JP2019057434A - Collector and forming method of the same - Google Patents

Abstract

To provide a forming method of an electrode for a battery capable of suppressing that a projection part is projected from an active material layer and short-circuited.SOLUTION: An electrode for a battery, comprises: a collector to which a plurality of openings are provided and which forms a projection part by projecting the collector in a circumference of each opening; and an active material layer formed onto the collector. The projection part is folded and curved in the active material layer or onto an active material layer surface, an insulation layer is formed onto the active material layer, and the projection is not exposed.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a current collector used for a battery or the like and a method for forming the current collector, and more particularly to a current collector having a hole and a method for forming the current collector.

  Secondary batteries are widely used as power sources for portable devices such as mobile phones, digital cameras, and notebook PCs, and as power sources for vehicles and homes. For example, a lithium ion secondary battery having a high energy density and a light weight is an energy storage device indispensable for life.

  7 and 8 are perspective views showing an example of a stacked lithium ion secondary battery 10. The battery element 400 and the exterior container 801 which encloses it with electrolyte solution are provided. The battery element 400 in the lithium ion secondary battery 10 has a structure in which a positive electrode 800 (cathode) and a negative electrode 700 (anode) are alternately and repeatedly stacked while being separated by a separator 350, as shown in FIG. Yes.

  The positive electrode 800 is formed by forming an active material layer obtained by solidifying a positive electrode active material with a binder on a current collector, and an active material layer is formed to provide a positive electrode active material forming portion 810 and a lead portion. A positive electrode active material non-formed portion 820. Similarly, the negative electrode 700 is formed by forming an active material layer obtained by solidifying a negative electrode active material with a binder on a current collector, and includes a negative electrode active material forming portion 710 and a negative electrode active material non-forming portion 720. ing.

  Each positive electrode active material non-formation part is bundled by ultrasonic bonding etc., and becomes the positive electrode lead part 460, as shown to Fig.8 (a). Similarly, the respective negative electrode active material unformed portions 220 are also bundled to form a negative electrode lead portion 480. The positive electrode lead portion 460 and the negative electrode lead portion 480 are electrically connected to the positive electrode terminal 830 and the negative electrode terminal 840, respectively. FIG. 8B is a cross-sectional view of FIG. 8A cut so as to include the positive electrode terminal 830.

  The current collector uses a metal foil with a flat main surface. When the battery is charged and discharged, lithium ions move between the electrodes and enter the active material layer of the positive electrode or the negative electrode, and the positive electrode or the negative electrode expands and contracts. In particular, when graphite is used as the negative electrode active material, lithium penetrates between the phases of the graphite during charging, and the negative electrode expands to expand it. Further, when an alloy such as silicon is used as an active material, volume expansion occurs when it is combined with lithium during charging. On the other hand, when a layered compound such as lithium nickelate is used for the positive electrode, since the crystal structure is maintained even when lithium is released during charging, the volume is hardly reduced, and when lithium returns to the positive electrode during discharge, Almost no increase in volume is seen. Therefore, when an active material that is currently in widespread use is used, the active material layer of the negative electrode has a larger volume change due to charge / discharge than that of the positive electrode. Moreover, since the distortion due to the volume change promotes the deterioration of the binder due to repeated charge and discharge, the active material layer may be peeled off from the current collector.

  For the purpose of preventing the active material layer from being peeled off from the current collector (increasing the peel resistance), a technique for making holes in the current collector at a predetermined interval is known. In a flat current collector, since the current collector is only in contact with the active material layer on a flat surface, the active material layer may be peeled off from the current collector. When forming the current collector by coating or the like, the active material layer goes around other than the inside of the hole, that is, the flat surface, so that the peeling resistance is improved. Further, when the active material layer is formed on both surfaces of the current collector foil, the active material layer on the front surface can be integrated with the active material layer on the back surface, so that peeling or falling off due to peeling hardly occurs. In addition to etching and punching, this drilling method includes a punching method. According to this method, since the periphery of the hole becomes a convex shape (hereinafter referred to as a protruding portion) and remains without being removed by drilling, the bonding area with the active material layer is not reduced. For this reason, the peeling resistance is further improved as compared with etching and punching. As a result, the battery life and safety are improved.

  In the electrode of Patent Document 1 (Japanese Patent Laid-Open No. 2014-220042), by forming holes in the active material layer or the active material layer and the current collector, the residual stress generated by press working is removed, thereby removing the peel strength. A technique for improving the ionic conductivity is also disclosed.

In the lithium secondary battery disclosed in Patent Document 2 (Japanese Patent No. 5224020), a plurality of holes are formed in the foil-like current collector, but the current collector is left by leaving a part of the current collector that is not perforated. The strength of the body itself is increased, and the current collector is not cut when pressed or bent, and as a result, the electrode plate is less likely to break, thereby preventing an internal short circuit. In Patent Document 2, the current collector is rolled or pressed to form a hole, and a protrusion is formed around the hole. The projecting portion desirably projects to the surface side on which the mixture layer is formed.
Further, the tip may have a projecting portion having a shape spreading outward from the opening direction of the hole or a shape bent in a bowl shape. In order to obtain such a shape, in addition to the above-described drilling method, A method such as roll pressing or die pressing can be used (paragraph 0017).

Patent Document 3 (Japanese Patent Laid-Open No. 2004-79500) describes a metal plate having a large number of protrusions formed so as to protrude alternately on the front and back sides. This metal plate has c> when the area of the upper base of the protrusion is c, the area of the upper base side opening is s, the height of the punching burr is h, and the thickness of the entire electrode base material before compression is d> s ≧ 0.1 mm ² and 0.2 ≦ h / d ≦ 0.95. By doing so, it is said that the active material layer paste can be easily filled in the apertures, and the holding capacity of the mixture layer is increased (paragraphs (0018) to (0019)).

  In Patent Document 4 (Japanese Patent Laid-Open No. 20210-80128), the angle formed by the protrusion of the current collector and the flat surface of the current collector is 30 to 80 °. It is said that the anchoring effect is generated when the sloped protrusion is surrounded by the active material layer, and the adhesion between the current collector and the active material layer can be realized.

  In the current collector for a secondary battery of Patent Document 5 (Japanese Patent Laid-Open No. 11-67219), in order to make it difficult for the active material applied to the front and back surfaces of the metal foil to fall off, a through hole formed in the current collector is provided. The periphery has a complex irregular shape. Thus, the active material or the like is digged into the edge periphery of the through hole, and the adhesion between the edge periphery of the through hole and the active material or the like is improved. In patent document 3, when the burr | flash (gagged protrusion) has arisen in the periphery of a through-hole, it passes between a pair of metal smooth rolls, and it pushes into the inner wall surface of an edge periphery. It is said that the generated burrs can be removed (paragraphs (0015), (0020), and (0021)).

Japanese Patent Laid-Open No. 2014-220042 Japanese Patent No. 5224020 JP 2004-79500 A JP20210-80128 Japanese Patent Laid-Open No. 11-67219

  In Patent Document 1, since the active material is lost due to perforation, the capacity of the battery is reduced. In Patent Document 2, the protruding portion is left as it is. If the protruding portion protrudes from the active material layer, the protruding portion may damage the separator or break through the adjacent electrode when the positive electrode and the negative electrode are stacked. If the active material layer is applied thickly, the protrusions are less likely to jump out of the active material layer, but the current collector foil protrusions are not deformed by the pressing process, and the effect of improving the peel strength is reduced.

  Further, Patent Document 3 defines parameters such as the height of the protruding portion. However, since a large number of openings are formed, it cannot be said that the parameters such as the height can be sufficiently controlled for all the openings. In some cases, the protruding portion protrudes from the layer, which causes problems such as a short circuit.

  Moreover, in patent document 4, although the angle which the protrusion part of a collector and the flat surface of a collector make is 30-80 degrees, in order to form many opening parts, all angles are controlled to 30-80 degrees. This is not always possible, and if the angle is large, the protruding portion may protrude from the active material layer, leading to a short circuit or the like. In Example 3 of Patent Document 4, it is described that a part of the tip of the protrusion protrudes from the active material layer and is short-circuited when used as an electrode. Further, such a protruding portion may be a starting point of lithium deposition during charging / discharging, in addition to being in contact with the counter electrode itself, and may cause a short circuit when the deposited lithium contacts the counter electrode. .

  Moreover, in patent document 5, although the burr | flash produced in the periphery of the through-hole was pushed into the inner wall surface of an edge periphery by letting it pass through a smooth roll, it is performed before forming an active material layer on a collector. Therefore, when a thin active material layer is formed, burrs may be exposed from the active material layer.

  An object of the present invention is to solve the above-described problems, and to provide a battery electrode and a method for forming the same that can prevent a protruding portion from protruding from an active material layer and causing a short circuit.

  The present invention is for a battery comprising a current collector provided with a plurality of openings, and a current collector around the openings protruding to form a protrusion, and an active material layer formed on the current collector An electrode, wherein the protrusion is bent in the active material layer or on the surface of the active material layer, an insulating layer is formed on the active material layer, and the protrusion is not exposed. Electrode.

  According to another aspect of the present invention, there is provided a method in which a plurality of openings are provided, and a current collector around the opening protrudes to form a protrusion. Is formed in the active material layer or on the surface of the active material layer, and then an insulating layer is formed on the active material layer so that the protruding portion is not exposed. .

  According to the present invention, it is possible to suppress the protrusion from jumping out of the active material layer and short-circuiting.

It is typical sectional drawing for demonstrating the battery electrode of the 1st Embodiment of this invention. It is a schematic plan view which shows the battery electrode of the 2nd Embodiment of this invention. (A) is an example in which the opening forming part is formed in a cross shape, (b) is an example in which the opening forming part is formed excluding the peripheral part of the current collector foil, and (c) is an opening forming part in the central part of the current collector foil. In addition, an example in which an opening forming portion that connects the central portion and the peripheral portion is formed, (d) is an example in which several elongated rectangular opening forming portions are formed, and (e) is one of the opening forming portions in (d). This is an example in which the portion reaches the end of the current collector foil. It is a schematic plan view which shows the battery electrode of the 3rd Embodiment of this invention. It is typical sectional drawing which shows the electrode for batteries of the 4th Embodiment of this invention. It is a scanning electron micrograph which shows the cross section of the opening of the battery electrode of the Example of this invention. It is the figure which showed the result of having measured peel strength in the Example of this invention with experimental conditions. It is a perspective view which shows an example of the existing laminated type lithium ion secondary battery. It is a figure which shows an example of the existing laminated type lithium ion secondary battery, (a) is a perspective view, (b) is sectional drawing.

(First embodiment)
FIG. 1 is a cross-sectional view of a battery electrode 100 according to a first embodiment of the present invention. The battery electrode 100 may be a positive electrode or a negative electrode. As shown in FIG. 1 (a), the current collector foil sheet 110 (hereinafter abbreviated as the current collector foil 110) is punched to provide openings 120, and then the both sides of the current collector foil 110 are formed with a die coater or the like. Then, the active material layer 130 is applied to form the battery electrode 100. A broken line is a cross-sectional shape of the current collector foil before being punched. Due to the unevenness on the current collector foil due to the openings, depressions 140 and protrusions are formed on both surfaces of the active material layer 130. A protrusion 150 is generated around the opening 120 by the drilling process. In FIG. 1, the size of the protrusion is emphasized as compared with other portions of the current collector foil. In this embodiment, since the punching is alternately performed from both sides of the current collector foil 110, the protrusions 150 are alternately formed on both sides of the current collector foil. Most of the protrusions are in a state where the tip has an acute angle with respect to the main surface of the current collector foil. In addition, since a large number of protrusions 150 are formed, it is difficult to completely align the shapes of the openings, and protrusions 153 protruding from the active material layer 130 are generated in some places.

  After the active material layer 130 is applied and dried, as shown in FIG. 1B, press working is performed to deform the protrusions 150 and 153 and push them into the active material layer 130. The protrusions 150 and 153 are bent toward the inner side of the active material layer 130 by pressing. The shape of the tip of the protrusion is small even if it is angled with respect to the main surface of the current collector foil, flat (parallel to the main surface of the current collector foil) or saddle shape (direction toward the main surface of the current collector foil) Bent shape). The protrusion 150 that does not protrude from the active material layer 130 is also bent toward the main surface of the current collector foil. The protruding portion 153 protruding from the active material layer 130 is bent toward the main surface, but is exposed on the surface of the active material layer 130 as indicated by 153 ′ in FIG. 1B and can be caught by the separator. There is sex.

  Next, as shown in FIG. 1C, an insulating layer 170 serving as a protective film is applied to both surfaces of the active material layer 130 and dried to form one battery electrode for positive electrode or negative electrode. The Even when the above-described pressing is performed, the tip of some of the protrusions 153 ′ is exposed on the surface of the active material layer 130. However, when the insulating layer 270 is applied and coated, it is not exposed.

  In this way, a positive electrode and a negative electrode are formed, separated by separators (not shown) and alternately laminated repeatedly, and the active material non-formed portions are bundled and ultrasonically bonded to form a positive electrode lead portion and a negative electrode lead portion. Then, it encloses with electrolyte solution in an exterior container, only the positive / negative lead part is exposed from an exterior container, and it welds with a positive electrode terminal and a negative electrode terminal.

  By applying the active material layer 130 to the punched current collector foil 110 and then pressing it, the heights of the protrusions 150 and 153 due to the deformation of the current collector foil 110 were reduced and jumped out of the active material layer. The protruding portion 153 is accommodated in the active material layer 130, and as a result, the possibility of damaging the separator or causing a short circuit by breaking through the separator and contacting an adjacent counter electrode is reduced. In addition, the angle of the tip of the projecting portion becomes small, parallel or saddle-shaped, the anchor effect is increased, and the adhesive force of the active material layer to the current collector foil is improved. Furthermore, by covering with the insulating layer 270, the protruding portion 153 'exposed from the active material layer even when pressed is not exposed to the surface of the electrode, and safety is improved. In the case where only the protrusion 150 that does not protrude from the active material layer due to the balance between the height of the protrusion and the thickness of the active material layer and there is only the protrusion 150 within the active material layer, only the protrusion 153 that protrudes from the active material layer In the case of, both may be mixed. This embodiment is effective in any case.

  Note that an active material having a large capacity per unit mass may be used for the purpose of designing the energy density of the battery to be high. Such high-capacity active material is present in many negative electrode active materials. For example, when a silicon metal compound or silicon oxide is used, the coating thickness of the negative electrode becomes thin, and it is difficult to maintain coating accuracy. Therefore, the protrusion of the protrusion from the active material layer occurs more frequently at the negative electrode. Although this embodiment can be applied to both the positive electrode and the negative electrode, for this reason, it is more effective when applied to the negative electrode.

  In the present embodiment, the protrusions are formed on both sides of the current collector foil, but may be formed only on one side.

The battery constituted by the battery electrode of the present embodiment can suppress short-circuit between electrodes and separation of the active material layer from the current collector, and therefore can be used for applications that require high reliability such as an electric vehicle. it can.
(Second Embodiment)
FIG. 2 is a schematic plan view for explaining a second embodiment of the present invention. In the present embodiment, the current collector foil sheet described in the first embodiment is used, and the opening and the protruding portion are provided in a part rather than the entire current collector foil sheet.

  As described in FIG. 8, the storage battery is formed by alternately laminating positive and negative battery electrodes to form a battery element, which is then placed in an outer container, injected with an electrolyte from a liquid injection port of the outer container, and then sealed. As the electrolytic solution is injected, the electrolytic solution enters the gap between the active material layer and the separator by capillary action, and replaces the air present there. It is desirable that the electrolytic solution is sufficiently infiltrated so that the entire battery element is impregnated with the electrolytic solution. However, since the gap between the active material layer and the separator is very narrow, it is difficult for the electrolyte to enter the center of the battery element. It takes time to penetrate. If the opening is formed in the current collector foil, the impregnation of the electrolytic solution is accelerated, but if the opening is formed in the entire current collector foil sheet, the strength of the battery electrode is reduced. Furthermore, in the periphery of the electrode, cracks may occur in the current collector foil due to expansion / contraction due to charge / discharge.

  Therefore, in the present embodiment, as shown in FIG. 2A, a region having an opening and a protruding portion (opening forming portion 202) is formed in a cross shape with respect to the sheet of the current collector foil 210. More specifically, the elongated rectangular opening forming portion 202 is formed so as to pass from the end portion on the side of the positive electrode lead portion 215 (or the negative electrode lead portion) of the current collector foil 210 to the end portion on the opposite side. Two opening forming portions 202 having the same elongated shape are formed so as to intersect with each other from the other end portion of the current collector foil 210 to the opposite end portion.

  Further, as shown in FIG. 2B, an opening may be formed in a region excluding the peripheral portion of the current collector foil 210.

  As shown in FIG. 2B, when there is no opening forming portion in the peripheral portion of the current collector foil 210, the electrolytic solution is less likely to penetrate from the periphery to the central portion when impregnated with the electrolytic solution, as compared with a case where there is no opening. Become. Therefore, as shown in FIG. 2C, an opening forming portion 202 is formed in the central portion of the current collector foil, and a thin opening forming portion 223 that connects two end portions having no lead portion and the opening forming portion in the central portion is formed. Form. If it does in this way, it will become easy for electrolyte solution to enter into a center part from the circumference.

  Further, as shown in FIG. 2D, several elongated rectangular opening forming portions 202 are formed from the end without the positive electrode lead portion (or the negative electrode lead portion) to the opposite end portion except for both ends. It may be.

  2E shows a part of the opening forming portion 202 of FIG. 2D as an opening forming portion 204 that reaches the end of the current collector foil, and the five opening forming portions 202 are replaced by the opening forming portion 205. Connected.

  According to the present embodiment, it is possible to suppress the protrusion from jumping out of the active material layer and to short-circuit, and to improve the strength of the electrode without greatly impairing the impregnation property of the electrolytic solution. In addition, the occurrence of cracks in the active material layer in the electrode periphery can be suppressed. If the opening forming portion reaches the end of the current collector foil as shown in FIGS. 2A, 2C and 2E, the penetration of the electrolyte into the central portion is fast.

A plurality of positive electrode lead portions and negative electrode lead portions are bundled and ultrasonically bonded, and the bonded portions are welded to the positive electrode terminal and the negative electrode terminal, respectively. Therefore, it is desirable not to form openings in the positive electrode lead portion, the negative electrode lead portion, and the periphery thereof, in the portions used for joining and welding and the portions subjected to stress by joining, welding, use, transportation, and the like.
(Third embodiment)
FIG. 3 is a schematic plan view for explaining a battery electrode according to a third embodiment of the present invention. This embodiment uses the current collector foil sheet described in the first embodiment, and is common to the second embodiment in that openings are provided in a part rather than the entire current collector foil sheet. However, in this embodiment, the opening forming portion 302 is provided in the peripheral portion of the negative electrode current collector foil 310. Taking a lithium ion battery as an example, the capacity of the negative electrode is often made larger than the capacity of the positive electrode in order to prevent deposition of Li metal on the negative electrode. If the ratio of negative electrode capacity to positive electrode capacity (A / C balance: charge capacity ratio of anode (negative electrode) and cathode (positive electrode) (negative electrode charge capacity / positive electrode charge capacity) is too close to 1, due to variations in manufacturing, etc. It may be locally 1 or less, and the volume expansion of the negative electrode at the time of full charge increases when the A / C balance is close to 1. This expansion coefficient is small in the carbon negative electrode, but an alloy system such as silicon In the case of the negative electrode active material, the expansion coefficient is several times that of the carbon negative electrode, and strain is accumulated in the peripheral portion of the electrode.
On the other hand, even if the A / C balance is made larger than 1, a wasteful capacity that does not contribute to charging / discharging is held. According to the present embodiment, in the electrode peripheral portion provided with the opening, since the active material enters the opening, it is possible to give a margin to the A / C balance, and the expansion is relaxed in the portion where the strain is most accumulated. be able to.
(Fourth embodiment)
FIG. 4 is a schematic plan view for explaining a battery electrode 401 according to the fourth embodiment of the present invention. The current collector 410 is provided with a plurality of openings 420, and a protrusion 450 is provided around the opening 420. An active material layer 430 is formed over the current collector 410. The protrusion 450 is bent in the active material layer or on the surface of the active material layer, and the insulating layer 470 is formed on the active material layer 430 so that the protrusion 450 is not exposed.

Since the protrusion 450 is bent, the height of the protrusions 450 and 453 due to the deformation of the current collector 410 is reduced, and the protrusion 453 protruding from the active material layer is accommodated in the active material layer 430, and as a result. The possibility of damaging the separator or causing a short circuit with the adjacent electrode is reduced.
(Electrode constituent material)
Here, the material constituting the electrode will be described including the insulating layer. The following is an example, and the material is not particularly limited, and a known material can be used.

  Aluminum, gold, platinum, or the like can be used as a material for the positive electrode current collector. The material of the current collector for the negative electrode is the same as the material for the positive electrode, but in particular, copper, iron, nickel, chromium and molybdenum based stainless steel, aluminum, aluminum alloy, platinum, gold, palladium, iridium, rhodium, etc. should be used. Can do.

Examples of the positive electrode active material include LiNiO ₂ , Li _y Ni _(1-x) M _x O ₂ (formula A) (where 0 ≦ x <1, 0 <y ≦ 1.2, M is Co And at least one element selected from the group consisting of Al, Mn, Fe, Ti, and B).

Also, for example, Li _α Ni _β Co _γ Mn _δ O ₂ (0 <α ≦ 1.2, preferably 1 ≦ α ≦ 1.2, β + γ + δ = 1, β ≧ 0.7, γ ≦ 0.2), Li _α Ni _β Co _γ Al _δ O ₂ (0 <α ≦ 1.2, preferably 1 ≦ α ≦ 1.2, β + γ + δ = 1, β ≧ 0.6, preferably β ≧ 0.7, γ ≦ 0.2), etc. In particular, LiNi _β Co _γ Mn _δ O ₂ (0.75 ≦ β ≦ 0.85, 0.05 ≦ γ ≦ 0.15, 0.10 ≦ δ ≦ 0.20) may be mentioned. More specifically, for example, LiNi _0.8 Co _0.05 Mn _0.15 O ₂ , LiNi _0.8 Co _0.1 Mn _0.1 O ₂ , LiNi _0.8 Co _0.15 Al _0.05 O _{2, LiNi} 0.8 _Co 0.1 _Al can be preferably used 0.1 _{O 2} or the like. Note that when the Ni content is increased (for example, exceeding 0.6), the energy density of the battery can be increased, but the present invention is effective even in such a case.

  In addition, two or more compounds represented by the above (formula A) may be used as a mixture, for example, NCM532 or NCM523 and NCM433 in the range of 9: 1 to 1: 9 (as a typical example) 2: 1) are also preferably used as a mixture. Furthermore, in (Formula A), a material having a high Ni content (x is 0.4 or less) and a material having a Ni content not exceeding 0.5 (x is 0.5 or more, for example, NCM433) are mixed. As a result, a battery having a high capacity and high thermal stability can be formed.

Other than the above, as the positive electrode active material, for example, LiMnO ₂ , Li _x Mn ₂ O ₄ (0 <x <2), Li ₂ MnO ₃ , Li _x Mn _1.5 Ni _0.5 O ₄ (0 <x < 2) Lithium manganate having a layered structure or spinel structure such as LiCoO ₂ or a part of these transition metals replaced with another metal; Li in these lithium transition metal oxides more than the stoichiometric composition And those having an olivine structure such as LiFePO ₄ . Furthermore, a material in which these metal oxides are partially substituted with Al, Fe, P, Ti, Si, Pb, Sn, In, Bi, Ag, Ba, Ca, Hg, Pd, Pt, Te, Zn, La, etc. Can also be used. Any of the positive electrode active materials described above can be used alone or in combination of two or more.

  The negative electrode active material contains a metal and / or metal oxide and carbon as a negative electrode active material. Examples of the metal include Li, Al, Si, Pb, Sn, In, Bi, Ag, Ba, Ca, Hg, Pd, Pt, Te, Zn, La, or alloys of two or more thereof. . Moreover, you may use these metals or alloys in mixture of 2 or more types. These metals or alloys may contain one or more non-metallic elements.

  Examples of the metal oxide include silicon oxide, aluminum oxide, tin oxide, indium oxide, zinc oxide, lithium oxide, and composites thereof. In this embodiment, it is preferable that tin oxide or silicon oxide is included as the negative electrode active material, and it is more preferable that silicon oxide is included. This is because silicon oxide is relatively stable and hardly causes a reaction with other compounds. Moreover, 0.1-5 mass% of 1 type, or 2 or more types of elements chosen from nitrogen, boron, and sulfur can also be added to a metal oxide, for example. By carrying out like this, the electrical conductivity of a metal oxide can be improved. In addition, the electrical conductivity can be similarly improved by coating a metal or metal oxide with a conductive material such as carbon by a method such as vapor deposition.

  Examples of carbon include graphite, amorphous carbon, diamond-like carbon, carbon nanotube, or a composite thereof. Here, graphite with high crystallinity has high electrical conductivity, and is excellent in adhesiveness and voltage flatness with a negative electrode current collector made of a metal such as copper. On the other hand, since amorphous carbon having low crystallinity has a relatively small volume expansion, it has a high effect of relaxing the volume expansion of the entire negative electrode, and deterioration due to non-uniformity such as crystal grain boundaries and defects hardly occurs.

  Metals and metal oxides are characterized by a lithium acceptability that is much greater than that of carbon. Therefore, the energy density of the battery can be improved by using a large amount of metal and metal oxide as the negative electrode active material. In order to achieve a high energy density, it is preferable that the content ratio of the metal and / or metal oxide in the negative electrode active material is high. A larger amount of metal and / or metal oxide is preferable because the capacity of the whole negative electrode increases. The metal and / or metal oxide is preferably contained in the negative electrode in an amount of 0.1% by mass or more of the negative electrode active material, more preferably 1% by mass or more, and still more preferably 10% by mass or more. However, the metal and / or metal oxide has a large volume change when lithium is occluded / released compared to carbon, and the electrical connection may be lost. It is below mass%. As described above, the negative electrode active material is a material capable of reversibly receiving and releasing lithium ions in accordance with charge and discharge in the negative electrode, and does not include other binders.

  The insulating layer preferably has heat resistance, and is made of a heat resistant resin such as engineer plastic or an inorganic material such as a metal oxide. It is also possible to use these materials as insulating fillers to form an insulating layer containing a binder that binds the insulating filler. When the insulating layer formed on the positive electrode is installed on a positive electrode containing a lithium nickel composite oxide having a high nickel content as the positive electrode active material, the constituent material of the insulating layer preferably has oxidation resistance. .

  Examples of inorganic materials include metal oxides and nitrides, specifically, aluminum oxide (alumina), silicon oxide (silica), titanium oxide (titania), zirconium oxide (zirconia), magnesium oxide (magnesia), Zinc oxide, strontium titanate, barium titanate, aluminum nitride, silicon nitride and the like can be mentioned. However, since they do not melt, it is preferable to use them together with the above binder as inorganic particles. Compared to organic particles, inorganic particles are preferable because they have oxidation resistance.

  Examples of the organic material include polyimide, polyamideimide, polyphenylene sulfide, polysulfone, polyethersulfone, polyetherimide, polyetheretherketone, and silicone rubber. About the material which can be melt | dissolved and coated in an organic solvent, the formation of an insulating layer is preferable compared with an inorganic particle. An organic material is preferable in that the weight of the battery can be reduced because the specific gravity is lower than that of the inorganic material.

  When a binder is used for the positive electrode active material, the negative electrode active material, and the insulating layer, the positive electrode active material and the binder for the insulating layer formed on the positive electrode are preferably those having excellent oxidation resistance, and obtained by molecular orbital calculation. It is preferable that the HOMO (Highest Occupied Molecular Orbit) value is small. Polymers containing halogen such as fluorine and chlorine are excellent in oxidation resistance, and are therefore suitable for the binder used in this embodiment. More specifically, such binders include polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE), polyhexafluoropropylene (PHFP), polytrifluoroethylene chloride (PCTFE), polypar. Examples include polyolefins containing fluorine or chlorine such as fluoroalkoxyfluoroethylene.

  In addition, a binder used for binding the electrode mixture layer may be used.

  The coating liquid (slurry) used when coating the positive electrode active material, the negative electrode active material, and the insulating layer on the current collector foil is an aqueous solvent (water or a mixed solvent containing water as a main component as a binder dispersion medium). When the solution used is used, a polymer that is dispersed or dissolved in an aqueous solvent can be used. Examples of the polymer that is dispersed or dissolved in the aqueous solvent include acrylic resins. As the acrylic resin, a homopolymer obtained by polymerizing monomers such as acrylic acid, methacrylic acid, acrylamide, methacrylamide, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, methyl methacrylate, ethylhexyl acrylate and butyl acrylate. Is preferably used. The acrylic resin may be a copolymer obtained by polymerizing two or more of the above monomers. Further, a mixture of two or more of the above homopolymers and copolymers may be used. In addition to the acrylic resins described above, polyolefin resins such as styrene butadiene rubber (SBR) and polyethylene (PE), polytetrafluoroethylene (PTFE), and the like can be used. These polymers can be used alone or in combination of two or more. The form of the binder is not particularly limited, and a particulate (powdered) form may be used as it is, or a solution or emulsion prepared may be used. Two or more binders may be used in different forms.

  The coating liquid can contain materials other than the above-described materials as necessary. Examples of such materials include various polymer materials that can function as a thickener for the coating liquid described later. In particular, when an aqueous solvent is used, it is preferable to contain a polymer that functions as the thickener. As the polymer that functions as the thickener, carboxymethyl cellulose (CMC) and methyl cellulose (MC) are preferably used.

  The operation of mixing the positive electrode active material, the negative electrode active material, the insulating filler, and the binder into the solvent includes ball mill, homodisper, dispermill (registered trademark), Claremix (registered trademark), and fillmix (registered trademark). It can be carried out using an appropriate kneader such as an ultrasonic disperser.

  The operation of applying the insulating layer forming coating liquid can be used without any particular limitation on existing general application means. For example, it can be applied by coating a predetermined amount of coating material for forming an insulating layer to a uniform thickness using a suitable coating device (gravure coater, slit coater, die coater, comma coater, dip coat, etc.).

  Thereafter, the coating material is dried (for example, 140 ° C. or lower, for example, 30 to 110 ° C.) by an appropriate drying means, thereby removing the solvent in the insulating layer forming paint.

  In the electrode according to the present embodiment, a coating solution containing an active material, a binder and a solvent is applied to a current collector foil having a protruding shape, dried, pressed, and further coated with a coating solution for an insulating layer It can be produced by drying and pressing as necessary.

Examples of the present invention will be described below. Example 1-3 and Comparative Example 1-3 are cases where an active material layer is formed on the current collector foil. In addition, Example 4-6 and Comparative Example 4-6 are cases where an active material layer was formed on the current collector foil and an insulating layer was further formed.
Example 1
Examples of the present invention will be described below. The current collector foil is a perforated aluminum foil having a thickness of 15 μm and used for the positive electrode. The height of the projecting portion by drilling (height from the flat surface of the current collector foil) is 20 μm on average, and approximately 10,000 per square centimeter are formed by alternately drilling from both sides of the aluminum foil.
An active material layer was coated on one side of the current collector foil. As the material, LiNi _0.8 Co _0.15 Al _0.05 O ₂ was weighed in a mass ratio of carbon black, polyvinylidene fluoride and 93: 2: 5, mixed with N-methylpyrrolidone (NMP), and slurry It was. The mass ratio of NMP to solid content was 50:50. This slurry was applied to an aluminum foil having a thickness of 15 μm using a doctor blade. The aluminum foil coated with this slurry was heated at 120 ° C. for 5 minutes to dry the NMP, and the current collector foil was pressed on a metal roller and pressed from above and below. The pressing speed was 1 mm / sec. In this way, a positive electrode was produced. FIG. 5 shows a scanning electron micrograph around the opening of the electrode after pressing. It can be seen that the tip of the protrusion (inside the broken line) is bent and has a saddle shape or a flat shape. The diameter of the opening shown in FIG. 5 is about 40 μm at the spread base and about 10 μm at the protruding tip.

FIG. 6 shows the thickness of the mixture layer (value read from the cross-sectional photograph of the electrode), basis weight (weight of the active material layer per unit volume of the mixture layer), density (roll calculated from the thickness and basis weight of the mixture layer) The weight of the active material layer per unit volume of the active material layer after pressing) and the peel strength measurement results are shown.
[Comparative Example 1]
Example 1 is the same as Example 1 except that an aluminum foil that has not been punched is used as the current collector foil. Comparison between Example 1 and Comparative Example 1 in FIG. 6 compares the case where the current collector foil is opened (“with hole processing” in FIG. 6) and the case where the current collector foil is “without hole processing”. When there was an opening, the peel strength was 67 mN / mm compared to when there was no opening, which was improved from 50 mN / mm when there was no opening. From FIG. 5 of Example 1, it was inferred that the active material layer buried the protrusions and the peel strength was improved by the anchor effect. Moreover, it was guessed that the mixture layer became more difficult to peel off because the protruding portion of the current collector foil was bent in the center direction of the hole to further improve the anchor effect.
(Example 2)
The current collector foil is a perforated copper foil having a thickness of 10 μm and used for the negative electrode. The shape of the holes and the number of holes are the same as in the first embodiment. An active material layer was coated on one side of the current collector foil. The material is a composite in which the surface of SiO _x is coated with a carbon material (the amount of the carbon material in the composite is 7% by mass) and a polyamic acid solution (trade name: “U-varnish A”, manufactured by Ube Industries, Ltd., Polyamic acid (20% by mass) and the additive were weighed at a mass ratio of 50:50, respectively. These and n-methylpyrrolidone (NMP) were kneaded to form a slurry. In addition, the material of Si alone can also be used and can be made thinner. The copper foil coated with the slurry was heated at 120 ° C. for 5 minutes to dry the NMP, and the current collector foil was pressed on a metal roller and pressed from above and below. Then, it heated at 150 degreeC for 2 hours in nitrogen atmosphere, and produced the negative electrode. FIG. 6 shows the measurement results.
[Comparative Example 2]
Example 2 is the same as Example 2 except that a copper foil that has not been punched is used as the current collector foil.
The case of opening (“with hole processing” in FIG. 6) and the case of not opening (“without hole processing” in FIG. 6) are shown in comparison. When there was an opening, the peel strength was 140 mN / mm compared to when there was no opening, which was improved from 100 mN / mm when there was no opening. Also in the negative electrode of Example 2, as with the positive electrode of Example 1, it was assumed that the protruding portion of the current collector foil was bent and the mixture layer was difficult to peel off.
(Example 3)
A negative electrode was prepared in the same manner as in Example 2 except that the active material was applied on both sides. The slurry obtained in Example 2 was applied to one side of the electrode, and the NMP was dried on the electrode. Subsequently, the slurry was applied to the back side to dry the NMP, and the current collector foil was pressed on a metal roller and pressed from above and below. Then, it heated at 150 degreeC for 2 hours in nitrogen atmosphere, and produced the positive electrode. FIG. 6 shows the measurement results.
[Comparative Example 3]
Example 3 is the same as Example 3 except that a copper foil that has not been punched is used as the current collector foil. The case of opening (with hole machining in FIG. 6) and the case of not opening (without hole machining in the same figure) are shown in comparison. When there was an opening, the peel strength was 200 mN / mm, compared with 115 mN / mm when there was no opening.

In Example 3, it was presumed that the anchor effect was further increased because the mixture layers on both sides were bonded via holes, and the peel strength was improved as compared with Example 2.
Example 4
An insulating layer was applied on the electrode of Example 1. Alumina particles (average particle size 0.1 μm) are weighed at a mass ratio of polyvinylidene fluoride and 90:10, mixed with N-methylpyrrolidone (NMP) to form a slurry, and this is applied onto the electrode of Example 1 did. The positive electrode coated with the slurry was heated at 120 ° C. for 5 minutes to dry the NMP, and the current collector foil was pressed on a metal roller and pressed from above and below. The basis weight after drying of the insulating layer was about 1.5 mg / cm ² . When the thickness of the insulating layer at this time was observed with a cross-sectional SEM (Scanning Electron Microscope), it was 5 μm. This electrode was sandwiched between a pair of flat terminals (diameter 25 mm), and when the resistance between the surface on the insulating layer side and the current collector foil was measured, it was insulated (> 1 kΩ).
(Example 5)
Example 4 is the same as Example 4 except that the thickness of the insulating layer is 3 μm. When this electrode was sandwiched between flat plates and the resistance between the surface on the insulating layer side and the current collector foil was measured, it exceeded 1 kΩ and was insulated.
(Example 6)
Example 4 is the same as Example 4 except that the thickness of the insulating layer is 2 μm. When this electrode was sandwiched between flat plates and the resistance between the surface on the insulating layer side and the current collector foil was measured, it exceeded 1 kΩ and was insulated.
[Comparative Example 4]
The electrode of Comparative Example 2 was sandwiched between a pair of flat plates as in Example 4, and the resistance between the surface of the mixture layer side and the current collector foil was measured and found to be 360 mΩ.
[Comparative Example 5]
The electrode of Example 1 was sandwiched between a pair of flat plates as in Example 4, and the resistance between the surface of the mixture layer and the current collector foil was measured to be 50 mΩ.
[Comparative Example 6]
Example 4 is the same as Example 4 except that the thickness of the insulating layer is 1 μm. The electrode was sandwiched between flat plates, and the resistance between the surface on the insulating layer side and the current collector foil was measured and found to be 100 mΩ.

  The results of Comparative Examples 4, 5, and 6 indicate that when a perforated current collector foil having a protrusion is used, the protrusion is exposed on the surface of the current collector foil, and insulation cannot be maintained. However, as shown in Examples 4 to 6, the insulating properties could be maintained by pressing the mixture layer after coating and further applying an insulating coat. However, as shown in Comparative Example 6, if the thickness of the insulating layer is 1 μm or less, sufficient insulation cannot be maintained.

A part or all of the above-described embodiment can be described as in the following supplementary notes, but is not limited thereto.
(Appendix 1)
A battery electrode comprising a current collector provided with a plurality of openings and a current collector around the openings projecting, and an active material layer formed on the current collector, wherein the projecting portion is the An electrode for a battery, wherein the electrode is bent in an active material layer or on the surface of the active material layer, an insulating layer is formed on the active material layer, and the protruding portion is not exposed.
(Appendix 2)
The battery electrode according to appendix 1, wherein the opening is formed by punching the current collector.
(Appendix 3)
The battery electrode according to appendix 1 or 2, wherein the protruding portion is bent in a bowl shape.
(Appendix 4)
The battery electrode according to any one of appendices 1 to 3, wherein the protruding portion and the active material layer are formed on both surfaces of the current collector.
(Appendix 5)
The battery electrode according to any one of appendices 1 to 4, wherein the plurality of openings and the protrusions are formed in a region excluding a peripheral portion of the current collector.
(Appendix 6)
The areas having the plurality of openings and the protrusions are formed in a cross shape in the current collector, and at least a part of the end of the cross is connected to the peripheral part of the current collector. The battery electrode according to any one of the above.
(Appendix 7)
The plurality of openings and the protrusions are formed in the periphery of the current collector, and the openings and the protrusions are not formed in the center of the current collector. The electrode for a battery as described.
(Appendix 8)
The battery electrode according to any one of appendices 1 to 7, wherein the insulating layer has a thickness of 2 μm or more.
(Appendix 9)
The battery electrode according to any one of appendices 1 to 8, wherein the insulating layer includes inorganic particles or a heat-resistant resin.
(Appendix 10)
A battery comprising the battery electrode according to any one of appendices 1 to 7.
(Appendix 11)
An electric vehicle comprising the battery according to appendix 10.
(Appendix 12)
The active material layer formed on the current collector on which the plurality of openings are provided and the current collector around the opening protrudes is pressed, and the protruding portion is formed in the active material layer or the active material layer A method for forming an electrode for a battery, comprising bending the surface and then forming an insulating layer on the active material layer so that the protruding portion is not exposed.
(Appendix 13)
The method for forming a battery electrode according to appendix 12, wherein the active material layer is applied, dried, and then the protruding portion is pressed.

100, 401 Battery electrode 110, 210, 310 Current collector foil 120 Opening 130 Active material layer 140 Depression 150, 153, 153 ′ Protruding part 170 Insulating layer 202, 204, 205, 223, 302 Opening forming part 215, 460 Positive electrode lead Part 700 negative electrode 710 negative electrode active material forming part 720 negative electrode active material non-forming part 800 positive electrode 810 positive electrode active material forming part 820 positive electrode active material non-forming part

Claims (10)

  A battery electrode comprising a current collector provided with a plurality of openings and projecting around the openings, and an active material layer formed on the current collector, wherein the protrusion An electrode for a battery, wherein a portion is bent in the active material layer or on the surface of the active material layer, an insulating layer is formed on the active material layer, and the protruding portion is not exposed.   The battery electrode according to claim 1, wherein the opening is formed by punching the current collector.   The battery electrode according to claim 1, wherein the protrusion is bent in a bowl shape.   The battery electrode according to any one of claims 1 to 3, wherein the protruding portion and the active material layer are formed on both surfaces of the current collector.   The battery electrode according to any one of claims 1 to 4, wherein the plurality of openings and the protrusions are formed in a region excluding a peripheral portion of the current collector.   The region having the plurality of openings and the protruding portion is formed in a cross shape in the current collector, and at least a part of an end of the cross-shaped region is connected to a peripheral portion of the current collector. The battery electrode according to any one of 1 to 4.   5. The plurality of openings and the protrusions are formed in a peripheral portion of the current collector, and the openings and the protrusions are not formed in a central portion of the current collector. The electrode for a battery as described in.   A battery comprising the battery electrode according to claim 1.   A plurality of openings are provided, and a current collector around the opening protrudes to form a protruding portion, and the active material layer formed on the current collector is pressed. A method for forming an electrode for a battery, wherein the battery electrode is bent inside or on the surface of the active material layer, and then an insulating layer is formed on the active material layer so that the protruding portion is not exposed.   The method for forming a battery electrode according to claim 9, wherein the projecting portion is pressed after the active material layer is applied and dried.

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