KR20060060077A - Battery pack of high output and large capacity - Google Patents

Abstract

The present invention relates to a high output large capacity battery pack that can be used as a power source for electric vehicles, etc. In a battery pack connected in a series and parallel manner so that a plurality of unit cells can provide electricity with a high output large capacity, each unit battery The positive electrode tab and the negative electrode tab protrude together at one end of the unit cell, and the electrode tab of the first unit cell is connected in series with the electrode tab of the adjacent second unit cell by an electrode lead, thereby reducing the temperature of the positive electrode tab. Provided is a battery pack capable of lowering and ultimately suppressing battery deterioration.

Description

Battery Pack of High Output and Large Capacity             

1 is a schematic diagram of a structure in which unit cells are connected in series in a high power / large capacity battery pack according to the prior art;

2 and 3 are schematic diagrams of a structure in which unit cells are connected in series in a high output / large capacity battery pack according to an exemplary embodiment of the present invention.

<Brief Description of Drawings>

100, 101, 102: unit cell

200, 201, 202: positive electrode tab

300, 301, 302: negative electrode tab

400: electrode lead

The present invention relates to a battery pack of high output large capacity, and more particularly, in the battery pack is connected in a series and parallel manner so that a plurality of unit cells to provide electricity at a high output large capacity, each unit battery is a positive electrode tab And the negative electrode tab protrude together at one end of the unit cell, and the electrode tab of the first unit cell is connected to the electrode tab of the adjacent second unit cell in series by an electrode lead to reduce the temperature of the positive electrode tab. To provide a structure.

One problem with existing vehicles that use fossil fuels such as oil is that they cause air pollution. Therefore, as a way to significantly reduce or fundamentally solve such air pollution, a lot of researches on electric vehicles, hybrid vehicles, etc. have been conducted, and some have been commercialized and used. The field where research is concentrated in relation to the development of such an electric vehicle is an electric generator as a power source.

In this regard, research has recently been conducted on the use of lithium secondary batteries, which are frequently used as power sources for mobile devices, as power sources for electric vehicles. In particular, Li-ion polymer batteries (LPB) have the advantage of providing a free cell design and high energy and power density. In order to use a lithium secondary battery as an automobile power source, it is necessary to satisfy various requirements. One of them is to configure a battery with a high output large capacity power supply. As one of the ways to provide a high output capacity with a limited size and weight, a technology for configuring a single battery pack by connecting a plurality of unit cells in series and in parallel has been proposed.

However, when a lithium secondary battery is used as a power source of an electric vehicle that requires high power, a large amount of heat generation is a problem. In order to solve the large calorific value problem, a cooling system is added. In general, a large calorific value requires a powerful and large cooling system, which in turn increases the size and weight of the battery pack, lowers the power density, and complex structure. As required, it causes a decrease in the assembly processability.

The battery pack used in the electric vehicle provides a high power and a large capacity by connecting a plurality of unit cells in series to form a battery group and again connecting them in parallel to form a battery pack. In general, in series connection of unit cells, unit cells protruding from both ends of the positive electrode tab and the negative electrode tab are connected to each other so that the positive electrode tab and the negative electrode tab cross each other. As an example, FIG. 1 schematically shows a series connection of unit cells in a high power / large capacity battery pack of the prior art.

Referring to FIG. 1, the unit cell 10 is sealed by a case in which a positive electrode, a negative electrode, a separator, and an electrolyte are embedded therein, and a positive electrode tab 20 and a negative electrode tab 30 protrude from upper and lower portions thereof, respectively. It is. When the positive electrode tab 20 is positioned upward in the first unit cell 10, the adjacent second unit cell 11 is disposed such that the positive electrode tab 21 is positioned downward. These unit cells 10 and 11 are electrically connected to each other by the electrode lead 40 while the opposite electrodes are adjacent to each other. The third unit cell 12 is also connected in series with the second unit cell 11 while being arranged in such a manner. Adjacent to the first battery group consisting of a plurality of unit cells connected in a series manner as described above, a second battery group consisting of a plurality of unit cells connected in the same manner but not shown in FIG. Adjacent to the battery group is connected in parallel. As described above, in a state in which a plurality of battery groups are connected in parallel, the positive electrode tab 20 of the first unit cell 10 of each cell group is connected to the positive external terminal 50, and the negative electrode tab of the last unit cell 15 is connected. 33 is embedded in the housing 70 in a state of being connected to the cathode external terminal 60. Although the electrode tabs 20 and 30 are formed in the long axis direction of the unit cell 10 of FIG. 1, in some cases, a structure in which the electrode tabs face each other in the short axis direction is also developed.

In general, the positive electrode of a unit cell exhibits a higher calorific value than a negative electrode due to a high resistance positive electrode active material. The high calorific value of the positive electrode acts as a cause of deterioration of the battery itself when not properly resolved. However, in the general unit cell structure in which the two electrode tabs are positioned opposite both ends of the unit cell as shown in FIG. 1, it is confirmed that the calorific value of the positive electrode is not effectively eliminated.

Therefore, when manufacturing a high output, large capacity battery pack by connecting a plurality of unit cells, there is a high need for a structure that can more effectively eliminate the high calorific value of the positive electrode.

The present invention aims to solve the problems of the prior art as described above and the technical problems that have been requested from the past.

After extensive research and various experiments, the inventors of the present invention have a high output large capacity battery pack in which a plurality of unit cells are connected in series and in parallel. The positive and negative tabs protrude together at one end of each unit cell. When connected in series with adjacent unit cells, the temperature of the positive electrode tab is remarkably lowered as compared to the series connection structure of the conventional unit cell in which the positive electrode tab and the negative electrode tab face each other. And it was confirmed that the fact that it can be suppressed, and also in the case of the structure and the structure of the electrode tab and the electrode tab of the electrode tab, it was confirmed that this effect is further improved, and came to complete the present invention.

The battery pack according to the present invention for achieving the above object is a battery pack in which a plurality of unit cells are connected in series and in parallel so as to provide electricity with a high output large capacity, each unit cell is a positive electrode tab and a negative electrode The tabs protrude together at one end of the unit cell, and the electrode tabs of the first unit cell (a) are connected to the electrode tabs of the adjacent second unit cells (b) in series by an electrode lead. It consists of.

In the above, "a battery pack connected in series and parallel manners to provide electricity at a high output capacity", as described with reference to FIG. 1, a plurality of unit cells are connected in series to form one battery group. That is, a battery pack having a structure in which a plurality of battery groups having such a structure is connected in parallel to provide a high output and a large capacity. The number of unit cells in each battery group is not particularly limited, and may be, for example, 4 to 15. In addition, the number of battery groups included in the battery pack is also not particularly limited, and may be, for example, 2 to 10.                     

The unit cell is a secondary battery capable of continuous charging and discharging. Preferably, the unit cell is a rectangular battery or a pouch type battery that can be accumulated at high density in a battery pack.

The unit cell is embedded in a state in which the positive electrode, the negative electrode, the separator, and the electrolyte are sealed in the battery case, and the electrode assembly in which the microporous separator is interposed between the thin film of the positive electrode and the negative electrode and the electrode of the positive electrode / membrane / cathode Various structures are possible, such as a stacked assembly. The active material applied to the positive electrode and the negative electrode, respectively, is also not particularly limited. Preferably, the positive electrode active material is made of a high safety lithium manganese oxide, and the negative electrode active material is made of a carbon material. In particular, the preferred unit cell may be based on a lithium ion polymer secondary battery.

2 and 3 are schematic views showing a structure in which unit cells are connected in series in a battery pack according to an embodiment of the present invention. However, these drawings are intended to more easily represent the contents of the present invention, and the scope of the present invention is not limited thereto.

Referring to FIG. 2, the unit cell 100 has a structure in which the positive electrode tab 200 and the negative electrode tab 300 are formed together at one end thereof. The second unit cell 101 is adjacent to the same tab direction as the first unit cell 100, and the negative electrode tab 300 of the first unit cell 100 is the positive electrode tab 201 of the second unit cell 101. ) And the electrode lead 400 are connected to each other. The remaining structure and configuration of the battery pack is the same as in FIG.

Further details of the coupling structure between the electrode tab of the unit cell and the adjacent unit cell are shown in FIG. 3. Referring to FIG. 3, when the first unit cell 100 and the second unit cell 101 are connected in series, the negative electrode tab 300 and the second unit cell 101 of the first unit cell 100 are connected. The electrode lead 400 is coupled to the positive electrode tab 201 of FIG. In the same manner, the electrode lead 400 is coupled to the negative electrode tab 301 of the second unit cell 101 and the positive electrode tab 202 of the third unit cell 102.

According to the experiments of the present inventors, the temperature of the positive electrode tab 201 of the unit cell (for example, 101) in the tap configuration and the electrical connection method of FIG. 3, when charging and discharging with a current of 100 A, Compared with the positive electrode tab in a unit cell, it was surprisingly found to be about 3 degreeC low. This low temperature of the positive electrode tab means an improved temperature deviation of 10 to 23% relative to the positive electrode tab in the unit cell of FIG. 1, and the degradation of the unit cell according to the present invention by such temperature deviation can be suppressed. As such, the reason why the temperature of the positive electrode tab decreases cannot be explained precisely, but is probably due to the shorter length of the electrode lead compared to FIG. 1 when the high heat of the positive electrode tab is conducted to the negative electrode tab through the electrode lead. I guess.

Referring again to FIG. 3, it is particularly preferable that the distance d ₁ of the tabs 300 and 201 of the opposite electrodes between the two unit cells 100 and 101 is within 30% of the width L of the unit cell. . According to the inventors, it was confirmed that the temperature drop of the positive electrode tab was large when the distance d ₁ between the electrode tabs was approximately in the above range.

In addition, the distance d ₂ between the positive electrode tab 201 and the negative electrode tab 301 in one unit electrode 101 is particularly preferably within 15% of the battery width L. When the distance between the positive electrode and the negative electrode is too far, the resistance term for electronic conduction in the battery increases, which may adversely affect the performance of the battery. On the contrary, when the distance between the anode and the cathode is too close, it is not preferable because the battery temperature rises due to the local current flow.

The electrode leads 400 electrically connecting the tabs 202 and 301 of the electrodes opposite to each other may be made of various materials, and examples thereof include nickel, copper, lead, and nickel-aluminum alloy. The coupling method of the electrode lead 400 and the tabs 202 and 301 may also be various. For example, a coupling method such as welding, soldering, or coupling may be used. The material, width, and thickness of the electrode lead 400 are important for transferring the high calorific value of the positive electrode tab 202 to the negative electrode tab 301, and the width × thickness of the lead is preferably 30 × 0.1 to 70 ×. It can be determined in the range of 0.5 (mm). According to the experiment, it is possible to more effectively lower the high heat generation amount of the positive electrode tab when the width and thickness of the lead are within the above range.

The shape of the electrode lead may be Al and Ni coated Cu or the like having a suitable surface treatment for securing durability as a sheet form.

Hereinafter, the present invention will be described in detail by way of examples, but the scope of the present invention is not limited thereto.

Example 1                     

As a unit cell, six lithium ion polymer batteries (LG chemicals) were connected in series in the same manner as in FIG. 2 to form a battery group, and the two battery groups were connected again in parallel to manufacture a battery pack. In the structure of the battery pack, the distance between the opposite electrode tabs of adjacent unit cells was within 30% of the battery width, and the connection of the electrode tabs was performed by a thermal welding method using a beryllium copper bus bar.

The battery pack thus manufactured was repeatedly charged and discharged 30 times with a 30 to 40 A pulse cycle, and the temperature during discharge of ten randomly selected positive electrode tabs was measured. As a result, the temperature of the positive electrode tab in discharge conditions was in the range of 32-34 degreeC.

Comparative Example 1

The experiment was conducted in the same manner as in Example 1 except that the distance between the opposite electrode tabs of adjacent unit cells was greater than 30% and less than 60% of the unit cell width. As a result, the average temperature of the positive electrode tab was 38 ° C.

Comparative Example 2

The experiment was conducted in the same manner as in Example 1 except that the distance between the opposite electrode tabs of adjacent unit cells was set to 60% or more and less than 90% of the unit cell width. As a result, the average temperature of the positive electrode tab was 40 ° C.

As can be seen from the above results, in the battery packs according to the present invention (Example 1), the calorific value of the positive electrode tabs is about 5 to 7 ° C. in comparison with the positive electrode tabs of the battery packs of the prior art (Comparative Examples 2 and 3). It can be seen that low.

As described above, the high output large capacity battery pack according to the present invention can significantly reduce the heat generation amount of the positive electrode tab to suppress the deterioration of the unit cell can be produced a more excellent battery pack. Such a battery pack is particularly preferable as a power source of an electric vehicle and a hybrid vehicle.

Those skilled in the art to which the present invention pertains will be able to perform various applications and modifications within the scope of the present invention based on the above contents.

Claims (6)

In a battery pack in which a plurality of unit cells are connected in series and in parallel so as to provide electricity at a high output capacity, each unit cell has a positive electrode tab and a negative electrode tab protruding together at one end of the unit cell. A battery pack comprising a structure in which an electrode tab of one unit cell (a) is connected in series to an electrode tab of an adjacent second unit cell (b) by an electrode lead. The battery pack as claimed in claim 1, wherein the unit cell is a lithium ion polymer battery. The battery pack as claimed in claim 1, wherein a distance between the electrode tab of the first unit cell and the counter electrode tab of the second unit cell adjacent thereto is within 30% of the width of the unit cell. The battery pack as claimed in claim 1, wherein a distance between the positive electrode tab and the negative electrode cap in the unit electrode is within 15% of the battery width. The battery pack according to claim 1, wherein the electrode lead has a sheet structure as 30 × 0.1 to 70 × 0.5 (mm) (width × thickness). The battery pack as claimed in claim 1, wherein the battery pack is used as a power source of an electric vehicle or a hybrid vehicle.

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