KR101464514B1 - Anode electrode of nickel base secondary battery improving battery service life and electrode structure of nickel base secondary battery including the same - Google Patents

Abstract

In the present invention, disclosed are an anode electrode of a nickel based secondary battery with improved battery service life which can reduce internal resistance due to the improvement of electrical conductivity and prevent the center part of the anode from swelling according to charging and discharging by using a current collector with two or more layers as an anode, and to a nickel based secondary battery stack including the same. The anode electrode of the nickel based secondary battery, according to the present invention, comprises a main current collector having a foam structure; an anode active material which is coated on the main current collector; and a sub current collector which is arranged on the anode active material and is compressed on the anode active material and the main current collector.

Description

TECHNICAL FIELD [0001] The present invention relates to a positive electrode for a nickel-based rechargeable battery improved in battery life and an electrode structure of a nickel-based rechargeable battery having the nickel-

The present invention relates to a positive electrode for a nickel-based secondary battery and a nickel-based secondary battery electrode structure having the same, and more particularly, to a positive electrode having a multilayer structure of two or more layers, A positive electrode for a nickel-based rechargeable battery improved in battery life that can compensate for swelling of a central portion of the positive electrode due to swelling due to charging / discharging, and a nickel- Electrode structure.

Recently, various environmental regulations have been implemented as a commitment to environmental conservation in each country. Therefore, lead batteries and nickel / cadmium batteries have been replaced with nickel / hydrogen and lithium ion batteries in small batteries, but lead acid batteries and nickel / cadmium batteries are still used in industrial large batteries because there is no alternative battery. Therefore, there is a growing interest in environmentally friendly large-capacity batteries, and the development of technologies therefor is intensifying.

Among them, nickel (Ni) / zinc (Zn) secondary batteries, which can replace lead acid batteries, have similar volume and volume energy densities, higher operating voltages than 1.6 [V / cell] power density is 875 [W / kg], which is higher than 535 [W / kg] of the lead acid battery, and the cycle life which reaches 80% of the maximum discharge capacity is 600 times or more. Compared to 200 ~ 700 times, there is a relatively stable advantage.

Generally, the secondary battery includes a positive electrode, a negative electrode arranged in parallel with the positive electrode, and a separator interposed between the positive electrode and the negative electrode to prevent the positive electrode and the negative electrode from being in electrical contact with each other. And has a structure impregnated in a case for housing.

However, since the conventional secondary battery has a simple plate structure with both the anode and the cathode, after the unit cell is tightened, the unit cell is impregnated with the electrolyte contained in the case, Due to the swelling phenomenon, the spacing between the positive electrode and the negative electrode is not uniform, so that the charge / discharge efficiency is drastically reduced, and the outermost edge of the positive electrode protrudes to the outside of the separator by the swelling phenomenon Short-circuiting short-circuiting with the cathode occurred.

A related prior art is Korean Patent Laid-Open Publication No. 10-2008-0114330 (published Dec. 31, 2008), which discloses an anode plate for a nickel / zinc secondary battery for increasing the reaction area and a manufacturing method thereof.

In the present invention, by applying a current collector having a multilayer structure of two or more layers as a positive electrode, the internal resistance can be reduced due to the improvement of the electrical conductivity, and the swelling phenomenon of the central portion of the positive electrode due to charging / discharging A positive electrode for a nickel-based secondary battery improved in life span of a battery and an electrode structure of a nickel-based secondary battery having the same.

According to an aspect of the present invention, there is provided a negative electrode for a nickel-based secondary battery having improved battery life, comprising: a main collector having a foam structure; A cathode active material coated on the main current collector; And a sub collector disposed on the cathode active material and pressed onto the cathode active material and the main current collector.

According to an aspect of the present invention, there is provided an electrode structure for a nickel-based rechargeable battery having improved battery life, comprising: a main current collector having a foam structure; a cathode active material coated on the main current collector; A positive electrode disposed on the positive electrode active material and having a sub current collector pressed onto the positive electrode active material and the main current collector; A negative electrode disposed so as to face the positive electrode; And a separator interposed between the positive electrode and the negative electrode, the separator electrically separating the positive electrode and the negative electrode.

The electrode structure for a nickel-based secondary battery having improved battery life according to the present invention and the electrode structure for a nickel-based secondary battery having the same have a structure in which an anode is formed by sequentially stacking a main collector, a cathode active material, It is possible to prevent the cathode active material coated on the main current collector from being removed and to increase the electric junction area with the main current collector to reduce the internal resistance of the electrode and improve the battery life.

In addition, the electrode structure of the nickel-based secondary battery having improved battery life according to the present invention and the electrode structure of the nickel-based secondary battery having the same has a structure in which the sub- current collector pressed on the main current collector coated with the positive electrode active material reinforces the strength of the positive electrode To compensate for the swelling phenomenon of the positive electrode even if charging / discharging is carried out for a long period of time in a state of being impregnated with the electrolytic solution contained in the case after the secondary battery is tightened, It is possible to improve charge / discharge efficiency and also to prevent a short failure in which the anode and the cathode are short-circuited.

1 is a cross-sectional view illustrating an electrode structure of a nickel-based secondary battery according to an embodiment of the present invention.
2 is a cross-sectional view illustrating a positive electrode for a nickel-based secondary battery according to an embodiment of the present invention.
3 is a cross-sectional view illustrating a positive electrode for a nickel-based secondary battery according to a modification of the present invention.
4 is a graph showing the results of measurement of battery life characteristics for the specimen according to Example 1 and Comparative Example 1. Fig.

BRIEF DESCRIPTION OF THE DRAWINGS The advantages and features of the present invention, and how to accomplish them, will become apparent by reference to the embodiments described in detail below with reference to the accompanying drawings. It should be understood, however, that the invention is not limited to the disclosed embodiments, but may be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Is provided to fully convey the scope of the invention to those skilled in the art, and the invention is only defined by the scope of the claims. Like reference numerals refer to like elements throughout the specification.

BRIEF DESCRIPTION OF THE DRAWINGS The above and other objects, features and advantages of the present invention will be more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which: FIG.

FIG. 1 is a cross-sectional view illustrating an electrode structure of a nickel-based secondary battery according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view illustrating a nickel-based secondary battery according to an embodiment of the present invention.

Referring to FIGS. 1 and 2, a nickel-based secondary battery electrode structure 100 according to an embodiment of the present invention includes a cathode 120, a cathode 140, and a separator 160.

The positive electrode 120 includes a main current collector 122 having a foam structure, a positive electrode active material 124 coated on the main current collector 122 and a negative electrode active material 124 disposed on the positive electrode active material 124, And a sub current collector 126 pressed against the current collector 122. At this time, the anode 120 may be provided with a positive terminal (not shown) for charging / discharging the secondary battery.

At this time, it is preferable that the main current collector 122 has a first thickness and the sub current collector 126 has a second thickness that is equal to or smaller than the first thickness. It is advantageous to compensate for the swelling of the central portion of the main current collector 122 when the sub current collector 126 is thicker than the main current collector 122, And it may be difficult to uniformly maintain the distance between the anode 120 and the cathode 140. [

At this time, each of the main current collector 122 and the sub current collector 126 preferably has a nickel foam form. As the positive electrode active material 124, nickel hydroxide (Ni (OH) ₂ ) and nickel hydroxide may be mixed with an additive. In addition to the additive, a binder and a conductive agent may be further mixed.

The main current collector 122 has a first area, the cathode active material 124 has a second area smaller than the first area, the sub collector 126 has a smaller area than the first area, It is preferable to have a large third area. It is preferable that the sub current collector 126 has an area equal to or larger than the area of the cathode active material 124. This is because the sub current collector 126 must be designed to cover the entire area of the cathode active material 124, It is possible to prevent the cathode active material 124 coated on the entire body 122 from being detached from the outside and reduce the internal resistance of the electrode by increasing the electrical junction area with the main current collector 122, The life can be improved.

The cathode 140 is disposed so as to be opposite to the anode 120. The cathode 140 is provided with a negative terminal (not shown) for charging / discharging the secondary battery. At this time, nickel may be used for the cathode 140, but the present invention is not limited thereto. The cathode 140 may have a form in which a negative active material (not shown) is coated on one side or both sides of a current collector (not shown) having a nickel-containing foam structure.

As the anode active material, zinc oxide and zinc oxide may be mixed with an additive. In addition to the additive, a binder and a conductive agent may be further mixed. As such an anode active material, a metal hydride (MH) alloy, cadmium oxide, or the like may be used instead of zinc oxide. Therefore, the nickel-based secondary battery unit cell according to the embodiment of the present invention may have any one of Ni-Zn, Ni-MH, and Ni-Cd secondary batteries.

The separator 160 is interposed between the anode 120 and the cathode 140 to electrically isolate the anode 120 and the cathode 140 from each other. At this time, the separator 160 may be any one selected from a polyethylene nonwoven fabric, a polypropylene nonwoven fabric, a polyester nonwoven fabric, a polyacrylonitrile porous separator, a poly (vinylidene fluoride) hexafluoropropane copolymer porous separator, a cellulose porous separator, One can be used.

Conventionally, as both the anode and the cathode have a simple plate structure, when the battery is impregnated with the electrolyte contained in the case after the nickel-based secondary battery is fastened, charging / discharging is carried out for a long period of time and the anode is swelled The gap between the positive electrode and the negative electrode is not uniform and the charging / discharging efficiency is drastically reduced. In addition, the short-circuiting phenomenon in which the outermost edge of the positive electrode is short-circuited to the negative electrode protruding outside the separator by the swelling phenomenon There was a problem that caused.

Alternatively, the nickel-based secondary battery electrode structure 100 according to the embodiment of the present invention may have a structure in which the main collector 122, the positive electrode active material 124, and the sub collector 126 are sequentially stacked, The sub current collector 126 serves as a shielding film for preventing the cathode active material 124 coated on the main current collector 122 from being detached and the electric junction area with the main current collector 122 So that the internal resistance of the electrode can be reduced and battery life can be improved.

In the nickel-based secondary battery electrode structure 100 according to the embodiment of the present invention, the sub current collector 126, which is pressed onto the main current collector 122 coated with the positive electrode active material 124, The swelling phenomenon of the anode 120 can be compensated for even if charging / discharging is performed for a long period of time in a state of being impregnated with the electrolytic solution contained in the case after the tightening.

Therefore, in the nickel-based secondary battery electrode structure 100 according to the embodiment of the present invention, the sub collector 126 is pressed on the main current collector 122 coated with the positive electrode active material 124, The strength of the anode 120 is reinforced and stably attracted to the separator 160 due to its own load so that it is impregnated into the electrolytic solution contained in the case after the tightening of the electrode structure 100, It is possible to compensate for the swelling of the central portion of the anode 120. As a result, the spacing between the anode 120 and the cathode 140 can be uniformly ensured, thereby improving charge / discharge efficiency Not only the anode 120 and the cathode 140 are short-circuited, but also the short-circuit failure can be prevented in advance.

3 is a cross-sectional view illustrating a positive electrode for a nickel-based secondary battery according to a modification of the present invention.

3, the anode 120 for a nickel-based secondary battery according to a modification of the present invention includes a main current collector 122, a cathode active material 124, and a plurality of sub current collectors 126.

At this time, at least one sub-current collector 126 is stacked on the cathode active material 124, and is pressed onto the cathode active material 124 and the main current collector 122. In FIG. 3, three sub-current collectors 126, that is, the first, second and third sub current collectors 126a, 126b, and 126c are stacked in order. However, the present invention is not limited thereto. Preferably 2 to 4 persons.

At this time, the first, second and third sub current collectors 126a, 126b, and 126c may have different areas and thicknesses, but are not necessarily limited thereto, and they may all have the same area and thickness.

The electrode structure of the nickel-based secondary battery having improved battery life according to the above-described embodiment of the present invention includes a main collector, a cathode active material, and a sub collector in this order, It is possible to prevent the cathode active material coated on the cathode current collector from being detached and to increase the electrical junction area with the main current collector to reduce the internal resistance of the electrode and improve the battery life.

Also, in the nickel-based secondary battery electrode structure according to the embodiment of the present invention, the sub current collector pressed on the main current collector coated with the positive electrode active material functions to reinforce the strength of the positive electrode, It is possible to uniformly maintain the separation distance between the anode and the cathode by compensating for the swelling phenomenon of the anode even if charge / discharge is performed due to long-term use under the impregnated electrolyte solution, And it is also possible to prevent a short defect in which the anode and the cathode are short-circuited.

Example

Hereinafter, the configuration and operation of the present invention will be described in more detail with reference to preferred embodiments of the present invention. It is to be understood, however, that the same is by way of illustration and example only and is not to be construed in a limiting sense.

The contents not described here are sufficiently technically inferior to those skilled in the art, and a description thereof will be omitted.

1. Anode manufacturing

Example 1

850 g of nickel hydroxide (Ni (OH) ₂ ) powder, 10 g of carbon as a conductive material and 5 g of polytetrafluoroethylene as a binder were mixed and stirred in 1000 ml of a carboxymethylcellulose solution (CMC Solution) The slurry was applied on a metal foam current collector having a thickness of 2 mm, and then dried at 90 ° C. using a convection oven to form a cathode active material.

Next, a metal foam current collector having a thickness of 2 mm was attached to the charged cathode active material, and then the main current collector and the sub current collector coated with the cathode active material were press-pressed to produce a positive electrode having a thickness of 1.8 mm.

Comparative Example 1

Only the sub-collector pressing after the electrode fabrication was excluded in the same manner as in Example 1

Experimental Example

Nickel-based secondary batteries were prepared by using the positive electrodes prepared according to Examples and Comparative Examples, using metal foams as negative electrodes, and injecting alkaline electrolytes.

2. Evaluation of life characteristics

Table 1 shows the results of measurement of battery life characteristics for the specimens according to Examples 1 to 3 and Comparative Example 1, and FIG. 4 shows the results of measurement of battery life characteristics for the specimens according to Example 1 and Comparative Example 1. Fig.

[Table 1]

Referring to Table 1 and FIG. 4, in the case of the test piece according to Comparative Example 1, the battery life is reduced in proportion to the number of cycles.

On the other hand, in the case of the test piece according to Example 1, it can be seen that the rate of change in capacity increases irrespective of the number of cycles. This is because when the main current collector, the cathode active material and the sub current collector are sequentially stacked, It can be understood that this is due to the fact that the cathode active material coated on the main current collector is prevented from being removed and the internal resistance of the electrode is reduced due to an increase of the electric junction area with the main current collector.

Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims. These changes and modifications may be made without departing from the scope of the present invention. Accordingly, the scope of the present invention should be determined by the following claims.

100: nickel-based secondary battery unit cell 120: anode
122: main collector 124: cathode active material
126: Sub-collector 126a: First sub-collector
126b: second sub collector 126c: third sub collector
140: cathode 160: separator

Claims (9)

A main current collector having a foam structure;
A cathode active material coated on the main current collector; And
And a sub collector disposed on the cathode active material and pressed onto the cathode active material and the main current collector,
Wherein the main current collector has a first area and the cathode active material has a second area smaller than the first area and the sub collector has a third area smaller than the first area and equal to or larger than the second area And a positive electrode for a negative electrode for a nickel-based secondary battery having improved battery life.
The method according to claim 1,
The main current collector
Wherein the secondary collector has a first thickness and the sub collector has a second thickness equal to or less than the first thickness.
delete The method according to claim 1,
Each of the main current collector and sub-
Wherein the positive electrode has a nickel foam form.
The method according to claim 1,
The positive electrode active material
Nickel hydroxide (Ni (OH) ₂ ).
The method according to claim 1,
The sub-
Wherein at least one of the positive electrode active material and the negative electrode active material is laminated on the positive electrode active material, and the positive electrode active material and the main current collector are pressed to each other.
1. A positive electrode comprising: a main current collector having a foam structure; a positive electrode active material coated on the main current collector; a positive electrode disposed on the positive electrode active material and having a sub current collector pressed onto the positive active material and the main current collector;
A negative electrode disposed so as to face the positive electrode; And
And a separator interposed between the positive electrode and the negative electrode to electrically isolate the positive electrode and the negative electrode,
Wherein the main current collector has a first area and the cathode active material has a second area smaller than the first area and the sub collector has a third area smaller than the first area and equal to or larger than the second area Wherein the electrode is formed on the surface of the nickel-based secondary battery.
8. The method of claim 7,
The negative electrode
Nickel-based secondary battery electrode structure having improved battery life.
8. The method of claim 7,
The nickel-based secondary battery unit cell
And the main current collector is inhibited from swelling by the sub current collector.

Images