Lithium secondary battery

Abstract

The purpose of the present invention is to provide a lithium secondary battery excellent in cycle characteristics and temperature stability of a tab. The present invention relates to a lithium secondary battery provided with: a laminate including a plurality of negative electrodes, a plurality of separators, and a plurality of positive electrodes; a plurality of negative electrode tab lead parts extending from the laminate; and a negative electrode tab joined to the plurality of negative electrode tab lead parts. In the negative electrode tab lead part, a negative electrode current collector constituting the negative electrode extends from the laminate, and the negative electrode tab lead part and the negative electrode current collector include a resin layer, and copper layers formed on both surfaces of the resin layer. In a 2θ pattern of an X-ray diffraction measurement of the copper layers, there is at least a peak A of 42.9-43.9 degrees, and the ratio (B / A) of the intensity of a peak B which is 50.0-51.0 degrees with respect to the intensity of the peak A is 0.3 or less, and the half-value width of the peak A is 0.2 degrees or less.

Description

Lithium secondary battery

[0001] The present invention relates to a lithium secondary battery.

[0002] In recent years, technology for converting natural energy such as solar or wind power into electrical energy has been attracting attention. Accordingly, various secondary batteries have been developed as electricity storage devices that are highly safe and capable of storing a large amount of electrical energy.

[0003] Among them, lithium secondary batteries, which are charged and discharged by the movement of lithium ions between a positive electrode and a negative electrode, are known to exhibit high voltage and high energy density. A typical lithium secondary battery is a lithium-ion secondary battery (LIB), which has active materials capable of retaining lithium elements in the positive electrode and the negative electrode, and is charged and discharged by the exchange of lithium ions between the positive electrode active material and the negative electrode active material.

[0004] For example, Patent Document 1 discloses an electricity storage device comprising: an anode, a cathode, at least one separator disposed between the anode and the cathode, an electrolyte, at least one thin-film current collector in contact with at least one of the anode and the cathode, and at least one tab attached to the at least one thin-film current collector; the tab is attached to the current collector via a connection means, which electrically connects the exposed surface of the tab to the thin-film current collector; one of the anode and the cathode is interposed between at least a portion of the thin-film current collector and the separator; the current collector comprises a conductive material covering a non-conductive material substrate; and at the operating voltage of the electricity storage device, the current collector stops conduction upon short circuit, and the voltage is at least 2.0 volts.

[0005] Furthermore, Patent Document 2 discloses a current collector having a multilayer structure in which an insulating layer is sandwiched between conductive layers, characterized in that the current collector has a folded region in which the end portion is folded back two or more times in the same direction, the conductive layers sandwiching the insulating layer in the folded region are electrically connected to each other, and the inner surfaces of the current collector ends forming the folded region are spaced apart or partially in contact with each other.

[0006] Furthermore, Patent Document 3 discloses a lithium ion secondary battery having a positive electrode and a negative electrode formed by adhering an active material to a current collector via a binder, characterized in that the current collector of at least one of the positive electrode and the negative electrode comprises a low-melting point layer made of a resin that melts when the battery abnormally heats up, and a metal layer interposed between the low-melting point layer and the active material and exchanging electric charges with the active material.

[0007] Japanese Patent Publication No. 2022-527140 Publication No. 2013-016321 Publication No. 11-102711

[0008] Conventionally, pure copper foil or copper alloy foil has often been used in the negative electrode to ensure electrical conductivity. However, recently, from the viewpoints of safety and light weight, current collector films in which metal layers are formed on both sides of a resin film have been often used in current collectors, as described in Patent Documents 1 to 3. However, when multiple current collector leads made of such current collector films are welded to a tab, the cycle characteristics of the lithium secondary battery may be reduced due to the weld strength and connection resistance of the weld, and further, the temperature of the tab may increase during charge and discharge.

[0009] The present invention has been made in view of the above circumstances, and has as its object to provide a lithium secondary battery that has excellent cycle characteristics and temperature stability of the tab when ultrasonic welding is performed on the current collector film.

[0010] A lithium secondary battery according to one embodiment of the present invention includes: a laminate including a plurality of negative electrodes, a plurality of separators, and a plurality of positive electrodes; a plurality of negative electrode tab lead portions extending from the laminate; and a plurality of negative electrode tabs joined to the negative electrode tab lead portions, wherein the negative electrode tab lead portion is a negative electrode current collector constituting the negative electrode extending from the laminate, and the negative electrode tab lead portion and the negative electrode current collector include a resin layer and copper layers formed on both sides of the resin layer, and a 2θ pattern obtained by X-ray diffraction measurement of the copper layer has at least a peak A in an angle of 42.9° or more and 43.9° or less, and a ratio (B / A) of an intensity of a peak B in an angle of 50.0° or more and 51.0° or less to an intensity of the peak A is 0.3 or less, and a half width of the peak A is 0.2° or less.

[0011] According to the present invention, a lithium secondary battery having excellent cycle characteristics and temperature stability of the tab can be provided.

[0012] FIG. 1 is a schematic diagram showing an example of a lithium secondary battery of the present invention. FIG. 2 is a schematic diagram showing an example of a negative electrode of the present invention. FIG. 3 is a schematic diagram showing an example of a cross section of a negative electrode of the present invention. FIG. 4 is a schematic diagram showing an example of joining a negative electrode lead portion and a negative electrode tab in a lithium secondary battery of the present invention. FIG. 5 is a schematic diagram showing an example of joining a negative electrode lead portion and a negative electrode tab in a lithium secondary battery of the present invention. FIG. 6 is a schematic diagram showing an example of joining a negative electrode lead portion and a negative electrode tab in a lithium secondary battery of the present invention. FIG. 7 is a schematic diagram showing an example of joining a negative electrode lead portion and a negative electrode tab in a lithium secondary battery of the present invention. FIG. 8 is a schematic diagram showing an example of a lithium secondary battery of the present invention. FIG. 9 shows a 2θ pattern of X-ray diffraction measurement of Example 3. FIG. 10 shows a 2θ pattern of X-ray diffraction measurement of Example 4. FIG. 11 shows a 2θ pattern of X-ray diffraction measurement of Example 5. FIG. 12 shows a 2θ pattern of X-ray diffraction measurement of Comparative Example 4.

[0013] Hereinafter, a mode for carrying out the present invention (hereinafter simply referred to as "the present embodiment") will be described in detail, but the present invention is not limited to the following embodiment. The present invention can be modified in various ways without departing from the gist of the present invention. In the drawings, the same elements are given the same reference numerals, and redundant explanations will be omitted. Furthermore, positional relationships such as up, down, left, and right are based on the positional relationships shown in the drawings unless otherwise specified. Furthermore, the dimensional ratios of the drawings are not limited to those shown in the drawings.

[0014] 1. Lithium Secondary Battery The basic configuration of a lithium secondary battery according to one embodiment of the present invention will be described with reference to Figure 1. As shown in Figure 1, the lithium secondary battery according to one embodiment of the present invention includes a plurality of negative electrodes 10, a plurality of separators 20, and a plurality of positive electrodes 30, and the negative electrodes 10 and the positive electrodes 30 are arranged to be spaced apart via the separators 20. Each component will be described in detail below.

[0015] 1.1. Negative Electrode FIG. 2 is a perspective view showing an example of a negative electrode 10 of this embodiment. As shown in FIG. 2, the negative electrode 10 of this embodiment has a negative electrode main body 101 and a negative electrode tab lead portion 102. The negative electrode tab lead portion 102 is formed by extending the negative electrode current collector constituting the negative electrode 10 from the negative electrode main body 101. The negative electrode 10 includes a negative electrode current collector and may further include a negative electrode active material. Furthermore, as shown in FIG. 3, when the negative electrode 10 of this embodiment is composed only of a negative electrode current collector, it is composed of a negative electrode current collector film including a resin layer 202 and copper layers 201 formed on both sides of the resin layer 202.

[0016] 4 , the negative electrode tab 11 is overlapped with a negative electrode tab lead portion stack 12, which is a collection of negative electrode tab lead portions 102 that are the negative electrode side end portion of the battery stack A, and joined by welding. Examples of welding include ultrasonic welding, laser welding, resistance welding, and spot welding. Among these, ultrasonic welding is suitable and preferable for the lithium secondary battery of this embodiment, since it is necessary to weld the stack including the resin layer 202.

[0017] The lithium secondary battery of this embodiment includes a plurality of negative electrodes 10, a plurality of negative electrode tab lead portions 102 extending from the laminate, and a negative electrode tab 11 joined to the plurality of negative electrode tab lead portions. The negative electrode tab lead portion 102 is a main body portion of a negative electrode current collector constituting the negative electrode 10 extending from the laminate. The negative electrode main body portion of the negative electrode current collector and the negative electrode tab lead portion 102 include a resin layer 202 and a copper layer 201 formed on both sides of the resin layer 202. In a 2θ pattern obtained by X-ray diffraction measurement of the copper layer 201, the copper layer 201 has at least a peak A in an angle of 42.9° or more and 43.9° or less, and the ratio (B / A) of the intensity of peak B in an angle of 50.0° or more and 51.0° or less to the intensity of peak A is 0.3 or less, and the half width of peak A is 0.2° or less.

[0018] In a lithium secondary battery configured as a laminate in which each component is stacked, electricity is extracted from the lithium secondary battery by joining the negative electrode laminate to a tab terminal from the negative electrode lead portion of each negative electrode current collector. Here, ultrasonic welding, laser welding, resistance welding, spot welding, etc. are used as a method for joining the electrode lead portion to the tab terminal, but when a current collector film having a resin layer 202 and copper layers 201 formed on both sides of the resin layer 202 is used, ultrasonic welding is often used because no current flows through the resin layer 202.

[0019] However, the present inventors have found that even when ultrasonic welding is performed under the same conditions, depending on the specifications of the current collector film, the connection resistance increases due to factors such as partial welding, leaving room for improvement in the performance of the lithium secondary battery and the temperature stability of the tab during charge and discharge. After extensive research into this point, they have found that when the 2θ pattern of X-ray diffraction measurement of the copper layer 201 has at least a peak A between 42.9° and 43.9°, the ratio of the intensity of peak B between 50.0° and 51.0° to the intensity of peak A (B / A) is 0.3 or less, and the half-width of peak A is 0.2° or less, the performance of the lithium secondary battery and the temperature stability of the tab during charge and discharge are also improved. The reasons for this are presumed to be, but are not limited to, the following.

[0020] Peak A indicates the orientation of the (111) plane in the copper layer 201, and Peak B indicates the orientation of the (200) plane. When the intensity of Peak B relative to the intensity of Peak A is 0.3° or less and the half-width of Peak A is 0.2° or less, the orientation and crystallinity of the (111) plane are maximized while suppressing the orientation of the (200) plane. Because the (111) plane is a slip plane of copper with a face-centered cubic lattice structure, shear deformation and plastic deformation are likely to occur. This is presumably why welding using ultrasonic lateral vibrations is advantageous and the connection resistance between the negative electrode tab 11 and the negative electrode tab lead portion 102 is reduced. Therefore, the lithium secondary battery of this embodiment is considered to have excellent cycle characteristics and tab temperature stability during charge and discharge. However, the factors behind this are not limited to those described above.

[0021] In this specification, the half width is the value of the width of 2θ at exactly half the height of the maximum value of the peak in the 2θ pattern of X-ray diffraction measurement, and is called Full Width at Half Maximum in English, or FWHM.

[0022] The negative electrode current collector of this embodiment includes a resin layer 202 and a copper layer 201 formed on both sides of the resin layer 202. Figure 3 is a schematic diagram showing an example cross section of a negative electrode 10 including the resin layer 202 and the copper layer 201 formed on both sides of the resin layer 202.

[0023] The thickness of the negative electrode current collector film of this embodiment is preferably 2.2 μm to 30 μm, 3.0 μm to 15 μm, 3.5 μm to 13 μm, or 5.0 μm to 10 μm. By setting the thickness of the negative electrode current collector film within the above ranges, the ease of ultrasonic welding is improved, and the cycle characteristics of the battery and / or the temperature stability of the tab tend to be improved.

[0024] The resin layer 202 preferably contains at least one selected from the group consisting of polyethylene terephthalate (PET), polypropylene, polyamide, acrylic resin, polycarbonate, polyethylene, polyvinyl chloride, and polystyrene. Furthermore, the resin layer 202 is more preferably made of polyethylene terephthalate or polypropylene. Using the above-described resin layer 202 tends to improve ease of ultrasonic welding and improve the cycle characteristics of the battery and / or the temperature stability of the tab.

[0025] The resin layer 202 is preferably in the form of a film (sheet), and its thickness is preferably from 2.0 μm to 20 μm, from 3.0 μm to 10 μm, or from 4.0 μm to 7.0 μm. By setting the thickness of the resin layer 202 within the above range, the ease of ultrasonic welding is improved, and the cycle characteristics of the battery and / or the temperature stability of the tab tend to be improved.

[0026] In the negative electrode current collector of this embodiment, copper (Cu) layers 201 are formed as conductive layers on both sides of a resin layer 202. The copper layers 201 of this embodiment have a Cu element content of 99% by mass or more, 99.9% by mass or more, 99.99% by mass or more, or 99.9999% by mass or more.

[0027] In the 2θ pattern of X-ray diffraction measurement of copper layer 201, there is at least a peak A between 42.9° and 43.9°, but there may also be a peak A between 43.0° and 43.8°, or between 43.1° and 43.7°. The copper layer 201 having peak A means that a (111) plane is formed. Furthermore, in copper layer 201, the half-width of peak A is 0.2° or less, preferably less than 0.2°, and more preferably 0.18° or less. A half-width within this range means that the crystallinity of the (111) crystal plane is high, and by using a negative electrode current collector including copper layer 201 exhibiting such orientation, the cycle characteristics of the battery and the temperature stability of the tab are improved.

[0028] In addition, in the 2θ pattern of the copper layer 201, the ratio (B / A) of the intensity of Peak B at 50.0° to 51.0° to the intensity of Peak A is 0.3 or less, preferably 0.25 or less, and more preferably 0.2 or less. An intensity ratio (B / A) of 0.3 or less means that the orientation of the (111) plane is significantly more prevalent than that of the (200) plane. Use of a negative electrode current collector including the copper layer 201 exhibiting such an orientation improves the cycle characteristics of the battery and the temperature stability of the tab. The position of Peak B may be 50.1° to 50.9° or 50.2° to 50.8°.

[0029] In the copper layer 201, the half-width of Peak B is preferably 0.5° or less, 0.3° or less, 0.2° or less, or 0.15° or less. When the half-width of Peak B is within the above range, the cycle characteristics of the battery and the temperature stability of the tab tend to be further improved. In addition, the half-width of Peak B may be 0.05° or more, or 0.1° or more.

[0030] In the copper layer 201, the ratio (C / A) of the intensity of Peak C at an angle of 73.7° to 74.7° to the intensity of Peak A is preferably 0.3 or less, more preferably 0.25 or less, even more preferably 0.15 or less, even more preferably 0.12 or less, and particularly preferably 0.1 or less. An intensity ratio (C / A) of 0.3 or less means that the orientation of the (111) plane is significantly more prevalent than the (220) plane. Use of a negative electrode current collector including a copper layer 201 exhibiting such an orientation tends to further improve the cycle characteristics of the battery and the temperature stability of the tab. The position of Peak C may be 73.8° to 74.6° or 73.9° to 74.5°.

[0031] The X-ray diffraction measurement may be performed by a conventionally known method using a commercially available X-ray diffraction measurement device. For example, measurement may be performed using a "RINT-Ultima" (X-ray diffraction device) manufactured by Rigaku Corporation, using CuKα rays as an X-ray source.

[0032] The thickness of each copper layer 201 is preferably 0.2 μm to 10 μm, 0.3 μm to 5.0 μm, 0.5 μm to 3.0 μm, or 0.8 μm to 2.0 μm. By keeping the thickness of each copper layer 201 within the above range, the cycle characteristics of the battery and / or the temperature stability of the tab tend to be improved.

[0033] In the negative electrode current collector film of this embodiment, the total thickness of the copper layer 201 relative to the thickness of the resin layer 202 is preferably 0.1 to 1.0, 0.2 to 0.6, or 0.35 to 0.5. By setting the thickness ratio of the copper layer 201 to the resin layer 202 within the above range, the cycle characteristics of the battery and / or the temperature stability of the tab tend to be improved.

[0034] The method for producing the negative electrode current collector film of this embodiment is not particularly limited as long as it can produce a current collector film having the above-described characteristics. A manufactured product may be used, or the current collector film may be produced by a conventionally known method. Examples of known methods include a method in which a base film (resin sheet) that will become the resin layer 202 is used, and the copper layer 201 is formed by sputtering or vapor deposition on both sides of the base film. Another possible method is to perform sputtering or vapor deposition on both sides of the base film, and then further grow the copper layer 201 by electroplating. When using this method, for example, in sputtering, increasing the target output tends to increase the orientation of the (111) plane, which in turn increases the crystallinity of the (111) plane. Therefore, in this embodiment, it is considered necessary to ensure that the target output is neither too high nor too low. Furthermore, in vapor deposition, increasing the purity of the copper used in the raw material tends to decrease the orientation. Therefore, in this embodiment, it is considered necessary to use copper with a purity that is not too high. Furthermore, increasing the vapor deposition rate and decreasing the cooling temperature tends to decrease the orientation. Therefore, in this embodiment, it is considered necessary to adjust the deposition rate so that it is not too high and the cooling temperature so that it is not too low. Note that the current collector film may also be prepared using the method described in the examples below.

[0035] The negative electrode active material is a material that causes an electrode reaction, i.e., an oxidation reaction and a reduction reaction, in the negative electrode 10. Specifically, the negative electrode active material of this embodiment includes lithium metal and a host material of lithium element (lithium ion or lithium metal). The host material of lithium element means a material provided to hold lithium ion or lithium metal in the negative electrode 10. Examples of such a holding mechanism include intercalation, alloying, and occlusion of metal clusters, and intercalation is a typical example.

[0036] The negative electrode active material is not particularly limited, but examples thereof include lithium metal and alloys containing lithium metal, carbon-based materials, metal oxides, and metals that can be alloyed with lithium and alloys containing such metals. The carbon-based materials are not particularly limited, but examples thereof include graphene, graphite, hard carbon, and carbon nanotubes. The metal oxides are not particularly limited, but examples thereof include titanium oxide-based compounds and cobalt oxide-based compounds. The metals that can be alloyed with lithium are not particularly limited, but examples thereof include silicon, germanium, tin, lead, aluminum, and gallium.

[0037] The lithium secondary battery of this embodiment may be an anode-free battery that does not substantially contain a negative electrode active material, or may contain a negative electrode active material. In an anode-free lithium secondary battery, the negative electrode 10 does not contain a negative electrode active material and is therefore composed of a negative electrode current collector. After initial charging, lithium metal is deposited on the negative electrode 10, and the deposited lithium metal is further electrolytically eluted to perform charging and discharging. Therefore, an anode-free battery has the advantage of, in principle, having a high energy density because the volume and mass of the negative electrode active material are reduced, thereby reducing the overall volume and mass of the battery.

[0038] 1.2 Negative Electrode Tab When the negative electrode tab 11 and the laminate 12 of the negative electrode tab lead portion are joined by ultrasonic welding, the ultrasonic welding may be performed while applying pressure. When ultrasonic welding is performed while applying pressure, heat is generated at the negative electrode tab joint 13, as shown in FIG. 5, for example, and the negative electrode tab joint 13 tends to become thinner.

[0039] As shown in Fig. 6, the negative electrode tab 11 is preferably joined by welding to a negative electrode tab lead portion laminate 12 obtained by assembling negative electrode tab lead portions 102, which are the negative electrode side ends of the battery laminate B, with auxiliary metal foil 14 sandwiched between them. By sandwiching the auxiliary metal foil 14, the thickness of the copper layer 201, which is thinned by ultrasonic welding, can be compensated for, and conductivity tends to be easily maintained. The auxiliary metal foil 14 is not particularly limited, but an example is electrolytic copper foil.

[0040] The negative electrode tab 11 may be made of, for example, at least one material selected from the group consisting of copper, titanium, stainless steel, nickel, and alloys thereof. The negative electrode tab 11 is preferably made of at least one material selected from the group consisting of copper, nickel, and alloys thereof, and more preferably made of copper plated with nickel.

[0041] The thickness of the negative electrode tab 11 is preferably 0.1 mm or more and 0.5 mm or less, and 0.2 mm or more and 0.4 mm or less. By setting the thickness of the negative electrode tab 11 within the above range, the cycle characteristics of the lithium secondary battery and the temperature stability of the tab tend to be further improved.

[0042] 1.3. Separator The separator 20 of this embodiment is not particularly limited as long as it has the function of physically and / or electrically isolating the positive electrode 30 and the negative electrode 10 and the function of ensuring ionic conductivity of lithium ions. Examples of such a separator include an insulating porous material, a polymer electrolyte, a gel electrolyte, and an inorganic solid electrolyte. Typically, the separator 20 includes at least one material selected from the group consisting of an insulating porous material, a polymer electrolyte, and a gel electrolyte. Furthermore, as the separator 20, one type of material may be used alone, or two or more types of materials may be used in combination.

[0043] The separator 20 is preferably made of an insulating porous material, a polymer electrolyte, or a gel electrolyte, either singly or in combination. When an insulating porous material is used alone as the separator 20, the lithium secondary battery must further include an electrolytic solution. Examples of the polymer electrolyte include, but are not limited to, solid polymer electrolytes primarily containing a polymer and an electrolyte, and semi-solid polymer electrolytes primarily containing a polymer, an electrolyte, and a plasticizer. Examples of the gel electrolyte include, but are not limited to, those primarily containing a polymer and a liquid electrolyte (i.e., a solvent and an electrolyte).

[0044] Polymers that may be contained in polymer electrolytes and gel electrolytes include, but are not limited to, polymers containing functional groups containing oxygen atoms such as ethers and esters, halogen groups, and polar groups such as cyano groups. Specific examples include resins having ethylene oxide units in the main chain and / or side chains such as polyethylene oxide (PEO), resins having propylene oxide units in the main chain and / or side chains such as polypropylene oxide (PPO), acrylic resins, vinyl resins, ester resins, nylon resins, polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), polysiloxane, polyphosphazene, polymethyl methacrylate, polyamide, polyimide, aramid, and polytetrafluoroethylene. The above-mentioned resins may be used alone or in combination of two or more.

[0045] Examples of electrolytes contained in the polymer electrolyte and gel electrolyte include salts of Li, Na, K, Ca, and Mg. Typically, in this embodiment, the polymer electrolyte and gel electrolyte contain a lithium salt. The lithium salt is not particularly limited, but may be, for example, any salt that can be contained in the electrolyte solution described below. Such salts or lithium salts may be used alone or in combination of two or more.

[0046] The compounding ratio of the polymer to the lithium salt in the polymer electrolyte and the gel electrolyte may be determined by the ratio of the polar group of the polymer to the lithium atom of the lithium salt. For example, when the polymer contains oxygen atoms, the compounding ratio may be determined by the ratio ([Li] / [O]) of the number of oxygen atoms of the polymer to the number of lithium atoms of the lithium salt. In the polymer electrolyte and the gel electrolyte, the compounding ratio of the polymer to the lithium salt can be adjusted so that the ratio ([Li] / [O]) is, for example, 0.02 to 0.20, 0.03 to 0.15, or 0.04 to 0.12.

[0047] The solvent contained in the gel electrolyte is not particularly limited, and for example, the solvents that can be contained in the electrolyte solution described below can be used alone or in combination of two or more. Examples of preferred solvents are the same as those in the electrolyte solution described below. The plasticizer contained in the semi-solid polymer electrolyte is not particularly limited, and examples include the same components as the solvents that can be contained in the gel electrolyte and various oligomers.

[0048] When the separator 20 includes an insulating porous member, the pores of the member are filled with an ion-conductive substance, thereby causing the member to exhibit ion conductivity. Thus, in this embodiment, the pores are filled with, for example, the electrolytic solution of this embodiment or a gel electrolyte containing the electrolytic solution of this embodiment.

[0049] The material constituting the insulating porous member is not particularly limited, and examples thereof include insulating polymer materials, specifically polyethylene (PE) and polypropylene (PP). That is, the separator 20 may be a porous polyethylene (PE) film, a porous polypropylene (PP) film, or a laminated structure thereof.

[0050] 1.4. Positive Electrode The positive electrode 30 of this embodiment includes a positive electrode current collector and a positive electrode active material layer. The average thickness of the positive electrode 30 is not particularly limited, but is, for example, 20 μm to 100 μm, 30 μm to 80 μm, or 40 μm to 70 μm. However, the average thickness of the positive electrode 30 can be adjusted appropriately depending on the desired battery capacity.

[0051] The positive electrode current collector of this embodiment may have a positive electrode current collector film including a resin layer containing polyethylene terephthalate and metal layers provided on both sides of the resin layer, or may have a metal layer without a resin layer. When a positive electrode current collector film is provided, the metal layers are formed by attaching the metal layers to both surfaces of the resin layer by vapor deposition, sputtering, electrolytic plating, or with an adhesive.

[0052] The resin layer of the positive electrode current collector is an insulator and prevents electrical conduction between the metal layers provided on both sides of the resin layer. The resin constituting the resin layer is not particularly limited, but may be, for example, a sheet-like (film-like) or fibrous resin. The resin may include at least one selected from the group consisting of polyethylene terephthalate (PET), polypropylene, polyamide, acrylic resin, polycarbonate, polyethylene, polyvinyl chloride, and polystyrene. The above resins may be used alone or in combination of two or more.

[0053] In addition to the resins described above, the resin layer of the positive electrode current collector may contain other additives as appropriate depending on the desired physical properties. The additives are not particularly limited, but examples thereof include colorants, flame retardants, surfactants, etc.

[0054] The thickness of the resin layer of the positive electrode current collector is, for example, 2 μm or more and 15 μm or less, 3 μm or more and 12 μm or less, or 4 μm or more and 10 μm or less.

[0055] The metal layer of the positive electrode current collector is in physical and / or electrical contact with the positive electrode active material layer and functions to donate and receive electrons to and from the positive electrode active material layer. The metal layer of the positive electrode current collector is composed of a conductor such as a metal that does not react with lithium in a battery. The metal constituting the metal layer of the positive electrode current collector is not particularly limited, but is at least one selected from the group consisting of aluminum, titanium, stainless steel, nickel, and alloys thereof. Among these, aluminum or an aluminum alloy is preferred, and aluminum is particularly preferred. The metal may be used alone or in combination of two or more. In this specification, the term "metal that does not react with lithium" refers to a metal that does not react with lithium ions or lithium metal to form an alloy under the operating conditions of a lithium secondary battery.

[0056] When the positive electrode current collector has a positive electrode current collector film, the thickness of the metal layer is not particularly limited, but is, for example, 0.1 μm to 4.0 μm, 0.2 μm to 3.0 μm, 0.3 μm to 2.5 μm, or 0.4 μm to 2.0 μm. When the positive electrode current collector has a metal layer without a resin layer, the thickness of the metal layer is not particularly limited, but is, for example, 4.0 μm to 20.0 μm, 6.0 μm to 17.5 μm, or 8.0 μm to 15.0 μm.

[0057] 1.4.2 Positive Electrode Active Material The positive electrode active material is a material that causes an electrode reaction, i.e., an oxidation reaction and a reduction reaction, in the positive electrode 30. The positive electrode active material of this embodiment is not particularly limited, but may be contained in a positive electrode active material composition that includes, for example, a binder, a conductive additive, a sacrificial positive electrode agent, and other additives. The positive electrode active material composition is applied to at least one or both surfaces of a positive electrode current collector and press-molded to form a positive electrode active material layer on at least one or both surfaces of the positive electrode current collector.

[0058] The method for disposing the positive electrode active material layer on the positive electrode current collector is not limited to press molding, and examples thereof include a method in which a thermosetting compound is added to a positive electrode active material composition and the composition is heated to harden it, a method in which a photocurable compound is added to a positive electrode active material composition and the composition is hardened by irradiating it with light, and a method in which the positive electrode active material composition is a two-component hardening composition and the two components are mixed to harden it.

[0059] The positive electrode active material layer of this embodiment is a compound represented by the general formula: Li ｚ Ni ｘ Co ｙ M １－ｘ－ｙ O ２＋α (wherein 0.5≦x≦1.0, 0≦y≦0.35, 0.9≦z≦1.3, −0.2≦α≦0.15, and M is one or more elements selected from the group consisting of Mn, Al, V, Mg, Mo, Nb, Ti, Zr, Fe, Cu, Cr, Zn, F, and B).

[0060] Preferably, the positive electrode active material layer is a compound represented by the general formula: Li ｚ Ni ｘ Co ｙ M １－ｘ－ｙ O ２＋α (wherein 0.7≦x≦1.0, 0≦y≦0.35, 0.9≦z≦1.3, −0.2≦α≦0.15, and M is one or more elements selected from the group consisting of Mn, Al, V, Mg, Mo, Nb, Ti, Zr, Fe, Cu, Cr, Zn, F, and B). By including the above-mentioned compound with a high nickel ratio as the positive electrode active material, the energy density of the lithium secondary battery tends to be further improved. Furthermore, as the nickel ratio increases, a redox shuttle reaction is more likely to occur, but by including an additive, which will be described in detail below, in the electrolyte, the reaction is suppressed, and the electrolyte tends to have excellent performance stability at high temperatures.

[0061] The positive electrode active material may include other positive electrode active materials in addition to the above-mentioned compounds. Specifically, the other positive electrode active material in this embodiment may be a host material of lithium element (typically, lithium ion). Such other positive electrode active materials are not particularly limited, but include, for example, metal oxides and metal phosphates. The metal oxides are not particularly limited, but include, for example, cobalt oxide-based compounds, manganese oxide-based compounds, and nickel oxide-based compounds. The metal phosphates are not particularly limited, but include, for example, iron phosphate-based compounds and cobalt phosphate-based compounds. Typical other positive electrode active materials include LiCoO ２ , LiNi ｘ Mn ｙ O(x+y=1), LiNiO ２ , LiMn ２ O ４ , LiFePO , LiCoPO , LiFeOF , LiNiOF , and TiS ２ The other positive electrode active materials may be used alone or in combination of two or more.

[0062] The positive electrode active material composition may contain a binder. By including a binder, the positive electrode active material layer is more easily bound to the positive electrode current collector, and flexibility is improved after the positive electrode active material layer is disposed on the positive electrode current collector. The binder of this embodiment is not particularly limited, but examples thereof include polyvinylidene fluoride; modified polyvinylidene fluoride obtained by introducing functional groups such as hydroxyl groups, amino groups, carbonyl groups, carboxyl groups, phenyl groups, and methyl groups into polyvinylidene fluoride; polytetrafluoroethylene; modified polytetrafluoroethylene obtained by introducing functional groups such as hydroxyl groups, amino groups, carbonyl groups, carboxyl groups, phenyl groups, and methyl groups into polytetrafluoroethylene; block copolymers, random copolymers, or graft copolymers having tetrafluoroethylene as a structural unit; styrene butadiene rubber; carboxymethyl cellulose; acrylic resins; polyimide resins, and the like. The binder may be used alone or in combination of two or more.

[0063] The positive electrode active material composition of this embodiment may contain a sacrificial positive electrode agent. The sacrificial positive electrode agent of this embodiment is a lithium-containing compound that undergoes an oxidation reaction and does not substantially undergo a reduction reaction in the charge / discharge potential range of the positive electrode active material. The sacrificial positive electrode agent is not particularly limited, but examples thereof include Li ２ O ２ Lithium oxides such as Li ３ Lithium nitrides such as N; Li ２ S-P ２ S ５ , Li ２ S-LiCl, Li ２ S-LiBr and Li ２ Lithium sulfide-based solid solutions such as S-LiI; Li １＋ｘ (Ti １－ｙ Fe ｙ ) １－ｘ O ２ (0<x≦0.25, 0.4<y≦0.9), Li ２－ｘ Ti １－ｚ Fe ｚ O ３－ｙ (0≦x<2, 0≦y≦1, 0.05≦z≦0.95), Li ５ FeO ４ The sacrificial positive electrode agent may be used alone or in combination of two or more.

[0064] 1.5. Positive Electrode Tab The positive electrode tab is placed on a stack of positive electrode tab lead portions, which are positive electrode end portions, and joined by welding. Examples of welding methods include ultrasonic welding, laser welding, resistance welding, and spot welding. When the positive electrode tab lead portion includes a resin layer, ultrasonic welding is suitable.

[0065] The positive electrode tab may be made of, for example, aluminum or an aluminum alloy. In one example, the positive electrode tab may be made of hard aluminum. The thickness of the positive electrode tab may be, for example, 0.05 mm to 1 mm, or 0.1 mm to 0.5 mm.

[0066] 1.6. Electrolyte A lithium secondary battery may contain an electrolyte. An electrolyte is a liquid containing a solvent and an electrolyte and has ion conductivity. The electrolyte may also be referred to as a liquid electrolyte and acts as a conductive path for lithium ions. Therefore, when a lithium secondary battery contains an electrolyte, the internal resistance can be reduced, and the energy density, capacity, and cycle characteristics can be improved.

[0067] The electrolytic solution is, for example, a solution that fills the housing (pouch) of the lithium secondary battery. The electrolytic solution may be impregnated into the separator 20, or may be held in a polymer to form a polymer electrolyte or a gel electrolyte.

[0068] The electrolyte contained in the electrolytic solution may be a lithium salt, such as LiI, LiCl, LiBr, LiF, or LiBF. ４ , LiPF ６ , LiAsF ６ , LiSO ３ CF ３ , LiN(SO ２ F) ２ , LiN(SO ２ CF ３ ) ２ , LiN(SO ２ CF ３ CF ３ ) ２ , LiB(O ２ C ２ H ４ ) ２ , LiB(C ２ O ４ ) ２ , LiB(O ２ C ２ H ４ ) F ２ , LiB(OCOCF ３ ) ４ , LiNO ３ , and Li ２ SO ４ It may be one or a combination of two or more selected from the group consisting of:

[0069] As the solvent contained in the electrolytic solution, for example, a non-aqueous solvent containing fluorine atoms (hereinafter referred to as a "fluorinated solvent") and a non-aqueous solvent containing no fluorine atoms (hereinafter referred to as a "non-fluorinated solvent") may be added.

[0070] Examples of fluorinated solvents include 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, and 1H,1H,5H-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether.

[0071] Examples of non-fluorine-containing solvents include triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 1,2-dimethoxyethane, dimethoxyethane, dimethoxypropane, dimethoxybutane, diethylene glycol dimethyl ether, acetonitrile, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, ethylene carbonate, propylene carbonate, chloroethylene carbonate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, trimethyl phosphate, triethyl phosphate, and 12-crown-4.

[0072] The above fluorinated solvents and / or non-fluorinated solvents may be used alone or in any combination of two or more in any ratio. The contents of the fluorinated solvent and non-fluorinated solvent are not particularly limited, and the ratio of the fluorinated solvent to the total solvent may be 0 to 100% by volume, or the ratio of the non-fluorinated solvent to the total solvent may be 0 to 100% by volume.

[0073] 2. Manufacturing Method of Lithium Secondary Battery There are no particular limitations on the manufacturing method of a lithium secondary battery, as long as it is a method that can manufacture a lithium secondary battery having the above-mentioned battery configuration. For example, the following method can be mentioned.

[0074] The negative electrode 10, separator 20, and positive electrode 30 described above are prepared. The components and reagents used for the components may be produced by conventionally known methods, or commercially available products may be used. The positive electrode 30, separator 20, and negative electrode 10 prepared in this manner are stacked in this order, with the positive electrode 30 and the separator 20 facing each other, to obtain a laminate. The resulting laminate is sealed in a sealed container together with an electrolyte solution to obtain a lithium secondary battery. The sealed container is not particularly limited, but examples thereof include laminate films.

[0075] 1, a plurality of positive electrodes 30 and negative electrodes 10 may be stacked alternately with a separator 20 sandwiched between the positive electrode 30 and the negative electrode 10, which tends to further improve battery performance such as energy density. As a stacking method, for example, as shown in FIG. 7, the negative electrode 10 and the positive electrode 30 may be wrapped so as to face opposite sides of the separator 20 without contacting each other, and the separator 20 may be stacked without cutting. Such stacking is preferable from the viewpoints of preventing short circuits and improving productivity.

[0076] When producing a lithium ion battery, the battery may be produced in the same manner as the above-described battery production method, except that a lithium host material is used for the negative electrode 10. The method for producing the negative electrode 10 having such a host material (negative electrode active material) is not particularly limited, but is, for example, as follows. If necessary, the above-described negative electrode active material is mixed with a binder, a conductive additive, and other additives, which will be described in detail below, to obtain a negative electrode active material composition. The negative electrode active material or the obtained negative electrode active material composition is applied to both sides or one side of the negative electrode current collector, and press-molded to form a negative electrode active material layer on both sides or one side of the negative electrode current collector, thereby obtaining a molded body. The obtained molded body is punched to a predetermined size by a punching process, to obtain the negative electrode 10 of this embodiment.

[0077] The lithium secondary battery of this embodiment can be made into an anode-free lithium battery, a lithium ion battery, a lithium metal battery, a lithium sulfur battery, a lithium oxygen battery, or a lithium air battery by adding additional components or changing the materials used in each component, and among these, the anode-free lithium battery, lithium ion battery, and lithium metal battery configurations are particularly suitable.

[0078] The shape of the battery of the lithium secondary battery of this embodiment is not particularly limited, and may be, for example, a sheet type, a laminated sheet type, a thin shape, a cylindrical shape with a bottom, a prismatic shape with a bottom, etc. From the viewpoint of more effectively and reliably achieving the effects of this embodiment, the sheet type, laminated sheet type, or thin shape is preferred.

[0079] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. ５ Pa).

[0080] 1. Fabrication of Lithium Secondary Batteries Lithium ion secondary batteries of Examples and Comparative Examples were fabricated as follows.

[0081] 1.1. Preparation of Negative Electrode 1.1.1. Preparation of Negative Electrode Current Collector (Example 1) A 4.5 μm polypropylene film obtained by injection molding was used as a negative electrode current collector, and vapor deposition and electrolytic plating were performed according to the following procedure. First, the polypropylene film was placed in a vapor deposition apparatus, and a 50 nm copper thin film was formed on both sides of the polypropylene film. Subsequently, electrolytic plating using copper sulfate was performed until the copper layer on each surface of the film reached a thickness of 1.0 μm, thereby obtaining a current collector film. A negative electrode active material layer was formed using the method described below, and cut out into a negative electrode main body portion measuring 4 cm × 4 cm with a 0.5 cm × 3 cm negative electrode tab lead, obtaining a negative electrode with a thickness of 100 μm.

[0082] Example 2 A 4.5 μm thick polypropylene film similar to that used in Example 1 was prepared. This polypropylene film was subjected to sputtering and electrolytic plating treatments according to the following procedure. First, the polypropylene film was placed in a vacuum chamber for sputtering, and copper ions were generated in the evacuated chamber to form 50 nm copper thin films on both sides of the film. Subsequently, electrolytic plating treatment using copper sulfate was performed until the copper layer on each surface of the film reached a thickness of 1.0 μm, thereby obtaining a current collector film of Example 2. A negative electrode active material layer was formed by the method described below, and the film was cut out to obtain a negative electrode of the same size and shape as that of Example 1, thereby obtaining a negative electrode.

[0083] Example 3 A 4.5 μm thick PET film was used as a negative electrode current collector, with a 1.0 μm thick copper thin film formed on both sides of the film. A negative electrode active material layer was then formed by the method described below, and a negative electrode of the same size and shape as in Example 1 was obtained by cutting out the negative electrode. The 2θ pattern of the X-ray diffraction measurement performed on this current collector film is shown in FIG. 8.

[0084] Example 4 A 6.0 μm thick PET film was used as a negative electrode current collector, with a 1.0 μm thick copper thin film formed on both sides of the film. A negative electrode active material layer was then formed by the method described below, and a negative electrode of the same size and shape as in Example 1 was obtained by cutting out the negative electrode. The 2θ pattern of the X-ray diffraction measurement performed on this current collector film is shown in FIG. 9 .

[0085] Example 5 A 4.5 μm polypropylene film was used as a negative electrode current collector, with a 1.0 μm copper thin film formed on both sides of the film. A negative electrode active material layer was then formed by the method described below, and a negative electrode of the same size and shape as in Example 1 was obtained by cutting out the film. The 2θ pattern of the X-ray diffraction measurement performed on this current collector film is shown in FIG.

[0086] (Comparative Example 1) A 6.0 μm PET film obtained by injection molding was used as a negative electrode current collector, and vapor deposition and electrolytic plating were performed according to the following procedure. First, the PET film was placed in a vapor deposition apparatus, and a 50 nm copper thin film was formed on both sides of the PET film. Subsequently, electrolytic plating using copper sulfate was performed until the copper layer on each surface of the film reached a thickness of 1.0 μm, thereby obtaining a current collector film of Comparative Example 1. Then, a negative electrode active material layer was formed by the method described below, and the negative electrode was cut out to have the same size and shape as in Example 1, thereby obtaining a negative electrode.

[0087] (Comparative Example 2) A 4.5 μm polypropylene film obtained by injection molding was used as a negative electrode current collector, and vapor deposition and electrolytic plating were performed according to the following procedure. First, the polypropylene film was placed in a vapor deposition apparatus, and a 50 nm copper thin film was formed on both sides of the polypropylene film. Subsequently, electrolytic plating using copper sulfate was performed until the copper layer on each surface of the film reached a thickness of 1.0 μm, thereby obtaining a current collector film of Comparative Example 2. Then, a negative electrode active material layer was formed by the method described below, and the resultant was cut out to obtain a negative electrode of the same size and shape as in Example 1, thereby obtaining a negative electrode.

[0088] (Comparative Example 3) A 4.5 μm polypropylene film obtained by injection molding was used as a negative electrode current collector, and vapor deposition and electrolytic plating were performed according to the following procedure. First, the polypropylene film was placed in a vapor deposition apparatus, and a 50 nm copper thin film was formed on both sides of the polypropylene film. Subsequently, electrolytic plating using copper sulfate was performed until the copper layer on each surface of the film reached a thickness of 1.0 μm, thereby obtaining a current collector film of Comparative Example 3. Then, a negative electrode active material layer was formed by the method described below, and the resultant was cut out to obtain a negative electrode of the same size and shape as in Example 1, thereby obtaining a negative electrode.

[0089] Comparative Example 4: A 6.0 μm thick PET film was used as a negative electrode current collector, with a 1.0 μm thick copper thin film formed on both sides of the film. A negative electrode active material layer was then formed by the method described below, and a negative electrode of the same size and shape as in Example 1 was obtained by cutting out the negative electrode. The 2θ pattern of the X-ray diffraction measurement performed on this current collector film is shown in FIG.

[0090] The negative electrode current collector film obtained above was subjected to X-ray diffraction measurement using "RINT-Ultima" manufactured by Rigaku Corporation, and the associated software was used to detect each peak and calculate the full width at half maximum (FWHM).

[0091] 1.1.2. Formation of Negative Electrode Active Material Layer A negative electrode active material composition was prepared by mixing 97.0 parts by mass of graphite as the negative electrode active material, 0.5 parts by mass of carbon black as a conductive additive, and 1.5 parts by mass of carboxymethyl cellulose (CMC) and 1.0 part by mass of styrene-butadiene rubber (SBR) as binders with water as a solvent. This negative electrode active material composition was applied to a portion of one side of each of the negative electrode current collector films obtained above so as to have a basis weight of 15 mg / cm. ２ The negative electrode active material layer was formed on one side of the negative electrode current collector by applying the coating and pressing the coating so that the negative electrode active material layer was formed on one side of the negative electrode current collector. The negative electrode of each example was obtained by cutting out the negative electrode current collector from this molded body, with the negative electrode active material layer being the negative electrode current collector portion and the negative electrode lead portion being the non-formed portion.

[0092] 1.2 Preparation of Positive Electrode A current collector film was used as the positive electrode current collector. The current collector film was a 6.0 μm thick PET film resin layer with a 1.0 μm thick aluminum metal layer deposited on both sides. LiNi was used as the positive electrode active material in N-methyl-pyrrolidone (NMP) as the solvent. ０．８ Co ０．１５ Al ０．０５ O ２ A positive electrode active material composition was prepared by mixing 96 parts by mass of the above-mentioned cellulose acetate copolymer, 2 parts by mass of carbon black as a conductive additive, and 2 parts by mass of polyvinylidene fluoride (PVDF) as a binder. This positive electrode active material composition was applied to one side of a positive electrode current collector in a basis weight of 15 mg / cm. ２ The positive electrode active material layer was formed on one side of the positive electrode current collector by coating with the paste and pressing it against the cathode current collector, thereby obtaining a molded body. This molded body was cut out to a predetermined size (4 cm x 4 cm). In this way, a positive electrode 30 was obtained.

[0093] 1.3. Preparation of separator Polyvinylidene fluoride (PVDF) and Al ２ O ３A polyethylene microporous film sheet (thickness: 15 μm, 4 cm×4 cm) whose surface was coated with the mixture was prepared as separator 20 .

[0094] 1.4. Preparation of Electrolyte Solution Lithium hexafluorophosphate (LiPF) was dissolved in a solvent containing ethylene carbonate (EC) and dimethyl carbonate (DMC) in a volume ratio of 3:7. ６ ) was dissolved at a concentration of 1 M. In addition, the total amount of the above solvent (LiPF ６ The content ratios of lithium difluorophosphate (LiPO) to the total mass of EC and DMC (excluding ２ F ２ ) and vinylene carbonate (VC) were added to the solvent. Thus, an electrolyte solution was prepared.

[0095] 1.5. Battery Assembly The positive electrode 30, separator 20, and negative electrode 10 obtained as described above were stacked multiple times in this order, with the positive electrode 30 facing the separator 20, as shown in FIG. 1 , to obtain a laminate. The lead portions of the stacked positive and negative electrodes were then ultrasonically welded to a 100 μm Al terminal for the positive electrode and a 100 μm Ni terminal for the negative electrode, and inserted into a laminate exterior. The resulting electrolyte was then injected into the exterior and sealed, yielding lithium-ion secondary batteries for each of the Examples and Comparative Examples.

[0096] 2. Evaluation of Lithium Secondary Battery 2.1. Rate Retention Rate The lithium secondary battery obtained above was initially CC charged to 4.2 V at a charge rate of 0.1 C in an environment of 25°C, and then initially CC discharged to 3.0 V at a discharge rate of 0.1 C. The battery was then CC charged again to 4.2 V at 0.1 C, and after charging was completed, CC discharge was performed at 3 C. The ratio of the discharge capacity at a discharge rate of 3.0 C to the initial discharge capacity (discharge rate at 0.1 C) obtained in this manner was calculated as the rate retention rate (%).

[0097] 2.2 Tab Temperature During Current Flow Each lithium secondary battery for which the rate retention rate had been measured was again CC charged to 4.2 V at a charge rate of 0.1 C, and then CC discharged to 2.5 V at a rate of 10 C. Two minutes after discharge was completed, the temperature (°C) at the center of the negative electrode tab was measured. A lower tab temperature means less heat generation, and therefore better tab temperature stability.

[0098]

[0099] As shown in Table 1, Examples 1 to 5, which included a laminate including a plurality of negative electrodes, a plurality of separators, and a plurality of positive electrodes, and a negative electrode tab joined to a plurality of negative electrode tab lead portions extending from the laminate, wherein the negative electrode tab lead portion was a negative electrode current collector constituting a negative electrode extending from the laminate, and the negative electrode tab lead portion and the negative electrode current collector included a resin layer and copper layers formed on both sides of the resin layer, and in a 2θ pattern obtained by X-ray diffraction measurement of the copper layer, the copper layer had at least Peak A at an angle of 42.9° or more and 43.9° or less, and the ratio (B / A) of the intensity of Peak B at an angle of 50.0° or more and 51.0° or less to the intensity of Peak A was 0.3 or less, and further the half width of Peak A was 0.2° or less, were confirmed to be superior in rate characteristics and temperature stability of the tab during current application compared to Comparative Examples 1 to 4, which did not include such examples.

[0100] Supplementary Notes Embodiments of the present disclosure include the following aspects: [1] A lithium secondary battery comprising: a laminate including a plurality of negative electrodes, a plurality of separators, and a plurality of positive electrodes; a plurality of negative electrode tab lead portions extending from the laminate; and a plurality of negative electrode tabs joined to the negative electrode tab lead portions, wherein the negative electrode tab lead portion is a negative electrode current collector constituting the negative electrode extending from the laminate, the negative electrode tab lead portion and the negative electrode current collector include a resin layer and copper layers formed on both sides of the resin layer, wherein a 2θ pattern obtained by X-ray diffraction measurement of the copper layer has at least a peak A in an angle of 42.9° or more and 43.9° or less, a ratio (B / A) of the intensity of a peak B in an angle of 50.0° or more and 51.0° or less to the intensity of the peak A is 0.3 or less, and the half width of the peak A is less than 0.2°. [2] The lithium secondary battery according to [1], wherein the ratio (C / A) of the intensity of Peak C at an angle of 73.7° or more and 74.7° or less to the intensity of Peak A is 0.3 or less. [3] The lithium secondary battery according to [1] or [2], wherein the half-width of Peak B is 0.1° or more. [4] The lithium secondary battery according to any one of [1] to [3], wherein the average thickness of the resin layer is 3.0 μm or more and 10.0 μm or less, and the average thickness of the copper layer is 0.5 μm or more and 3.0 μm or less. [5] The lithium secondary battery according to any one of [1] to [4], wherein the resin layer contains at least one selected from the group consisting of polyethylene terephthalate, polypropylene, polyamide, acrylic resin, polycarbonate, polyethylene, polyvinyl chloride, and polystyrene. [6] The lithium secondary battery according to any one of [1] to [5], wherein the resin layer is made of polyethylene terephthalate or polypropylene. [7] The lithium secondary battery according to any one of [1] to [6], which is used to join the tab lead portion to the tab by ultrasonic welding.

[0101] The lithium secondary battery according to the present invention has excellent cycle characteristics and temperature stability of the tab, and therefore has industrial applicability as an electricity storage device for a variety of uses.

[0102] A, B... battery stack, 10... negative electrode, 11... negative electrode tab, 12... stack of negative electrode tab lead portion, 13... negative electrode tab joint portion, 14... auxiliary metal foil, 20... separator, 30... positive electrode, 101... negative electrode main body portion, 102... negative electrode tab lead portion, 201... copper layer, 202... resin layer.

Claims

1. A lithium secondary battery comprising: a laminate including a plurality of negative electrodes, a plurality of separators, and a plurality of positive electrodes; a plurality of negative electrode tab leads extending from the laminate; and negative electrode tabs joined to the plurality of negative electrode tab leads, wherein the negative electrode tab leads are formed by extending a negative electrode current collector constituting the negative electrode from the laminate, the negative electrode tab leads and the negative electrode current collector include a resin layer and copper layers formed on both surfaces of the resin layer, in the 2θ pattern of X-ray diffraction measurement of the copper layer, it has a peak A at least at 42.9° or more and 43.9° or less, the ratio (B / A) of the intensity of peak B at 50.0° or more and 51.0° or less to the intensity of peak A is 0.3 or less, and the half-value width of peak A is 0.2° or less.

2. The lithium secondary battery according to claim 1, wherein the ratio (C / A) of the intensity of peak C at 73.7° or more and 74.7° or less to the intensity of peak A is 0.3 or less.

3. The lithium secondary battery according to claim 1, wherein the half-value width of peak B is 0.5° or less.

4. The lithium secondary battery according to claim 1, wherein the average thickness of the resin layer is 3.0 μm or more and 10.0 μm or less, and the average thickness of the copper layer is 0.5 μm or more and 3.0 μm or less.

5. The lithium secondary battery according to claim 1, wherein the resin layer contains at least one selected from the group consisting of polyethylene terephthalate, polypropylene, polyamide, acrylic resin, polycarbonate, polyethylene, polyvinyl chloride, and polystyrene.

6. The lithium secondary battery according to claim 1, wherein the resin layer is made of polyethylene terephthalate or polypropylene.

7. The lithium secondary battery according to claim 1, wherein the negative electrode tab leads are joined to the negative electrode tabs by ultrasonic welding.

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