JP2007095423A - Lithium ion battery tab, its manufacturing method, and lithium ion battery using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lithium ion battery tab capable of preventing corrosion due to a hydrofluoric acid generated by an electrolyte and moisture at a sandwiching part adhered to an outer package or an adhesive film, and to provide its manufacturing method. <P>SOLUTION: The lithium ion battery tab is used for a lithium ion battery provided with a lithium ion battery body and the outer package for hermetically sealing the lithium ion battery body. The tab is connected to a cathode and an anode, and sandwiched by the outer package so that the tip is protruded to outside. The sandwiching part is heat-sealed. The tab 4 on the cathode side is formed of aluminum. The lithium ion battery tab is composed so as to provide an insulating layer 4b composed of an oxide film to the sandwiching part 7 and a part arranged inside the outer package 5 and contacting a battery electrolyte, and also, to provide a hydrogen fluoride-resistant chemical conversion treatment layer 4c so as to cover the insulating layer 4b. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a tab material for a lithium ion battery showing a stable sealing property with a packaging material, a manufacturing method thereof, and a lithium ion battery using the same.

The lithium ion battery is also referred to as a lithium secondary battery, and includes a battery having a liquid, gel-like, and polymer-like electrolyte, and a positive electrode / negative electrode active material made of a polymer. In this lithium ion battery, the lithium atom (Li) in the lithium transition metal oxide, which is the positive electrode active material, is charged as lithium ion (Li ⁺ ) during charging and enters the carbon layer of the negative electrode (intercalation). This is a battery in which charge / discharge reaction proceeds when ions (Li ⁺ ) are separated from the carbon layer (deintercalation) and move to the positive electrode to become the original lithium compound. From the nickel-cadmium battery and the nickel-hydrogen battery The output voltage is high, the energy density is high, and the apparent discharge capacity is reduced by repeating shallow discharge and recharging, so that there is no so-called memory effect. Therefore, in recent years, it has been widely used as a power source for portable devices such as mobile phones, notebook computers, digital cameras, and small video cameras.

  The composition of the lithium ion battery is as follows: positive electrode current collector (aluminum, nickel) / positive electrode active material layer (polymeric positive electrode material such as metal oxide, carbon black, metal sulfide, electrolyte, polyacrylonitrile) / electrolyte layer (propylene carbonate) , Carbonate electrolytes such as ethylene carbonate, dimethyl carbonate, ethylene methyl carbonate, inorganic solid electrolytes composed of lithium salts, gel electrolytes, etc.) / Anode active material layers (lithium metals, alloys, carbon, electrolytes, polyacrylonitrile, etc.) Molecular negative electrode material) / negative electrode current collector (copper, nickel, stainless steel) and an outer package for packaging them. As an exterior body, conventionally, a metal can obtained by pressing a metal into a cylindrical shape or a rectangular parallelepiped shape, or a bag made of a multilayer film composed of an outermost aluminum sealant layer has been used. .

  However, there have been the following problems as the exterior body of the conventional lithium ion battery. In a metal can, since the outer wall of the container is rigid, the shape of the battery itself is determined. Therefore, since the hardware side is designed in accordance with the battery, the size of the hardware using the battery is determined by the battery, and the degree of freedom in shape is lost. On the other hand, a pouch type in which the laminated body is made into a bag shape and a lithium ion battery main body is stored, or an exterior body that is embossed by pressing the laminated body, the battery is made by the battery itself like the metal can. Although there is no restriction on the degree of freedom in designing the shape of the hardware to be used, a packaging material that can sufficiently satisfy the physical properties and functions required for an exterior body of a lithium ion battery has not yet been developed.

  The physical properties and functions required for the exterior body are high moisture resistance or surface insulation, and moisture resistance is particularly important. The packaging material for a lithium ion battery is a laminate composed of at least a base material layer, a barrier layer, and a heat seal layer, and the material of each layer and the adhesive strength between the layers are necessary as an outer package of a lithium ion battery. It has been confirmed that it affects the properties. For example, if the adhesive strength between the barrier layer and the heat seal layer is insufficient, moisture may enter from the outside, and fluorination generated by the reaction between the electrolyte in the component forming the lithium ion battery and the moisture. There is a problem that dehydration (peeling) occurs between the barrier layer and the heat seal layer due to corrosion of the aluminum surface, which is the barrier layer, due to hydrogen acid, and various proposals have been made for this problem. . When the lithium ion battery main body is sealed with the exterior body, the portion including the tab portion of the lithium ion battery main body needs to be reliably sealed.

  Conventionally, as a method for reliably sealing the tab portion of a lithium ion battery, a heat seal layer having heat and heat fusion properties is selected as a packaging material for a lithium ion battery on a tab made of metal such as aluminum, copper, stainless steel, and nickel. Or, when the heat seal layer does not have heat-fusibility to the metal, heat sealing may be performed by interposing an adhesive film (tab film) in the planned sealing portion of the tab. However, no measures were taken to prevent peeling due to corrosion of the tab surface. Therefore, surface corrosion occurs due to hydrofluoric acid generated in the electrolyte solution as the contents, delamination occurs between the tab and the resin layer laminated on the tab, and the electrolyte solution is exposed to the outside. May leak. Among the tab materials, nickel and stainless steel have a low risk of being corroded by hydrofluoric acid, but aluminum has a problem that it is most easily corroded.

Therefore, various methods for improving the corrosion resistance of the surface of the tab portion and preventing the separation between the tab and the exterior body have been proposed. For example, Patent Document 1 discloses the front and back surfaces and side surfaces of the tab on which the exterior body is heat-sealed. A method is disclosed in which corrosion of the tab due to hydrofluoric acid is suppressed by phosphoric acid chromate treatment, and wettability (adhesiveness) of the tab surface is improved to improve sealing performance by heat sealing. According to the method of Patent Document 1, the heat seal layer or adhesive film layer that adheres to the tab portion is prevented from peeling off for several years required as the service life of a power source for portable equipment such as a mobile phone, and the sealing performance Can be held.

  By the way, it is known that the lithium ion battery not only has a high output voltage and energy density as described above, but also has high energy efficiency (discharge power / charge power). Is preferable. Therefore, attempts have been made to increase the capacity of lithium ion batteries for power storage such as electric vehicles. If a lithium ion battery is to be used for power storage, it is necessary to store power of several kWh to several tens of kWh.

In that case, since a high voltage is applied to the tub surface as compared with a small lithium ion battery, the chemical conversion treatment layer of Patent Document 1 is eroded by hydrofluoric acid, and a small amount of chromium in the chemical conversion treatment layer is dissolved in the electrolytic solution. There is a possibility that the sealing performance at the seal portion between the tab and the outer package will deteriorate and the positive and negative tabs may short circuit. As the lithium-ion battery becomes larger, the required service life is more than 10 years, so the surface of the tab gradually corrodes over a long period of time, and the outer package or adhesive film layer heat-sealed to the tab peels off. As a result, the sealing system is broken.
JP 2001-307715 A

  In view of the above problems, the present invention provides a tab in which a tab of a lithium ion battery is not corroded by hydrofluoric acid generated by an electrolyte and moisture in a sandwiched portion where the outer body or an adhesive film is bonded. An object of the present invention is to provide a method for forming a surface layer of a tab having corrosion resistance. Another object of the present invention is to provide a lithium ion battery having high durability and safety that ensures sealing performance even after long-term use.

  To achieve the above object, the present invention provides a positive electrode comprising a positive electrode active material and a positive electrode current collector, a negative electrode comprising a negative electrode active material and a negative electrode current collector, and an electrolyte filled between the positive electrode and the negative electrode. Including a lithium ion battery main body and an exterior body that houses the lithium ion battery main body and seals the lithium ion battery main body by heat-sealing a peripheral portion thereof, and is connected to the positive electrode. And a lithium ion battery tab that is sandwiched by the exterior body so that the tip protrudes to the outside, and the sandwiched portion is heat sealed. The tab is formed of aluminum, and at least the sandwiched portion is oxidized. An insulating layer made of a film is provided, and a hydrogen fluoride-resistant chemical conversion treatment layer is provided so as to cover the entire sandwiched portion including the insulating layer. It is characterized in Rukoto.

  According to the present invention, in the lithium ion battery tab configured as described above, the insulating layer has a thickness of 5 μm or more.

  According to the present invention, in the lithium ion battery tab having the above-described configuration, the insulating layer is formed by sealing fine holes of a porous oxide film.

  According to the present invention, in the lithium ion battery tab having the above-described configuration, the chemical conversion treatment layer is formed by a phosphoric acid chromate treatment.

  Moreover, this invention is a lithium ion battery provided with the lithium ion battery tab of the said structure.

  According to the present invention, in the lithium ion battery having the above-described configuration, an adhesive film is interposed between the sandwiched portion and the exterior body.

  The present invention also includes a slitting process in which an aluminum sheet is slit to a final use width to form a tab material, a degreasing process for degreasing the front and back surfaces and side surfaces of the tab material, and a part of the front and back surfaces and side surfaces of the tab material. An insulating layer forming step of forming an insulating layer made of an oxide film by anodizing, and a chemical conversion treatment step of forming a hydrogen fluoride-resistant chemical conversion treatment layer so as to cover at least the insulating layer It is a manufacturing method of a battery tab.

  Further, the present invention provides the method for manufacturing a lithium ion battery tab having the above-described configuration, wherein the insulating layer forming step includes an oxide film forming step in which a tab material is anodized to form a porous oxide film, and the porous oxide film And a sealing treatment step for sealing the fine holes.

  According to the first configuration of the present invention, an insulating layer made of an oxide film is provided at least on the sandwiched portion that is bonded to the exterior body or the adhesive film, and the entire sandwiched portion is covered with fluorination resistance so as to cover the insulating layer. By providing the hydrogenous chemical conversion treatment layer, corrosion of the tab due to hydrofluoric acid generated by the electrolyte and moisture is less likely to occur. Therefore, it is possible to provide a lithium ion battery tab having excellent durability that can be applied to a large-sized lithium ion battery that generates a high voltage and has a long service life.

  Further, according to the second configuration of the present invention, in the lithium ion battery tab of the first configuration, the insulating layer has a thickness of 5 μm or more, so that the insulating property of the tab can be further improved and hydrofluoric acid. Corrosion due to can be reliably prevented.

  Further, according to the third configuration of the present invention, in the lithium ion battery tab having the first or second configuration, the insulating layer is formed by sealing the micropores of the porous oxide film, thereby oxidizing. Generation of cracks can be suppressed by increasing the breakdown pressure of the film.

  Further, according to the fourth configuration of the present invention, in the lithium ion battery tab having any one of the first to third configurations, the chemical conversion treatment layer is formed by the phosphoric acid chromate treatment, whereby high hydrogen fluoride resistance And a lithium ion battery tab having a chemical conversion treatment layer having both heat resistance and stable heat sealability with the inner surface of the exterior body.

  Further, according to the fifth configuration of the present invention, by using the lithium ion battery tab having any one of the first to fourth configurations in which the corrosion resistance of the tab surface is improved by forming an insulating film, It is possible to provide a lithium ion battery with high durability and safety in which sealing performance is ensured even during a period of use.

  Further, according to the sixth configuration of the present invention, in the lithium ion battery of the fifth configuration, the adhesive film is interposed between the tab sandwiching portion and the outer package so as to adhere to the inner surface of the outer package. Heat-sealing property can be imparted to the sandwiched portion without laminating the layers, and sealing with the exterior body is possible in a stable state.

  Further, according to the seventh configuration of the present invention, after slitting the aluminum sheet to the final use width to obtain a long tab material, the front and back surfaces and side surfaces of the tab material are degreased, and the front and back surfaces of the tab material and An insulating layer made of an oxide film is formed by anodizing a part of the side surface, and a hydrogen fluoride-resistant chemical conversion treatment layer is formed so as to cover at least the insulating layer. A lithium ion battery tab that is resistant to corrosion by hydrofluoric acid and has excellent durability can be manufactured easily and at low cost.

  According to the eighth configuration of the present invention, in the method for manufacturing a lithium ion battery tab according to the seventh configuration, after the tab material is anodized to form a porous oxide film, By forming the insulating layer by sealing the fine holes, it is possible to manufacture a lithium ion battery tab that has high insulation resistance, high breakdown voltage, and few cracks.

  Hereinafter, the manufacturing method of the lithium ion battery tab of this invention and a tab material is demonstrated, referring drawings. FIG. 1A is a perspective view of a lithium ion battery of the present invention, and FIG. 1B is a perspective view showing a state in which the lithium ion battery is disassembled. As shown in FIGS. 1A and 1B, a lithium ion battery 1 is composed of a lithium ion battery body 2 and an exterior body 5, and the lithium ion battery body 2 housed in the exterior body 5 is By sealing the periphery, moisture resistance is imparted.

  The lithium ion battery body 2 includes a positive electrode composed of a positive electrode active material and a positive electrode current collector, a negative electrode composed of a negative electrode active material and a negative electrode current collector, and an electrolyte filled between the positive electrode and the negative electrode (none shown). And a tab (electrode terminal) 4 that is connected to a positive electrode and a negative electrode in the cell 3 and has a tip projecting outside the exterior body 5. The tab 4 connected to the positive electrode is made of aluminum and has a thickness of about 50 to 200 μm and a width of about 5 to 100 mm.

  FIG. 2 is an enlarged cross-sectional view showing the configuration around the positive electrode tab of the lithium ion battery. Portions common to FIG. 1 are denoted by the same reference numerals and description thereof is omitted. The exterior body 5 has a laminated structure composed of a plurality of layers, and a metal adhesive film is laminated as the innermost layer 14 to enhance the heat sealability between the metal tab 4 and the exterior body 5. The outer package 5 in which the innermost layer 14 does not have heat sealability with respect to the metal may be used. In that case, both the metal tab 4 and the innermost layer of the outer package 5 have heat sealability. It heat-seals and welds through an adhesive film (refer FIG. 5, FIG. 6).

  An insulating layer 4b (not shown) made of an oxide film, an anti-oxidation film 4b (not shown), and a portion where the outer body 5 is heat-sealed (hereinafter referred to as a sandwiching portion) 7 and a portion disposed inside the outer body 5 and in contact with the electrolyte solution, A chemical conversion treatment layer 4c made of a hydrogen fluoride layer is laminated. A positive electrode current collector 8 that electrically connects a positive electrode (not shown) and the tab 4 is coupled to the tip of the tab 4 housed in the exterior body 5. The detailed configuration of the exterior body 5 will be described later.

  The present invention is characterized in that an insulating layer 4b made of an oxide film is provided on at least the sandwiching portion 7 of the aluminum tab 4, and further a chemical conversion treatment layer 4c is provided. With this configuration, the dissolution and corrosion of the tab surface due to hydrogen fluoride (chemical formula: HF) generated by the reaction between the electrolyte of the lithium ion battery and moisture is prevented, and the innermost layer or the adhesive film of the outer package 5 It is possible to improve the adhesiveness (wetting property) with the tab 4 and to stabilize the adhesive force in the tab.

  The lithium ion battery has a pouch type using a pillow-shaped exterior body 5 as shown in FIG. 1 and an embossed portion as shown in FIG. 3 depending on the type of exterior body that wraps the lithium ion battery body. There is an embossed type in which the lithium ion battery main body 2 is hermetically housed using an exterior body 5 composed of a tray 5a and a sheet 5b, but the present invention can be applied to any type.

  Next, the configuration of the tab will be described in detail. 4A is a cross-sectional view of the lithium-ion battery tab (XX cross-section in FIG. 1), FIG. 4B is a cross-sectional view in a state of being housed in the exterior body, and FIG. 4C is a tab view of the exterior body. It is sectional drawing in the state heat-sealed with. Portions common to FIGS. 1 and 2 are denoted by the same reference numerals and description thereof is omitted. As shown in FIG. 4, the tab 4 on the positive electrode side (the left side in FIG. 4) is located on the sandwiched portion of the tab material 4a having a predetermined width and on the inside of the exterior body 5 and in contact with the electrolyte (see FIG. 2). An insulating layer 4b is formed, and a chemical conversion treatment layer 4c is stacked on the outside of the insulating layer 4b. An opening 4d is formed in the insulating layer 4b, and the tab member 4a is in contact with the chemical conversion treatment layer 4c through the opening 4d. On the other hand, in the tab 4 on the negative electrode side (the right side in FIG. 4), only the chemical conversion treatment layer 4c is formed in the sandwiched portion of the tab material 4a.

  The insulating layer 4b is formed by anodizing a predetermined portion of the aluminum tab member 4a to form an insulating oxide film. For forming the oxide film, a neutral electrolyte solution such as boric acid is used to form a barrier layer having a thickness of less than 1 μm, and an acidic or alkaline electrolyte such as sulfuric acid, oxalic acid, or sodium hydroxide is used. There is a method in which anodization, anodic dissolution, and chemical dissolution are repeated, and a porous oxide film of several μm to several tens of μm is grown on the barrier layer. In the present invention in which the insulating layer is formed by the latter method, the latter method capable of forming a porous oxide film is used.

This porous oxide film consists of a very thin barrier layer formed on the aluminum surface and a porous layer formed on the barrier layer, and a large number of micropores opening on the surface of the porous layer reach the barrier layer. is doing. Although there is no proton supply source from the aluminum side to the film side, no current flows, but H ⁺ (proton) dissociated from the electrolyte residual components and moisture flows from the film side to the aluminum side as proton current. At this time, H ⁺ becomes H ² at the interface between the film and aluminum, and there is a risk of causing a decrease in insulation resistance or withstand voltage due to mechanical film destruction due to volume expansion.

  Therefore, normally, after forming a porous oxide film, a sealing treatment is performed. As a sealing treatment method, boiling water, a hydration sealing method that seals with pressurized steam, a metal salt sealing method that seals with hot water containing a metal salt, or an organic substance such as an oil or a synthetic resin is applied or Conventionally known sealing treatments such as an organic matter sealing method immersed in an organic matter and a method of forming an inorganic film by a plasma CVD method can be used.

  If the insulating layer 4b is formed on the entire surface of the tab member 4a, the discharge from the cell 3 and the recharge to the cell 3 cannot be performed via the tab 4. Therefore, an opening 4d is provided at a predetermined location of the insulating layer 4b, and electrons are exchanged between the cell 3 and the tab material 4a through the opening 4d and the chemical conversion treatment layer 4c. The opening 4d may be provided in a pattern as shown in FIG. 4, or may be provided only in a portion where the positive electrode current collector 8 (see FIG. 2) is connected.

  The chemical conversion treatment layer 4c is formed by performing chemical conversion treatment (hereinafter referred to as phosphoric acid chromate treatment) with chromium phosphate, chromic acid or the like on at least the portion of the surface of the tab material 4a where the insulating layer 4b is provided. The In the tab 4 on the positive electrode side, the surface of the tab surface by hydrofluoric acid generated by the reaction between the electrolyte component in the lithium ion battery and moisture entering from the outside is formed by the chemical conversion treatment layer 4c and the insulating layer 4b described above. Effectively prevents corrosion and dissolution. Furthermore, the chemical conversion treatment layer 4 c also has an action of reliably heat-sealing the innermost layer 14 (see FIG. 5) of the outer package 5 or the adhesive film 6 (see FIG. 6) to the tab 4 and the tab 4.

  Next, the manufacturing method of the positive electrode side tab used for the lithium ion battery of this invention is demonstrated. First, an aluminum sheet for tab production is slit into a long tab material having a final use width using a slitter (slit process). Next, the front and back surfaces and side surfaces of the tab material slit to a predetermined width are degreased (degreasing step). Thereafter, a predetermined portion of the tab material (a sandwiched portion and a portion disposed inside the outer package 5 and in contact with the electrolytic solution) is anodized to form an insulating layer made of a porous oxide film (insulating layer forming step). Finally, a hydrogen fluoride-resistant chemical conversion treatment layer is formed so as to cover the entire sandwiched portion including the insulating layer (chemical conversion treatment step), and the lithium ion battery tab is manufactured by cutting into a predetermined length.

  When forming an aluminum sheet as a raw material for the tab material, oily components may adhere to the surface, and when cutting from a wide sheet to a tab material of a predetermined width by a slitter, to protect the cutting blade Oil used in the case may adhere. Since these oil components and oil adversely affect the subsequent formation of the insulating layer and the chemical conversion treatment layer, a degreasing process for removing the oil components and oil is necessary. In addition, before the degreasing step, a step of pretreating the surface of the tab material by buffing or the like may be provided, and a step of cleaning and dissolving the surface of the tab material by etching, desmut treatment or the like may be further provided.

  The degreasing treatment can be performed by coating the tab material with an acid or an alkali solution, or immersing the tab material in an acid or an alkali solution. Acidic substances used for degreasing include inorganic acids such as hydrochloric acid, sulfuric acid, nitric acid, hydrofluoric acid, phosphoric acid, sulfamic acid, citric acid, gluconic acid, oxalic acid, tartaric acid, formic acid, hydroxyacetic acid, EDTA (ethylenediaminetetraacetic acid) and Examples thereof include ammonium derivatives and ammonium thioglycolate.

Examples of alkaline substances include caustic soda (NaOH), soda ash (Na ₂ CO ₃ ), baking soda (NaHCO ₃ ), bow glass (Na ₂ SO ₄ .10H ₂ O), sesquicarbonate soda (Na ₂ CO ₃ .NaHCO ₃ ). ₃ · 2H ₂ O) soda salts such as, orthosilicate Cao _{(2Na 2 O · S I O} 2, 10~40% moisture), metasilicate Cao _{(2Na 2 O · S I O} 2 · 9H 2 O), one silicate No. Cao _{(Na 2 O · 2S I O} 2, water 42 to 44%), two items silicate soda _{(Na 2 O · 3S I O} 2, 65% moisture) silicates such as, primary phosphate sodium (NaH ₂ PO ₄ ), sodium pyrophosphate (Na ₄ P ₂ O ₇ ), sodium diphosphate (Na ₂ HPO ₄ ), sodium hexametaphosphate {(NaPO ₃ ) ₆ }, sodium triphosphate (Na ₃ PO ₄ ) phosphate salts such as sodium tripolyphosphate (Na ₅ P ₃ O ₁₀₎ And the like.

  The insulating layer forming step further includes a step of anodizing the tab material to form a porous oxide film (oxide film forming step), a step of sealing micropores in the porous oxide film (sealing process step), It is divided into. The oxide film forming step is performed by energizing (electrolyzing) a direct current in an electrolytic bath using a tab material (aluminum) as an anode (positive electrode) and carbon or the like as a cathode (negative electrode). At this time, aluminum on the surface of the tab material dissolves and combines with the generated oxygen to form an aluminum oxide film (anodized film).

  In the initial stage of electrolysis, a barrier layer of about 20 nm is formed on the aluminum surface. Thereafter, as the electrolysis time elapses, a porous layer grows from the barrier layer, and electrolysis is continued until a predetermined thickness is reached. As the electrolytic bath, a sulfuric acid bath, an oxalic acid bath, a chromic acid bath, a mixed acid bath of an organic acid and sulfuric acid, or the like is used, and a sulfuric acid bath with low electrolysis voltage and low power consumption is preferable. As a current waveform to be energized, direct current is generally used. However, when a good film cannot be obtained by direct current electrolysis, alternating current, orthogonal superposition, and pulse electrolysis are used. Further, by flowing a large current, dissolution of the film into the electrolytic solution can be prevented, and the film forming speed can be increased and a film having high hardness can be formed.

  Accordingly, the type, current waveform, bath temperature, stirring speed, electrolysis time, etc. of the electrolytic bath may be selected so as to be the optimum conditions according to the required layer thickness and quality of the insulating layer. In order to suppress corrosion due to hydrofluoric acid for a long period, the thickness of the anodized film (insulating layer) is preferably 5 μm or more.

  As described above, in order to ensure the conductivity of the tab, it is necessary to form an opening (see FIG. 4) through which the surface of the tab material is exposed in the oxide film. As a method for forming the opening, a resist film is formed in a pattern corresponding to the opening by printing or the like in advance, and an acidic or alkaline electrolytic solution is treated only in a necessary portion, and then the resist film is removed and oxidized. Examples include a method of forming a film, a method of immersing the entire surface in an acidic or alkaline electrolytic solution to form an oxide film on the entire surface, and then scraping off unnecessary portions.

  Then, following the oxide film forming step, a sealing treatment step for sealing the micropores of the porous layer is performed in order to suppress a decrease in insulation resistance and withstand voltage. As the sealing treatment, the above-described hydration sealing method, metal salt sealing method, organic matter sealing method, plasma CVD method and the like can be appropriately selected and used.

  In the chemical conversion treatment step, a solution composed of phosphate, chromate, fluoride, and triazine thiol compound is applied to the surface of the tab material, and the film is dried and cured by heating, irradiation with near infrared rays, etc. to form a chemical conversion treatment layer. Is. In particular, a phosphoric acid chromate treatment using an aqueous solution comprising a phenol resin, a chromium fluoride (3) compound, and phosphoric acid is suitably used as the treatment liquid.

The chemical conversion treatment method only needs to be able to treat at least the portion of the tab material provided with the insulating layer, but a dipping method in which the tab material is immersed in the chromate solution, a shower method in which the chromate solution is sprayed on the tab material, and a roll. It is desirable to process the entire circumference of the tab material using a roll coating method or the like for coating the tab material with a chromate solution. Thereafter, the chromate solution applied to the tab material is dried, and further subjected to chemical conversion treatment on the front and back surfaces and side surfaces of the tab material by baking under a temperature condition where the film temperature is 180 ° C. or higher. The coating amount of chromate solution is suitably about ^{2 to} 20 mg / m ² (dry weight). Note that the tab on the negative electrode side can be manufactured by the same method as that on the positive electrode side except for the insulating layer forming step, and thus the description thereof is omitted here.

  Next, the material of the exterior body used for the lithium ion battery of this invention is demonstrated. As shown in FIG. 5A, the laminate 10 forming the exterior body includes at least a base material layer 11, a barrier layer 12, and an innermost layer (heat seal layer) 14, and an adhesive layer 16 is provided between these layers. And laminating by a method such as a dry laminating method, a sandwich laminating method, an extrusion laminating method, or a thermal laminating method. Further, as shown in FIG. 5B, an intermediate layer 13 may be provided between the barrier layer 12 and the innermost layer 14.

  The outermost layer is made of stretched polyester or nylon film, and examples of the polyester resin include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, copolymerized polyester, and polycarbonate. Examples of the nylon resin include polyamide resins such as nylon 6, nylon 6,6, copolymers of nylon 6,6 and nylon 6, nylon 6,10, polymetaxylylene adipamide (MXD6), and the like. It is done.

  When the outermost layer is used as a lithium ion battery, the outermost layer is a portion that is in direct contact with the hardware, and thus a resin layer having insulating properties is basically preferable. Considering the existence of pinholes in a single film and the occurrence of pinholes during processing, the outermost layer needs to have a thickness of 6 μm or more, and a preferred thickness is 12 to 25 μm.

The outermost layer may be laminated in order to improve pinhole resistance and insulation when used as a battery outer package. When the outermost layer is laminated, the outermost layer includes at least one resin layer of two or more layers, and the thickness of each layer is 6 μm or more, preferably 12 to 25 μm. Examples of laminating the outermost layer include the following 1) to 7) although not shown.
1) Stretched polyethylene terephthalate / stretched nylon 2) Stretched nylon / stretched polyethylene terephthalate

In addition, mechanical suitability of packaging materials (stability of conveyance in packaging machines and processing machines), surface protection (heat resistance and electrolyte resistance), secondary processing and embossing type outer packaging for lithium ion batteries (Refer to Fig. 3) For the purpose of reducing the frictional resistance between the mold and the outermost layer during embossing, the outermost layer is multi-layered, and the surface of the outermost layer is a fluororesin layer, an acrylic resin layer, a silicone system. It is preferable to provide a resin layer or the like. For example,
3) Fluorine resin / stretched polyethylene terephthalate (Fluorine resin is a film or formed by drying after liquid coating)
4) Silicone resin / stretched polyethylene terephthalate (silicone resin is a film or formed by drying after liquid coating)
5) Fluorine-based resin / stretched polyethylene terephthalate / stretched nylon 6) Silicone-based resin / stretched polyethylene terephthalate / stretched nylon 7) Acrylic resin / stretched nylon (Acrylic resin is cured in a film or liquid coating and dried)

  As a laminating method for forming the outer package having a laminated structure, a dry laminating method, a thermal laminating method, an extrusion laminating method, a sandwich laminating method, a coextrusion laminating method, or the like can be used.

  The barrier layer 12 is a layer for preventing water vapor from entering the inside of the lithium ion battery from the outside through the exterior body 5, and stabilizes pinholes and processability (pouching, embossing) of the barrier layer alone. For example, a film having a thickness of 15 μm or more, such as aluminum or nickel, or a film on which an inorganic compound such as silicon oxide or alumina is deposited is preferable. Is aluminum of 15 μm to 100 μm.

  By using aluminum having an iron content of 0.3 to 9.0% by weight, preferably 0.7 to 2.0% by weight, as a material for the barrier layer, compared to aluminum not containing iron, Aluminum has good spreadability, and the laminated body is less likely to generate pinholes due to bending, and the side wall can be easily formed when embossing an embossed type exterior body. When the iron content is less than 0.3% by weight, effects such as prevention of pinholes and improvement in embossing formability are not observed, and the iron content of the aluminum is 9.0% by weight. When exceeding, the softness | flexibility as aluminum is inhibited and bag-making property worsens as a laminated body.

  In addition, aluminum produced by cold rolling changes its flexibility, waist strength, and hardness under annealing (so-called annealing treatment) conditions, but the aluminum used in this example is not annealed. A soft processed product having flexibility, which is appropriately annealed, is preferable to the product. The degree of flexibility, waist strength and hardness, that is, annealing conditions may be appropriately selected in accordance with processing suitability (pouching, embossing suitability). For example, in order to prevent pinholes and wrinkles during embossing, aluminum that tends to be softer and more or less annealed than hard aluminum that has not been annealed is better.

  Furthermore, a chemical conversion treatment layer 15 made of an oxide film is provided on the surface of the barrier layer 12. The chemical conversion treatment layer 15 prevents the corrosion and dissolution of the surface of the barrier layer 12 due to hydrogen fluoride generated by the electrolyte and moisture of the lithium ion battery, and improves the adhesion (wetting property) of the surface of the barrier layer 12 to provide a laminate. The adhesive force between the barrier layer 12, the base material layer 11, and the innermost layer 14 (or the intermediate layer 13) at the time of formation is stabilized.

  The innermost layer of the outer package used in the present invention is a material in which the innermost layers have heat-sealing properties and also show heat-sealing properties with respect to the metal forming the tab, and are not altered or deteriorated by the contents. As a result, the unsaturated carboxylic grafted polyethylene, the unsaturated carboxylic grafted polypropylene, the unsaturated carboxylic grafted polymethyl having a thickness of 10 μm or more, preferably 20 to 100 μm, a melting point of 80 ° C. or more, and a Vicat softening point of 70 ° C. or more. An unsaturated carboxylic graft polyolefin resin such as pentene, a metal ion cross-linked polyethylene, or a copolymer of ethylene or propylene and acrylic acid or methacrylic acid, and those containing at least one of these modified products give good results. Indicated.

  For the innermost layer, a polyolefin having no metal adhesion can also be used. In this case, an unsaturated carboxylic graft polyolefin, a metal-crosslinked polyethylene, ethylene or propylene and acrylic acid, between the electrode and the innermost layer, Alternatively, by using a heat-adhesive tab material (thickness of 15 μm or more) formed from a copolymer with methacrylic acid, the tab and the packaging material can be completely bonded and sealed. By interposing the adhesive film 6 between the tab 4 and the innermost layer 14, sealing performance can be ensured.

  As the adhesive film, it is more preferable to use a film in which a polyolefin layer in which at least one is an acid-modified polyolefin is laminated on both surfaces of a biaxially stretched polyethylene naphthalate film. In this case, since the polyethylene naphthalate film is excellent in heat resistance, it is not thinned during heat sealing, and a short circuit between the barrier layer 12 and the tab 4 can be prevented.

  As shown in FIGS. 6 (a), 6 (b), and 6 (c), the adhesive film is set on the heat seal portion between the tab 4 and the innermost layer 14 with the tab 4 (metal). ) And the innermost layer 14 (heat seal layer) may be provided with an adhesive film 6 having a sealing property, and FIGS. 7 (a), 7 (b), and 7 (c). As shown in FIG. 5, the tab 4 may be wound around a predetermined position. Examples of the adhesive film 6 include an unsaturated carboxylic acid grafted polyolefin obtained by graft-modifying a polyolefin resin with an unsaturated carboxylic acid, a metal-crosslinked polyethylene, a film made of a copolymer of ethylene or propylene and acrylic acid, or methacrylic acid. Can be used. In addition, the innermost layer 14 in the laminated body of the present invention may be a single layer made of the above resin, or may be two or more layers including the above resin.

  The unsaturated carboxylic graft polyolefin resin is suitable for any of adhesion to electrodes, heat resistance, cold resistance, and processability (pouching, embossing formability). If the thickness of the innermost layer is less than 20 μm, when the electrode is heat-sealed, a gap is formed at the end portion and the barrier property is lost. Moreover, even if the thickness of the innermost layer exceeds 100 μm, the heat seal strength does not change, and the thickness of the laminated body increases, which goes against the space-saving that is the subject of the present invention. Moreover, when melting | fusing point and Vicat softening point are low, heat resistance and cold resistance will lose | eliminate, the adhesive strength with films and an electrode will fall, and a bag will break. The various unsaturated carboxylic graft polymers may be used alone, but the properties can also be satisfied by blending two or more kinds of resins.

  For each layer of the laminate of the present invention, corona treatment and blast treatment are appropriately performed for the purpose of improving and stabilizing film forming properties, lamination processing, and final product secondary processing (pouching, embossing) suitability. Surface activation treatment such as oxidation treatment or ozone treatment may be performed.

  The outermost layer, the barrier layer, the intermediate layer, and the innermost layer of the laminate of the present invention are formed, or the lamination method between the layers is specifically a T-die method, an inflation method, a coextrusion method, or the like. To form a film. If necessary, the secondary film may be formed by a method such as coating, vapor deposition, ultraviolet curing, or electron beam curing. Moreover, as a bonding method, methods such as a dry laminating method, an extrusion laminating method, a coextrusion laminating method, and a thermal laminating method can be used.

  When laminating by the dry laminating method, polyester, polyethyleneimine, polyether, cyanoacrylate, urethane, organic titanium, polyetherurethane, epoxy, polyesterurethane, imide, isocyanate Various adhesives based on polyolefin, polyolefin, and silicone can be used. Further, these adhesive layers contain at least one of silicon oxide, calcium carbonate, zinc, red lead, lead suboxide, lead oxide, lead cyanamide, zinc chromate, barium potassium chromate, and barium zinc chromate as appropriate. Addition of an additive characterized by this further improves chemical resistance and organic solvent resistance. In particular, silicon oxide, calcium carbonate, zinc, red lead, lead suboxide, zinc oxide, lead cyanamide, zinc chromate, potassium barium chromate, barium zinc chromate, etc. are generated by the reaction of electrolyte with moisture Has the effect of preventing the corrosion of hydrogen fluoride on each layer, particularly the barrier layer (aluminum).

  In addition, when using the extrusion laminating method, polyester, polyether, urethane, polyetherurethane, polyesterurethane, isocyanate, and polyolefin can be used as an adhesion promotion method that stabilizes the adhesive strength between the layers to be bonded. , Polyethyleneimine, cyanoarylate, organotitanium compound, epoxy, imide, silicone, and their modified or mixed resin, etc. It can be carried out. Further, by using an unsaturated carboxylic acid grafted polyolefin as a resin when bonded by an extrusion laminating method or a thermal laminating method, adhesion resistance and content resistance are improved.

The lithium ion battery tab and the tab material chemical conversion treatment method of the present invention will be described with reference to examples. In the following Examples 1 and 2, the common conditions are as follows.
(1) The tab has nickel as the anode and aluminum as the cathode, and each has a width of 8 mm, a length of 50 mm, and a thickness of 100 μm.
(2) The pouch type was a pillow type, and the pouch size was an outer size, with a width of 60 mm and a length of 80 mm (both seal widths were 5 mm).
(3) The embossed type was a single-sided embossed type, the recess was 35 mm × 50 mm, the depth of the recess was 3.5 mm, and the width of the flange part (seal part) was 5 mm.
(4) The tab degreasing treatment, anodizing treatment, and chemical conversion treatment in the examples were performed on the sheet cut to the size to be attached to the lithium ion battery main body. In actual manufacturing, as described above, the metal sheet of the tab material can be processed in a slit state.

(Pouch type)
1. (Degreasing step) The tab material was immersed in a 0.1 N sulfuric acid solution for 10 seconds, washed with water and dried.
2. (Insulating layer forming step) After patterning a resist film on the surface of the aluminum tab material for the cathode, the tab material is used as an anode and carbon is used as the cathode to perform direct current electrolysis in a 20% sulfuric acid bath to form an anodized film. Formed. After washing with water, the resist film was removed, immersed in boiling water and sealed, and an insulating layer having a predetermined pattern was formed on the surface of the tab material. The nickel tab material for the anode did not form an insulating layer and proceeded directly to the next step.
3. (Chemical conversion treatment process) The tab material is dipped in an aqueous solution consisting of phenol resin, chromium (III) fluoride compound and phosphoric acid for 5 seconds and pulled up. After removing moisture with hot air, the film temperature is adjusted by a far infrared heater. It heated until it reached 190 degreeC, it joined to the cell edge part of the lithium ion battery, and it was set as the battery main body.
4). The laminated body which forms an exterior body was created as follows. Chemical conversion treatment is applied to one side of 20 μm aluminum, and a stretched polyester film (thickness: 16 μm) is bonded to the surface not subjected to chemical conversion by a dry lamination method. Next, acid modification is applied to the surface of the chemical conversion treatment aluminum and the chemical conversion treatment layer. A pouch was formed using a laminate obtained by laminating 50 μm of a polypropylene film by dry lamination to obtain an outer package.
5. The battery main body was housed in the outer package, and the unsealed portion of the main body example was heat sealed together with the tab to obtain a pouch-type lithium ion battery.

(Embossed type)
1. (Degreasing step) The tab material was dipped in a 1.0 N sodium hydroxide solution for 10 seconds, washed with water and dried.
2. (Insulating layer forming step) After patterning a resist film on the surface of the aluminum tab material for the cathode, the tab material is used as an anode and carbon is used as the cathode to perform direct current electrolysis in a 20% sulfuric acid bath to form an anodized film. Formed. After washing with water, the resist film was removed, immersed in boiling water and sealed, and an insulating layer having a predetermined pattern was formed on the surface of the tab material. The nickel tab material for the anode did not form an insulating layer and proceeded directly to the next step.
3. (Chemical conversion treatment process) After dipping for 5 seconds in an aqueous solution consisting of phenol resin, chromium (III) fluoride compound, phosphoric acid, removing moisture with hot air, the film temperature is raised to 190 ° C by a far infrared heater. It heated until it reached | attained, it joined to the cell edge part of the lithium ion battery, and it was set as the battery main body.
4). Chemical conversion treatment was applied to both sides of 40 μm aluminum, and a stretched nylon film (thickness 25 μm) was bonded to one side of the chemical conversion treatment by dry lamination, and then MDPE was heat sealed to the other side of the chemical conversion treatment aluminum. It is obtained by extruding as a molten resin film having a thickness of 30 μm as a layer, extruding and laminating the laminated surface with aluminum of the molten resin film to form a laminate, and then heating it above the softening point of MDPE. The laminate was embossed using the laminate, and the lid was cut into a predetermined size without molding to obtain an exterior body.
5. As an adhesive film, with the tabs sandwiched by acid-modified LLDPE 100 μm, the battery body is housed in the embossed part of the exterior body, the lid is covered, the periphery is heat sealed, and an embossed type lithium ion battery is obtained. Obtained.

  When the lithium ion battery of the present invention obtained in Examples 1 and 2 was used for repeated charging and discharging over a long period of time, none of the contents leaked, and the sealing performance at the sandwiched portion of the tab Was good.

  The present invention seals a lithium ion battery main body by housing a lithium ion battery main body including a positive electrode and a negative electrode, and an electrolyte filled between the positive electrode and the negative electrode, and heat-sealing the peripheral portion. A lithium ion battery tab that is used in a lithium ion battery including an exterior body, is connected to a positive electrode, is sandwiched by the exterior body so that a tip protrudes outside, and the sandwiched portion is heat sealed. Is formed of aluminum, and at least the sandwiched portion is provided with an insulating layer made of an oxide film, and a hydrogen fluoride-resistant chemical conversion treatment layer is provided so as to cover the entire sandwiched portion including the insulating layer.

  In the present invention, an insulating layer made of an oxide film is formed by anodizing the front and back surfaces and part of the side surface of the tab material obtained by slitting the aluminum sheet to the final use width, and covers the entire sandwiched portion including the insulating layer. Thus, a lithium ion battery tab is manufactured by forming a hydrogen fluoride resistant chemical conversion treatment layer.

  Thereby, in the aluminum tab where the corrosion of the tab due to the hydrofluoric acid generated by the reaction between the electrolyte and moisture is remarkable, the sandwiched portion is hardly corroded, and the sealing performance can be maintained for a long period of time. Therefore, a lithium ion battery tab that can be applied to a large-sized lithium ion battery that generates high voltage and has a long service life can be provided simply and at low cost. Further, since the insulating layer is formed of a porous oxide film, a thick oxide film can be easily formed. Further, by sealing the micropores of the porous oxide film, it is possible to suppress a decrease in insulation resistance and withstand voltage.

  In addition, by using the lithium ion battery tab of the present invention, it is possible to provide a large-sized lithium ion battery with high durability and safety suitable as a power source for energy storage or electric vehicles.

These are the perspective view and exploded perspective view of the lithium ion battery (pouch type) of the present invention. These are the expanded sectional views which show the structure of the tab periphery of the lithium ion battery of this invention. These are the perspective view and exploded perspective view of the lithium ion battery (emboss type) of the present invention. FIG. 4 is a cross-sectional view (a) of a lithium ion battery tab of the present invention, a cross-sectional view (b) in a state in which a lithium ion battery main body is housed in an exterior body, and a cross-sectional view (c) after heat-sealing a tab clamping portion. It is. These are sectional drawings which show the laminated structure of the exterior body used for this invention. These are the perspective views explaining the mounting method of the adhesive film in the heat seal of a lithium ion battery tab and an exterior body. These are perspective views explaining the other mounting methods of an adhesive film.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Lithium ion battery 2 Lithium ion battery main body 3 Cell (electric storage part)
4 Tab 4a Tab material 4b Insulating layer 4c Chemical conversion treatment layer (tab)
4d opening 5 exterior body 6 adhesive film 7 sandwiching portion 8 positive electrode current collector 10 laminate 11 base material layer 12 barrier layer 13 intermediate layer 14 innermost layer (heat seal layer)
15 Chemical conversion layer (barrier layer surface)
16 Adhesive layer

Claims (8)

A lithium ion battery body comprising: a positive electrode comprising a positive electrode active material and a positive electrode current collector; a negative electrode comprising a negative electrode active material and a negative electrode current collector; and an electrolyte filled between the positive electrode and the negative electrode;
The lithium ion battery main body is housed, and the outer peripheral body that seals the lithium ion battery main body by heat-sealing a peripheral portion thereof is used for a lithium ion battery including:
Lithium ion battery tab connected to the positive electrode and sandwiched so that the tip protrudes to the outside by the exterior body, and the sandwiched portion is heat sealed,
The tab is made of aluminum, and at least the sandwiched portion is provided with an insulating layer made of an oxide film, and a hydrogen fluoride-resistant chemical conversion treatment layer covers the entire sandwiched portion including the insulating layer. A lithium ion battery tab provided.   The lithium ion battery tab according to claim 1, wherein the insulating layer has a thickness of 5 μm or more.   The lithium ion battery tab according to claim 1 or 2, wherein the insulating layer is formed by sealing micropores of a porous oxide film.   The lithium ion battery tab according to any one of claims 1 to 3, wherein the chemical conversion treatment layer is formed by a phosphoric acid chromate treatment.   The lithium ion battery provided with the lithium ion battery tab in any one of Claims 1 thru | or 4.   The lithium ion battery according to claim 5, wherein an adhesive film is interposed between the sandwiched portion and the exterior body. Slitting the aluminum sheet into the final use width to make the tab material, and
A degreasing step of degreasing the front and back surfaces and side surfaces of the tab material;
An insulating layer forming step of forming an insulating layer made of an oxide film by anodizing a part of the front and back surfaces and side surfaces of the tab material;
And a chemical conversion treatment step of forming a hydrogen fluoride-resistant chemical conversion treatment layer so as to cover at least the insulating layer.   The insulating layer forming step includes an oxide film forming step for forming a porous oxide film by anodizing the tab material, and a sealing process step for sealing micropores in the porous oxide film. The manufacturing method of the lithium ion battery tab of Claim 7.

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