KR20170093369A - Degassing Device for Battery Cell Using Adjustable Valve and Degassing Method Using the Same - Google Patents

Abstract

As a device for removing gas generated in charging and discharging processes for battery activation in a process of manufacturing a battery cell embedded in a pouch type case in which an electrode assembly is embedded with an electrolyte, the present invention provides a degassing device of a battery cell which includes a chamber where the battery cell being sealed from the outside is located inside, a decompression unit for evacuating the air in the battery cell for changing the inside of the battery cell into a vacuum state, a valve which is located between the battery cell and the decompression unit and controls the vacuum state inside the chamber by a set opening degree and a control unit for controlling the opening degree of the valve for controlling the pressure inside the battery cell based on stepwise decompression. Accordingly, the present invention can prevent a defect rate of the battery cell from being increased.

Description

[0001] The present invention relates to a degassing apparatus for a battery cell using an adjustable valve and a degassing method using the same. [0002]

The present invention relates to a degassing apparatus for a battery cell using an adjustable valve and a degassing method using the same.

As technology development and demand for mobile devices have increased, the demand for batteries as energy sources has been rapidly increasing, and a lot of researches have been conducted on batteries that can meet various demands therefrom.

Typically, in terms of the shape of a battery, there is a high demand for a prismatic secondary battery and a pouch-type secondary battery which can be applied to products such as mobile phones with a small thickness, and has advantages such as high energy density, discharge voltage, There is a high demand for lithium secondary batteries such as lithium ion batteries and lithium ion polymer batteries.

Recently, an electrode assembly in which a porous separator is interposed between a positive electrode and a negative electrode each coated with an active material on an electrode collector is impregnated with a non-aqueous electrolyte containing a lithium salt, Pouch-shaped cells are attracting much attention due to their low manufacturing cost, small weight, easy shape deformation, and their usage is gradually increasing

In such a pouch-type battery, swelling may occur due to gas generated inside the battery case during charging and discharging for activating the battery.

Such a swelling phenomenon may cause a high pressure in the sealed battery case, further accelerate the decomposition of the electrolyte, and may cause explosion of the battery cell. Therefore, a process for discharging gas inside the battery case is performed by forming a through hole for gas discharge in a part of the pouch-shaped battery case. At this time, the battery cell is closed to discharge the gas, and the valve connected to the battery cell is adjusted to decompress the inside of the battery cell. However, since the valve is manually adjusted, there is a difference in vacuum reaching time for each chamber, and there is a problem that a large amount of electrolyte solution in the battery case is discharged due to a sudden drop in pressure.

Accordingly, there is a great need for a technology for controlling the vacuum arrival times of the target chambers equally to reduce the deviation of the gas discharge of the battery cells, the deviation of the discharge amount of the electrolyte, and the drop of the pressure.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems of the prior art and the technical problems required from the past.

The inventors of the present application have conducted intensive research and various experiments and have used a battery cell degassing apparatus including a valve capable of gradually regulating a vacuum state inside a chamber for degassing a battery cell as described later The present invention has been accomplished based on the discovery that it is possible to solve the problem that the variation in the amount of electrolyte discharge between the battery cells becomes large by reducing the pressure inside the sealed battery cell and increasing the vacuum reaching time.

To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described herein, there is provided an apparatus for removing a gas generated during charging and discharging for activating a battery in a battery cell having an electrode assembly, A decompression unit for sucking air in the battery cell to make the interior of the battery cell into a vacuum state, a vacuum chamber disposed between the battery cell and the decompression unit, And a control unit for controlling the amount of opening of the valve to regulate the pressure inside the battery cell based on the stepwise depressurization.

During the activation process of the battery cell, a gas is generated inside the battery cell due to side reaction with the electrolyte, resulting in a swelling phenomenon. If the internal pressure of the battery cell increases to a certain level or higher, the battery cell may be detonated. In order to prevent such a phenomenon, the gas inside the battery cell is removed to reduce the pressure It is necessary to perform a degassing process.

In order to degas the gas inside the battery cell, conventionally, since the valve connecting the battery cell and the pressure-reducing section is manually adjusted, it has been difficult to set the opening amount to increase stepwise. As a result, in the initial stage of opening the valve, the pressure inside the battery cell is rapidly lowered, so that there is a problem that the amount of the electrolyte discharged to each battery cell varies.

However, the battery cell degassing apparatus of the present invention can control the amount of opening of the valve for controlling the pressure inside the chamber, and it is possible to solve the problem due to the increase in the amount of opening of the valve, have.

Since the control unit can be set and controlled in a digital manner, it is possible to control not only the opening amount but also the holding time for each step as described below.

In one specific example, the vacuum state inside the battery cell can be sequentially depressurized by the gradual depressurization of the control unit.

Specifically, in order to sequentially depressurize the battery cells, a vacuum pad is attached to a gas outlet formed in a part of the sealing part of the battery cell, and the other end of the vacuum tube connected to the valve is connected to the vacuum pad. Since the connection between the valve and the pressure reducing portion is also performed using a vacuum tube, the pressure of the battery cell is reduced through the opening and closing of the valve according to the opening amount set in the control portion during operation of the pressure reducing portion.

At this time, since the amount of opening of the valve can be set by dividing into two or more steps, the pressure decreasing time inside the chamber can be increased by gradually increasing the opening amount of the valve.

When the decompression time in the battery cell is increased as described above, it is possible to reduce the deviation of the pressure decrease which is different for each battery cell. Therefore, it is possible to solve the problem that the discharge amount of the electrolyte varies, Can be manufactured.

For example, the stepwise depressurization may be a decompression divided into 2 to 10 steps, and in detail, it may be decompression divided into 3 to 6 steps.

If the stepwise depressurization is smaller than the second stage, it is difficult to solve the problem caused by the sudden pressure drop. If the stepwise depressurization is smaller than the 10 stages, the degassing process may be prolonged and the efficiency of the manufacturing process may deteriorate.

In one specific example, the valve may be set in a range of 0% to 100% in consideration of prevention of sudden drop in pressure and time taken for degassing, etc., and the inside of the battery cell is evacuated to perform a degassing process It is preferable to set the opening amount only in an increasing direction, rather than being set so as to repeat the increase and decrease. Therefore, the valve can be operated so that the opening amount increases stepwise for the gradual depressurization of the pressure inside the chamber.

In order to increase the vacuum state reaching time, the controller may set the holding time of the corresponding pressure in each step. The holding time of the corresponding pressure in each step may be set differently for each step, Can be set the same.

Generally, the vacuum state means a state in which the pressure is lower than -90 kPa when the pressure before the pressure decrease is 0 kpa, and the vacuum reaching time, which is the time required for the internal pressure of the battery cell to reach the predetermined vacuum state, May range from 1 second to 10 seconds, and in particular may range from 2 seconds to 6 seconds.

If the vacuum reaching time is shorter than 1 second, it is difficult to solve the problem of sudden pressure drop, and if it is longer than 10 seconds, the degassing process is delayed. However, considering that the retention time for each step is set, the vacuum reaching time may become longer as the number of decompression steps increases.

Further, in order to perform a stable degassing process, it is preferable to maintain a vacuum state after reaching a vacuum, and the predetermined vacuum state can be maintained for 3 to 30 seconds, more specifically, for 5 to 20 seconds .

If the holding time of the vacuum state is shorter than 3 seconds, gas discharge in the battery cell may not be completely performed. If it is longer than 30 seconds, the time required for the degassing process becomes longer, , The electrolyte is excessively discharged and the performance of the battery cell may be deteriorated.

In one specific example, the stepwise depressurization is divided into four steps and can be increased stepwise until the opening amount of the initial 0% reaches 100%. In the first step, the opening amount of 25% The opening amount can be set to 30% in the second stage, to 40% in the third stage, and to 100% in the fourth stage.

However, the number of the depressurization steps may be reduced or increased in consideration of the size of the battery cell and the time of arrival of the vacuum, and the size of the opening amount may be appropriately set according to the number of depressurization steps.

The battery cell degassing apparatus may include two or more chambers, and the controller may set the vacuum cells of all the chambers to have the same vacuum reaching time.

As described above, by setting the vacuum reaching time or the pressure reducing step of two or more battery cells using one control unit, the degassing process can be performed easily and quickly.

On the other hand, the battery cell degassing apparatus may be composed of one chamber, a depressurizing unit, a control unit, and a valve, and since the digital setting method is used, the same opening amount and time can be set for each chamber, Available

However, in such a case, the convenience of the process can be reduced as compared with a case where a plurality of chambers are managed by a single controller, and when the number of the chambers is two or more, The main control unit may further include a main control unit.

The present invention provides a battery cell manufactured using the battery cell degassing apparatus and a battery pack including the battery cell as a unit cell.

The present invention also provides a method for degassing a battery cell, comprising the steps of: removing gas generated during charging and discharging for activating a battery cell in the process of manufacturing a battery cell in which an electrode assembly is embedded in a pouch- A process of disposing a battery cell having been discharged from the outside and then placing it in the chamber; a degassing process of depressurizing the inside of the battery cell step by step according to the amount of opening of the valve set in the control unit to discharge gas inside the battery cell; And maintaining the vacuum state.

In order to prevent a sudden drop in pressure inside the chamber, the valve may be opened stepwise according to the opening amount set for each step. In consideration of the size of the battery cell and the time of vacuum arrival, It can be divided into two or more stages.

Meanwhile, in the degassing process, the holding times of the respective depressurization stages may be set individually, but may be set to the same value for each stage, or may be set to different times.

For example, the degassing process may be performed gradually from the initial stage of decompression to the vacuum state for 1 second to 10 seconds, and the vacuum state may be maintained for several seconds to several tens of seconds. By maintaining the progressive degassing process and the subsequent vacuum state as described above, it is possible to prevent a problem that a variation in the amount of the electrolyte solution discharged from each battery cell occurs, so that the defective rate of the battery cell can be lowered and the productivity can be improved.

As described above, the battery cell degassing apparatus according to the present invention can set the amount of opening of the valve for regulating the vacuum state inside the battery cell and the holding time for each step of depressurization, It is possible to solve the problem that the defective rate of the battery cell is increased due to a difference from the discharge amount of the electrolyte discharged with the gas.

In addition, by increasing the vacuum arrival time, it is possible to reduce variations in the discharge amount of the electrolyte through reduction of the downward pressure deviation occurring between the battery cells, thereby making it possible to manufacture battery cells of uniform quality, It is possible to prevent the shape of the battery case from being deformed.

1 is a schematic view of a battery cell degassing apparatus according to one embodiment;
2 is a schematic view of a battery cell degassing apparatus according to another embodiment;
Figure 3 is a graph showing pressure reduction over time in the chamber as a result of the embodiments; And
Figure 4 is a graph showing the pressure drop over time in the chamber as a result of comparative examples.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings, but the present invention is not limited by the scope of the present invention.

FIG. 1 schematically shows a battery cell degassing apparatus according to the present invention.

Referring to FIG. 1, a battery cell degassing apparatus 100 has a structure in which a vacuum pad is attached to a gas outlet formed in a part of a sealing part of a battery cell, and a vacuum cell is connected to the vacuum pad, A depressurizing portion 120 for evacuating the battery cell to evacuate the battery cell located in the chamber 110, a chamber 110 connected to the battery cell through the vacuum tube, And a control unit 140 for controlling the degree of vacuum in the battery cell by setting the amount of opening of the valve 130. [

The chamber 110 is preferably configured to gradually decrease the internal pressure in the process of degassing the battery cell located inside the chamber 110, and sets the controller 140 such that the opening amount of the valve 130 increases stepwise. At this time, the control unit 140 can set a time at which each step is held, and can set a time for maintaining the vacuum state after reaching the vacuum state.

2 schematically shows another battery cell degassing apparatus according to the present invention.

2, the battery cell degassing apparatus 200 includes three battery cell degassing apparatuses 210, 220, and 230 having the same configuration as the battery cell degassing apparatus 100 of FIG. 1 and their control units 214 , 224, and 234, respectively.

Since the battery cell degassing apparatus 200 further includes a main control unit which can control the controllers 214, 224 and 234 collectively in comparison with the battery cell degassing apparatus 100, It is not necessary to individually set and adjust the controls 214, 224, and 234 for adjusting the internal pressure of the battery cells located in the battery cells 211, 221, and 231. Therefore, by controlling the vacuum step and the vacuum arrival speed of the battery cells located in all the chambers connected to the main control unit, the efficiency of the battery cell degassing process can be improved.

Hereinafter, the present invention will be described with reference to Examples, but the present invention is not limited thereto.

≪ Examples 1 to 4 >

Four spare battery cells prepared by mounting an electrode assembly in a housing part of a battery case made of a laminate sheet, injecting an electrolyte solution, and thermally fusing and sealing are prepared. The preliminary battery cells are activated by repeating a process of charging the battery cells to a charging end voltage of 4.35 V at a charging current of 0.7 C at a temperature of 45 ° C and discharging the battery cells to a voltage of 3.0 V at a discharging current of 1.0C.

A gas discharge port is formed in the spare battery cells after the activation process, the gas discharge port is sealed with a vacuum pad, and then a vacuum tube is connected to the vacuum pad to seal it.

Closed battery cells are moved to chambers 1 to 4, respectively, and a valve capable of digitally regulating opening amount is connected to the battery cells using a vacuum tube. The opening amount and the holding time of the valve were set as shown in Table 1, and the pressure was measured during the degassing process. After reaching the vacuum state, the vacuum state was maintained for 6 seconds.

step Number of dogs (%) Holding Time (sec) Stage 1 25 3.0 Step 2 30 3.0 Step 3 40 3.0 Step 4 100 3.0

The pressure decrease in the battery cell measured in this way is shown in the graph of FIG.

≪ Comparative Examples 1 to 4 >

The electrode assembly is mounted on the housing part of the battery case made of a laminate sheet, the electrolyte is injected, and the four battery cells are prepared by heat sealing. The preliminary battery cells are charged to a charging end voltage of 4.35 V at a charging current of 0.7 C at a temperature of 45 캜, and discharged to 3.0 V with a discharging current of 1.0C.

A gas discharge port is formed in the spare battery cells after the activation process, the gas discharge port is sealed with a vacuum pad, and then a vacuum tube is connected to the vacuum pad to seal it.

Closed battery cells are moved to chambers I to IV, respectively, and a vacuum tube is used to connect the battery cells to the valve that is manually controlled by the opening amount.

The pressure was measured under the condition that the opening of the valve was 100% and the pressure inside the battery cell reached vacuum within 0.5 seconds. The pressure was measured, and the vacuum state was maintained for 6 seconds after reaching the vacuum state.

The pressure decrease in the battery cell measured in this manner is shown in the graph of FIG.

3 and 4, in the case of Embodiments 1 to 4, since the pressure is reduced over a long time such that the time to reach a vacuum state of -90 KPa or less is about 4 seconds, It is possible to prevent the problem that the electrolyte is excessively discharged due to rapid descent.

In addition, since the battery cell degassing apparatus is configured to perform the stepwise depressurization four times in a digital automation manner, there is almost no pressure reduction variation with time between the battery cells, It is possible to manufacture a battery cell of uniform quality under similar conditions.

On the other hand, in the case of the comparative examples 1 to 3, since the time for reaching the vacuum state of -90 KPa or less is very short within 0.5 seconds, an excessive amount of the electrolytic solution is discharged together with the instantaneous gas discharge. In addition, when the valve is manually opened by 100%, the deviation of the pressure decrease due to the time between the battery cells becomes very large, so that the vacuum conditions between the battery cells are different from each other, It is difficult to predict the amount of the electrolytic solution remaining in the inside of the battery cell, and the gas is not completely discharged and residual gas remains in the battery cell.

When the pressure reducing step of the degassing process is subdivided into several stages and the vacuum state is reached in a stepwise manner, since the vacuum reaching time can be increased, the deviation of the electrolyte discharged from the plurality of battery cells becomes small, The degassing process can be stably performed.

It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims (17)

An apparatus for removing a gas generated during charging and discharging for activating a battery in a process of manufacturing a battery cell in which an electrode assembly is embedded in a pouch-shaped case together with an electrolyte,
A chamber in which a battery cell in an enclosed state from the outside is located inside;
A depressurizing portion for sucking air in the battery cell to make the inside of the battery cell into a vacuum state;
A valve disposed between the battery cell and the decompression unit and adjusting a vacuum state inside the chamber by an opening amount; And
A control unit for controlling the amount of opening of the valve to regulate the pressure inside the battery cell based on the gradual decompression;
Wherein the battery cell is a battery cell. The battery cell degassing apparatus according to claim 1, wherein the vacuum state of the battery cell is sequentially reduced by the step-down of the control unit. The battery cell degassing apparatus according to claim 1, wherein the stepwise depressurization is divided into 2 to 10 steps. 4. The battery cell degassing apparatus according to claim 3, wherein the stepwise depressurization is decompression divided into 3 to 6 steps. 2. The battery cell degassing apparatus according to claim 1, wherein the valve is set to an opening amount in a range of 0% to 100%, and the opening amount is operated so as to increase stepwise in order to gradually decrease the pressure. The battery cell degassing apparatus according to claim 1, wherein the control unit sets the pressure holding time for each step. The battery cell degassing apparatus according to claim 6, wherein the holding time of the corresponding pressure is set to be the same for each step. The battery cell degassing apparatus according to claim 1, wherein a vacuum arrival time, which is a time required for the internal pressure of the battery cell to reach a predetermined vacuum state, is in the range of 1 second to 10 seconds. The battery cell degassing apparatus of claim 8, wherein the predetermined vacuum state is set to be maintained for 3 to 30 seconds. 3. The method according to claim 2, wherein the stepwise depressurization is divided into four steps, wherein 25% opening amount in the first step, 30% opening amount in the second step, 40% opening amount in the third step, And the opening degree of the battery cell is set to 100% in the fourth step. The battery cell degassing apparatus according to claim 1, wherein the apparatus includes at least two chambers, and the controller sets the vacuum reach times of the battery cells in all the chambers to be the same. A battery cell manufactured by using the battery cell degassing apparatus according to any one of claims 1 to 11. A battery pack comprising the battery cell according to claim 12 as a unit cell. A method for removing gas generated during charging and discharging for activating a battery cell in the process of manufacturing a battery cell in which an electrode assembly is embedded in a pouch-shaped case together with an electrolyte,
Disposing a battery cell having undergone charging and discharging from the outside and placing it in a chamber;
A degassing process of depressurizing the interior of the battery cells in a stepwise manner to discharge gas inside the battery cells according to the opening amount of the valve set in the control unit; And
Maintaining the vacuum state after reaching the vacuum state;
Wherein the battery cell is provided with a battery cell. 15. The method according to claim 14, wherein the valve is opened stepwise according to an opening amount set for each step. 15. The method of claim 14, wherein the degassing process is divided into at least two stages. 15. The method according to claim 14, wherein the holding times of the respective depressurization steps in the degassing process are individually set.

Images