of the electrolyte solution A (non-aqueous solvent) on the surface of the negative electrode. When the content Mvc of vinylene carbonate (6) in the electrolyte solution A is within the above range, the cycle characteristics of the lithium ion secondary battery 100 including the electrolyte solution A at high temperature are easily improved. For the same reason, the content Mvc of vinylene carbonate (6) in the electrolyte solution 19 having characteristics (A), (B), (C), (D), (E), (F) and (G) can also be greater than 0.03 mass % and less than 0.20 mass %.

[0257] The content Mps of propane sultone (7) in the electrolyte solution A can be 0.05 mass % or more and 0.20 mass % or less. With propane sultone (7), a thin SEI film is easily formed on the surface of the negative electrode, and the decomposition of the electrolyte solution A (non-aqueous solvent) on the surface of the negative electrode is easily suppressed. When the content Mps of propane sultone (7) in the electrolyte solution A is 0.05 mass % or more and 0.20 mass % or less, the cycle characteristics of the lithium ion secondary battery 100 including the electrolyte solution A at high temperature are easily improved. For the same reason, the content Mps of propane sultone (7) in the electrolyte solution 19 having the characteristics (A), (B), (C), (D), (E), (F) and (G) can also be 0.05 mass % or more and 0.20 mass % or less.

[0258] The electrolyte in the electrolyte solution A may include lithium hexafluorophosphate (LiPF 6 ), the total concentration of the electrolyte in the electrolyte solution A may be 1.05 mol / L or more and 1.20 mol / L or less. 6 When the total concentration of the electrolytes is 1.05 mol / L or more and 1.20 mol / L or less, the high temperature cycle characteristics of the lithium ion secondary battery 100 including the electrolyte solution A are easily improved. However, the electrolyte in the electrolyte solution A is not limited to LiPF 6 , the electrolyte solution A may also contain LiPF 6 Other electrolytes.

[0259] In the case where the lithium ion secondary battery includes the electrolyte solution A, the [Ni] / [Mn] in the metal oxide (active material) contained in the first active material layer 14 (active material layer for positive electrode) may be 1.67 or more and 1.84 or less, and the [Ni] / [Co] in the metal oxide may be 2.21 or more and 2.41 or less. When [Ni] / [Mn] and [Ni] / [Co] are respectively within the above ranges, the cycle characteristics of the lithium ion secondary battery 100 including the electrolyte solution A at high temperatures are easily improved.

[0260] In the case where the lithium ion secondary battery includes the electrolyte solution A, the first active material layer (positive electrode active material layer) may further include titanium and zirconium. For example, the first active material layer may further include TiO 2 and ZrO 2. When the first active material layer further contains titanium and zirconium, the effect of suppressing the decomposition of the electrolyte solution caused by the side reaction on the surface of the first active material layer can be obtained. For the same reason, when the electrolyte solution 19 having the characteristics (A), (B), (C), (D), (E), (F) and (G) is contained in a lithium ion secondary battery, the first active material layer may further contain titanium and zirconium.

[0261] In the case where the lithium ion secondary battery includes the electrolyte solution A, the content of titanium in the first active material layer (positive electrode active material layer) is expressed as TiO 2 The conversion can be 0.084 mol% or more and 0.184 mol% or less, or 0.10 mol% or more and 0.150 mol% or less. When the content of titanium in the first active material layer is within the above range, the cycle characteristics of the lithium ion secondary battery 100 including the electrolyte solution A at high temperature are easily improved. For the same reason, when the electrolyte solution 19 having the characteristics (A), (B), (C), (D), (E), (F) and (G) is included in the lithium ion secondary battery, the content of titanium in the first active material layer can also be within the above range.

[0262] In the case where the lithium ion secondary battery includes the electrolyte solution A, the content of zirconium in the first active material layer (positive electrode active material layer) is expressed as ZrO 2 The conversion can be 0.095 mol% or more and 0.195 mol% or less, or 0.10 mol% or more and 0.150 mol% or less. When the content of zirconium in the first active material layer is within the above range, the cycle characteristics of the lithium ion secondary battery 100 including the electrolyte solution A at high temperature are easily improved. For the same reason, when the electrolyte solution 19 having the characteristics (A), (B), (C), (D), (E), (F) and (G) is included in the lithium ion secondary battery, the content of zirconium in the first active material layer can also be within the above range.

[0263] [Lithium ion secondary battery including electrolyte solution B]

[0264] Hereinafter, a lithium ion secondary battery including an electrolyte solution B is described, wherein the electrolyte solution B is a specific example of the electrolyte solution 19 having the characteristics (A), (B), (C), (D), (E), (F), and (G). The lithium ion secondary battery including the electrolyte solution B corresponds to a part of the multiple embodiments described in the above-mentioned [6] to [8],

[12] and

[18] and in Tables 5, 6, 9, and 10 described later.

[0265] The content Vemc of ethyl methyl carbonate (1) in the electrolyte solution B may be 40.5% by volume or more and 44.5% by volume or less.

[0266] The content Vec of ethylene carbonate (2) in the electrolyte solution B may be 9.3% by volume or more and 13.3% by volume or less.

[0267] The content Vdmc of dimethyl carbonate (3) in the electrolyte solution B may be 29.5% by volume or more and 33.5% by volume or less.

[0268] The content Vpc of propylene carbonate (5) in the electrolyte solution B may be 4.0% by volume or more and 8.0% by volume or less.

[0269] The content Vfec of fluoroethylene carbonate (8) in the electrolyte solution B may be 6.2% by volume or more and 10.8% by volume or less.

[0270] The total of Vemc, Vec, Vdmc, Vpc, and Vfec in the electrolyte solution B may be 97.0% by volume or more and 100% by volume or less.

[0271] By including the electrolyte solution B, the cycle characteristics of the lithium ion secondary battery at high temperatures are easily improved.

[0272] The content Mvc of vinylene carbonate (6) in the electrolyte solution B can be greater than 0.01 mass % and less than 0.10 mass %. Through vinylene carbonate (6), a thin SEI film is easily formed on the surface of the negative electrode (second active material layer), which easily inhibits the decomposition of the electrolyte solution B (non-aqueous solvent) on the surface of the negative electrode. When the content Mvc of vinylene carbonate (6) in the electrolyte solution B is greater than 0.01 mass % and less than 0.10 mass %, the cycle characteristics of the lithium ion secondary battery 100 including the electrolyte solution B at high temperature are easily improved. For the same reason, the content Mvc of vinylene carbonate (6) in the electrolyte solution 19 having characteristics (A), (B), (C), (D), (E), (F) and (G) can also be greater than 0.01 mass % and less than 0.10 mass %.

[0273] The content Madn of adiponitrile (9) in the electrolyte solution B may be 0.70 mass % or more and 4.70 mass % or less. Adiponitrile (9) makes it easy to stabilize the structure of the lithium compound (active material for the positive electrode) contained in the positive electrode (first active material layer), to suppress the side reaction between the positive electrode (first active material layer) and the electrolyte solution B, to extend the life of the lithium ion secondary battery charged at a high voltage, and to stabilize the cycle characteristics of the lithium ion secondary battery at high temperature. When the content Madn of adiponitrile (9) in the electrolyte solution B is 0.70 mass % or more and 4.70 mass % or less, the cycle characteristics of the lithium ion secondary battery 100 including the electrolyte solution B at high temperature are easily improved. For the same reason, the content Madn of adiponitrile (9) in the electrolyte solution 19 having the characteristics (A), (B), (C), (D), (E), (F) and (G) may be 0.70 mass % or more and 4.70 mass % or less.

[0274] The electrolyte in the electrolyte solution B may include lithium hexafluorophosphate (LiPF 6 ), the total concentration of the electrolyte in the electrolyte solution B may be 1.42 mol / L or more and 1.60 mol / L or less. 6 When the total concentration of the electrolytes is 1.42 mol / L or more and 1.60 mol / L or less, the high temperature cycle characteristics of the lithium ion secondary battery 100 including the electrolyte solution B are easily improved. However, the electrolyte in the electrolyte solution B is not limited to LiPF 6 , the electrolyte solution B may also contain LiPF 6 Other electrolytes.

[0275] In the case where the lithium ion secondary battery includes the electrolyte solution B, the [Ni] / [Mn] in the metal oxide (active material) contained in the first active material layer 14 (active material layer for positive electrode) may be 1.95 or more and 2.15 or less, and the [Ni] / [Co] in the metal oxide may be 2.38 or more and 2.58 or less. When [Ni] / [Mn] and [Ni] / [Co] are respectively within the above ranges, the cycle characteristics of the lithium ion secondary battery 100 including the electrolyte solution B at high temperatures are easily improved.

[0276] However, the present disclosure is not necessarily limited to the above-described embodiments. Various modifications can be made to the present disclosure without departing from the gist of the present disclosure, and these modifications are also included in the present disclosure.

[0277] For example, the structure of a lithium-ion secondary battery is not limited to Figure 1The structure shown. For example, the lithium-ion secondary battery can be a wound battery. The wound battery includes a stacked body in which a first separator, a positive electrode, a second separator and a negative electrode are stacked in sequence, and the wound stacked body is contained in a shell. The positive electrode of the wound battery includes a first current collector and a first active material layer covering the two main surfaces of the first current collector. The negative electrode of the wound battery includes a second current collector and a second active material layer covering the two main surfaces of the second current collector. The electrolyte solution of the wound battery is impregnated in the first separator and the second separator, respectively.

[0278] For example, the storage element is not limited to a lithium ion secondary battery, and may be, for example, a sodium ion secondary battery, a potassium ion secondary battery, a magnesium ion secondary battery, or a calcium ion secondary battery.

[0279] Example

[0280] The present disclosure is described in detail by the following examples and comparative examples. The present disclosure is not limited to the following examples.

[0281] (Example 1)

[0282] <Manufacturing of lithium-ion secondary batteries>

[0283] The lithium ion battery of Example 1 was produced by the following method.

[0284] As the positive electrode active material contained in the first active material layer, a metal oxide represented by the following chemical formula 2 is used. In the following chemical formula 2, x is 6 / 10. In the following chemical formula 2, y is 2 / 10. In the following chemical formula 2, z is also 2 / 10. x+y+z is 1. x / y (i.e., [Ni] / [Mn]) is 3. x / z (i.e., [Ni] / [Co]) is also 3.

[0285] LiNi x Mn y Co z O 2 (2)

[0286] LiNi x Mn y Co z O 2 , a conductive aid, a binder and a solvent are mixed to prepare a positive electrode coating (raw material for the first active material layer). The positive electrode coating is applied to the main surface of the first current collector. The first current collector covered with the positive electrode coating is dried and rolled. Through the above steps, a positive electrode consisting of a first active material layer and a first current collector is obtained. Carbon black is used as a conductive aid. Polyvinylidene fluoride is used as a binder. N-methyl-2-pyrrolidone is used as a solvent. Aluminum foil is used as the first current collector. LiNi x Mn yCo z O 2 The ratio of the mass of the conductive additive to the mass of the adhesive is 95.0:2.0:3.0.

[0287] In addition to replacing LiNi x Mn y Co z O 2 In addition to using graphite, the negative electrode coating (raw material of the second active material layer) is prepared by the same method as the positive electrode coating. The negative electrode coating is applied to the main surface of the second current collector. Copper foil is used as the second current collector. The second current collector covered with the negative electrode coating is dried and rolled. Through the above steps, a negative electrode consisting of the second active material layer and the second current collector is obtained.

[0288] The separator is sandwiched between the first active material layer and the second active material layer, and the positive electrode, the negative electrode and the separator are stacked in sequence to obtain a storage unit. The positive electrode, the negative electrode and the separator are fixed to each other by a hot melt adhesive. A porous film made of polyolefin is used as a separator. The dimensions of the main surfaces of the positive electrode, the negative electrode and the separator are approximately the same. The positive lead is connected to the positive electrode (the first collector) by ultrasonic welding. The negative lead is connected to the negative electrode (the second collector) by the same method. Aluminum foil is used as the positive lead. Nickel foil is used as the negative lead. A polymer for improving the airtightness of the shell is bonded to the ends of the positive lead and the negative lead.

[0289] The storage unit is contained in the shell, and the electrolyte solution is injected into the shell. In a state where the ends of the positive lead and the negative lead, which are insulated from each other, are arranged outside the shell, the interior of the shell is degassed, whereby the storage unit and the electrolyte solution are sealed in the shell. The shell is a laminated film composed of a metal layer and a resin layer. Through the above process, the lithium ion secondary battery of Example 1 is obtained.

[0290] The electrolyte contained in the electrolyte solution of Example 1 is lithium hexafluorophosphate (LiPF 6 ). LiPF in the electrolyte solution of Example 1 6 The concentration is 1.0 mol / L.

[0291] The composition of the electrolyte solution of Example 1 is shown in Table 1 below.

[0292] Vemc described in the following Tables 1 to 9 refers to the content of ethyl methyl carbonate (1) in the electrolyte solution (unit: volume %).

[0293] Vec described in the following Tables 1 to 9 refers to the content of ethylene carbonate (2) in the electrolyte solution (unit: volume %).

[0294] Vdmc described in the following Tables 1 to 9 refers to the content of dimethyl carbonate (3) in the electrolyte solution (unit: volume %).

[0295] Vdec described in the following Tables 1 to 9 refers to the content of diethyl carbonate (4) in the electrolyte solution (unit: volume %).

[0296] Vpc described in the following Tables 1 to 9 refers to the content of propylene carbonate (5) in the electrolyte solution (unit: volume %).

[0297] Vfec described in the following Tables 1 to 9 refers to the content (unit: volume %) of fluoroethylene carbonate (8) in the electrolyte solution.

[0298] Mvc described in the following Tables 1 to 9 refers to the content (unit: mass %) of vinylene carbonate (6) in the electrolyte solution.

[0299] Mps described in the following Tables 1 to 9 refers to the content (unit: mass %) of propane sultone (7) in the electrolyte solution.

[0300] Madn described in the following Tables 1 to 9 refers to the content of adiponitrile (9) in the electrolyte solution (unit: mass %).

[0301] SUM1 described in the following Tables 1 to 9 refers to the total of Vemc, Vec, Vdmc, Vdec, Vpc, and Vfec (unit: volume %).

[0302] SUM2 described in the following Tables 3 and 4 refers to the total of Vemc, Vec, Vdmc, and Vdec (unit: volume %).

[0303] SUM6 described in the following Tables 5 and 6 refers to the total of Vemc, Vec, Vdmc, Vpc, and Vfec (unit: volume %).

[0304] <Determination of Capacity Retention Rate>

[0305] The charge and discharge cycle of the lithium ion secondary battery of Example 1 was repeated 500 times. The discharge rate was maintained at 0.5 C. The temperature of the lithium ion secondary battery during the charge and discharge cycle was maintained at 60° C. The capacity retention rate R defined by the following mathematical formula 1 was measured. CAPACITY (Unit: %) C in the following mathematical formula 1 INITIAL C is the discharge capacity per unit mass of the lithium ion secondary battery measured in the first charge and discharge cycle (unit: mA·h / g). FINAL It is the discharge capacity per unit mass of the lithium ion secondary battery measured at the 500th charge and discharge cycle. The capacity retention rate of Example 1 is shown in Table 1 below.

[0306] R CAPACITY =(C FINAL / C INITIAL )×100(1)

[0307] A described in the "Evaluation" column of the following Tables 1 to 11 means a capacity maintenance rate of 80% or more.

[0308] B described in the "Evaluation" column of the following Tables 1 to 11 means a capacity maintenance rate of 75% or more and less than 80%.

[0309] C described in the "Evaluation" column of the following Tables 1 to 11 means a capacity maintenance rate of 70% or more and less than 75%.

[0310] D described in the "Evaluation" column of the following Tables 1 to 11 means a capacity maintenance rate of 65% or more and less than 70%.

[0311] E described in the "Evaluation" column of the following Tables 1 to 11 means a capacity maintenance rate of 60% or more and less than 65%.

[0312] F described in the "Evaluation" column of the following Tables 1 to 11 means a capacity maintenance rate of 55% or more and less than 60%.

[0313] G described in the "Evaluation" column of the following Tables 1 to 11 means a capacity retention rate of 40% or less.

[0314] (Examples 2 to 79, 131 and 132, and Comparative Examples 1 to 12)

[0315] The composition of the electrolyte solution of each of Examples 2 to 79, 131 and 132, and Comparative Examples 1 to 12 is shown in Tables 1 to 6 below. Except for the composition of the electrolyte solution, the lithium ion secondary batteries of each of Examples 2 to 79, 131 and 132, and Comparative Examples 1 to 12 were prepared by the same method as Example 1. The capacity retention rate of the lithium ion secondary batteries of each of Examples 2 to 79, 131 and 132, and Comparative Examples 1 to 12 was measured by the same method as Example 1. The capacity retention rate of the lithium ion secondary batteries of each of Examples 2 to 79, 131 and 132, and Comparative Examples 1 to 12 is shown in Tables 1 to 6 below.

[0316] (Examples 80 to 106)

[0317] [LiPF 6 ] refers to LiPF in the electrolyte solution 6 The concentration of LiPF in the electrolyte solutions of Examples 80 to 106 is (unit: mol / L). 6 The concentrations were adjusted to the values ​​shown in Tables 7 to 9 below.

[0318] The electrolyte solutions of Examples 80 to 88 in Table 7 below differ from the electrolyte solution of Example 2 only in that LiPF 6 The concentration is different.

[0319] The electrolyte solutions of Examples 89 to 97 in Table 8 below differ from the electrolyte solution of Example 46 only in that LiPF 6 The concentration is different.

[0320] The electrolyte solutions of Examples 98 to 106 in Table 9 below differ from the electrolyte solution of Example 79 only in that LiPF 6 The concentration is different.

[0321] Except for the above matters, lithium ion secondary batteries of Examples 80 to 106 were prepared in the same manner as in Example 1. The capacity retention rate of the lithium ion secondary batteries of Examples 80 to 106 was measured in the same manner as in Example 1. The capacity retention rate of the lithium ion secondary batteries of Examples 80 to 106 is shown in Tables 7 to 9 below.

[0322] (Examples 107 to 130)

[0323] LiNi of Examples 107 to 130 x Mn y Co z O 2 The x / y (i.e., [Ni] / [Mn]) in Examples 107 to 130 was adjusted to the values ​​shown in Tables 10 and 11 below. x Mn y Co z O 2 The x / z (i.e., [Ni] / [Co]) in the formula is adjusted to the values ​​shown in Tables 10 and 11 below.

[0324] [Ti] in Tables 10 and 11 below is the content of titanium in the first active material layer (unit: mol%), which is converted into TiO 2 The titanium content.

[0325] [Zr] in Tables 10 and 11 below is the content of zirconium in the first active material layer (unit: mol%), which is converted into ZrO 2 The zirconium content.

[0326] TiO was added to the raw material of the first active material layer in each of Examples 122 to 130. 2 and ZrO 2At least one of the following. The titanium content in the first active material layer of each of Examples 122 to 130 was adjusted to the value shown in Table 11 below. The zirconium content in the first active material layer of each of Examples 122 to 130 was adjusted to the value shown in Table 11 below.

[0327] The electrolyte solution of each of Examples 107 to 130 is the same as the electrolyte solution of the Examples described in the column "Electrolyte solution" in Tables 10 and 11 below.

[0328] Except for the above matters, the lithium ion secondary batteries of Examples 107 to 130 were prepared in the same manner as in Example 1. The capacity retention rates of the lithium ion secondary batteries of Examples 107 to 130 were measured in the same manner as in Example 1. The capacity retention rates of the lithium ion secondary batteries of Examples 107 to 130 are shown in Tables 10 and 11 below.

[0329]

[0330]

[0331]

[0332]

[0333]

[0334]

[0335]

[0336]

[0337]

[0338] [Table 10]

[0339]

[0340] [Table 11]

[0341]

[0342] [Industrial Applicability]

[0343] For example, the power storage element involved in one aspect of the present disclosure can be used as a power source for mobile devices such as mobile phones, smart watches, and laptop computers; a power source for transportation equipment such as electric vehicles and hybrid vehicles; and a stationary power storage device.

[0344] [Explanation of Reference Numerals]

[0345] 10 positive electrode, 12 first current collector, 14 first active material layer, 18 separator, 19 electrolyte solution, 20 negative electrode, 22 second current collector, 24 second active material layer, 30 power storage unit, 50 casing, 60 negative electrode lead, 62 positive electrode lead, 100 lithium ion secondary battery (power storage element).

Claims

1. A power storage element, wherein: It has a positive electrode, a negative electrode, a separator and an electrolyte solution. The positive electrode includes a first current collector and a first active material layer covering at least a portion of a main surface of the first current collector. The negative electrode includes a second current collector and a second active material layer covering at least a portion of a main surface of the second current collector. The first active material layer and the second active material layer face each other via the separator, The separator is a porous insulator and is disposed between the first active material layer and the second active material layer. The electrolyte solution is impregnated in the separator and is in contact with the first active material layer and the second active material layer. The content Vemc of ethyl methyl carbonate in the electrolyte solution is greater than or equal to 26.5% by volume and less than or equal to 45.0% by volume, The content Vec of ethylene carbonate in the electrolyte solution is 9.0 volume % or more and 33.5 volume % or less, The content Vdmc of dimethyl carbonate in the electrolyte solution is 29.5 volume % or more and 41.0 volume % or less, The content Vdec of diethyl carbonate in the electrolyte solution is greater than or equal to 0.0% by volume and less than or equal to 0.2% by volume, The content Vpc of propylene carbonate in the electrolyte solution is greater than or equal to 0.0 volume % and less than or equal to 10.5 volume %, The content Vfec of fluoroethylene carbonate in the electrolyte solution is 0.0 volume % or more, The total of the Vemc, the Vec, the Vdmc, the Vdec, the Vpc, and the Vfec is greater than or equal to 97.0 volume % and less than or equal to 100 volume %.

2. The electric storage element according to claim 1, wherein The Vemc is 27.0 volume % or more and 31.0 volume % or less, The Vec is 29.0 volume % or more and 33.0 volume % or less, The Vdmc is 37.0 volume % or more and 41.0 volume % or less, The Vdec is 0.02 volume % or more and 0.20 volume % or less, The total of the Vemc, the Vec, the Vdmc, and the Vdec is greater than or equal to 97.0 volume % and less than or equal to 100 volume %.

3. The electric storage element according to claim 2, wherein: The Vemc is smaller than the Vec.

4. The electric storage element according to claim 2, wherein: The content of vinylene carbonate in the electrolyte solution is 0.03 mass % or more and 0.20 mass % or less.

5. The electric storage element according to claim 2, wherein The content of propane sultone in the electrolyte solution is 0.05 mass % or more and 0.20 mass % or less.

6. The electric storage element according to claim 1, wherein The Vemc is 40.5 volume % or more and 44.5 volume % or less, The Vec is 9.3 volume % or more and 13.3 volume % or less, The Vdmc is 29.5 volume % or more and 33.5 volume % or less, The Vpc is greater than or equal to 4.0% by volume and less than or equal to 8.0% by volume, The Vfec is greater than or equal to 6.2 volume % and less than or equal to 10.8 volume %, The total of the Vemc, the Vec, the Vdmc, the Vpc, and the Vfec is greater than or equal to 97.0 volume % and less than or equal to 100 volume %.

7. The electric storage element according to claim 6, wherein The content of vinylene carbonate in the electrolyte solution is 0.01 mass % or more and 0.10 mass % or less.

8. The electric storage element according to claim 6, wherein The content of adiponitrile in the electrolyte solution is 0.70 mass % or more and 4.70 mass % or less.

9. The electric storage element according to claim 1, wherein The electrolyte in the electrolyte solution comprises lithium hexafluorophosphate, The total concentration of the electrolyte in the electrolyte solution is 1.05 mol / L or more and 1.60 mol / L or less.

10. The electric storage element according to claim 1, wherein The electrolyte in the electrolyte solution comprises lithium hexafluorophosphate, The total concentration of the electrolyte in the electrolyte solution is 1.21 mol / L or more and 1.41 mol / L or less.

11. The electric storage element according to claim 2, wherein The electrolyte in the electrolyte solution comprises lithium hexafluorophosphate, The total concentration of the electrolyte in the electrolyte solution is 1.05 mol / L or more and 1.20 mol / L or less.

12. The electric storage element according to claim 6, wherein The electrolyte in the electrolyte solution comprises lithium hexafluorophosphate, The total concentration of the electrolyte in the electrolyte solution is 1.42 mol / L or more and 1.60 mol / L or less.

13. The electric storage element according to claim 1, wherein The first active material layer contained in the positive electrode includes a metal oxide. The metal oxide comprises lithium, nickel, manganese and cobalt, The amount of nickel in the metal oxide is indicated as [Ni] mol, The amount of manganese in the metal oxide is indicated as [Mn] mol, The amount of cobalt in the metal oxide is indicated as [Co] mol, Among the [Ni], the [Mn] and the [Co], the [Ni] is the largest. [Ni] / [Mn] is 1.55 or more and 2.15 or less, [Ni] / [Co] is 2.20 or more and 2.60 or less.

14. The electric storage element according to claim 2, wherein The first active material layer contained in the positive electrode includes a metal oxide. The metal oxide comprises lithium, nickel, manganese and cobalt, The amount of nickel in the metal oxide is indicated as [Ni] mol, The amount of manganese in the metal oxide is indicated as [Mn] mol, The amount of cobalt in the metal oxide is indicated as [Co] mol, Among the [Ni], the [Mn] and the [Co], the [Ni] is the largest. [Ni] / [Mn] is 1.67 or more and 1.84 or less, [Ni] / [Co] is 2.21 or more and 2.41 or less.

15. The electric storage element according to claim 14, wherein The first active material layer included in the positive electrode further includes titanium and zirconium.

16. The electric storage element according to claim 15, wherein The content of the titanium in the first active material layer is 0.084 mol % or more and 0.184 mol % or less in terms of TiO 2 .

17. The electric storage element according to claim 15, wherein The content of the zirconium in the first active material layer is 0.095 mol % or more and 0.195 mol % or less in terms of ZrO 2 .

18. The electric storage element according to claim 6, wherein The first active material layer contained in the positive electrode includes a metal oxide. The metal oxide comprises lithium, nickel, manganese and cobalt, The amount of nickel in the metal oxide is indicated as [Ni] mol, The amount of manganese in the metal oxide is indicated as [Mn] mol, The amount of cobalt in the metal oxide is indicated as [Co] mol, Among the [Ni], the [Mn] and the [Co], the [Ni] is the largest. [Ni] / [Mn] is 1.95 or more and 2.15 or less, [Ni] / [Co] is 2.38 or more and 2.58 or less.

19. The electric storage element according to claim 13, wherein The first active material layer included in the positive electrode further includes at least one element selected from the group consisting of sodium, aluminum, chlorine, phosphorus, and sulfur.

20. The electric storage element according to claim 1, wherein The first active material layer contained in the positive electrode includes a metal oxide. The metal oxide comprises lithium, nickel, manganese and cobalt, The amount of nickel in the metal oxide is indicated as [Ni] mol, The amount of manganese in the metal oxide is indicated as [Mn] mol, The amount of cobalt in the metal oxide is indicated as [Co] mol, Among the [Ni], the [Mn] and the [Co], the [Ni] is the largest. [Ni] / [Mn] is 3.00 or more and 8.00 or less, [Ni] / [Co] is 3.00 or more and 8.00 or less.

21. The electric storage element according to claim 1, wherein The power storage element is a lithium ion secondary battery, a sodium ion secondary battery, a potassium ion secondary battery, a magnesium ion secondary battery, or a calcium ion secondary battery.

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