Non-aqueous electrolyte storage element and storage device

Abstract

To provide a nonaqueous electrolyte power storage element and a power storage device which enable the suppression of the increase in resistance at low temperature accompanying a charge / discharge cycle.SOLUTION: A nonaqueous electrolyte power storage element comprises: an electrode body 2 in which negative and positive electrodes are laminated through a separator; a nonaqueous electrolyte; and a container 3 which contains the electrode body 2. The container 3 receives a pressure in a thickness direction of the electrode body 2. The separator has an inorganic particle layer. The positive electrode has a positive electrode active material layer containing a positive electrode active material. The positive electrode active material layer is laminated on the inorganic particle layer. The positive electrode active material includes a transition metal oxide. In a lamination plane of the positive electrode active material layer with the inorganic particle layer, the percentage of elements forming the positive electrode active material to all of elements is smaller than 38 atom%.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a non-aqueous electrolyte storage element and a power storage device.

Background Art

[0002] Non-aqueous electrolyte secondary batteries typified by lithium-ion non-aqueous electrolyte secondary batteries are widely used in electronic devices such as personal computers and communication terminals, and automobiles because of their high energy density. Generally, the non-aqueous electrolyte secondary battery includes an electrode body having a pair of electrodes electrically isolated by a separator, and a non-aqueous electrolyte interposed between the electrodes, and is configured to charge and discharge by transferring ions between both electrodes. In addition, as non-aqueous electrolyte storage elements other than non-aqueous electrolyte secondary batteries, capacitors such as lithium-ion capacitors and electric double layer capacitors are also widely spread.

[0003] The electrodes of the non-aqueous electrolyte storage element expand by repeating charge and discharge. Therefore, when forming a power storage device by stacking a plurality of flat non-aqueous electrolyte storage elements, in order to maintain the dimensions of the power storage device, a method of assembling the non-aqueous electrolyte storage elements in a state of being compressed in the stacking direction is adopted. As the non-aqueous electrolyte storage element, for example, a flat non-aqueous electrolyte secondary battery including a flat electrode body having a structure in which a positive electrode plate and a negative electrode plate are stacked via a separator, and a non-aqueous electrolyte solution, wherein the flat portion of the flat non-aqueous electrolyte secondary battery is subjected to pressure from the outside in the stacking direction of the positive electrode plate, the negative electrode plate, and the separator, so that a pressure of 8.83×10 -2 MPa or more is applied to the electrode body, and a flat non-aqueous electrolyte secondary battery is disclosed (see Japanese Patent Application Laid-Open No. 2018-26352).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In recent years, from the viewpoint of imparting heat resistance and the like, separators having an inorganic particle layer have been adopted, and in some cases, the positive electrode active material layer and the inorganic particle layer of the separator are opposed to each other. In a power storage device including a non-aqueous electrolyte storage element in which the positive electrode active material layer and the inorganic particle layer of the separator are opposed to each other, when the non-aqueous electrolyte storage element is repeatedly charged and discharged in a compressed state, the positive electrode expands, and contact and friction between the positive electrode active material and the inorganic particles may occur, and cracks or the like in the positive electrode active material may occur. Such cracks in the positive electrode active material may lead to an increase in resistance at low temperatures of the non-aqueous electrolyte storage element.

[0006] The present invention has been made based on the above circumstances, and an object of the present invention is to provide a non-aqueous electrolyte storage element capable of suppressing an increase in resistance at low temperatures associated with charge and discharge cycles when a compressed electrode body is provided, and a power storage device capable of suppressing an increase in resistance at low temperatures associated with charge and discharge cycles.

Means for Solving the Problems

[0007] A non-aqueous electrolyte storage element according to an aspect of the present invention includes an electrode body in which a negative electrode and a positive electrode are laminated via a separator, a non-aqueous electrolyte, and a container that houses the electrode body, the container being compressed in the thickness direction of the electrode body, the separator having an inorganic particle layer, the positive electrode having a positive electrode active material layer containing a positive electrode active material, the positive electrode active material layer being laminated on the inorganic particle layer, the positive electrode active material containing a transition metal oxide, and on the lamination surface of the positive electrode active material layer with the inorganic particle layer, the ratio of the elements constituting the positive electrode active material to all elements is less than 38 atomic %.

Effects of the Invention

[0008] According to the non-aqueous electrolyte storage element according to an aspect of the present invention, when a compressed electrode body is provided, an increase in resistance at low temperatures associated with charge and discharge cycles can be suppressed.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

[0010] First, an overview of the non-aqueous electrolyte storage element and the power storage device disclosed in this specification will be described.

[0011] A non-aqueous electrolyte storage element according to one aspect of the present invention includes an electrode body in which a negative electrode and a positive electrode are laminated via a separator, a non-aqueous electrolyte, and a container that houses the electrode body. The container is compressed in the thickness direction of the electrode body. The separator has an inorganic particle layer, the positive electrode has a positive electrode active material layer containing a positive electrode active material, the positive electrode active material layer is laminated on the inorganic particle layer, the positive electrode active material contains a transition metal oxide, and on the lamination surface of the positive electrode active material layer and the inorganic particle layer, the ratio of the elements constituting the positive electrode active material to all elements is less than 38 atomic %.

[0012] As described above, when the positive electrode active material is opposed to the inorganic particle layer of the separator in a state where the container of the non-aqueous electrolyte storage element is compressed, the two come into close contact. When the electrode expands in this state, damage such as cracking of the positive electrode active material may occur, leading to an increase in the resistance of the non-aqueous electrolyte storage element. This is presumably because when the positive electrode active material cracks, a new surface is generated, and the amount of the film formed on the surface of the positive electrode active material increases due to the reaction between this new surface and the non-aqueous electrolyte, resulting in an increase in the resistance of the non-aqueous electrolyte storage element.

[0013] According to the non-aqueous electrolyte storage element, on the lamination surface of the inorganic particle layer and the positive electrode active material layer, the ratio of the elements constituting the positive electrode active material to all elements is less than 38 atomic %, so that the exposure of the positive electrode active material on the lamination surface of the inorganic particle layer and the positive electrode active material layer can be effectively suppressed. As a result, damage due to contact and friction between the positive electrode active material and the inorganic particles can be suppressed. Therefore, according to the non-aqueous electrolyte storage element, when an electrode body is compressed, an increase in resistance at low temperature associated with charge and discharge cycles can be suppressed.

[0014] It is preferable that the positive electrode active material layer contains carbon material particles, resin particles, or a combination thereof, and the content of the carbon material particles, resin particles, or a combination thereof in the positive electrode active material layer is 7% by mass or more and 21% by mass or less. The positive electrode active material layer contains carbon material particles, resin particles, or a combination thereof that are softer than the positive electrode active material and the inorganic particles, and the content thereof is 7% by mass or more and 21% by mass or less, so that the exposure of the positive electrode active material on the lamination surface of the positive electrode active material layer and the inorganic particle layer can be more effectively suppressed. Thereby, the suppression effect against damage due to contact and friction between the positive electrode active material and the inorganic particles can be enhanced.

[0015] The positive electrode has a coating layer that covers at least a part of the surface of the positive electrode active material layer, the coating layer is interposed between the positive electrode active material layer and the inorganic particle layer, and it is preferable that the coating layer contains carbon material particles, resin particles, or a combination thereof as a main component. In the non-aqueous electrolyte storage element, the positive electrode has a coating layer interposed between the positive electrode active material layer and the inorganic particle layer, and the coating layer contains carbon material particles, resin particles, or a combination thereof that are softer than the positive electrode active material and the inorganic particles as a main component, so that the exposure of the positive electrode active material on the lamination surface of the positive electrode active material layer and the inorganic particle layer can be more effectively suppressed. Thereby, the suppression effect against damage due to contact and friction between the positive electrode active material and the inorganic particles can be enhanced. Here, the "main component" refers to the substance with the highest content rate among the constituent substances, and preferably refers to the substance with a content rate of 30% by mass or more.

[0016] As the pressure applied to the electrode body by the above compression, it is preferably 0.4 MPa or more. When the pressure is 0.4 MPa or more, the distance between the positive and negative electrodes becomes uniform, so that it is possible to suppress the local deterioration of the active material due to the non-uniform reaction during charge and discharge.

[0017] The power storage device according to another aspect of the present invention includes the one or more non-aqueous electrolyte power storage elements and a pressing member, and the pressing member presses the electrode body of the non-aqueous electrolyte power storage element by pressing the container.

[0018] According to the power storage device, since the non-aqueous electrolyte power storage element is provided in a state where the electrode body is pressed by the pressing member, it is possible to suppress an increase in resistance at low temperature associated with the charge and discharge cycle.

[0019] The configuration of the non-aqueous electrolyte power storage element, the configuration of the power storage device, the manufacturing method of the non-aqueous electrolyte power storage element, the manufacturing method of the power storage device, and other embodiments according to an embodiment of the present invention will be described in detail. Note that the names of the respective constituent members (each constituent element) used in each embodiment may be different from the names of the respective constituent members (each constituent element) used in the background art.

[0020] <Configuration of non-aqueous electrolyte power storage element> The non-aqueous electrolyte power storage element according to an embodiment of the present invention includes an electrode body in which a negative electrode and a positive electrode are laminated via a separator, a non-aqueous electrolyte, and a container that houses the electrode body. The electrode body is usually a laminated type in which a plurality of positive electrodes and a plurality of negative electrodes are laminated via a separator, or a wound type in which the positive electrode and the negative electrode are wound in a state of being laminated via a separator. The non-aqueous electrolyte exists in a state of being impregnated in the positive electrode, the negative electrode, and the separator. As an example of the non-aqueous electrolyte power storage element, a non-aqueous electrolyte secondary battery will be described.

[0021] The shape of the non-aqueous electrolyte storage element of this embodiment is not particularly limited. For example, a rectangular battery is preferable. FIG. 1 shows a non-aqueous electrolyte storage element 1 as an example of a rectangular battery. Note that this figure is a perspective view of the inside of the container. An electrode body 2 having a positive electrode and a negative electrode wound with a separator interposed therebetween is housed in a rectangular container 3. The positive electrode is electrically connected to a positive electrode terminal 4 via a positive electrode lead 41. The negative electrode is electrically connected to a negative electrode terminal 5 via a negative electrode lead 51.

[0022] In the non-aqueous electrolyte storage element 1 of this embodiment, the container 3 is pressed in the thickness direction of the electrode body 2 in the situation where the non-aqueous electrolyte storage element 1 is used. Here, the thickness direction refers to the direction in which the positive electrode, the separator, and the negative electrode are laminated. That is, the non-aqueous electrolyte storage element 1 of this embodiment is used in a state where the electrode body 2 is pressed. For example, as will be described later, by pressing the container 3 with a pressing member 6 (see FIG. 3), the electrode body 2 can be put in a state of being pressed in the thickness direction. The electrode body 2 may be put in a state of being pressed in the thickness direction by reducing the pressure (negative pressure) by sucking the gas in the container 3 or the like. In addition to the electrode body 2, a spacer (not shown) may be inserted into the container 3 so that the electrode body 2 is in a pressed state. Generally, the thickness of the electrode body 2 increases after manufacture than immediately after manufacture by impregnating with a non-aqueous electrolyte or by charging and discharging. Therefore, when using a container 3 with high rigidity, an electrode body 2 having a thickness substantially the same as the inner dimension of the container 3 is housed in the container 3, a non-aqueous electrolyte is injected, and charging and discharging are performed, so that the electrode body 2 can be put in a state of being pressed by the container 3.

[0023] When the electrode body 2 is in a compressed state, the pressure applied to the electrode body 2 is preferably 0.4 MPa or more, more preferably 0.4 MPa or more and 4 MPa or less, and even more preferably 0.4 MPa or more and 2 MPa or less. By setting the pressure to be equal to or higher than the lower limit, the expansion of the positive electrode accompanying the charge-discharge cycle can be suppressed, and the cracking of the positive electrode active material can be more reliably suppressed. On the other hand, by setting the pressure to be equal to or lower than the upper limit, a decrease in durability caused by excessive compression of the electrode body can be suppressed. The pressure applied to the electrode body 2 means a value measured by a strain gauge type load cell. Hereinafter, each member constituting the non-aqueous electrolyte storage element will be described in detail.

[0024] [Separator] The separator has an inorganic particle layer. The separator may be composed only of the inorganic particle layer, or may have an inorganic particle layer and a base material layer. When the separator has a base material layer, the inorganic particle layer may be formed on only one surface of the base material layer, or may be formed on both surfaces. When the inorganic particle layer is formed on only one surface of the base material layer, it is arranged so that the inorganic particle layer and the positive electrode active material layer face each other. By providing the separator with an inorganic particle layer, the decomposition of the non-aqueous electrolyte during charge-discharge cycling at high temperature can be suppressed. The inorganic particle layer contains inorganic particles and, if necessary, a binder, a resin base material, and the like.

[0025] The inorganic particle layer may be provided by applying a paste containing inorganic particles and a binder to the surface of a base material layer or the like, or may be formed by dispersing inorganic particles in a resin base material made of a thermoplastic resin.

[0026] Examples of the inorganic particles contained in the inorganic particle layer include inorganic compounds. Examples of the inorganic compounds include oxides such as iron oxide, silicon oxide, aluminum oxide, titanium oxide, barium titanate, zirconium oxide, calcium oxide, strontium oxide, barium oxide, magnesium oxide, and aluminosilicate; hydroxides such as magnesium hydroxide, calcium hydroxide, and aluminum hydroxide; nitrides such as aluminum nitride and silicon nitride; carbonates such as calcium carbonate; sulfates such as barium sulfate; sparingly soluble ionic crystals such as calcium fluoride and barium fluoride; covalent crystals such as silicon and diamond; and substances derived from mineral resources such as talc, montmorillonite, boehmite, zeolite, apatite, kaolin, mullite, spinel, olivine, sericite, bentonite, and mica, or artificial products thereof. As the inorganic compound, a single substance or a composite of these substances may be used alone, or two or more kinds may be mixed and used. As the inorganic particles, inorganic compounds with a mass loss of 5% or less when heated from room temperature to 500 ° C in an air atmosphere at 1 atm are preferable, and inorganic compounds with a mass loss of 5% or less when heated from room temperature to 800 ° C are more preferable. Among these inorganic compounds, from the viewpoint of the safety of the non-aqueous electrolyte storage element, silicon oxide, aluminum oxide, or aluminosilicate is preferable.

[0027] Examples of the binder used for the inorganic particle layer include, for example, fluororesins (polytetrafluoroethylene (PTFE), polyvinylidene fluoride, etc.), elastomers such as ethylene-propylene-diene rubber (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), and fluororubber; and polysaccharide polymers.

[0028] Examples of the resin base material used for the inorganic particle layer include thermoplastic resins such as polyethylene, polypropylene, polyacrylic, and polyimide.

[0029] From the viewpoint of strength, the porosity of the inorganic particle layer of the separator is preferably 80% by volume or less, and from the viewpoint of discharge performance, it is preferably 20% by volume or more. Here, the "porosity" is a value based on volume and means the measured value by a mercury porosimeter.

[0030] Examples of the form of the base material layer of the separator include woven fabric, non-woven fabric, porous resin film, and the like. Among these, a porous resin film is preferable from the viewpoint of strength, and a non-woven fabric is preferable from the viewpoint of the liquid retention property of the non-aqueous electrolyte. As the material of the base material layer of the separator, polyolefins such as polyethylene and polypropylene are preferable from the viewpoint of the shut-down function, and polyimides, aramids, etc. are preferable from the viewpoint of oxidation decomposition resistance. As the base material layer of the separator, a material in which these resins are combined may be used.

[0031] The porosity of the base material layer of the separator is preferably 80% by volume or less from the viewpoint of strength, and preferably 20% by volume or more from the viewpoint of discharge performance.

[0032] As the base material layer of the separator, a polymer gel composed of a polymer and a non-aqueous electrolyte may be used. Examples of the polymer include polyacrylonitrile, polyethylene oxide, polypropylene oxide, polymethyl methacrylate, polyvinyl acetate, polyvinyl pyrrolidone, polyvinylidene fluoride, and the like. Using a polymer gel has the effect of suppressing liquid leakage. As the separator, a porous resin film or non-woven fabric as described above and a polymer gel may be used in combination.

[0033] [Positive Electrode] The positive electrode has a positive electrode substrate and a positive electrode active material layer disposed directly or via an intermediate layer on the positive electrode substrate. The positive electrode further has a coating layer that covers at least a part of the surface of the positive electrode active material layer, and in the thickness direction of the electrode body, one surface of the positive electrode active material layer may be in contact with the positive electrode substrate and the other surface may be in contact with the coating layer.

[0034] The positive electrode substrate has conductivity. Whether it has "conductivity" is determined by the volume resistivity measured in accordance with JIS-H-0505 (1975) being 10 7It is determined with Ω·cm as the threshold value. As the material of the positive electrode substrate, metals such as aluminum, titanium, tantalum, and stainless steel, or alloys thereof are used. Among these, aluminum or an aluminum alloy is preferable from the viewpoints of corrosion resistance, high conductivity, and cost. Examples of the positive electrode substrate include a foil, a vapor deposition film, a mesh, and a porous material, and a foil is preferable from the viewpoint of cost. Therefore, an aluminum foil or an aluminum alloy foil is preferable as the positive electrode substrate. Examples of the aluminum or aluminum alloy include A1085, A3003, A1N30, etc. defined in JIS-H-4000 (2014) or JIS-H4160 (2006).

[0035] The average thickness of the positive electrode substrate is preferably 3 μm or more and 50 μm or less, more preferably 5 μm or more and 40 μm or less, still more preferably 8 μm or more and 30 μm or less, and particularly preferably 10 μm or more and 25 μm or less. By setting the average thickness of the positive electrode substrate within the above range, the strength of the positive electrode substrate can be increased while increasing the energy density per volume of the secondary battery.

[0036] The intermediate layer is a layer disposed between the positive electrode substrate and the positive electrode active material layer. The intermediate layer contains a conductive agent such as carbon particles to reduce the contact resistance between the positive electrode substrate and the positive electrode active material layer. The configuration of the intermediate layer is not particularly limited. For example, it contains a binder and a conductive agent.

[0037] The positive electrode active material layer contains a positive electrode active material. The positive electrode active material layer is laminated so as to face the inorganic particle layer of the separator.

[0038] On the lamination surface of the positive electrode active material layer with the inorganic particle layer, the upper limit of the ratio of the elements constituting the positive electrode active material to all elements is 38 atomic %, preferably 35 atomic %, and more preferably 30 atomic %. Thereby, the exposure of the positive electrode active material on the lamination surface of the positive electrode active material layer with the inorganic particle layer can be effectively suppressed. As a result, damage due to contact and friction between the positive electrode active material and the inorganic particles can be suppressed. Therefore, when a compressed electrode body is provided, an increase in resistance at low temperature accompanying charge and discharge cycles can be suppressed.

[0039] The ratio of the elements constituting the positive electrode active material with respect to all the above elements is calculated by the following method. Using a scanning electron microscope - energy dispersive X - ray analyzer (SEM - EDS), the elemental ratios of the elements (excluding lithium and oxygen) constituting the positive electrode active material, carbon, and fluorine are measured by energy - dispersive X - ray spectroscopy (EDX). The ratio of the sum of the elemental ratios of the elements (excluding lithium and oxygen) constituting the positive electrode active material to the sum of the elemental ratios of the elements (excluding lithium and oxygen), carbon, and fluorine is defined as the ratio of the elements constituting the positive electrode active material with respect to all the above elements. The analysis conditions are as follows. Magnification for photography: 1000 times EDS acceleration voltage: 15 kV Elements for mapping: C, F, elements (excluding lithium and oxygen) constituting the positive electrode active material Resolution: 128 pixels Pixel time: 10 ms Number of integrations: 1 time Note that the elements constituting the positive electrode active material are elements contained at 1 atomic % or more in the positive electrode active material, excluding lithium, oxygen, carbon, and fluorine. All the above elements do not include elements other than the elements (excluding lithium and oxygen) constituting the positive electrode active material, carbon, and fluorine.

[0040] Therefore, for example, when the positive electrode active material is represented by the composition formula of Li[Li x Ni γ Mn β Co (1-x-γ-β) O2, the ratio (atomic %) of the elements constituting the positive electrode active material can be obtained by the following formula. Ratio of elements = ((R Ni +R Mn +R Co ) / (R Ni +R Mn +R Co +R C +R F ))*100

[0041] In the above formula, R Ni 、R Mn, R Co , R C and R F are the elemental ratios of nickel, manganese, cobalt, carbon, and fluorine obtained from the elemental mapping, respectively.

[0042] The above positive electrode active material contains a transition metal oxide. As the transition metal oxide, a transition metal composite oxide is preferable, and examples thereof include a lithium transition metal composite oxide having an α-NaFeO2 type crystal structure, a lithium transition metal composite oxide having a spinel type crystal structure, and the like. As the lithium transition metal composite oxide having an α-NaFeO2 type crystal structure, for example, Li[Li x Ni (1-x) O2(0 ≦ x < 0.5), Li[Li x Ni γ Co (1-x-γ) O2(0 ≦ x < 0.5, 0 < γ < 1), Li[Li x Co (1-x) O2(0 ≦ x < 0.5), Li[Li x Ni γ Mn (1-x-γ) O2(0 ≦ x < 0.5, 0 < γ < 1), Li[Li x Ni γ Mn β Co (1-x-γ-β) O2(0 ≦ x < 0.5, 0 < γ, 0 < β, 0.5 < γ + β < 1), Li[Li x Ni γ Co β Al (1-x-γ-β) O2(0 ≦ x < 0.5, 0 < γ, 0 < β, 0.5 < γ + β < 1), etc. are included. As the lithium transition metal composite oxide having a spinel type crystal structure, Li x Mn2O4, Li x Ni γ Mn (2-γ) O4, etc. are included. Atoms in these materials may be partially substituted with atoms composed of other elements. In the positive electrode active material layer, one of these materials may be used alone, or two or more thereof may be mixed and used.

[0043] The positive electrode active material is usually particles (powder). The average particle size of the positive electrode active material is preferably, for example, 0.1 μm or more and 20 μm or less. By setting the average particle size of the positive electrode active material to be equal to or greater than the above lower limit, the production or handling of the positive electrode active material becomes easy. By setting the average particle size of the positive electrode active material to be equal to or less than the above upper limit, the electron conductivity of the positive electrode active material layer is improved. The "average particle size" means a value at which the volume-based cumulative distribution calculated in accordance with JIS-Z-8819-2 (2001) based on the particle size distribution measured by the laser diffraction / scattering method for a diluted solution in which particles are diluted with a solvent conforms to JIS-Z-8825 (2013).

[0044] In order to obtain powder with a predetermined particle size, a crusher, a classifier, or the like is used. Examples of the pulverization method include methods using a mortar, a ball mill, a sand mill, a vibration ball mill, a planetary ball mill, a jet mill, a counter jet mill, a swirling air flow type jet mill, a sieve, or the like. During pulverization, wet pulverization in which water or an organic solvent such as hexane coexists can also be used. As the classification method, a sieve, an air classifier, or the like is used as needed for both dry and wet processes.

[0045] The content of the positive electrode active material in the positive electrode active material layer is preferably 50% by mass or more and 93% by mass or less, more preferably 70% by mass or more and 92% by mass or less, and even more preferably 80% by mass or more and 91% by mass or less. By setting the content of the positive electrode active material within the above range, both high energy density and manufacturability of the positive electrode active material layer can be achieved.

[0046] The positive electrode active material layer preferably contains carbon material particles, resin particles, or a combination thereof. By containing carbon material particles, resin particles, or a combination thereof, which are softer than the positive electrode active material and inorganic particles, as a material for suppressing the exposure of the positive electrode active material to the surface of the positive electrode active material layer, the suppression effect against damage caused by contact and friction between the positive electrode active material and the inorganic particles can be enhanced. When the positive electrode active material layer contains carbon material particles, the carbon material particles also function as a conductive agent. When the resin particles exemplified below are contained, the resin particles function as a binder.

[0047] Examples of the carbon material include graphitized carbon, non-graphitized carbon, graphene-based carbon, etc. Graphitized carbon includes graphite. Non-graphitized carbon includes carbon nanofibers, pitch-based carbon fibers, carbon black, etc. Carbon black includes furnace black, acetylene black, ketjen black, etc. Graphene-based carbon includes graphene, carbon nanotubes (CNT), fullerenes, etc. The shape of the carbon material particles includes powder, fiber, etc. As the carbon material, one of these materials may be used alone, or two or more of them may be mixed and used. Also, these materials may be used in a composite form. For example, a material in which carbon black and CNT are composite may be used. Among these, carbon black is preferable from the viewpoints of electron conductivity and manufacturability, and acetylene black is particularly preferable. Examples of the resin include fluororesins such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride; thermoplastic resins such as polyolefins such as polyethylene and polypropylene, polyacryl, and polyimide; elastomers such as ethylene-propylene-diene rubber (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), and fluororubber; polysaccharide polymers, etc.

[0048] It is preferable that the content of the carbon material particles, resin particles, or a combination thereof in the positive electrode active material layer is 7% by mass or more and 21% by mass or less. As the lower limit of the content, 7% by mass is preferable, and 9% by mass is more preferable. On the other hand, as the upper limit of the content, 21% by mass is preferable, and 17% by mass is more preferable. By having these contents within the above range, while maintaining the energy density of the positive electrode active material layer, the exposure of the positive electrode active material on the lamination surface with the inorganic particle layer of the positive electrode active material layer can be more effectively suppressed, and an increase in resistance at low temperatures accompanying charge and discharge cycles can be suppressed.

[0049] The positive electrode active material layer may contain optional components such as a conductive agent, a binder, a thickener, and a filler, as required.

[0050] The conductive agent is not particularly limited as long as it is a material having conductivity. Examples of such a conductive agent include carbonaceous materials, metals, conductive ceramics, and the like. As the carbonaceous material, it can be selected from the configurations exemplified as the above carbon materials. Examples of the shape of the conductive agent include powder form, fibrous form, and the like. As the conductive agent, one of these materials may be used alone, or two or more of them may be mixed and used. Further, these materials may be used in a composite form. For example, a material obtained by compositing carbon black and CNT may be used. Among these, carbon black is preferable from the viewpoints of electron conductivity and manufacturability, and acetylene black is particularly preferable.

[0051] The content of the conductive agent in the positive electrode active material layer is preferably 5% by mass or more and 15% by mass or less, and more preferably 7% by mass or more and 12% by mass or less. When resin particles are used as a material for suppressing the exposure of the positive electrode active material to the surface of the positive electrode active material layer, the content of the conductive agent is preferably 2% by mass or more and 15% by mass or less. By setting the content of the conductive agent within the above range, the energy density of the secondary battery can be increased.

[0052] The binder is not particularly limited, and for example, it can be selected from the materials exemplified as the above resins.

[0053] The content of the binder in the positive electrode active material layer is preferably 1% by mass or more and 10% by mass or less, and more preferably 3% by mass or more and 9% by mass or less. By setting the content of the binder within the above range, the positive electrode active material can be stably held.

[0054] Examples of the thickener include polysaccharide polymers such as carboxymethyl cellulose (CMC) and methyl cellulose. When the thickener has a functional group that reacts with lithium or the like, this functional group may be deactivated in advance by methylation or the like.

[0055] The filler is not particularly limited. Examples of the filler include polyolefins such as polypropylene and polyethylene, inorganic oxides such as silicon dioxide, alumina, titanium dioxide, calcium oxide, strontium oxide, barium oxide, magnesium oxide, and aluminosilicate, hydroxides such as magnesium hydroxide, calcium hydroxide, and aluminum hydroxide, carbonates such as calcium carbonate, sparingly soluble ionic crystals such as calcium fluoride, barium fluoride, and barium sulfate, nitrides such as aluminum nitride and silicon nitride, and mineral resource-derived substances such as talc, montmorillonite, boehmite, zeolite, apatite, kaolin, mullite, spinel, olivine, sericite, bentonite, and mica, or artificial products thereof.

[0056] The positive electrode active material layer may contain typical non-metal elements such as B, N, P, F, Cl, Br, and I, typical metal elements such as Li, Na, Mg, Al, K, Ca, Zn, Ga, Ge, Sn, Sr, and Ba, and transition metal elements such as Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Mo, Zr, and Nb as components other than the positive electrode active material, conductive agent, binder, thickener, and filler.

[0057] [Negative electrode] The negative electrode has a negative electrode substrate and a negative electrode active material layer disposed directly or via an intermediate layer on the negative electrode substrate. The configuration of the intermediate layer is not particularly limited, and can be selected, for example, from the configurations exemplified for the positive electrode above.

[0058] The negative electrode substrate has conductivity. As the material of the negative electrode substrate, metals such as copper, nickel, stainless steel, nickel-plated steel, and aluminum, or alloys thereof, carbonaceous materials, etc. are used. Among these, copper or a copper alloy is preferable. Examples of the negative electrode substrate include foil, vapor deposition film, mesh, porous material, etc., and foil is preferable from the viewpoint of cost. Therefore, a copper foil or a copper alloy foil is preferable as the negative electrode substrate. Examples of the copper foil include rolled copper foil, electrolytic copper foil, etc.

[0059] The average thickness of the negative electrode substrate is preferably 2 μm or more and 35 μm or less, more preferably 3 μm or more and 30 μm or less, still more preferably 4 μm or more and 25 μm or less, and particularly preferably 5 μm or more and 20 μm or less. By setting the average thickness of the negative electrode substrate within the above range, it is possible to increase the strength of the negative electrode substrate and at the same time increase the energy density per unit volume of the secondary battery.

[0060] The negative electrode active material layer contains a negative electrode active material. The negative electrode active material layer may contain optional components such as a conductive agent, a binder, a thickener, and a filler as required. The optional components such as the conductive agent, the binder, the thickener, and the filler can be selected from the materials exemplified in the above positive electrode.

[0061] The negative electrode active material layer may contain typical non-metal elements such as B, N, P, F, Cl, Br, and I, typical metal elements such as Li, Na, Mg, Al, K, Ca, Zn, Ga, Ge, Sn, Sr, and Ba, and transition metal elements such as Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Mo, Zr, Ta, Hf, and Nb as components other than the negative electrode active material, the conductive agent, the binder, and the filler.

[0062] The negative electrode active material can be appropriately selected from known negative electrode active materials. As the negative electrode active material for a lithium-ion secondary battery, a material that can occlude and release lithium ions is usually used. Examples of the negative electrode active material include metallic Li; metals or semi-metals such as Si and Sn; metal oxides or semi-metal oxides such as SiO, TiO, and SnO; 12 , LiTiO 2、 titanium-containing oxides such as TiNb2O7; polyphosphoric acid compounds; silicon carbide; carbon materials such as graphite (graphite), non-graphitic carbon (easily graphitizable carbon or hardly graphitizable carbon), etc. Among these materials, graphite and non-graphitic carbon are preferred. In the negative electrode active material layer, one of these materials may be used alone, or two or more of them may be used in combination.

[0063] "Graphite" refers to the average lattice plane spacing (d 002refers to a carbon material having an average lattice plane spacing (d

[0064] of the (002) plane determined by X-ray diffraction method before charge-discharge or in a discharged state) of 0.33 nm or more and less than 0.34 nm. Examples of graphite include natural graphite and artificial graphite. From the viewpoint of obtaining a material with stable physical properties, artificial graphite is preferred. 002 "Non-graphitic carbon" refers to a carbon material having an average lattice plane spacing (d

[0065] ) of 0.34 nm or more and 0.42 nm or less determined by X-ray diffraction method before charge-discharge or in a discharged state. Examples of non-graphitic carbon include non-graphitizable carbon and graphitizable carbon. Examples of non-graphitic carbon include, for example, resin-derived materials, petroleum pitch or petroleum pitch-derived materials, petroleum coke or petroleum coke-derived materials, plant-derived materials, alcohol-derived materials, and the like.

[0066] Here, the "discharged state" means a state in which lithium ions that can be occluded and released during charge-discharge are sufficiently released from the carbon material that is the negative electrode active material. For example, in a single electrode battery using a negative electrode containing a carbon material as the working electrode and metallic Li as the counter electrode, it is a state where the open circuit voltage is 0.7 V or more. 002 "Non-graphitizable carbon" refers to a carbon material having a d

[0067] of 0.36 nm or more and 0.42 nm or less. 002 "Graphitizable carbon" refers to a carbon material having a d

[0068] The negative electrode active material is usually in the form of particles (powder). The average particle size of the negative electrode active material can be, for example, 1 nm or more and 100 μm or less. When the negative electrode active material is a carbon material, a titanium-containing oxide, or a polyphosphoric acid compound, its average particle size may be 1 μm or more and 100 μm or less. When the negative electrode active material is Si, Sn, a silicon oxide, or a tin oxide, etc., its average particle size may be 1 nm or more and 1 μm or less. By setting the average particle size of the negative electrode active material to be equal to or greater than the above lower limit, the production or handling of the negative electrode active material becomes easier. By setting the average particle size of the negative electrode active material to be equal to or less than the above upper limit, the electron conductivity of the active material layer is improved. To obtain a powder with a predetermined particle size, a pulverizer, a classifier, etc. are used. The pulverization method and the classification method can be selected, for example, from the methods exemplified for the positive electrode above. When the negative electrode active material is a metal such as metallic Li, the negative electrode active material may be in the form of a foil.

[0069] The content of the negative electrode active material in the negative electrode active material layer is preferably 60% by mass or more and 99% by mass or less, and more preferably 90% by mass or more and 98% by mass or less. By setting the content of the negative electrode active material within the above range, both high energy density and manufacturability of the negative electrode active material layer can be achieved.

[0070] [Non-aqueous electrolyte] The non-aqueous electrolyte can be appropriately selected from known non-aqueous electrolytes. A non-aqueous electrolyte solution may be used as the non-aqueous electrolyte. The non-aqueous electrolyte solution contains a non-aqueous solvent and an electrolyte salt dissolved in this non-aqueous solvent.

[0071] The non-aqueous solvent can be appropriately selected from known non-aqueous solvents. Examples of the non-aqueous solvent include cyclic carbonates, chain carbonates, carboxylic acid esters, phosphoric acid esters, sulfonic acid esters, ethers, amides, nitriles, etc. As the non-aqueous solvent, those in which some of the hydrogen atoms contained in these compounds are substituted with halogens may be used.

[0072] Examples of the cyclic carbonate include ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), vinylene carbonate (VC), vinyl ethylene carbonate (VEC), chloroethylene carbonate, fluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC), styrene carbonate, 1-phenylvinylene carbonate, 1,2-diphenylvinylene carbonate, and the like. Among these, EC is preferred.

[0073] Examples of the chain carbonate include diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diphenyl carbonate, trifluoroethyl methyl carbonate, bis(trifluoroethyl) carbonate, and the like. Among these, EMC is preferred.

[0074] As the non-aqueous solvent, it is preferable to use a cyclic carbonate or a chain carbonate, and it is more preferable to use them in combination. By using a cyclic carbonate, the dissociation of the electrolyte salt can be promoted and the ionic conductivity of the non-aqueous electrolyte can be improved. By using a chain carbonate, the viscosity of the non-aqueous electrolyte can be kept low. When using a cyclic carbonate and a chain carbonate in combination, the volume ratio of the cyclic carbonate to the chain carbonate (cyclic carbonate:chain carbonate) is preferably in the range of, for example, 5:95 to 50:50.

[0075] The electrolyte salt can be appropriately selected from known electrolyte salts. Examples of the electrolyte salt include lithium salts, sodium salts, potassium salts, magnesium salts, onium salts, and the like. Among these, lithium salts are preferred.

[0076] Examples of the lithium salt include inorganic lithium salts such as LiPF6, LiPO2F2, LiBF4, LiClO4, and LiN(SO2F)2; lithium salts having an oxalate group such as lithium bis(oxalate) borate (LiBOB), lithium difluorooxalate borate (LiFOB), and lithium bis(oxalate) difluorophosphate (LiFOP); and lithium salts having a halogenated hydrocarbon group such as LiSO3CF3, LiN(SO2CF3)2, LiN(SO2C2F5)2, LiN(SO2CF3)(SO2C4F9), LiC(SO2CF3)3, and LiC(SO2C2F5)3. Among these, inorganic lithium salts are preferred, and LiPF6 is more preferred.

[0077] The content of the electrolyte salt in the non-aqueous electrolyte is preferably 0.1 mol / dm 3 or more and 2.5 mol / dm 3 or less at 20 °C and 1 atm, more preferably 0.3 mol / dm 3 or more and 2.0 mol / dm 3 or less, even more preferably 0.5 mol / dm 3 or more and 1.7 mol / dm 3 or less, and particularly preferably 0.7 mol / dm 3 or more and 1.5 mol / dm 3 or less. By setting the content of the electrolyte salt within the above range, the ionic conductivity of the non-aqueous electrolyte can be increased.

[0078] In addition to non-aqueous solvents and electrolyte salts, the non-aqueous electrolyte may contain additives. Examples of the additives include halogenated carbonates such as fluoroethylene carbonate (FEC) and difluoroethylene carbonate (DFEC); salts having an oxalic acid group such as lithium bis(oxalate) borate (LiBOB), lithium difluorooxalate borate (LiFOB), and lithium bis(oxalate) difluorophosphate (LiFOP); imide salts such as lithium bis(fluorosulfonyl) imide (LiFSI); aromatic compounds such as biphenyl, alkyl biphenyl, terphenyl, partially hydrogenated terphenyl, cyclohexylbenzene, t-butylbenzene, t-amylbenzene, diphenyl ether, and dibenzofuran; partial halides of the aromatic compounds such as 2-fluorobiphenyl, o-cyclohexylfluorobenzene, and p-cyclohexylfluorobenzene; halogenated anisole compounds such as 2,4-difluoroanisole, 2,5-difluoroanisole, 2,6-difluoroanisole, and 3,5-difluoroanisole; vinylene carbonate, methyl vinylene carbonate, ethyl vinylene carbonate, succinic anhydride, glutaric anhydride, maleic anhydride, citraconic anhydride, glutaconic anhydride, itaconic anhydride, cyclohexanedicarboxylic anhydride; ethylene sulfite, propylene sulfite, dimethyl sulfite, propane sultone, propene sultone, butane sultone, methyl methanesulfonate, busulfan, methyl toluenesulfonate, dimethyl sulfate, ethylene sulfate, sulfolane, dimethyl sulfone, diethyl sulfone, dimethyl sulfoxide, diethyl sulfoxide, tetramethylene sulfoxide, diphenyl sulfide, 4,4'-bis(2,2-dioxo-1,3,2-dioxathiolane), 4-methylsulfonyloxymethyl-2,2-dioxo-1,3,2-dioxathiolane, thioanisole, diphenyl disulfide, dipyridinium disulfide, 1,3-propene sultone, 1,3-propane sultone, 1,4-butane sultone, 1,4-butene sultone, perfluorooctane, tris(trimethylsilyl) borate, tris(trimethylsilyl) phosphate, tetrakis(trimethylsilyl) titanate, lithium monofluorophosphate, lithium difluorophosphate, and the like.These additives may be used individually or in combination of two or more.

[0079] The content of the additive contained in the non-aqueous electrolyte is preferably 0.01% by mass or more and 10% by mass or less, more preferably 0.1% by mass or more and 7% by mass or less, still more preferably 0.2% by mass or more and 5% by mass or less, and particularly preferably 0.3% by mass or more and 3% by mass or less with respect to the mass of the entire non-aqueous electrolyte. By setting the content of the additive within the above range, it is possible to improve the capacity retention performance or charge-discharge cycle performance after high-temperature storage, or to further improve the safety. As the non-aqueous electrolyte, a solid electrolyte may be used, or a non-aqueous electrolyte and a solid electrolyte may be used in combination.

[0080] As the solid electrolyte, it can be selected from any material having ion conductivity such as lithium, sodium, calcium, etc. and being solid at room temperature (for example, from 15 °C to 25 °C). Examples of the solid electrolyte include sulfide solid electrolytes, oxide solid electrolytes, oxynitride solid electrolytes, polymer solid electrolytes, and the like.

[0081] Examples of the sulfide solid electrolyte include Li2S-P2S5, LiI-Li2S-P2S5, Li 10 Ge-P2S 12 and the like.

[0082] <Power storage device> The non-aqueous electrolyte power storage element of this embodiment can be mounted as a power storage device configured by aggregating a plurality of non-aqueous electrolyte power storage elements 1 in a power source for automobiles such as electric vehicles (EVs), hybrid vehicles (HEVs), plug-in hybrid vehicles (PHEVs), a power source for electronic devices such as personal computers and communication terminals, or a power source for power storage. In this case, the technology of the present invention may be applied to at least one non-aqueous electrolyte power storage element included in the power storage device.

[0083] The energy storage device of this embodiment includes the non-aqueous electrolyte energy storage element and the pressing member of the above-described this embodiment, and the pressing member presses the electrode body by pressing the container. FIG. 2 shows an example of a battery pack 30 in which energy storage devices 20, each of which is a collection of two or more non-aqueous electrolyte energy storage elements 1 electrically connected, are further combined. The battery pack 30 may include a bus bar (not shown) for electrically connecting two or more non-aqueous electrolyte energy storage elements 1, a bus bar (not shown) for electrically connecting two or more energy storage devices 20, and the like. The energy storage device 20 or the battery pack 30 may include a state monitoring device (not shown) for monitoring the state of one or more non-aqueous electrolyte energy storage elements.

[0084] FIG. 3 shows an aspect in which the energy storage device 20 has a plurality of non-aqueous electrolyte energy storage elements 1 that are rectangular batteries as shown in FIG. 1. As shown in FIG. 3, the energy storage device 20 includes a plurality of non-aqueous electrolyte energy storage elements 1 whose side surfaces face each other and are arranged side by side with a space therebetween, and a pressing member 6.

[0085] (Pressing member) As shown in FIG. 3, the pressing member 6 includes two (i.e., a pair of) pressing portions 61 that respectively press the outer surfaces of the two non-aqueous electrolyte energy storage elements 1 arranged on the outermost sides in the arrangement direction of the plurality of non-aqueous electrolyte energy storage elements 1, one or a plurality of spacer portions 62 arranged between the plurality of non-aqueous electrolyte energy storage elements 1, two support portions 63 arranged along the arrangement direction between the two pressing portions 61 and supporting the two pressing portions 61, and a plurality of pressing force adjusting portions 64 configured to connect the two pressing portions 61 and the one or more support portions 63 and to be able to adjust the pressing force of the two pressing portions 61 on the plurality of non-aqueous electrolyte energy storage elements 1. [Pressing portion]

[0086] The two pressing parts 61 are in contact with the outer surfaces of the two outermost non-aqueous electrolyte storage elements 1 and press these non-aqueous electrolyte storage elements 1. The pressing part 61 is not particularly limited and is appropriately set so as to be able to contact the side surface of the non-aqueous electrolyte storage element and press the non-aqueous electrolyte storage element 1. Examples of the pressing part 61 include a metal plate, a resin plate, and the like. As shown in FIG. 3, the shape of the pressing part 61 can be, for example, a rectangular shape. In the embodiment shown in FIG. 3, the pressing part 61 has one or a plurality (4 in FIG. 3) of screw holes (not shown) into which the pressing force adjusting part 64 is screwed. In FIG. 3, in addition to the pressing force adjusting part 64 being screwed into one (front side) of the two pressing parts 61, the pressing force adjusting part 64 is also screwed into the other (rear side) pressing part 61 in the same manner.

[0087] [Support part] The two support parts 63 are connected to the two pressing parts 61 and support these pressing parts 61. The support part 63 is not particularly limited and can be appropriately set so as to be able to support the pressing part 61. Examples of the support part 63 include a metal plate, a resin plate, and the like. As shown in FIG. 3, the shape of the support part 63 can be, for example, a rectangular shape. The support part 63 can be arranged so as to be in contact with a side surface perpendicular to the arrangement direction in a plurality of non-aqueous electrolyte storage elements 1. The support part 63 is connected to the pressing part 61 by the pressing force adjusting part 64. The length of the support part 63 in the above arrangement direction can be appropriately set to a length such that the pressing force from the pressing part 62 can be adjusted to a desired value.

[0088] The number of the support parts 63 may be 1 or more and is not particularly limited. As shown in FIG. 3, for example, the number of the support parts 63 is 2, and these two support parts 63 can be respectively connected to the two pressing parts 61. In the embodiment shown in FIG. 3, the support part 63 has a plurality (2 each on each end surface in FIG. 3) of screw holes (not shown) into which the pressing force adjusting part 64 is screwed on both end surfaces in the above arrangement direction.

[0089] [Spacer part] One or a plurality of spacer portions 62 are arranged between the plurality of non-aqueous electrolyte storage elements 1 so as to be in contact with these plurality of non-aqueous electrolyte storage elements 1, and transmit the pressing force from the pressing portion 61 to the adjacent non-aqueous electrolyte storage elements 1. The spacer portion 62 is not particularly limited and is appropriately set so that the pressing force can be transmitted to the adjacent non-aqueous electrolyte storage elements 1. Examples of the spacer portion 62 include a metal plate, a resin plate, and the like. As shown in FIG. 3, the shape of the spacer portion 62 can be, for example, rectangular. As shown in FIG. 3, for example, the outer peripheral edge of the side surface of the spacer portion 62 that contacts the non-aqueous electrolyte storage element 1 can be formed smaller than the outer peripheral edge of the side surface of the non-aqueous electrolyte storage element 1. By forming it in this way, the pressing force from the pressing portion 61 can be efficiently transmitted by the non-aqueous electrolyte storage element 1. The number of the spacer portions 62 may be one or more and is not particularly limited. For example, the number of the spacer portions 62 can be appropriately set according to the number of the non-aqueous electrolyte storage elements 1 included in the power storage device 20.

[0090] [Pressing Force Adjusting Portion] A plurality of pressing force adjusting portions 64 connect the two pressing portions 61 and adjust the pressing force of the plurality of non-aqueous electrolyte storage elements 1 by these pressing portions 61. In the embodiment shown in FIG. 3, the pressing force adjusting portion 64 connects the two pressing portions 61 via the support portion 63. The pressing force adjusting portion 64 is not particularly limited and can be appropriately set so that the two pressing portions 61 can be connected in this way and the pressing force by these pressing portions 61 can be adjusted.

[0091] As shown in FIG. 3, for example, the compression force adjustment part 64 may be formed by a screw member screwed into the compression part 61 and the support part 63. As described above, in FIG. 3, in addition to the compression force adjustment part 64 being screwed into one (front side) compression part 61 of the two compression parts 61, the compression force adjustment part 64 is similarly screwed into the other (rear side) compression part 61. In this aspect, by adjusting the screwing amount of the compression force adjustment part 64 with respect to the compression part 61 and the support part 63, the compression force applied by the compression part 61 to the non-aqueous electrolyte storage element 1 can be adjusted. For example, by adjusting the screwing amount of the compression force adjustment part 64 in the direction in which the distance between the two compression parts 61 becomes smaller, the compression force applied by these compression parts 61 to the non-aqueous electrolyte storage element 1 can be increased. On the other hand, by adjusting the screwing amount of the compression force adjustment part 64 in the direction in which the distance between the two compression parts 61 becomes larger, the compression force applied by these compression parts 61 to the non-aqueous electrolyte storage element 1 can be decreased. The number of the compression force adjustment parts 64 may be one or more and is not particularly limited. As shown in FIG. 2, for example, the number of the compression force adjustment parts 64 can be set to 8 (4 for each compression part 61).

[0092] In this way, when the compression force adjustment part 64 is formed by a screw member, the compression force can be adjusted only by adjusting the screwing amount, so that the adjustment of the compression force becomes easy. The compression force can be set so that the pressure applied to the electrode body 2 is 0.4 MPa or more as described above.

[0093] The battery pack 30 can include one or more power storage devices 20. When the battery pack 30 includes one power storage device 20, this power storage device 20 can correspond to the battery pack 30. When the battery pack 30 includes a plurality of power storage devices 20 as shown in FIG. 2, these plurality of power storage devices 20 can be connected by a connecting member (not shown).

[0094] <Manufacturing Method of Non-aqueous Electrolyte Storage Element> The manufacturing method of the non-aqueous electrolyte storage element of the present embodiment is a method for manufacturing the non-aqueous electrolyte storage element of the present embodiment described above, and includes preparing an electrode body, preparing a non-aqueous electrolyte, accommodating the electrode body and the non-aqueous electrolyte in a container, and pressing the electrode body. That is, the manufacturing method includes preparing an electrode body, preparing a non-aqueous electrolyte, accommodating the electrode body and the non-aqueous electrolyte in a container, and pressing the container in a state where the electrode body and the non-aqueous electrolyte are accommodated in the container.

[0095] Preparing the electrode body includes preparing a positive electrode including a positive electrode active material layer and a negative electrode, and forming the electrode body by winding or laminating the positive electrode and the negative electrode with a separator having an inorganic particle layer interposed therebetween. When using a separator having an inorganic particle layer only on one surface of the base material layer, the positive electrode, the separator, and the negative electrode are arranged so that the inorganic particle layer faces the positive electrode active material layer.

[0096] The positive electrode can be manufactured, for example, by applying a positive electrode mixture paste directly to a positive electrode substrate or through an intermediate layer and drying it. The positive electrode mixture paste contains each component constituting the positive electrode active material layer, such as positive electrode active material particles and optional components such as a conductive agent and a binder. The positive electrode mixture paste preferably contains carbon material particles, resin particles, or a combination thereof. The positive electrode mixture paste usually further contains a dispersion medium. Examples of the dispersion medium include N-methylpyrrolidone (NMP), toluene, and the like.

[0097] When the above-mentioned positive electrode active material layer further contains carbon material particles, resin particles, or a combination thereof in addition to the positive electrode active material, from the viewpoint of further suppressing the exposure of the positive electrode active material, it is preferable to apply a low-viscosity positive electrode binder paste so that sedimentation of the positive electrode active material in the positive electrode binder paste is likely to occur. As means for lowering the viscosity of the positive electrode binder paste, for example, lowering the solid content concentration of the positive electrode binder paste or adding a dispersant to the positive electrode binder paste can be mentioned. Further, in order to cause the binder to flow, it is also preferable to quickly dry the positive electrode binder paste after application. As means for quickly drying the positive electrode binder paste after application, for example, raising the temperature of the drying furnace or increasing the air volume in the drying furnace can be mentioned.

[0098] The method of accommodating the non-aqueous electrolyte in the container can be appropriately selected from known methods. For example, when using a non-aqueous electrolyte solution as the non-aqueous electrolyte, after injecting the non-aqueous electrolyte solution from the injection port formed in the container, the injection port may be sealed.

[0099] As for compressing the electrode body, for example, as described above, it is possible to adopt compressing the container with a pressing member. In this case, as described above, the container can be compressed with a pressing member so that the pressure applied to the electrode body is 0.4 MPa or more. Alternatively, as described above, by using a container with high rigidity and an electrode body whose thickness becomes larger than the inner dimension of the container after charge and discharge, and performing injection of the non-aqueous electrolyte and charge and discharge, the electrode body can also be compressed.

[0100] <Method for manufacturing a power storage device> The manufacturing method of the power storage device according to the present embodiment includes arranging the above-described one or more non-aqueous electrolyte power storage elements and making the arranged non-aqueous electrolyte power storage elements be in a state of being pressed by a pressing member. For example, when manufacturing a power storage device in the form shown in FIGS. 2 and 3, the manufacturing method of the power storage device includes arranging a plurality of non-aqueous electrolyte power storage elements and a spacer portion 62 arranged between the plurality of non-aqueous electrolyte power storage elements so as to be in contact with the plurality of non-aqueous electrolyte power storage elements, contacting two pressing portions 61 with the outer surfaces of two non-aqueous electrolyte power storage elements located on both outer sides in the arrangement direction of the plurality of non-aqueous electrolyte power storage elements, arranging two support portions 63 between the two pressing portions 61, and connecting each pressing portion 61 and each support portion 63 with a plurality of pressing force adjusting portions 64. The manufacturing method may include manufacturing the power storage device 20 by making the plurality of non-aqueous electrolyte power storage elements be in a state of being pressed by the pressing member 6 and connecting the manufactured plurality of power storage devices 20. <Other Embodiments>

[0101] Note that the non-aqueous electrolyte power storage element of the present invention is not limited to the above embodiment, and various modifications may be made without departing from the gist of the present invention. For example, the configuration of another embodiment can be added to the configuration of a certain embodiment, and a part of the configuration of a certain embodiment can be replaced with the configuration of another embodiment or well-known technology. Further, a part of the configuration of a certain embodiment can be deleted. Also, well-known technology can be added to the configuration of a certain embodiment.

[0102] In the above-described embodiment, the positive electrode active material layer contains carbon material particles, resin particles, or a combination thereof, thereby suppressing the exposure of the positive electrode active material on the laminated surface of the positive electrode active material layer and the inorganic particle layer. However, the positive electrode may have a coating layer that covers at least a part of the surface of the positive electrode active material layer, and the coating layer may be interposed between the positive electrode active material layer and the inorganic particle layer. Further, as the coating layer, it is preferable to mainly contain carbon material particles, resin particles, or a combination thereof. In the non-aqueous electrolyte storage element, the positive electrode has a coating layer interposed between the positive electrode active material layer and the inorganic particle layer, and the coating layer mainly contains carbon material particles, resin particles, or a combination thereof that are softer than the positive electrode active material and the inorganic particles. Thus, the exposure of the positive electrode active material on the laminated surface of the positive electrode active material layer and the inorganic particle layer can be more effectively suppressed. In addition, the suppression effect against damage due to contact and friction between the positive electrode active material and the inorganic particles can be enhanced.

[0103] The coating layer only needs to cover at least a part of the surface of the positive electrode active material layer, but preferably covers 62% or more of the surface of the positive electrode active material layer, and more preferably covers 70% or more. The coating layer preferably mainly contains the carbon material particles, the resin particles, or a combination thereof. The sum of the contents of the carbon material particles and the resin particles contained in the coating layer is preferably 50% by mass or more, more preferably 70% by mass or more, and further preferably 80% by mass or more with respect to the entire coating layer. Thereby, cracking and the like of the positive electrode active material on the laminated surface of the positive electrode active material layer and the inorganic particle layer can be more effectively suppressed, and an increase in resistance at low temperature accompanying charge and discharge cycles can be suppressed. The sum of the contents of the carbon material particles and the resin particles contained in the coating layer is preferably 7% by mass or more and 21% by mass or less, and more preferably 9% by mass or more and 17% by mass or less with respect to the positive electrode active material layer and the coating layer. Thereby, while maintaining the energy density of the positive electrode, the exposure of the positive electrode active material on the laminated surface of the positive electrode active material layer and the inorganic particle layer can be more effectively suppressed, and an increase in resistance at low temperature accompanying charge and discharge cycles can be more suppressed.

[0104] The thickness of the coating layer is preferably 1 μm or more and 10 μm or less, more preferably 2 μm or more and 5 μm or less. Thereby, while maintaining the energy density of the positive electrode, the exposure of the positive electrode active material on the lamination surface with the inorganic particle layer of the positive electrode active material layer can be more effectively suppressed, and the increase in resistance at low temperature associated with charge-discharge cycles can be more suppressed.

[0105] The coating layer is provided, for example, by applying a coating layer forming paste containing carbon material particles, resin particles, and a dispersion medium to the surface of the positive electrode active material layer. The coating layer may be formed by coating a coating powder containing carbon material particles and resin particles on the surface of the positive electrode active material layer and heating at a temperature equal to or higher than the melting point of the resin particles.

[0106] When the positive electrode has a coating layer that covers at least a part of the surface of the positive electrode active material layer, and the coating layer contains carbon material particles, resin particles, or a combination thereof as a main component, the ratio of the elements constituting the positive electrode active material to all elements can be less than 38 atomic% on the lamination surface with the inorganic particle layer of the positive electrode active material layer. At this time, the content of the conductive agent in the positive electrode active material layer is preferably 1 mass% or more and 15 mass% or less, more preferably 3 mass% or more and 12 mass% or less. By setting the content of the conductive agent within the above range, the energy density of the secondary battery can be increased.

[0107] In the above embodiment, the case where the non-aqueous electrolyte storage element is used as a non-aqueous electrolyte secondary battery (for example, a lithium ion secondary battery) capable of charge and discharge has been described, but the type, shape, dimensions, capacity, etc. of the non-aqueous electrolyte storage element are arbitrary. The present invention can also be applied to various secondary batteries, electric double layer capacitors, or capacitors such as lithium ion capacitors.

[0108] In the non-aqueous electrolyte storage element and the power storage device of the above embodiment, the mode in which a plurality of non-aqueous electrolyte storage elements are compressed by a pressing member has been described, but other modes in which one non-aqueous electrolyte storage element is compressed by a pressing member can also be adopted.

[0109] In the power storage device of the above embodiment, the aspect in which the pressing member has a plurality of support portions has been described. However, for example, an aspect in which the pressing member has one support portion can also be adopted. In this case, for example, the support portion is in contact with the bottom surfaces of the plurality of non-aqueous electrolyte power storage elements and the outer side surfaces on both sides in the direction perpendicular to the above-described arrangement direction of the plurality of non-aqueous electrolyte power storage elements, and is bent so that the upper side is open (that is, the cross-sectional shape viewed in the arrangement direction is U-shaped). It can be formed by one bent plate.

[0110] In the power storage device of the above embodiment, the aspect in which the pressing force adjustment portion is formed by a screw member has been described. However, as the pressing force adjustment portion, a connecting member other than the screw member that connects the two pressing portions and one or a plurality of support portions so that the interval between the two pressing portions can be adjusted can also be adopted.

[0111] In the power storage device of the above embodiment, the aspect in which the pressing member has a spacer portion and a support portion has been described. However, an aspect in which the pressing member does not include a spacer portion and a support portion can also be adopted. In this case, for example, the two pressing portions can be directly connected by one or a plurality of pressing force adjustment portions.

Example

[0112] Hereinafter, the present invention will be described more specifically by way of examples. The present invention is not limited to the following examples.

[0113] [From Example 1 to Example 3, Example 5 and Comparative Example 1 to Comparative Example 5] (Fabrication of positive electrode plate) As the positive electrode active material, in terms of solid content, the contents of carbon black and polyvinylidene fluoride (PVDF) were as shown in Table 1, and the content of the positive electrode active material composed of LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (NCM111) was used as the remainder, and a positive electrode mixture paste using NMP as a dispersion medium was prepared. The positive electrode mixture paste was applied to one side of the positive electrode active material at a coating amount of 0.96 g / 100 cm 2It was applied to both sides of an aluminum foil as a positive electrode substrate so as to form a positive electrode active material layer by drying and pressing, thereby obtaining a positive electrode.

[0114] (Fabrication of negative electrode plate) Graphite was used as the negative electrode active material. A negative electrode binder paste containing the negative electrode active material, SBR, and CMC in a mass ratio of 98:1:1 (in terms of solid content) with water as a dispersion medium was prepared. This negative electrode binder paste was applied to both sides of a copper foil as a negative electrode substrate so that the coating amount on one side of the negative electrode active material was 0.58 g / 100 cm 2 and a negative electrode was obtained by drying and pressing.

[0115] (Preparation of non-aqueous electrolyte) LiPF6 as an electrolyte salt was dissolved in a non-aqueous solvent obtained by mixing EC, EMC, and DMC in a volume ratio of 30:35:35 at a concentration of 1.2 mol / dm 3 to obtain a non-aqueous electrolyte.

[0116] (Fabrication of non-aqueous electrolyte energy storage device) As the separator, one having an inorganic particle layer containing alumina formed on one side of a base material layer made of a polyolefin microporous membrane was used. Through this separator, the positive electrode and the negative electrode were laminated and wound so that the inorganic particle layer faced the positive electrode to fabricate a wound electrode body. This electrode body was housed in a rectangular aluminum container, the non-aqueous electrolyte was injected therein, and then sealed.

[0117] After this sealing, charge and discharge were performed once, and then, by pressing both side surfaces of the container with a pressing member, the non-aqueous electrolyte storage element of Example 1 was obtained. At this time, the container was pressed with the pressing member so that the pressure applied to the electrode body was 0.4 MPa. In this non-aqueous electrolyte storage element, since the container was in a pressed state, the electrode body in the container was in a pressed state. The charge and discharge conditions were as follows. In an environment of 25 °C, after constant current charging to 4.2 V at a current value of 0.2 C, constant voltage charging was performed at 4.2 V. The end condition of charging was until the charging current became 0.01 C. After providing a rest for 10 minutes, discharging was performed at a constant current of 0.2 C to 2.5 V. The pressure applied to the electrode body was measured with a strain gauge type load cell.

[0118] As the pressing member, two metal plate-like pressing parts arranged in parallel so as to contact both side surfaces of the container, and one pressing force adjusting part that can connect these pressing parts by being screwed into the two pressing parts and adjust the distance therebetween (that is, the pressing force) were used. With this pressing force adjusting part, one non-aqueous electrolyte storage element was put in a pressed state. The above pressure adjustment was performed by adjusting the screwing amount of the pressing force adjusting part.

[0119] [Examples 4 and 6] A carbon paste containing carbon black and PVDF at a mass ratio of 4.5:2 in terms of solid content and using NMP as a dispersion medium was prepared. The non-aqueous electrolyte storage element of Example 4 was produced in the same procedure as Example 2, except that this carbon paste was applied to the surface of the positive electrode active material layer so that the one-sided coating amount was 0.02 g / 100 cm 2 The non-aqueous electrolyte storage element of Example 6 was produced in the same procedure as Comparative Example 1, except that this carbon paste was applied to the surface of the positive electrode active material layer so that the one-sided coating amount was 0.02 g / 100 cm 2 to form a coating layer.

[0120] [Comparative Example 3] A non-aqueous electrolyte storage device of Comparative Example 3 was produced in the same procedure as in Example 1, except that the positive electrode and the negative electrode were laminated via a separator such that the inorganic particle layer faced the negative electrode. [Comparative Example 4] A non-aqueous electrolyte storage device of Comparative Example 4 was produced in the same procedure as in Example 1, except that the positive electrode and the negative electrode were laminated via a separator without an inorganic particle layer. [Comparative Example 5] A non-aqueous electrolyte storage device of Comparative Example 5 was produced in the same procedure as in Example 1, except that compression by a compression member was not performed.

[0121] (Ratio of the element constituting the positive electrode active material to all elements) The ratio (atomic %) of the element constituting the positive electrode active material to all elements was calculated by the above method. As the scanning electron microscope-energy dispersive X-ray analyzer, "Phenom ProX" manufactured by Phenom-World was used.

[0122] (Charge and discharge cycle test) After each non-aqueous electrolyte storage device was stored in a thermostat at 45°C for 3 hours, it was charged at a constant current up to 4.2V at a current value of 1C, and then charged at a constant voltage at 4.2V. The end condition of charging was until the charging current reached 0.01C. Thereafter, constant current discharge was performed at a current value of 1C down to 2.5V, and a 10-minute pause was provided. These charging and discharging steps were taken as one cycle, and this cycle was repeated 300 times. Charging, discharging, and pausing were all performed in a thermostat at 45°C.

[0123] (Rate of increase in low-temperature DC resistance (DCR) after charge and discharge cycle test) The increase rate of the low-temperature direct current resistance (DCR) of the non-aqueous electrolyte storage element after the above charge-discharge cycle test was evaluated. For each non-aqueous electrolyte storage element before the charge-discharge cycle test and after the charge-discharge cycle test of 300 cycles, in a constant temperature bath at 25°C, constant current charging was performed at a current value of 0.1C to make the SOC (State of Charge) 50%. After each non-aqueous electrolyte storage element was stored in a constant temperature bath at -10°C for 4 hours, it was discharged for 30 seconds at current values of 0.2C, 0.5C, and 1C respectively. The voltage 10 seconds after the start of discharge was plotted on the vertical axis, and the discharge current value was plotted on the horizontal axis, and the DCR value, which is the value corresponding to the slope of the straight line, was obtained. Table 1 shows the relative values with the value of Example 1 set to 100 for the low-temperature DCR increase rate obtained by the following formula. Low-temperature DCR increase rate = (Low-temperature DCR after charge-discharge cycle test / Low-temperature DCR before charge-discharge cycle test) × 100

[0124] The evaluation results are shown in Table 1 below.

[0125]

Table 1

[0126] As shown in Table 1, in the state where the electrode body was compressed, the positive electrode active material layer was laminated on the inorganic particle layer, and in Examples 1 to 6 where the ratio of the elements constituting the positive electrode active material to all elements on the lamination surface of the positive electrode active material layer and the inorganic particle layer was less than 38 atomic%, regardless of the presence state of the material that suppresses the exposure of the positive electrode active material, the increase in resistance at low temperature accompanying the charge-discharge cycle was suppressed.

[0127] On the other hand, in Comparative Example 1 and Comparative Example 2 where the ratio of the elements constituting the positive electrode active material to all elements on the lamination surface of the positive electrode active material layer and the inorganic particle layer was 38 atomic% or more, and in Comparative Example 3 where the negative electrode active material layer was laminated on the surface of the inorganic particle layer, the increase rate of resistance at low temperature accompanying the charge-discharge cycle was higher than that of the examples.

[0128] In Comparative Example 4, which has a separator without an inorganic particle layer, since the decomposition of the electrolytic solution could not be suppressed during charge and discharge cycles, it is presumed that the rate of increase in resistance at low temperatures associated with the charge and discharge cycles became extremely high. Also, in Comparative Example 5 where there was no compression, the rate of increase in resistance at low temperatures associated with the charge and discharge cycles was high. This is thought to be because the gas generated by the decomposition of the non-aqueous electrolyte during charge and discharge was present between the positive and negative electrodes, causing the resistance at low temperatures to increase. In contrast, in Examples 1 to 6, due to the compression of the electrode body, the generated gas could be discharged from inside the electrode body, and as a result, it is considered that the increase in resistance at low temperatures associated with the charge and discharge cycles was suppressed.

[0129] As a result of the above, the non-aqueous electrolyte storage element includes a compressed electrode body, the positive electrode active material layer is laminated on the inorganic particle layer of the separator, and the ratio of the elements constituting the positive electrode active material to all elements on the lamination surface of the positive electrode active material layer and the inorganic particle layer is less than 38 atomic%, indicating that an increase in resistance at low temperatures associated with charge and discharge cycles can be suppressed.

Explanation of Signs

[0130] 1 Non-aqueous electrolyte storage element 2 Electrode body 3 Container 4 Positive electrode terminal 41 Positive electrode lead 5 Negative electrode terminal 51 Negative electrode lead 6 Compression member 61 Compression part 62 Spacer part 63 Support part 64 Compression force adjustment part 20 Power storage device 30 Battery pack

Claims

1. An electrode body in which a negative electrode and a positive electrode are laminated via a separator, a non-aqueous electrolyte, a container for housing the electrode body and comprising: the container being compressed in the thickness direction of the electrode body, the separator having an inorganic particle layer, the inorganic particle layer containing inorganic particles and at least one binder selected from the group consisting of fluororesins, estramers and polysaccharide polymers, or a thermoplastic resin, the positive electrode having a positive electrode active material layer containing a positive electrode active material, the positive electrode active material layer being laminated on the inorganic particle layer, the positive electrode active material containing a transition metal oxide, on the lamination surface of the positive electrode active material layer and the inorganic particle layer, the ratio of the elements constituting the positive electrode active material to all the elements on the lamination surface of the positive electrode active material layer being less than 38 atomic %, 、 on the lamination surface of the positive electrode active material layer, at least a part of the surface of the positive electrode active material is exposed, and the positive electrode active material layer further contains carbon material particles, resin particles or a combination thereof, and the carbon material particles, the resin particles or a combination thereof are uniformly present in the positive electrode active material layer, a non-aqueous electrolyte storage element.

2. The non-aqueous electrolyte storage element according to claim 1, wherein the content of the carbon material particles, the resin particles or a combination thereof in the positive electrode active material layer is 7% by mass or more and 21% by mass or less.

3. An electrode body in which a negative electrode and a positive electrode are laminated via a separator, a non-aqueous electrolyte, a container for housing the electrode body and comprising: the container being compressed in the thickness direction of the electrode body, the separator having an inorganic particle layer, the positive electrode having a positive electrode active material layer containing a positive electrode active material, the positive electrode active material layer being laminated on the inorganic particle layer, the positive electrode active material containing a transition metal oxide, the positive electrode having a coating layer covering at least a part of the surface of the positive electrode active material layer, the coating layer being interposed between the positive electrode active material layer and the inorganic particle layer, the coating layer being mainly composed of carbon material particles, resin particles or a combination thereof, the combination of the positive electrode active material layer and the coating layer or the coating layer covering the entire surface on the lamination surface of the layer formed thereby and the inorganic particle layer, on the lamination surface of the layer, the ratio of the elements constituting the positive electrode active material to all the elements is less than 38 atomic %, a non-aqueous electrolyte storage element.

4. The non-aqueous electrolyte storage element according to claim 1, claim 2 or claim 3, wherein the pressure applied to the electrode body by the compression is 0.4 MPa or more.

5. One or more non-aqueous electrolyte storage elements according to any one of Claims 1 to 4, and a pressing member, wherein the pressing member presses the electrode body of the non-aqueous electrolyte storage element by pressing the container, a power storage device.

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