JP2019200855A - Electrode assembly and power storage device - Google Patents

Abstract

To suppress plastic deformation of a collector of a negative electrode at the time of charging.SOLUTION: A negative electrode 20 comprises: a sheet-like collector 21; a negative electrode active material layer 22 that is provided on a primary face of the collector 21 and contains negative electrode active material capable of occluding and discharging lithium; and a first ceramic layer 23 that is provided on the negative electrode active material layer 22 and contains ceramic particles. A separator 30 comprises: a sheet-like base material layer 31; and a second ceramic layer 32 that is provided on a primary face of the base material layer 31 and contains ceramic particles. The first ceramic layer 23 of the negative electrode 20 is in contact with the second ceramic layer 32 of the separator 30.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an electrode assembly and a power storage device.

  Patent Document 1 discloses a technique for suppressing expansion of a negative electrode due to expansion of a negative electrode active material during charging, for a non-aqueous secondary battery such as a lithium ion battery. In the non-aqueous secondary battery of Patent Document 1, ceramic particles are contained in a separator disposed between a positive electrode and a negative electrode to enhance the structure holding performance of the separator. According to the said structure, when the expansion pressure of a negative electrode active material acts on a separator, it becomes difficult to compress a separator and the expansion | swelling of the thickness direction (lamination direction) of a negative electrode resulting from expansion | swelling of a negative electrode active material can be suppressed.

In addition, attempts have been made to use a high-capacity negative electrode active material such as a silicon-based material as a negative electrode active material constituting a negative electrode of a non-aqueous secondary battery such as a lithium ion battery. For example, Patent Document 2 discloses a negative electrode active material made of a silicon-based material obtained from CaSi ₂ through a decalcification reaction. Such a high-capacity negative electrode active material has a property of having a high expansion coefficient during charging.

JP 2009-43715 A International Publication No. 2014/080608

  By the way, the conventional negative electrode disclosed by patent document 1 etc. is from the sheet-like collector which consists of metal foil etc., and the negative electrode active material layer which is provided in the surface of a collector and contains a negative electrode active material. It is configured. For this reason, when the negative electrode active material expands during charging, the expansion pressure also acts on the current collector, and may be plastically deformed so that the current collector is stretched in the surface direction. Such plastic deformation of the current collector due to the expansion of the negative electrode active material makes it difficult to precisely control the dimensions of the negative electrode and the electrode assembly including the negative electrode, and hinders miniaturization of the electrode assembly.

  The present invention has been made in view of such circumstances, and an object thereof is to suppress plastic deformation of the current collector of the negative electrode during charging.

  An electrode assembly that solves the above problems is an electrode assembly that includes a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode. A negative electrode active material layer containing a negative electrode active material capable of inserting and extracting lithium; and a ceramic particle provided on the main surface of the current collector; A first ceramic layer, and the separator includes a sheet-like base material layer and a second ceramic layer provided on a main surface of the base material layer and containing ceramic particles, and the first electrode of the negative electrode. One ceramic layer is in contact with the second ceramic layer of the separator.

  According to the above configuration, the negative electrode active material layer is reinforced by the first ceramic layer, thereby suppressing the spread in the surface direction of the negative electrode active material layer due to the expansion of the negative electrode active material during charging. Further, even if the first ceramic layer tends to spread in the plane direction together with the negative electrode active material layer, the surface of the first ceramic layer is caused by the frictional resistance between the surface of the first ceramic layer and the surface of the second ceramic layer of the separator. Directional spread is suppressed. Further, by suppressing the spread in the surface direction of the first ceramic layer, the spread in the surface direction of the negative electrode active material layer due to the expansion of the negative electrode active material during charging is further suppressed. By suppressing the spread in the surface direction of the negative electrode active material layer due to the expansion of the negative electrode active material during charging, the current collector is prevented from being greatly plastically deformed by being pulled by the spread in the surface direction of the negative electrode active material layer. The

  In the electrode assembly, at least one of the first ceramic layer and the second ceramic layer contains at least one selected from branched ceramic particles and ceramic particles having an aspect ratio of 2 to 5. Is preferred.

  According to the said structure, the unevenness | corrugation based on the ceramic particle of a branched shape and the shape of a ceramic particle whose aspect ratio is 2-5 is formed in the surface of at least one of a 1st ceramic layer and a 2nd ceramic layer. Thereby, the frictional resistance between the surface of a 1st ceramic layer and the surface of a 2nd ceramic layer becomes large, and can suppress the plastic deformation of a collector more effectively.

  In the electrode assembly, it is preferable that the first ceramic layer contains at least one selected from branched ceramic particles and ceramic particles having an aspect ratio of 2 to 5.

  According to the said structure, a 1st ceramic layer becomes harder because the ceramic particles which comprise a 1st ceramic layer become entangled. Thereby, the reinforcement effect of the negative electrode active material layer by a 1st ceramic layer becomes large, and can suppress the plastic deformation of a collector more effectively.

  In the electrode assembly, the negative electrode active material is preferably at least one selected from a compound containing an element that can be alloyed with lithium and an element that can be alloyed with lithium. In the electrode assembly, the negative electrode active material is preferably at least one silicon-based material selected from silicon alone and a compound containing silicon.

  According to the above configuration, the use of the negative electrode active material having a large capacity and a high expansion coefficient during charging increases the force for deforming the current collector due to the expansion of the negative electrode active material. Therefore, the effect of suppressing the plastic deformation of the current collector is remarkably obtained.

  A power storage device that solves the above problems includes the electrode assembly and a non-aqueous electrolyte.

  According to the present invention, plastic deformation of the current collector of the negative electrode during charging can be suppressed.

(A), (b) is a schematic cross section of an electrode assembly. (A), (b) is explanatory drawing of a non-spherical ceramic particle. Explanatory drawing of the manufacturing method of an electrode assembly. The top view of a negative electrode.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment of the invention will be described with reference to the drawings.
As shown in FIG. 1A, the electrode assembly includes a positive electrode 10, a negative electrode 20, and a separator that is disposed between the positive electrode 10 and the negative electrode 20 and insulates the positive electrode 10 and the negative electrode 20. The laminated structure A having 30 is provided. In the laminated structure A, a plurality of positive electrodes 10 and a plurality of negative electrodes 20 are alternately arranged via separators 30. The electrode assembly further includes a restraining portion 40 that restrains the stacked structure A in the stacking direction and suppresses the expansion of the stacked structure A in the stacking direction.

  The electrode assembly is disposed in a case filled with a non-aqueous electrolyte and used as a non-aqueous power storage device (hereinafter simply referred to as “power storage device”). Examples of the power storage device include a secondary battery, an electric double layer capacitor, and a lithium ion capacitor. In addition, such power storage devices are useful as non-aqueous secondary batteries for driving motors of electric vehicles and hybrid vehicles, and non-aqueous secondary batteries used in personal computers, portable communication devices, home appliances, office equipment, industrial equipment, etc. It is.

Examples of the nonaqueous electrolytic solution include a nonaqueous electrolytic solution containing an organic solvent and an electrolyte dissolved in the organic solvent.
Examples of the organic solvent include cyclic esters, chain esters, ethers and the like. Examples of the cyclic esters include ethylene carbonate, propylene carbonate, butylene carbonate, gamma butyrolactone, vinylene carbonate, 2-methyl-gamma butyrolactone, acetyl-gamma butyrolactone, and gamma valerolactone. Examples of the chain esters include dimethyl carbonate, diethyl carbonate, dibutyl carbonate, dipropyl carbonate, ethyl methyl carbonate, propionic acid alkyl ester, malonic acid dialkyl ester, and acetic acid alkyl ester. Examples of ethers include tetrahydrofuran, 2-methyltetrahydrofuran, 1,4-dioxane, 1,2-dimethoxyethane, 1,2-diethoxyethane, and 1,2-dibutoxyethane. The nonaqueous electrolytic solution may contain only one of the above organic solvents, or may contain two or more.

Examples of the electrolyte include lithium salts such as LiClO ₄ , LiAsF ₆ , LiPF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , and LiN (FSO ₂ ) ₂ .

As the non-aqueous electrolyte solution, such as ethylene carbonate, dimethyl carbonate, ethyl methyl carbonate, propylene carbonate, in an organic solvent such as dimethyl _{carbonate, LiClO 4, LiPF 6, LiBF} 4, LiCF 3 SO 3 and lithium salts, such as 0. Examples include a solution dissolved at a concentration of about 5 mol / l to 1.7 mol / l.

Next, the positive electrode 10, the negative electrode 20, and the separator 30 which comprise an electrode assembly are demonstrated in detail.
(Positive electrode)
The positive electrode 10 is not particularly limited, and a known positive electrode used for a power storage device can be used. Examples of the positive electrode 10 include a positive electrode having a current collector and a positive electrode active material layer containing a positive electrode active material.

  The current collector refers to a chemically inert electronic high conductor that keeps a current flowing through an electrode during discharging or charging of a power storage device. As the current collector, for example, at least one selected from silver, copper, gold, aluminum, magnesium, tungsten, cobalt, zinc, nickel, iron, platinum, tin, indium, titanium, ruthenium, tantalum, chromium, molybdenum, and Examples include metal materials such as stainless steel.

The positive electrode active material, known materials including materials that lithium ions can occlude and release, for example, the general formula of the layered rock salt _{structure: Li a Ni b Co c Mn} d D e O f (0.2 ≦ a ≦ 2, b + c + d + e = 1, 0 ≦ e <1, D is W, Mo, Re, Pd, Ba, Cr, B, Sb, Sr, Pb, Ga, Al, Nb, Mg, Ta, Ti, La, Zr, Cu, At least one element selected from Ca, Ir, Hf, Rh, Fe, Ge, Zn, Ru, Sc, Sn, In, Y, Bi, S, Si, Na, K, P, V, 1.7 ≦ f A lithium composite metal oxide represented by ≦ 3), Li ₂ MnO ₃ can be selected. Further, as a positive electrode active material, a spinel structure metal oxide such as LiMn ₂ O ₄ , a solid solution composed of a mixture of a spinel structure metal oxide and a layered compound, LiMPO ₄ , LiMVO ₄ or Li ₂ MSiO ₄ (wherein M is selected from at least one of Co, Ni, Mn, and Fe). Furthermore, as the positive electrode active material, tavorite compound represented by LiMPO ₄ F, such as LiFePO ₄ F (M is a transition metal), Limbo ₃ such LiFeBO ₃ (M is a transition metal) include borate compound represented by It is done. Any metal oxide used as the positive electrode active material may have the above composition formula as a basic composition, and a metal element contained in the basic composition may be substituted with another metal element.

(Negative electrode)
As shown in FIG. 1B, the negative electrode 20 includes a sheet-like current collector 21, a negative electrode active material layer 22 provided on the main surface of the current collector 21, and a negative electrode active material layer 22. The first ceramic layer 23 is provided.

The thickness of the negative electrode 20 is, for example, 135 to 185 μm.
<Current collector>
The current collector 21 refers to a chemically inert electronic high conductor that keeps a current flowing through an electrode during discharging or charging of a power storage device. As the current collector, for example, at least one selected from silver, copper, gold, aluminum, magnesium, tungsten, cobalt, zinc, nickel, iron, platinum, tin, indium, titanium, ruthenium, tantalum, chromium, molybdenum, and Examples include metal materials such as stainless steel.

The thickness of the current collector 21 is, for example, 5 to 15 μm.
<Negative electrode active material layer>
The negative electrode active material layers 22 are respectively provided on both main surfaces of the current collector 21. The negative electrode active material layer 22 contains a negative electrode active material capable of inserting and extracting lithium, and a binder that binds the negative electrode active material to the current collector 21.

The negative electrode active material is a known substance including a material capable of inserting and extracting lithium ions, for example, a group 14 element such as carbon, germanium, and tin, a group 13 element such as aluminum and indium, and a group 12 element such as zinc and cadmium. At least one element of a group 15 element such as antimony and bismuth, an alkaline earth metal such as magnesium and calcium, and a group 11 element such as silver and gold can be selected. Examples of the alloy or compound include tin-based materials such as an Ag—Sn alloy, Cu—Sn alloy, and Co—Sn alloy, and carbon-based materials such as various graphites. Further, as the negative electrode active _{material, Nb 2 O 5, TiO 2} , Li 4 Ti 5 O 12, WO 2, MoO 2, Fe 2 O 3 oxide such, _{or, Li 3-x M x N} (M = Co , Ni, Cu). Further, as the negative electrode active material, silicon alone, silicon-based materials such as SiO _x (0.3 ≦ x ≦ 1.6) disproportionate to silicon and silicon dioxide, silicon alone or silicon-based materials and carbon black, graphite And composites in which carbon-based materials such as these are combined.

  Among these negative electrode active materials, negative electrode active materials having a large capacity and a high expansion coefficient during charging are preferable. Since the negative electrode active material having a higher expansion rate at the time of charging has a greater force to deform the current collector 21 due to the expansion of the negative electrode active material, the plasticity of the current collector 21 by the electrode assembly of this embodiment is increased. The effect of suppressing deformation is remarkably obtained.

  The negative electrode active material having a high expansion coefficient at the time of charging is preferably at least one selected from an element that can be alloyed with lithium and a compound or alloy having an element that can be alloyed with lithium. It is more preferable that the material is at least one silicon-based material selected from compounds containing.

Examples of the silicon-based material include silicon simple substance, silicon oxide-based material such as SiO _x (0.3 ≦ x ≦ 1.6) disproportionate to silicon simple substance and silicon dioxide, silicon simple substance or silicon oxide-based material and carbon. Composites combining carbon-based materials such as black and graphite, SiB ₄ , SiB ₆ , Mg ₂ Si, Ni ₂ Si, TiSi ₂ , MoSi ₂ , CoSi ₂ , NiSi ₂ , CaSi ₂ , CrSi ₂ , Cu ₅ Si _{, FeSi 2, MnSi 2, NbSi} 2, TaSi 2, VSi 2, WSi 2, ZnSi 2, SiC, Si 3 N 4, Si 2 N 2 O, include SnSiO 3, LiSiO. The silicon-based material may be coated with carbon. A silicon-based material coated with carbon is excellent in conductivity.

Further, as a silicon-based material, a silicon-based material obtained from CaSi ₂ through a decalcification reaction disclosed in Patent Document 2 can also be used. Examples of the silicon-based material include silicon obtained by decalcification (for example, heat treatment at 300 to 1000 ° C.) of layered polysilane obtained by treating CaSi ₂ with an acid (for example, hydrochloric acid or hydrogen fluoride). It is a system material.

The negative electrode active material layer 22 may contain only one of the above negative electrode active materials, or may contain two or more.
The ratio of the negative electrode active material contained in the negative electrode active material layer 22 is, for example, 75 to 95% by mass.

  The porosity of the negative electrode active material layer 22 is, for example, 20 to 40%. Since the density of the negative electrode active material in the negative electrode active material layer 22 is higher and the porosity of the negative electrode active material layer 22 is lower, the force to deform the current collector 21 due to the expansion of the negative electrode active material increases. The effect which suppresses the plastic deformation of the electrical power collector 21 by the electrode assembly of a form is acquired notably.

  The binder plays a role of connecting the negative electrode active material or the like to the surface of the current collector 21. Examples of the binder include fluorine-containing resins such as polyvinylidene fluoride, polytetrafluoroethylene, and fluorine rubber, thermoplastic resins such as polypropylene, polyethylene, and polyvinyl alcohol, imide resins such as polyimide and polyamideimide, and alkoxysilyl group-containing resins. Is mentioned. Moreover, you may employ | adopt the polymer which has a hydrophilic group as a binder. Examples of the hydrophilic group of the polymer having a hydrophilic group include a carboxyl group, a sulfo group, a silanol group, an amino group, a hydroxyl group, and a phosphate group. Examples of the polymer having a hydrophilic group include polyacrylic acid, carboxymethylcellulose, polymethacrylic acid, and poly (p-styrenesulfonic acid). The negative electrode active material layer 22 may contain only one of the above binders, or may contain two or more.

The ratio of the binder contained in the negative electrode active material layer 22 is, for example, 5 to 15% by mass.
Moreover, the negative electrode active material layer 22 may contain other components, such as a conductive support agent.
The conductive additive is added to increase the conductivity of the negative electrode 20. The conductive auxiliary agent may be a chemically inert electronic high conductor, and examples of the conductive auxiliary agent include carbon black, graphite, vapor grown carbon fiber (Vapor Grown Carbon Fiber), and carbonaceous fine particles. Examples include various metal particles. Examples of the carbon black include acetylene black, ketjen black (registered trademark), furnace black, and channel black. The negative electrode active material layer 22 may contain only one kind of the above-mentioned conductive auxiliary agent, or may contain two or more kinds.

The thickness of the negative electrode active material layer 22 is, for example, 50 to 90 μm.
<First ceramic layer>
The first ceramic layer 23 is an insulating layer having a porous structure through which the non-aqueous electrolyte can permeate, and covers the entire surface of each negative electrode active material layer 22 provided on both main surfaces of the current collector 21. Is provided. The first ceramic layer 23 contains insulating ceramic particles and a binder that binds the ceramic particles to the negative electrode active material layer 22.

  Examples of the material of the ceramic particles include metal oxides such as aluminum oxide, silicon oxide, titanium oxide, zirconium oxide, cerium oxide, and chromium oxide, metal carbides such as silicon carbide, and metal nitrides such as aluminum nitride and boron nitride. Can be mentioned. The first ceramic layer 23 may contain only one kind of ceramic particles made of the same material, or may contain two or more kinds of ceramic particles made of different materials.

  The shape of the ceramic particles is not particularly limited, but the branched shape as shown in FIG. 2A and the aspect ratio as shown in FIG. 2B (the length L1 of the long side of the circumscribed rectangle) It is preferably a non-spherical shape such as a vertically long shape having a short side length L2 of 2 to 5.

  The first ceramic layer 23 may contain only one of the branched ceramic particles and the vertically long ceramic particles, or may contain both, but the branched ceramic particles Particularly preferred are those containing ceramic particles. When non-spherical ceramic particles are contained, the ratio (number ratio) of non-spherical ceramic particles in the entire ceramic particles is preferably 80% or more.

  The particle diameter of the ceramic particles is not particularly limited, but is, for example, 5 to 10 μm. The particle diameter is the length L1 of the long side of the circumscribed rectangle, and can be obtained, for example, by image analysis of a cross-sectional photograph of the first ceramic layer 23.

  Examples of the binder include fluorine-containing resins such as polyvinylidene fluoride, polytetrafluoroethylene, and fluororubber, thermoplastic resins such as polypropylene and polyethylene, imide resins such as polyimide and polyamideimide, and alkoxysilyl group-containing resins. . Moreover, you may employ | adopt the polymer which has a hydrophilic group as a binder. Examples of the hydrophilic group of the polymer having a hydrophilic group include a carboxyl group, a sulfo group, a silanol group, an amino group, a hydroxyl group, and a phosphate group. Examples of the polymer having a hydrophilic group include polyacrylic acid, carboxymethylcellulose, polymethacrylic acid, and poly (p-styrenesulfonic acid).

The thickness of the first ceramic layer 23 is, for example, 3 to 8 μm.
The porosity of the first ceramic layer 23 is, for example, 30 to 60%.
The first ceramic layer 23 is formed by, for example, preparing a slurry by mixing ceramic particles, a binder, and a solvent, applying the slurry to the negative electrode active material layer 22, removing the solvent, and drying and curing. be able to. As the solvent, a known solvent used at the time of manufacturing the electrode of the power storage device, for example, water, N-methyl-2-pyrrolidone, methanol, or methyl isobutyl ketone can be used.

(Separator)
As shown in FIG. 1B, the separator 30 includes a sheet-like base material layer 31 and a second ceramic layer 32 provided on the main surface of the base material layer 31.

The thickness of the separator 30 is, for example, 12 to 20 μm.
<Base material layer>
As the base material layer 31, a known porous film used as a separator of a power storage device can be used. Examples of the known porous membrane include a porous membrane made of polyethylene and a porous membrane made of polypropylene.

The thickness of the base material layer 31 is, for example, 8 to 16 μm.
<Second ceramic layer>
The second ceramic layer 32 is an insulating layer having a porous structure through which the nonaqueous electrolytic solution can permeate, and is provided so as to cover the entire surface of the base material layer 31 on the negative electrode 20 side.

The second ceramic layer 32 contains ceramic particles and a binder that binds the ceramic particles to the base material layer 31.
The material, shape, and average particle diameter of the ceramic particles contained in the second ceramic layer 32 are the same as those of the ceramic particles contained in the first ceramic layer 23. Further, the material, average particle diameter, shape, and the like of the ceramic particles contained in the second ceramic layer 32 may be the same as those of the ceramic particles contained in the first ceramic layer 23, or one or more. The configuration may be different.

  As for the shape of the ceramic particles, at least one of the first ceramic layer 23 and the second ceramic layer 32 preferably contains non-spherical ceramic particles, and both the first ceramic layer 23 and the second ceramic layer 32 are included. More preferably contains non-spherical ceramic particles. When one of the first ceramic layer 23 and the second ceramic layer 32 contains non-spherical ceramic particles, the first ceramic layer 23 preferably contains non-spherical ceramic particles.

The thickness of the second ceramic layer 32 is, for example, 2 to 6 μm.
The porosity of the second ceramic layer 32 is, for example, 30 to 60%.
As shown in FIG. 3, the laminated structure A of the electrode assembly has the positive electrode 10 and the negative electrode 20 so that the first ceramic layer 23 of the negative electrode 20 and the second ceramic layer 32 of the separator 30 face each other. , And separator 30 are laminated and pressed in the laminating direction as necessary.

Next, the operation of this embodiment will be described.
In the electrode assembly of this embodiment, the first ceramic layer 23 is integrally provided on the negative electrode active material layer 22 in the negative electrode 20. According to the above configuration, the negative electrode active material layer 22 is reinforced by the first ceramic layer 23 that contains ceramic particles and is harder than the negative electrode active material layer 22. The spread of the material layer 22 in the surface direction is suppressed.

  Furthermore, in the electrode assembly of this embodiment, a second ceramic layer 32 containing ceramic particles is provided on the base material layer 31 in the separator 30. The first ceramic layer 23 of the negative electrode 20 and the second ceramic layer 32 of the separator 30 have a laminated structure arranged so as to face each other, and the first ceramic layer 23 and the second ceramic layer 32 are in contact with each other. It is in a state.

  According to the above configuration, even if the first ceramic layer 23 and the negative electrode active material layer 22 try to spread in the surface direction due to the expansion of the negative electrode active material during charging, the surface of the first ceramic layer 23 and the second ceramic of the separator 30 Due to the frictional resistance with the surface of the layer 32 (resistance due to catching of irregularities), the spread of the first ceramic layer 23 in the surface direction is suppressed. Then, by suppressing the spread in the surface direction of the first ceramic layer 23, the spread in the surface direction of the negative electrode active material layer 22 due to the expansion of the negative electrode active material during charging is further suppressed.

  In particular, when the negative electrode active material expands, the first ceramic layer 23 is strongly pressed against the second ceramic layer 32 by the negative electrode active material layer 22 attempting to expand in the thickness direction. Thereby, the frictional resistance between the surface of the first ceramic layer 23 and the surface of the second ceramic layer 32 is increased, and the effect of suppressing the spread in the surface direction of the first ceramic layer 23 is increased, and the negative electrode active material The effect of suppressing the spread in the surface direction of the layer 22 is increased.

  Thus, according to the electrode assembly of this embodiment, the spread of the negative electrode active material layer 22 in the surface direction due to the expansion of the negative electrode active material during charging is suppressed. Thereby, it is suppressed that the current collector 21 of the negative electrode 20 is greatly plastically deformed beyond the elastic limit by being pulled by the spread in the surface direction of the negative electrode active material layer 22.

Next, the effect of this embodiment will be described.
(1) The electrode assembly includes a positive electrode 10, a negative electrode 20, and a separator 30 disposed between the positive electrode 10 and the negative electrode 20. The negative electrode 20 is provided on a sheet-shaped current collector 21, a main surface of the current collector 21, a negative electrode active material layer 22 containing a negative electrode active material capable of occluding and releasing lithium, and a negative electrode active material layer 22. And a first ceramic layer 23 containing ceramic particles. The separator 30 includes a sheet-like base material layer 31 and a second ceramic layer 32 provided on the main surface of the base material layer 31 and containing ceramic particles. The first ceramic layer 23 of the negative electrode 20 and the second ceramic layer 32 of the separator 30 are in contact with each other.

  According to the above configuration, the current collector 21 of the negative electrode 20 is suppressed from being greatly plastically deformed during charging. Thereby, the change in battery performance due to the plastic deformation of the current collector 21 of the negative electrode 20 can be suppressed. In the power storage device, the case that accommodates the electrode assembly is sized so that the current collector 21 does not contact the inner surface of the case even when the current collector 21 of the negative electrode 20 is deformed during charging. Therefore, according to the above configuration, since the deformation amount of the current collector 21 of the negative electrode 20 during charging is reduced, the case can be reduced, and the power storage device can be reduced in size.

  (2) At least one of the first ceramic layer 23 and the second ceramic layer 32 contains at least one selected from branched ceramic particles and ceramic particles having an aspect ratio of 2 to 5.

  According to the above configuration, complex irregularities based on non-spherical ceramic particles are formed on at least one surface of the first ceramic layer 23 and the second ceramic layer 32. Thereby, the frictional resistance between the surface of the 1st ceramic layer 23 and the surface of the 2nd ceramic layer 32 becomes large, and the plastic deformation of the electrical power collector 21 can be suppressed more effectively.

(3) The first ceramic layer 23 contains at least one selected from branched ceramic particles and ceramic particles having an aspect ratio of 2 to 5.
According to the said structure, the 1st ceramic layer 23 becomes harder because the ceramic particles which comprise the 1st ceramic layer 23 become entangled. Thereby, the reinforcement effect of the negative electrode active material layer 22 by the 1st ceramic layer 23 becomes large, and the plastic deformation of the electrical power collector 21 can be suppressed more effectively.

  (4) The negative electrode active material is at least one selected from an element that can be alloyed with lithium and a compound containing an element that can be alloyed with lithium, and preferably at least selected from a simple substance of silicon and a compound containing silicon. It is a kind of silicon material.

  According to the above configuration, the use of the negative electrode active material having a large capacity and a high expansion coefficient during charging increases the force for deforming the current collector 21 due to the expansion of the negative electrode active material. Therefore, the effect which suppresses the plastic deformation of the electrical power collector 21 by the electrode assembly of this embodiment is acquired notably.

(5) The electrode assembly includes a restraining portion 40 that restrains the laminated structure A in which the positive electrode 10, the negative electrode 20, and the separator 30 are laminated in the laminating direction.
According to the above configuration, the first ceramic layer 23 is more strongly pressed against the second ceramic layer 32 when the negative electrode active material is expanded. Thereby, the frictional resistance between the surface of the 1st ceramic layer 23 and the surface of the 2nd ceramic layer 32 becomes still larger, and the plastic deformation of the electrical power collector 21 can be suppressed more effectively.

In addition, this embodiment can be implemented with the following modifications. The present embodiment and the following modifications can be implemented in combination with each other within a technically consistent range.
The formation range of the first ceramic layer 23 on the surface of the negative electrode active material layer 22 is not particularly limited. For example, the first ceramic layer 23 may be partially provided on a part of the surface of the negative electrode active material layer 22 in a range where the separator 30 is in contact with the second ceramic layer 32.

  O The formation range of the 2nd ceramic layer 32 in the surface of the base material layer 31 of the separator 30 is not specifically limited. For example, the second ceramic layer 32 may be partially provided on a part of the surface of the base material layer 31 in a range where the negative electrode 20 is in contact with the first ceramic layer 23.

  In the above embodiment, the first ceramic layer 23 is provided on each of the negative electrode active material layers 22 provided on both main surfaces of the current collector 21, but only on one of the negative electrode active material layers 22 The first ceramic layer 23 may be provided.

The electrode assembly may include the negative electrode 20 having the first ceramic layer 23 and the negative electrode 20 not having the first ceramic layer 23.
The electrode assembly may include the separator 30 having the second ceramic layer 32 and the separator 30 not having the second ceramic layer 32.

O The restraint part 40 may be omitted. In this case, it is preferable that the laminated structure A is constrained in the stacking direction by a configuration other than the electrode assembly (for example, the inner surface of the case of the power storage device).
Next, the technical idea that can be grasped from the above embodiment and other examples will be described below.

  (A) The first ceramic layer contains at least one selected from branched ceramic particles and ceramic particles having an aspect ratio of 2 to 5, and the second ceramic layer is branched ceramic particles. And at least one selected from ceramic particles having a shape with an aspect ratio of 2 to 5.

  (B) The negative electrode active material layer is the electrode assembly containing the negative electrode active material made of a carbon-based material and the negative electrode active material made of a silicon-based material.

Hereinafter, examples that further embody the above embodiment will be described.
An electrode assembly of an example having a first ceramic layer on a negative electrode active material layer in a negative electrode, and a comparative electrode assembly having no first ceramic layer on a negative electrode active material layer in a negative electrode are prepared. Then, the amount of deformation of the negative electrode of each electrode assembly during charging was evaluated.

<Example>
(Positive electrode)
Containing positive electrode active material (LiNi _82/100 Co _15/100 Al _3/100 O ₂ ), acetylene black, and polyvinylidene fluoride with respect to one main surface of a sheet-like current collector made of aluminum having a thickness of 12 μm A positive electrode provided with a positive electrode active material layer was used.

(Negative electrode active material)
CaSi ₂ was added to a concentrated hydrochloric acid solution at 0 ° C. under stirring conditions and reacted for 1 hour. Water was added to the reaction solution, filtration was performed, and a yellow powder was collected by filtration. The yellow powder was washed with water, further washed with ethanol, and then dried under reduced pressure to obtain a layered silicon compound containing layered polysilane. Next, the layered silicon compound was heated at 800 ° C. in an argon atmosphere to release hydrogen to produce a silicon-based material. By heating the silicon-based material at 880 ° C. in a propane gas atmosphere, a carbon-coated silicon-based material (hereinafter referred to as a silicon-based material) was manufactured.

(Negative electrode)
Both main surfaces of a sheet-like current collector made of rolled copper foil having a thickness of 10 μm contain a silicon-based material, acetylene black, and polyamideimide, and the total charge amount by the silicon-based material per 1 cm ² is 2.90 mAh. A negative electrode provided with a negative electrode active material layer was prepared.

  In addition, 89 parts by mass of ceramic particles, 4.5 parts by mass of polyvinyl alcohol, 3.0 parts by mass of modified polyvinyl alcohol (Z410), and 3.5 parts by mass of acrylic emulsion (J-537J) were suspended in ion-exchanged water. A slurry was prepared. This slurry was applied on each negative electrode active material layer, and heated at 120 ° C. for 1 minute to form a first ceramic layer having a thickness of 5 μm. As ceramic particles, branched aluminum oxide particles (AKP-3000 manufactured by Sumitomo Chemical Co., Ltd.) having a particle diameter of 0.70 μm were used.

  Here, as shown in FIG. 4, the lateral dimension L <b> 3 in the portion where the negative electrode active material layer 22 and the first ceramic layer 23 of the negative electrode 20 were provided was measured using a two-dimensional measuring machine. The measurement of the lateral dimension L3 was performed at eight different locations of the negative electrode 20, and the average value was taken as the dimension before charging of the negative electrode 20.

(Separator)
A ceramic coated separator in which a ceramic layer having a thickness of 4 μm containing ceramic particles was provided on one main surface of a 12 μm thick sheet-like base material layer made of a polyethylene porous film was used.

(Electrode assembly)
The separator is positioned between the positive electrode and the negative electrode, and the first ceramic layer of the negative electrode and the second ceramic layer of the separator face each other, so that 25 positive electrodes, 26 negative electrodes, The separator was laminated to obtain a laminated structure. An electrode assembly of an example was obtained by attaching a restraining portion that restrains the laminated structure in the laminating direction with a pressure corresponding to a fixed size of 20 kN.

<Comparative example>
As a negative electrode, silicon-based material, artificial graphite, acetylene black, and polyamideimide are contained in both main surfaces of a sheet-like current collector made of rolled copper foil having a thickness of 10 μm, and silicon-based material per 1 cm ² An electrode assembly was produced in the same manner as in the example except that the negative electrode provided with the negative electrode active material layer was used as it was so that the total amount of charge was 2.90 mAh.

<Evaluation of deformation amount of negative electrode>
A lithium ion secondary battery was obtained by housing the electrode assembly of the example or the comparative example in the case and injecting a nonaqueous electrolytic solution to seal the case. As a non-aqueous electrolyte, LiPF ₆ is dissolved in a mixed solvent in which dimethyl carbonate, ethylene carbonate, and fluoroethylene carbonate are mixed at a volume ratio of 80:10:10, and the concentration of LiPF ₆ is 2 mol / L. Was used. The obtained lithium ion secondary battery was fully charged and then discharged to SOC 0%. The electrode assembly was taken out from the lithium ion secondary battery, and the negative electrode was taken out from the electrode assembly.

  As shown in FIG. 4, the lateral dimension L <b> 4 in the portion where the negative electrode active material layer 22 and the first ceramic layer 23 of the extracted negative electrode 20 were provided was measured using a two-dimensional measuring machine. The measurement of the lateral dimension L4 was performed at eight different locations of the negative electrode 20, and the average value was taken as the post-charge dimension of the negative electrode 20. Then, the deformation amount of the negative electrode due to charging (plastic deformation amount of the current collector) was calculated using the following formula.

(Deformation amount of negative electrode) = (Dimension after charging)-(Dimension before charging)
As a result, the amount of deformation of the negative electrode in the electrode assembly of the example was about 56% of the amount of deformation of the negative electrode in the electrode assembly of the comparative example. From this result, the first ceramic layer is provided on the negative electrode active material layer of the negative electrode, and the first ceramic layer and the second ceramic layer of the separator are in contact with each other, so that It can be seen that plastic deformation of the current collector can be suppressed.

A ... laminated structure, 10 ... positive electrode, 20 ... negative electrode, 21 ... current collector, 22 ... negative electrode active material layer, 23 ... first ceramic layer, 30 ... separator, 31 ... substrate layer, 32 ... second Ceramic layer, 40 ... restraint part.

Claims (6)

An electrode assembly comprising a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode,
The negative electrode includes a sheet-like current collector, a negative electrode active material layer that is provided on a main surface of the current collector and contains a negative electrode active material capable of occluding and releasing lithium, and on the negative electrode active material layer And a first ceramic layer containing ceramic particles,
The separator includes a sheet-like base material layer, and a second ceramic layer provided on a main surface of the base material layer and containing ceramic particles,
The electrode assembly, wherein the first ceramic layer of the negative electrode and the second ceramic layer of the separator are in contact with each other.   The at least one of the first ceramic layer and the second ceramic layer contains at least one selected from branched ceramic particles and ceramic particles having an aspect ratio of 2 to 5. 2. The electrode assembly according to 1.   The electrode assembly according to claim 2, wherein the first ceramic layer contains at least one selected from branched ceramic particles and ceramic particles having an aspect ratio of 2 to 5.   The said negative electrode active material is at least 1 type chosen from the compound containing an element which can be alloyed with lithium, and an element which can be alloyed with lithium, The negative electrode active material as described in any one of Claims 1-3 characterized by the above-mentioned. Electrode assembly.   The electrode assembly according to claim 4, wherein the negative electrode active material is at least one silicon-based material selected from silicon alone and a compound containing silicon. A power storage device comprising the electrode assembly according to any one of claims 1 to 5 and a nonaqueous electrolytic solution.