Lithium secondary battery

Abstract

This invention provides a lithium secondary battery with excellent cycle characteristics and temperature stability of the tabs. The invention relates to a lithium secondary battery comprising: a laminate including multiple negative electrodes, multiple separators, and multiple positive electrodes; multiple negative electrode tab leads extending from the laminate; and negative electrode tabs joined to the multiple negative electrode tab leads, wherein each negative electrode tab lead is formed by a negative electrode current collector constituting the negative electrode extending from the laminate, the negative electrode tab leads and the negative electrode current collector comprising a resin layer and copper layers formed on both sides of the resin layer, wherein in the 2θ pattern determined by X-ray diffraction of the copper layer, there is at least a peak A located at 42.9° or higher and 43.9° or lower, and the intensity ratio (B / A) of peak B located at 50.0° or higher and 51.0° or lower to peak A is 0.3 or lower, and the half-width at half-maximum (FWHM) of peak A is 0.2° or lower.

Description

Technical Field

[0001] This invention relates to lithium secondary batteries. Background Technology

[0002] In recent years, technologies that convert natural energy sources such as solar or wind power into electrical energy have attracted attention. Consequently, various secondary batteries have been developed as energy storage devices that are highly safe and capable of storing large amounts of electrical energy.

[0003] Among them, lithium-ion batteries, which are known to charge and discharge by the movement of lithium ions between the positive and negative electrodes, exhibit high voltage and high energy density. As a typical lithium-ion battery, there is a lithium-ion battery (LIB) that has active materials in both the positive and negative electrodes that can retain lithium elements, and charges and discharges by accepting and transferring lithium ions between these active materials.

[0004] For example, Patent Document 1 discloses an energy storage device characterized by comprising an anode, a cathode, at least one diaphragm 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 mounted on the at least one thin-film current collector. The tab is mounted on the current collector via a connecting device, which electrically connects the exposed surface of the tab to the thin-film current collector. Either the anode or the cathode is located between at least a portion of the thin-film current collector and the diaphragm. The current collector has a conductive material covering a non-conductive material substrate. Under the operating voltage of the energy storage device, the current collector stops conducting when a short circuit occurs, and the voltage is at least 2.0 volts.

[0005] In addition, Patent Document 2 discloses a current collector characterized by having a multilayer structure consisting of conductive layers sandwiching insulating layers, having a folded-back region where the ends are folded back twice or more in the same direction, wherein each conductive layer sandwiching the insulating layer in the folded-back region is electrically connected to each other, and the inner surfaces of the current collector ends forming the folded-back region are separated from each other or partially in contact.

[0006] In addition, Patent Document 3 discloses a lithium-ion secondary battery, characterized in that it comprises a positive electrode and a negative electrode formed by attaching an active material to a current collector via an adhesive, wherein the current collector of at least one of the positive electrode and the negative electrode comprises: a low-melting-point layer made of resin that melts when the battery abnormally heats up; and a metal layer between the low-melting-point layer and the active material for exchanging charge with the active material.

[0007] Existing technical documents

[0008] Patent documents

[0009] Patent Document 1: Japanese Patent Publication No. 2022-527140

[0010] Patent Document 2: Japanese Patent Application Publication No. 2013-016321

[0011] Patent Document 3: Japanese Patent Application Publication No. 11-102711 Summary of the Invention

[0012] The problem the invention aims to solve

[0013] Previously, pure copper foil or copper alloy foil were often used in the negative electrode to ensure conductivity. However, more recently, from the viewpoints of safety and weight reduction, as described in Patent Documents 1-3, current collector films with metal layers formed on both sides of the resin film are commonly used in the current collector. However, when multiple current collector leads made of such current collector films are soldered to the tabs, the cycle characteristics of the lithium-ion battery decrease due to the weld strength and connection resistance of the solder joints, and the temperature of the tabs sometimes rises during charging and discharging.

[0014] The present invention was made in view of the above circumstances, and its object is to provide a lithium secondary battery with excellent cycle characteristics and temperature stability of the tabs when the current collector film is ultrasonically welded.

[0015] Solution for solving the problem

[0016] An embodiment of the present invention relates to 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 a negative electrode current collector constituting the negative electrode extending from the laminate, the negative electrode tab leads and the negative electrode current collector comprising a resin layer and a copper layer formed on both sides of the resin layer, wherein in the 2θ pattern determined by X-ray diffraction of the copper layer, there is at least a peak A located at 42.9° or higher and 43.9° or lower, the intensity ratio (B / A) of a peak B located at 50.0° or higher and 51.0° or lower to the intensity of peak A is 0.3 or lower, and the half-width at half-maximum (FWHM) of peak A is 0.2° or lower.

[0017] Invention Effects

[0018] According to the present invention, a lithium secondary battery with excellent cycle characteristics and temperature stability of the tabs can be provided. Attached Figure Description

[0019] Figure 1 This is a schematic diagram illustrating an example of the lithium secondary battery of the present invention.

[0020] Figure 2 This is a schematic diagram illustrating an example of the negative electrode of the present invention.

[0021] Figure 3 This is a schematic diagram showing an example of a cross-section of the negative electrode of the present invention.

[0022] Figure 4 This is a schematic diagram illustrating an example of the connection between the negative electrode lead and the negative electrode tab in the lithium secondary battery of the present invention.

[0023] Figure 5 This is a schematic diagram illustrating an example of the connection between the negative electrode lead and the negative electrode tab in the lithium secondary battery of the present invention.

[0024] Figure 6 This is a schematic diagram illustrating an example of the connection between the negative electrode lead and the negative electrode tab in the lithium secondary battery of the present invention.

[0025] Figure 7 This is a schematic diagram illustrating an example of the lithium secondary battery of the present invention.

[0026] Figure 8 The image shows the 2θ pattern obtained from X-ray diffraction measurements in Example 3.

[0027] Figure 9 The image shows the 2θ pattern obtained from X-ray diffraction measurements in Example 4.

[0028] Figure 10 The image shows the 2θ pattern obtained from X-ray diffraction measurements in Example 5.

[0029] Figure 11 The image shows the 2θ pattern obtained from X-ray diffraction measurements of Comparative Example 4. Detailed Implementation

[0030] The following describes in detail the method for implementing the present invention (hereinafter referred to as "this embodiment"), but the present invention is not limited to the following embodiment. Various modifications can be made to the present invention without departing from its spirit. Furthermore, in the accompanying drawings, the same reference numerals are used to label the same elements, and repeated descriptions are omitted. In addition, unless otherwise specified, positional relationships such as up, down, left, and right are based on the positional relationships shown in the accompanying drawings. Moreover, the scale of the accompanying drawings is not limited to the scale shown in the drawings.

[0031] 1. Lithium secondary battery

[0032] Reference Figure 1 The basic structure of a lithium secondary battery according to one embodiment of the present invention will be described. For example... Figure 1 As shown, a 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, wherein the negative electrodes 10 and the positive electrodes 30 are separated by the separators 20. The structures will be described in detail below.

[0033] 1.1 Negative electrode

[0034] Figure 2 This is a perspective view showing an example of the negative electrode 10 in this embodiment. Figure 2 As shown, the negative electrode 10 of this embodiment has a negative electrode body portion 101 and a negative electrode tab lead portion 102. The negative electrode tab lead portion 102 is a portion that extends from the negative electrode body portion 101, constituting the negative electrode current collector. The negative electrode 10 includes a negative electrode current collector and may further have a negative electrode active material. Additionally, as... Figure 3 As shown, in this embodiment, the negative electrode 10 is composed only of a negative electrode current collector, which is composed of a negative electrode current collector film including a resin layer 202 and a copper layer 201 formed on both sides thereof.

[0035] like Figure 4 As shown, the negative electrode tab 11 overlaps with the negative electrode tab lead portion 102, which is the negative electrode side end of the battery stack A, forming a stack 12 of negative electrode tab lead portion, and is joined by welding. Examples of welding methods include ultrasonic welding, laser welding, resistance welding, or spot welding. In the lithium secondary battery of this embodiment, since welding of the stack including the resin layer 202 is required, ultrasonic welding is more suitable and preferred.

[0036] 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 a laminate, and negative electrode tabs 11 joined to the plurality of negative electrode tab lead portions. The negative electrode tab lead portions 102 are formed by extending the main body portion of the negative electrode current collector constituting the negative electrode 10 from the laminate. The negative electrode main body portion of the negative electrode current collector and the negative electrode tab lead portions 102 include a resin layer 202 and a copper layer 201 formed on both sides of the resin layer 202. In the 2θ pattern measured by X-ray diffraction of the copper layer 201, there is at least a peak A located at 42.9° or higher and 43.9° or lower, and the ratio of the intensity of peak B located at 50.0° or higher and 51.0° or lower to the intensity of peak A (B / A) is 0.3 or lower, and the half-width of peak A is 0.2° or lower.

[0037] In a lithium-ion secondary battery, which is a stack of structural elements, the negative electrode stack is joined from the negative electrode lead portion of each negative electrode current collector to the tab terminal, thereby extracting electrical energy from the lithium-ion secondary battery. Here, methods for joining the electrode lead portion to the tab terminal include ultrasonic welding, laser welding, resistance welding, spot welding, etc. However, when using a current collector film having a resin layer 202 and a copper layer 201 formed on both sides of the resin layer 202, since no current is passed through the resin layer 202, ultrasonic welding is often used.

[0038] Furthermore, the inventors have confirmed that even when ultrasonic welding is performed under the same conditions, the connection resistance increases due to factors such as localized welding, depending on the specifications of the current collector film. This results in room for improvement in the performance of the lithium secondary battery and the temperature stability of the tabs during charging and discharging. In-depth research was conducted on this point, and it was found that in the 2θ spectrum determined by X-ray diffraction of the copper layer 201, when the intensity ratio (B / A) of peak A (located at least 42.9° to 43.9° and peak B (located at 50.0° to 51.0°) to peak 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 is improved, and the temperature stability of the tabs during charging and discharging is also improved. The reasons for this are speculated below, but are not limited to these.

[0039] Peak A represents the orientation of the (111) plane in copper layer 201, and peak B represents the orientation of the (200) plane. If the intensity of peak B is less than or equal to the intensity of peak A, and the half-width of peak A is less than or equal to 0.2°, a state is formed in which the orientation and crystallinity of the (111) plane are maximized while suppressing the orientation of the (200) plane. It is speculated that the (111) plane is a slip plane of copper with a face-centered cubic lattice structure, and therefore is prone to shear deformation and plastic deformation, which is beneficial for welding by transverse vibration of ultrasonic waves, and the connection resistance between the negative electrode tab 11 and the negative electrode tab lead portion 102 decreases. Therefore, it is believed that the lithium secondary battery of this embodiment has excellent cycle characteristics and tab temperature stability during charging and discharging. However, the reasons are not limited to the above.

[0040] In this specification, the full width at half maximum (FWHM) refers to the 2θ width at exactly half the height of the peak in a 2θ pattern determined by X-ray diffraction.

[0041] The negative 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 This is a schematic diagram showing an example of a cross-section of a negative electrode 10 including a resin layer 202 and a copper layer 201 formed on both sides of the resin layer 202.

[0042] The thickness of the negative electrode current collector film in this embodiment is preferably 2.2 μm or more and 30 μm or less, 3.0 μm or more and 15 μm or less, 3.5 μm or more and 13 μm or less, or 5.0 μm or more and 10 μm or less. By keeping the thickness of the negative electrode current collector film 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 tabs tend to be improved.

[0043] The resin layer 202 preferably comprises at least one selected from polyethylene terephthalate (PET), polypropylene, polyamide, acrylic resin, polycarbonate, polyethylene, polyvinyl chloride, and polystyrene. Furthermore, the resin layer 202 is more preferably composed of polyethylene terephthalate or polypropylene. By forming the above-described resin layer 202, the ease of ultrasonic welding is improved, and the cycle characteristics and / or temperature stability of the battery tend to be improved.

[0044] The resin layer 202 is preferably in the form of a film (sheet), and its thickness is preferably 2.0 μm or more and 20 μm or less, 3.0 μm or more and 10 μm or less, or 4.0 μm or more and 7.0 μm or less. By keeping 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 tabs tend to be improved.

[0045] In this embodiment, the negative current collector is a copper (Cu) layer 201 formed on both sides of the resin layer 202 as a conductive layer. In this embodiment, the copper layer 201 refers to a copper layer with 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.

[0046] In the 2θ pattern determined by X-ray diffraction of the copper layer 201, there is at least a peak A located between 42.9° and 43.9°, but it may also be located between 43.0° and 43.8° or between 43.1° and 43.7°. The presence of peak A in the copper layer 201 indicates the formation of a (111) plane. Furthermore, in the copper layer 201, the half-width at half-maximum (WHM) of peak A is 0.2° or less, preferably less than 0.2°, and more preferably 0.18° or less. By keeping the WHM within this range, it indicates a higher crystallinity of the (111) plane. By using a negative electrode current collector containing a copper layer 201 exhibiting this orientation, the cycle characteristics of the battery and the temperature stability of the tab are improved.

[0047] Furthermore, in the 2θ spectrum of the copper layer 201, the ratio (B / A) of the intensity of peak B (between 50.0° and 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 dominant than that of the (200) plane. By using a negative electrode current collector comprising a copper layer 201 exhibiting this orientation, the cycle characteristics of the battery and the temperature stability of the tabs are improved. Additionally, the position of peak B can also be between 50.1° and 50.9°, or between 50.2° and 50.8°.

[0048] In the copper layer 201, the half-width at half-maximum (WHM) of peak B is preferably 0.5° or less, 0.3° or less, 0.2° or less, or 0.15° or less. By keeping the WHM of peak B within the above range, the cycle characteristics of the battery and the temperature stability of the tabs tend to be further improved. Alternatively, the WHM of peak B can also be 0.05° or more, or 0.1° or more.

[0049] In the copper layer 201, the intensity ratio (C / A) of peak C (between 73.7° and 74.7°) to 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 very dominant over that of the (220) plane. If a negative electrode current collector containing a copper layer 201 exhibiting such orientation is used, the cycle characteristics of the battery and the temperature stability of the tabs tend to be further improved. In addition, the position of peak C may also be between 73.8° and 74.6°, or between 73.9° and 74.5°.

[0050] In addition, X-ray diffraction measurements can be performed using commercially available X-ray diffraction apparatus according to previously known methods. For example, the "RINT-Ultima" (X-ray diffraction apparatus) manufactured by Rigaku Corporation can be considered for measurement using CuKα rays as the X-ray source.

[0051] The thickness of each copper layer 201 is preferably 0.2 μm or more and 10 μm or less, 0.3 μm or more and 5.0 μm or less, 0.5 μm or more and 3.0 μm or less, or 0.8 μm or more and 2.0 μm or less. 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 tabs tend to be improved.

[0052] 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 or more and 1.0 or less, 0.2 or more and 0.6 or less, or 0.35 or more and 0.5 or less. By keeping the ratio of the thickness of the copper layer 201 to the thickness of the resin layer 202 within the above range, the cycle characteristics of the battery and / or the temperature stability of the tabs tend to be improved.

[0053] As for the method of manufacturing the negative electrode current collector film of this embodiment, any method that can obtain a current collector film with the above-described characteristics is acceptable and is not particularly limited. A pre-manufactured product can be used, or it can be manufactured using conventionally known methods. As a known method, for example, the following method can be listed: using a substrate film (resin sheet) as the resin layer 202, sputtering or vapor deposition is performed on both sides thereon to form a copper layer 201.

[0054] Alternatively, for example, the following method can be considered: after sputtering or vapor deposition on both sides of the substrate film, the copper layer 201 can be further grown by electrolytic plating. When using this method, for example in sputtering, if the target power is increased, the orientation of the (111) facet tends to increase, and the crystallinity of the (111) facet also tends to increase. Therefore, in this embodiment, it is considered necessary to ensure that the target power is neither too high nor too low.

[0055] Furthermore, in vapor deposition, increasing the purity of the copper used tends to decrease orientation. Therefore, in this embodiment, it is considered necessary to use copper with a moderate purity. Moreover, increasing the vapor deposition rate and decreasing the cooling temperature tends to decrease orientation. Therefore, in this embodiment, it is considered necessary to adjust the vapor deposition rate to a moderate level and the cooling temperature to a moderate level.

[0056] Alternatively, the current collector film can be fabricated using the methods described in the embodiments described later.

[0057] The negative electrode active material refers to the material that undergoes electrode reactions, namely oxidation and reduction reactions, in the negative electrode 10. Specifically, examples of negative electrode active materials in this embodiment include lithium metal and lithium element (lithium ion or lithium metal) host materials. The lithium element host material refers to the material provided to retain lithium ions or lithium metal in the negative electrode 10. Examples of such retention mechanisms include intercalation, alloying, and metal cluster adsorption, with intercalation being typical.

[0058] There are no particular limitations on the negative electrode active material; examples include: lithium metal and alloys containing lithium metal, carbon-based materials, metal oxides, and metals that form alloys with lithium and alloys containing such metals. There are no particular limitations on the aforementioned carbon-based materials; examples include: graphene, graphite, hard carbon, carbon nanotubes, etc. There are no particular limitations on the aforementioned metal oxides; examples include: titanium oxide compounds, cobalt oxide compounds, etc. There are no particular limitations on the aforementioned metals that form alloys with lithium; examples include: silicon, germanium, tin, lead, aluminum, and gallium.

[0059] The lithium secondary battery in this embodiment can be an anode-free battery that substantially does not contain negative electrode active material, or it can contain negative electrode active material.

[0060] Anode-less lithium-ion batteries lack anode active material at their negative electrode 10, which is composed of anode current collector. During initial charging, lithium metal is deposited on the negative electrode 10, and charging and discharging occur through the electrolytic dissolution of this deposited lithium metal. Therefore, anode-less batteries offer the following advantages: the volume and mass of the negative electrode active material are reduced, resulting in a decrease in the overall volume and mass of the battery, thus theoretically leading to higher energy density.

[0061] 1.2 Negative electrode tab

[0062] When joining the laminate 12 of the negative electrode tab 11 and the negative electrode tab lead portion using ultrasonic welding, ultrasonic welding can be performed simultaneously with pressure. For example, when performing ultrasonic welding simultaneously with pressure... Figure 5 As shown, heat is generated at the negative electrode tab junction 13, and a portion of the negative electrode tab junction 13 tends to thin out.

[0063] like Figure 6 As shown, the negative electrode tab 11 preferably overlaps with the negative electrode tab lead portion of the laminate 12, which is formed by assembling components that sandwich an auxiliary metal foil 14 between the negative electrode side end of the battery laminate B, i.e., the negative electrode tab lead portion 102, and is joined by welding. By sandwiching the auxiliary metal foil 14, the thickness of the copper layer 201, which has become thinner due to ultrasonic welding, can be supplemented, and conductivity is more easily maintained. There is no particular limitation on the auxiliary metal foil 14; for example, electrolytic copper foil can be cited.

[0064] The negative electrode tab 11 may be made of at least one material selected from copper, titanium, stainless steel, nickel, and alloys thereof. Preferably, the negative electrode tab 11 is made of at least one material selected from copper, nickel, and alloys thereof, and more preferably, it is nickel-plated copper.

[0065] 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 keeping the thickness of the negative electrode tab 11 within the above range, the cycle characteristics and temperature stability of the tab of the lithium secondary battery tend to be further improved.

[0066] 1.3 Diaphragm

[0067] As for the separator 20 in this embodiment, there are no particular limitations as long as it has the functions of physically isolating and / or electrically isolating the positive electrode 30 and the negative electrode 10, and ensuring the ionic conductivity of lithium ions. Examples of such separators include insulating porous components, polymer electrolytes, gel electrolytes, and inorganic solid electrolytes. Typically, at least one selected from insulating porous components, polymer electrolytes, and gel electrolytes can be used. In addition, the separator 20 can be used alone or in combination with two or more components.

[0068] As the separator 20, it is preferable to use one or more of the following: an insulating porous component, a polymer electrolyte, or a gel electrolyte, or a combination of two or more. Furthermore, when an insulating porous component is used alone as the separator 20, the lithium secondary battery needs to further include an electrolyte.

[0069] There are no particular limitations on the polymer electrolytes mentioned above. Examples include: solid polymer electrolytes that mainly contain polymers and electrolytes, and semi-solid polymer electrolytes that mainly contain polymers, electrolytes and plasticizers.

[0070] There are no particular limitations on the above-mentioned gel electrolytes. For example, gel electrolytes that mainly consist of polymers and liquid electrolytes (i.e., solvents and electrolytes) can be listed.

[0071] There are no particular limitations on the polymers that can be included in polymer electrolytes and gel electrolytes. Examples include polymers containing functional groups with oxygen atoms, halogen groups, and polar groups such as cyano groups, such as ethers and esters. Specifically, examples include resins such as polyethylene oxide (PEO) with ethylene oxide units in the main chain and / or side chains, resins such as polypropylene oxide (PPO) with propylene oxide units in the main chain and / or side chains, acrylic resins, vinyl resins, ester resins, nylon resins, polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), polysiloxanes, polyphosphononitrile, polymethyl methacrylate, polyamides, polyimides, aramids, and polytetrafluoroethylene. The resins mentioned above can be used alone or in combination of two or more.

[0072] Examples of electrolytes included in polymeric electrolytes and gel electrolytes include salts of Li, Na, K, Ca, and Mg. Typically, in this embodiment, the polymeric electrolyte and gel electrolyte contain a lithium salt. There are no particular limitations on the lithium salt; any lithium salt that can be contained in the electrolyte described later is acceptable. This salt or lithium salt can be used alone or in combination of two or more.

[0073] The ratio of polymer to lithium salt in polymer electrolytes and gel electrolytes can be determined based on the ratio of polar groups in the polymer to lithium atoms in the lithium salt. For example, if the polymer has oxygen atoms, it can be determined based on the ratio of the number of oxygen atoms in the polymer to the number of lithium atoms in the lithium salt ([Li] / [O]). In polymer electrolytes and gel electrolytes, the ratio of polymer to lithium salt can be adjusted to the above ratio ([Li] / [O]) for example, 0.02 or more and 0.20 or less, 0.03 or more and 0.15 or less, or 0.04 or more and 0.12 or less.

[0074] There are no particular limitations on the solvent contained in the gel electrolyte; for example, one of the solvents that can be contained in the electrolyte described later can be used alone or in combination of two or more. Examples of preferred solvents are also the same as those for the solvents in the electrolyte described later.

[0075] There are no particular limitations on the plasticizers contained in semi-solid polymer electrolytes. Examples include components that are the same as those that can be contained in gel electrolytes and various oligomers.

[0076] When the diaphragm 20 includes an insulating porous component, the component exhibits ion conductivity by filling the pores of the component with a substance that has ion conductivity. Therefore, in this embodiment, for example, the electrolyte of this embodiment and a gel electrolyte containing the electrolyte of this embodiment are filled.

[0077] There are no particular limitations on the materials used to form the porous insulating components. For example, insulating polymer materials can be listed, specifically polyethylene (PE) and polypropylene (PP). That is, the diaphragm 20 can be a porous polyethylene (PE) membrane, a porous polypropylene (PP) membrane, or a laminate of these membranes.

[0078] 1.4 Positive electrode

[0079] The positive electrode 30 in this embodiment has a positive current collector and a positive active material layer. The average thickness of the positive electrode 30 is not particularly limited, and for example, it can be 20 μm or more and 100 μm or less, 30 μm or more and 80 μm or less, or 40 μm or more and 70 μm or less. However, the average thickness of the positive electrode 30 can be appropriately adjusted according to the desired battery capacity.

[0080] 1.4.1 Positive Current Collector

[0081] The positive current collector in this embodiment may have a positive current collector film, which includes a resin layer containing polyethylene terephthalate and metal layers disposed on both sides of the resin layer, or it may have a metal layer but no resin layer. When a positive current collector film is provided, the metal layers are formed by vapor deposition, sputtering, electroplating, or by attaching them to the surfaces of both sides of the resin layer using an adhesive.

[0082] The resin layer of the positive current collector is an insulator, preventing the metal layers on both sides of the resin layer from conducting to each other. There is no particular limitation on the resin constituting the resin layer; for example, it can be composed of sheet (film) or fibrous resin. The resin may contain at least one selected from polyethylene terephthalate (PET), polypropylene, polyamide, acrylic resin, polycarbonate, polyethylene, polyvinyl chloride, and polystyrene. The above-mentioned resins may be used alone or in combination of two or more.

[0083] In addition to the resins mentioned above, the resin layer of the positive current collector may also contain other additives depending on the desired physical properties. There are no particular limitations on the additives; examples include colorants, flame retardants, and surfactants.

[0084] The thickness of the resin layer of the positive 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.

[0085] The metal layer of the positive electrode current collector is in physical and / or electrical contact with the positive electrode active material layer, functioning by accepting and donating electrons to the positive electrode active material layer. The metal layer of the positive electrode current collector is composed of a conductive material such as a metal that does not react with lithium in the battery. There is no particular limitation on the metal constituting the metal layer of the positive electrode current collector; it is selected from at least one of aluminum, titanium, stainless steel, nickel, and alloys thereof. Aluminum or aluminum alloys are preferred, and aluminum is particularly preferred. One metal may be used alone or in combination of two or more. Furthermore, in this specification, "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.

[0086] When the positive current collector has a positive current collector film, there is no particular limitation on the thickness of the metal layer, for example, it can be 0.1μm or more and 4.0μm or less, 0.2μm or more and 3.0μm or less, 0.3μm or more and 2.5μm or less, or 0.4μm or more and 2.0μm or less.

[0087] When the positive current collector has a metal layer but no resin layer, there is no particular limitation on the thickness of the metal layer, for example, it can be 4.0 μm or more and 20.0 μm or less, 6.0 μm or more and 17.5 μm or less, or 8.0 μm or more and 15.0 μm or less.

[0088] 1.4.2 Positive Electrode Active Material

[0089] The positive electrode active material refers to the substance that undergoes electrode reactions, namely oxidation and reduction reactions, in the positive electrode 30. There is no particular limitation on the positive electrode active material in this embodiment; for example, it may be included in a positive electrode active material composition containing a binder, conductive additive, sacrificial positive electrode agent, and other additives. The positive electrode active material layer is disposed on at least one or both sides of the positive electrode current collector by coating the positive electrode active material composition onto at least one or both sides of the positive electrode current collector and pressing it into shape.

[0090] Methods for configuring a positive electrode active material layer on a positive electrode current collector are not limited to compression molding. Examples include: a method of including a thermosetting compound in a positive electrode active material composition and heating it to cure it; a method of including a photocurable compound in a positive electrode active material composition and irradiating it with light to cure it; and a method of curing a positive electrode active material composition as a two-component curable composition by mixing the two components.

[0091] The positive electrode active material layer in this embodiment may contain one or more substances of the general formula Li. z Ni x Co y M 1-x-y O 2+α(where 0.5≤x≤1.0, 0≤y≤0.35, 0.9≤z≤1.3, -0.2≤α≤0.15, and M is a compound selected from one or more elements selected from Mn, Al, V, Mg, Mo, Nb, Ti, Zr, Fe, Cu, Cr, Zn, F and B)

[0092] Furthermore, preferably, the positive electrode active material layer contains one or more substances of the general formula Li. z Ni x Co y M 1-x-y O 2+α (where 0.7≤x≤1.0, 0≤y≤0.35, 0.9≤z≤1.3, -0.2≤α≤0.15, and M is an element selected from Mn, Al, V, Mg, Mo, Nb, Ti, Zr, Fe, Cu, Cr, Zn, F, and B) represents the compound. By using the above-mentioned compound with a high nickel content as the positive electrode active material, the energy density of lithium secondary batteries tends to be further improved. In addition, if the nickel content is increased, redox shuttle reaction is more likely to occur, but by including the additives detailed below in the electrolyte, this reaction tends to be suppressed, resulting in excellent performance stability at high temperatures.

[0093] As the positive electrode active material, other positive electrode active materials besides the compounds mentioned above may be included. Specifically, other positive electrode active materials in this embodiment may include: host materials for lithium (typically lithium ions). There are no particular limitations on such other positive electrode active materials; for example, metal oxides and metal phosphates may be included. There are no particular limitations on the aforementioned metal oxides; for example, cobalt oxide compounds, manganese oxide compounds, and nickel oxide compounds may be included. There are no particular limitations on the aforementioned metal phosphates; for example, iron phosphate compounds and cobalt phosphate compounds may be included. Typical other positive electrode active materials may include: LiCoO2, LiNi... x Mn y O(x+y=1), LiNiO2, LiMn2O4, LiFePO4, LiCoPO4, LiFeOF, LiNiOF, and TiS2. Other positive electrode active materials can be used alone or in combination of two or more.

[0094] The positive electrode active material composition may include a binder. By including a binder, the positive electrode active material layer is more easily bonded to the positive electrode current collector, and the flexibility is improved after the positive electrode active material layer is disposed on the positive electrode current collector.

[0095] The adhesive used in this embodiment is not particularly limited, but examples include: polyvinylidene fluoride (PVDF); modified PVDF obtained by introducing functional groups such as hydroxyl, amino, carbonyl, carboxyl, phenyl, and methyl groups into PVDF; polytetrafluoroethylene (PTFE); modified PTFE obtained by introducing functional groups such as hydroxyl, amino, carbonyl, carboxyl, phenyl, and methyl groups into PTFE; block copolymers, random copolymers, or graft copolymers having PTFE as a structural unit; styrene-butadiene rubber; carboxymethyl cellulose; acrylic resin; polyimide resin, etc. One adhesive may be used alone or in combination of two or more.

[0096] The positive electrode active material composition of this embodiment may include a sacrificial positive electrode agent. The sacrificial positive electrode agent in this embodiment refers to a lithium-containing compound that undergoes oxidation within the charge / discharge potential range of the positive electrode active material and substantially does not undergo reduction. There is no particular limitation on the sacrificial positive electrode agent; examples include: lithium oxides such as Li₂O₂; lithium nitrides such as Li₃N; lithium sulfide solid solutions such as Li₂S-P₂S₅, Li₂S-LiCl, Li₂S-LiBr, and Li₂S-LiI; and Li… 1+x (Ti 1-y Fe y ) 1-x O2(0<x≤0.25, 0.4<y≤0.9), Li 2-x Ti 1-z Fe z O 3-y Iron-based lithium oxides such as Li5FeO4 (0≤x<2、0≤y≤1、0.05≤z≤0.95) can be used. Sacrificial cathode agents can be used alone or in combination of two or more.

[0097] 1.5 Positive electrode tab

[0098] The positive electrode tab overlaps with the positive electrode tab lead portion, which is a laminated body formed by the positive electrode side end, and is joined by welding. Examples of welding methods include ultrasonic welding, laser welding, resistance welding, or spot welding. Ultrasonic welding is suitable when the positive electrode tab lead portion contains a resin layer.

[0099] The positive electrode tab can be made of, for example, aluminum or an aluminum alloy. In one example, the positive electrode tab can be made of hard aluminum. The thickness of the positive electrode tab can be, for example, 0.05 mm or more and 1 mm or less, or 0.1 mm or more and 0.5 mm or less.

[0100] 1.6 Electrolyte

[0101] Lithium-ion rechargeable batteries may include an electrolyte. An electrolyte is a liquid containing a solvent and an electrolyte, possessing ionic conductivity. The electrolyte, also known as a liquid electrolyte, acts as the conductive pathway for lithium ions. Therefore, when a lithium-ion rechargeable battery contains an electrolyte, its internal resistance decreases, and its energy density, capacity, and cycle characteristics can be improved.

[0102] The electrolyte is, for example, a solution that fills the casing (soft pack) of a lithium secondary battery. Alternatively, the electrolyte can be impregnated in the separator 20, or it can be contained within a polymer to form a polymer electrolyte or a gel electrolyte.

[0103] The electrolyte in the electrolyte solution can be any lithium salt. For example, the lithium salt can be one or a combination of two or more selected from LiI, LiCl, LiBr, LiF, LiBF4, LiPF6, LiAsF6, LiSO3CF3, LiN(SO2F)2, LiN(SO2CF3)2, LiN(SO2CF3CF3)2, LiB(O2C2H4)2, LiB(C2O4)2, LiB(O2C2H4)F2, LiB(OCOCF3)4, LiNO3, and Li2SO4.

[0104] As solvents contained in the electrolyte, for example, non-aqueous solvents having fluorine atoms (hereinafter referred to as "fluorinated solvents") and non-aqueous solvents without fluorine atoms (hereinafter referred to as "non-fluorinated solvents") can be added.

[0105] 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.

[0106] Examples of non-fluorinated 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, 12-crown ether-4, etc.

[0107] The aforementioned fluorinated solvent and / or non-fluorinated solvent may be used alone or in any combination of two or more in any proportion. There is no particular limitation on the content of fluorinated solvent and non-fluorinated solvent. The proportion of fluorinated solvent relative to the total solvent volume may be 0 to 100% by volume, and the proportion of non-fluorinated solvent relative to the total solvent volume may be 0 to 100% by volume.

[0108] 2. Manufacturing method of lithium secondary batteries

[0109] As for the manufacturing method of lithium secondary batteries, any method that can manufacture lithium secondary batteries with the above-described battery structure is acceptable, and there are no particular limitations. For example, the following methods can be listed.

[0110] Prepare the aforementioned negative electrode 10, separator 20, and positive electrode 30. The structural components and reagents used in these components can be manufactured using conventional methods or commercially available products. Stack the prepared positive electrode 30, separator 20, and negative electrode 10 in this order, with the positive electrode 30 facing the separator 20, to obtain a laminate. Seal the resulting laminate together with the electrolyte into a sealed container to obtain a lithium secondary battery. There are no particular limitations on the sealed container; for example, a laminated membrane can be used.

[0111] In addition, such as Figure 1 As shown, a separator 20 can be sandwiched between the positive electrode 30 and the negative electrode 10, and the positive electrode 30 and the negative electrode 10 can be alternately stacked in multiple layers, thereby tending to further improve battery performance such as energy density. As a stacking method, for example... Figure 7 As shown, the negative electrode 10 and the positive electrode 30 can be coated without contacting each other, facing the opposite side of the diaphragm 20, and the layers can be stacked without cutting the diaphragm 20. From the viewpoint of preventing short circuits and improving productivity, such a stacking is preferred.

[0112] In the case of manufacturing lithium-ion batteries, except for using lithium as a host material in the negative electrode 10, it can be manufactured in the same manner as the battery manufacturing method described above. There are no particular limitations on the manufacturing method of the negative electrode 10 having this host material (negative electrode active material), for example, as described below. As needed, the aforementioned negative electrode active material is mixed with the binder, conductive agent, and other additives detailed below to obtain a negative electrode active material composition. The negative electrode active material or the obtained negative electrode active material composition is coated onto both sides or one side of the aforementioned negative electrode current collector, and then pressed and molded to form a negative electrode active material layer on both sides or one side of the negative electrode current collector, obtaining a molded body. The obtained molded body is punched to a specified size by a punching process to obtain the negative electrode 10 of this embodiment.

[0113] The lithium secondary battery of this embodiment can be manufactured into an anode-free lithium battery, a lithium-ion battery, a lithium metal battery, a lithium-sulfur battery, a lithium-oxygen battery, and a lithium-air battery by changing the added structure or the components used in each structure. Among them, the structures of the anode-free lithium battery, the lithium-ion battery, and the lithium metal battery are particularly suitable.

[0114] The shape of the lithium secondary battery in this embodiment is not particularly limited; for example, it can be a sheet type, a stacked sheet type, a thin shape, a bottomed cylindrical shape, a bottomed square shape, etc. From the viewpoint of more effectively and reliably achieving the effects of this embodiment, a sheet type, a stacked sheet type, or a thin shape is preferred.

[0115] Example

[0116] The present invention will be further described in detail below through embodiments, but the present invention is not limited to these embodiments. Furthermore, unless otherwise specified, all measurements are performed at room temperature (25°C) and atmospheric pressure (10... 5 Performed under (Pa).

[0117] 1. Manufacturing of lithium secondary batteries

[0118] The following procedures were followed to fabricate lithium-ion secondary batteries for the examples and comparative examples.

[0119] 1.1 Preparation of the negative electrode

[0120] 1.1.1 Preparation of the negative current collector

[0121] (Example 1)

[0122] As the negative current collector, a 4.5 μm polypropylene film obtained by injection molding was used, and vapor deposition and electroplating were performed according to the following steps.

[0123] First, a polypropylene membrane was placed in a vapor deposition apparatus, and a 50 nm thick copper film was formed on both sides of the polypropylene membrane. Then, electrolytic plating with copper sulfate was performed until the copper layer thickness on the membrane surface reached 1.0 μm, resulting in a current collector film. A negative electrode active material layer was formed using the method described later, and the negative electrode body (4 cm × 4 cm) with negative electrode tab leads of 0.5 cm × 3 cm was punched out, resulting in a negative electrode with a thickness of 100 μm.

[0124] (Example 2)

[0125] A 4.5 μm thick polypropylene film, as used in Example 1, was prepared. Using this polypropylene film, sputtering and electroplating processes were performed according to the following steps.

[0126] First, a polypropylene membrane was placed in a vacuum chamber for sputtering, where copper ions were generated to form a 50 nm thick copper film on both sides of the membrane. Then, the membrane was treated with copper sulfate electroplating until the copper layer thickness on each surface reached 1.0 μm, resulting in the current collector film of Example 2. A negative electrode active material layer was formed using the method described later, and the negative electrode was punched into the same size and shape as in Example 1, thus obtaining the negative electrode.

[0127] (Example 3)

[0128] As the negative electrode current collector, a current collector was prepared using a 4.5 μm PET film with 1.0 μm copper thin films formed on both sides of the film. Then, a negative electrode active material layer was formed using the method described later, and the negative electrode was punched into the same size and shape as in Example 1, thus obtaining the negative electrode. The 2θ pattern obtained by X-ray diffraction of this current collector film is shown below. Figure 8 .

[0129] (Example 4)

[0130] As the negative electrode current collector, a current collector was prepared using a 6.0 μm PET film with 1.0 μm copper thin films formed on both sides of the film. Then, a negative electrode active material layer was formed using the method described later, and the negative electrode was punched into the same size and shape as in Example 1, thus obtaining the negative electrode. The 2θ pattern obtained by X-ray diffraction of this current collector film is shown below. Figure 9 .

[0131] (Example 5)

[0132] As the negative electrode current collector, a current collector was prepared using a 4.5 μm polypropylene film with 1.0 μm copper films formed on both sides of the film. Then, a negative electrode active material layer was formed using the method described later, and the negative electrode was punched into the same size and shape as in Example 1, thus obtaining the negative electrode. The 2θ pattern obtained by X-ray diffraction of this current collector film is shown below. Figure 10 .

[0133] (Comparative Example 1)

[0134] As the negative current collector, a 6.0 μm PET film obtained by injection molding was used, and vapor deposition and electroplating were performed according to the following steps. First, the PET film was placed in a vapor deposition apparatus, and a 50 nm copper film was formed on both sides of the PET film. Then, electroplating with copper sulfate was performed until the copper layer thickness on the film surface reached 1.0 μm, thus obtaining the current collector film of Comparative Example 1.

[0135] Then, the negative electrode active material layer is formed using the method described later, and the negative electrode is punched into the same size and shape as in Example 1 to obtain the negative electrode.

[0136] (Comparative Example 2)

[0137] As the negative electrode current collector, a 4.5 μm polypropylene film obtained by injection molding was used, and vapor deposition and electroplating were performed according to the following steps. First, the polypropylene film was placed in a vapor deposition apparatus, and a 50 nm copper film was formed on both sides of the polypropylene film. Then, electroplating with copper sulfate was performed until the copper layer thickness on the film surface reached 1.0 μm, thus obtaining the current collector film of Comparative Example 2.

[0138] Then, the negative electrode active material layer is formed using the method described later, and the negative electrode is punched into the same size and shape as in Example 1 to obtain the negative electrode.

[0139] (Comparative Example 3)

[0140] As the negative electrode current collector, a 4.5 μm polypropylene film obtained by injection molding was used, and vapor deposition and electroplating were performed according to the following steps. First, the polypropylene film was placed in a vapor deposition apparatus, and a 50 nm copper film was formed on both sides of the polypropylene film. Then, electroplating with copper sulfate was performed until the copper layer thickness on the film surface reached 1.0 μm, thus obtaining the current collector film of Comparative Example 3.

[0141] Then, the negative electrode active material layer is formed using the method described later, and the negative electrode is punched into the same size and shape as in Example 1 to obtain the negative electrode.

[0142] (Comparative Example 4)

[0143] As the negative electrode current collector, a current collector was prepared using a 6.0 μm PET film with 1.0 μm copper thin films formed on both sides of the film. Then, a negative electrode active material layer was formed using the method described later, and the negative electrode was punched into the same size and shape as in Example 1, thus obtaining the negative electrode. The 2θ pattern obtained by X-ray diffraction of this current collector film is shown below. Figure 11 .

[0144] The negative electrode current collector film obtained above was subjected to X-ray diffraction measurement using a "RINT-Ultima" manufactured by Rigaku Corporation. The peaks were detected and the full width at half maximum (FWHM) was calculated using the software included with the instrument.

[0145] 1.1.2 Formation of the negative electrode active material layer

[0146] A negative electrode active material composition was prepared by mixing 97.0 parts by weight of graphite as the negative electrode active material, 0.5 parts by weight of carbon black as a conductive additive, and 1.5 parts by weight of carboxymethyl cellulose (CMC) and 1.0 parts by weight of styrene-butadiene rubber (SBR) as binders in water as a solvent. This negative electrode active material composition was then coated onto a portion of one side of each of the aforementioned negative electrode current collector films and pressed to achieve a weight per unit area of ​​15 mg / cm². 2 A negative electrode active material layer is formed on one side of the negative electrode current collector. In this molded body, the negative electrode of each example is obtained by punching in such a way that the part with the negative electrode active material layer formed becomes the negative electrode current collector part, and the part without the negative electrode active material layer formed becomes the negative electrode lead part.

[0147] 1.2 Preparation of the positive electrode

[0148] A current collector film consisting of a 6.0 μm thick PET film as a resin layer and 1.0 μm thick aluminum metal layers deposited on both sides is used as the positive electrode current collector. Then, 96 parts by mass of LiNi as the positive electrode active material are mixed in N-methylpyrrolidone (NMP) as a solvent. 0.8 Co 0.15 Al 0.05 A positive electrode active material composition was prepared by using O2, 2 parts by weight of carbon black as a conductive additive, and 2 parts by weight of polyvinylidene fluoride (PVDF) as a binder. The positive electrode active material composition was then subjected to a surface area weight ratio of 15 mg / cm². 2 The material is coated onto one side of the positive electrode current collector and then extruded to form a positive electrode active material layer on that side, resulting in a molded body. This molded body is then punched to a specified size (4cm × 4cm). This yields positive electrode 30.

[0149] 1.3 Preparation of the diaphragm

[0150] A polyethylene microporous membrane sheet (thickness: 15 μm, 4 cm × 4 cm) coated with a mixture of polyvinylidene fluoride (PVDF) and Al2O3 was prepared as the diaphragm 20.

[0151] 1.4 Electrolyte Preparation

[0152] Lithium hexafluorophosphate (LiPF6) was dissolved at a concentration of 1 M in a solvent prepared by mixing ethylene carbonate (EC) and dimethyl carbonate (DMC) in a volume ratio of 3:7. Lithium difluorophosphate (LiPO2F2) and ethylene carbonate (VC) were then added to the solvent to achieve a content ratio of 1% by mass and 2% by mass relative to the total amount of the solvent (total mass of EC and DMC, excluding LiPF6), respectively. The electrolyte was prepared as described above.

[0153] 1.5 Battery Assembly

[0154] The positive electrode 30, separator 20, and negative electrode 10 obtained by the above operation are as follows: Figure 1 The positive electrode 30 and the separator 20 are stacked multiple times in this order to obtain a laminate. Then, the leads of the stacked positive and negative electrodes are ultrasonically welded together to form terminals, i.e., a 100 μm Al terminal is joined to the positive electrode and a 100 μm Ni terminal is joined to the negative electrode, and then inserted into the laminated outer casing. Then, the electrolyte obtained above is injected into the outer casing for sealing, thereby obtaining the lithium-ion secondary batteries of each embodiment and comparative example.

[0155] 2. Evaluation of lithium secondary batteries

[0156] 2.1 Rate maintenance rate

[0157] The lithium secondary battery obtained above was initially charged to 4.2V at a charging rate of 0.1C at 25°C, and then initially discharged to 3.0V at a discharging rate of 0.1C. Then, it was charged again at 0.1C to 4.2V, and after charging, it was discharged at 3C. The ratio of the discharge capacity at the discharge rate of 3.0C obtained from the above operation to the initial discharge capacity (discharge rate of 0.1C) was calculated as the rate maintenance rate (%).

[0158] 2.2 Temperature of the tabs when energized

[0159] After the rate maintenance rate measurement, each lithium secondary battery was charged again at a charging rate of 0.1C to 4.2V, and then discharged at a charging rate of 10C to 2.5V. After the discharge was completed, the temperature (°C) of the central part of the negative electrode tab was measured after 2 minutes. The lower the tab temperature, the less heat is generated, therefore the tab temperature stability is considered to be excellent.

[0160] [Table 1]

[0161]

[0162] As shown in Table 1, Examples 1 to 5 comprise: a laminate containing multiple negative electrodes, multiple diaphragms, and multiple positive electrodes; and negative electrode tabs joined to multiple negative electrode tab leads extending from the laminate. The negative electrode tab leads are formed by a negative electrode current collector constituting the negative electrode extending from the laminate. The negative electrode tab leads and the negative electrode current collector comprise a resin layer and copper layers formed on both sides of the resin layer. In the 2θ pattern determined by X-ray diffraction of the copper layer, there is at least a peak A located at 42.9° or higher and 43.9° or lower, and the ratio of the intensity of peak B located at 50.0° or higher and 51.0° or lower to the intensity of peak A (B / A) is 0.3 or lower, and the half-width of peak A is 0.2° or lower. Compared with Comparative Examples 1 to 4, which do not have this structure, Examples 1 to 5 are found to be superior in terms of rate characteristics and tab temperature stability during energization.

[0163] <Note>

[0164] The embodiments disclosed herein include the following schemes.

[0165] [1] A lithium secondary battery, comprising:

[0166] A laminate containing multiple negative electrodes, multiple separators, and multiple positive electrodes;

[0167] Multiple negative electrode lead portions extending from the laminated body; and

[0168] Negative electrode tabs that are engaged with the lead portions of the plurality of negative electrode tabs.

[0169] The negative electrode tab lead portion is formed by the negative electrode current collector extending from the laminate, which constitutes the negative electrode.

[0170] 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.

[0171] In the 2θ pattern determined by X-ray diffraction of the copper layer, there is at least one peak A located above 42.9° and below 43.9°.

[0172] The ratio of the intensity of peak B (located above 50.0° and below 51.0°) to the intensity of peak A (B / A) is 0.3 or less.

[0173] The half-width at half maximum (FWHM) of peak A is less than 0.2°.

[0174] [2] According to the lithium secondary battery described in [1], wherein,

[0175] The ratio of the intensity of peak C, which is located above 73.7° and below 74.7°, to the intensity of peak A (C / A) is 0.3 or less.

[0176] [3] The lithium secondary battery according to [1] or [2], wherein the half-peak width of peak B is greater than 0.1°.

[0177] [4] The lithium secondary battery according to any one of [1] to [3], wherein,

[0178] The average thickness of the resin layer is greater than 3.0 μm and less than 10.0 μm.

[0179] The average thickness of the copper layer is greater than 0.5 μm and less than 3.0 μm.

[0180] [5] The lithium secondary battery according to any one of [1] to [4], wherein,

[0181] The resin layer comprises at least one selected from polyethylene terephthalate, polypropylene, polyamide, acrylic resin, polycarbonate, polyethylene, polyvinyl chloride and polystyrene.

[0182] [6] The lithium secondary battery according to any one of [1] to [5], wherein,

[0183] The resin layer is composed of polyethylene terephthalate or polypropylene.

[0184] [7] The lithium secondary battery according to any one of [1] to [6], wherein,

[0185] Used to join the electrode lead portion to the electrode by ultrasonic welding.

[0186] Industrial availability

[0187] The lithium secondary battery involved in this invention has excellent cycle characteristics and temperature stability of the tabs, and therefore has industrial applicability as an energy storage device for various purposes.

[0188] Explanation of reference numerals in the attached figures

[0189] A, B: Battery laminate; 10: Negative electrode; 11: Negative electrode tab; 12: Laminated section of negative electrode tab lead; 13: Negative electrode tab junction; 14: Auxiliary metal foil; 20: Separator; 30: Positive electrode; 101: Negative electrode body; 102: Negative electrode tab lead; 201: Copper layer; 202: Resin layer. Claims (as amended under Article 19 of the Treaty) 1. A lithium secondary battery, comprising: A laminate containing multiple negative electrodes, multiple separators, and multiple positive electrodes; Multiple negative electrode lead portions extending from the laminated body; and Negative electrode tabs that are engaged with the lead portions of the plurality of negative electrode tabs. The negative electrode tab lead portion is formed by the negative electrode current collector extending from the laminate, which constitutes the negative electrode. 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. In the 2θ pattern determined by X-ray diffraction of the copper layer, there is at least one peak A located above 42.9° and below 43.9°. The ratio of the intensity of peak B (located above 50.0° and below 51.0°) to the intensity of peak A (B / A) is 0.3 or less. The half-width at half maximum (FWHM) of peak A is less than 0.2°. The half-width of peak B is less than 0.5°. 2. The lithium secondary battery according to claim 1, wherein, The ratio of the intensity of peak C, which is located above 73.7° and below 74.7°, to the intensity of peak A (C / A) is 0.3 or less. 3. The lithium secondary battery according to claim 1, wherein, The average thickness of the resin layer is greater than 3.0 μm and less than 10.0 μm. The average thickness of the copper layer is greater than 0.5 μm and less than 3.0 μm. 4. The lithium secondary battery according to claim 1, wherein, The resin layer comprises at least one selected from polyethylene terephthalate, polypropylene, polyamide, acrylic resin, polycarbonate, polyethylene, polyvinyl chloride and polystyrene. 5. The lithium secondary battery according to claim 1, wherein, The resin layer is composed of polyethylene terephthalate or polypropylene. 6. The lithium secondary battery according to claim 1, wherein, The negative electrode lead wire is joined to the negative electrode tab by ultrasonic welding.

Claims

1. A lithium secondary battery, comprising: A laminate containing multiple negative electrodes, multiple separators, and multiple positive electrodes; Multiple negative electrode lead portions extending from the laminated body; and Negative electrode tabs that are engaged with the lead portions of the plurality of negative electrode tabs. The negative electrode tab lead portion is formed by the negative electrode current collector extending from the laminate, which constitutes the negative electrode. 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. In the 2θ pattern determined by X-ray diffraction of the copper layer, there is at least one peak A located above 42.9° and below 43.9°. The ratio of the intensity of peak B (located above 50.0° and below 51.0°) to the intensity of peak A (B / A) is 0.3 or less. The half-width of peak A is less than 0.2°.

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

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

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

5. The lithium secondary battery according to claim 1, wherein, The resin layer comprises at least one selected from 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 composed of polyethylene terephthalate or polypropylene.

7. The lithium secondary battery according to claim 1, wherein, The negative electrode lead wire is joined to the negative electrode tab by ultrasonic welding.

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