JP2804557B2 - Prismatic battery and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Industrial Field of the Invention The present invention relates to a prismatic battery including a cylindrical one pole and another pole disposed in a hollow portion provided at the center of the one pole, In particular, the present invention relates to a configuration of a battery and a method of molding the one electrode.

(B) Conventional technology In recent years, demand for batteries has greatly increased with the portable use of electric devices. On the other hand, the miniaturization and thinning of electric equipment have progressed, and a battery, which is a power source, inevitably requires high capacity and small size. But,
Currently widely used batteries are cylindrical and have a circular cross-section, so when multiple batteries are used side by side, when there is a gap between batteries or when batteries are stored in electrical equipment Useless space is generated in the corner portion of the battery storage space in the above. For this reason, it can be said that the cylindrical battery is disadvantageous in increasing the capacity and reducing the size.

From such a viewpoint, Japanese Utility Model Laid-Open No. 58-169659 discloses that
Attention has been paid to prismatic batteries as batteries with good volumetric efficiency and high energy density. By the way, the configuration of the prismatic battery as shown in the above-mentioned publication is usually based on the idea that the thickness of the positive electrode is kept constant, and as shown in the vertical sectional view of the battery in FIG. A pole 15 having a rectangular outer shape along the inner peripheral surface of the outer case 21 and having a hollow portion having a similar cross-sectional rectangular shape in the center is provided, and a hollow portion is provided in the hollow portion of the one pole 15. The other electrode 17 having an outer shape along the inner peripheral surface of the second member is arranged with a separator 16 interposed therebetween. However, in the battery of the above configuration, the other electrode 17
When a battery whose volume is reduced by discharge, such as a lithium electrode, is used, the discharge capacity does not become sufficiently large.

As an electrode configuration of a prismatic battery, there is also a method of using a laminated electrode configuration in which plate-like positive and negative plates are alternately stacked with a separator interposed therebetween. Is required, and the volume occupied by the current collector and the separator increases, so that the amount of effective electrode material decreases accordingly, which is disadvantageous for increasing the capacity.

(C) Problems to be Solved by the Invention It is an object of the present invention to provide a configuration of a rectangular battery capable of obtaining a high capacity without causing waste of a housing space such as a cylindrical battery, and a method of manufacturing the same.

(D) Means for Solving the Problems The prismatic battery of the present invention has a cylindrical one-sided electrode having an outer peripheral surface having a polygonal cross section and a circular hollow portion at the center, and the separator has the one-sided electrode. And the other pole located in the hollow portion and separated from the corner, the packing density of the mixture of the one pole is closer to the corner periphery than to the periphery of the outer periphery of the one pole. It is characterized in that the part which is closed is denser.

Further, in the method for manufacturing a prismatic battery of the present invention, the electrode mixture is temporarily formed into a hollow cylindrical shape having a hollow portion having a circular cross section at the center, and then the outer peripheral case is formed in an outer case having a polygonal cross section on the inner peripheral surface. By inserting the temporarily molded mixture, and then, inside the outer case, inserting a cylindrical jig into the hollow portion of the temporarily molded electrode mixture, and pressing and compressing the mixture from the upper surface. An electrode whose outer peripheral surface has a polygonal cross section along the inner peripheral surface of the outer case and has a space portion having a circular cross section at the center is formed.

(E) Function Even when one electrode having a rectangular cross section on the outer peripheral surface and having a hollow portion with a circular cross section in the center is used as the electrode configuration of the prismatic battery, the discharge performance is determined by the packing density of the one electrode mixture. Are different. That is, as compared with the case where the filling density is uniform, the discharge performance is improved when the filling density around the corner around the outer periphery of the one electrode is reduced as in the present invention. This is because, when the distance from the other electrode increases, the packing density of the peripheral portion of the corner decreases, and the amount of retained electrolyte in the peripheral portion increases accordingly, and the utilization rate of the active material improves. It is thought to be.

Further, in the production method of the present invention, the electrode mixture is temporarily molded into a hollow cylindrical shape having a hollow portion with a circular cross section in the center, and the inner peripheral surface is inserted into a rectangular outer case, and the inserted temporary case is inserted. Since the outer shape of the molded product is circular in cross section, the outer corner of the temporary molded product is inserted into the outer edge of the outer case at the time of insertion, as in the case of the outer shape of the temporary molded product having a square cross section along the inner peripheral surface of the outer case. It is unlikely to collapse due to contact, and insertion is easy. Further, after inserting the temporary molded product into the outer case, a columnar jig is inserted into the space of the temporary molded product, and the temporary molded product is pressed and compressed from the upper surface, so that the outer peripheral corner of one pole is formed. Molding can be easily performed so that the filling density of the peripheral portion of the portion is reduced.

(F) Examples Examples of the present invention are shown below, and reference is made to comparison with comparative examples.

[Example] A positive electrode mixture obtained by mixing manganese dioxide as an active material, a binder and a conductive material was pressurized with a pressing force of 1 to 5 tons,
A mixture is temporarily formed into a hollow cylindrical shape having a hollow portion having a circular cross section at the center. This mixture 1 was prepared as shown in FIGS.
As shown in FIG.
As shown in the figure, a jig 4 on a cylinder is placed in the space 3 of the mixture 1.
Is inserted and the upper surface of the mixture 1 is pressurized by a pressing jig, so that the mixture 1 ′ as shown in FIGS.
Is molded into a mixture having a rectangular shape having an outer peripheral surface in close contact with the outer case 2 and a hollow section 5 having a circular cross section at the center. When the density of the mixture thus molded is measured, the peripheral portion 6 of the outer peripheral surface of the mixture is 2.75 g / cc to 2.85 g / cc, and the portion 7 sandwiched between the peripheral portions 6 is 2.92 g / cc. And the mixture density at the corner peripheral portion 6 was lower.

Next, in order to remove moisture in the positive electrode active material, about 200
After drying at a temperature of from about 300 ° C. to 300 ° C., a plan view of the battery in FIG. 6A, a longitudinal sectional view of the battery in FIG. 6B, and FIG. 6B shown in FIG. ), A lithium negative electrode 9 is inserted into the hollow portion 5 of the positive electrode mixture 1 ′ molded in the outer case 2 via the separator 8, and a sealing lid is inserted into the opening of the outer case 2. A prismatic battery was fabricated by welding 10. In the drawing, 11 is an insulating packing, 12 is a negative electrode lead, and 13 is a negative electrode terminal. This battery is designated as A.

[Comparative Example 1] Using the same amount of the positive electrode mixture in the example, a mixture temporarily molded into a hollow rectangular tube shape having a hollow portion with a circular cross section in the center is similarly produced. As shown in FIGS. 3 (a) and 3 (b), this mixture 14 is inserted into the rectangular outer case 3, and FIG.
The mixture was molded under pressure as shown at 14 'in (b), and then a battery was assembled in the same manner as in the example. This battery is designated as B.

[Comparative Example 2] Using the same amount of the positive electrode mixture in the example, a mixture was formed into a hollow cylindrical shape having a square cylindrical hollow portion having a square cross section at the center. This mixture is inserted into a rectangular outer case and molded by pressure to form a mixture in which the outer peripheral surface of the mixture has a square shape in close contact with the outer can and has a hollow section having a rectangular cross section at the center. Next, a battery is assembled in the same manner as in the example. FIG. 9 (a) is a cross-sectional view of the battery assembled in this manner. In the hollow part formed in the center of the positive electrode mixture 15, a lithium negative electrode 17 is interposed with a positive electrode mixture via a separator 16.
It is arranged along the inner peripheral surface of fifteen. This battery is designated as C.

Each of the batteries A to C has a height of 33.5 mm and a length of one side of each of the vertical and horizontal sides is 17 mm. FIG. 7 shows discharge characteristics when each of the batteries A to C was discharged at room temperature with a load of 1 KΩ, and the discharge was stopped when the battery voltage reached 2.0 V.

As is clear from FIG. 7, the battery A has the highest discharge capacity of 1600 mAH at the end of 2.0 V and shows excellent performance. Battery B has a discharge capacity at the end of 2.0 V of 1250 mAH, which is inferior to Battery A, but is superior to Battery C of 975 mAH.

8 shows batteries A and B, and FIG. 9 shows battery C. In FIG. 8, (a) is a cross-sectional view of the battery immediately after assembly, (b) is a cross-sectional view of the battery at the time of 50% discharge, (c) is an enlarged view of a main part of (b). As described above, in the battery C, since the cross-sections of the inner peripheral surface of the positive electrode mixture 15 and the outer peripheral surface of the negative electrode 17 are square, the reaction is biased toward the corner 18 of the negative electrode 17, and the lithium of the negative electrode decreases in volume in this portion Therefore, the separator 16 is locally wavy. For this reason, it is considered that the resistance between the positive electrode and the negative electrode was increased in a portion where the separator 16 was locally corrugated, and it was difficult to discharge, and a sufficient discharge capacity could not be obtained. On the other hand, in the batteries A and B, since the cross-sections of the inner peripheral surface of the positive electrode mixture 14 ′ and the outer peripheral surface of the negative electrode 19 are circular, the reaction proceeds almost uniformly on the outer peripheral surface of the negative electrode 19. It is considered that the wave was formed relatively uniformly, and an increase in resistance between the positive electrode and the negative electrode could be suppressed.

Also, the batteries A and B have almost the same electrode configuration, but the different discharge performance is considered to be due to the reason for connection. That is, the positive electrode mixture of the battery A is as shown in FIG.
Since the pressure molding is performed from the state shown in FIG. 2B to the state shown in FIGS. 2A and 2B, a portion where the distance from the negative electrode becomes large, that is, a corner peripheral portion on the outer peripheral surface of the positive electrode mixture 1 ′ 6 is
Since the packing density of the mixture is lower than that of the portion 7 sandwiched between the corner peripheral portions 6, the amount of retained electrolyte increases, so that the reaction proceeds smoothly even at a distance from the negative electrode, and the discharge capacity is large. Become. On the other hand, in the battery B, since the filling density of the positive electrode mixture is uniform, the reactivity around the corner portion is lower than that in the battery A, and this portion cannot sufficiently contribute to the discharge reaction. Therefore, it is considered that the performance of the battery A was excellent.

(G) Effects of the Invention In the prismatic battery of the present invention, the cross section of the outer peripheral surface is a square shape, the other pole is disposed in a hollow section having a circular cross section provided at the center of one pole, and the periphery of the corner on the outer peripheral face of the one pole is provided. By reducing the packing density of the mixture in the portion, the reactivity of the peripheral portion, which is difficult to react, can be increased, and the discharge capacity can be increased.

Further, in the method for manufacturing a prismatic battery of the present invention, a mixture temporarily molded in a hollow cylindrical shape in advance is inserted into a rectangular outer case and molded in the outer case, so that the outer peripheral surface is the inner circumferential surface of the outer case. Forming an electrode having a hollow section with a circular cross section at the center with a polygonal cross section along
It is easy to insert the mixture into the outer case, and it is possible to manufacture a unipolar electrode having portions with different packing densities by a simple operation.

[Brief description of the drawings]

FIGS. 1 and 2 show an embodiment of the present invention, and FIGS. 3 and 4 show comparative examples. FIGS.
FIG. 4 and FIG. 4 show drawings after the molding of the mixture, and FIG.
Is a cross-sectional view, and (b is a longitudinal sectional view. FIG. 5 is a schematic view showing a method of molding a mixture, FIG. 6 shows a battery of the present invention, and FIG. Fig. 6 (b) is a longitudinal sectional view of the battery, Fig. 6 (c) is a sectional view taken along line XX of Fig. 6 (b), Fig. 7 is a discharge characteristic diagram, Fig. 8 is batteries A and B, and Fig. 9 The drawing shows a battery C. In these drawings, (a) is a cross-sectional view of the battery immediately after assembly, and (b) and (c) are a cross-sectional view of the battery at 50% discharge and an enlarged cross-sectional view of a main part, respectively. 1, 1 ', 14, 14' ... positive electrode mixture (one electrode), 5 ... hollow part, 8 ... separator, 9 ... negative electrode (other electrode), 2 ...
... Outer case, 6 ... Around corners. A: battery of the present invention, B, C: comparative battery.

Claims (2)

(57) [Claims] 1. A cylindrical one pole having an outer peripheral surface having a polygonal cross section and a hollow cross section having a circular cross section at the center, and the other pole located in the hollow part while being separated from the one pole by a separator. And an outer case for housing the one pole and the other pole, wherein the packing density of the mixture of the one pole is
A prismatic battery in which a portion sandwiched between the corner peripheral portions is denser than a corner peripheral portion on the outer peripheral surface of the one pole. 2. An electrode mixture is temporarily molded into a hollow cylindrical shape having a hollow section with a circular cross section at the center, and then the temporarily molded mixture is inserted into an outer case having a polygonal inner peripheral section. Then, in the outer case, a cylindrical jig is inserted into the hollow portion of the temporarily formed electrode mixture, and the mixture is pressed and compressed from the upper surface, so that the outer peripheral surface is formed inside the outer case. A method for manufacturing a prismatic battery, comprising forming an electrode having a polygonal cross-section along the peripheral surface and having a space portion having a circular cross-section at the center.