JP2869156B2 - Manufacturing method of positive electrode plate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial applications]

The present invention relates to an improvement in a method for manufacturing a positive electrode plate, and particularly to a method for manufacturing a positive electrode plate having good workability.

[Prior art]

As a conventional method for manufacturing a positive electrode plate, a paste method, a press method, a roll method, or the like has been adopted. The paste method produces a positive electrode plate in the following steps. Water, a solvent and the like are added to form a paste-like positive electrode mixture. The paste-like positive electrode mixture is applied to a desired thickness on the surface of the electrode core material. After the application, the coating is dried to remove water, a solvent, and the like to obtain a positive electrode plate. In this method, it is difficult to uniformly apply the paste-like positive electrode mixture to the electrode core material, and many steps such as mixing and kneading of the mixture are required to produce the paste-like mixture. is there. Further, the press method has a drawback that it is difficult to obtain a long and uniform thickness since the wet mixture is pressed into a sheet by pressing. Further, a method of manufacturing a positive electrode plate by a roll method is disclosed in
No. 57-46471. In this method, a positive electrode plate is manufactured in the following steps. The positive electrode mixture in a wet state is passed between a pair of rotating rolls to prepare a spare sheet. The obtained preliminary sheet is dried. Drying condition is 10
2 hours at 0 ° C. The dried preliminary sheet is adhered to both sides of the electrode core material. In order to pressure-bond the sheet to the electrode core material, the sheet and the electrode core material are supplied between a pair of rotating rolls and pressure-bonded by the rolls.

[Problems to be solved by the invention]

The roll method has a feature that a long positive electrode plate having a uniform thickness can be produced. However, this method requires a step of drying the wound sheet, and has a drawback that the sheet is apt to be cut when the sheet coming out from between the rolls is wound on a coil. It is a cause that hinders improvement of the performance. The wet sheet cannot be pressure-bonded to the electrode core material as it is, but must be dried and then pressure-bonded to the electrode core material. The reason is that when a wet sheet formed by a roll is pressed against an electrode core material without being dried without being dried, the sheet partially adheres to a roll for pressing the sheet and the electrode core material. It is. Further, when the sheet is wet-bonded to the electrode core, the wet sheet is more easily stretched than that in the dry state. Therefore, the electrode core is stretched together with the sheet, and the electrode core is cut. The present invention has been developed with the object of solving these conventional disadvantages. An important object of the present invention is to solve problems in work, and to achieve a continuous, efficient and uniform method. An object of the present invention is to provide a method for manufacturing a positive electrode plate.

[Means to solve the problem]

According to the present invention, in order to achieve the above object, a positive electrode plate is manufactured in the following steps. The positive electrode mixture in a wet state is supplied between two pairs of heating rolls. The heating roll heats the positive electrode mixture when the wet positive electrode mixture is formed into a sheet to reduce the moisture content. The sheet formed by the heating roll is supplied to a pair of pressure rolls in a laminated state on both surfaces of the electrode core material, and the sheet is pressure-bonded to both surfaces of the electrode core material by the pressure roll.

[Action]

In the method for producing a positive electrode plate according to the present invention, the positive electrode mixture is formed into a sheet by a heating roll. The heating roll heats the positive electrode mixture in the step of forming the positive electrode mixture into a sheet to reduce the moisture content. For this reason, the sheet formed by the heating roll can be pressed against the electrode core material without drying. Thereafter, the sheet formed by the heating roll is continuously supplied to a pressure bonding roll, and the pressure bonding roll presses the sheet to both sides of the electrode core material.

【Example】

Hereinafter, examples of the present invention will be described in detail. [Wet state positive electrode mixture adjustment step] The following materials (1) to (5) are weighed and mixed to obtain a wet state positive electrode mixture. A mixture of 90 parts by weight of manganese dioxide powder as a positive electrode active material, 8 parts by weight of graphite as a conductive agent, 3.3 parts by weight of a dispersion of polytetrafluoroethylene as a binder, but 2 parts by weight as a solid content Add water and mix. The amount of water added is such that the water content becomes 25% by weight. [Step of Forming Positive Electrode Mixture] The obtained positive electrode mixture in a wet state is formed into two sheets by using two pairs of heating rolls A, B, C, and D shown in FIG. The pair of heating rolls A and B and C and D are arranged in parallel with each other. Heating rolls A and B, heating rolls C and D
Determines the thickness of the sheet 2 to be formed. The intervals between the heating rolls A and B and between the heating rolls C and D are adjusted so that the thickness of the sheet 2 to be formed is 0.55 mm. When the distance between the heating rolls A and B and C and D is reduced, the formed sheet 2 becomes thinner, and when the distance is increased, the formed sheet 2 becomes thicker. The heating rolls A, B, C and D form the wetted positive electrode mixture 1 and heat it to reduce the moisture content of the formed sheet 2. Therefore, the moisture content of the sheet 2 can be controlled by the temperature of the heating roll. The heating roll adjusts the surface temperature to 100 ° C. so that the moisture of the sheet can be removed simultaneously with the forming. However, the present invention does not specify the surface temperature of the heating roll to be 100 ° C. Table 1 shows the relationship between the surface temperature of the heating roll and the moisture value of the sheet 2 when the temperature of the heating roll is variously changed. The moisture value of the sheet affects the adhesion state of the roll for forming the positive electrode plate and the elongation of the electrode core material. Table 2 shows the relationship between the moisture value of the sheet and the state of adhesion to the roll when the sheet and the electrode core material are pressed by a roll. This table shows that when the moisture value of the sheet is 7.5% by weight or less, the sheet does not adhere to a roll for pressing the sheet to the electrode core material. Further, Table 3 shows the relationship between the water content of the sheet and the elongation percentage of the electrode core material when the sheet and the electrode core material are pressed by a roll. This table shows that when the moisture value of the sheet is 7.5% by weight or less, the elongation of the electrode core material becomes zero in the step of pressing the sheet. Therefore, from Tables 2 and 3, it can be seen that the moisture value of the sheet to be pressed against the electrode core material is preferably 7.5% by weight or less. The sheet used in the above test was manufactured under the following conditions. A mixture comprising 90 parts by weight of manganese dioxide powder as a positive electrode active substance, 8 parts by weight of graphite as a conductive agent, and 3.3 parts by weight of a dispersion of polytetrafluoroethylene as a binder (2 parts by weight as a solid content). Then, water was added so that the content of water became 25% by weight, and mixed to prepare a positive electrode mixture in a wet state. The positive electrode mixture in a wet state was passed between a pair of rotating rolls to form a sheet having a thickness of 0.55 mm, which was dried with a drier to obtain a sheet having each moisture value. As the electrode core material, a stainless steel plate having a thickness of 0.10 mm and processed into a three-dimensional lath having a mesh (SW × LW) of 1.0 mm × 2.0 mm and a three-dimensional thickness of 0.28 mm was used. Here, SW is a distance between centers in the short direction of the mesh of the three-dimensional lath, and LW is a distance between centers in the long direction. From Tables 2 and 3, the moisture value of the sheet to be pressed against the electrode core material is preferably 7.5% by weight or less. For this reason,
According to Table 1, the surface temperature of the heating roll is preferably 80 ° C. or higher. Further, even if the surface temperature of the heating roll is set to 200 ° C. or less, the moisture value of the sheet does not change. For this reason, the surface temperature of the heating roll is preferably adjusted to a range of 80 to 200 ° C. Further, the moisture content of the sheet formed by the heating roll is
It also varies slightly depending on the peripheral speed of the heating roll. If the peripheral speed of the heating roll is low, the heating time of the positive electrode mixture becomes long, and the moisture content decreases. Conversely, if the peripheral speed of the heating roll is high,
The heating time of the positive electrode mixture is shortened, and the moisture content of the sheet is increased. However, since the sheet formed by the heating roll is extremely thin, the change in the moisture content of the sheet due to the peripheral speed of the heating roll is extremely small. Further, the moisture content of the sheet changes depending on the thickness of the sheet. Even if the surface temperature of the heating roll is the same, if the sheet is thin, the moisture content will be low. This is because water is easily vaporized in the step of being pressed by a heating roll and being heated and molded. However, the sheet is formed to be extremely thin, and the thickness of the sheet is adjusted to an extremely limited range from the performance as a positive electrode plate. Therefore, in the actual manufacturing process, the change in the moisture content due to the change in the thickness of the sheet is extremely small. [Step of pressing the sheet to the electrode core material] The sheet formed by the heating roll and having the adjusted moisture content is pressed against both surfaces of the electrode core material 3 by the pressure bonding rolls E and F. In order to crimp the sheet 2 on both sides of the electrode core material 3, the first
As shown in the figure, the sheet 2 is positioned on both sides of the electrode core material 3, the electrode core material 3 is laminated between the sheets 2, and supplied between a pair of pressure bonding rolls E and F. The press rolls E and F press the sheet 2 against the electrode core 3 to form the positive electrode plate 4 containing the electrode core. Crimping rolls E and F
Presses the sheet 2 to form a positive electrode plate 4 having a thickness of 0.45 mm.
And As the electrode core material 3, a stainless steel plate having a thickness of 0.10 mm and processed into a three-dimensional lath having a mesh (SW × LW) of 1.0 mm × 2.0 mm and a three-dimensional thickness of 0.28 mm can be used. In the method of manufacturing the positive electrode plate shown in FIG. 1, the positive electrode plate 4 is manufactured using four heating rolls A, B, C, and D and two pressure rolls E and F. However, the method of manufacturing a positive electrode plate of the present invention is to form a sheet from a positive electrode mixture in a wet state,
It is not necessary to use four heating rolls. For example, as shown in FIG. 2, the positive electrode mixture in a wet state is formed into a preliminary sheet 2 ′ having a predetermined thickness by unheated rolls G, H, I, and J, and the preliminary sheet 2 ′ is heated by a heating roll A, B,
It is also possible to supply the sheet 2 and C to adjust the moisture content to form the sheet 2. Further, the heating roll and the pressure roll need not necessarily be separate rolls. As shown in FIG. 3, one roll can be used in combination with the heating roll and the pressure roll. In FIG. 3, rolls B and C for pressing the sheet 2 on both sides of the electrode core 3 are used in combination with a heating roll and a pressing roll. FIG. 4 shows a half-mounted side view of a battery assembled using the positive electrode plate manufactured in the above steps. In this figure, reference numeral 5 denotes a negative electrode plate formed of a 0.3 mm-thick strip-shaped lithium rolled plate. A negative electrode current collecting lead plate 6 is crimped to one side surface of the negative electrode plate 5. Negative current collecting lead plate 6
Is fixedly connected to the lower surface of the sealing plate 8 and is electrically connected thereto. The sealing plate 8 is fixed to the lower surface of the sealing lid 7 also serving as a negative electrode terminal. Reference numeral 4 denotes a positive electrode plate having a thickness of 0.
45mm thing is used. At the lower end of the positive electrode plate 4, a positive electrode current collecting lead plate 9 is fixed. Positive current collecting lead plate 9
The other end is fixed to the inner bottom surface of the outer can 10 also serving as a positive electrode terminal,
Electrically connected. Reference numeral 11 denotes a separator using a microporous polypropylene membrane. The separator 11 is stacked between the positive and negative electrode plates. The laminate of the separator 11 and the positive and negative electrode plates 4 and 5 is wound to form a spiral electrode body. 12 is an insulating packing, 13 is an insulating washer, and 14 is a can bottom insulating plate. In addition, as the electrolyte, propylene carbonate,
A solution in which lithium perchlorate is dissolved in a mixed solvent with dioxolane is used.

【The invention's effect】

In the method of manufacturing a positive electrode plate according to the present invention, a wet positive electrode mixture is supplied between two heated rolls to form two sheets. The heating roll forms the positive electrode mixture into a sheet and heats the positive electrode mixture to reduce the moisture content. The sheet whose moisture content has been adjusted is laminated on both sides of the electrode core material and supplied to a pressure roll. Therefore, according to the method for manufacturing a positive electrode plate of the present invention, the sheet formed by the heating roll can be continuously supplied to the pressing roll to be bonded to the electrode core. For this reason, the method for manufacturing a positive electrode plate of the present invention can continuously and uniformly manufacture a positive electrode plate, can greatly improve workability as compared with the conventional manufacturing method, and has an industrial value. Very large.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of an apparatus used in an embodiment of the method for producing a positive electrode plate of the present invention, FIGS. 2 and 3 are schematic sectional views of an apparatus used in another embodiment of the present invention, FIG. 4 is a half-mounted side view of a battery manufactured using the positive electrode plate obtained by the manufacturing method of the present invention. A, B, C, D… Heating roll E, F… Pressure roll 1… Positive electrode mixture 2… Sheet 2… Preliminary sheet 3… Electrode core material 4… Positive electrode plate 5, negative electrode plate, 6 negative electrode current collecting lead plate, 7 sealing lid, 8 sealing plate, 9 positive electrode current collecting lead plate, 10 outer package can, 11 separator, 12 ... insulating packing, 13 ... insulating washer, 14 ... can bottom insulating plate.

Claims (1)

(57) [Claims] A positive electrode mixture in a wet state is supplied between two pairs of heating rolls, and the heating roll heats the positive electrode mixture when forming the positive electrode mixture in a wet state into a sheet. The moisture content is reduced, and the sheet formed by the heating roll is supplied to a pair of pressure rolls in a laminated state on both surfaces of the electrode core material, and the sheet is pressure-bonded to both surfaces of the electrode core material by the pressure roll. Characteristic method for producing a positive electrode plate.