HK1118130B - Structure of layering unit cells for high power lithium polymer battery - Google Patents

Description

Structure of unit cell of laminated high-energy lithium polymer battery

Technical Field

The present invention relates to a structure of a unit cell of a stacked high-energy lithium polymer battery.

More particularly, the present invention relates to a structure of stacking unit cells of a lithium polymer battery, in which electrode terminals are disposed on surfaces of the respective unit cells of the lithium polymer battery and are alternately stacked, so that the unit cells are connected in series only through a stacking operation without an additional connecting device.

Background

Generally, a secondary battery is chargeable and dischargeable, unlike a primary battery. Research on secondary batteries has made secondary batteries suitable for high-tech fields such as digital cameras, cellular phones, notebook computers, or hybrid cars. As examples of the secondary battery, there have been nickel-cadmium batteries, nickel-metal hydride batteries, nickel-hydrogen batteries, rechargeable lithium batteries, and other batteries. Among these batteries, a rechargeable lithium battery has an operating voltage of 3.6V or more, and is used as a power source for portable electronic products. In addition, connecting several rechargeable lithium batteries in series may be used for a hybrid vehicle. The rechargeable lithium battery has an operating voltage 3 times that of a nickel-cadmium battery or a nickel-metal hydride battery. In addition, the rechargeable lithium battery has high energy density per unit weight. For these reasons, the use of rechargeable lithium batteries is rapidly increasing.

The rechargeable lithium battery may be manufactured in various shapes, for example, a cylindrical shape or a prismatic shape, which may be used for the lithium ion battery. A lithium polymer battery, which has recently attracted considerable attention, can be manufactured in a flexible pouch type so that its shape can be variously changed. In addition, the lithium polymer battery is excellent in stability and light in weight, and thus has an advantage in that a small and lightweight portable electronic product can be realized.

Referring to fig. 1, a conventional pouch-type rechargeable lithium battery 10 includes a battery part 11 and a case 12. The case 12 provides a space 12a for accommodating the battery part 11 therein.

The battery part 11 is made by placing an anode plate, a separator, and a cathode plate in this order and winding them in one direction, or is made by stacking a plurality of anode plates, separators, and cathode plates. Each electrode plate of the battery part 11 is electrically connected to the anode terminal 13 or the cathode terminal 14.

One end of each of the anode terminal 13 and the cathode terminal 14 protrudes out of the sealing surface 12b of the case 12. The protruding ends of the anode terminal 13 and the cathode terminal 14 are connected to terminals of a protection circuit board, which are not shown in the drawing.

A sealing tape 15 is wound at the junction of the outer surface of each of the anode and cathode terminals 13 and 14 and the sealing surface 12b, thereby preventing a short circuit between the case 12 and the electrode terminals 13 and 14.

The case 12 is not a cylindrical or prismatic can-shaped structure made of thick gold material (thick gold material), but is a bag-type structure of which the middle layer is a metal foil, and attached to opposite sides of the metal foil are inner and outer layers made of insulating films. Thus, the pouch structure has excellent toughness so that it can be bent as needed. As described above, the case 12 has the space 12a for accommodating the battery part 11 therein, and has the sealing surface 12b on the surface thermally fused along the edge of the space 12 a.

Fig. 2 is an enlarged view taken along line 1-1 in fig. 1.

Referring to the drawings, the housing 12 comprises a composite membrane having an intermediate layer 12c, an inner layer 12d and an outer layer 12 e. The intermediate layer 12c is made of a metal foil, such as aluminum foil. The inner layer 12d and the outer layer 12e include insulating films attached to the inner and outer surfaces of the intermediate layer 12c to protect the intermediate layer 12 c.

The battery portion 11 has an anode plate 11a, a separator 11c and a cathode plate 11b arranged in this order, and is housed in a space 12a of the case 12. Anode terminal 13 and cathode terminal 14 extend from anode plate 11a and cathode plate 11b as shown in fig. 1. The distal ends of the electrode terminals 13 and 14 are exposed to the outside through the sealing surface 12b of the case 12. The sealing tape 15 is wound around the outer surface of each of the electrode terminals 13 and 14 in the sealing surface 12 b.

The battery part 11 of the pouch-type rechargeable lithium battery 10 constructed as described above is manufactured through the following process. First, the anode terminal 13 and the cathode terminal 14 are electrically connected to the anode plate 11a and the cathode plate 11 b. Next, the anode plate 11a, the separator 11c, and the cathode plate 11b are arranged in this order. In this state, they are wound in one direction, thereby making the battery portion 11.

The completed battery part 11 is housed in the case 12 having the space 12a by a drawing process. One end of each of the electrode terminals 13 and 14 is exposed to the outside of the case 12 during the mounting process. In this state, predetermined heat and pressure are applied to the sealing surface 12b of the case 12, thereby performing thermal fusion. Thereby completing the pouch-type rechargeable lithium battery 10. The completed pouch-type rechargeable lithium battery 10 is subjected to a series of molding processes including a charging operation, an aging operation, and a discharging operation, thereby detecting a defective battery and stabilizing the battery structure.

Korean patent application laid-open No. 2005-594 discloses a related art method for packaging pouch-type rechargeable lithium batteries. According to this document, the pouch-type rechargeable lithium battery applies the same positive potential to the metal layer of the case and the anode terminal, thereby damaging the case internal layer. Due to the destruction of the inner layer, a short circuit is caused when the cathode terminal and the metal layer of the case contact each other, so that an open circuit voltage difference is easily detected.

Meanwhile, when a high-energy lithium battery is required, as in a hybrid car, several tens or hundreds of pouch type batteries as shown in fig. 1 and 2 may be stacked and connected in series, thereby providing a high voltage.

Since the pouch type lithium polymer battery includes a fragile aluminum pouch that is easily bent or curved, the pouch must be protected by a strong case so as to be used for a long time. According to the related art, in order to connect the pouches in series, the anode terminal and the cathode terminal of each pouch are connected through a PCB (printed circuit board) having a circuit pattern. The attached bag is then placed in the housing.

However, the conventional method of obtaining a high-energy lithium battery by stacking lithium polymer pouches is problematic in that it is difficult to perfectly protect the fragile lithium polymer pouches. Also, a method of stacking a plurality of pouches and connecting the pouches to a PCB is imperfect, so that it is easily affected by the environment, such as external impact.

Therefore, a method is required to more firmly and reliably stack pouches constituting lithium batteries as high energy sources and reliably connect the pouches in series.

Disclosure of Invention

Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide a structure capable of firmly and stably laminating a plurality of lithium unit cells.

Another object of the present invention is to provide a stacking structure capable of simultaneously stacking and connecting a plurality of lithium unit cells without an additional connecting device.

Another object of the present invention is to provide a stacking structure capable of easily stacking a plurality of lithium unit cells without an additional supporting device.

In order to achieve the above object, the present invention provides a battery system including a first unit cell and a second unit cell, each unit cell having a pouch and an anode terminal and a cathode terminal connected to a surface of the pouch and oppositely bent in upward and downward directions. In this case, the cathode terminal of the second unit cell is directly connected to the anode terminal of the first unit cell.

As described above, the present invention provides a structure capable of firmly and reliably laminating a plurality of lithium unit cells.

Also, the present invention provides a stacking structure capable of simultaneously stacking and connecting a plurality of lithium unit cells without an additional connecting device.

In addition, the present invention provides a stacking structure capable of easily stacking a plurality of lithium unit cells without an additional supporting device.

Drawings

Fig. 1 illustrates a conventional pouch-type rechargeable lithium battery;

fig. 2 is an enlarged view of the conventional pouch-type rechargeable lithium battery of fig. 1 taken along line I-I;

fig. 3 is a perspective view of a lithium unit cell according to the present invention;

fig. 4 shows a structure in which two unit cells of fig. 3 are stacked;

fig. 5 is a perspective view illustrating a main frame for clamping a unit cell according to the present invention;

fig. 6 is a perspective view illustrating a cover frame for covering the unit cells according to the present invention;

fig. 7 shows a structure of a stacked unit cell according to the present invention; and

fig. 8 is a perspective view illustrating a stacked structure of a lithium battery system according to the present invention.

Detailed Description

Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

Fig. 3 is a perspective view of a lithium unit cell 31 according to the present invention;

according to the present invention, the lithium unit cell 31 includes a pouch 34 and a pair of anode and cathode terminals 32 and 33. The pouch 34 has a rechargeable lithium battery structure therein. An anode terminal 32 and a cathode terminal 33, each having a bracket shape, are provided on the surface of the pouch 34.

The pouch 34 may have the structure of a conventional pouch-type rechargeable lithium battery shown in fig. 2, i.e., a structure formed by stacking anode plates, cathode plates, and separators a plurality of times. Further, such bags are not rigid, but flexible, unlike typical metals or plastics.

The anode terminal 32 and the cathode terminal 33 are connected to an anode plate and a cathode plate (not shown) in the pouch 34. One end of the anode terminal 32 and one end of the cathode terminal 33 are bent in opposite directions with respect to the pouch 34.

Preferably, as shown in fig. 3, the connection parts 35 between the anode terminal 32 and the pouch 34 and between the cathode terminal 33 and the pouch 34 are stepped, and thus are easily connected to the electrode terminals of other unit cells.

Preferably, the anode terminal 32 may be made of aluminum, and the cathode terminal 33 may be made of nickel or copper.

Fig. 4 shows a state in which two unit cells 31a and 31b of fig. 3 are stacked.

The first unit cell 31a and the second unit cell 31b in fig. 4 have the same shape. The ends of the anode terminals of the first and second unit cells 31a and 31b are bent in opposite directions. Also, the ends of the cathode terminals of the first and second unit cells 31a and 31b are bent in opposite directions.

When one unit cell is stacked on another unit cell having the same shape, the other unit cell is turned upside down. That is, the unit cells are stacked as shown in fig. 4. The anode terminal and the cathode terminal are alternately connected to each other, thereby connecting the two unit cells in series.

That is, as shown in fig. 4, the end of the anode terminal 32a of the first unit cell 31a is bent downward, and the end of the cathode terminal 33a is bent upward. The end of the anode terminal 33b of the second unit cell 31b is bent downward and the end of the cathode terminal 32b is bent upward.

The anode terminal 32a of the first unit cell 31a is connected to the cathode terminal 32b of the second unit cell 31 b.

With this structure, the first unit cell 31a and the second unit cell 31b can be connected in series with each other only through the stacking operation without an additional connecting means, such as a PCB, unlike the related art. The contact resistance becomes very low.

Additional unit cells may be stacked on the stacked structure of fig. 4 as needed. Additional unit cells may be stacked by alternately connecting the anode terminals and the cathode terminals such that they are connected in series.

Fig. 5 is a perspective view of a main frame 41 for packaging a unit cell having the pouch and the electrode terminal of fig. 3 or a unit cell having other pouches and electrode terminals according to the present invention.

The main frame 41 includes a pouch support frame 47, a heat radiating portion 46, and a terminal support 42. The pouch support frame 47 supports the pouch of the unit cell. The heat radiating portion 46 is formed at a side of the pouch support frame 47 in the form of a bracket. The terminal support 42 is formed in the form of a wall at the side wall of the heat dissipation part 46 and supports the electrode terminals of the unit cells.

Preferably, the main frame 41 is made of an integral plastic member.

The pouch support frame 47 holds the pouch therein and serves to support the pouch by the outer surface of the pouch support frame 47. The heat radiating portion 46 functions to radiate heat generated in the pouch.

As shown in fig. 5, the pouch support frame 47 preferably has a predetermined depth to hold the pouch therein.

Preferably, a support lattice 43 is provided in the pouch support frame 47 for stably supporting the pouch clamped in the main frame 41.

The pouch support frame 47 may have frame locking parts 44a and 44b, and may be connected to other frames by screwing screws into the frame locking parts 44a and 44 b.

The terminal supporter 42 serves to support the anode and cathode terminals of the unit cells. Preferably, the terminal supporter may have terminal locking parts 45 so that the anode and cathode terminals may be fixed to the terminal locking parts 45 using screws.

Further, the terminal support 42 has frame connecting portions 48a and 48b at opposite ends thereof for connection to frame connecting portions of another frame when the frames are connected to each other. Preferably, the main frame 41 may have another frame locking portion 44c to be locked to another frame.

Fig. 6 is a perspective view of a cover frame 51 for being stacked on the main frame 41 in fig. 5 and connected to the main frame 41 to cover the unit cells.

The cover frame 51 includes a pouch support frame 57, a heat radiating portion 56, and a terminal support 52, like the main frame 41. The pouch support frame 57 supports the pouch of the unit cell. The heat radiating portion 56 is formed at the side of the pouch support frame 57 in a support form. The terminal support 52 is formed in the form of a wall at the side wall of the heat dissipation part 56 and supports the electrode terminals of the unit cells.

Preferably, the cover frame 51 is made of a unitary plastic piece.

The main frame 41 and the cover frame 51 form a battery case. The cover frame 51 is stacked on the main frame 41 and connected to the main frame 41. Preferably, the cover frame 51 serves as a cover covering the main frame 41. In this case, the frame connecting portions 48a and 48b of the main frame 41 are connected to the corresponding frame connecting portions 58a and 58b of the cover frame 51.

That is, the unit cells are placed in the main frame 41, and then the cover frame 51 is covered on the main frame 41, thereby stably packing the unit cells.

Fig. 7 shows such a stacked structure. The main frame 41 and the cover frame 51 are stacked, and the unit cell of fig. 3 is inserted into the main frame 41 and the cover frame 51. In this case, the unit cells are stacked such that the anode terminals and the cathode terminals are cross-connected to each other in series.

This stacking structure stably connects the main frame 41 and the cover frame 51 to each other without an additional supporting or connecting means. A flexible battery cell may be inserted into the structure.

Also, screws or bolts may be screwed into the frame locking parts 44a, 44b, 44c, 54a, 54b, and 54c on the pouch support frames 47 and 57 and the terminal supports 42 and 52 as needed, thereby increasing stability. Also, the electrode terminals may be fixed to the terminal locking parts 45 and 55 on the terminal supports 42 and 52 with screws or bolts.

The main frame, the unit cells, and the cover frame constitute one unit. The other unit cells are inserted into the stacked unit. Thus, a plurality of unit cells, for example, 100 unit cells, are connected in series.

Fig. 8 is a perspective view of a stacked structure of a lithium battery system including a plurality of main frames and a cover frame, and a unit cell interposed between the main frames and the cover frame.

Industrial applicability

As described above, the present invention can firmly and stably stack a plurality of lithium unit cells.

Furthermore, according to the present invention, it is possible to simultaneously stack and connect a plurality of lithium unit cells without an additional connection device.

Also, according to the present invention, a plurality of lithium unit cells can be easily stacked without an additional supporting device.

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.

Claims (3)

1. A battery system, comprising:

a first unit cell and a second unit cell, each having a pouch having a rectangular plate shape and an anode terminal and a cathode terminal extending outward from sides of the pouch and bent toward a first direction and a second direction opposite to the first direction, respectively, wherein

The cathode terminal of the second unit cell is directly connected to the anode terminal of the first unit cell.

2. The battery system of claim 1, wherein each of the anode and cathode terminals of the first and second cells extend outwardly from a side of the pouch in the form of a plate.

3. The battery system of claim 1, further comprising:

at least one unit cell having the same shape as the first and second unit cells, additionally stacked on the first and second unit cells, and having an anode terminal and a cathode terminal, the cathode terminal of the at least one unit cell being directly connected to the anode terminal of the first or second unit cell, and the anode terminal of the at least one unit cell being directly connected to the cathode terminal of the first or second unit cell.