JP2021077641A - Power storage element - Google Patents

Abstract

To provide a power storage element capable of suppressing the dissolution of fine copper powder even when the fine copper powder is mixed between a positive electrode and a negative electrode.SOLUTION: A power storage element includes a positive electrode 11 having a conductive positive electrode base material 13, a positive electrode active material layer 14, and an insulating layer 15, a negative electrode 12 that is arranged so as to face the positive electrode and having a conductive negative electrode base material 16 and a negative electrode active material layer 17, and a separator 18 arranged between the positive electrode and the negative electrode, and in a region in which the positive electrode faces the negative electrode, the insulating layer covers a laminated structure including the positive electrode base material and the positive electrode active material layer, and the potential of the surface of the insulating layer is lower than 3.4 V vs. Li/Li+.SELECTED DRAWING: Figure 1

Description

The present invention relates to a power storage element.

Secondary batteries typified by lithium-ion secondary batteries are widely used in electronic devices such as personal computers and communication terminals, automobiles, etc. due to their high energy density. The secondary battery generally has a pair of electrodes composed of a sheet-shaped positive electrode and a negative electrode, and an electrolyte interposed between the electrodes, and charges and discharges by transferring ions between the electrodes. Is configured. In addition, capacitors such as lithium ion capacitors and electric double layer capacitors are also widely used as power storage elements other than secondary batteries.

The pair of electrodes usually form an electrode body laminated or wound via a separator. As the separator, a resin-made porous membrane is widely used. A storage device including such a separator and an electrode having a porous insulating layer formed on the surface of a mixture layer (active material layer) has been proposed. Patent Document 1 describes a secondary battery in which a positive electrode and a negative electrode are wound with a separator interposed therebetween, and the positive electrode and the negative electrode are a metal foil and a mixture layer formed on the metal foil, respectively. The secondary battery is described in that the secondary battery has a foil exposed portion in which the metal foil is exposed on one side in the width direction, and the positive electrode or the negative electrode has an insulating layer covering the mixture layer. Has been done.

International Publication No. 2017/130821

In the power storage element, a copper member may be used as a negative electrode base material, other conductive member, a container, or the like. Therefore, in the manufacturing process of the power storage element, for example, fine copper powder generated at the time of cutting or joining the negative electrode base material made of copper may be mixed in the power storage element. When the mixed fine copper powder comes into contact with the positive electrode due to interposition between the positive electrode and the negative electrode, etc., it is oxidized by being exposed to the high potential of the positive electrode during charging, and is dissolved in the electrolyte as copper ions to store electricity. It may affect the performance.

The present invention has been made based on the above circumstances, and an object of the present invention is to use the fine copper powder even when the fine copper powder is mixed between the positive electrode and the negative electrode. The present invention is to provide a power storage element capable of suppressing dissolution.

One aspect of the present invention includes a positive electrode having a conductive positive electrode base material, a positive electrode active material layer and an insulating layer, and a negative electrode arranged facing the positive electrode and having a conductive negative electrode base material and a negative electrode active material layer. In the region of the positive electrode facing the negative electrode, the insulating layer covers a laminated structure including the positive electrode base material and the positive electrode active material layer. The potential on the surface of the insulating layer is 3.4 V vs. It is a power storage element that is lower than Li / Li ^+.

The power storage element according to one aspect of the present invention and the power storage element according to the other aspect can dissolve the fine copper powder even when the fine copper powder is mixed between the positive electrode and the negative electrode. It can be suppressed.

FIG. 1 is a schematic cross-sectional view of a secondary battery according to an embodiment of the present invention. FIG. 2 is an explanatory diagram showing the relationship between the structure of the conventional power storage element and the electric potential. FIG. 3 is an explanatory diagram showing the relationship between the structure of the power storage element and the electric potential. FIG. 4 is an explanatory diagram showing the relationship between the structure and the electric potential of the power storage element according to one aspect of the present invention. FIG. 5 is an explanatory diagram showing the relationship between the structure and the electric potential of the power storage element according to one aspect of the present invention. FIG. 6 is an explanatory diagram showing the relationship between the structure of the power storage element and the electric potential. FIG. 7 is an external perspective view showing an embodiment of the power storage element. FIG. 8 is a schematic view showing an embodiment of a power storage device in which a plurality of power storage elements are assembled.

First, the outline of the power storage element disclosed by the present specification will be described.

The power storage element (A) according to one aspect of the present invention is arranged with a positive electrode having a conductive positive electrode base material, a positive electrode active material layer and an insulating layer facing the positive electrode, and a conductive negative electrode base material and a negative electrode. A negative electrode having an active material layer and a separator arranged between the positive electrode and the negative electrode are provided, and in a region of the positive electrode where the negative electrode faces, the insulating layer is the positive electrode base material and the positive electrode active material. It covers a laminated structure including layers, and the potential on the surface of the insulating layer is 3.4 V vs. It is a power storage element that is lower than Li / Li ^+.

According to such a power storage element (A), even when the fine copper powder is mixed between the positive electrode and the negative electrode, it is possible to suppress the dissolution of the fine copper powder. The reason for this effect is not clear, but the following reasons are presumed. The redox potential of copper is about 3.38 V vs. Since it is Li / Li ⁺ , in solid copper, it is usually 3.4 V vs. It oxidizes at a potential of Li / Li ⁺ or higher and dissolves in the electrolyte as copper ions. Therefore, the surface of the positive electrode is, for example, 3.4 V vs. When the potential is Li / Li ⁺ or higher, the fine copper powder adhering to the surface of the positive electrode can be dissolved. FIG. 2 shows a conventional power storage element 20 in which a positive electrode 23 having a positive electrode active material layer 21 and an insulating layer 22, a separator 26, and a negative electrode 25 having a negative electrode active material layer 24 are laminated in this order. Further, FIG. 2 schematically shows the potentials from the positive electrode active material layer 21 to the negative electrode active material layer 24 in the charged state of the conventional power storage element 20. Here, in FIG. 2, as an example, it is assumed that a general lithium transition metal composite oxide is used as the positive electrode active material and general graphite is used as the negative electrode active material, and the potential of the positive electrode active material layer 21 in the charged state is set. 4.3V vs. Li / Li ⁺ , the potential of the negative electrode active material layer 24 was 0.1 V vs. It is Li / Li ⁺ . Generally, the separator 26 is made of resin, and its volume resistivity is generally higher than that of the insulating layer 22 containing inorganic particles as a main component. Also, in terms of thickness, the general separator is thicker than the general insulating layer laminated on the surface of the active material layer. Therefore, the potential drop due to the insulating layer 22 is very small as compared with the potential drop due to the separator 26, and the potential on the surface of the insulating layer 22, that is, the surface of the positive electrode 23 is almost the same as the potential on the surface of the positive electrode active material layer 21. Therefore, in the charged state, the potential on the surface of the insulating layer 22 is 3.4 V vs. the melting potential of copper. It tends to be Li / Li ⁺ or higher, and the fine copper powder A existing on the surface of the insulating layer 22 (the surface of the positive electrode 23) is easily dissolved. When the positive electrode does not have an insulating layer and is laminated on the negative electrode via a separator, the potential on the surface of the positive electrode is the potential on the surface of the active material layer of the positive electrode, so that fine copper powder is more likely to dissolve. Become. Further, regardless of the material and thickness of the insulating layer and the separator, in the power storage element having the configuration shown in FIG. 2, the potential on the surface of the positive electrode (insulating layer) during charging is higher than the potential of the negative electrode active material layer. , The possibility of melting copper is high.

On the other hand, in the power storage element (A), the insulating layer covers the laminated structure including the positive electrode base material and the positive electrode active material layer in the region of the positive electrode facing the negative electrode, and the surface of the insulating layer. The potential is 3.4 V vs. Lower than Li / Li ^+. Therefore, the copper powder mixed between the positive electrode and the negative electrode may come into contact with the insulating layer, but is difficult to come into contact with the positive electrode base material and the positive electrode active material layer having a high potential. Since the potential on the surface of the insulating layer is lower than the dissolution potential of copper, the dissolution of the fine copper powder existing on the positive electrode surface, that is, the surface of the insulating layer is suppressed.

The term "conductive" means that the volume resistivity is measured according to JIS-H-0505 (1975 years) is not more than 10 ⁷ Ω · cm. "Insulating layer" means a layer having an insulating property, that is, a property of insulating electricity. The "insulating (non-conductive)" means that the volume resistivity is 10 ⁷ Ω · cm greater.

"The potential on the surface of the insulating layer ^{is lower than 3.4 V vs. Li /} Li +" means that the power storage element is insulated in all states from the discharged state to the charged state (SOC 0% to 100%) during normal use. The potential on the surface of the layer is 3.4 V vs. It means that it is lower than Li / Li ^+.

The potential on the surface of the insulating layer was set to 3.4 V vs. It can be made lower than Li / Li ⁺ by adjusting the volume resistivity and thickness of the insulating layer and the volume resistivity and thickness of the separator.
FIG. 3 shows a power storage element 30 in which a positive electrode 23 having a positive electrode active material layer 21 and an insulating layer 22, a separator 26, and a negative electrode 25 having a negative electrode active material layer 24 are laminated in this order. Further, FIG. 3 schematically shows the potentials from the positive electrode active material layer 21 to the negative electrode active material layer 24 in the charged state of the power storage element 30. In the figure, α (vs. Li ^/ Li +) is the potential of the positive electrode active material layer 21, β (vs. Li ^/ Li +) is the potential of the negative electrode active material layer 24, and γ (vs. Li ^/ Li +) is the positive electrode. The potential on the surface of the 23 (potential on the surface of the insulating layer 22), Δa (V) is the potential difference between the positive electrode active material layer 21 and the surface of the positive electrode 23 (that is, the potential drop due to the insulating layer 22), and Δb (V) is the surface of the positive electrode 23. The potential difference between the negative electrode active material layer 24 and the negative electrode active material layer 24 (that is, the potential drop due to the separator 26) is shown.
In the power storage element 30, the potential drop Δa (V) due to the insulating layer 22, the potential drop Δb (V) due to the separator 26, and the resistance A (Ωcm) per unit area of the insulating layer 22 in the region where the insulating layer 22 and the separator 26 face each other. ^{-2 ) and the resistance B (Ωcm -2} ) per unit area of the separator 26 in the region where the insulating layer 22 and the separator 26 face each other are set to Δa: Δb = A: B (that is, A / Δa = B / Δb). ) Holds. The resistance per unit area of the insulating layer 22 and the separator 26 is calculated by the volume resistivity and the thickness of each.
Therefore, Δa and Δb are adjusted by adjusting the volume resistivity and thickness of the insulating layer and the volume resistivity and thickness of the separator, and the potential of the surface of the insulating layer is 3.4 V vs. It can be lower than Li / Li ^+.

In the power storage element (A), it is preferable that the average thickness of the insulating layer in the region of the positive electrode facing the negative electrode is larger than the thickness of the separator.

According to such a power storage element (A), since the average thickness of the insulating layer is larger than the thickness of the separator, the dissolution of fine copper powder can be more sufficiently suppressed. FIG. 4 schematically shows such a power storage element 30 and the potentials from the positive electrode active material layer 21 to the negative electrode active material layer 24 in the charged state of the power storage element 30. The potential of the positive electrode active material layer 21 and the potential of the negative electrode active material layer 24 (positive electrode active material and negative electrode active material) of the power storage element 30 of FIG. 4 are the same as those of the power storage element 20 of FIG.

In the power storage element (A), it is preferable that the resistivity of the insulating layer is larger than the resistivity of the separator.

According to such a power storage element (A), since the resistivity of the insulating layer is larger than the resistivity of the separator, the dissolution of fine copper powder can be more sufficiently suppressed. FIG. 5 schematically shows such a power storage element 30 and the potentials from the positive electrode active material layer 21 to the negative electrode active material layer 24 in the charged state of the power storage element 30. The potential of the positive electrode active material layer 21 and the potential of the negative electrode active material layer 24 (positive electrode active material and negative electrode active material) of the power storage element 30 of FIG. 5 are the same as those of the power storage element 20 of FIG.

The power storage element (B) includes a positive electrode having a conductive positive electrode base material, a positive electrode active material layer and an insulating layer, and a negative electrode arranged facing the positive electrode and having a conductive negative electrode base material and a negative electrode active material layer. In the region of the positive electrode facing the negative electrode, the insulating layer covers a laminated structure including the positive electrode base material and the positive electrode active material layer, and the surface potential of the insulating layer is 3.4 V. vs. It is a power storage element that is lower than Li / Li ^+.

According to such a power storage element (B), even when the fine copper powder is mixed between the positive electrode and the negative electrode, it is possible to suppress the dissolution of the fine copper powder. The reason for this effect is not clear, but the following reasons are presumed. The redox potential of copper is about 3.38 V vs. Since it is Li / Li ⁺ , in solid copper, it is usually 3.4 V vs. It oxidizes at a potential of Li / Li ⁺ or higher and dissolves in the electrolyte as copper ions. Therefore, the surface of the positive electrode is, for example, 3.4 V vs. When the potential is Li / Li ⁺ or higher, the fine copper powder adhering to the surface of the positive electrode can be dissolved. On the other hand, in the power storage element (B), the insulating layer covers the laminated structure including the positive electrode base material and the positive electrode active material layer in the region of the positive electrode facing the negative electrode, and the surface of the insulating layer. The potential is 3.4 V vs. Lower than Li / Li ^+. Therefore, the copper powder mixed between the positive electrode and the negative electrode may come into contact with the insulating layer, but is difficult to come into contact with the positive electrode base material and the positive electrode active material layer having a high potential. Since the potential on the surface of the insulating layer is lower than the dissolution potential of copper, the dissolution of the fine copper powder existing on the positive electrode surface, that is, the surface of the insulating layer is suppressed.

The power storage element (C) includes a positive electrode having a conductive positive electrode base material, a positive electrode active material layer and an insulating layer, and a negative electrode arranged facing the positive electrode and having a conductive negative electrode base material and a negative electrode active material layer. In the region of the positive electrode facing the negative electrode, the insulating layer covers a laminated structure including the positive electrode base material and the positive electrode active material layer, and the surface of the insulating layer is on the surface of the negative electrode. It is a power storage element that is in direct contact.

According to such a power storage element (C), even when the fine copper powder is mixed between the positive electrode and the negative electrode, it is possible to suppress the dissolution of the fine copper powder. The reason for this effect is not clear, but the following reasons are presumed. FIG. 2 shows a conventional power storage element 20 in which a positive electrode 23 having a positive electrode active material layer 21 and an insulating layer 22, a separator 26, and a negative electrode 25 having a negative electrode active material layer 24 are laminated in this order. Further, FIG. 2 schematically shows the potentials from the positive electrode active material layer 21 to the negative electrode active material layer 24 in the charged state of the conventional power storage element 20. Here, in FIG. 2, as an example, it is assumed that a general lithium transition metal composite oxide is used as the positive electrode active material and general graphite is used as the negative electrode active material, and the potential of the positive electrode active material layer 21 in the charged state is set. 4.3V vs. Li / Li ⁺ , the potential of the negative electrode active material layer 24 was 0.1 V vs. It is Li / Li ⁺ . Generally, the separator 26 is made of resin, and its volume resistivity is generally higher than that of the insulating layer 22 containing inorganic particles as a main component. Also, in terms of thickness, the general separator is thicker than the general insulating layer laminated on the surface of the active material layer. Therefore, the potential drop due to the insulating layer 22 is very small as compared with the potential drop due to the separator 26, and the potential on the surface of the insulating layer 22, that is, the surface of the positive electrode 23 is almost the same as the potential on the surface of the positive electrode active material layer 21. Therefore, in the charged state, the potential on the surface of the insulating layer 22 is 3.4 V vs. the melting potential of copper. It tends to be Li / Li ⁺ or higher, and the fine copper powder A existing on the surface of the insulating layer 22 (the surface of the positive electrode 23) is easily dissolved. When the positive electrode does not have an insulating layer and is laminated on the negative electrode via a separator, the potential on the surface of the positive electrode is the potential on the surface of the active material layer of the positive electrode, so that fine copper powder is more likely to dissolve. Become. Further, regardless of the material and thickness of the insulating layer and the separator, in the power storage element having the configuration shown in FIG. 2, the potential on the surface of the positive electrode (insulating layer) during charging is higher than the potential of the negative electrode active material layer. , The possibility of melting copper is high.

On the other hand, FIG. 6 shows a power storage element 30 in which a positive electrode 23 having a positive electrode active material layer 21 and an insulating layer 22 and a negative electrode 25 having a negative electrode active material layer 24 are laminated in this order. Further, FIG. 6 schematically shows the potentials from the positive electrode active material layer 21 to the negative electrode active material layer 24 in the charged state of the power storage element 30. The potential of the positive electrode active material layer 21 and the potential of the negative electrode active material layer 24 (positive electrode active material and negative electrode active material) of the power storage element 30 of FIG. 6 are the same as those of the power storage element 20 of FIG. As described above, in the power storage element 30, the surface of the insulating layer 22 is in contact with the surface of the negative electrode 25. Therefore, the potential on the surface of the insulating layer 22, that is, the surface of the positive electrode 23 is the same as the potential on the surface of the negative electrode 25, that is, in the form of FIG. 6, 0.1 V vs. It is Li / Li ⁺ . Therefore, the fine copper powder A existing on the surface of the insulating layer 22 (the surface of the positive electrode 23) is difficult to dissolve. Further, in the power storage element (C), since the insulating layer covers the laminated structure including the positive electrode base material and the positive electrode active material layer in the region of the positive electrode facing the negative electrode, it is mixed between the positive electrode and the negative electrode. The fine powder of copper is hard to come into contact with the positive electrode base material and the positive electrode active material layer having a high potential. Therefore, in the power storage element (C), even when the fine copper powder is mixed between the positive electrode and the negative electrode, it is possible to suppress the dissolution of the fine copper powder.

In the power storage element (C), the potential on the surface of the insulating layer is 3.4 V vs. It is preferably lower than Li / Li ^+.

According to such a power storage element (C), since the potential on the surface of the insulating layer is lower than the dissolution potential of copper, the dissolution of fine copper powder can be more sufficiently suppressed.

In the power storage element (C), it is preferable that the surface of the insulating layer is in direct contact with the surface of the negative electrode active material layer.

According to such a power storage element (C), the potential on the surface of the insulating layer becomes the potential of the negative electrode active material layer, and the potential on the surface of the insulating layer can be sufficiently low. It can be sufficiently suppressed.

In the power storage element (A), the power storage element (B), and the power storage element (C), it is preferable that the insulating layer contains insulating particles.

When the insulating layer contains insulating particles, the insulating layer can exhibit good insulating properties.

In the power storage element (A), the power storage element (B), and the power storage element (C), it is preferable that the insulating layer contains inorganic particles.

When the insulating layer contains insulating particles, the insulating layer can exhibit good heat resistance.

In the power storage element (A), the power storage element (B), and the power storage element (C), it is preferable that the negative electrode base material contains copper.

Since the negative electrode base material contains copper having excellent conductivity, the current collecting performance of the negative electrode base material can be improved. Further, when the negative electrode base material contains copper, the risk of fine copper powder being mixed into the power storage element in the manufacturing process or the like increases. Therefore, when the negative electrode base material contains copper, the advantages of the present invention can be enjoyed more effectively.

The power storage element, the power storage device, the method for manufacturing the power storage element, and other embodiments according to the embodiment of the present invention will be described in detail. The name of each component (each component) used in each embodiment may be different from the name of each component (each component) used in the background technology.

<Power storage element>
The power storage element according to an embodiment of the present invention includes an electrode body having a positive electrode, a negative electrode, and a separator, a non-aqueous electrolyte, and a container for accommodating the electrode body and the non-aqueous electrolyte. The electrode body is usually a laminated type in which a plurality of positive electrodes and a plurality of negative electrodes are laminated via a separator, or a wound type in which a positive electrode and a negative electrode are laminated via a separator. The non-aqueous electrolyte exists in a state of being contained in the positive electrode, the negative electrode and the separator. Hereinafter, as an example of the power storage element, the configuration of a non-aqueous electrolyte secondary battery (hereinafter, also simply referred to as “secondary battery”) will be described.

FIG. 1 shows a schematic cross-sectional view of the secondary battery 10 according to the embodiment of the present invention. The secondary battery 10 of FIG. 1 includes a positive electrode 11, a negative electrode 12, and a separator 18. In the secondary battery 10 of FIG. 1, the description of the configurations (non-aqueous electrolyte, container, etc.) other than the positive electrode 11 and the negative electrode 12 is omitted. At least a part of the positive electrode 11 and the negative electrode 12 is arranged so as to face each other via the separator 18.

The positive electrode 11 has a positive electrode base material 13, a positive electrode active material layer 14, and an insulating layer 15. The positive electrode base material 13 is a conductive film-like or plate-like base material. The positive electrode active material layer 14 is laminated on both sides of the positive electrode base material 13 (upper and lower surfaces in FIG. 1), leaving the uncoated portion P. The uncoated portion P is one end (right side in FIG. 1) of the positive electrode base material 13. In other words, the positive electrode active material layer 14 is laminated on both sides of the positive electrode base material 13 in the region X of the positive electrode 11 where the negative electrode 12 faces. The region X of the positive electrode 11 facing the negative electrode 12 may be a region in which the positive electrode 11 substantially overlaps the negative electrode 12 in the thickness direction view of the positive electrode (vertical view in FIG. 1). The region X is a region other than the uncovered portion P. The uncoated portion P is a portion electrically connected to a positive electrode terminal or the like (not shown).

In the region X of the positive electrode 11 where the negative electrode 12 faces, the insulating layer 15 covers the laminated structure Y including the positive electrode base material 13 and the positive electrode active material layer 14. In the present embodiment, the laminated structure Y including the positive electrode base material 13 and the positive electrode active material layer 14 is composed of three layers composed of the positive electrode base material 13 and the positive electrode active material layers 14 laminated on both surfaces of the positive electrode base material 13. It is a structure. In the present embodiment, the portion of the three-layer structure (laminated structure Y) composed of the positive electrode base material 13 and the two positive electrode active material layers 14 is the region of the positive electrode facing the negative electrode 12. The laminated structure Y is covered with the insulating layer 15 including the side surface. That is, the left end face of the positive electrode base material 13 in FIG. 1 is also covered with the insulating layer 15, and the left end face and the right end face of the positive electrode active material layer 14 in FIG. 1 are also covered with the insulating layer 15. .. As described above, the insulating layer 15 is the outermost layer in the region X of the positive electrode 11 where the negative electrode 12 faces. In other words, the positive electrode base material 13 and the positive electrode active material layer 14 are not exposed in the region X of the positive electrode 11 where the negative electrode 12 faces. Furthermore, all surfaces of the positive electrode base material 13 are not exposed except for the uncoated portion P which does not face the negative electrode 12. Further, all the surfaces of the positive electrode active material layer 14 are not exposed.

In another embodiment of the present invention, an insulating layer may be provided in a region of the positive electrode where the negative electrode does not face. Further, the positive electrode active material layer may be provided in the region of the positive electrode where the negative electrode does not face, and the positive electrode active material layer provided in the region of the positive electrode where the negative electrode does not face is covered with an insulating layer. It may be present, and it may not be covered with an insulating layer.

The negative electrode 12 has a negative electrode base material 16 and a negative electrode active material layer 17. The negative electrode base material 16 is a conductive film-like or plate-like base material. The negative electrode active material layer 17 is laminated on both surfaces of the negative electrode base material 16 (upper and lower surfaces in FIG. 1), leaving an uncoated portion Q. The uncoated portion Q is an end portion of the negative electrode base material 16 (on the left side in FIG. 1) and is a region not facing the positive electrode 11. In other words, the negative electrode active material layer 17 is laminated on both sides of the negative electrode base material 16 in the region of the negative electrode 12 where the positive electrode 11 faces. The uncoated portion Q is a portion electrically connected to a negative electrode terminal or the like (not shown).

The potential on the surface of the insulating layer 15 of the secondary battery 10 in one embodiment of the present invention is 3.4 V vs. Lower than Li / Li ^+. The potential on the surface of the insulating layer 15 is 3 V vs. It is preferably lower than Li / Li ^{+, 2.5 V vs.} More preferably lower than Li / Li ^+. The potential on the surface of the insulating layer 15 is 0 V vs. It may be Li / Li ^{+ or more.}

Hereinafter, each component and the like of the secondary battery according to the embodiment of the power storage element of the present invention will be described in detail.

(Positive electrode)
The positive electrode has a positive electrode base material, a positive electrode active material layer arranged directly on the positive electrode base material or via an intermediate layer, and an insulating layer.

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 or an aluminum alloy is preferable from the viewpoint of potential resistance, high conductivity, and cost. Examples of the positive electrode base material include foils and vapor-deposited films, and foils are 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 and A3003 specified in JIS-H-4000 (2014).

The average thickness of the positive electrode base material 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 within 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. The "average thickness" means a value obtained by dividing the punching mass when punching a base material having a predetermined area by the true density of the base material and the punching area. The "average thickness" of the negative electrode substrate is also defined.

The intermediate layer is a layer arranged between the positive electrode base material and the positive electrode active material layer. The intermediate layer contains conductive particles such as carbon particles to reduce the contact resistance between the positive electrode base material and the positive electrode active material layer. The composition of the intermediate layer is not particularly limited, and includes, for example, a resin binder and conductive particles.

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

The positive electrode active material can be appropriately selected from known positive electrode active materials. As the positive electrode active material for a lithium ion secondary battery, a material capable of occluding and releasing lithium ions is usually used. As the positive electrode active material, the potential in the charged state (SOC 100%) is 3.4 V vs. Li / Li ⁺ or higher, and 4.0V vs. Those having Li / Li ⁺ or more are preferable from the viewpoint of increasing energy density and the like. 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 oxide having a spinel type crystal structure, a polyanion 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 _{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 (0 ≦ x <0.5, 0 <γ, Examples thereof include 0 <β, 0.5 <γ + β <1). Examples of the lithium transition metal oxide having a spinel-type crystal structure include Li _x Mn ₂ O ₄ , Li _x Ni _γ Mn _2-γ O _{4, and the} like. Examples of the polyanion 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. The surface of these materials may be coated with other materials. In the positive electrode active material layer, one of these materials may be used alone, or two or more of these materials may be mixed and used.

The positive electrode active material is usually particles (powder). The average particle size of the positive electrode active material is preferably 0.1 μm or more and 20 μm or less, for example. By setting the average particle size of the positive electrode active material to the above lower limit or more, the production or handling of the positive electrode active material becomes easy. By setting the average particle size of the positive electrode active material to the above upper limit or less, the electron conductivity of the positive electrode active material layer is improved. When a complex of a positive electrode active material and another material is used, the average particle size of the complex is taken as the average particle size of the positive electrode active material. The "average particle size" is based on JIS-Z-8825 (2013), and is based on the particle size distribution measured by the laser diffraction / scattering method for a diluted solution obtained by diluting the particles with a solvent. -2 (2001) means a value at which the volume-based integrated distribution calculated in accordance with (2001) is 50%.

A crusher, a classifier, or the like is used to obtain a powder having a predetermined particle size. Examples of the crushing method include a method using a mortar, a ball mill, a sand mill, a vibrating ball mill, a planetary ball mill, a jet mill, a counter jet mill, a swirling airflow type jet mill, a sieve, or the like. At the time of pulverization, wet pulverization in which water or an organic solvent such as hexane coexists can also be used. As a classification method, a sieve, a wind power classifier, or the like is used as needed for both dry and wet types.

The content of the positive electrode active material in the positive electrode active material layer is preferably 50% by mass or more and 99% by mass or less, more preferably 70% by mass or more and 98% by mass or less, and further preferably 80% by mass or more and 95% by mass or less. By setting the content of the positive electrode active material within the above range, it is possible to achieve both high energy density and manufacturability of the positive electrode active material layer.

The conductive agent is not particularly limited as long as it is a conductive material. Examples of such a conductive agent include carbonaceous materials, metals, conductive ceramics and the like. Examples of the carbonaceous material include graphitized carbon, non-graphitized carbon, graphene-based carbon and the like. Examples of non-graphitized carbon 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 carbon include graphene, carbon nanotubes (CNT), and fullerenes. 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 these materials may be mixed and used. Further, these materials may be used in combination. For example, a material in which carbon black and CNT are composited may be used. Among these, carbon black is preferable from the viewpoint of electron conductivity and coatability, and acetylene black is particularly preferable.

The content of the conductive agent in the positive electrode active material layer is preferably 1% by mass or more and 10% by mass or less, and more preferably 3% by mass or more and 9% by mass or less. By setting the content of the conductive agent in the above range, the energy density of the secondary battery can be increased.

Examples of the binder include fluororesins (polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), etc.), thermoplastic resins such as polyethylene, polypropylene, polyacrylic, and polyimide; ethylene-propylene-diene rubber (EPDM), sulfone. Elastomers such as chemicalized EPDM, styrene-butadiene rubber (SBR), fluororubber; and thermoplastic polymers can be mentioned.

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

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

The filler is not particularly limited. Fillers include polyolefins such as polypropylene and polyethylene, silicon dioxide, aluminum oxide, titanium dioxide, calcium oxide, strontium oxide, barium oxide, magnesium oxide, inorganic oxides such as aluminosilicate, magnesium hydroxide, calcium hydroxide, and water. Hydroxides such as aluminum oxide, carbonates such as calcium carbonate, sparingly soluble ionic crystals such as calcium fluoride, barium fluoride, barium sulfate, nitrides such as aluminum nitride and silicon nitride, talc, montmorillonite, boehmite and zeolite. , Apatite, kaolin, mulite, spinel, olivine, sericite, bentonite, mica and other mineral resource-derived substances, or man-made products thereof.

The positive 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 of Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Mo, Zr, Nb, W and other transition metal elements are used as positive electrode active materials, conductive agents, binders, thickeners, fillers. It may be contained as a component other than.

(Insulation layer)
The insulating layer covers a laminated structure including a positive electrode base material and a positive electrode active material layer in a region of the positive electrode facing the negative electrode. The insulating layer is usually porous.

The insulating layer usually contains particles and a binder.

The particles are preferably insulating particles. Insulating particles include oxides such as iron oxide, silicon oxide, aluminum oxide, titanium oxide, barium titanate, zirconium oxide, calcium oxide, strontium oxide, barium oxide, magnesium oxide, and aluminosilicate; magnesium hydroxide, Hydroxides such as calcium hydroxide and aluminum hydroxide; nitrides such as aluminum nitride and silicon nitride; carbonates such as calcium carbonate; sulfates such as barium sulfate; sparingly soluble ions such as calcium fluoride and barium fluoride Crystals: Mineral resource-derived substances such as talc, montmorillonite, boehmite, zeolite, apatite, kaolin, mulite, spinel, olivine, cericite, bentonite, mica, or particles such as man-made products thereof. In addition, the insulating particles may be resin particles.

The particles are also preferably inorganic particles. Examples of the inorganic particles include the above-mentioned oxides, hydroxides, nitrides, carbonates, sulfates, flame-retardant ionic crystals, mineral resource-derived substances, and particles such as artificial products thereof.

As the particles, insulating inorganic particles are more preferable, and silicon oxide, aluminum oxide, and aluminosilicate are further preferable.

The content of the particles in the insulating layer is preferably 50% by mass or more and 99% by mass or less, more preferably 60% by mass or more and 98% by mass or less, and further preferably 65% by mass or more and 97% by mass or less. By setting the content of the particles in the above range, sufficient insulating properties can be exhibited.

As the binder of the insulating layer, those exemplified as the binder of the positive electrode active material layer can be used. The binder content in the insulating layer is preferably 1% by mass or more and 50% by mass or less, more preferably 2% by mass or more and 40% by mass or less, and further preferably 3% by mass or more and 35% by mass or less. By setting the binder content in the above range, the particles can be stably retained while maintaining a good porous state.

The average thickness of the insulating layer is preferably larger than the thickness of the separator. Thereby, the dissolution of the fine copper powder can be suppressed more sufficiently.
The average thickness of the insulating layer is preferably 3 μm or more and 50 μm or less, and more preferably 6 μm or more and 30 μm or less. By setting the average thickness of the insulating layer within the above range, it is possible to achieve both sufficient insulation and thinning. Further, by providing the insulating layer with an appropriate thickness, it is possible to sufficiently reduce the amount of mixed copper fine powder reaching the surface of the positive electrode active material layer. The "average thickness of the insulating layer" is an average value of any three locations when the cross section is observed with an electron microscope image.

The resistivity of the insulating layer is preferably larger than the resistivity of the separator. Thereby, the dissolution of the fine copper powder can be suppressed more sufficiently.
As the resistance of the insulating layer, 1 × 10 13 Ωcm ² or more is preferable, and 1 × 10 14 Ωcm ² or more is more preferable. Sufficient insulating properties can be obtained by setting the resistance of the insulating layer to be equal to or higher than the above lower limit. The larger the resistance of the insulating layer, the more preferable it is, and there is no particular upper limit, but for example, it may be 1 × 10 16 Ωcm ² or less.
The term "resistance" refers to the product of the DC resistance value when the measurement target is sandwiched between metal plates by the area of the area where the DC resistance value is measured. The same is defined when "resistivity" is used for other members and the like.

(Separator)
The separator can be appropriately selected from known separators. As the separator, for example, a separator composed of only a base material layer, a separator in which a heat-resistant layer containing heat-resistant particles and a binder is formed on one surface or both surfaces of the base material layer can be used. Examples of the shape of the base material layer of the separator include a woven fabric, a non-woven fabric, and a porous resin film. Among these shapes, a porous resin film is preferable from the viewpoint of strength, and a non-woven fabric is preferable from the viewpoint of liquid retention of a non-aqueous electrolyte. As the material of the base material layer of the separator, polyolefins such as polyethylene and polypropylene are preferable from the viewpoint of shutdown function, and polyimide and aramid are preferable from the viewpoint of oxidative decomposition resistance. As the base material layer of the separator, a material in which these resins are composited may be used.

The heat-resistant particles contained in the heat-resistant layer preferably have a mass reduction of 5% or less when the temperature is raised from room temperature to 500 ° C. in an air atmosphere of 1 atm, and the mass reduction when the temperature is raised from room temperature to 800 ° C. Is more preferably 5% or less. Inorganic compounds can be mentioned as materials whose mass reduction is less than or equal to a predetermined value. Examples of inorganic compounds include oxides such as iron oxide, silicon oxide, aluminum oxide, titanium oxide, barium titanate, zirconium oxide, calcium oxide, strontium oxide, barium oxide, magnesium oxide and aluminosilicate; aluminum nitride and silicon nitride. Nitridees such as; carbonates such as calcium carbonate; sulfates such as barium sulfate; sparingly soluble ion crystals such as calcium fluoride and barium fluoride; covalent crystals such as silicon and diamond; talc, montmorillonite, boehmite, etc. Examples thereof include substances derived from mineral resources such as zeolite, apatite, kaolin, mulite, spinel, olivine, sericite, bentonite, mica, and man-made products thereof. As the inorganic compound, a simple substance or a complex of these substances may be used alone, or two or more kinds thereof may be mixed and used. Among these inorganic compounds, silicon oxide, aluminum oxide, or aluminosilicate is preferable from the viewpoint of safety of the power storage device.

The porosity of the separator is preferably 80% by volume or less from the viewpoint of strength, and preferably 20% by volume or more from the viewpoint of discharge performance. Here, the "porosity" is a volume-based value, and means a value measured by a mercury porosity meter.

As the separator, a polymer gel composed of a polymer and a non-aqueous electrolyte may be used. Examples of the polymer include polyacrylonitrile, polyethylene oxide, polypropylene oxide, polymethylmethacrylate, polyvinylacetate, polyvinylpyrrolidone, polyvinylidene fluoride and the like. The use of polymer gel has the effect of suppressing liquid leakage. As the separator, a polymer gel may be used in combination with the above-mentioned porous resin film or non-woven fabric.

The thickness of the separator is preferably smaller than the average thickness of the insulating layer.
The thickness of the separator is preferably 1 μm or more and 40 μm or less, and more preferably 3 μm or more and 20 μm or less. By setting the thickness of the separator within the above range, it is possible to achieve both sufficient insulation and thinning.

The resistivity of the separator is preferably smaller than the resistivity of the insulating layer. Thereby, as the resistance of the separator capable of more sufficiently suppressing the dissolution of the fine copper powder, 1 × 10 12 Ωcm ² or more is preferable, and 1 × 10 13 Ωcm ² or more is more preferable. Sufficient insulation can be obtained by setting the resistivity of the separator to be equal to or higher than the above lower limit. The resistance of the separator is preferably as large as possible within the range not exceeding the resistivity of the insulating layer, and there is no particular upper limit, but for example, it may be 1 × 10 to the 15th power Ωcm ² or less, and 1 × 10 to the 14th power Ωcm ² or less. It may be. By setting the resistivity of the separator to the above upper limit or less, it becomes easy to maintain the effect of suppressing the dissolution of the fine copper powder even when the insulating layer deteriorates and the resistivity of the insulating layer decreases.

(Negative electrode)
The negative electrode has a negative electrode base material and a negative electrode active material layer arranged directly on the negative electrode base material or via an intermediate layer. The configuration of the intermediate layer is not particularly limited, and can be selected from, for example, the configurations exemplified by the positive electrode.

The negative electrode base material has conductivity. As the material of the negative electrode base material, metals such as copper, nickel, stainless steel, nickel-plated steel, and aluminum, or alloys thereof are used. The negative electrode base material preferably contains copper. For example, the content ratio of copper in the negative electrode base material is preferably 50% by mass or more, more preferably 80% by mass or more, further preferably 90% by mass or more, still more preferably 99% by mass or more. The content ratio of copper in the negative electrode base material may be 100% by mass or less. That is, copper or a copper alloy is preferable as the material of the negative electrode base material. Examples of the negative electrode base material include foils and vapor-deposited films, and foils are 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, electrolytic copper foil and the like.

The average thickness of the negative electrode base material is preferably 2 μm or more and 35 μm or less, more preferably 3 μm or more and 30 μm or less, further preferably 4 μm or more and 25 μm or less, and particularly preferably 5 μm or more and 20 μm or less. By setting the average thickness of the negative electrode 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 negative electrode base material.

The negative electrode active material layer contains a negative electrode active material. The negative 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 by the positive electrode.

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 adhesive and the filler.

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. As the negative electrode active material, the potential in the discharged state (SOC 0%) is 3.4 V vs. Those lower than Li / Li ⁺ are preferable from the viewpoints of high energy density and suppression of dissolution of fine copper powder. 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; carbon materials such as graphite (graphite) and non-graphitizable carbon (graphitizable carbon or non-graphitizable carbon). Be done. 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 thereof 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. Artificial graphite is preferable from the viewpoint that a material having stable physical properties can be obtained.

_{“Non-graphitic carbon” 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 0.34 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-graphitic 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.

Here, the "discharged state" in the definition of graphite and non-graphitic carbon means that the open circuit voltage is 0 in a unipolar battery 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. It means a state where the voltage is 7V or higher. Since the potential of the metal Li counter electrode in the open circuit state is substantially equal to the oxidation-reduction potential of Li, the open circuit voltage in the single-pole battery is substantially equal to the potential of the negative electrode containing the carbon material with respect to the oxidation-reduction potential of Li. .. That is, the fact that the open circuit voltage in the single-pole battery is 0.7 V or more means that lithium ions that can be occluded and discharged are sufficiently released from the carbon material that is the negative electrode active material during charging and discharging. ..

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.

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, for example, a carbon material, the average particle size thereof may be preferably 1 μm or more and 100 μm or less. When the negative electrode active material is a metal, a semi-metal, a metal oxide, a semi-metal oxide, a titanium-containing oxide, a polyphosphate compound or the like, the average particle size thereof may be preferably 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. The pulverization method and the powder grade method can be selected from, for example, the methods exemplified for the positive electrode.

The content of the negative electrode active material in the negative electrode active material layer is preferably 60% by mass or more and 99% by mass or less, and more preferably 90% by mass or more and 98% by mass or less. By setting the content of the negative electrode active material within the above range, it is possible to achieve both high energy density and manufacturability of the negative electrode active material layer.

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

The non-aqueous solvent can be appropriately selected from known non-aqueous solvents. Examples of the non-aqueous solvent include cyclic carbonates, chain carbonates, carboxylic acid esters, phosphoric acid esters, sulfonic acid esters, ethers, amides, nitriles and the like. As the non-aqueous solvent, those 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 carbonate. (DFEC), styrene carbonate, 1-phenylvinylene carbonate, 1,2-diphenylvinylene carbonate and the like can be mentioned. Of these, EC is preferable.

Examples of the chain carbonate include diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diphenyl carbonate, trifluoroethyl methyl carbonate, and bis (trifluoroethyl) carbonate. Of 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.

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.

Examples of the lithium salt 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 , and 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.

The non-aqueous electrolyte solution may contain additives. Additives include, for example, biphenyls, alkylbiphenyls, terphenyls, partially hydrides of terphenyls, aromatic compounds such as cyclohexylbenzene, t-butylbenzene, t-amylbenzene, diphenyl ethers, dibenzofurans; 2-fluorobiphenyls, o Partial halides of the aromatic compounds such as −cyclohexylfluorobenzene and p-cyclohexylfluorobenzene; such as 2,4-difluoroanisole, 2,5-difluoroanisole, 2,6-difluoroanisole, 3,5-difluoroanisole and the like. Anisole halide compounds; succinic anhydride, glutaric anhydride, maleic anhydride, citraconic anhydride, glutaconic anhydride, itaconic anhydride, cyclohexanedicarboxylic acid anhydride; ethylene sulfite, propylene sulfite, dimethyl sulfite, dimethyl sulfite, ethylene sulfate, Sulfolane, dimethylsulfone, diethylsulfone, dimethylsulfoxide, diethylsulfoxide, tetramethylenesulfoxide, diphenylsulfide, 4,4'-bis (2,2-dioxo-1,3,2-dioxathiolane), 4-methylsulfonyloxymethyl- Examples thereof include 2,2-dioxo-1,3,2-dioxathiolane, thioanisol, diphenyldisulfide, dipyridinium disulfide, perfluorooctane, tristrimethylsilyl borate, tristrimethylsilyl phosphate, tetraxtrimethylsilyl 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 is 0.1% by mass or more and 7% by mass or less with respect to the total mass of the non-aqueous electrolytic solution. It is more preferable to have it, more preferably 0.2% by mass or more and 5% by mass or less, and particularly preferably 0.3% by mass or more and 3% by mass or less. By setting the content of the additive in the above range, it is possible to improve the capacity maintenance performance or the cycle performance after high temperature storage, and further improve the safety.

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

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

Examples of the lithium ion secondary battery include Li _{2 SP 2} S ₅ , Li I-Li _{2 SP 2} S ₅ , Li ₁₀ Ge-P ₂ S _{12 and the} like as the sulfide solid electrolyte.

The shape of the power storage element of the present embodiment is not particularly limited, and examples thereof include a cylindrical battery, a square battery, a flat battery, a coin battery, and a button battery.

FIG. 7 shows a power storage element 40 as an example of a square battery. The figure is a perspective view of the inside of the container. The electrode body 41 having a wound positive electrode and a negative electrode is housed in a square container 42. The positive electrode is electrically connected to the positive electrode terminal 44 via the positive electrode lead 43. The negative electrode is electrically connected to the negative electrode terminal 46 via the negative electrode lead 45.

<Power storage device>
The power storage element of the present embodiment is a power source for automobiles such as an electric vehicle (EV), a hybrid vehicle (HEV), and a plug-in hybrid vehicle (PHEV), a power source for electronic devices such as a personal computer and a communication terminal, or a power source for power storage. Etc., it can be mounted as a power storage unit (battery module) composed of a plurality of power storage elements 40 assembled together. In this case, the technique of the present invention may be applied to at least one power storage element included in the power storage device.

FIG. 8 shows an example of a power storage device 60 in which a power storage unit 50 in which two or more electrically connected power storage elements 40 are assembled is further assembled. The power storage device 60 may include a bus bar (not shown) that electrically connects two or more power storage elements 40, a bus bar (not shown) that electrically connects two or more power storage units 50, and the like. The power storage unit 50 or the power storage device 60 may include a condition monitoring device (not shown) that monitors the state of one or more power storage elements.

<Manufacturing method of power storage element>
The method for manufacturing the power storage element of the present embodiment can be appropriately selected from known methods. The manufacturing method includes, for example, preparing an electrode body, preparing a non-aqueous electrolyte, and accommodating the electrode body and the non-aqueous electrolyte in a container. Preparing the electrode body includes, for example, preparing a positive electrode body and a negative electrode body, and forming the electrode body by laminating or winding the positive electrode body and the negative electrode body.

Containing the non-aqueous electrolyte in a container can be appropriately selected from known methods. For example, when a non-aqueous electrolyte solution is used as the non-aqueous electrolyte solution, the non-aqueous electrolyte solution may be injected from the injection port formed in the container, and then the injection port may be sealed.

<Other Embodiments>
The power storage element of the present invention is not limited to the above embodiment, and various modifications may be made without departing from the gist of the present invention. For example, the configuration of 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 case where the power storage element is used as a chargeable / dischargeable non-aqueous electrolyte secondary battery (for example, a lithium ion secondary battery) has been mainly described, but the type, shape, dimensions, capacity, etc. of the power storage element are arbitrary. Is. The present invention can also be applied to capacitors such as various secondary batteries, electric double layer capacitors and lithium ion capacitors.

In one embodiment of the present invention, the negative electrode may further have an insulating layer that covers the negative electrode active material layer. Further, in one embodiment of the present invention, the potential on the surface of the insulating layer of the positive electrode is 3.4 V vs. If it is lower than Li / Li ⁺ , a separator may be provided between the positive electrode and the negative electrode, and the surface of the insulating layer of the positive electrode may not be in direct contact with the surface of the negative electrode. When the separator is provided, it is preferable to use a separator having a relatively low volume resistivity and a relatively thin thickness because the potential on the surface of the insulating layer of the positive electrode can be lowered. Further, when the separator is provided, it is also preferable to provide an insulating layer having a relatively high volume resistivity and a relatively thick thickness because the potential on the surface of the insulating layer of the positive electrode can be lowered.

Further, the positive electrode active material layer may be laminated only on one surface of the positive electrode base material, or the negative electrode active material layer may be laminated only on one surface of the negative electrode base material. Further, the laminated structure including the positive electrode base material and the positive electrode active material layer covered by the insulating layer is not limited to the one composed of only the positive electrode base material and the positive electrode active material layer. The laminated structure may have, for example, an intermediate layer provided between the positive electrode base material and the positive electrode active material layer.

In one embodiment of the present invention, the insulating layer of the positive electrode has an insulating property, and the potential of the insulating layer of the positive electrode is 3.4 vs. If it is lower than Li / Li ⁺ , the insulating layer of the positive electrode may be a layer made of a solid electrolyte. That is, the insulating layer of the positive electrode may have ionic conductivity as long as it has the property of insulating electricity. Further, when the insulating layer of the positive electrode is a layer made of a solid electrolyte, the power storage element may be an all-solid-state battery.

10 Secondary battery (power storage element)
11 Positive electrode 12 Negative electrode 13 Positive electrode base material 14 Positive electrode active material layer 15 Insulation layer 16 Negative electrode base material 17 Negative electrode active material layer 18 Separator 20, 30 Power storage element 21, 31 Positive electrode active material layer 22, 32 Insulation layer 23, 33 Positive electrode 24, 34 Negative electrode active material layers 25, 35 Negative electrode 26 Separator A Copper fine powder P, Q Non-coated portion X Region of the positive electrode facing the negative electrode Y Laminated structure including the positive electrode base material and the positive electrode active material layer 40 Power storage element 41 Electrode body 42 Container 43 Positive electrode lead 44 Positive electrode terminal 45 Negative electrode lead 46 Negative electrode terminal 50 Power storage unit 60 Power storage device

Claims (5)

A positive electrode having a conductive positive electrode base material, a positive electrode active material layer and an insulating layer,
A negative electrode arranged to face the positive electrode and having a conductive negative electrode base material and a negative electrode active material layer,
A separator arranged between the positive electrode and the negative electrode is provided.
In the region of the positive electrode where the negative electrode faces, the insulating layer covers a laminated structure including the positive electrode base material and the positive electrode active material layer.
The potential on the surface of the insulating layer is 3.4 V vs. A power storage element that is lower than Li / Li ^+. The power storage element according to claim 1, wherein the average thickness of the insulating layer in the region of the positive electrode facing the negative electrode is larger than the thickness of the separator. The power storage element according to claim 1 or 2, wherein the insulating layer contains insulating particles. The power storage element according to any one of claims 1 to 3, wherein the insulating layer contains inorganic particles. The power storage element according to any one of claims 1 to 4, wherein the negative electrode base material contains copper.

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