JP3488267B2 - Sheet secondary battery and method of manufacturing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a sheet secondary battery.

[0002]

2. Description of the Related Art In recent years, as electronic products have become smaller and lighter, batteries have become smaller and lighter. In addition, the shape of the battery tends to diversify into coin type, prismatic type, paper type, etc.
Paper lithium batteries of 0.5 mm or less that can be loaded in a card have been developed. Recently, from the viewpoint of energy and global environment protection, there has been a strong demand for higher functionality and higher energy in secondary batteries, and paper secondary batteries using lithium as an active material have been reported. A paper battery generally has a battery structure as shown in FIG. 1 for a primary battery. 4'is a negative electrode sheet, 3 is a positive electrode sheet, and 5'is an ion conductive electrolyte layer. A frame-shaped sealing member 6 made of polypropylene resin is arranged around the power generation cell made of these materials. Reference numeral 2 denotes a positive electrode current collector plate made of a stainless plate, a nickel plate, etc., which also serves as an exterior. The battery configuration of the secondary battery is basically similar to that of the primary battery. However, secondary batteries require higher reliability in charge / discharge cycles than primary batteries, and short-circuit prevention design is an important issue. In a paper-type secondary battery, an electrical short circuit easily occurs at the ends of two current collectors in the conventional primary battery configuration, and no consideration is given to the cycle life.

[0003]

An object of the present invention is to provide a sheet secondary battery having high reliability while preventing electrical short circuit at the end of the current collector of the battery, improving cycle characteristics.

[0004]

A first aspect of the present invention is a sheet secondary battery having at least a power generating element and a sealing material for sealing a peripheral portion of the power generating element, the positive electrode and the negative electrode having different areas. In a sheet secondary battery in which the width of the sealing material is different on the positive electrode side and the negative electrode side in correspondence with the areas of the positive electrode and the negative electrode, the negative electrode is a sheet electrode made of a carbon active material The sheet secondary battery is characterized in that the negative electrode has a larger energy capacity that can be stored in the negative electrode than the positive electrode. A second aspect of the present invention is characterized in that, after the electrode plates, in which the sealing material is separately applied or printed on the positive electrode plate and the negative electrode plate, are laminated, the peripheral edge portion is sealed by heat sealing. The present invention relates to a method for manufacturing a sheet secondary battery. A third aspect of the present invention relates to a secondary battery including the laminated body of the sheet secondary battery according to claim 1, 2 or 3.

[0005]

DETAILED DESCRIPTION OF THE INVENTION The inventors of the present invention have found that a paper battery uses a material that is reactive with outside air or moisture such as lithium and lithium ion-occluding carbon in a paper battery, and the battery capacity is reduced during storage or deformation occurs due to swelling. And the cause of the decrease in cycle life is due to the permeation of water from the sealing material.In addition, the cycle life of the secondary battery and the short circuit during manufacturing have a great influence on the battery structure, especially the electrode area. The present invention has been completed by finding out that it is received. That is, it was found that excellent reliability and cycle characteristics are exhibited by changing the electrode area of the positive and negative electrodes and changing the amount of energy of the positive and negative electrodes. In particular, in a secondary battery configuration in which a carbon electrode sheet is used for the negative electrode, the negative electrode area is made smaller than that of the positive electrode, and the width of the sealing portion at the peripheral portion of the negative electrode is made larger, thereby improving cycle characteristics and improving reliability. Realized a high battery configuration. The reason is based on the following experimental results. Here, the graphite obtained by calcination of the fluid coke at 2500 ° C. will be described as an example. That is, the energy capacity of graphite that can be discharged is 250 mAh / unit weight in the voltage range of 0 V to 3.0 V with respect to the potential of lithium.
It is g. Here, when a battery is constructed using a vanadium oxide electrode for the positive electrode, the OCV is 3.7 when the battery is positively and negatively charged.
It should show a voltage of V. If the carbon were completely discharged, the battery would have a voltage below 0.7V. Therefore, in the ion storage battery, carbon is allowed to discharge substantially within the range of 0 V to 1.5 V with respect to the potential of lithium. Of course, the smaller the discharge voltage range, the better. In the battery structure of the present invention, high cycle characteristics are obtained in a state where the negative electrode is not completely discharged with respect to the discharge of the positive electrode. In this case, the discharge capacity of the negative electrode graphite was calculated to be 200 mAh / g or less. A configuration example is shown by the figure. FIG. 2 is a plan view of the battery of the present invention, and FIG.
Here, 1 is a positive electrode current collector, 2 is a negative electrode current collector, 3 is a positive electrode sheet, 4 is a negative electrode carbon sheet, 5 is an electrolyte film, and 6 is a sealing body having electrical insulation. The electrolyte film is made of a polymer solid electrolyte. As the sealing body 6, a thermoplastic resin such as modified polypropylene or modified polyethylene is used, and the current collectors 1 and 2 are heated and fused and sealed. It is particularly preferable to apply the sealing material for the battery by coating in terms of productivity and addition of a filler. Examples of the coating type sealing material include thermosetting or photocurable acrylic resin, urethane resin, modified polyolefin resin, and the like. Among them, dispersion of carboxylic acid modified polyolefin has particularly excellent performance and productivity. In addition, long-term storage was solved by adding powders of silica, alumina, aluminum and the like. Next, a specific manufacturing method example will be described. To make a battery, print the electrode active material on the positive and negative electrode plates, further infiltrate the positive electrode with the solid electrolyte composition and irradiate it with light to form an electrolyte layer, then print the sealing material and stack it, then heat seal the peripheral edge. I went by. The positive electrode was prepared and implemented by two methods.

[0006]

【Example】

Example 1 5.0 mol of propylene carbonate, 5.0 mol of 1,2-dimethoxyethane as a solid electrolyte composition, 1.
75 mol of LiBF ₄ , 1.38 mol of ethoxydiethylene glycol acrylate and 0.11 mol of triethylene glycol diacrylate were mixed and dissolved, and 4% of methylbenzoyl formate per unit weight of the polymerizable compound was added to obtain a solid. An electrolyte composition solution was prepared. For the positive electrode, a solution of 0.5 mol of aniline in 1000 parts of 5.5 N HBF ₄ solution was used, and a polyaniline thin film was formed on a SUS substrate at a constant potential of 0.8 V vs SCE and a charge amount of ² C / cm ^2. Formed. This was made into a completely reduced body by a predetermined reduction treatment, then sufficiently dried, and a polypropylene separator having the same area was superposed thereon and impregnated with the solid electrolyte forming composition, which was sandwiched between glass substrates and pressurized with 1 kg. The impregnated composition was cured by irradiating it with actinic radiation from a high pressure mercury lamp. The composition completely solidified into a viscoelastic body, had no fluidity, and integrated with the electrode. After that, a carboxylic acid-modified polypropylene dispersion was printed to obtain FIG. For the negative electrode, a pitch coke having a particle size of 3 μm or less is fired at 2500 ° C. to obtain 10% PVD.
It was dispersed in an N-methylpyrrolidone solution of F, applied on a negative electrode plate and dried to obtain a carbon sheet having a thickness of 0.1 mm. The negative electrode was impregnated with the solid electrolyte-forming composition, and irradiated with actinic rays by a high pressure mercury lamp. A carboxylic acid-modified polypropylene dispersion was printed in the same manner as the positive electrode, as shown in FIG. The positive electrode,
The diaphragm and the negative electrode were laminated and sealed by heat sealing to prepare a 4 × 5 cm sheet-type battery shown in FIG.

Example 2 AgMacDiamid et al., C from ammonium persulfate and hydrochloric acid
Polyaniline was synthesized by the method described in onducting polymers., 105 (1987). The reduction treatment was sufficiently performed. 20 parts of polyaniline white powder, acetylene black 20
Parts and 60 parts of vanadium pentoxide were kneaded with an N-methylpyrrolidone solution by a roll mill to obtain a 45% ink composition. It was prepared in the same manner as in Example 1 except that the positive electrode was prepared by printing on an electrode plate and drying.

Comparative Example The configuration was the same as in Example 1 except that the shape of the sealing portion was the same as in FIG. The prepared battery was charged and discharged at 2 mA to evaluate the battery performance. The results are shown in Table 1 below. (Below margin)

[Table 1]

[0009]

According to the present invention, it is possible to prevent electrical short circuit at the end of the current collector of the battery, improve cycle characteristics, and provide a highly reliable sheet secondary battery.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a conventional paper-type primary battery.

FIG. 2 is a plan view of an example of the sheet secondary battery of the present invention.

FIG. 3 is a cross-sectional view of the sheet secondary battery of Example 1.

4 is a cross-sectional view of a positive electrode and a negative electrode of the secondary battery shown in FIG. (A) It is sectional drawing of a positive electrode. (B) It is sectional drawing of a negative electrode.

[Explanation of symbols]

1 Positive electrode current collector 2 Negative electrode current collector 3 Positive electrode sheet (film) 4 Negative carbon sheet 4'Negative electrode sheet (film) 5 Polymer electrolyte film 5'ion conductive electrolyte layer 6 Electrically insulating closure

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Nobuo Katagiri 1-3-6 Nakamagome, Ota-ku, Tokyo Within Ricoh Co., Ltd. (72) Inventor Kotori Kimura 1-3-6 Nakamagome, Ota-ku, Tokyo (56) Reference JP-A-3-108278 (JP, A) JP-A-2-51847 (JP, A) JP-A-4-51455 (JP, A) JP-A-62-296361 (JP, A) JP-A-61-163559 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01M 2/08 H01M 10/40 H01M 2/02 H01M 10/04

Claims (5)

(57) [Claims] 1. A sheet secondary battery comprising at least a power generating element and a sealing material for sealing a peripheral portion of the power generating element, wherein the areas of the positive electrode and the negative electrode are different and the areas of the positive electrode and the negative electrode correspond to each other. In a sheet secondary battery in which the width of the sealing material is different on the positive electrode side and the negative electrode side, the negative electrode is a sheet electrode made of a carbon active material, and the energy capacity that can be accumulated per unit area facing the negative electrode is the negative electrode. A sheet secondary battery having a large size. 2. The sheet electrode, wherein the negative electrode is made of a carbon active material, the negative electrode area is smaller than the positive electrode area, and the width of the sealing material at the peripheral portion of the negative electrode corresponds to the difference in the positive electrode area and the negative electrode area. The sheet secondary battery according to claim 1, which is wider than the width of the portion. 3. The sheet secondary battery according to claim 1, wherein the sealing material is an acid-modified polyolefin containing a fine particle filler. 4. The sheet 2 according to claim 1, wherein the positive electrode and the negative electrode are separately coated or printed with a sealing material, the electrode plates are laminated, and then the peripheral edge portion is sealed by heat sealing. Next battery manufacturing method. 5. A secondary battery comprising a laminated body of the sheet secondary battery according to claim 1, 2 or 3.