JPH09306465A - Cylindrical secondary cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cylindrical secondary cell having high output density and a long life. SOLUTION: A collector terminal 11 comprises a disk-shaped flat plate part 12 and a columnar protruded part 3 protruded to one side from the center of this flat plate part 12. In an opposite side to a side provided with the protruded part 3 of the flat plate part 12, a plurality of slightly protruded protrusion parts 13 are formed. This protrusion part 13, in accordance with its forming length, is divided into three kinds of protrusion part 13a to 13c. In the case of welding the protrusion part 13 to a lead of a positive electrode plate of a collector, as going to an outside from an inside on a diametric direction, a lead per one peripheral round and the number of contact points of the protrusion part 13 are increased, dispersion of a space of this contact point is also set to within a small range.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a cylindrical secondary battery, and more particularly to a structure for collecting electric charge in an electrode plate.

[0002]

2. Description of the Related Art Recently, as a power source for electric vehicles and electric forklifts,
Demand for alkaline storage batteries is increasing. In particular, among alkaline storage batteries, nickel-hydrogen secondary batteries having a hydrogen storage alloy electrode as a negative electrode have a large energy capacity, and have been attracting attention as power sources for the electric vehicles and electric forklifts. Further, the nickel-hydrogen secondary battery is classified into a cylindrical type, a rectangular type, and the like depending on its shape. Among them, the cylindrical type has an advantage that it can be widely applied to various devices by making the size compatible with the dry battery.

FIG. 8 is a diagram for explaining the structure of a nickel-hydrogen secondary battery using, for example, a current collecting terminal system as a conventional cylindrical secondary battery. The configuration of the conventional cylindrical secondary battery 40 will be described with reference to FIG.

As shown in FIG. 8, a conventional cylindrical secondary battery 40 has a cylindrical case (container) 41 in which a positive electrode plate,
An electrode assembly composed of a negative electrode plate and a separator (hereinafter,
42), a current collector terminal 43 connected to one end of the current collector 42, and an electrolyte solution (not shown), and a groove is formed in the upper part of the case 41 in this state. , The sealing plate 4 in which the projection 45 of the collector terminal 43 is inserted into the groove
4 are brought into contact with each other via packing, and then the sealing plate 44
Is fixed to the case 41.

The current collector 42 uses, for example, a positive electrode plate, a negative electrode plate, and a plate-shaped separator, and a separator is inserted between the positive electrode plate and the negative electrode plate to form a positive electrode plate and a negative electrode plate. It is manufactured by winding up and down in a spiral shape. Leads for current collection are provided on the positive electrode plate and the negative electrode plate.

FIG. 9 is a view for explaining the shape of the collector terminal 43. 9A is a front view thereof, and FIG. 9B is a side view thereof. The front view shows the shape of the current collecting terminal 43 when viewed from the direction indicated by the arrow in FIG.
The side view shows the shape of the current collecting terminal 43 when viewed from the direction of arrow B in FIG.

The collector terminal 43 is shown in FIGS. 9 (a) and 9 (b).
As shown in FIG. 5, the protrusion 45 and the plate-shaped flat plate portion 46 having the protrusion 45 in the central portion are provided. The protrusion 45 protrudes outside from the hole of the sealing plate 44 and serves as a positive electrode terminal of the cylindrical secondary battery 40 (see FIG. 8). In addition, a plurality of small protruding protrusions 47 are formed on the surface (lower surface) of the flat plate portion 46 opposite to the side where the protruding portions 45 are provided.

A in FIG. 9B shows an end of the flat plate portion 46, and FIG. 9C is an enlarged view of a portion indicated by A. The protrusion 47 is provided to connect (weld) the current collector terminal 43 to the positive electrode plate of the current collector 42, and is provided linearly with respect to the flat plate portion 46.

FIG. 10 is a view for explaining how the projection 47 is connected (welded) to the current collector 42. The current collector 42 shown in the same figure is as viewed from the direction of arrow A shown in FIG. In the figure, 49 indicates a lead provided on the positive electrode plate. Since the current collector 42 is manufactured by winding the positive electrode plate, the negative electrode plate, and the separator as described above, the lead 49 is also formed in a spiral shape. Further, the total of eight lines 50 shown in FIG.
The protrusion 47 provided on the lower surface of the flat plate portion 46 is attached to the current collector 4
It is projected on 2. Therefore, the collector terminal 43 is connected to the positive electrode plate of the collector 42 at the intersection b of the line 50 and the line indicating the lead 49. The other negative electrode plate is similarly connected to the current collector for the negative electrode plate, and the current collector is welded to the bottom portion 41a (see FIG. 8) of the case 41.

FIG. 11 is a view showing an example of the positive electrode plate welded to the collector terminal 43. FIG. 11A shows the entire positive electrode plate 51 wound in a spiral shape in an expanded manner. In the conventional cylindrical secondary battery 40, as shown in FIG.
(Note that this welded portion B is a group of 8 welds including the above-mentioned eight intersection points b.) The interval became longer from the inside to the outside of the positive electrode plate 51 to be wound. That is, the distance between the welded portions B was different between the inside and the outside of the positive electrode plate 51. FIG. 11B is a partially enlarged view of the welded portion B.

When electric charges move in a conductor, the electric resistance value increases according to the length of the path along which the electric charges move. For this reason, due to the variation in the length between the intersection points b (welded portions B), the positive electrode plate 51 has a bias in the ease of movement of the charges. The variation in the length between the intersection points b (welded portion B) causes the following problems.

The power density of the battery (power that can be taken out per unit mass or unit volume of the battery) is correlated with the magnitude of the internal resistance value. The internal resistance can be roughly classified into a physical resistance as a path through which charges move and a reaction resistance of an active material reaction. The apparent internal resistance is represented by the sum of the resistances of the electrode plate, the electrolytic solution (electrolyte), and other components.

If the easiness of the movement of the charges in the electrode plate is biased, the current distribution is biased. The bias in the current distribution acts to substantially reduce the area of the current path. Therefore, the reaction resistance value is increased,
There was a problem that the output density was reduced.

In the portion where the charge easily moves, the reactivity becomes higher than in the portion where the charge does not move. Therefore, there is a problem that the active material utilization frequency is biased, and the active material in the vicinity of the portion where the electric charge easily moves is overused and deteriorates faster than the vicinity of the portion in which the charge does not easily move, which shortens the battery life. there were.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a cylindrical secondary battery having a high output density and a long life.

[0016]

A cylindrical secondary battery of the present invention comprises an electrode assembly formed by spirally winding a positive electrode plate and a negative electrode plate with a separator interposed between the positive electrode plate and the negative electrode plate. The positive electrode plate is connected to the positive electrode current collector terminal at the upper or lower end of the positive electrode plate and the negative electrode current collector terminal is connected to the lower end or upper end of the negative electrode plate. The number of connection points per circle to connect to the terminal and the number of connection points per circle to connect the negative electrode plate to the negative electrode current collector terminal are respectively determined according to the position in the radial direction of the electrode assembly. It is increased from the innermost side to the outermost side of the body.

In the above structure, the connection points on the positive electrode plate and the negative electrode plate per one circle are the connection points of the positive electrode plate and the negative electrode plate according to the radial position of the electrode assembly. As the number increases, it is desirable to arrange them so that the intervals between the connection points are equal to each other.

Electricity has the property of flowing along a path that easily flows (having a small resistance value). The resistance value increases in proportion to the length of the path through which the current flows. For example, the average length of the path through which electric charge existing at a certain point on the positive electrode plate goes to the connection point (the connection point in the vicinity) becomes longer as the number of the connection points becomes smaller, and the resistance value of the path increases. Further, the variation in the resistance value (length) of the path depending on the position on the positive electrode plate also becomes large. Therefore, the current distribution is biased.

When the number of connection points per circumference of the positive and negative electrode plates is increased from the innermost side to the outermost side of the electrode assembly, in other words, the longer the circumference, the more When the number of connection points per circumference is increased, the variation in the average length of the paths along which electric charges move for each connection location is suppressed, and the variation in the length between the paths is also suppressed. This reduces the bias in the current distribution. Furthermore, if the intervals between the connection points are made equal, there is no variation in the average length of the paths between the connection points, and the current distribution becomes more uniform.

If the current distribution is uneven in the electrode plate, the reaction of the active material easily occurs in the place where a large amount of current flows,
Otherwise, the reaction of the active material is unlikely to occur. Therefore, the active material is partially used, and the reaction resistance due to uneven distribution of the reaction portion increases. In addition, an increase in reaction resistance that reduces the utilization rate of the active material causes a decrease in output density and the like. The uneven distribution of the reaction parts, that is, the uneven use frequency of the active material, rapidly deteriorates the overused active material and shortens the battery life. When the utilization rate of the active material is low, the values of output density, energy density, capacity, etc. also become small. These are avoided by making the current distribution uniform in the positive and negative electrode plates.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings. The present embodiment applies the present invention to a nickel-hydrogen storage battery.

FIG. 1 is an external view of a cylindrical secondary battery according to this embodiment. In the figure, a cylindrical secondary battery 1
After inserting the electrolytic solution (electrolyte), the electrode assembly (see FIG. 2) and the like into the cylindrical case 2, a groove 2b is formed in the upper part of the case 2 and an insulating plate is formed in the groove 2b. A sealing plate (not shown) provided with a safety valve is brought into contact with a gasket (not shown), and the sealing plate is caulked and fixed by a clamping method.

FIG. 2 is a diagram showing the structure of the electrode assembly 4. In the electrode assembly 4, as shown in the figure, a separator 5, a negative electrode plate 6, a separator 7 and a positive electrode plate 8 are stacked in this order by shifting the negative electrode plate 6 and the positive electrode plate 8 vertically. It is manufactured by winding the positive electrode plate 8 inward and spirally. After that, the electrode assembly 4 is replaced with the current collector 4 '.
I will call it.

The cylindrical secondary battery 1 is a nickel-hydrogen storage battery as described above. Therefore, nickel oxide is used for the positive electrode plate 8 and hydrogen storage alloy is used for the negative electrode plate 6. Leads 9 and 10 are provided at one ends of the negative electrode plate 6 and the positive electrode plate 8, respectively. These leads 9 and 10 are for improving current collecting efficiency, and are thin plate-shaped conductors containing nickel, for example, attached to the negative electrode plate 6 and the positive electrode plate 8 by welding. The separators 5 and 7 are non-woven fabrics made of synthetic resin.

FIG. 3 is a diagram for explaining the shape of the collector terminal 11. The figure (a) is the side view, and the figure (b).
Is a rear view thereof. This rear view shows the shape as seen from the direction a shown by the arrow in FIG.

As shown in FIG. 3, the collector terminal 11 is composed of a disk-shaped flat plate portion 12 and a cylindrical projection portion 3 protruding from the center of the flat plate portion 12 to one side. As shown in FIG. 1, the projecting portion 3 is to be inserted into the hole of the sealing plate and project to the outside to serve as a positive electrode terminal of the cylindrical secondary battery 1.

Further, as shown in FIG. 3B, a large number of slightly protruding projections 13 are formed on the surface of the flat plate portion 12 opposite to the side where the projection 3 is located. This protrusion 13
The current collector terminal 11 is provided so that the lead 10 can be welded well. The protrusion 13 is divided into three types, that is, the protrusions 13a to 13c, depending on the length of the protrusion 13 formed. Here, when the current collector 4 ′ is radially divided into three equal parts from the innermost part to the inner part, the middle part, and the outer part, the protruding part 1
3a is formed linearly in the radial direction so as to cover the entire current collector 4'in the radial direction. Similarly, the protrusion 13
b is formed so as to cover the middle portion and the outside, and the protrusion 1
3c is formed so as to cover the outside.

One end of each of the protrusions 13a to 13c reaches the circular edge of the flat plate portion 12, respectively. From this, when one end of the flat plate portion 12 on the edge side is expressed as a base point, the base points of the respective protrusions 13a to 13c are divided into equal intervals on the circumference of the flat plate portion 12 in order from the longer one. The position is. Specifically, the base points of the three protrusions 13a divide the circumference into three equal parts, and the base points of the three protrusions 13b divide the arc divided by the protrusions 13a into two equal parts (the entire circumference is The base points of the six protrusions 13c are located at positions that divide the arc divided by the protrusions 13a and 13b into two equal parts (the entire circumference is divided into 12 equal parts). still,
Although not shown, the current collector terminal for the negative electrode plate 6 provided below the cylindrical secondary battery 1 is also provided with a protrusion similar to the protrusion 13 of the current collector terminal 11.

Next, a method of manufacturing the cylindrical secondary battery 1 having the current collector 4'and the current collector terminal 11 will be described in detail. First, the current collector 4'is manufactured. This current collector 4 '
As described above, the positive electrode plate 8 and the negative electrode plate 6 are vertically displaced (the direction intersecting the longitudinal direction of the electrode plates), and the separators 5 and 7 are sandwiched and wound up. Since the positive electrode plate 8 and the negative electrode plate 6 are vertically displaced from each other in the current collector 4'manufactured in this way, the leads 9 and 10 of the respective electrode plates 6 and 8 are respectively connected to the current collector 4 '. 'Is protruding from both ends.

When the current collector 4'is manufactured in this way,
A collector terminal for the negative electrode is connected to the negative electrode side of the current collector 4 '. Specifically, the current collecting terminal is connected by spot welding from the side opposite to the side where the protrusion is formed.

After that, the current collector 4'welded with the current collector terminal for the negative electrode is placed in a case (battery can) with the current collector terminal side first.
2, and the current collecting terminal is welded to the bottom 2a of the case 2. As a result, the current collector 4'is fixed inside the case 2, and the bottom portion 2a serves as a negative electrode terminal.

When the current collector 4'is fixed to the case 2, next, the current collector terminal 1 described with reference to FIG. 3 is attached to the positive electrode side of the current collector 4 '.
1 is connected. This connection is also made by spot welding as in the case of the current collector terminal for the negative electrode.

FIG. 4 is a view for explaining a welded portion between the current collector 4'and the current collector terminal 11. As shown in the figure, the protrusions 13 (13 a to 13 c) of the collector terminal 11 are connected (welded) to the leads 10 protruding from the end of the positive electrode plate 8. That is, the flat plate portion 12 of the collector terminal 11 is formed with the three types of protrusions 13a to 13c having different lengths as described above. Lines 13a 'to 13c' shown in FIG.
The projections 13a to 13c formed above are projected onto the end of the current collector 4 '. Therefore, each line 13a '
~ 13c 'and the line showing the lead 10 at the intersection of the collector terminal 1
1 is connected (welded) to the positive electrode body 8 of the current collector 4 '.

When the welding of the current collecting terminal 11 is completed, the electrolytic solution is injected into the case 2 to form the groove 2b in the upper part of the case 2. The groove 2b is formed in a position where the upper portion of the current collector terminal 11 is held so that the current collector 4'and the current collector terminal 11 placed in the case 2 do not move. After that, an insulating plate / gasket (not shown) is inserted and the case 2 is sealed with a sealing plate. The sealing plate is provided with a hole through which the protruding portion 3 of the collector terminal 11 is inserted and a safety valve. The sealing with the sealing plate is performed by a clamping method in which the sealing plate is brought into contact with the groove 2b through the insulating plate / gasket while inserting the protruding portion 3 of the collector terminal 11 into the hole and then caulking and fixing the sealing plate. .

When the sealing plate is attached to the case 2 as described above, the tip of the case 2 is bent toward the sealing plate. After the sealing plate is attached, the front end of the sealing plate is welded to the sealing plate by laser welding or the like to seal the inside of the case 2 (cylindrical secondary battery 1). This sealing completes the assembly of the cylindrical secondary battery 1. After that, charging and discharging are repeated to activate the battery 1.

An electromotive reaction occurs due to the charge and discharge, and charges move in the electrode plate. This electromotive reaction is as follows. The electromotive reactions that occur on the positive electrode plate 8 and the negative electrode plate 6 are shown below.

Reaction of positive electrode: NiOOH + H ₂ O + e ⁻ ⇔
Reaction of Ni (OOH) ₂ + OH ^- negative electrode: MHx + xOH ^- ⇔M + xH ₂
O + xe ^- where M is a hydrogen storage alloy and x is an integer determined by the hydrogen storage alloy.

In the spot welding for connecting the collector terminal 11 to the collector 4 ', electricity easily flows in the vicinity of the position where the welding rod comes into contact, and it is not possible to satisfactorily perform welding in a place where little electricity flows. Usually, in the process, the position where the welding rod is brought into contact is changed and the process is performed a plurality of times.

FIG. 5 is a view showing the positive electrode plate 8 welded to the collector terminal 11. FIG. 5 is a developed view of the positive electrode plate 8 which is wound in a spiral shape and is schematically shown. Reference numeral 16 in FIG. 5 denotes a welded portion to which the protruding portion 13 of the collector terminal 11 is welded.

As shown in FIG. 3B, the base points of the three kinds of protrusions 13a to 13c formed on the collector terminal 11 are such that the circular edges of the flat plate portion 12 are divided at equal intervals. The position. The protrusions 13a to 13c are formed from their base points toward the center. The number of protrusions 13 on the circumference is
It increases as it goes outside. Therefore, the length between the adjacent welded portions 16 of the lead 10 does not change so much depending on the radial position in the wound state, and is substantially equal.

FIG. 6 is a diagram for explaining the flow of charges in the positive electrode plate 8. The positive electrode plate 8 shown in FIG. 6 is also an outline of the positive electrode plate 8 which is wound in a spiral shape. In FIG. 6, the arrows shown in the electrode plate represent the flow of charges.

FIG. 6A is a diagram for explaining the flow of charges in the positive electrode plate 8 according to this embodiment. In the present embodiment, as shown in FIG. 5, the lengths between adjacent welded portions 16 are substantially equal. Therefore, as shown in FIG. 6A, the movement of charges is not biased by the position of the positive electrode plate 8 (position in the radial direction), and the movement of charges is uniform. Therefore, the charge distribution is also uniform.

FIG. 6B is a diagram for explaining the flow of charges in the conventional positive electrode plate 8. FIG. 6 (b) shows an example of the related art for comparison with the present invention. As shown in FIG. 6B, the positive electrode plate 52 is provided with a lead 53 at one end thereof, and the lead 53 has a total of 9
Individual welds 54 are formed. However, since the lengths of the adjacent protrusions 54 have a large variation width, the movement of the electric charges is concentrated in the vicinity of the welded portion 54 due to the difference in the ease of electricity flow. A region 55 surrounded by a broken line in FIG.
Is a region where the movement of charges hardly occurs. In this region 55, electromotive reaction with the active material in the electrolytic solution hardly occurs.

As described above, in the present embodiment, the movement of charges in the positive electrode plate 8 is made uniform, that is, the deviation of the current distribution is greatly improved, as compared with the conventional case. This also applies to the negative electrode plate 6. Therefore, the following effects can be obtained.

First, since a current flows uniformly through the electrode plates 6 and 8, the active material in the electrolytic solution reacts with the entire electrode plates 6 and 8. As a result, the reaction resistance is reduced and the power density is improved. Further, since the utilization rate of the active material is improved, the energy density, the battery capacity, etc. can be improved.

The active material of the battery gradually deteriorates, and when the deterioration progresses to some extent, the battery reaches the end of its life (when the capacity is 80% or less of the nominal capacity in the standard). If the currents flowing through the electrode plates 6 and 8 are biased, the active material in the portion where the charge easily flows is overused, and the active material in that portion deteriorates quickly, so that the battery life is shortened. In contrast,
In the present embodiment, since the current flow is made uniform, the active material in the electrolytic solution is deteriorated in the same manner as a whole, and the deterioration progresses slowly. Therefore, the battery life can be extended.

Diffusion of the active material cannot be expected so much during continuous discharge or rapid charge. Therefore, in a secondary battery that is repeatedly used by being charged, the uneven current distribution rapidly deteriorates a partial active material, shortens the life of the battery, and causes a large decrease in charging efficiency. These problems are serious in practical use. However, the present invention
By making the current distribution uniform, it is possible to prolong the service life of the battery, discharge for a longer time, and improve the charging efficiency, and avoid the above-mentioned problems. Therefore, the present invention can provide the user with a secondary battery that can be used more comfortably.

In the present embodiment, the present invention is applied to the cylindrical secondary battery 1 which adopts the current collecting terminal method as the current collecting method. However, the present invention is different in the current collecting method to be adopted. Regardless, it can be applied to a cylindrical secondary battery. For example, when the tab method is adopted as the current collecting method, as shown in FIG. 7, a plurality of tabs 17 may be provided on the positive electrode plate 8 so that adjacent intervals are equal. In this case, it is not necessary to provide a protrusion on the positive electrode current collector terminal side, and a disk-shaped current collector terminal may be used, for example.
This also applies to the other negative electrode plate 6.

The cylindrical battery to which the present invention can be applied is not limited to the nickel-hydrogen storage battery of this embodiment. The present invention can be widely applied to other types of secondary batteries such as nickel-cadmium storage batteries and lithium-ion secondary batteries.

In the pattern of the projections 13 formed on the flat plate portion 12 of the collector terminal 11, the gaps between the adjacent welded portions 16 are not completely equal. This is because the pattern is monotonous in terms of the ease of spot welding and the ease of manufacturing the current collector terminal 11. Various patterns are conceivable as the pattern of the projection 13 formed on the current collector terminal 11, but since the length of the circumference is proportional to the diameter (radius), the pattern goes from the inner peripheral side to the outer side in any case. Along with this, the number of points per one circle for contacting the current collector terminal 11 and the lead 10 increases, in other words, the protrusion 3a of the sealing plate 3 which is the positive electrode terminal and the lead 10 via the current collector terminal 11.
It is sufficient if the number of points per circle on which is connected is increased.

[0051]

As described above, according to the present invention, the number of connection points on one circumference of the positive and negative electrode plates is sequentially increased from the innermost side to the outermost side of the electrode assembly, In other words, the longer the circumference is, the more the number of connection points per circumference is increased, so that the current distribution in each electrode plate can be made uniform. As a result, it is possible to improve the utilization rate of the active material while avoiding uneven distribution of the reaction portion of the active material. As a result, it is possible to obtain effects such as a decrease in internal resistance, a longer battery life, and an improvement in output density, energy density, capacity and the like.

When the intervals between the connection points are made equal,
Since it is possible to make the current distribution in each electrode plate more uniform, it is possible to obtain the greater effect described above.

[Brief description of drawings]

FIG. 1 is an external view of a cylindrical secondary battery according to the present embodiment.

FIG. 2 is a diagram showing a configuration of an electrode assembly (current collector).

FIG. 3 is a diagram illustrating the shape of a collector terminal.

FIG. 4 is a diagram illustrating a current collector weld portion.

FIG. 5 is a view showing a positive electrode plate welded to a collector terminal.

FIG. 6 is a diagram illustrating the flow of charges in a positive electrode plate.

FIG. 7 is a diagram showing a positive electrode plate used in another embodiment.

FIG. 8 is a diagram illustrating a configuration of a conventional cylindrical secondary battery using a collector terminal method.

FIG. 9 is a diagram illustrating the shape of a conventional collector terminal.

FIG. 10 is a diagram for explaining how the protrusion is connected (welded) to the electrode assembly.

FIG. 11 is a view showing an example of a positive electrode plate connected (welded) to a conventional collector terminal.

[Explanation of symbols]

 4'current collector 5, 7 separator 6 negative electrode plate 8 positive electrode plate 9, 10 lead 11 current collector terminal 12 flat plate portion 13, 13a, 13b, 13c protruding portion 16 welded portion 17 tab

Claims (2)

[Claims] 1. An electrode assembly formed by spirally winding a positive electrode plate and a negative electrode plate with a separator interposed between the positive electrode plate and the negative electrode plate is housed in a cylindrical container together with an electrolytic solution. In a cylindrical secondary battery in which a positive electrode current collector terminal is connected to the positive electrode current collector terminal and a negative electrode current collector terminal is connected to the lower end or the upper end of the negative electrode plate, the positive electrode plate is connected to the positive electrode current collector terminal per circle. And the number of connection points per circumference for connecting the negative electrode plate to the negative electrode current collector terminal, depending on the radial position of the electrode assembly. A cylindrical secondary battery, wherein the number is increased from the peripheral side toward the outermost peripheral side. 2. The positive electrode plate according to the radial position of the electrode assembly, and the positive electrode plate according to an increase in the number of connection points per circumference of the negative electrode plate,
The cylindrical secondary battery according to claim 1, wherein the connection points on the negative electrode plate are arranged so that the intervals between the connection points are equal.