KR101602466B1 - Pouch type secondary battery and method for manufacturing the same - Google Patents

Abstract

The present invention relates to a method of manufacturing a pouch type secondary battery, which comprises the step of applying pressure to a battery cell by a roll press to remove gas generated in the battery cell during an activation process .
According to the manufacturing method of the present invention, the gas generated during the activation process of the secondary battery can be efficiently removed in a short time, and the gas can be collected in a specific direction of the battery cell, so that the gas can be easily removed.

Description

TECHNICAL FIELD [0001] The present invention relates to a pouch type secondary battery, and a pouch type secondary battery produced by the method.

The present invention relates to a manufacturing method of a pouch type secondary battery and a pouch type secondary battery produced thereby.

BACKGROUND ART [0002] In recent years, with the trend toward downsizing and weight reduction of electronic devices, there is also a demand for miniaturization and weight reduction of batteries operating as a power source. BACKGROUND ART [0002] A secondary battery has been put to practical use as a battery which can be miniaturized and lightened and can be recharged and discharged with a high capacity, and is used for portable electronic and communication devices such as a small video camera, a mobile phone, and a notebook computer.

The secondary battery is classified into a cylindrical shape, a square shape, or a pouch type, depending on the shape of the casing to which the electrode assembly is accommodated.

Among them, the pouch type is composed of a metal layer (foil) and a multi-layered film composed of a synthetic resin layer coated on the upper and lower surfaces of the metal layer. Thus, It is possible to reduce the weight of the battery and it is possible to change to various forms.

Conventional pouch facings generally consist of an upper facer material which receives the electrode assembly and an upper facer material which seals the upper part of the lower facer material. At this time, the space portion where the electrode assembly is accommodated may be formed in both the upper and lower portions. Meanwhile, the electrode assembly included in the pouch exterior member includes at least one anode, at least one cathode, and at least one separator interposed between the anode and the cathode, and the kind thereof is not particularly limited. That is, various types of electrode assemblies known in the art such as jelly-roll (rolled) electrode assemblies, stacked (stacked) electrode assemblies, and / or stacked and folded Can be used without limitation.

A conventional jelly-roll type electrode assembly is produced by coating an electrode active material on a metal foil used as a current collector, pressing the electrode active material, cutting the electrode active material into a band having a desired width and length, separating the negative electrode and the positive electrode using a separation film A stacked electrode assembly refers to an electrode assembly manufactured by vertically stacking a cathode, a separator, and an anode. On the other hand, the stack and folding type electrode assembly refers to an electrode assembly manufactured by folding or folding electrode assemblies composed of a single electrode or a cathode / separator / anode with a long sheet-like separation film.

The electrode assembly is housed in a space portion of the lower casing material, and then the edge portion around the lower casing material space is closely contacted with the edge of the upper casing material corresponding thereto, and the electrolyte is injected into the closely adhered portion, A pouch type secondary battery is formed.

On the other hand, in the secondary battery, the activation process for the activation of the cathode active material and the generation of the stable SEI (Solid Electrolyte Interface) in the cathode must be preceded by the characteristics of the secondary battery. A large amount of gas is generated. Subsequently, the generated gas is removed through the opened or incised exhaust port, and the gas exhaust portion is again thermally fused and sealed. As described above, the process of discharging the gas inside the battery cell and thermally fusing the discharge passage is often referred to as a degassing process.

In the case of the pouch type secondary battery, if the gas generated inside the battery cell during the activation process is not efficiently removed as described above, since the gas occupies a certain space inside the battery cell, the central portion of the battery case swells, And adversely affect battery performance such as capacity and output and battery life.

In order to solve such a problem, some techniques for forming a predetermined non-sealing portion between the electrode assembly and the sealing portion of the battery case have been introduced. For example, Japanese Patent Application Laid-Open Nos. 2005-332726 and 2005-222872 disclose a secondary battery in which a laminate electrode assembly is embedded in a housing portion of a laminate sheet, a laminate sheet accommodating portion of the laminate sheet on which the electrode assembly is mounted, Discloses a structure for discharging a gas while spreading sealing portions fused in one direction with a sealing portion between sealing portions of a laminated sheet. Korean Patent Registration No. 10-0876455 discloses a structure in which an electrode assembly is embedded in a laminated sheet storage portion And a gas pocket, which is a surplus portion in a non-sealing state, capable of collecting gas generated between a sealing portion of the battery case and a receiving portion for mounting the electrode assembly, A method of removing the above-mentioned material is disclosed.

However, the conventional method as described above attempts to discharge the gas inside the battery cell due to the natural movement due to the pressure difference between the gas pocket and the inside of the battery cell. In such a method, There is a limit to the effective removal of the gas.

Japanese Patent Application Laid-Open No. 2001-35523 discloses a method for producing a film covered battery comprising a cathode, an anode, an electrolyte and a separator, and a method for inserting a battery between two opposing flat plates and applying pressure from both sides . However, in the above method, the direction in which the gas is collected is not uniform due to the uniform pressure applied to the upper and lower surfaces of the battery cell. If the gas can be collected in a direction in which the electrode assembly is not wrapped by the folding separator, the gas can be removed more efficiently, so it is necessary to collect and remove the gas to a specific portion of the battery cell. Also, in a large area cell, it is necessary to precisely control the level of the flat plate in order to apply a uniform pressure to the entire cell, so that problems such as productivity decrease and deviation between products may occur.

Disclosure of Invention Technical Problem [8] Accordingly, the present invention has been made in view of the above problems, and it is an object of the present invention to solve the problems of not effectively removing gas generated in a battery cell in a short period of time and leading to a specific portion of a battery cell.

To this end, according to one embodiment,

(a) providing a battery cell having an electrode assembly and an electrolyte therein;

(b) activating the battery cell by performing at least one charge and discharge at least once;

(c) applying pressure to the battery cell using a roll press to induce gas generated in the battery cell in one direction; And

(d) discharging the gas induced in the one direction

The present invention also provides a method of manufacturing a pouch type secondary battery.

The electrode terminals of the electrode assembly may be exposed in parallel with the upper end of the battery cell in the same direction.

The battery cell may further include a gas pocket for receiving the induced gas.

The battery cell may be charged with a current of 0.05 C to 1 C at a voltage of 1.5 V to 5 V, and then charged again to activate the battery cell.

The application of the pressure to the battery cell may be performed simultaneously with the activation process or after the activation process.

The application of the pressure to the battery cell may be performed in all or a part of the activation process after opening the lower end of the battery cell.

The application of pressure to the battery cell may be performed in a vacuum chamber in a reduced pressure state.

One direction for applying the pressure to the battery cell by the roll press to induce the gas may be the lower end direction from the upper end where the electrode terminal of the battery cell is exposed.

The battery cell may have a gas pocket formed in the battery cell after the electrode assembly is housed in the battery case and then sealed.

The gas may be removed by cutting a portion of the gas pocket and applying pressure to the roll press during all or a portion of the activation process.

The removal of the gas may be performed in a vacuum chamber in a reduced pressure state.

The present invention provides a pouch-type secondary battery manufactured by the above manufacturing method.

In the pouch type secondary battery manufactured by the above manufacturing method, the gas volume inside the battery cell of the pouch type secondary battery may be 0.5% to 5% of the entire volume of the battery cell excluding the exterior material.

According to the manufacturing method of the present invention, the gas generated during the activation process of the secondary battery can be efficiently removed in a short time, and the gas can be collected in a specific direction of the battery cell, so that the gas can be easily removed.

1 is a front view of a battery cell having a gas pocket portion according to an embodiment of the present invention.
FIG. 2 is a schematic view illustrating a method of applying a roll press on a battery cell for explaining an embodiment of the manufacturing method of the present invention.
Figure 3 is a side view of Figure 2;
4 is a front view of a battery cell having a gas pocket portion provided with a discharge portion according to another embodiment of the present invention.
5 is a graph showing the battery capacity of a battery cell manufactured by the manufacturing method of the embodiment of the present invention, the comparative example 1 and the comparative example 2 as the life evaluation cycle progresses.

Hereinafter, the present invention will be described more specifically.

The inventors of the present invention have attempted to effectively remove the gas occupying a certain space in the battery cell by the conventional method of attempting to discharge the gas inside the battery cell due to the natural movement due to the pressure difference inside the battery cell, In the method of applying the pressure between both sides of the battery by sandwiching the battery between the two flat plates facing each other, since the uniform pressure is applied to the upper and lower surfaces of the battery cell, the direction in which the gas is collected is not constant, It is recognized that there is a problem that it is difficult to collect and remove the gas and it is found that the gas generated in the activation process can be efficiently removed by controlling the gas collection direction by applying pressure to the battery cell by the roll press, Respectively.

More particularly, the present invention provides a method of manufacturing a pouch type secondary battery, comprising: (a) providing a battery cell having an electrode assembly and an electrolyte therein; (b) charging the battery cell or performing charging and discharging at least once Activating the battery cell; (c) applying pressure to the battery cell using a roll press to induce gas generated in the battery cell in one direction; And (d) discharging the gas induced in the one direction.

Hereinafter, each step of the present invention will be described in more detail.

The step (a) of preparing the battery cell in which the electrode assembly and the electrolyte are accommodated may be performed through a method of manufacturing a battery cell well known in the art. For example, the electrode assembly may be stored in the pouch- , Injecting an electrolyte solution, sealing the electrolyte solution, or the like.

The electrode assembly that can be used in the present invention is a concept including all electrode assemblies including at least one anode, at least one cathode, and at least one separator, and the shape and the like are not particularly limited.

The materials of the positive electrode, negative electrode and separator included in the electrode assembly of the present invention are not particularly limited, and any of the positive electrodes, negative electrodes and separators known in the art may be used without limitation. For example, the negative electrode may be made of a lithium metal, a lithium alloy, a carbon, a petroleum coke, an activated carbon, a graphite, a silicon compound, or a mixture thereof with a negative electrode current collector made of copper, nickel, aluminum or an alloy containing at least one of them. , A tin compound, a titanium compound, or an alloy thereof, or the like. The positive electrode may be formed of, for example, lithium manganese oxide, lithium cobalt oxide, lithium nickel oxide, lithium iron phosphate, or the like, to the positive electrode current collector made of aluminum, nickel, copper, or an alloy containing at least one of them. , Or a compound containing at least one of the foregoing, and a mixture thereof, or the like. In addition, the electrode active materials may be coated on both sides of the current collector, or may be coated on only one side of the current collector in order to form an uncoated portion. The thicknesses of the positive electrode and the negative electrode are not particularly limited. That is, these thicknesses can be set in consideration of the purpose of use such as output or energy-weighted or ionic-conductive importance.

On the other hand, the separation membrane may be a multilayer film produced by, for example, polyethylene, polypropylene, or a combination thereof having a microporous structure, or a multilayer film produced by combining polyvinylidene fluoride, polyethylene oxide, polyacrylonitrile or polyvinylidene fluoride And a polymer film for a solid polymer electrolyte such as a hexafluoropropylene copolymer or a gel polymer electrolyte polymer.

As the electrode assembly, various types of electrode assemblies used in the art, for example, jelly-roll, stacked or stacked and folded electrode assemblies can be used without limitation. At this time, the jelly-roll type electrode assembly is coated with an electrode active material on a metal foil used as a current collector, pressed, cut into a band shape having a desired width and length, and then separated into a diaphragm The stacked electrode assembly refers to an electrode assembly manufactured by vertically stacking a cathode, a separator, and an anode. On the other hand, the stack and folding type electrode assembly refers to an electrode assembly manufactured by folding or folding electrode assemblies composed of a single electrode or a cathode / separator / anode with a long sheet-like separation film.

In the case of the stack and folding type electrode assembly, since the electrode stacked body composed of a single electrode or a cathode / separator / anode is surrounded by the sheet type separation film, the expansion of the electrode or electrode stacked body is suppressed by the sheet type separation film, Which is superior in stability. However, it is difficult to discharge the gas generated in the battery cell to the outside due to the presence of the sheet-type separation film. However, in the case of using the manufacturing method of the present invention in which the gas generated in the battery cell is directed in one direction , The above problems can be solved. Therefore, the present invention can provide more efficient results in a battery cell composed of stacked and folded electrode assemblies in which gas discharge is not easy.

As the pouch outer cover material, various types of outer cover materials well known in the art can be used without limitation, for example, a laminate sheet, wherein the laminate sheet has an outermost outer resin layer, A barrier metal layer for preventing penetration of the resin, and an inner resin layer for sealing. An example of such a laminate sheet, it is possible in the aluminum laminate sheet, the aluminum sheet is laminated nylon-aluminum-polypropylene film with a thickness of about 100㎛ layer configured such as, heat and 1-3 of 160 ~ 210 ℃ kg _f / Cm < 2 >.

As the electrolyte, various electrolytes used in the technical field can be used without limitation. For example, an organic solvent composed of PC (propylene carbonate) and EC (ethylene carbonate) and a lithium salt (LiPF ₆ ). The organic solvent is not particularly limited to PC and EC, and may include, for example, other cyclic carbonates, chain-like carbonates such as dimethyl carbonate, and ethers such as tetrahydrofuran. The lithium salt is not particularly limited to LiPF ₆ , but may include, for example, other inorganic acid anion salts and organic acid anion salts such as LiCF ₃ SO ₃ .

Meanwhile, the battery cell may further include a gas pocket portion for accommodating the induced gas, if necessary. 1 shows an embodiment of a battery cell of the present invention having a gas pocket portion 50 according to the present invention. 1, when the gas pocket portion 50 is provided, it is preferable that the gas pocket portion 50 is formed on the side where the electrode terminal 60 is not formed, more preferably, 60, for example, at the lower end of the battery cell. This is because, when the gas pocket portion 50 is formed on the surface on which the electrode terminal is formed, the moving direction of the roll press faces the electrode terminal, and there is a risk of damaging the electrode terminal while performing the process. Further, when the gas pocket portion 50 is formed at the lower end portion of the battery cell, there is an advantage that it is easier to discharge the gas present in the sheet-like separation film when the stack and folding type electrode assembly is used. In the case of the stack and folding type electrode assembly, the side portion is wrapped with a sheet-type separation film, and the sheet-type separation film is not generally present at the bottom portion. Therefore, it is easier to discharge the gas inside the stack and folding type electrode assembly by providing the gas pocket portion at the lower end of the battery cell.

However, FIG. 1 is merely an example of the present invention, and the present invention is not limited thereto. That is, the battery cell of the present invention does not have a separate gas pocket portion 50, and can collect gas in a surplus space inside the battery case accommodating the electrode assembly.

Next, the step (b) is for activating the battery cell, The battery cell is charged or discharged at least once, but the present invention is not limited thereto. For example, in the step (b), defective open-circuit voltage (OCV) is detected by charging only a part of the battery cell with a current of 0.2 C or after aging the battery cell, The discharge capacity is measured and then charged to 50% of the capacity for shipment, and the like. Specifically, the activation process may be performed at a current of about 0.05C to 1C and a voltage of about 1.5V to 5.0V.

Next, in step (c), pressure is applied to the battery cell by a roll press in order to induce gas generated in the battery cell in one direction of the battery cell during the activation process. Figs. 2 and 3 show an embodiment of the step (c).

As shown in FIGS. 2 and 3, the step (c) may be carried out by placing the roll press on the upper part of the battery cell and pressing the roll while moving the gas in a direction to induce the gas. For example, as shown in FIG. 3, in the case of the battery cell in which the gas pocket portion 50 is mounted at the lower end of the battery cell, the roll (in the direction of the lower end 20 of the battery cell) 70), and applying pressure while moving the press. The gas 80 generated in the battery cell through the above process is collected in the gas pocket portion 50.

At this time, electrode terminals 60 for electrically connecting the electrode assembly to the upper end 10 of the battery cell may be provided. In this case, the roll 70 presses in a direction away from the electrode terminals 60, That is, it is preferable that the electrode terminals 60 are moved in the direction of the lower end 20 of the battery cell from the upper end 10 of the exposed battery cell, and the pressure is applied. When the roll press 60 is moved in the same direction as described above, it is possible to prevent the electrode terminals from being damaged during the pressure application process.

According to this method, when the gas is collected from the stacked and folded electrode assembly to the side surfaces 30 and 40 of the battery cell, the single electrode or the unit cells are wound, The problem of difficulty in discharging can be solved, so that the present invention can be particularly useful for the stack and folding type. Also, if the roll 70 press is applied in the lateral direction facing the one side of the battery cell, the problem that the electrode terminal 60 may be damaged can be solved.

In the present invention, by applying pressure while moving the roll 70, an artificial gas is moved by pressurization rather than the movement of the natural gas, thereby allowing the gas in the battery cell to be discharged efficiently and efficiently. The performance of the battery is improved and the life of the battery is extended. In addition, since the gas is continuously discharged by the artificial pressure, the inside of the battery cell is kept in the reduced pressure state, so that the swelling phenomenon in which the central portion of the battery cell swells up due to the excessive pressure is suppressed. In addition, when the roll press is used, since the pressing direction is easily adjusted, it is possible to prevent the electrolyte from being excessively lost during the pressing process.

On the other hand, it is caused by the rolls 70, press pressure is 30kg _f / ㎠ is the preferred, is not proven to effectively discharge effect of the gas to which the present invention seek if the pressure is less than 3kg _f / ㎠, applying pressure 200kg _f / Cm < 2 >, the sealing state of the battery cell or the occurrence of a short circuit between the electrode-separation membrane and the electrode It is undesirable because it may affect the performance. At this time, the linear velocity of the roll 70 is preferably 0.5 m / min to 10 m / min.

On the other hand, the step of applying pressure by the roll 70 press may be performed during all or a part of the activation process of step (b). Continuous application of pressure throughout the activation process may be desirable in view of the performance of the process and ensuring a clear discharge of the generated gas, but it may be possible that additional leakage of electrolyte may occur and additional costs may arise, It may be performed fluidly so as to apply pressure only during a specific period in which the occurrence is severe.

Alternatively, the step (c) may be performed after the activation process of step (b) is completed. In this case, by applying a pressure to the battery cell using the roll press, the gas trapped in the battery cell generated in the activation process can be guided in one direction.

Further, the step (c) may be performed in a reduced pressure state, if necessary. When step (c) is performed under a reduced pressure, step (c) and step (d) described below can be performed simultaneously.

Next, the discharging of the gas induced in the one direction in the step (d) may be performed by discharging gas to the outside of the battery cell, for example, by a method of opening a part of the battery cell have. For example, the step of discharging the gas may be performed by opening a part of the battery cell, opening a part of the gas pocket part in the case of the battery cell having the gas pocket part, or separating the gas pocket part from the battery cell . At this time, the opening may be performed by cutting, cutting, or punching a part of the battery cell.

Further, the step of discharging the gas for smooth gas discharge may be performed while applying pressure to the roll press, or may be performed at a reduced pressure.

4 shows a front view of a battery cell in which a cut portion 90 is formed in a gas collecting portion 80 of the gas pocket portion 50 as an embodiment of the gas removing method. The gas can be removed by drilling a part of the hole 90 in the gas trapped portion 80 of the gas pocket portion 50 during the activation process or after the activation process or by cutting off the center of the gas trapped portion 80. At this time, degassing is preferably carried out in a vacuum chamber in a reduced pressure state.

Meanwhile, it is preferable to reseal the cut, cut or punched portion after the gas is discharged through the above process. In the case of the battery cell having the gas pocket portion 50, a portion where the gas pocket portion 50 is formed after gas discharge can be cut from the battery cell, and the cut portion can be resealed again.

In the pouch type secondary battery manufactured by the method of the present invention as described above, the amount of gas remaining in the battery cell is maintained at 5% or less of the internal volume of the battery cell. The amount of gas remaining in the battery cell is 10% or less. In this manner, the life of the battery cell is improved by minimizing the amount of the residual gas in the battery cell, the lithium precipitation on the electrode is suppressed, and the output of the battery cell is improved.

Hereinafter, the present invention will be described in detail with reference to specific examples.

Example

A pouch-type lithium secondary battery was fabricated in the following manner.

Manufacture of anode

90 wt% of NMC (Li [Ni, Mn, Co] O ₂ ), 5 wt% of carbon black as a conductive material, and 5 wt% of polyvinylidene fluoride as a binder were dissolved in NMP (N-methyl- pyrrolidone) to prepare a positive electrode mixture slurry. The slurry of the positive electrode mixture was applied to an aluminum foil having a thickness of 20 mu m as a positive electrode plate and dried to prepare a positive electrode, followed by roll pressing.

Cathode manufacturing

95 wt% of carbon powder, 2 wt% of carbon black as a conductive material, 1 wt% of carboxymethyl cellulose (CMC) as a thickener and 2 wt% of styrene butadiene rubber (SBR) as a binder were added to distilled water as a negative electrode active material, A mixture slurry was prepared. The negative electrode mixture slurry was applied to a Cu foil having a thickness of 10 탆, which was a negative electrode plate, Dried to prepare a negative electrode, and then roll 70 was pressed.

Of the battery cell  Produce

A 20Ah 1C capacity electrode assembly was fabricated by stacking and folding the PP / PE / PP separator between the anode and cathode fabricated in the above manner.

An aluminum foil metal foil layer was formed on the heat fusion layer, and then an insulating layer was laminated on the aluminum foil metal foil layer to prepare a pouch exterior material. The manufactured pouch exterior member was bent to form an upper exterior member and a lower exterior member, and then an electrode assembly receiving portion was formed by press working on the lower exterior member.

Accommodating the electrode assembly is manufactured in the compartment to the next, an electrolyte (ethylene carbonate (EC) / propylene carbonate (PC) / diethyl carbonate (DEC) = 30/20/50% by weight of lithium hexafluoro phosphate flow (LiPF ₆ ) 1 mole) was injected.

Perform activation process

A gas pocket portion 50 having a length of 8 cm and a width of 15 cm was formed on the lower end 20 side of the battery cell in the pouch exterior member of the battery cell. The battery cell to which the gas pocket portion 50 was connected was charged at a constant current (CC) until a voltage of 3.8 V was reached at a current of 0.1 C at room temperature Lt; / RTI >

Digging ( Degassing ) process

The activation process to rough the battery cells 30 kg _f / ㎠ pressure to the electrode terminal 60 was the press roll 70 in the bottom 20, the direction from the top 10 of the exposure. At this time, the temperature of the roll 70 was 80 占 폚 and the linear velocity was 1.5 m / min.

After the roll 70 is pressed to collect the gas in the direction of the lower end 20 of the battery cell, the hole 90 is opened in the gas pocket portion 50 and the gas is removed at a pressure of -95 kPa for 2 seconds. (50) was cut and removed.

Comparative Example  One

The experiment was conducted under the same conditions as those of the example except that no roll (70) press was applied during the degassing process.

Comparative Example  2

D. Instead of applying a roll (70) presses during gaesing process, and is carried out, except into a cell between two flat plates opposed to applying a flat plate press at a temperature of 80 ℃ at a pressure of 200kg _f / ㎠ for 4 seconds The experiment was carried out under the same conditions as in the example.

Comparative Example  3

The gas pocket portion 50 was formed on the side surfaces 30 and 40 of the battery cell and was tested under the same conditions as those of the embodiment except that the roll press was applied from one side to the other side of the battery cell.

Experimental Example  One( Battery cell  Analysis of internal gas volume)

A battery cell was inserted into the vacuum chamber and a vacuum pressure of -760 mmHg was applied. After confirming that the pressure of the chamber reached -760 mmHg, a hole was drilled in the outer shell of the battery cell, and a tube was connected to the outer shell of the battery cell to collect gas released from the chamber for 10 minutes. The amount of gas was analyzed by GC-Mass.

Experimental Example  2( Battery cell  Life evaluation)

After the degassing, charge the CC / CV 4.2V 1C at 45 ° C - 20 minutes at rest - CC 3.0V 2C discharge - 20 minutes At 300 cycles in the order of dormancy, measure the capacity of the battery cell to evaluate the life of the battery cell Respectively.

In order to analyze the residual gas amount of the battery cell manufactured by the manufacturing method of the example, the comparative example 1, the comparative example 2, and the comparative example 3, the results of the example 1 and the results of the examples, the comparative example 1 and the comparative example 2 The results of the experiment 2 are shown in Table 1 for the evaluation of the life of the battery cell.

Example Comparative Example 1 Comparative Example 2 Comparative Example 3 Remaining gas amount (V / V,%) 1.2 8.3 6.1 6.7 After 300 cycles
Remaining battery cell capacity (%) 98.2 95.9 96.9 -

The results of Table 1 show that the residual gas amount in the case where the roll press or the flat press is not applied (Comparative Example 1) is the highest and the residual gas amount in the case where the roll press is applied (Example) It can be seen that the amount of residual gas in the produced battery cell is the lowest.

The residual gas amount in the case where the gas pocket portion 50 is formed on the side surfaces 30 and 40 of the battery cell and the roll press is applied from one side of the battery cell to the other side (Comparative Example 3) The gas pocket portion 50 is formed on the side surfaces 30 and 40 of the battery cell because the gas pocket portion 50 is higher than the residual gas amount in the case where the roll 70 is pressed from the exposed upper end 10 toward the lower end 20 Forming the lower end 20 of the battery cell is more effective in removing the gas through the subsequent roll press process.

5 shows the battery capacities of the battery cells manufactured by the method of the embodiment, the comparative example 1, and the comparative example 2, respectively. FIG. 5 is a graph showing a change in battery capacity as a cycle of life evaluation proceeds.

Referring to FIG. 5, it can be seen that, in the embodiment manufactured by applying the roll press, the reduction width with the progress of the life evaluation cycle of the battery capacity is the smallest.

10: Top of battery cell
20: Lower part of the battery cell
30, 40: side surface of the battery cell
50: gas pocket portion
60: Electrode terminal
70: roll
80: part where the gas generated inside the battery cell is collected
90:

Claims (14)

(a) providing a battery cell having an electrode assembly and an electrolyte therein;
(b) activating the battery cell by charging the battery cell or performing at least one charge and discharge at least once;
(c) applying pressure to the battery cell using a roll press to induce gas generated in the battery cell in one direction; And
(d) discharging the gas induced in the one direction.
The method according to claim 1,
Wherein the electrode assembly in step (a) is a stack and folding type electrode assembly.
The method according to claim 1,
Wherein the battery cell of the step (a) further comprises a gas pocket for accommodating the induced gas.
The method according to claim 1,
Wherein the step (b) comprises charging the battery at a current of 0.05 C to 1 C at a voltage of 1.5 V to 5.0 V, and then discharging the battery again, thereby activating the battery cell.
The method according to claim 1,
Wherein the step (c) is performed at a speed of 0.5 m / min. To 10 m / min, and the roll press is performed at a pressure of 3 kg _f / cm 2 to 200 kg _f / cm 2.
The method according to claim 1,
Wherein the step (c) is performed while moving the roll press from the upper end to the lower end of the battery cell.
The method according to claim 1,
Wherein the step (c) is performed at the same time as the step (b) or after the step (b).
The method according to claim 1,
Wherein the step (c) is performed in all or part of the step (b).
The method according to claim 1,
Wherein the step (c) is performed in a vacuum chamber in a reduced pressure state.
The method according to claim 1,
Wherein the step (d) is performed by opening a part of the battery cell.
The method of claim 3,
Wherein the step (d) is performed by a method of opening part or all of the gas pocket portion.
The method according to claim 1,
Wherein the step (d) is performed in a vacuum chamber in a reduced pressure state.
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