JPH04155767A - Thin type lead acid battery - Google Patents

Abstract

PURPOSE:To prevent an active material from falling off by constituting in such a way that the active material has a crystalline graphite structure and also contains hollow carbon fiber as an additive. CONSTITUTION:Cut fiber, sulfuric acid and water are added to lead powder so as to be kneaded together, and carbon fiber, which has the diameter of 0.1-0.3mum, the length of less than 7mum and a graphite structure of the hollow diameter of 0.03-0.14mum, is added to obtained paste to be agitated so that it can be 0.4wt.% to the lead powder, and then water content is adjusted to be 13wt.% so as to form positive electrode paste. Meanwhile, two current collecting bodies consisting respectively of Pb-Ca-Sn alloy are arranged in parallel on a plastic film substrate to be adhered by means of pressure so as to form the current collecting bodies for a positive electrode and negative electrode. In this way, by forming the positive electrode paste by adding the carbon fiber having a crystalline graphite structure and a hollow structure to lead paste to be mixed, even if the graphite structure of the carbon fiber forms a compound between graphite layers, an active material never falls off because of the hollow structure.

Description

[Detailed description of the invention]

[Industrial Field of Application J] The present invention relates to a thin lead-acid battery having a battery thickness of approximately 1s+s+, and particularly to a thin lead-acid battery capable of increasing capacity.

[Background Art] With the spread of small devices such as portable devices, the demand for inexpensive and thin sealed storage batteries is increasing. JP-A-1-1
32064, Japanese Patent Application No. 1-168531, and Japanese Patent Application No. 1-317619 disclose thin storage batteries by the present inventors. These thin storage batteries are, for example,
As shown in the figure, a positive electrode plate consisting of a positive electrode current collector 2 and a positive electrode active material 3 and a negative electrode plate consisting of a negative electrode current collector 4 and a negative electrode active material 5 are provided on the surface of one film-like case 1. The space between each end face of the positive electrode plate and the negative electrode plate is filled with an electrolyte 6 containing sulfuric acid. The other film-like case 7 seals the entire battery to form a thin battery. By adopting such a structure, the direction of the field of battery reaction during charging and discharging occurs not between the electrode surfaces, but between the electrode ends d, which are parallel to the electrode surfaces. This protects the current collector located at the center of the electrode surface from deteriorating, so that even if the electrode thickness becomes thinner, the lifespan will not be reduced, making it possible to make the electrode thinner. In addition, the electrodes are formed by applying lead paste as an active material on the current collector 2.4 made of lead or lead-based alloy fixed to the case 1 by the stamping method, and going through the generation and chemical formation process. ing. The lead paste used for this purpose is manufactured using a common manufacturing method. That is, lead powder is mixed with sulfur and water, and if necessary, cut fibers, lignin and barium sulfate are added as additives, and the lead paste is made into a live wire. On the other hand, it is generally known that the high capacity performance required for batteries and long-term whitening are in a contradictory relationship with each other, but there is a special method to improve the capacity performance of the cathode active storage without impairing the life performance. It is disclosed in 1988-89071. This is a method in which anisotropic graphite with a layered structure is added to the positive electrode paste, and during chemical formation, this anisotropic graphite is anodized in sulfuric acid to produce a graphite intercalation compound, and the positive electrode It improves the utilization rate of materials. Journal' of
Power 5 sources, 27 (1989) P1
According to 27-143, it is said that (1) the utilization rate of the positive electrode active material is increased in order to improve the diffusibility of sulfate ions due to electrophoresis, and the battery capacity is increased11. ~ - [Problem to be solved by the invention 1] Thin lead-acid batteries have the advantage of being thin, but - as long as lead paste is used using a numerical manufacturing method, there is a limit to the amount of active material that can be applied. Therefore, it is inevitable that the capacity will become smaller. Therefore, if you want to increase the capacity, you have to coat the active material thickly, which causes the problem of damaging the thin shape.Therefore, we use the above-mentioned anisotropic graphite-added paste to form the electrode. However, in this method, the active material that adheres to the current collector during the aging process expands when the anisotropic graphite becomes a graphite intercalation compound during the chemical formation process. Therefore, a problem arose in that the battery detached from the current collector and electrode formation could not be performed.The present invention was made in view of the above-mentioned problems, and does not impair the characteristic feature of the battery shape, which is the battery's thin shape. An object of the present invention is to provide a thin lead-acid battery that enables high capacity without any problems. 1. Means for Solving the Problems] In order to achieve the above-mentioned objects, the present invention provides a current collector made of lead or shipboard metal. A thin lead-acid battery having an electrode plate made of an active material in close contact with the current collector surface, wherein the active material has a substantially crystalline graphite structure and hollow carbon fibers are used as an additive. The carbon fiber is characterized in that the spacing between the (002) planes is d (002
) initial Å, the size of crystallites of (002) plane and (110) plane are both Lc (002) > 100 Å, La
(110) > 100, and the intensity ratio of the Raman bands at 1360 cm-' and 1580 cm-' (Lsso/
Ls*o) is 0.25 to 0. It may be III. [Function] Conventionally, the lead paste used to form electrodes for thin batteries with a thickness of about 1 mm is made by mixing sulfuric acid and water with lead powder, and then adding cut fibers as necessary. Lignin and barium sulfate are added as additives and kneaded to create a lead paste, which is then applied to a current collector by a printing method and subjected to aging and chemical conversion treatment to form an electrode. As an additive, a hollow crystalline carbon fiber having a space that compensates for the volume of the expansion is used so that the active material does not fall off even if it expands during the formation of a graphite intercalation compound during chemical formation. Here, crystalline carbon fibers include not only crystals with a perfect graphite structure but also graphite fibers with a slightly disordered crystal structure.
The interplanar spacing of the (002) plane is approximately Å, and the (002) plane and (1
10) The crystallite size of the plane is Lc (002) > 10
0 Å, La(110) > 100 Å, 1360 cm
-' and 1580 cm-' Raman band intensity ratio (11
ago/I+sa. ) is 0.25 to 0.18, it is possible to prevent the active material from falling off during the chemical formation process and form a graphite intercalation compound. Therefore, the thin shape of the battery and the conventional screen printing etc. It is possible to increase the capacity of a thin lead-acid battery without changing the paste application process, aging process, and chemical conversion process. [Example 1] The details of the present invention will be explained below with reference to Examples. 0.6g of cut fiber for 300g of lead powder, 20
While gradually adding 80 cc of wt% sulfuric acid and 80 cc of water, the mixture was kneaded using a milk needle. The paste obtained by kneading has a diameter of 0.1 to 0.3μ, a length of about 7μ or less, and a hollow diameter of 0.
Carbon fiber having a graphite structure of 0.3 to 0.14 μm was added to the lead powder to give a concentration of 0.4 wt%, and the mixture was stirred using a general-purpose stirrer to reduce the moisture content to 13 wt% (paste density: 4
．． 4 g/cm”) to obtain a positive electrode paste.
A scanning electron micrograph of the carbon fiber used in the figure is shown in FIG. 2, and a transmission electron micrograph thereof is shown in FIG. As seen in FIG. 2, this carbon fiber is a hollow fiber. The (002) plane spacing of the carbon fiber used is Å, Lc(002)416
Å, La (110) = 141 people. Raman band intensity ratio 118. . /Eng 3. . . =0.18
It is. Other than adding a predetermined amount of lignin and barium sulfate to 300g of lead powder in addition to cut fibers,
Repeat the same operation to reduce the water content to 11wt% (paste density: 4
．． 5 g/cm") to obtain a negative electrode paste. On the other hand, each current collector 2 was made of Pb-Ca-3n alloy and had dimensions of 51111 mm width x 60 m length x 0.1 mm thickness.
The book was placed in parallel on a plastic film substrate and crimped to form a current collector for the positive and negative electrodes. The distance between the positive and negative electrodes was set to 5 points. Next, apply the positive electrode and negative electrode pastes prepared above to a radius of 5+n.
It was rubbed and coated onto the surfaces of the positive electrode and negative electrode current collectors by a printing method through a metal mask having a length of 50 mm and a thickness of 0.51 mm. After that, paste the paste at 25℃.
It was left standing in 90% RH for 2 days to age and harden. Furthermore, the electrodes were formed by chemical conversion at a constant current of 20A+A for 20 hours, washed with water, and dried.Next, in order to confirm the battery performance,
An electrolyte in which a glass retainer is impregnated with 0.61 g of 46% sulfuric acid is placed between the electrodes and on the top of the negative electrode plate, and a plastic film identical to that of the film substrate is placed over it, and the four sides of the top and bottom film substrates are heated. A thin sealed lead-acid battery with a thickness of 0.8 mm was produced by heat-sealing by seek. The results of charging and discharging tests on these batteries are shown in FIG. The charging and discharging conditions are 2.45V constant voltage charging, current limit 10mA, 10 hours charging, 1 hour charging aftertaste, discharging current 12.5mA, and final voltage 1.75V. The discharge time of this carbon fiber-containing battery was longer than that of the battery of Comparative Example 1, shown below, in which carbon fiber was not added. Comparative Example 1 A thin sealed lead-acid battery having a thickness of 0.8 ms+ was produced in the same manner as in Example 1 except that the carbon fiber described above was not used. The results of a charge/discharge test conducted under the same conditions as in Example 1 are shown in FIG. The discharge time is shorter than that of batteries with carbon fiber added. Comparative Example 2゜Grain size is approximately 600 μm, (002) spacing is 3.39
Å, Lc (002) = 895 Å, La (110) = 4
A paste was prepared in the same manner as in Example 1, except that anisotropic graphite of 62 people was used at 0.4 wt% based on the lead powder instead of the crystalline hollow carbon fiber described above, and further aged.・Curing and chemical conversion treatment were performed. However, the positive electrode active material to which anisotropic graphite was added fell off during formation, and it was not possible to use it as a battery.

【Effect of the invention】

As explained above, in the present invention, carbon fibers having a crystalline graphite structure and a hollow structure are blended into the lead paste as an additive, so even if the graphite structure of the carbon fibers forms a graphite intercalation compound during chemical formation. Because it has a hollow structure, the active material does not fall off, and the formation of graphite intercalation compounds improves the utilization rate of the active material, making it possible to increase the capacity of thin lead-acid batteries. Moreover, there is no need to change conventional manufacturing processes such as applying the paste to the current collector, aging, and chemical conversion steps.

[Brief explanation of the drawing]

Figures 1 and 2 are scanning electron micrographs and transmission electron micrographs showing the shapes of the carbon fibers used in the present invention, respectively. Figure 3 is a comparison of discharge time curves with respect to the number of charge/discharge cycles of examples of the present invention. FIG. 4 is a perspective view showing a structural example of a thin storage battery. 1.7... Case, 2... Current collector for positive electrode, 3... Positive electrode active material, 4... Current collector for negative electrode, 5... Negative electrode active material, 6... Electrolyte.

Claims (1)

[Scope of Claims] 1) A thin lead-acid battery having an electrode plate composed of a current collector made of lead or a lead alloy and an active material in close contact with the surface of the current collector, wherein the active material is substantially A thin lead-acid battery characterized by having a crystalline graphite structure and containing hollow carbon fibers as an additive. 2) The spacing between the (002) planes of the carbon fiber is d(002
)≒3.4 Å, the crystallite sizes of the (002) and (110) planes are both Lc (002) > 100 Å, La
(110) > 100 Å and 1360 cm^-^
The intensity ratio of the Raman bands of 1 and 1580 cm^-^1 (I
_1_3_6_0/I_1_5_6_0) is 0.25~
2. The thin lead-acid battery according to claim 1, wherein the lead-acid battery has a diameter of 0.18.