WO2022009734A1

WO2022009734A1 - Nonaqueous electrolyte power storage element

Info

Publication number: WO2022009734A1
Application number: PCT/JP2021/024557
Authority: WO
Inventors: 直樹上原
Original assignee: 株式会社Ｇｓユアサ
Priority date: 2020-07-06
Filing date: 2021-06-29
Publication date: 2022-01-13
Also published as: JPWO2022009734A1

Abstract

A nonaqueous electrolyte power storage element according to an aspect of the present invention comprises a negative electrode having a negative electrode active material layer containing an acrylic resin, a positive electrode, a first separator layer, and a second separator layer. The first separator layer is interposed between the negative electrode and the positive electrode. The second separator layer is interposed between the negative electrode and the first separator layer. The porosity of the second separator layer is higher than that of the first separator layer.

Description

Non-aqueous electrolyte power storage element

The present invention relates to a non-aqueous electrolyte power storage element.

Non-aqueous electrolyte secondary batteries represented by lithium-ion non-aqueous electrolyte secondary batteries are widely used in personal computers, electronic devices such as communication terminals, automobiles, etc. due to their high energy density. The non-aqueous electrolyte secondary battery generally includes an electrode body having a pair of electrodes electrically separated by a separator, and a non-aqueous electrolyte interposed between the electrodes, and transfers ions between the two electrodes. It is configured to charge and discharge by doing. In addition, capacitors such as lithium ion capacitors and electric double layer capacitors are also widely used as power storage elements other than non-aqueous electrolyte secondary batteries.

From the viewpoint of improving fuel efficiency, a non-aqueous electrolyte secondary battery that can be charged with a large current and has high charge acceptance performance is required as an energy source for the above-mentioned automobiles and the like. For example, Patent Document 1 describes a technique for improving the charge acceptability of a lithium ion secondary battery by combining a non-aqueous electrolytic solution containing a specific compound with a negative electrode active material containing a specific lithium storage alloy and an element. Proposed.

Japanese Unexamined Patent Publication No. 2007-188871

The non-aqueous electrolyte storage element using acrylic resin as the binder of the negative electrode active material layer containing the negative electrode active material has higher charge acceptance performance than the non-aqueous electrolyte storage element using styrene-butadiene rubber as the binder. However, the non-aqueous electrolyte power storage element using acrylic resin as the binder of the negative electrode active material layer tends to increase the resistance after the charge / discharge cycle.

The present invention has been made based on the above circumstances, and a non-aqueous electrolyte power storage element capable of suppressing an increase in resistance after a charge / discharge cycle even when an acrylic resin is used as a binder for the negative electrode active material layer. The purpose is to provide.

The non-aqueous electrolyte power storage element according to one aspect of the present invention includes a negative electrode having a negative electrode active material layer containing an acrylic resin, a positive electrode, a first separator layer, and a second separator layer. The layer is interposed between the negative electrode and the positive electrode, the second separator layer is interposed between the negative electrode and the first separator layer, and the porosity of the second separator layer is higher than that of the first separator layer.

The non-aqueous electrolyte power storage element according to one aspect of the present invention can suppress an increase in resistance after a charge / discharge cycle even when an acrylic resin is used as the binder of the negative electrode active material layer.

It is an external perspective view which shows the non-aqueous electrolyte power storage element which concerns on one Embodiment of this invention. It is a schematic diagram which shows the power storage device which was configured by gathering a plurality of non-aqueous electrolyte power storage elements which concerns on one Embodiment of this invention.

As described above, the non-aqueous electrolyte power storage element using acrylic resin as the binder of the negative electrode active material layer is superior in charge acceptability as compared with the non-aqueous electrolyte power storage element using styrene-butadiene rubber as the binder, but it is filled. The resistance after the discharge cycle tends to increase. However, the non-aqueous electrolyte power storage element includes a first separator layer interposed between the negative electrode and the positive electrode, and a second separator layer interposed between the negative electrode and the first separator layer having a higher porosity than the first separator layer. It is possible to suppress an increase in resistance after a charge / discharge cycle. The reason for this is not clear, but it can be thought of as follows. When acrylic resin is used as the binder for the negative electrode active material layer, the acrylic resin has a high swelling rate with respect to the non-aqueous electrolyte, so that the binder swells due to the non-aqueous electrolyte as the charge / discharge cycle progresses, and the negative electrode active material layer expands. It's easy to do. Therefore, when a separator having a low pore ratio is opposed to the negative electrode active material layer using acrylic resin as the binder, the negative electrode active material layer expands and invades the pores of the separator, and the pores of the separator are clogged. By causing this, it is considered that the resistance of the non-aqueous electrolyte power storage element is significantly increased. The non-aqueous electrolyte power storage element has a second separator layer having a high porosity facing the negative electrode active material layer using an acrylic resin as a binder, so that the pores of the first separator layer having a low porosity can be obtained. It is possible to suppress the invasion of the negative electrode active material layer and prevent the occurrence of clogging of the first separator layer. As a result, it is considered that the effect of suppressing the increase in resistance of the non-aqueous electrolyte power storage element after the charge / discharge cycle is improved. Therefore, the non-aqueous electrolyte power storage element can suppress an increase in resistance after the charge / discharge cycle while taking advantage of the characteristics of the acrylic resin having high charge acceptance performance. The "porosity" is a volume-based value, and is calculated from the mass per unit area, the thickness, and the true density of the constituent materials.

It is preferable that the first separator layer contains a synthetic resin as a main component and the second separator layer contains inorganic particles. Since the first separator layer contains a synthetic resin as a main component and the second separator layer contains inorganic particles, the effect of suppressing the invasion of the negative electrode active material layer into the pores of the first separator layer can be enhanced. , The effect of suppressing the increase in resistance of the non-aqueous electrolyte storage element after the charge / discharge cycle can be further improved. Here, the "main component" means the component having the highest content.

It is preferable that the second separator layer is further interposed between the positive electrode and the first separator layer. More specifically, at least one second separator layer is interposed between one surface of the negative electrode and the first separator layer, and the other at least one second separator layer is between the other surface of the positive electrode and the first separator layer. It is preferable to intervene in. By providing the second separator layer containing the inorganic particles on the side facing the positive electrode, the oxidation of the synthetic resin due to the direct contact of the first separator layer containing the synthetic resin as a main component with the positive electrode is suppressed. The first separator layer can be protected.

It is preferable that the porosity of the second separator layer is 45% by volume or more and 85% by volume or less. When the porosity of the second separator layer is 45% by volume or more and 85% by volume or less, it is possible to suppress the occurrence of clogging of the pores of the second separator layer and to activate the negative electrode on the pores of the first separator layer. It is possible to suppress the invasion of the material layer.

Hereinafter, the non-aqueous electrolyte power storage device according to the embodiment of the present invention will be described in detail.

<Non-water electrolyte power storage element>
The non-aqueous electrolyte power storage element according to the embodiment of the present invention includes a negative electrode, a positive electrode, and a non-aqueous electrolyte. Hereinafter, the non-aqueous electrolyte secondary battery will be described as an example of the non-aqueous electrolyte power storage element. The positive electrode and the negative electrode form an electrode body that is alternately superimposed by laminating or winding via a first separator layer and a second separator layer. The electrode body is housed in a case, and the case is filled with a non-aqueous electrolyte. The non-aqueous electrolyte is interposed between the positive electrode and the negative electrode. Further, as the above case, a known metal case, resin case or the like which is usually used as a case of a non-aqueous electrolyte secondary battery can be used.

[Negative electrode]
The negative electrode has a negative electrode base material and a negative electrode active material layer. The negative electrode active material layer contains a negative electrode active material. The negative electrode active material layer is laminated directly or via an intermediate layer along at least one surface of the negative electrode base material.

(Negative electrode base material)
The negative electrode base material is a base material having conductivity. As the material of the negative electrode base material, a metal such as copper, nickel, stainless steel, nickel-plated steel or an alloy thereof is used, and copper or a copper alloy is preferable. Further, examples of the form of the negative electrode base material include foil, a vapor-deposited film, a mesh, a porous material, and the like, and foil is preferable from the viewpoint of cost. Therefore, a copper foil or a copper alloy foil is preferable as the negative electrode base material. Examples of the copper foil include rolled copper foil and electrolytic copper foil. Whether or not having a "conductive" is the volume resistivity is measured according to JIS-H-0505 (1975 years) is equal to 1 × 10 ⁷ Ω · cm as a threshold value.

(Negative electrode active material layer)
The negative electrode active material layer contains a negative electrode active material. The negative electrode active material layer contains an acrylic resin as a binder.

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 capable of occluding and releasing lithium ions is usually used. Examples of the negative electrode active material include metal Li; metal or semi-metal such as Si and Sn; metal oxide or semi-metal oxide such as Si oxide, Ti oxide and Sn oxide; Li ₄ Ti ₅ O ₁₂ ; Titanium-containing oxides such as LiTIO _{2 and} TiNb ₂ O ₇ ; polyphosphate compounds; silicon carbide; non-graphites such as graphite (graphite), non-graphitizable carbon (hard carbon) and easily graphitizable carbon (soft carbon). Examples include carbon materials such as carbon. Among these materials, graphite and non-graphitic carbon are preferable. In the negative electrode active material layer, one of these materials may be used alone, or two or more of them may be mixed and used.

_{“Graphite” refers to a carbon material having an average lattice spacing (d 002} ) of (002) planes determined by X-ray diffraction before charging / discharging 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.
_{"Non-graphitic carbon" refers to a carbon material having an average lattice spacing (d 002} ) of the (002) plane determined by X-ray diffraction before charging / discharging or in a discharged state of 0.34 nm or more and 0.42 nm or less. Say. Examples of non-graphitizable carbon include non-graphitizable carbon and easily graphitizable carbon. Examples of the non-planar carbon include a resin-derived material, a petroleum pitch or a petroleum pitch-derived material, a petroleum coke or a petroleum coke-derived material, a plant-derived material, an alcohol-derived material, and the like. The “non-graphitizable carbon” _{refers to a carbon material having d 002} of 0.36 nm or more and 0.42 nm or less. The “graphitizable carbon” _{refers to a carbon material having d 002} of 0.34 nm or more and less than 0.36 nm.

Here, the "discharged state" means a state in which the carbon material, which is the negative electrode active material, is discharged so as to sufficiently release lithium ions that can be occluded and discharged by charging and discharging. For example, in a half cell in which a negative electrode containing a carbon material as a negative electrode active material is used as a working electrode and metallic Li is used as a counter electrode, the open circuit voltage is 0.7 V or more.

The content of the negative electrode active material in the negative electrode active material layer is not particularly limited, but the lower limit thereof is preferably 50% by mass, more preferably 80% by mass, and even more preferably 90% by mass. On the other hand, the upper limit of this content is preferably 99% by mass, more preferably 98% by mass.

The negative electrode active material layer includes typical non-metal elements such as B, N, P, F, Cl, Br, I, Li, Na, Mg, Al, K, Ca, Zn, Ga, Ge, Sn, Sr, Ba and the like. Typical metal elements such as Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Mo, Zr, Ta, Hf, Nb, W, etc. It may be contained as a component other than the thickener and the filler.

The negative electrode active material is usually 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, the average particle size thereof may be 1 μm or more and 100 μm or less. When the negative electrode active material is Si, Sn, Si oxide, Sn oxide or the like, the average particle size thereof 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 higher than the above lower limit, the production or handling of the negative electrode active material becomes easy. By setting the average particle size of the negative electrode active material to the above upper limit or less, the electron conductivity of the active material layer is improved. A crusher, a classifier, or the like is used to obtain a powder having a predetermined particle size. When the negative electrode active material is a metal such as metal Li, the negative electrode active material may be in the form of a foil.

The negative electrode active material layer contains an acrylic resin as a binder. Examples of the "acrylic resin" include a polymer of an acrylic acid ester or a methacrylic acid ester, a copolymer containing polyacrylamide, an acrylic acid ester or a methacrylic acid ester, and the like.

The content of the acrylic resin in the binder is preferably 99% by mass or more, and may be 100% by mass.

The lower limit of the content of the binder in the negative electrode active material layer is preferably 0.2% by mass, more preferably 0.3% by mass, 0.4% by mass, or 0.5% by mass from the viewpoint of ensuring adhesion. In some cases, 0.8% by mass is even more preferable, 0.9% by mass is even more preferable, and 1.0% by mass is particularly preferable. On the other hand, as the upper limit of this content, from the viewpoint of improving output performance, 10% by mass is preferable, 5% by mass is more preferable, 3% by mass, 2% by mass% and 1% by mass are more preferable, and 0.8% by mass. May be particularly preferred.

The negative electrode active material layer contains optional components such as a conductive agent, a thickener, and a filler, if necessary.

The conductive agent is not particularly limited as long as it is a conductive material. The carbon materials such as graphite, graphitizable carbon, and non-graphitizable carbon also have conductivity, but are not included in the conductive agent in the negative electrode active material layer. Examples of the conductive agent other than the carbon material include other carbonaceous materials, metals, conductive ceramics and the like. Examples of other carbonaceous materials include other non-graphitic carbons, graphene-based carbons and the like. Examples of other non-graphular carbons include carbon nanofibers, pitch-based carbon fibers, and carbon black. Examples of carbon black include furnace black, acetylene black, and ketjen black. Examples of graphene-based carbons include graphene, carbon nanotubes (CNTs), fullerenes and the like. Examples of the shape of the conductive agent include powder and fibrous. 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 combined and used. For example, a material in which carbon black and CNT are combined may be used. Among these, carbon black is preferable from the viewpoint of electron conductivity and coatability, and acetylene black is particularly preferable.

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, it is preferable to inactivate this functional group by methylation or the like in advance.

The filler is not particularly limited. Examples of the main component of the filler include polyolefins such as polypropylene and polyethylene, silica, alumina, zeolite, and glass.

The lower limit of the average thickness of one side of the negative electrode active material layer is not particularly limited, but may be 30 μm, preferably 40 μm, 44 μm, 49 μm, 50 μm, and 55 μm, 59 μm, 60 μm, or 62 μm. More preferably, 64 μm is even more preferable. When the average thickness of one side of the negative electrode active material layer is at least the above lower limit, the energy density of the non-aqueous electrolyte power storage element can be increased. The upper limit of the average thickness of one side of the negative electrode active material layer is not particularly limited, but may be 90 μm, preferably 80 μm, 79 μm, or 77 μm, and more preferably 75 μm, 74 μm, or 72 μm. .. When the average thickness of one side of the negative electrode active material layer is not more than the above upper limit, the output performance of the non-aqueous electrolyte power storage element can be improved, and the negative electrode active material layer penetrates into the pores of the first separator layer. This can be suppressed, and clogging of the first separator layer can be suppressed with high certainty.
Energy density when a non-aqueous electrolyte power storage element is used as a power supply for automobiles such as electric vehicles (EV) and plug-in hybrid vehicles (PHEV), and as a power supply device for auxiliary power supply devices and uninterruptible power supply devices (UPS). The average thickness of one side of the negative electrode active material layer is preferably 50 μm or more and 90 μm or less, and more preferably 62 μm or more and 77 μm or less. When a non-aqueous electrolyte power storage element is used as a power source for an automobile such as a hybrid electric vehicle (HEV), the average thickness of one side of the negative electrode active material layer is preferably 30 μm or more and 50 μm or less, preferably 32 μm, from the viewpoint of improving output performance. More preferably 48 μm or more.

(Middle layer)
The intermediate layer is a coating layer on the surface of the negative electrode base material, and contains a conductive agent such as carbon particles to reduce the contact resistance between the negative electrode base material and the negative electrode active material layer. The composition of the intermediate layer is not particularly limited, and can be formed by, for example, a composition containing a binder and a conductive agent.

[Positive electrode]
The positive electrode has a positive electrode base material and a positive electrode active material layer. The positive electrode active material layer contains a positive electrode active material. The positive electrode active material layer is laminated directly or via an intermediate layer along at least one surface of the positive electrode base material. The configuration of the intermediate layer is not particularly limited, and can be selected from, for example, the configurations exemplified by the negative electrode.

(Positive electrode base material)
The positive electrode base material is a base material having conductivity. As the material of the positive electrode base material, metals such as aluminum, titanium, tantalum, and stainless steel or alloys thereof are used. Among these, aluminum and aluminum alloys are preferable from the viewpoint of the balance between potential resistance, high conductivity and cost. Examples of the form of the positive electrode base material include foil, a vapor-deposited film, a mesh, a porous material, and the like, and foil is preferable from the viewpoint of cost. Therefore, aluminum foil or aluminum alloy foil is preferable as the positive electrode base material. Examples of aluminum or aluminum alloy include A1085, A3003, and A1N30 specified in JIS-H4000 (2014) or JIS-H4160 (2006).

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, further 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 base material in the above range, it is possible to increase the energy density per volume of the secondary battery while increasing the strength of the positive electrode base material.

(Positive electrode active material layer)
The positive electrode active material layer contains a positive electrode active material. As the positive electrode active material, for example, a known positive electrode active material can be appropriately selected. As the positive electrode active material for a lithium ion secondary battery, a material capable of occluding and releasing lithium ions is usually used. Examples of the positive electrode active material include _{a lithium transition metal composite oxide having an α-NaFeO type 2} crystal structure, a lithium transition metal composite oxide having a spinel type crystal structure, a polyanionic compound, a chalcogen compound, sulfur and the like. Examples of the lithium transition metal composite oxide having an _{α-NaFeO type 2} _{crystal structure include Li [Li x} Ni _(1-x) ] O ₂ (0 ≦ x <0.5) and Li [Li _x Ni _γ Co _{(0 ≦ x <0.5). _{1-x-γ)] O}} 2 (0 ≦ x <0.5,0 <γ <1), Li [Li x Co (1-x)] O 2 (0 ≦ x <0.5), Li [ Li _x Ni _γ Mn _(1-x-γ) ] O ₂ (0 ≦ x <0.5, 0 <γ <1), Li [Li _x Ni _γ Mn _β Co _(1-x-γ-β) ] O ₂ (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) ] O ₂ ( Examples thereof include 0 ≦ x <0.5, 0 <γ, 0 <β, 0.5 <γ + β <1). Examples of the lithium transition metal composite oxide having a spinel-type crystal structure include Li _x Mn ₂ O ₄ and Li _x Ni _γ Mn _(2-γ) O ₄ . Examples of the polyanionic compound include LiFePO ₄ , LiMnPO ₄ , LiNiPO ₄ , LiCoPO ₄ , Li ₃ V ₂ (PO ₄ ) ₃ , Li ₂ MnSiO ₄ , Li ₂ CoPO ₄ F and the like. Examples of the chalcogen compound include titanium disulfide, molybdenum disulfide, molybdenum dioxide and the like. The atoms or polyanions in these materials may be partially substituted with atoms or anion species consisting of other elements. Among these, the lithium transition metal composite oxide is preferable as the positive electrode active material from the viewpoint of increasing energy density, and a nickel cobalt manganese-containing lithium transition metal composite containing nickel, cobalt and manganese as constituent elements in addition to Li is preferable. Oxides are more preferred.

The surface of the material listed as the positive electrode active material may be coated with another material. In the positive electrode active material layer, one of these materials may be used alone, or two or more of them may be mixed and used.

The content of the positive electrode active material in the positive electrode active material layer is not particularly limited, but the lower limit thereof is preferably 50% by mass, more preferably 80% by mass, and even more preferably 90% by mass. On the other hand, as the upper limit of this content, 99% by mass is preferable, and 98% by mass is more preferable.

The positive electrode active material layer contains optional components such as a conductive agent, a binder, a thickener, and a filler, if necessary. Optional components such as a conductive agent, a binder, a thickener, and a filler can be selected from the materials exemplified for the negative electrode. In the positive electrode active material layer, carbon materials such as graphite, graphitizable carbon, and non-graphitizable carbon are also included in the conductive agent.

The binder of the positive electrode active material layer is not particularly limited, and is, for example, a fluororesin (polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), etc.), a thermoplastic resin such as polyethylene, polypropylene, polyimide; ethylene-propylene-. Elastomers such as diene rubber (EPDM), sulfonated EPDM, styrene butadiene rubber (SBR), and fluororubber; polysaccharide polymers and the like can be mentioned.

[Separator]
The non-aqueous electrolyte power storage element includes a first separator layer and a second separator layer. The first separator layer is interposed between the negative electrode and the positive electrode, and the second separator layer is interposed between the negative electrode and the first separator layer. The first separator layer and the second separator layer are infiltrated with a non-aqueous electrolyte. The first separator layer and the second separator layer separate the positive electrode and the negative electrode, and hold a non-aqueous electrolyte between the positive electrode and the negative electrode.

The porosity of the second separator layer is higher than the porosity of the first separator layer. The non-aqueous electrolyte power storage element has a charge / discharge cycle in which a second separator layer having a higher porosity than the first separator layer is arranged facing the negative electrode active material layer using an acrylic resin as a binder. The effect of suppressing the subsequent increase in resistance is improved.

The lower limit of the porosity of the first separator layer is preferably 30%, more preferably 31%, 32%, 33%, 34%, or 35%, and 36%, 37%, 38. %, 39%, or 40% may be preferred. By setting the porosity of the first separator layer to be equal to or higher than the above lower limit, the permeability of the non-aqueous electrolyte can be improved. On the other hand, the upper limit of the porosity of the first separator layer is preferably 50%, more preferably 49%, 48%, 47%, 46%, or 45%, and 44%, 43%. , 42%, 41%, or 40% is more preferred. By setting the porosity of the first separator layer to the above upper limit or less, the strength of the first separator layer can be improved.

The lower limit of the porosity of the second separator layer is preferably 45%, more preferably 46%, 47%, 48%, 49% or 50%. By setting the porosity of the second separator layer to be equal to or higher than the above lower limit, the permeability of the non-aqueous electrolyte can be improved. On the other hand, the upper limit of the porosity of the second separator layer may be 90%, preferably 88%, 87%, 86%, or 85%, and 84%, 83%, 82%, 81%, and so on. Or 80% is more preferable. By setting the porosity of the second separator layer to the above upper limit or less, the strength of the second separator layer can be improved.

The difference between the porosity of the first separator layer and the porosity of the second separator layer is preferably 5% or more and 55% or less, more preferably 8% or more and 49% or less, and further preferably 9% or more and 48% or less. It is preferable, and 10% or more and 45% or less are particularly preferable. By setting the difference in porosity within the above range, it is possible to suppress the penetration of the negative electrode active material layer into the pores of the first separator layer, further suppress the clogging of the first separator layer, and further suppress the clogging of the separator. A good balance between strength and permeability can be achieved.

The porosity of the first separator layer and the second separator layer is calculated from the following formula. ^{Here, W is the mass [g / cm 2} ] per unit area of the first separator layer and the second separator layer, and ρ is the true density [g / cm 2] of the material constituting the first separator layer or the second separator layer. cm ³ ], where t is the thickness [cm] of the first separator layer or the second separator layer.
Porosity (%) = 100- (W / (ρ × t)) × 100

The first separator layer preferably contains a synthetic resin as a main component. Since the first separator layer contains a synthetic resin as a main component, the strength is excellent. The synthetic resin as the main component of the first separator layer is not particularly limited, and examples thereof include polyolefins, polyesters, polyimides, polyamides (aromatic polyamides, aliphatic polyamides, etc.) and the like. Polyolefins shall also include copolymers of olefins and other monomers. Examples of the polyolefin include polyethylene (PE), polypropylene (PP), ethylene-propylene copolymer, ethylene-vinyl acetate copolymer, ethylene-methyl acrylate copolymer, ethylene-ethyl acrylate copolymer, chlorinated polyethylene and the like. Examples thereof include a polyolefin derivative and an ethylene-propylene copolymer.

Among these resins, polyolefins, polyesters and aliphatic polyamides are preferable, polyolefins are more preferable, and PE and PP are even more preferable. PE and PP can exert a good shutdown function.

As the structure of the first separator layer, for example, a woven fabric, a non-woven fabric, a microporous film, or the like is used. Among these, a non-woven fabric and a microporous membrane are preferable, and a microporous membrane is more preferable. The microporous membrane has advantages such as high strength. Nonwoven fabric has advantages such as high liquid retention.

The second separator layer preferably contains inorganic particles. Since the second separator layer contains inorganic particles, the effect of suppressing the invasion of the negative electrode active material layer into the pores of the first separator layer can be enhanced, so that the resistance of the non-aqueous electrolyte power storage element increases after the charge / discharge cycle. It is possible to further improve the suppressive effect on. The second separator layer is a porous layer. The second separator layer is usually composed of inorganic particles and a binder, and may contain other components.

Examples of the inorganic particles contained in the second separator layer include oxides such as alumina, silica, zirconia, titania, magnesia, ceria, ittria, zinc oxide and iron oxide, nitrides such as silicon nitride, titanium nitride and boron nitride, and silicon. Carbide, calcium silicate, aluminum sulfate, barium sulfate, aluminum hydroxide, potassium titanate, barium titanate, talc, kaolin ray, kaolinite, halloysite, pyrophyllite, montmorillonite, sericite, mica, amesite, bentonite, asbestos , Oxide, calcium silicate, magnesium silicate and the like. Among these, particles of alumina, silica, titania, or barium sulfate are preferable.

Specific types of the binder for the second separator layer include those exemplified as the binder for the positive electrode active material layer described above.

The second separator layer may be integrally formed with the first separator layer, or may be in a form independent of the first separator layer. Further, the second separator layer may be provided so as to cover the negative electrode active material layer.

It is preferable that the second separator layer is further interposed between the positive electrode and the first separator layer. More specifically, at least one second separator layer is interposed between one surface of the negative electrode and the first separator layer, and the other at least one second separator layer is between the other surface of the positive electrode and the first separator layer. It is preferable to intervene in. By providing the second separator layer containing the inorganic particles on the side facing the positive electrode, the synthetic resin is oxidized by the direct contact of the first separator layer containing the synthetic resin as a main component with the positive electrode. It can be suppressed and the first separator layer can be protected.

The lower limit of the average thickness of the first separator layer is preferably 4 μm, more preferably 8 μm. The upper limit of this average thickness is preferably 30 μm, more preferably 20 μm. By setting the average thickness of the first separator layer to be equal to or greater than the lower limit, it is possible to prevent a short circuit between the positive electrode and the negative electrode with high certainty. Further, by setting the average thickness of the first separator layer to be equal to or less than the upper limit, the energy density of the non-aqueous electrolyte power storage element can be increased.

The lower limit of the average thickness of the second separator layer is preferably 1 μm, more preferably 2 μm. On the other hand, the upper limit of the average thickness of the second separator layer is preferably 10 μm, more preferably 6 μm. By setting the average thickness of the second separator layer to be equal to or greater than the lower limit, it is possible to prevent the negative electrode active material layer from invading the pores of the first separator layer and to ensure that the first separator layer is clogged. It can be suppressed high. By setting the average thickness of the second separator layer to be equal to or less than the upper limit, the energy density of the non-aqueous electrolyte power storage element can be increased. When two or more second separator layers are provided, the average thickness of the second separator layers is the average value of the average thickness of each second separator layer.

The ratio of the average thickness of the second separator layer to the average thickness of the first separator layer is preferably less than 0.5, preferably 0.4 or less, and more preferably 0.3 or less. By setting the ratio of the average thickness of the second separator layer to the average thickness of the first separator layer within the above range, the energy density of the non-aqueous electrolyte power storage element can be increased. The lower limit of the ratio of the average thickness of the second separator layer to the average thickness of the first separator layer is preferably 0.1 or more, more preferably 0.2 or more. By setting the ratio of the average thickness of the second separator layer to the average thickness of the first separator layer to be equal to or higher than the above lower limit, it is possible to prevent the negative electrode active material layer from invading the pores of the first separator layer. It is possible to prevent the separator layer from being clogged with high certainty.

The lower limit of the ratio of the average thickness of the first separator layer to the average thickness of the negative electrode active material layer and the total thickness of the second separator layer is, for example, 0.05, and may be 0.10. , 0.15 is preferable, 0.20 is more preferable, and 0.25, 0.30, 0.38 may be preferable. The upper limit of the ratio of the average thickness of the first separator layer to the average thickness of the negative electrode active material layer and the total thickness of the second separator layer is, for example, 1.30, preferably 1.00. , 0.80, 0.75, 0.65 are more preferable, and 0.60, 0.50, 0.45 may be preferable. By setting the ratio of the total of the average thickness of the first separator layer and the average thickness of the second separator layer to the average thickness of the negative electrode active material layer within the above range, the energy density of the non-aqueous electrolyte power storage element can be adjusted. In addition to increasing the height, it is possible to suppress the invasion of the negative electrode active material layer into the pores of the first separator layer and more reliably suppress the clogging of the first separator layer.

The lower limit of the ratio of the average thickness of the first separator layer to the average thickness of the negative electrode active material layer is, for example, 0.04, preferably 0.08, and more preferably 0.11. The upper limit of the ratio of the average thickness of the first separator layer to the average thickness of the negative electrode active material layer is, for example, 1.00, 0.80, 0.70, 0.65, 0.50, 0. It may be .45, and 0.40 or 0.30 may be preferable. By setting the ratio of the average thickness of the first separator layer to the average thickness of the negative electrode active material layer in the above range, the energy density of the non-aqueous electrolyte power storage element is increased, and the reaction due to the expansion of the negative electrode active material layer is increased. The effect of the separator suppressing the increase in force can be enhanced.

The lower limit of the ratio of the average thickness of the second separator layer to the average thickness of the negative electrode active material layer is, for example, 0.01, preferably 0.02, 0.04, 0.06, 0.08. Is more preferable. The upper limit of the ratio of the average thickness of the second separator layer to the average thickness of the negative electrode active material layer is, for example, 0.33, preferably 0.20, 0.17, 0.13, and 0.10. , 0.08. By setting the ratio of the average thickness of the second separator layer to the average thickness of the negative electrode active material layer within the above range, the energy density of the non-aqueous electrolyte power storage element can be increased and the pores of the first separator layer can be increased. It is possible to suppress the invasion of the negative electrode active material layer and more reliably suppress the clogging of the first separator layer.

When the first separator layer contains a synthetic resin as a main component and the positive electrode active material layer and the first separator layer come into direct contact with each other, the upper limit charging potential of the positive electrode is 4.15 V vs. from the viewpoint of suppressing the oxidation of the first separator layer. .. Li / Li ⁺ or less is preferable, and 4.10 V vs. Li / Li ⁺ or less is more preferable. In order to set the charge upper limit potential of the positive electrode within the above range, the charge upper limit voltage of the non-aqueous electrolyte power storage element may be controlled by setting a charger or the like, but the charge / discharge reaction potential _{of LiFePO 4 or the like as the positive electrode active material.} Is 4.15V vs. Materials that are Li / Li ⁺ or less may be used.

[Non-water electrolyte]
As the non-aqueous electrolyte, a known non-aqueous electrolyte can be appropriately selected. As the non-aqueous electrolyte, a non-aqueous electrolyte solution is used. The non-aqueous electrolyte solution contains a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent.

(Non-aqueous solvent)
As the non-aqueous solvent, a known non-aqueous solvent can be appropriately selected. Examples of the non-aqueous solvent include cyclic carbonates, chain carbonates, carboxylic acid esters, phosphoric acid esters, sulfonic acid esters, ethers, amides, nitriles and the like. As the non-aqueous solvent, a solvent in which some of the hydrogen atoms contained in these compounds are replaced with halogen may be used.

Examples of the cyclic carbonate include ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), vinylene carbonate (VC), vinylethylene carbonate (VEC), chloroethylene carbonate, fluoroethylene carbonate (FEC), and difluoroethylene. Examples thereof include carbonate (DFEC), styrene carbonate, catechol carbonate, 1-phenylvinylene carbonate, 1,2-diphenylvinylene carbonate, and among these, EC is preferable.

Examples of the chain carbonate include diethyl carbonate (DEC), dimethyl carbonate (DMC), ethylmethyl carbonate (EMC), diphenyl carbonate, trifluoroethylmethyl carbonate, bis (trifluoroethyl) carbonate and the like. Among these, EMC is preferable.

As the non-aqueous solvent, it is preferable to use cyclic carbonate or chain carbonate, and it is more preferable to use cyclic carbonate and chain carbonate in combination. By using the cyclic carbonate, the dissociation of the electrolyte salt can be promoted and the ionic conductivity of the non-aqueous electrolyte solution can be improved. By using the chain carbonate, the viscosity of the non-aqueous electrolytic solution can be kept low. When the cyclic carbonate and the chain carbonate are used 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.

(Electrolyte salt)
The electrolyte salt can be appropriately selected from known electrolyte salts. Examples of the electrolyte salt include lithium salt, sodium salt, potassium salt, magnesium salt, onium salt and the like. Of these, lithium salts are preferred.

Lithium salts include inorganic lithium salts such _{as LiPF 6} , LiPO ₂ F ₂ , LiBF ₄ , LiClO ₄ , LiN (SO ₂ F) ₂ _{, LiSO 3} CF ₃ , LiN (SO ₂ CF ₃ ) ₂ , LiN (SO _2). C ₂ F ₅ ) ₂ , LiN (SO ₂ CF ₃ ) (SO ₂ C ₄ F ₉ ), LiC (SO ₂ CF ₃ ) ₃ , LiC (SO ₂ C ₂ F ₅ ) _{3 and} other halogenated hydrocarbon groups Examples thereof include lithium salts having. Among these, an inorganic lithium salt is preferable, and LiPF ₆ is more preferable.

The content of the electrolyte salt in the nonaqueous electrolytic solution, preferable to be 0.1 mol / dm ³ or more 2.5 mol / dm ³ or less, more preferable to be 0.3 mol / dm ³ or more 2.0 mol / dm ³ or less , more preferable to be 0.5 mol / dm ³ or more 1.7 mol / dm ³ or less, and particularly preferably 0.7 mol / dm ³ or more 1.5 mol / dm ³ or less. By setting the content of the electrolyte salt in the above range, the ionic conductivity of the non-aqueous electrolyte solution can be increased.

(Additive)
The non-aqueous electrolyte solution may contain additives. Examples of the additive include aromatic compounds such as biphenyl, alkyl biphenyl, terphenyl, and partially hydrides of turphenyl, cyclohexylbenzene, t-butylbenzene, t-amylbenzene, diphenyl ether, and dibenzofuran; 2-fluorobiphenyl, o. -Partial halides of the above aromatic compounds such as cyclohexylfluorobenzene and p-cyclohexylfluorobenzene; Halogenated anisole compounds; succinic anhydride, glutaric anhydride, maleic anhydride, citraconic anhydride, glutaconic anhydride, itaconic anhydride, cyclohexanedicarboxylic acid anhydride; ethylene sulfone, propylene sulfite, dimethyl sulfite, dimethyl sulfate, ethylene sulfate, Sulfone, dimethyl sulfone, diethyl sulfone, dimethyl sulfoxide, diethyl sulfoxide, tetramethylene sulfoxide, diphenyl sulfide, 4,4'-bis (2,2-dioxo-1,3,2-dioxathiolane), 4-methylsulfonyloxymethyl- Examples thereof include 2,2-dioxo-1,3,2-dioxathiolane, thioanisole, diphenyldisulfide, dipyridinium disulfide, perfluorooctane, tristrimethylsilyl borate, tristrimethylsilyl phosphate, tetrakistrimethylsilyl titanate and the like. These additives may be used alone or in combination of two or more.

The content of the additive contained in the non-aqueous electrolytic solution is preferably 0.01% by mass or more and 10% by mass or less, and more preferably 0.1% by mass or more and 7% by mass or less with respect to the total mass of the non-aqueous electrolytic solution. , 0.2% by mass or more and 5% by mass or less is more preferable, and 0.3% by mass or more and 3% by mass or less is particularly preferable. By setting the content of the additive in the above range, it is possible to improve the capacity maintenance performance or charge / discharge cycle performance of the non-aqueous electrolyte power storage element after high temperature storage, and further improve the safety.

As the non-aqueous electrolyte, a non-aqueous electrolyte solution and a solid electrolyte may be used in combination.

[Specific configuration of non-aqueous electrolyte power storage element]
The shape of the non-aqueous electrolyte power storage element of the present embodiment is not particularly limited, and examples thereof include a cylindrical battery, a pouch film type battery, a square battery, a flat type battery, a coin type battery, and a button type battery. Be done.

FIG. 1 shows a non-aqueous electrolyte power storage element 1 as an example of a square battery. The figure is a perspective view of the inside of the case 3. The electrode body 2 having the positive electrode and the negative electrode wound around the separator is housed in the square case 3. The positive electrode is electrically connected to the positive electrode terminal 4 via the positive electrode current collector 41. The negative electrode is electrically connected to the negative electrode terminal 5 via the negative electrode current collector 51. Further, a non-aqueous electrolyte is injected into the case 3.

[Manufacturing method of non-aqueous electrolyte power storage element]
The method for manufacturing a non-aqueous electrolyte power storage element according to an embodiment of the present invention includes accommodating the negative electrode, the positive electrode, and the non-aqueous electrolyte in a case. The negative electrode can be obtained by laminating the negative electrode active material layer directly on the negative electrode base material or via an intermediate layer. The laminating of the negative electrode active material layer is performed by applying a negative electrode mixture paste containing a negative electrode active material and an acrylic resin to the negative electrode base material. Further, the positive electrode can be obtained by laminating the positive electrode active material layer directly on the positive electrode base material or via an intermediate layer, similarly to the negative electrode. The laminating of the positive electrode active material layer is performed by applying a positive electrode mixture paste to the positive electrode base material. The negative electrode mixture paste and the positive electrode mixture paste may contain a dispersion solvent. As the dispersion solvent, for example, an aqueous solvent such as water or a mixed solvent mainly composed of water; an organic solvent such as N-methylpyrrolidone or toluene can be used.

Further, as described above, the method for manufacturing the non-aqueous electrolyte power storage element includes laminating the negative electrode and the positive electrode via the first separator layer and the second separator layer. The first separator layer is interposed between the negative electrode and the positive electrode, and the second separator layer is interposed between the negative electrode and the first separator layer. An electrode body is formed by laminating the negative electrode and the positive electrode via the first separator layer and the second separator layer.

The method of accommodating the negative electrode, the positive electrode, the non-aqueous electrolyte, etc. in the case can be performed by a known method. After accommodating, a non-aqueous electrolyte power storage element can be obtained by sealing the accommodating port. The details of each element constituting the non-aqueous electrolyte power storage element obtained by the above manufacturing method are as described above.

[Other embodiments]
The non-aqueous electrolyte power storage device 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 one embodiment can be added to the configuration of another embodiment, and a part of the configuration of one embodiment can be replaced with the configuration of another embodiment or a well-known technique. In addition, some of the configurations of certain embodiments can be deleted. Further, a well-known technique can be added to the configuration of a certain embodiment.

In the above embodiment, the non-aqueous electrolyte storage element has been described mainly in the form of a non-aqueous electrolyte secondary battery, but other non-aqueous electrolyte storage elements may be used. Examples of other non-aqueous electrolyte storage elements include capacitors (electric double layer capacitors, lithium ion capacitors) and the like. Examples of the non-aqueous electrolyte secondary battery include a lithium ion non-aqueous electrolyte secondary battery.

Further, in the above embodiment, the winding type electrode body is used, but the laminated type formed from the laminated body in which a plurality of sheet bodies including the positive electrode, the negative electrode, the first separator layer and the second separator layer are stacked. An electrode body may be provided.

The present invention can also be realized as a power storage device including a plurality of the above-mentioned non-aqueous electrolyte electric elements. Further, a power storage unit can be configured by using a single or a plurality of non-aqueous electrolyte power storage elements of the present invention, and a power storage device can be further configured by using the power storage unit. The power storage device can be used as a power source for automobiles such as electric vehicles (EVs), hybrid electric vehicles (HEVs), and plug-in hybrid vehicles (PHEVs). Further, the power storage device can be used for various power supply devices such as an engine starting power supply device, an auxiliary power supply device, and an uninterruptible power supply (UPS).

FIG. 2 shows an example of a power storage device 30 in which a power storage unit 20 in which two or more electrically connected non-aqueous electrolyte power storage elements 1 are assembled is further assembled. Even if the power storage device 30 includes a bus bar (not shown) for electrically connecting two or more non-aqueous electrolyte power storage elements 1 and a bus bar (not shown) for electrically connecting two or more power storage units 20. good. The power storage unit 20 or the power storage device 30 may include a condition monitoring device (not shown) for monitoring the state of one or more non-aqueous electrolyte power storage elements.

Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited to the following examples.

[Example 1 and Comparative Example 2]
(Negative electrode)
A negative electrode mixture paste containing graphite as a negative electrode active material, the binder shown in Table 1, and carboxymethyl cellulose (CMC) as a thickener, and using water as a dispersion solvent was prepared. The mixing ratio of the negative electrode active material, the binder and the thickener was 98: 1: 1 in mass ratio. The negative electrode mixture paste is applied to one side of a copper foil having a thickness of 10 μm as a negative electrode base material, dried and pressed to form a negative electrode active material layer having an average thickness of 67 μm, and the negative electrodes of Examples and Comparative Examples are formed. Got
(Non-water electrolyte)
A non-aqueous electrolyte in which _{LiPF 6} is dissolved in 1.0 mol / dm ³ in a non-aqueous solvent in which ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) are mixed at a volume ratio of 30:35:35. Got
(Positive electrode)
A positive electrode containing NCM (LiNi _0.6 Co _0.2 Mn _0.2 O ₂ ) having an α-NaFeO _{type 2} crystal structure as a positive electrode active material was prepared. A positive electrode mixture paste containing the above positive electrode active material, polyvinylidene fluoride (PVDF) as a binder, and acetylene black as a conductive agent and using N-methyl-2-pyrrolidone (NMP) as a dispersion solvent was prepared. .. The mixing ratio of the positive electrode active material, the binder and the conductive agent was 94: 3: 3 in mass ratio. The positive electrode mixture paste was applied to one side of the positive electrode base material, dried and pressed to form a positive electrode active material layer. An aluminum foil having a thickness of 15 μm was used as the positive electrode base material.
(Separator)
The separator has a porous layer containing inorganic particles and a binder (average thickness 4 μm, porosity 48%) on one side of a microporous substrate made of polyolefin (average thickness 20 μm, porosity 37%). I prepared a laminated one. Here, the microporous substrate made of polyolefin corresponds to the first separator layer, and the porous layer corresponds to the second separator layer.

(Porosity of separator)
The porosity [%] of the first separator layer and the second separator layer was calculated from the following formula.
Porosity (%) = 100- (W / (ρ × t)) × 100
W: Mass per unit area [g · cm- ² ]
ρ: True density of constituent materials [g · cm ^-3 ]
t: Thickness [cm]
Table 1 shows the porosities of the first separator layer and the second separator layer.

(Manufacturing of non-aqueous electrolyte power storage element)
A non-aqueous electrolyte power storage element using the positive electrode and the negative electrode was assembled. The positive electrode active material layer and the negative electrode active material layer face each other with the first separator layer and the second separator layer interposed therebetween, the first separator layer is interposed between the negative electrode and the positive electrode, and the second separator layer is the negative electrode. The positive electrode, the first separator layer, the second separator layer and the negative electrode were laminated so as to be interposed between the first separator layers, and the non-aqueous electrolyte was used as the non-aqueous electrolyte.

[Example 2 and Comparative Example 3]
As a separator, a porous layer containing inorganic particles and a binder on both sides of a microporous base material made of polyolefin (average thickness 14 μm, porosity 45%) (average thickness 3 μm, porosity: 58%). We used the laminated ones. Here, the microporous base material made of polyolefin corresponds to the first separator layer, and the porous layer corresponds to the second separator layer. The positive electrode, the first separator layer, the second separator layer and the negative electrode are laminated so that one second separator layer is interposed between the negative electrode and the first separator layer and the other second separator layer is interposed between the positive electrode and the first separator layer. The non-aqueous electrolyte power storage elements of Example 2 and Comparative Example 3 were obtained in the same manner as in Example 1 and Comparative Example 2 except for the above.

[Comparative Example 1 and Comparative Example 4]
As a separator, a porous layer containing inorganic particles and a binder (average thickness 4 μm, porosity: 75%) on one side of a microporous base material made of polyolefin (average thickness 14 μm, porosity 44%). Was used. Here, the microporous base material made of polyolefin corresponds to the first separator layer, and the porous layer corresponds to the second separator layer. Same as in Example 1 and Comparative Example 2 except that the positive electrode, the first separator layer, the second separator layer and the negative electrode are laminated so that the second separator layer is interposed between the positive electrode active material and the first separator layer. Then, the non-aqueous electrolyte power storage elements of Comparative Example 1 and Comparative Example 4 were obtained.

[evaluation]
(Initial performance evaluation)
Each of the obtained non-aqueous electrolyte power storage elements was subjected to constant current charging up to 4.25 V at a charging current of 0.2 C under a temperature environment of 25 ° C., and then constant voltage charged at 4.25 V. The charging end condition was set to be until the charging time reached 7 hours. After a 10-minute pause, a constant current discharge was performed at a discharge current of 0.2 C to 2.75 V, and a 10-minute pause was provided. Next, under a temperature environment of 25 ° C., constant current charging was performed up to 4.25 V at a charging current of 1.0 C, and then constant voltage charging was performed at 4.25 V. The charging end condition was until the charging time reached 3 hours. After a 10-minute pause, constant current discharge was performed at a discharge current of 1.0 C to 2.75 V. The discharge capacity at this discharge current of 1.0 C was defined as the "initial discharge capacity".
Further, each of the obtained non-aqueous electrolyte power storage elements was subjected to constant current charging at 25 ° C. with a charging current of 1.0 C to set the SOC (State of Charge) to 50%. It was charged at 25 ° C. with a charging current of 0.2C, 0.5C, or 1.0C for 30 seconds. After each charge was completed, constant current discharge was performed with a discharge current of 1.0 C to set the SOC to 50%. The relationship between the current at each charging current and the voltage 10 seconds after the start of charging was plotted, and the DC input resistance (initial DC input resistance) was obtained from the slope of a straight line obtained from the three plots.

(Charge / discharge cycle test)
Each non-aqueous electrolyte power storage element after the above initial performance evaluation was subjected to a charge / discharge cycle test under the following conditions. After storing in a constant temperature bath at 45 ° C. for 3 hours, the cells were constantly charged with a charging current of 1.0 C to a voltage of 100% SOC (State of Charge). A 10-minute rest period was provided after charging. Then, a constant current discharge was performed with a discharge current of 1.0 C to a voltage of SOC 0%, and then a rest period of 10 minutes was provided. These charging and discharging steps were regarded as one cycle, and this cycle was repeated 100 cycles. Charging, discharging and pausing were performed in a constant temperature bath at 45 ° C.

(DC input resistance increase rate after charge / discharge cycle)
After the charge / discharge cycle test, the DC input resistance (DC input resistance after the charge / discharge cycle) of each non-aqueous electrolyte storage element was determined by the same method as in the above "initial performance evaluation". The rate of increase (%) of the DC input resistance after the charge / discharge cycle with respect to the initial DC input resistance was calculated.
Then, the ratio of the DC input resistance increase rate of Example 1 and Example 2 to Comparative Example 1 and the ratio of the DC input resistance increase rate of Comparative Example 2 and Comparative Example 3 to Comparative Example 4 were obtained. The results are shown in Table 1 below.

As shown in Table 1, the negative electrode active material layer contains an acrylic resin as a binder, and the second separator layer having a higher porosity than the first separator layer is not arranged facing the negative electrode. Charging / discharging in Examples 1 and 2 in which the negative electrode active material layer contains an acrylic resin as a binder and the second separator layer is arranged facing the negative electrode with respect to the DC input resistance increase rate after the discharge cycle. It can be seen that the rate of increase in DC input resistance after the cycle is greatly reduced. Further, it can be seen that the DC input resistance increase rate after the charge / discharge cycle in Example 2 in which the second separator layer is arranged facing the negative electrode and the positive electrode is particularly greatly reduced.

On the other hand, in Comparative Examples 2 to 3 in which the negative electrode active material layer contains styrene-butadiene rubber as a binder, the second separator layer is arranged facing the negative electrode even if the second separator is arranged facing the negative electrode. It can be seen that the DC input resistance increase rate after the charge / discharge cycle is not sufficiently reduced as compared with Comparative Example 4 which has not been used.

As described above, it was shown that the non-aqueous electrolyte power storage element is excellent in the effect of suppressing the increase in resistance after the charge / discharge cycle.

The present invention is suitably used as a non-aqueous electrolyte power storage element such as a non-aqueous electrolyte secondary battery used as a power source for personal computers, electronic devices such as communication terminals, automobiles, and the like.

1 Non-aqueous electrolyte power storage element 2 Electrode body 3 Case 4 Positive electrode terminal 5 Negative electrode terminal 20 Power storage unit 30 Power storage device 41 Positive electrode current collector 51 Negative electrode current collector

Claims

A negative electrode having a negative electrode active material layer containing an acrylic resin, and a negative electrode
With the positive electrode
With the first separator layer,
It has a second separator layer and
The first separator layer is interposed between the negative electrode and the positive electrode,
The second separator layer is interposed between the negative electrode and the first separator layer,
A non-aqueous electrolyte power storage element having a higher porosity of the second separator layer than that of the first separator layer.
The non-aqueous electrolyte power storage element according to claim 1, wherein the first separator layer contains a synthetic resin as a main component and the second separator layer contains inorganic particles.
The non-aqueous electrolyte power storage element according to claim 2, wherein the second separator layer is further interposed between the positive electrode and the first separator layer.
The non-aqueous electrolyte power storage element according to claim 1, claim 2 or claim 3, wherein the porosity of the second separator layer is 45% by volume or more and 85% by volume or less.