JP2022079083A - Electrode structure and power storage device - Google Patents

Abstract

To realize a slow discharge mechanism at the time of internal short circuit in a sheet-shaped electrode.SOLUTION: An electrode structure according to the present disclosure includes a positive electrode including a positive electrode active material and a positive electrode current collector having a comb-tooth structure, which includes a plurality of current collectors adjacent to the positive electrode active material and a connection portion in which the current collectors are connected in parallel, and a negative electrode including a negative electrode active material and a negative electrode current collector having a comb-tooth structure arranged in the opposite direction to the comb-tooth structure of the positive electrode current collector, which is provided with a plurality of collectors adjacent to the negative electrode active material and a connection portion in which the collectors are connected in parallel.SELECTED DRAWING: Figure 1

Description

This specification discloses an electrode structure and a power storage device.

Conventionally, as a power storage device, current is collected from lead wires connected to a plurality of positions of a positive electrode plate and a negative electrode plate, and the current path inside the battery melts when the battery temperature rises above a predetermined temperature. A low melting point alloy member is inserted as a current cutoff mechanism for cutting off the current path (see, for example, Patent Document 1). This power storage device can provide a lithium secondary battery with excellent charge / discharge characteristics and safety, which reduces the internal resistance of the battery and has a current cutoff mechanism when the battery temperature rises due to the generation of a short-circuit current or the like. It is said that it can be done.

Japanese Unexamined Patent Publication No. 10-233233

However, in Patent Document 1, a pair of positive / negative sheet electrodes having an electrode material formed on a strip-shaped current collecting foil is used to collect electricity with a current collector having a thermal fuse function. Only charging and discharging via an external circuit can be stopped by operation, and it was not possible to suppress the discharge reaction when an internal short circuit occurs in the electrode. The reason is that the entire electrodes are connected by a low resistance current collector foil, so if an internal short circuit occurs, the discharge current from all the opposite positive / negative electrodes will be short-circuited through the low resistance current collector foil. This is because you will concentrate on the part. As described above, there has been a demand for a current collecting structure capable of coping with an internal short circuit of an electrode.

The present disclosure has been made in view of such a problem, and an object of the present disclosure is to provide an electrode structure and a power storage device capable of exhibiting a slow discharge mechanism at the time of an internal short circuit in a sheet-shaped electrode.

As a result of diligent research to achieve the above-mentioned object, the present inventors embedded a comb-shaped collector wire inside the active material, connected the collector wire in parallel to the connection portion, and reversed the direction in the positive and negative electrodes. It has been found that, if it has a comb-toothed structure, it is possible to efficiently collect electricity in a sheet-shaped electrode structure and to develop a slow discharge mechanism at the time of an internal short circuit, and the invention disclosed in the present specification. Has been completed.

That is, the electrode structure disclosed in the present specification is:
A positive electrode having a positive electrode active material, a positive electrode current collector having a comb-teeth structure including a plurality of collectors adjacent to the positive electrode active material and a connection portion in which the collectors are connected in parallel,
A negative electrode having a negative electrode active material, a plurality of collector wires adjacent to the negative electrode active material, and a connection portion in which the collector wires are connected in parallel, and arranged in the opposite direction to the comb tooth structure of the positive electrode current collector. A negative electrode with a current collector, and
It is equipped with.

The power storage device disclosed in this specification is
With the above-mentioned electrode structure,
An ion conduction medium that is interposed between the positive electrode and the negative electrode and conducts ions,
It is equipped with.

The present disclosure can develop a slow discharge mechanism at the time of an internal short circuit in a sheet-shaped electrode. The reason why such an effect is obtained is presumed as follows. For example, in a conventional storage device such as a lithium battery composed of a sheet-shaped electrode, current is collected from positive and negative electrodes by a continuous current collecting foil. Therefore, when an internal short circuit occurs between the positive and negative electrodes, all the currents from the opposite positive / negative sheet electrodes may be concentrated at the internal short circuit location through the continuous current collector foil. On the other hand, in the electrode structure and the power storage device of the present disclosure, since the current in the normal use area is arranged in a comb-shaped current collector (striped shape) having a resistance that allows the current to flow without any problem, normal charging / discharging is performed. Is done without problems. On the other hand, in a situation where an internal short circuit occurs in the electrode and all the current is concentrated at the short-circuited portion, the current tends to concentrate on the comb-shaped current collector near the short-circuited portion. At this time, since the volume of one comb-tooth current collector is much smaller than that of the continuous current collector foil, the resistance becomes extremely large even if a metal having the same volume resistivity is used. For this reason, the current value that flows concentrated in the short-circuited part becomes small, and it becomes a so-called slow discharge that slowly discharges over a long period of time. , Becomes a safe battery. By the way, the resistance of one comb-toothed current collector increases, but there is no problem because the current flowing through one comb-toothed current collector during normal use is a small current only for the electrodes near the current collector. It will flow. In other words, the current collector resistance in the electrodes of the entire battery is reduced to the value obtained by dividing the resistance of one comb-shaped current collector by the number of many comb teeth. In other words, by connecting a large number of relatively high resistance comb teeth in parallel, the current collection resistance of the entire battery is designed to be low, enabling smooth charging and discharging, and if an internal short circuit occurs somewhere, the resistance is high. Since it passes through one comb tooth, it becomes a slow discharge, and high safety can be guaranteed.

The schematic diagram which shows an example of the electrode structure 10. The schematic diagram which shows an example of the cross section of the electrode structure 10. The schematic diagram which shows an example of another electrode structure 10B. The schematic diagram which shows an example of another electrode structure 10C. The relationship diagram between the interval s of the collector wire and the discharge capacity ratio. Explanatory drawing of the electrode structure of Example 1. FIG. Explanatory drawing of the electrode structure of Example 3. FIG. Explanatory drawing of the electrode structure of the comparative example 1. FIG.

(Electrode structure)
The electrode structure of the present disclosure described in the embodiment is a sheet-shaped positive electrode and a negative electrode used in a power storage device facing each other. This electrode structure includes a positive electrode having a positive electrode active material and a positive electrode current collector having a comb-toothed structure having a collecting wire adjacent to the positive electrode active material and a connection portion to which the collecting wire is connected, and a negative electrode active material and a negative electrode active material. A negative electrode having a negative electrode current collector having a comb-tooth structure, which is adjacent to the positive electrode and is arranged in the opposite direction to the comb-tooth structure of the positive electrode current collector and has a connection portion to which the collector wire is connected, is provided.

The power storage device disclosed in this embodiment will be described with reference to the drawings. 1 is a schematic view showing an example of the electrode structure 10, FIG. 1A is a sectional view taken along the line AA of FIG. 1B, FIG. 1B is a side view of the electrode structure 10, and FIG. 1C is a sectional view taken along the line BB of FIG. 1B. It is a figure, and FIG. 1D is an explanatory view of a positive electrode current collecting unit 30. FIG. 2 is a schematic view showing an example of a cross section of the electrode structure 10 orthogonal to the longitudinal direction of the collector wires 23 and 33. 3A and 3B are schematic views showing an example of another electrode structure 10B, FIG. 3A is a side view of the electrode structure 10B, and FIG. 3B is an explanatory view of a positive electrode current collector 30B. FIG. 4 is a schematic view showing an example of another electrode structure 10C. The electrode structure 10 includes a negative electrode 12 and a positive electrode 16. The electrode structure 10 may include a separator 15 between the negative electrode 12 and the positive electrode 16. The electrode structure 10 has a structure in which a sheet-shaped negative electrode 12, a sheet-shaped separator 15, and a sheet-shaped positive electrode 16 are laminated. Further, the electrode structure 10 may have a structure in which a single cell 11 having a negative electrode 12, a separator 15, and a positive electrode 16 is further laminated (see FIG. 2).

The negative electrode 12 includes a negative electrode active material layer 13 and a negative electrode current collector 20. The negative electrode 12 may be formed by bringing the negative electrode active material layer 13 and the negative electrode current collector 20 into close contact with each other. For example, the negative electrode active material, the conductive material, and the binder are mixed, and an appropriate solvent is added. The paste-like negative electrode mixture may be applied and dried so that the negative electrode current collector 20 is embedded, and if necessary, compressed to increase the electrode density. The negative electrode active material layer 13 may include a negative electrode active material, a conductive material, and a binder. Examples of the negative electrode active material include inorganic compounds such as lithium, lithium alloys and tin compounds, carbonaceous materials capable of storing and releasing lithium ions, composite oxides containing a plurality of elements, and conductive polymers. Examples of the carbonaceous material include cokes, glassy carbons, graphites, non-graphitizable carbons, pyrolytic carbons, carbon fibers and the like. Of these, graphites such as artificial graphite and natural graphite have an operating potential close to that of metallic lithium and can be charged and discharged at a high operating voltage. When lithium salt is used as a supporting salt, self-discharge is suppressed. Moreover, it is preferable because the irreversible capacity at the time of charging can be reduced. Examples of the composite oxide include lithium titanium composite oxide and lithium vanadium composite oxide. Of these, the carbonaceous material is preferable as the negative electrode active material from the viewpoint of safety.

The conductive material is not particularly limited as long as it is an electronically conductive material that does not adversely affect the battery performance of the positive electrode, and for example, graphite such as natural graphite (scaly graphite, scaly graphite) or artificial graphite, acetylene black, carbon black, etc. One or a mixture of one or more of Ketjen black, carbon whisker, graphite coke, carbon fiber, metal (copper, nickel, aluminum, silver, gold, etc.) can be used. Among these, carbon black and acetylene black are preferable as the conductive material from the viewpoint of electron conductivity and coatability. The binder serves to hold the active material particles and the conductive material particles together, and is, for example, a fluororesin such as polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), fluororubber, or polypropylene. A thermoplastic resin such as polyethylene, ethylene propylene diene rubber (EPDM), sulfonated EPDM rubber, natural butyl rubber (NBR) and the like can be used alone or as a mixture of two or more kinds. Further, an aqueous dispersion of cellulose-based binder or styrene-butadiene rubber (SBR), which is an aqueous binder, can also be used. Examples of the solvent for dispersing the positive electrode active material, the conductive material, and the binder include N-methylpyrrolidone, dimethylformamide, dimethylacetamide, methylethylketone, cyclohexanone, methyl acetate, methyl acrylate, diethylenetriamine, and N, N-dimethylaminopropylamine. , Ethylene oxide, tetrahydrofuran and other organic solvents can be used. Further, a dispersant, a thickener or the like may be added to water, and the active material may be slurryed with a latex such as SBR. As the thickener, for example, polysaccharides such as carboxymethyl cellulose and methyl cellulose can be used alone or as a mixture of two or more kinds. Examples of the coating method include roller coating such as applicator roll, screen coating, doctor blade method, spin coating, bar coater, and the like, and any of these can be used to obtain an arbitrary thickness and shape.

The negative electrode current collector 20 is a member having a comb-tooth structure having a current collector 23 and a connection portion 21. The collector wire 23 is a plurality of linear members that are adjacent to the negative electrode active material and are not electrically connected to each other at the portion in contact with the negative electrode active material. The collector wire 23 may have a square or rectangular cross-sectional shape, or may be a polygonal pillar such as a cylinder, an elliptical pillar, a hexagonal pillar, or an octagonal pillar. The connection portion 21 is a member that is a continuous body that connects a plurality of collector wires 23 in parallel outside the collector wire 23 and the negative electrode active material that are not in contact with each other. The connecting portion 21 is a foil-shaped or plate-shaped member whose longitudinal direction is the arrangement direction of the collecting wires 23.

The collector wire 23 includes copper, nickel, stainless steel, titanium, aluminum, calcined carbon, conductive polymer, conductive glass, Al-Cd alloy, etc., as well as for the purpose of improving adhesiveness, conductivity, and reduction resistance. For example, one having a surface of copper or the like treated with carbon, nickel, titanium, silver or the like can also be used. For these, it is also possible to oxidize the surface. As shown in FIG. 2, the negative electrode current collector 20 may have a structure in which the current collector 23 is embedded in the negative electrode active material layer 13 other than the end portion.

The negative electrode 12 includes a positive electrode current collector 20 having a connection portion 21 for connecting a plurality of current collectors 23 in parallel. The connecting portion 21 may have collector wires 23 having 100 or more lines N connected in parallel, or may have 200 or more or 500 or more collector wires 23 connected in parallel. good. Since the resistance applied to the single cell 11 via the connection portion 21 is determined according to the number N of parallel connections, the number N of parallel connections of the collector wire 23, the connection portion 21, and the connection portion 21 are determined according to the desired charge / discharge characteristics. The volume resistivity of the collector wire 23 may be appropriately set. Further, since the amount of the negative electrode active material per unit volume decreases as the number N of the collector wires 23 increases, the number N of the collector wires 23 may be appropriately set from the viewpoint of energy density. The negative electrode current collector 20 may have a volume resistivity of 1.0 × 10 ^-7 Ωm or less. Further, the negative electrode current collector 20 may have a volume resistivity of 5.0 × 10 ^-8 Ωm or less, or may have a volume resistivity of 2.0 × 10 ^-8 Ωm or less. The volume resistivity of the collector wire 23 and the connection portion 21 may be the same or different.

In the negative electrode current collector 20, the width t of the current collector 23 is preferably 2 mm or less, and the pitch P of the current collector 23 is preferably 2 mm or less. In this range, the decrease in discharge capacity can be further suppressed. The width t and the pitch P may have the same value or different values, but it is preferable that the width t and the pitch P have the same value in consideration of the supportability at the time of stacking. The width t of the collecting wire is preferably 100 μm or more, more preferably 200 μm or more, and may be 400 μm or more. Further, the width t is preferably 1 mm or less, more preferably 750 μm or less, and may be 500 μm or less. The pitch P of the collector wire is preferably 100 μm or more, more preferably 200 μm or more, and may be 400 μm or more. Further, the pitch P is preferably 1 mm or less, more preferably 750 μm or less, and may be 500 μm or less.

The separator 15 insulates the negative electrode 12 and the positive electrode 16 without inhibiting the ionic conduction of carrier ions (for example, lithium ions). The separator 15 is not particularly limited as long as it has a composition that can withstand the range of use of the electrode structure 10, but is, for example, a polymer nonwoven fabric such as a polypropylene nonwoven fabric or a polyphenylene sulfide nonwoven fabric, or a thin olefin resin such as polyethylene or polypropylene. Examples include microporous membranes. These may be used alone or in combination of two or more. The thickness of the separator 15 is, for example, preferably 5 μm or more, more preferably 8 μm or more, and may be 10 μm or more. When this thickness is 5 μm or more, it is preferable in order to secure the insulating property. The thickness of the separator 15 is preferably 15 μm or less, and more preferably 10 μm or less. When this thickness is 15 μm or less, it is preferable in that the decrease in ionic conductivity can be suppressed and the volume occupied in the cell can be further reduced.

The positive electrode 16 may have a positive electrode active material layer 17 and a positive electrode current collector 30. The positive electrode active material layer 17 may include a positive electrode active material, a conductive material, and a binder, if necessary. For the positive electrode 16, for example, a positive electrode active material, a conductive material, and a binder are mixed, and an appropriate solvent is added to form a paste-like positive electrode mixture, which is then applied and dried so that the positive electrode current collector 30 is embedded. Then, if necessary, it may be formed by compression to increase the electrode density. Examples of the positive electrode active material include a material capable of occluding and releasing lithium as a carrier. Examples of the positive electrode active material include compounds having lithium and a transition metal, for example, an oxide containing lithium and a transition metal element, a phosphoric acid compound containing lithium and a transition metal element, and the like. Specifically, a lithium manganese composite oxide having a basic composition formula of Li _(1-x) MnO ₂ (0 ≦ x ≦ 1, etc., the same applies hereinafter) or Li _(1-x) Mn ₂ O ₄ or the like, basic composition. Lithium-cobalt composite oxide with formula Li _(1-x) CoO ₂ , etc., lithium nickel composite oxide with basic composition formula Li _(1-x) NiO ₂ , etc., basic composition formula Li _(1-x) Co _a Ni _b Mn _c O ₂ (a> 0, b> 0, c> 0, a + b + c = 1), Li _(1-x) Co _a Ni _b Mn _c O ₄ (0 <a <1, 0 <b) Lithium cobalt nickel-manganese composite oxide with <1, 1 ≦ c <2, a + b + c = 2), etc., lithium vanadium composite oxide with basic composition formula such as LiV ₂ O ₃ , basic composition formula V ₂ O ₅ , etc. A transition metal oxide or the like can be used. Further, a lithium iron phosphate compound having a basic composition formula of LiFePO ₄ can be used as the positive electrode active material. Of these, lithium cobalt nickel-manganese composite oxides such as LiCo _1/3 Ni _1/3 Mn _1/3 O ₂ and LiNi _0.4 Co _0.3 Mn _0.3 O ₂ are preferable. The "basic composition formula" means that other elements such as Al and Mg may be contained. Further, as the conductive material, the binder, the solvent and the like used for the positive electrode, those exemplified for the negative electrode 12 can be used.

In the positive electrode 16, the content of the positive electrode active material is preferably larger, preferably 70% by mass or more, and more preferably 80% by mass or more with respect to the total mass of the positive electrode 16. The content of the conductive material is preferably in the range of 0% by mass or more and 20% by mass or less, and more preferably in the range of 0% by mass or more and 10% by mass or less with respect to the total mass of the positive electrode 16. In such a range, it is possible to suppress a decrease in battery capacity and sufficiently impart conductivity. The content of the binder is preferably in the range of 0.1% by mass or more and 5% by mass or less, and in the range of 0.2% by mass or more and 3% by mass or less with respect to the total mass of the positive electrode 16. Is more preferable.

The positive electrode current collector 30 is a member having a comb tooth structure having a current collector 33 and a connection portion 31. The collector wire 33 is a plurality of linear members that are adjacent to the positive electrode active material and are not electrically connected to each other at the portion in contact with the positive electrode active material. The collector wire 33 may have a square or rectangular cross-sectional shape, or may be a polygonal pillar such as a cylinder, an elliptical pillar, a hexagonal pillar, or an octagonal pillar. The connection portion 31 is a member that is a continuous body that connects a plurality of collector wires 33 in parallel outside the collector wire 33 and the positive electrode active material that are not in contact with each other. The connecting portion 31 is a foil-shaped or plate-shaped member whose longitudinal direction is the arrangement direction of the collecting wires 33.

The collector wire 33 includes copper, nickel, stainless steel, titanium, aluminum, calcined carbon, conductive polymer, conductive glass, Al-Cd alloy, etc., as well as for the purpose of improving adhesiveness, conductivity, and reduction resistance. For example, one having a surface of copper or the like treated with carbon, nickel, titanium, silver or the like can also be used. For these, it is also possible to oxidize the surface. As shown in FIG. 2, the positive electrode current collector 30 may have a structure in which the current collector 33 is embedded in the positive electrode active material layer 17 other than the end portion.

The positive electrode 16 includes a positive electrode current collector 30 having a connection portion 31 for connecting a plurality of current collectors 33 in parallel. The connection portion 31 may have collector wires 33 having 100 or more lines N connected in parallel, or may have 200 or more or 500 or more collector wires 33 connected in parallel. good. Since the resistance applied to the single cell 11 via the connection portion 31 is determined according to the number N of parallel connections, the number N of parallel connections of the collector wire 33, the connection portion 31, and the connection portion 31 are determined according to the desired charge / discharge characteristics. The volume resistivity of the collector wire 33 may be appropriately set. Further, since the amount of the negative electrode active material per unit volume decreases as the number N of the collector wires 33 increases, the number N of the collector wires 33 may be appropriately set from the viewpoint of energy density. The positive electrode current collector 30 may have a volume resistivity of 1.0 × 10 ^-7 Ωm or less. Further, the positive electrode current collector 30 may have a volume resistivity of 5.0 × 10 ^-8 Ωm or less, or may have a volume resistivity of 2.0 × 10 ^-8 Ωm or less. The volume resistivity of the collector wire 33 and the connection portion 31 may be the same or different.

In the positive electrode current collector portion 30, the width t of the current collector 33 is preferably 2 mm or less, and the pitch P of the current collector 33 is preferably 2 mm or less. In this range, the decrease in discharge capacity can be further suppressed. The width t and the pitch P may have the same value or different values, but it is preferable that the width t and the pitch P have the same value in consideration of the supportability at the time of stacking. The width t of the collecting wire is preferably 100 μm or more, more preferably 200 μm or more, and may be 400 μm or more. Further, the width t is preferably 1 mm or less, more preferably 750 μm or less, and may be 500 μm or less. The pitch P of the collector wire is preferably 100 μm or more, more preferably 200 μm or more, and may be 400 μm or more. Further, the pitch P is preferably 1 mm or less, more preferably 750 μm or less, and may be 500 μm or less. The positive electrode current collector 30 may have the same configuration as the negative electrode current collector 20 or may have a different configuration, but it is more preferable to have the same configuration as the negative electrode current collector 20. ..

From the viewpoint of safety, the slow discharge function of the electrode structure 10 at the time of an internal short circuit from a fully charged state is preferably longer, for example, preferably 30 minutes or longer, and preferably 1 hour or longer. More preferably, it is more preferably 2 hours or more. If this slow discharge function is longer, sudden discharge can be further suppressed at the time of partial short circuit inside the cell, and safety can be further ensured. This slow discharge function may be 5 hours or less from the viewpoint of energy density, such as an increase in the resistance of the electrode structure 10.

As shown in FIG. 3, the positive electrode 16B having the positive electrode current collector 30B in which the collector wire 33 is arranged at an angle with respect to the perpendicular wire from the connection portion 31 and the collector wire 23 with respect to the perpendicular wire from the connection portion 21. The electrode structure 10B may be provided with a negative electrode structure 10B including a negative electrode current collector 20B arranged at an angle and a negative electrode structure 10B. In the electrode structure 10B, it is preferable that the collector wire 23 and the collector wire 33 have a structure inclined in the opposite direction. In this electrode structure 10B, unevenness of charge / discharge reaction due to pitch deviation of comb teeth can be further suppressed. It is preferable that the current collector 33 of the positive electrode current collector 30B and the current collector 23 of the negative electrode current collector 20 intersect in a range of 1 time or more and 3 times or less. In this range, the unevenness of charge / discharge reaction can be further suppressed, and the region where the collector wires 23 and 33 are absent can be further suppressed. The positive electrode current collector 30B can satisfy P ≦ L · tan θ when the length L of the collector wire 33, the pitch P between the collector wires, and the angle θ of the collector wire with respect to the line orthogonal to the connection portion. preferable. In this range, the collection wires 23 and 33 intersect at least once. At this time, the positive electrode current collector 30B may satisfy 3P ≧ L · tan θ. Further, the negative electrode current collector 20B may have the same configuration as the positive electrode current collector 30B or may have a different configuration, but may have the same configuration as the positive electrode current collector 30B. preferable. Here, it is assumed that the configuration of the negative electrode current collector 20B can adopt the same configuration as that of the positive electrode current collector 30B, and the description thereof will be omitted.

As shown in FIG. 4, a positive electrode 16C having a positive electrode current collector 30C having a collector wire 33 formed on a support film 19 having no electron conductivity and a support film 18 having no electron conductivity were formed. The electrode structure 10C may be provided with a negative electrode 12C having a negative electrode current collecting unit 20C having a collecting wire 23. If the current collectors 23 and 33 are formed on the support films 18 and 19, it is easy to form a comb-shaped current collector structure. FIG. 4 shows a cross section orthogonal to the collector wires 23 and 33. It is preferable that the collector wires 33 are alternately formed on the front and back surfaces of the support film 19 so as not to overlap each other. Further, it is preferable that the collecting wires 33 and 23 facing each other via the separator 15 are formed alternately so as not to overlap each other. At this time, as shown in FIG. 3, the collecting wires 23 and 33 may be inclined with respect to the perpendicular lines from the connecting portions 21 and 31. The support films 18 and 19 may be, for example, resin films. As this resin, for example, a resin having high heat resistance is preferable, and special engineering resins such as polyimide resin, polytetrafluoroethylene resin, polyamideimide resin and polysulfone, general-purpose engineering resin such as polyamide, polyacetal and polycarbonate, polyethylene, etc. Examples thereof include general-purpose resins such as polypropylene and polyvinylidene fluoride. The thickness of the support films 18 and 19 is preferably thinner, preferably 10 μm or less, more preferably 5 μm or less, and may be 4 μm or less. Further, the thickness of the support films 18 and 19 needs to be thick enough to form the collector wires 23 and 33, and may be, for example, 2 μm or more.

(Power storage device)
The energy storage device of the present disclosure described in the embodiment includes the above-mentioned electrode structure, an ion conduction medium interposed between the positive electrode and the negative electrode to conduct ions, and a separator interposed between the positive electrode and the negative electrode. It may be used as an electrode. The electric storage device may be, for example, an electric double layer capacitor, a hybrid capacitor, a pseudo electric double layer capacitor, an alkali metal secondary battery, an alkali metal ion battery, or the like. Examples of the carrier ion of the energy storage device include alkali metal ions such as lithium ion, sodium ion and potassium ion, and group 2 ions such as magnesium ion, strontium ion and calcium ion. Here, for convenience of explanation, a lithium ion secondary battery having a lithium ion as a carrier will be described below as a main example thereof.

As the ion conduction medium, a non-aqueous electrolytic solution containing a supporting salt, a non-aqueous gel electrolytic solution, or the like can be used. Examples of the solvent for the non-aqueous electrolytic solution include carbonates, esters, ethers, nitriles, furans, sulfolanes, dioxolanes and the like, and these can be used alone or in combination. Specifically, as carbonates, cyclic carbonates such as ethylene carbonate (EC), propylene carbonate, vinylene carbonate, butylene carbonate, and chloroethylene carbonate, dimethyl carbonate (DMC), ethylmethyl carbonate (EMC), diethyl carbonate, and ethyl are used. Chain carbonates such as -n-butyl carbonate, methyl-t-butyl carbonate, di-i-propyl carbonate, t-butyl-i-propyl carbonate, cyclic esters such as γ-butyl lactone and γ-valerolactone, Chain esters such as methyl formate, methyl acetate, ethyl acetate, methyl butyrate, ethers such as dimethoxyethane, ethoxymethoxy ethane, diethoxyethane, nitriles such as acetonitrile and benzonitrile, furan such as tetrahydrofuran and methyl tetrahydrofuran, etc. , Sulfolane, sulfolans such as tetramethylsulfolan, and dioxolans such as 1,3-dioxolane and methyldioxolan. In this electrolytic solution, a supporting salt containing ions which are carriers of the electrode structure 10 may be dissolved. Examples of the supporting salt include LiPF ₆ , LiBF ₄ , LiAsF ₆ , LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiC (CF ₃ SO ₂ ) ₃ , LiSbF ₆ , LiSiF ₆ , LiAlF ₄ , LiSCN, and the like. Examples thereof include LiClO ₄ , LiCl, LiF, LiBr, LiI, and LiAlCl ₄ . Of these, 1 selected from the group consisting of inorganic salts such as LiPF ₆ , LiBF ₄ , and LiClO ₄ , and organic salts such as LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , and LiC (CF ₃ SO ₂ ) ₃ . It is preferable to use a seed or a combination of two or more kinds of salts from the viewpoint of electrical characteristics. The concentration of this supporting salt in the electrolytic solution is preferably 0.1 mol / L or more and 5 mol / L or less, and more preferably 0.5 mol / L or more and 2 mol / L or less.

The separator 15 may be used as a solid electrolyte as an ion conduction medium. Examples of the solid electrolyte include an inorganic solid electrolyte and a polymer solid electrolyte. The solid electrolyte is not limited to the following composition and structure, and may be any one in which Li ions can move. As long as the compound illustrated below is used as the basic skeleton, it can be used even if it is partially substituted or has a different composition ratio. Examples of the inorganic solid electrolyte include Li ₃ N, Li ₁₄ Zn (GeO ₄ ) ₄ called LISION, Li _3.25 Ge _0.25 P _0.75 S ₄ of sulfide, and La _0.5 Li _0.5 TiO ₃ of the perovskite type, (La _{2 /). 3} Li _3x □ _{1 / 3-2x} ) TIM ₃ (□: atomic vacancies), garnet type Li ₇ La ₃ Zr ₂ O ₁₂ , NASION type Li Ti ₂ (PO ₄ ) ₃ , Li _1.3 M _0.3 Ti _1.7 (PO ₃ ) ₄ (M = Sc, Al), Li ₇ P ₃ S ₁₁ obtained from glass having a composition of 80 Li ₂ S / 20 P ₂ S ₅ (mol%), which is a glass ceramic, and high conductivity in a sulfide system. Li ₁₀ Ge ₂ PS ₂ , which is a substance with a ratio, Li ₂ S-SiS ₂ , Li ₂ S-SiS ₂ -Li I, Li ₂ S-SiS ₂ -Li ₃ PO ₄ , Li ₂ S for glass-based inorganic solid electrolytes. -SiS ₂ -Li ₄ SiO ₄ , Li ₂ SP ₂ S ₅ , Li ₃ PO ₄ -Li ₄ SiO ₄ , Li ₃ BO ₄ -Li ₄ SiO ₄ , and SiO ₂ , GeO ₂ , B ₂ O ₃ , Examples include those using P ₂ O ₅ as a glass-based substance and Li ₂ O as a network modifier, and Li 2S-GeS ₂ series, Li 2S _- GeS _{2 -} ZnS series, and Li 2S- as _thiolithicon solid electrolytes. Ga ₂ S ₂ series, Li ₂ S-GeS ₂ -Ga ₂ S ₃ series, Li ₂ S-GeS ₂ -P ₂ S ₅ series, Li ₂ S-GeS ₂ -SbS ₅ series, Li ₂ S-GeS _2- Al ₂ S ₃ series, Li ₂ S-SiS ₂ series, Li ₂ SP ₂ S ₅ series, Li ₂ S-Al ₂ S ₃ series, LiS-SiS ₂ -Al ₂ S ₃ series, Li ₂ S-SiS ₂ -P ₂ S ₅ series and the like can be mentioned.

Examples of the polymer solid electrolyte include a complex of polyethylene oxide (PEO) and an alkali metal, and if it is a polymer, the unit structure of a polymer material that dissolves a lithium salt is not limited to PEO. PEO, PPO: poly (propylene oxide), Polyamine-based PEI: poly (ethylene imine), PAN: poly (acrylo nitrile), Polysulfide-based PAS: poly (polyethylene sulfide), and the like. Examples of the lithium salt include LiTFSI: (LiN (SO ₂ CF ₃ ) ₂ ), LiPEI: (COCF ₂ SO ₂ NLi) n, and LiPPI: (COCF (CF ₃ OCF ₂ CF ₂ SO ₂ NLi)) _n . Further, a gel polymer electrolyte using PVdF (PolyVinylidene DiFluoride), PAN, HFP (Hexafluoropropylene) and the like can be mentioned. Further, examples of the organic ionic plastic electrolyte include those having a plastic crystal phase. Representative molecules of the plastic crystal phase include Tetrachloromethane, Cyclohexane, Succinonitrile, etc., and Tf ₂ N: (trifluoromethylsulfonyl) amide, LiBF ₄ is added to these plastic crystal phases, or aliphatic quaternary ammonium is added. It may be a combination of a salt having a plastic crystal phase composed of and a perfluoroanion. Organic / inorganic hybrid ion gel in which ionic liquid and glass components are mixed at the molecular level, that is, organic boron-based ion gel electrolyte using cellulose, organic boron-based ion gel electrolyte using amylose, and boron polysubstituted macrocycle derived from cyclodextrin. And so on.

The shape of the power storage device is not particularly limited, and examples thereof include a coin type, a button type, a sheet type, a laminated type, a cylindrical type, a flat type, and a square type. Further, a plurality of such batteries may be connected in series and applied to a large-sized battery used for an electric vehicle or the like.

In the electrode structure 10 described in detail above, the slow discharge mechanism at the time of internal short circuit can be exhibited in the sheet-shaped electrode. The reason why such an effect is obtained is presumed as follows. For example, since the collecting wires are arranged in a stripe shape, normal charging / discharging can be performed without any problem. On the other hand, in a situation where an internal short circuit occurs in the electrode and all the current is concentrated at the short-circuited portion, the current tends to concentrate on the collecting wire near the short-circuited portion. However, since the volume of one current collector is much smaller than that of a continuous current collector foil, the resistance increases even if members having the same volume resistivity are used. Therefore, the value of the current concentrated in the short-circuited portion becomes small, and the discharge is slow over a long period of time, that is, so-called slow discharge, and the Joule heat generation in the short-circuited portion is significantly suppressed, which is safe. Although the resistance of one current collector increases, the current flowing through one current collector during normal use is a small current only for the electrodes in the vicinity of the current collector, so that the current flows without any problem. In other words, the current collector resistance in the electrodes of the entire cell becomes as small as the value obtained by dividing one current collector resistance by the number of a large number of current collectors. In other words, by connecting a large number of collector wires in parallel, the current collection resistance of the entire cell is designed to be low, enabling smooth charging and discharging, and if an internal short circuit occurs somewhere, a single collection with relatively high resistance. Since it passes through an electric wire, it becomes a slow discharge, and high safety can be guaranteed.

Further, by providing the connecting portions 21 and 31 which are continuous bodies, it is possible to connect a large number of collecting wires in parallel. The resistance of the connecting portions 21 and 31 can be easily controlled by controlling the thickness of the member. Therefore, in this electrode structure 10, it is possible to achieve both high energy density by efficient current collection and a slow discharge mechanism at the time of an internal short circuit.

It should be noted that the present disclosure is not limited to the above-described embodiment, and it goes without saying that the present disclosure can be carried out in various embodiments as long as it belongs to the technical scope of the present disclosure.

For example, in the above-described embodiment, the carrier of the power storage device is lithium ion, but the carrier is not particularly limited to this, and it may be an alkali metal ion such as sodium ion or potassium ion, or a group 2 element ion such as calcium ion or magnesium ion. good. Further, the positive electrode active material may contain carrier ions. Further, although the electrolytic solution is a non-aqueous electrolytic solution, an aqueous solution-based electrolytic solution may be used.

In the above-described embodiment, the positive electrode active material is a transition metal composite oxide, but the present invention is not particularly limited, and for example, it may be a carbon material used for a capacitor. The carbon material is not particularly limited, but for example, activated carbons, cokes, glassy carbons, graphites, graphitizable carbons, pyrolytic carbons, carbon fibers, carbon nanotubes, etc. Examples include graphite. Of these, activated carbons having a high specific surface area are preferable. Activated carbon as a carbon material preferably has a specific surface area of 1000 m ² / g or more, and more preferably 1500 m ² / g or more. When the specific surface area is 1000 m ² / g or more, the discharge capacity can be further increased. The specific surface area of this activated carbon is preferably 3000 m ² / g or less, and more preferably 2000 m ² / g or less, from the viewpoint of ease of production. It is considered that at the positive electrode, at least one of the anion and the cation contained in the ion conduction medium is adsorbed and desorbed to store electricity, but further, at least one of the anion and the cation contained in the ion conduction medium is inserted and desorbed. It may be used to store electricity.

Hereinafter, an example in which the above-mentioned electrode structure and power storage device are specifically manufactured will be described as examples.

(Consideration of the effect of comb tooth spacing during normal charging and discharging)
When the C rate is 0.05 and 1.0 when the pitch P is changed to 2500 μm from the conventional foil-like current collector foil in which the pitch P (interval) of the comb teeth is 0 by simulation (calculation). The discharge capacity of the foil was calculated, and the ratio to the discharge capacity of the foil-like collector foil was plotted. FIG. 5 is a diagram showing the relationship between the distance between the collector wires and the discharge capacity ratio. In each case, the discharge was started from the fully charged state of 4.1 V. Further, the calculation was performed assuming a current collector in which the width t of the comb teeth and the pitch P are the same values. As the C rate increased, the discharge capacity decreased significantly with the increase in the comb tooth spacing, but even if the discharge rate was increased to 1C, it was possible to discharge about 60% when the comb tooth spacing was 2 mm. It was found that when the comb tooth spacing was 500 μm or less, the decrease in discharge capacity was negligible. Therefore, it was determined that a comb tooth pitch P of 2 mm or less is appropriate.

(Example 1)
(Examination of electrode structure and power storage device)
FIG. 6 is an explanatory diagram of the electrode structure of the first embodiment. As shown in FIG. 6, a lithium ion secondary battery in which 30 sets of single cells in which current collectors having a comb-tooth structure are arranged in opposite directions and opposed to each other are stacked is used as Example 1. The thickness of the positive electrode active material layer was 80 μm on one side, a polyethylene separator having a thickness of 15 μm was used as the separator, and the thickness of the negative electrode active material layer was 60 μm on one side. The material of the positive electrode current collector is Al, the length of the current collector is 70 mm, the width t is 335 μm, and the thickness is 7 μm. The negative electrode current collector was made of Cu, the length of the current collector was 70 mm, the width t was 200 μm, and the thickness was 7 μm. Due to the difference in volume resistivity, the resistance of both Al and Cu with a path length of 70 mm is 0.84 Ω. In this electrode structure, even if an internal short circuit occurs in any of the electrodes and the comb teeth of the Al and Cu current collectors are short-circuited with zero resistance, the current from all the electrodes is combined with the positive and negative electrodes. It will pass through the comb teeth with a resistance of 0.84Ω. Since the maximum voltage of the battery is 4.1V, the current flowing through the short-circuited portion is limited to 4.9A, and the calorific value remains at 20W at the maximum. Further, when the battery capacity is 10 Ah, the battery is slowly discharged for 2 hours or more, and the short-circuited portion does not reach the thermal runaway region, so that the battery is extremely safe. By the way, consider a normal charge / discharge reaction. Assuming that the battery in which 30 sets of electrodes of FIG. 6 are stacked is 200 μm between Al comb teeth and 330 μm between Cu comb teeth, the number of comb teeth of one electrode is 264 for both positive and negative electrodes. Since the number of electrodes is 30, the number of comb teeth is 7920. Since the resistance per comb tooth is 0.84Ω, the positive electrode current collection resistance is 0.1mΩ, and even if the positive and negative are combined, it is extremely low at 0.2mΩ, so normal charging and discharging should be performed without problems. Can be done. The resistance of the entire comb tooth current collector is low enough to allow a current of 4.1 V / 0.0002 Ω = 20500 A to flow. The resistance (0 ° C.) is 2.80 μΩcm for aluminum, 1.68 μΩcm for copper, 1.0 Ωcm for the positive electrode mixture (plane direction / after pressing), and the negative electrode (plane direction / after pressing). ) Was 0.25 Ωcm.

(Example 2)
The result of examining the electrode structure shown in FIG. 3 was referred to as Example 2. When both the positive electrode current collector foil and the negative electrode current collector are comb-shaped, there is a concern that reaction unevenness may occur due to the deviation of the comb-tooth pitch when facing the positive / negative electrode. Therefore, in order to suppress the pitch shift, the comb tooth angles of the positive electrode and the negative electrode are tilted in opposite directions to suppress the reaction unevenness. In order to eliminate the lateral displacement of the positive / negative electrode, it is sufficient that the inclination angle θ with respect to the perpendicular line from the connection portion and the lateral displacement W with respect to the length L of the collector wire are larger than the pitch P of the comb tooth collection, so P ≦ It was inferred that L. tan θ should be satisfied. Further, it was presumed that it is preferable to satisfy 3P ≧ L · tan θ.

(Example 3)
The result of examining the electrode structure shown in FIG. 4 was referred to as Example 3. The comb-toothed current collector structure was patterned into a film without electron conductivity. FIG. 7 is an explanatory diagram of the electrode structure of the third embodiment. A polyethylene separator having a thickness of 60 μm and a thickness of 15 μm was used for the positive electrode active material layer, and the thickness of the negative electrode active material layer was set to 50 μm. The film was made of a polyimide resin having a thickness of 10 μm. The thickness, width, and length of the current collectors of the positive electrode current collector and the negative electrode current collector were the same as in Example 1. In this way, when the current collector is formed on the film, the electrode can be reliably produced without electrically contacting each current collector with the comb-shaped current collector, which is relatively thin and long. Was made.

(Comparative Example 1)
A Li-ion secondary battery in which 30 sets of single cells equipped with a negative electrode having a foil-shaped current collector and a positive electrode were laminated was used as Comparative Example 1, and the current flowing through the short-circuited portion was examined. FIG. 8 is an explanatory diagram of the electrode structure of Comparative Example 1. The shape of one electrode is VDA size 80 mm in length and 140 mm in width, of which 70 mm is the electrode coating part and 10 mm is the current collector, and 30 current collectors are ultrasonically welded and connected in parallel. .. The thickness of the Al current collector foil was 15 μm. When the positive electrode and the negative electrode are short-circuited at one place of one electrode, the resistance value when the current flows through the other 29 positive electrode current collector foils is the volume resistivity of Al × current path length / current path cross-sectional area. It is represented by. At this time, the resistance of the other 29 positive electrode current collector aluminum collector foils is 0.018 mΩ, assuming that the current path length is an average path length of 35 mm + 5 mm = 40 mm and the current path cross-sectional area is 140 mm × 15 μm × 29 sheets. be. The resistance of the positive electrode aluminum collector foil at the electrode with the entangled part is 0.54 mΩ when the current path length is the average path length of 35 mm + 5 mm = 40 mm and the current path cross-sectional area is 140 mm × 15 μm × 1. The sum with the other 29 sheets is 0.558 mΩ. When the thickness of Cu in the negative electrode current collector foil is 9 μm, the resistance of the negative electrode Cu current collector foil is the same as that in the case of the positive electrode. Therefore, the sum of positive / negative current collecting resistances up to the short-circuited portion is 1.116 mΩ. Assuming that only the current collector foil is the resistance, the short-circuit current when short-circuited with the resistance 0 at the maximum of 4.1V of the cell is 4.1 / 0.001116 = 3674A, and the calorific value is It will be as high as 15kW. This is 750 times larger than the short-circuit current and calorific value of the present disclosure described above. In Comparative Example 1, assuming that the battery capacity is 10 Ah, the discharge time is about 10 seconds and the battery is completely discharged. From such calculation results, it was found that in Examples 1 to 3, normal charging / discharging can be sufficiently performed, and slow discharging is possible even by a partial short circuit inside, which is extremely safe.

It should be noted that the present disclosure is not limited to the above-mentioned examples, and it goes without saying that the present disclosure can be carried out in various embodiments as long as it belongs to the technical scope of the present disclosure.

10,10B, 10C electrode structure, 11 single cell, 12,12B, 12C negative electrode, 13 negative electrode active material layer, 15 separator, 16,16B, 16C positive electrode, 17 positive electrode active material layer, 18,19 support film, 20, 20B, 20C Negative electrode current collector, 21 connection part, 23 collection wire, 30, 30B, 30C Positive electrode current collector, 31 connection part, 33 collection wire, N number, L length, t width, P pitch.

Claims (9)

A positive electrode having a positive electrode active material, a positive electrode current collector having a comb-teeth structure including a plurality of collectors adjacent to the positive electrode active material and a connection portion in which the collectors are connected in parallel,
A negative electrode having a negative electrode active material, a plurality of collector wires adjacent to the negative electrode active material, and a connection portion in which the collector wires are connected in parallel, and arranged in the opposite direction to the comb tooth structure of the positive electrode current collector. A negative electrode with a current collector, and
Electrode structure with. The electrode structure according to claim 1, wherein the current collector of the positive electrode current collector and the current collector of the negative electrode current collector are arranged at an angle. The electrode structure according to claim 2, wherein the current collector of the positive electrode current collector and the current collector of the negative electrode current collector intersect each other within a range of once or more and three times or less. Whether the positive electrode current collector satisfies P ≦ L · tan θ when the length L of the collector, the pitch P between the collectors, and the angle θ of the collector with respect to the line orthogonal to the connection portion.
Whether the negative electrode current collector satisfies P ≦ L · tan θ when the length L of the collector, the pitch P between the collectors, and the angle θ of the collector with respect to the line orthogonal to the connection portion. The electrode structure according to claim 2 or 3, wherein is one or more of the above. Whether the positive electrode current collector satisfies 3P ≧ L · tan θ, where the length L of the collector, the pitch P between the collectors, and the angle θ of the collector with respect to the line orthogonal to the connection.
Whether the negative electrode current collector satisfies P ≦ L · tan θ when the length L of the collector, the pitch P between the collectors, and the angle θ of the collector with respect to the line orthogonal to the connection portion. The electrode structure according to claim 4, wherein the electrode structure is any one or more of the above. Is the positive electrode current collector formed on a support film that does not have electron conductivity?
The electrode structure according to any one of claims 1 to 5, wherein the negative electrode current collector is formed on a support film having no electron conductivity, or is one or more. In the positive electrode current collector, the width t of the current collector is 2 mm or less, and the pitch P of the current collector is 2 mm or less.
The negative electrode current collector has any one of claims 1 to 6, wherein the width t of the current collector is 2 mm or less and the pitch P of the current collector is 2 mm or less. The electrode structure according to. Whether 100 or more of the current collectors are connected in parallel to the positive electrode current collector.
The electrode structure according to any one of claims 1 to 7, wherein the negative electrode current collector is one or more of 100 or more of the current collectors connected in parallel. The electrode structure according to any one of claims 1 to 8 and the electrode structure.
An ion conduction medium that is interposed between the positive electrode and the negative electrode and conducts ions,
Power storage device equipped with.

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