JPH0628171B2 - Rechargeable electrochemical device and its manufacturing method - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rechargeable electrochemical device used for a mobile DC power supply, a buffer power supply, and the like.

2. Description of the Related Art Organic electrolyte batteries that use light metals such as lithium as the negative electrode active material use fluorocarbon or manganese dioxide as the positive electrode, lithium metal as the negative electrode active material, lithium borofluoride, lithium perchlorate as the electrolyte, etc. Propylene carbonate, γ-butyrolactone, in which the lithium salt of
Although polar and aprotic solvents such as 1.2 diethoxymethane are used, this system is for primary batteries,
Charging is impossible as it is.

On the other hand, as a rechargeable electrochemical device, there is a battery using a lithium alloy for a positive electrode and an activated carbon negative electrode.
Shown in the figure.

In FIG. 3, 1 is a battery case, 2 is a sealing plate made by punching out the same material as the case, 3 is a gasket, 4 is a positive electrode made of activated carbon, 5 is a positive electrode current collector, and 5'is a case 1
It is welded to the inner surface of.

This type of electrochemical device mainly utilizes the charge charge in the electric double layer on the surface of the activated carbon, and therefore the effective surface area and conductivity of the activated carbon forming the electric double layer, and the storage of the current collector and activated carbon. Contact resistance with the case becomes a problem. Conventionally, there have been the following methods for electrically contacting the positive electrode and the case.

(1) A positive electrode mixture is formed around the current collector, a part of the mixture is peeled off to expose the current collector, and this is welded to a case.

(2) One side of the current collector is filled with the mixture, and a part of the mixture is peeled off to bring the current collector and the case into contact with each other.

(3) A non-woven fabric made of activated carbon is used for the positive electrode, and the core material of the positive electrode is welded to the case.

Problems to be Solved by the Invention In the methods (1) and (2), the contact between the positive electrode and the case is complete, and the discharge characteristics are good, but the manufacturing process becomes complicated,
As a result, the cost becomes high. Further, since the capacity is reduced because a part of the mixture is peeled off, conversely, if the filling amount is increased by the peeled amount, the electrode plate becomes thicker, which is disadvantageous.

In the method (3), the production of the positive electrode is simple, but since it is a non-woven fabric, the welding strength with the case is not sufficient, and the welded part may come off after sealing and the dispersion of the discharge characteristics becomes large.
Moreover, the capacity in the same volume becomes extremely small as compared with the positive electrode formed by molding powdered activated carbon. The common problems of the methods in (1) to (3) are that charge and charge in the electric double layer on the surface of activated carbon are used as described above.
In order to obtain stable characteristics in the discharge cycle, it is required that the contact area between the positive electrode and the current collector is as large as possible, but the methods (1) to (3) are limited to the surface of the positive electrode and are not sufficient. The present invention solves the above conventional problems.

Means for Solving the Problems The present invention is a positive electrode sheet molded into a positive electrode using expanded metal as a core material, and a positive electrode punched into a pellet form,
The positive electrode is sandwiched from the top and bottom by adhering the other surface of the positive electrode having no core material to the metal current collector that has been welded to the battery case in advance.

Operation According to this configuration, the contact area between the positive electrode and the current collector is wide and reliable contact with the battery case can be obtained. Therefore, the above
Unlike the cases of (1) and (2), it is possible to obtain a high capacity in the same volume without the need to remove the mixture, and the manufacturing process is simple. Further, since there is a current collector over the entire positive electrode, there is also a reliable current collecting effect, and the welding strength is certainly increased as compared with (3).

Embodiments Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows, as one embodiment of the present invention, a rechargeable organic electrolyte battery having a height of 2 mm and a diameter of 20 mm. In FIG. 1, 4 is a positive electrode using 9 expanded metal as a core material, activated carbon powder having a surface area of 1500 cm ² / g, carbon black as a conductive material, and 6-fluorinated propylene and 4-fluoride as a binder. This is a sheet formed by mixing a copolymer with ethylene oxide and using a core material as a core, and the thickness of the core material reaches up to about 50% of the thickness of the positive electrode mixture. Next, a titanium lath is punched out to a diameter of 14 mm, spot welded 5'to the center of the inner surface of the battery case 1 to form a positive electrode current collector 5, and the above-mentioned positive electrode 4 is mounted on this positive electrode current collector. Then, the positive electrode 4 and the positive electrode current collector 5 were integrated and brought into close contact with each other by the pressure applied at the time of sealing. Reference numeral 7 denotes a negative electrode, which is obtained by rolling an alloy of lithium and lead into a sheet having a thickness of 50 μ, punching it out to a diameter of 14 mm, and crimping it onto a negative electrode current collector 8 made of a nickel metal net that is welded to the inner surface of the sealing plate 2 in advance. did. 3 is a gasket, 6
Is a separator made of polypropylene nonwoven fabric. For the electrolyte, 1 mol / mol of lithium borofluoride was added to a mixed solvent of propylene carbonate and 1,2-dimethoxyethane.
What was melt | dissolved in the ratio of is used. This battery is a rechargeable electrochemical device having a total height of 2 mm, a diameter of 20 mm and a capacity of 1 mA / V.

In FIG. 1A, a positive electrode 4 is used, in which activated carbon powder is mixed with a binder, then formed into a sheet, and then punched into pellets. This is placed on the metal current collector 5 previously welded in the battery case 1, and the case 1 is placed as shown in FIG. 2B.
The positive electrode 4 and the current collector 5 are integrated by the pressure applied at the time of sealing, and the positive electrode 4 and the current collector 5 have a sandwich structure in which the positive electrode is sandwiched by the expanded metal and the current collector. Next, A, B, and C are obtained by electrically connecting the positive electrode and the case by the methods of the above-mentioned conventional examples (1) to (3), and those according to the present example are designated as D, and each battery is 1 mA. After repeating charging and discharging for 1 hour, the internal resistance after 1000 cycles and the discharge capacity from 3 V to 1.5 V at 1 mA discharge were measured. The results are shown in Table 1 as an average value x and a variation σ.

Table 2 shows the results of changing the ratio of the surface area of the current collector to the surface area of the positive electrode after punching.

From this result, the surface area of the current collector is larger than that of the positive electrode.
When it is 0.3 or less, the current collecting effect is lost, and when it is 0.9 or more,
The current collector becomes larger than that of the positive electrode, and the mixture at the end of the pellet easily collapses during battery construction, which causes an internal short circuit.

As is clear from the above results, the surface area of the current collector and the positive electrode is optimally 0.3 to 0.9 with respect to the positive electrode 1.

EFFECTS OF THE INVENTION As is apparent from the above description, the activated carbon is punched into a pellet shape after sheet molding, and the expanded metal of the positive electrode core material and the case side current collector are provided on the metal current collector that is previously welded to the inner surface of the case. The battery of the present invention having a configuration in which the positive electrode is placed so as to have a sandwich structure and the positive electrode and the current collector are brought into close contact with each other by the pressure applied when the case is sealed, and the positive electrode, the current collector and the case are not in contact with each other. It has sufficient internal resistance and good charge / discharge performance and storage performance. Moreover, the manufacturing process can be simplified and mass productivity can be improved.
An industrially valuable manufacturing method can be obtained.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a rechargeable organic electrolyte battery according to an embodiment of the present invention. 2A and 2B are diagrams showing a process of constructing the battery of the present invention, and FIG. 3 is a sectional view of a rechargeable organic electrolyte battery manufactured by a conventional manufacturing method. 1 ... Positive electrode case, 2 ... Sealing plate, 3 ... Gasket,
4 ... Positive electrode, 5 ... Positive electrode current collector, 5, 5 '... Spot weld, 6 ... Separator, 7 ... Load, 8 ... Negative electrode current collector, 9 ... Positive electrode core material.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Hayashi Hayakawa, 1006 Kadoma, Kadoma City, Osaka Prefecture, Matsushita Electric Industrial Co., Ltd. (72) Yuji Kano, 1006 Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd. 56) References JP-A-60-17857 (JP, A) JP-A-58-121553 (JP, A) JP-A-59-96678 (JP, A) Actual development Sho-54-174820 (JP, U) JP 57-32865 (JP, B2)

Claims (3)

[Claims] 1. A rechargeable electrochemical device comprising a positive electrode containing activated carbon as a main component, a lithium alloy negative electrode containing lithium as an active material, and an organic electrolyte, wherein the positive electrode is a sheet of a mixture of activated carbon and a binder. It is in the form of pellets that are molded and punched into a shape, one side of which is fitted with an expanded metal core material, and the other side of which is fitted with a metal current collector welded to the inner surface of the battery case. And a rechargeable electrochemical device. 2. The area ratio between the current collector on the inner surface of the battery case and the punched out positive electrode is 0.3 to 0.9 when the positive electrode is 1, and the area of the current collector is 0.3 to 0.9. A rechargeable electrochemical device as described. 3. A method of manufacturing a rechargeable electrochemical device comprising a positive electrode mainly containing activated carbon, a lithium alloy negative electrode containing lithium as an active material, and an organic electrolyte, wherein the positive electrode is a mixture of activated carbon and an adhesive. After forming a sheet using expanded metal as the core material and punching it into pellets, the other side of the pellet-shaped positive electrode without the core material faces the metal current collector that was previously welded to the inner surface of the battery case. A method for manufacturing a rechargeable electrochemical device, which comprises placing the metal collector on the other surface of the pellet-shaped positive electrode by applying pressure when the positive electrode case is caulked and sealed.