JP2649729B2 - Manufacturing method of cylindrical lithium battery - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a cylindrical spiral battery formed by winding a belt-like positive / negative electrode plate via a separator containing an electrolyte.

[Prior art and its problems] A cylindrical spiral lithium battery is composed of an electrode group in which positive and negative bipolar plates are spirally wound via a separator. Also, various methods are known as the forming method. For example, a positive electrode mixture sheet is wrapped in a bag-shaped separator, and a negative electrode plate is further stacked and wound in a spiral shape, then housed in a battery case, and a liquid electrolyte is injected into the battery case to form a separator. A method of impregnating and forming a battery is known.

In general, a spiral-wound lithium battery is used for a large discharge current, so it is essential to reduce the internal resistance as much as possible. Therefore, as the separator, for example, a microporous resin film obtained by stretching a polypropylene film is used.

By reducing the thickness of the separator part, the resistance of the electrolyte part is reduced, and furthermore, the size of the spiral electrode group housed in the same battery container is increased and the electrode area is increased, so that the discharge current is increased. It is valid.

However, after laminating the electrode plate and the separator, in the winding step, a wrinkle is formed on the separator, and the distance between the electrode plates is increased, so that a problem of increasing the internal resistance is likely to occur. Also, in the step of impregnating with the liquid electrolyte after the spiral shape, air bubbles are generated in the inside, which is likely to cause trouble.

Various methods have been already disclosed to solve these problems. For example, there are the following methods.

JP-A-60-41772 (the major axis direction of the micropores of the separator film is made to match the winding direction of the spiral battery), JP-A-60-79672 (the end of the separator is welded and fixed to the current collector) JP-A-60-74267 (using a separator reinforcing sheet), JP-A-62-139253 (MnO ₂ has a small particle size), JP-A-63-164170 (winding using a holding plate), etc. It has been known. However, the improvement by these methods cannot be said to be sufficient, and the process becomes complicated.

Accordingly, an object of the present invention is to provide a simple method for producing a spiral lithium battery having excellent performance by improving a conventional method for manufacturing a spiral lithium battery.

[Means for Solving the Problem] The present invention relates to a spiral battery in which a belt-like positive / negative electrode plate is wound via a separator, wherein a liquid mixture containing a polymerizable monomer or macromer and a lithium ion salt is prepared. Impregnated in a separator made of a microporous resin film, laminated on both surfaces of one of the electrodes and polymerized and gelled, and then laminated and wound on the other electrode to form a cylindrical spiral. The above object has been achieved by proposing a method of manufacturing a lithium battery.

According to the present invention, a microporous resin film for a separator is impregnated with a liquid mixture containing a lithium ion salt and gelling by polymerization, and is laminated on both surfaces of one of the electrode plates and further polymerized and gelled. In this step, when laminating on both sides, the surface of the microporous resin film is tacky, so that the adhesion between the electrode plate and the separator film is improved, and only the conventional microporous resin film is applied to the electrode plate. In comparison with a case where the microporous film is laminated, troubles such as generation of wrinkles of the microporous film in the winding step are less likely to occur. Further, in the present invention, the method of impregnating the microporous film in the state of the liquid mixture, and then gelling, is easier to impregnate the inside of the separator than the method of simply impregnating a high-viscosity gel-like substance. The air gap is small and the internal resistance is small.

The liquid mixture to be impregnated into the microporous resin film for a separator according to the present invention contains a polymerizable monomer or macromer, and a lithium ion salt, and is further added with an organic solvent if necessary to improve ionic conductivity. Is also good.

LiClO ₄ , LiBF ₄ , LiAsF ₆ , Li
PF ₆ , LiSCN, LiI, LiBr and the like are mentioned as examples.

Examples of polymerizable monomers and macromers include acrylates and methacrylates, and examples thereof include methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, pentyl acrylate, aryl acrylate, and methacrylic acid. Methyl, ethyl methacrylate, propyl methacrylate, butyl methacrylate, aryl methacrylate, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 1,6-hexanediol acrylate, 1,6-hexanediol methacrylate, trimethylolpropane tri Methacrylate and the like.

There are also acryloyl-modified polyalkylene oxides, such as diethylene glycol monoacrylate, diethylene glycol methacrylate, triethylene glycol monoacrylate, polyethylene glycol monoacrylate, methoxytetraethylene glycol monoacrylate, phenoxytetraethylene glycol monoacrylate, and triethylene glycol. There are monomethacrylate, polyethylene glycol monomethacrylate, methoxypolyethylene glycol monomethacrylate, polyethylene glycol dimethacrylate, and the like, or the above-mentioned one in which the ethylene glycol structure is changed to a propylene glycol structure can also be used.

Alternatively, it is also possible to use one in which the ethylene glycol structure is changed to a random or block copolymer structure of units of ethylene oxide and propylene oxide.

Alternatively, a reactive oligomer or polymer used for a UV curing paint or the like can also be used. For example, an unsaturated acrylate prepolymer obtained by modifying an unsaturated polyester with acrylic acid, an acryl-modified siloxane, an acryl-modified polyurethane prepolymer, and the like can be given. These can be used in combination of two or more.

The content of the above-mentioned lithium ion salt in the above-mentioned liquid mixture is preferably in the range of 0.01 to 50% by weight, and more preferably 0.1 to 30% by weight. If the content of the lithium ion is too large, the excess lithium ion salt does not dissociate and form a solid solution, but merely mixes, and the ion conductivity is reduced. Also, when the content is too small, the amount of dissociated lithium ions as charge carriers decreases, and the ionic conductivity decreases.

Examples of the organic solvent include propylene carbonate, acetonitrile, γ-butyrolactone, ethylene carbonate, tetrahydrofuran, dimethoxyethane, dimethyl sulfoxide, dioxolan, sulfolane, and other known organic solvents, and low molecular weight polyethylene glycol. And liquid substances such as polypropylene glycol and copolymers thereof.

After impregnating the liquid mixture into a separator made of a microporous resin film, laminated on both sides of one of the electrode plates,
Gelation is performed by heating or irradiation with actinic rays, and the separator and the electrode plate are brought into close contact with each other. At this time, if necessary, a photoinitiator or a thermal polymerization initiator such as peroxide may be contained in order to promote polymerization gelation. These impregnation, lamination, and polymerization gelation steps can be performed continuously using a roll or the like.

As the negative electrode active material in the present invention, lithium or a lithium alloy such as lithium and aluminum, mercury,
An alloy with zinc or the like can be given. These sheet-shaped materials can be used as a current collector by being pressed against, for example, a stainless steel net.

As the positive electrode active material, for example, those known as positive electrode active materials for lithium batteries, such as manganese dioxide, molybdenum trioxide, vanadium pentoxide, sulfides of titanium or niobium, chromium oxide, and copper oxide are used. be able to. As the positive electrode, these active materials are mixed with, for example, graphite as a conductive agent and, if necessary, as a binder, for example, polytetrafluoroethylene, and used in the form of a sheet. If necessary, a stainless steel mesh or the like may be used as a reinforcing agent inside to maintain the shape of the sheet.

The microporous resin film used in the present invention is not particularly limited, but generally has a film thickness of 5 to 100 μ and a porosity of 30 to 90.
% Is used.

The other electrode plate is superimposed on the electrode plate on which the separator is laminated, and the current-collecting rod with the indigo is used as a core rod, and spirally wound,
A spiral battery is prepared by placing the battery in a cylindrical battery case and injecting and closing the electrolyte.

[Example] Example 1 A negative electrode plate obtained by pressing lithium foil on a stainless steel net (current collector) is used. 25 parts by weight of polyethylene glycol monomethacrylate (manufactured by Shin-Nakamura Chemical, M-90G), 75 parts by weight of polyethylene glycol dimethacrylate (manufactured by Shin-Nakamura Chemical, 9G), dimethoxy polyethylene glycol (CLE-400, manufactured by Asahi Denka, average molecular weight 200) 500 parts by weight, lithium perchlorate (LiClO ₄ ) parts by weight, and 2,2-dimethoxy-2-phenylacetophenone 0.1 as a sensitizer
The liquid composition mixed in parts by weight is impregnated into a polypropylene microporous film (manufactured by Hoechst Celanese, Juraguard 2500), laminated on the screen of the above-described negative electrode lithium foil, and irradiated with a UV lamp to form a liquid mixture. Gelled.

As the positive electrode mixture, 75 parts by weight of manganese dioxide, 10 parts by weight of acetylene black, and 15 parts by weight of tetrafluoroethylene were mixed, and a positive electrode sheet was prepared using a stainless steel wire mesh as a reinforcing agent. Laminated and wound on the negative electrode plate coated with the separator, propylene carbonate and, as an electrolytic solution, a solution obtained by dissolving 1.0 M / L of LiClO ₄ in an equal volume mixture of 1,2-tetrafluoroethylene was added, 17.0mm in diameter and 33.5mm in height in a cylindrical battery case
Battery was created.

Ten were created, but there was no trouble such as wrinkling of the separator. When the internal resistance was measured at 1 kHz, 0.52
Ω.

Example 2 In Example 1, 100 parts by weight of trimethylolpropane methacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd.), 500 parts by weight of a propylene carbonate solution in which LiClO ₄ was dissolved at 1 M / L were used as a liquid mixture, and as a sensitizer, A battery was prepared in the same manner as in Example 1, except that a mixture consisting of 0.1 parts by weight of 2,2-dimethoxy-2-phenylacetophenone was used. There were no troubles such as wrinkling of the separator part. The internal resistance was 0.34Ω.

Example 3 The procedure of Example 2 was repeated, except that 1 part by weight of benzoyl peroxide was added as an initiator and polymerization was performed by heating at 80 ° C. instead of polymerization and gelation by UV irradiation.
A battery was prepared in the same manner as in Example 2. There were no troubles such as wrinkling of the separator part. Internal resistance is 0.
It was 36Ω.

Comparative Example 1 A liquid mixture having the same composition as in Example 3 was heated at 80 ° C. to form a viscous gel, and then coating and impregnation on a polypropylene microporous film was attempted. However, because of high viscosity, impregnation was difficult, and it was difficult to uniformly impregnate the internal voids.

Comparative Example 2 In Example 1, the positive electrode sheet was wrapped with a porous polypropylene film and impregnated with an electrolyte to make a similar battery. However, three of the ten batteries thus formed were wrinkled or damaged in the separator. Trouble occurred in the lamination process.

[Effects of the Invention] According to the manufacturing method of the present invention, compared to the conventional manufacturing method, a battery having stable battery characteristics free from wrinkling, breakage, entrapment of air bubbles, etc. of the separator during battery manufacturing can be obtained. Can be obtained efficiently.

Claims (1)

(57) [Claims] 1. A spiral battery in which a belt-like positive / negative electrode plate is wound via a separator, wherein a liquid mixture containing a polymerizable monomer or a macromer and a lithium ion salt is formed of a microporous resin film. A method for producing a cylindrical spiral lithium battery, comprising: impregnating a separator; laminating on both surfaces of one electrode plate to polymerize and gelling; and laminating and winding the other electrode plate.