KR100389968B1 - Lithium ion secondary battery - Google Patents

Abstract

Disclosed is a thin light area lithium ion secondary battery capable of preventing leakage of an electrolyte solution and improving energy storage density by securing a sealing property of a can and a cap. The thin light-area lithium ion secondary battery of the present invention is characterized in that the flange is applied to the can, and the upper part of the can including the flange is inserted into the cap to assemble and weld. According to the present invention, the welding area required for welding the can and the cap can be secured to prevent the electrolyte from leaking, and a metal container having a wide opening and a thickness of 0.3 mm or less can be used as a battery can, thereby dramatically reducing the energy storage density. Not only can it be increased, but the can and cap are assembled by inserting method, which eliminates the need for a separate jig when welding the cap and cap, thereby improving productivity and lowering the production cost. The battery of the shape can be easily made, and by installing the protective circuit box and the PTC box by utilizing the outer space formed by the shape of the can, the energy storage density per volume of the battery soft pack can be significantly improved.

Description

Lithium ion secondary battery

The present invention relates to a thin light area lithium ion secondary battery, and in particular, to secure the sealing property of a wide area can and cap having a wide opening, preventing leakage of electrolyte solution, improving energy storage density, and making batteries of various shapes. The present invention relates to a lithium ion secondary battery having a thin light area.

As the market for portable electronic devices such as mobile phones and notebook computers expands and diversifies, the demand for rechargeable rechargeable batteries is increasing. Miniaturization, light weight, high performance, and multifunctionality of portable electronic devices require continuous improvement of energy storage density of secondary batteries used as power sources.

Accordingly, as a result of many years of research to satisfy this problem, a lithium ion secondary battery using a cathode material capable of reversible insertion and release of lithium and a reversible insertion and release of lithium have emerged. The lithium ion secondary battery has a relatively larger unit weight, energy density per volume, and charge / discharge life than conventional aqueous solutions such as nickel-cadmium and nickel-hydrogen, thus rapidly replacing the existing battery as a new energy source for portable electronic devices. Doing.

On the other hand, mobile phones and personal digital assistants are increasing in size due to an increase in the amount of processing and display information. In addition, communication functions are added and energy consumption is rapidly increasing. Therefore, in the case of adopting a general 6 mm or less thin lithium ion secondary battery, it is difficult to obtain sufficient driving time. Therefore, it is necessary to connect two or more batteries or employ a thicker battery. The outline of the lithium ion secondary battery is largely composed of a can into which an electrolyte and the like are inserted, and a cap forming a sealed container together with the can. However, as the width of the lithium ion secondary battery becomes wider and the capacity thereof increases, the electrolyte leaks at the contact portion between the can and the cap due to an increase in the internal pressure due to the expansion of the electrode and the generation of gas, which occur naturally during the use of the lithium ion secondary battery. Situations often arise. If the electrolyte leaks in this way, it not only adversely affects the performance of the battery itself, but more seriously, it may contaminate the electronic circuit of the electronic device in which the battery is being used to shorten the life of the expensive electronic device. do.

1A and 1B are schematic diagrams for explaining a conventional lithium ion secondary battery.

In order to prevent the problems caused by the leakage of the electrolyte as described above, the conventional lithium ion prismatic battery is focused on minimizing the sealing area of the battery can and the cap, the battery can is narrow and deeply shaped metal container I'm using. By the way, when the surface area of the deep dug increases compared to the area of the container opening, the stretching of the metal plate should be made that much. Therefore, it is not suitable to manufacture a thin light-area battery because a rupture or deformation of the container wall at the edge of the container occurs, there is a limitation in producing a battery of various shapes because the container is deeply dug.

Recently, a lithium ion square battery having a wall thickness of about 0.2 mm has been introduced, but in this case, the exterior materials are limited to aluminum having high elongation. The high elongation metal is easy for deep drawing, but has a limitation of high defect rate in laser welding used for sealing because it is easily deformed by internal pressure of the battery and has high thermal conductivity. In addition, the multi-step molding raises the manufacturing cost of the metal cladding material due to the difficulty of the process, and has a big limitation in the selection of the cladding metal material and the change of the thickness.

On the other hand, lithium ion secondary batteries have been manufactured by laser welding after fitting the battery cap to the battery can in order to secure the welding area of the battery can and the battery cap with an external terminal and to increase productivity by mass production.

Referring to FIG. 1A, in the conventional fitting type lithium ion secondary battery, the cap has to be manufactured in two stages to fit the battery cap 21 to the can, and thus, the thickness increase of the battery cap 21 is essential. When the metal can 11 and the cap 21 having a wide opening and thin opening are welded and sealed, it is necessary to increase the thickness of the battery cap 21 to ensure the quality of the sealing. If the thickness of the battery cap 21 is increased for the above reason, the loss of energy density per volume of the battery becomes very large. Therefore, it is not suitable to use a fitting method to manufacture a thin light area battery. In addition, when the protective circuit box 30 and the PTC box 40 are installed on the outside in the state in which the can 11 and the cap 21 are assembled as shown in FIG. 1A, loss of energy density per volume is lost. It gets bigger. Accordingly, attempts have been made to insert and weld an electrode body into a metal can having a wide opening and thin shape, and then place and weld a metal cap having a wide plate shape in one stage.

Referring to FIG. 1B, in order to secure a welding area required for welding when the battery cap 22 having a wide plate shape having a thickness of the same stage as that of the battery can 12 that is not a two-stage shape of the fitting type is used. The thickness of the 12 and the battery cap 22 must be increased. Therefore, since the maximum available welding length of the metal container is the same as the thickness of the metal container, a proper sealing property cannot be secured in a metal container having a thickness of 0.3 mm or less, and thus there is a disadvantage in that the yield of the production process is low.

In addition, when the battery cap 22 having a wide plate-like shape having a thickness of one stage that is the same as the battery can 12 that is not a two-stage shape of the fitting shape is used, the battery can 12 and the battery cap ( There is a problem in that the joint position of 22) must be exactly matched. This requires high-precision tolerance management, which increases the production cost. In addition, expensive automatic jig is required in the welding process, and the production speed is greatly reduced due to the process time required for fixing the position. Will be raised.

Therefore, the technical problem to be achieved by the present invention is to introduce a flange into the battery can to make the battery can and cap to a thinner thickness than conventional to improve the energy storage density, adjust the protrusion length of the flange to increase the efficiency of the sealing, The present invention provides a lithium ion secondary battery capable of improving productivity.

Another object of the present invention is to provide a lithium ion secondary battery that can maximize the space outside the battery by providing a protective circuit box and a PTC box in the outer space formed by the shape of the can.

1A and 1B are perspective views illustrating a conventional lithium ion secondary battery;

2 to 5 are perspective views for explaining a lithium ion secondary battery according to the present invention.

Lithium-ion secondary battery of the present invention for achieving the above technical problem: a lower portion, an open upper portion, and a side wall connecting the lower portion and the upper portion of each of the first and second regions are formed to communicate with each other ; The first region having a lower portion sealed to allow the electrode plate and the electrolyte to be interpolated; The predetermined area is closed and protrudes outwardly from the sidewall of the first area, and the remaining predetermined area is formed in the lower part of the open shape so that the space formed by the first area and the space formed by the second area communicate with each other. A can formed of a flange provided at an upper end of the second region to protrude outside the sidewalls of the second region, and the second region having a cross-sectional area larger than that of the first region;

A closed container having a closed upper part and sidewalls forming a circumference to surround the flange, and assembled with the can so that the inner side of the sidewalls and the outer side of the flange face each other. A cap to form;

One end is connected to the electrode plate and the other end is characterized by having an electrode terminal exposed to the outside of the can.

In this case, a lower portion of the second region is formed such that a predetermined region protrudes 2 to 10 mm from the side wall of the first region, and the flange protrudes from 0.2 to 2 mm from the side wall of the second region. The perimeter of the side wall of the side wall is characterized in that the gap between the inner side of the side wall and the outer side of the flange when the can and the cap is located so that the gap between the inner side of the side wall and the outer side of the flange is less than 1mm, The height of the side wall of the second region may be 0.5 to 3 mm, and the height of the side wall of the cap may be 0.5 to 5 mm.

Further, the other end of the electrode terminal may be exposed to the outside of the can through the closed lower portion of the second region of the can. At this time, it is preferable that the protective circuit box in which the circuit connected to the electrode terminal is embedded is located in a space formed by the outer side of the side wall of the first region and the outer side of the lower portion of the second region. In addition, a PTC box including a PTC element connected to the electrode terminal may be positioned in a space formed by an outer side of the side wall of the first region and an outer side of the lower portion of the second region. It is preferably installed on the side wall of the first region so as to be disposed outside or below the bottom of the second region of the can, or located below the flange.

Further, the flange of the can and the side wall or the upper portion of the cap may be welded to form the sealed container.

Hereinafter, with reference to the accompanying drawings will be described a preferred embodiment of the present invention.

2 is a perspective view of a can according to the present invention, reference A is a cross-sectional view taken along line aa 'of FIG. 2, and FIG. 3 is a perspective view of a cap according to the present invention, reference B is taken along line bb' of FIG. 3. 4 is a perspective view showing the assembled shape of the can according to FIG. 2 and the cap according to FIG. 3, and reference numeral C is a cross-sectional view taken along line cc ′ of FIG. 4. FIG. 5 is a perspective view showing a shape of a protective circuit box and a PTC box installed in the assembly of the can and cap according to FIG. 4, wherein D is a cross-sectional view taken along the line dd ′ of FIG. 5, and E is an ee ′ of FIG. 5. Sectional view along the line.

Referring to FIG. 2, the cans 100 each include an independent space and include a first region 110 and a second region 120 communicating with each other. The cross sectional area of the second region 120 is greater than the cross sectional area of the first region 110.

The first region 110 includes an open top 111, a closed bottom 112, and sidewalls 113 connecting the top 111 and the bottom 112 to form a space.

The second region 120 includes a lower portion 122, an open upper portion 121, sidewalls 123 connecting the upper portion 121 and the lower portion 122 to form a space, and protrude outside the sidewalls. It consists of a flange 124 provided on the top. In this case, unlike the lower part 112 of the first area 110, the lower part 122 of the second area 120 is closed in the predetermined area 112 ′ from the sidewall 113 of the first area 110. Protrudes outward, and the remaining predetermined region 122 ″ is opened to be connected to the upper portion 111 of the first region 110. Therefore, the upper region 111 and the second region of the first region 110 ( The interior spaces formed by the first region 110 and the second region 120 communicate with each other through the lower portion 122 of the 120. Meanwhile, the spaces in the lower portion 122 of the second region 120 are closed. The protruding regions 122 'may be present only with respect to the one side wall 113' of the first region 110. In this case, the side walls 123 of the second region 120 except for the one side wall 123 are provided. The remaining sidewalls are positioned on the extension of the other sidewalls 113 ″ of the first region 110.

Although not shown, an electrode plate and an electrolyte are inserted into the first region 110 of the can 100, and the other end of the electrode terminal connected to one end of the electrode plate is the second region 120 of the can 100. Is exposed to the outside through the protruding and hermetic lower portion 122 '.

The flange 124 of the can 100 is assembled with a cap, which will be described later, to form a sealed container.

Meanwhile, the protruding length of the hermetically sealed and protruding region 112 'in the lower portion 122 of the second region 120 may be 2 to 10 mm from one side wall 113' of the first region 110. This is a protective circuit box described later in the space created by the outer side of the side wall 113 'of the first region 110 of the can 100 and the outer side of the sealed and protruding lower portion 122' of the second region 120. Alternatively, when installing a PTC box, the volume of the protective circuit box or the PTC box and its installation workability are considered. However, there is a problem that the volume of the can is increased if the protrusion length is longer.

The flange 124 may increase the efficiency of sealing by adjusting its protruding length, and it is preferable that the flange 124 protrudes 0.2 to 2 mm from the side wall of the second region 120. This takes into consideration workability in the joining operation of the can and the cap to be described later.

Referring to FIG. 3, the cap 200 is formed of a closed upper portion 210 and sidewalls 230 forming a circumference to surround the flange 124 of the can 100 of FIG. 2. It is a shape with an open space. At this time, the inside of the side walls 230 of the cap 200 and the outside of the flange 124 of the can 100 face each other, the top of the flange 124 of the can 100 and the top 210 of the cap 200. When the can 100 and the cap 200 are assembled such that the inner predetermined area of the cap 200 comes into contact with the cap 200, the gap between the inside of the side wall 230 of the cap 200 and the outside of the flange 124 is 1 mm or less. It is preferable to form the perimeters of the sidewalls 230 of. This is because if the gap is too large, the sealing property may be lowered even when the can 100 and the cap 200 are joined by welding or the like.

Then, when the height of the side wall 123 of the second region 120 of the can 100 is 0.5 to 3 mm, the height of the side walls 230 of the cap 200 may be 0.5 to 5 mm. This can be done for the purpose of sealing, although it is possible for the cap 200 to wrap at least the first and second regions 110 and 120 of the can 100 when the can 100 and the cap 200 are assembled. If the height of the 200 is too high, this is because the workability in the joining operation of the can 100 and the cap 200 to be described later is reduced.

4, the inner sidewalls 230 of the cap 200 and the outer side of the flange 124 of the can 100 face each other, and the top of the flange 124 of the can 100 and the cap 200 of the cap 200 face each other. The can 100 and the cap 200 are assembled so that the predetermined area inside the upper portion 210 abuts. One sealed container is formed by joining the sidewall 230 and top of the cap 200 and the flange 124 of the can 100 using laser welding or resistance welding.

As such, the upper portion of the can including the flange is inserted into the cap and the flange and the cap are welded to secure a welding area necessary for welding the can and the cap, and the welding can be performed without a separate jig.

On the other hand, as a safety device, a lithium ion secondary battery generally employs a PTC element which cuts off a current when the temperature rises or a protection circuit having a function of preventing overcharge and overdischarge.

Referring to FIG. 5, an electrode terminal is electrically connected to a space formed by an outer side of one side wall 113 ′ of the first region of the can 100 and an outer side of the protruding and closed lower portion 122 ′ of the second region. The protective circuit box 410 is installed. At this time, the protective circuit box 410 is firmly installed on one side wall 113 ′ of the first region of the can 100 or a lower portion 122 ′ of the second region of the can 100.

In the space created by the outer side of the other side wall 113 ″ of the first region of the can 100 and the lower portion of the flange 124, a PTC box 420 electrically connected to the electrode terminal is provided. The PTC 420 box is firmly installed on the outside of the sidewall 113 "of the first region of the can 100. As such, the protective circuit box 410 is installed in the space generated by the outer side of the side wall 113 'of the first region of the can 100 and the outer side of the protruding and closed lower portion 122' of the second region. Of the battery soft pack manufactured by attaching a PTC box 420 in a space formed by an outer side of the other side wall 113 ″ of the first region of the can 100 and a lower portion of the flange 124. At the same time reducing the volume, the energy storage density per volume as a battery soft pack is improved.

On the other hand, the electrolyte injection hole 600 is provided in the lower portion 122 ′ of the second region of the can 100 so as to inject the electrolyte solution through the protruding and closed lower portion 122 ′ of the second region of the can 100. Then, the other end 500 of the electrode terminal to which the electrode plate is connected at one end thereof penetrates through the protruding and hermetic region 122 ′ below the second region of the can 100 so as to form a portion of the second region of the can 100. It is provided in the outer wall of the lower part 122 '. At this time, the predetermined region of the lower portion of the second region of the can 100 through which the electrode terminal 500 penetrates is very tightly sealed so that the electrolyte is not leaked, and the electrolyte injection hole 600 is also very strong after injecting the electrolyte solution. To be sealed.

Example 1

Using a can and cap of the present invention made of a metal plate having a thickness of 0.15 mm, a lithium ion secondary battery was manufactured in a square shape having a thickness of 4.2 mm, a short diameter of 34 mm, and a long diameter of 54 mm.

At this time, the protruding length of the flange of the can is 0.5mm so as to have a sufficient area for welding, and the gap between the outside of the can of the flange and the inner side of the side wall of the cap is 0.1mm, and then assembled as shown in FIG. The flange and the top and sidewalls of the cap were joined by laser welding. 4, the protective circuit box and the PTC box were firmly attached to the outer surface of the can.

The energy storage density per volume as a soft pack state of the lithium ion secondary battery manufactured as described above was 420 Wh / l.

[Example of lithium ion secondary battery according to Figure 1a]

A lithium ion secondary battery using a can and a cap having a shape according to FIG. 1A as a square having a thickness of 4.2 mm, a short diameter of 34 mm, and a long diameter of 50 mm was prepared. At this time, a 0.3 mm thick metal plate was used as a can, and a 0.8 mm thick metal plate was used as a cap. The prepared can and cap were assembled by laser welding as shown in Fig. 1A (3), and the protective circuit box and the PTC box were firmly attached to the outer wall of the assembly as shown in Fig. 1A (4).

At this time, the energy storage density per volume as a soft pack state of the lithium ion secondary battery was 286 Wh / l.

[Example of lithium ion secondary battery according to Figure 1b]

A lithium ion secondary battery using a can and a cap having a shape according to FIG. 1B as a square having a thickness of 4.2 mm, a short diameter of 34 mm, and a long diameter of 50 mm was prepared. At this time, both the can and the cap were prepared in one stage using a 0.3 mm thick metal plate. The prepared cans and caps were assembled as shown in FIG.

Comparative Example 1

Comparing the battery of Example 1 according to the present invention and [Example of the lithium ion secondary battery according to FIG. 1A], it can be seen that the case of the present invention has a large energy storage density per unit volume. Therefore, when the lithium ion secondary battery according to the present invention is manufactured to have the same energy storage density as that of the example of the lithium ion secondary battery according to FIG. 1A, the battery of the example of the lithium ion secondary battery according to FIG. 1A. The thickness of the battery can be made thinner. As described above, the battery having various shapes can be easily formed by making the molding depth of the container shallower.

Comparative Example 2

The battery of the present invention according to Example 1 described above and the lithium ion secondary battery prepared according to FIGS. 1A and 1B were stored and stored for 5 days in a 4.2 V state of charge, respectively. In addition, a hole was formed in the center of each cell and stored for 1 hour under the application of 5 atmospheres of air.

Under such conditions, the battery according to [Example of the lithium ion secondary battery according to FIG. 1B] has a small amount of electrolyte flowing through the junction surface and the voltage has also been reduced to 3.97 V. [Example of the lithium ion secondary battery according to FIG. 1A] The battery according to the present invention and the battery of the present invention were maintained at 4.12V and 4.13V voltage without leakage.

In addition, the battery according to [Example of the lithium ion secondary battery according to FIG. 1B] has a productivity loss of more than three times compared to 10 minutes of the battery of the present invention with a total work time of 30 minutes for welding. In addition, a jig having a complicated shape without interference with a separate laser welder for a welding process was required, whereas the battery of the present invention only required a process of inserting a can into a lower portion of a cap, and thus, a separate jig was not required.

According to the lithium ion secondary battery of the present invention as described above, by applying a flange to the can, inserting the upper portion of the can including the flange into the cap and assembling to secure a welding area necessary for welding the can and the cap, the electrolyte is leaked. The metal container can be used as a battery can with a wide opening and a thin opening, and the energy storage density can be dramatically increased by reducing the thickness of the metal container to 0.3 mm or less.

In addition, since the can and the cap are assembled by the inserting method, a separate jig is not required when the cap and the cap are welded, thereby improving productivity and lowering the production cost.

Furthermore, the battery of various shapes can be easily made by making the shaping | molding depth of a container shallower than before.

Furthermore, by installing the protective circuit box and the PTC box by utilizing the outer space formed by the shape of the can, the energy storage density per volume of the battery soft pack can be significantly improved.

The present invention is not limited only to the above embodiments, and it is apparent that many modifications are possible by those skilled in the art within the technical spirit of the present invention.

Claims (8)

A lower portion, an open upper portion, and first and second regions communicating with each other while forming independent spaces, respectively, as sidewalls connecting the lower portion and the upper portion thereof; The first region having a lower portion sealed to allow the electrode plate and the electrolyte to be interpolated; The predetermined area is closed and protrudes outwardly from the sidewall of the first area, and the remaining predetermined area is formed in the lower part of the open shape so that the space formed by the first area and the space formed by the second area communicate with each other. A can formed of a flange provided at an upper end of the second region so as to protrude outside the sidewalls of the second region, and the second region having a cross sectional area larger than the cross sectional area of the first region; A closed container having a closed upper part and sidewalls forming a circumference to surround the flange, and assembled with the can so that the inner side of the sidewalls and the outer side of the flange face each other. A cap to form; One end is connected to the electrode plate and the other end has a lithium ion secondary battery having an electrode terminal exposed to the outside of the can. The lower portion of the second region is formed such that a predetermined region protrudes 2 to 10 mm from the side wall of the first region, and the flange protrudes 0.2 to 2 mm from the side wall of the second region. Lithium-ion secondary battery. The circumference of the side wall of the cap, wherein the gap between the inner side of the side wall and the outer side of the flange is less than 1mm when the can and the cap are positioned so that the inner side of the side walls and the outer side of the flange face each other. Lithium ion secondary battery characterized in that it is formed to be. The lithium ion secondary battery of claim 1, wherein the height of the sidewall of the second region is 0.5 to 3 mm, and the height of the sidewall of the cap is 0.5 to 5 mm. The lithium ion secondary battery of claim 1, wherein the other end of the electrode terminal is exposed to the outside of the can through a closed lower portion of the second region of the can. The protective circuit box according to claim 1 or 5, wherein a protective circuit box in which a circuit connected to the electrode terminal is embedded is provided so as to be positioned in a space formed by an outer side of the side wall of the first region and an outer side of a lower portion of the second region. Lithium-ion secondary battery, characterized in that. The PTC box according to claim 1 or 5, wherein a PTC box having a PTC element connected to the electrode terminal is embedded in a space formed by an outer side of a side wall of the first region and an outer side of a lower portion of the second region. Lithium ion secondary battery, characterized in that it is provided on the outer side of the side wall of the first region of the can or the outer side of the lower portion of the second region of the can, or on the side wall of the first region to be located below the flange. The lithium ion secondary battery of claim 1, wherein the flange of the can is welded to a side wall or an upper portion of the cap to form the sealed container.