KR102045246B1 - Method for Preparing Secondary Battery Having Improved Performance of Degassing Process - Google Patents

Abstract

The present invention provides a method of manufacturing a secondary battery for grading capacity, comprising: (i) preparing an electrode assembly including a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode; (ii) accommodating the electrode assembly in a battery case, injecting an electrolyte solution, and then activating a process of applying voltage and leaving the battery at a constant temperature; (iii) a charge / discharge process for setting a capacity class of the battery and a charging process for shipping the initial voltage of the battery; And (iv) a degas process for removing the gas generated in the above processes.

Description

{Method for Preparing Secondary Battery Having Improved Performance of Degassing Process}

The present invention relates to a method for manufacturing a secondary battery for setting a capacity grade, and more particularly, a method for manufacturing a secondary battery in which a charge / discharge process for setting a capacity grade of a battery and a shipping charge process for initial voltage application are performed before a degassing process. It is about.

As technology (Information Technology) technology has developed remarkably, the spread of various portable information and communication devices has made it possible to develop the ubiquitous society, which is capable of providing high quality information services regardless of time and place.

Lithium secondary batteries occupy an important position on the basis of development into such a ubiquitous society. Specifically, the rechargeable lithium battery has been widely used as an energy source of wireless mobile devices such as notebooks, tablet PCs, wearable electronic devices, and the like.

As described above, as the devices to which the lithium secondary battery is applied are diversified, the lithium secondary battery is diversified to provide output and capacity suitable for the device to which the lithium secondary battery is applied.

Meanwhile, lithium secondary batteries may be classified into cylindrical battery cells, rectangular battery cells, and pouch-type battery cells according to the shape of the battery case. The lithium secondary batteries may be stacked with high integration and have high energy density per weight and inexpensive according to the above requirements. Pouch-type battery cells that are easy to deform have attracted much attention.

In particular, recently, a pouch-type battery having a stacked or stacked / folding electrode assembly in a pouch-type battery case of an aluminum laminate sheet has attracted much attention due to its low manufacturing cost, small weight, and easy shape deformation. And its usage is gradually increasing.

In the secondary battery as described above, the first activation process is performed for the first time to inject the electrolyte and charge the battery for the first time while the electrode assembly including the positive electrode, the negative electrode, and the separator interposed therebetween is mounted inside the pouch type battery case. And, after performing a degassing process to remove the gas generated in the activation process, by applying a predetermined voltage to the battery, performs a secondary activation process including a full charge, full discharge, or ripening process, the outer peripheral surface of the case It is produced by sealing the sealing portion formed along the.

At this time, the degassing process is applied to the vacuum suction and pressure to remove the gas generated in the activation process, because the gas is not selectively absorbed and the electrolyte is discharged at the same time, the higher the capacity of the electrolyte is required, the more difficult the process conditions.

In addition, in recent years, a small size of the device is required to be thin, and when an excessive amount of electrolyte is added and a degassing process is performed to meet the appearance standard of the cell, an excess amount of electrolyte is discharged than the set value, thereby ensuring a long life. There is a problem in that the life characteristics and cycle characteristics of the battery is poor due to the lack of electrolyte solution.

On the other hand, when the degassing pressure is lowered to secure the remaining amount of the electrolyte, gas is not sufficiently removed to cause side reactions, thereby deteriorating battery performance, and bubbles are formed to form an undesirable appearance.

Therefore, there is a high need for a technology that can fundamentally solve these problems.

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

An object of the present invention is to perform the charging and discharging process and shipment charging process for setting the capacity grade in the secondary battery manufacturing before the degassing process, reducing the thickness difference between the battery case and the electrode assembly prior to the degassing process, to reduce the electrolyte remaining space This ensures the predictability of the electrolyte discharged during the degassing process.

It is also an object of the present invention to provide a high-density secondary battery that is manufactured by the above-described manufacturing method and has a small size and light weight, and at the same time realizes high voltage and high capacity.

A method of manufacturing a secondary battery for grading capacity according to the present invention for achieving the above object,

(i) preparing an electrode assembly including an anode, a cathode, and a separator interposed between the anode and the cathode;

(ii) accommodating the electrode assembly in a battery case, injecting an electrolyte solution, and then activating a process of applying voltage and leaving the battery at a constant temperature;

(iii) a charge / discharge process for setting a capacity class of the battery and a charging process for shipping the initial voltage of the battery; And

(iv) a degas process for removing gas generated in the above processes;

Characterized in that it comprises a.

That is, in the method of manufacturing a secondary battery according to the present invention, a charge / discharge process for setting a capacity grade and applying an initial voltage is performed before the degassing process, and the electrode assembly expanded by the charge / discharge process is subjected to the degassing process. The battery case is supported so as not to be excessively shrunk even under high pressure conditions, and thus has an effect of ensuring the remaining amount of the electrolyte.

In the charging and discharging process, the positive electrode of the battery is charged with (+), the negative electrode is charged with (-) during charging, and the higher the SOC, the more attractive force is to move the opposite polarity of the electrode and the electrolyte adjacent to the separator. Gets bigger In particular, since the charge and discharge process for setting the capacity grade is generally performed by charging up to 100% SOC, the lithium salt and other electrolytes are attracted into the electrode assembly, and the electrode assembly is further expanded by other reactions.

At this time, the method of manufacturing the secondary battery according to the present invention is intended to ensure a space in which the electrolyte is not discharged during the degassing process, it is preferable to expand only in the thickness direction rather than expanding in all directions.

That is, the type of the electrode assembly is not particularly limited, but it is preferable that the electrode assembly is a stack type or a stack / fold type electrode assembly that expands only in the thickness direction, which will be described in more detail below.

Electrode assemblies may be classified into jelly-roll type, stack type, and stack / fold type electrode assemblies according to structures. Specifically, the jelly-roll type electrode assembly has a structure in which long sheets of positive and negative electrodes are wound with a separator interposed therebetween, and the stacked electrode assembly has a plurality of positive and negative electrodes cut in units of a predetermined size through a separator. The stacked / folding electrode assembly is an electrode assembly having an advanced structure, which is a mixed form of the jelly-roll type and the stacked type, wherein the positive and negative electrodes of a predetermined unit are laminated with a separator therebetween. It has a structure wound sequentially in a state in which the unit cells are placed on the separation film.

Among these electrode assemblies, the electrode assembly of the secondary battery manufacturing method according to the present invention comprises a stacked electrode assembly in which the positive electrode and the negative electrode laminated with a separator interposed therebetween; Or a stack / foldable electrode assembly sequentially wound in a state in which unit cells, in which a positive electrode and a negative electrode of a predetermined unit are stacked with a separator interposed therebetween, are placed on a separation film.

This is because, when the swelling of the electrode assembly due to charging and discharging has no directivity, it is difficult for the accommodating part of the battery case and the electrode assembly to be in close contact with each other, and thus the supporting efficiency in the degassing process is reduced.

In other words, in the degassing process, pressure is applied in the thickness direction of the electrode assembly to remove the gas. If the electrode assembly expands only in the width direction, there is no support effect for the pressurization during the degassing process, thereby preventing the problem of electrolyte over-ejection. Can't solve it.

Therefore, the electrode assembly is preferably expanded only in the thickness direction, which is the pressing direction in the degassing process, and is preferably a stack type / stack folding type electrode assembly that expands in the thickness direction as a whole. Of course, the jelly-roll electrode assembly also expands to a certain extent in the thickness direction, so that the application of the present invention to the jelly-roll electrode assembly is not limited.

In addition, even if the electrode assembly is expanded only in the thickness direction, when the depth of the receiving portion in which the electrode assembly is accommodated in the battery case is too deep, the difference between the depth and the thickness of the electrode assembly is large, the electrolyte may be over-exposed.

Therefore, the depth of the receiving part of the battery case in which the electrode assembly is accommodated is shallower than the thickness of the electrode assembly before the activation process plus 0.1 mm, and the depth of the electrode assembly before the activation process minus 0.1 mm from the thickness of the electrode assembly before the activation process. In more detail, the thickness of the electrode assembly before the activation process may be the same.

Outside the above range, if the depth of the housing portion is too deep than the thickness of the electrode assembly, the amount of the electrolyte that can be discharged by pressurizing during the degassing process is not preferable, the depth of the housing portion is shallower than the thickness of the electrode assembly In this case, storage of the electrode assembly is difficult, which is not preferable.

That is, in the method of manufacturing a secondary battery according to the present invention, after the electrode assembly expands in the thickness direction and adheres to the upper and lower surfaces of the receiving part through a charge / discharge process of setting a capacity rating and initial voltage, the receiving part also expands together, When the degassing process is performed, even if pressure is applied in the vertical direction during the degassing process, the battery case is not excessively contracted, and thus the remaining amount of the electrolyte is secured.

Hereinafter, a method of manufacturing a secondary battery according to the present invention will be described in more detail.

First, in step (i), an electrode assembly including a cathode, a cathode, and a separator interposed between the anode and the cathode is prepared.

The positive electrode is prepared by, for example, applying a mixture of a positive electrode active material, a conductive material, and a binder to a positive electrode current collector, followed by drying, and optionally, a filler is further added to the mixture.

Such a positive electrode active material may be a layered compound such as lithium cobalt oxide (LiCoO ₂ ), lithium nickel oxide (LiNiO ₂ ), or lithium manganese oxide; Lithium copper oxide, vanadium oxide, lithium nickel oxide, lithium manganese composite oxide, LiMn ₂ O _{4 in} which a part of Li in the chemical formula is substituted with alkaline earth metal ions, disulfide compounds, and the like, but are not limited thereto.

The conductive material is typically added in an amount of 1 wt% to 30 wt% based on the total weight of the mixture including the positive electrode active material. The conductive material is not particularly limited as long as it has conductivity without causing chemical change in the battery. Examples of the conductive material include conductive materials such as graphite, carbon black, conductive fibers, metal powders, conductive whiskey, and polyphenylene derivatives. This can be used.

The binder is a component that assists in bonding the active material and the conductive material to the current collector, and is generally added in an amount of 1 wt% to 30 wt% based on the total weight of the mixture including the positive electrode active material. Examples of such a binder include polyvinylidene fluoride, cellulose, rubber, and the like.

The filler is selectively used as a component for inhibiting the expansion of the positive electrode, and is not particularly limited as long as it is a fibrous material without causing chemical change in the battery. For example, a polyolefin polymer and a fibrous material are used.

The negative electrode is manufactured by coating and drying a negative electrode active material on a negative electrode current collector, and optionally, the components as described above may optionally be further included.

As such a negative electrode active material, For example, Conductive polymers, such as carbon, a metal complex oxide, lithium metal, a lithium alloy, a silicon-type alloy, a tin-type alloy, polyacetylene; Li-Co-Ni-based materials, silicon-based materials and the like are used.

The separator is interposed between the anode and the cathode, and an insulating thin film having high ion permeability and mechanical strength is used. The pore diameter of the separator is generally 0.01 μm to 10 μm and the thickness is generally 5 μm to 300 μm. As such a separator, for example, olefin polymers such as chemical resistance and hydrophobic polypropylene; Sheets or non-woven fabrics made of glass fibers or polyethylene are used.

As described above, the electrode assembly including the anode, the cathode, and the separator may be a stack type or a stack / fold type electrode assembly.

Next, in the step (ii), the electrode assembly is accommodated in the battery case, and after the injection of the electrolyte, the activation (formation) process of applying a voltage and the aging process to stand at a constant temperature is performed.

The activation process of the process (ii) corresponds to the primary activation process (primary formation) or pre-charging.

Specifically, the process (ii) may be performed to be set to more than 0% to 20% SOC, in detail, may be performed to be set to more than 15% to 20% SOC.

The first activation process, or precharging process, is a process of initially applying a voltage to a battery, and may include a aging process that is left at a constant SOC and temperature, and the aging process is substantially a battery cell. It is performed for the purpose of checking the capacity of the battery and screening defective products with the activation of, and for the purpose of screening defective products substantially in case of high temperature aging.

Before and / or after the activation process of the process (ii), the aging process may be performed, and may be performed for 1 to 7 days at a temperature in the range of 20 ℃ to 70 ℃.

Specifically, the aging process is a high temperature aging process carried out for 0.5 days to 1.5 days at a temperature in the range of 50 ℃ to 70 ℃, room temperature aging carried out for 1 day to 5 days at a temperature in the range of 20 ℃ to 30 ℃ The process may include, and this aging process can be freely adjusted according to the use of the product.

In one specific example, the process (ii) is charged with SOC 16.7% for primary activation after room temperature aging process (23 ° C. to 27 ° C.) for 2 days, and high temperature aging process (60 ° C.) for 1 day. After performing, it may be carried out through room temperature aging process (23 ° C. to 27 ° C.) again for 4 days.

Next, in step (iii), a charging / discharging process for setting a capacity grade of the battery and a shipping charging process for applying an initial voltage of the battery are performed.

This capacity class setting process corresponds to a secondary activation process, and the secondary activation process is a process of converting chemical energy of the electrode assembly into electrical energy by charging up to SOC, which is generally higher than the primary activation process. .

The capacity grade setting process of step (iii) may be performed by full charge and full discharge.

That is, in the capacity class setting process, the battery is charged to full charge (SOC 100%) and then discharged to confirm the discharge capacity at SOC 0%.

The shipping charging process performed after the capacity class setting process is a process of applying an initial voltage according to a customer's request and a product's use. In one specific example, the charging process is performed by charging in a range of 40% to 60% of SOC. Can be.

As described above, the electrode assembly of the secondary battery, which has undergone the capacity class setting and shipping charging process, expands in the thickness direction and thus adheres to the accommodating part of the battery case, and pushes the accommodating part outward to increase the thickness of the entire secondary battery. .

Specifically, the thickness of the electrode assembly of the secondary battery that has performed the process (iii) is increased within the range of 1% or more and 5% or less based on the thickness of the electrode assembly of the secondary battery before the process (iii). It may be, in detail, may increase in the range of 2% or more to 3% or less.

Next, in the process (iv), a degas process for removing the gas generated in the processes (ii, iii) is performed.

Specifically, the process (iv) may be performed by applying pressure under vacuum conditions, and in one specific example, may be performed through a clamp & bake process performed at a high temperature and in a closed state.

If the degassing process is not sufficiently performed, the gas is not sufficiently removed to form bubbles, so that the appearance is uneven and battery characteristics are deteriorated, and pressure is applied in a state where the thickness of the electrode assembly and the depth of the battery case accommodating part are large. When the degassing process is sufficiently performed, the electrolyte solution is over-discharged, so that a smaller amount of the electrolyte solution than the designed value remains, or the electrolyte solution is contaminated.

In the secondary battery manufacturing method according to the present invention, the capacity grade setting and shipping charging process are performed before the degassing process, and the degassing process without over ejection is performed by reducing the difference between the thickness of the electrode assembly and the depth of the battery case accommodating part before the degassing process. While performing, a large amount of electrolyte can be ensured in the battery cell.

The present invention also provides a secondary battery produced by the above method.

Meanwhile, the secondary battery according to the present invention is preferably a pouch-type lithium ion battery prepared by injecting an electrolyte and degassing by pressure and vacuum after the activation process, and thus the secondary battery includes a resin layer and a metal layer. It is preferable that it is a pouch type secondary battery containing the pouch type battery case which consists of laminated sheets.

The present invention also provides a battery pack including at least one secondary battery, and a device including the battery pack as a power source.

The device may be selected from a mobile phone, a notebook, a tablet PC, a wearable electronic device, an electric vehicle, a battery bicycle, and a wireless aircraft, and in particular, a device that requires a high density battery that realizes high capacity and high voltage while being compact and thin. Can be.

Structures and fabrication methods of these devices are well known in the art, and thus detailed descriptions thereof are omitted herein.

As described above, in the method of manufacturing a secondary battery according to the present invention, the thickness of the electrode assembly is increased through charging and discharging overcharging and shipping charging to set the capacity grade of the battery before the degassing process, and thus, the receiving part and the electrode assembly are increased. To close the space, push out the housing, and support the space where the electrolyte can remain, even under the high pressure condition of the degassing process, thereby increasing the predictability of the amount of electrolyte discharged, securing the desired amount of the electrolyte, It is effective to provide a high density secondary battery that implements high voltage and high capacity.

1 is a perspective view and side views schematically showing a method of manufacturing a secondary battery according to an embodiment of the present invention; And
FIG. 2 is an enlarged perspective view illustrating a secondary battery of process (iii) in FIG. 1 as a specific embodiment of the present invention.

Hereinafter, although described with reference to the drawings according to an embodiment of the present invention, the scope of the present invention is not limited thereto.

FIG. 1 is a perspective view and a side view schematically showing a method of manufacturing a secondary battery as an embodiment of the present invention, and FIG. 2 shows the secondary battery of step (iii) in FIG. 1 as a more specific embodiment. Magnified perspective views are shown.

Referring to FIG. 1, in step (i), the stacked electrode assembly 30 includes a pouch type battery case 20 including a laminate sheet including a resin layer 20A, a metal layer 20B, and a heat seal layer 20C. Prepare.

The pouch-type battery case 20 includes a case main body, a cover connected to one side of the main body, and a concave shape accommodating portion 21 into which the electrode assembly may be seated. At this time, the pouch-type battery case 20 may collect a gas generated in the degassing process afterwards, may include a sealing surplus (not shown) for forming a gas pocket.

In addition, in the process (i), the electrode assembly 30 includes a stacked electrode assembly 30 in which a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode are stacked, and electrode tabs extending from the positive and negative electrodes, respectively. Prepare by welding.

In step (ii), the prepared stacked electrode assembly 30 is stored in the accommodating portion 21 of the pouch-type battery case 20, the electrolyte is injected, and the heat-sealed portion 20C is sealed to seal the secondary battery 10. Manufacture. At this time, it is a matter of course that a stack / folding electrode assembly can be used.

In general, the receiving process of the electrode assembly is performed in a state where the battery case is lateral, and the voltage application process, that is, the activation process and the maturing process, which are performed afterwards, are performed in a state where the battery case is upright. By the activation process and the aging process, gas is collected in the sealing excess of the battery case to form a gas pocket (not shown).

Next, in step (iii), before the degassing process, charging and discharging for setting the capacity class of the battery and shipping charge for applying the initial voltage of the battery are performed. At this time, the electrode assembly 30 is expanded in the thickness direction, hereinafter will be described in more detail with reference to FIG.

Referring to FIG. 2, the stacked electrode assembly 30 accommodated in the pouch-type case 20 is expanded in the thickness direction by step (iii), that is, by the capacity grade setting and shipping charging process.

Specifically, the depth 21a of the accommodating part of the pouch-type case 20 before performing the step (iii) is equal to the value obtained by adding 0.1 mm to the thickness 30a of the electrode assembly. Of course, the depth of the housing and the thickness of the electrode assembly may be the same.

After performing the step (iii), the electrode assembly 30 expands in the thickness direction, whereby the thickness 30b of the electrode assembly and the depth 21b of the receiving portion become the same, and the electrode assembly is formed on the inner surface of the receiving portion. Close contact

The thickness 30b of the electrode assembly was increased by 2% compared to the thickness 30a of the electrode assembly before expansion, and the depth of the accommodating part also increased together with the electrode assembly, thereby increasing the depth of the accommodating part after expansion than the depth 21a of the accommodating part before expansion. Depth 21b is deeper.

Therefore, the secondary battery 10 after the process (iii) is slightly expanded in the thickness direction, and both sides of the pouch-type case 20 are supported by the electrode assembly 30.

Next, in step (iv) of FIG. 1, a degassing process for removing a gas generated in the activation process is applied to both sides of the secondary battery.

With the electrode assembly expanded in step (iii), even if pressure is applied to both sides for the degassing step in step (iv), the electrolyte is not excessively discharged.

On the contrary, in the conventional general secondary battery manufacturing method, the process (iv) is performed between the primary activation process and the secondary activation process, and thus, the supporting effect of the expanded electrode assembly cannot be obtained.

That is, the method of manufacturing a secondary battery according to the present invention performs a charge-discharge process for setting the capacity rating of the battery before the degassing process, and a shipping charge process for applying the initial voltage of the battery, thereby miniaturizing high voltage and high capacity. It provides a method for manufacturing a high density secondary battery and a secondary battery manufactured therefrom that can implement.

Although described above with reference to the drawings according to an embodiment of the present invention, those of ordinary skill in the art will be able to perform a variety of applications and modifications within the scope of the present invention based on the above contents.

Claims (18)

In the method of manufacturing a secondary battery for grading capacity (grading),
(i) preparing an electrode assembly including an anode, a cathode, and a separator interposed between the anode and the cathode;
(ii) accommodating the electrode assembly in a battery case, injecting an electrolyte solution, and then activating a process of applying voltage and leaving the battery at a constant temperature;
(iii) a charge / discharge process for setting a capacity class of the battery and a charging process for shipping the initial voltage of the battery; And
(iv) a degas process for removing the gas generated in the above processes;
Step (ii) to (iv) is to be performed sequentially,
The thickness of the electrode assembly of the secondary battery subjected to the process (iii) is increased in the range of 1% or more to 5% or less based on the thickness of the electrode assembly of the secondary battery before performing the process (iii). Method for producing a secondary battery. The method of claim 1, wherein the electrode assembly,
A stack type electrode assembly in which anodes and cathodes are stacked with a separator interposed therebetween; or
A stack / folding electrode assembly in which unit cells stacked in a state in which a separator and a cathode of a predetermined unit are interposed therebetween are sequentially wound in a state of being placed on a separator film;
Method for producing a secondary battery, characterized in that. The depth of an accommodating part of the battery case in which the electrode assembly is accommodated is shallower than a value obtained by adding 0.1 mm to the thickness of the electrode assembly before the activation process, and 0.1 mm from the thickness of the electrode assembly before the activation process. Method of manufacturing a secondary battery, characterized in that deeper than the subtracted value. The method of claim 1, wherein the depth of the accommodating part of the battery case in which the electrode assembly is accommodated is equal to the thickness of the electrode assembly before the activation process. The method of claim 1, wherein the process (ii) is performed by setting the SOC to more than 0% and 20% or less. The method of claim 1, wherein before and / or after the activation process of the process (ii), a aging process is performed. The method of claim 1, wherein the aging process of the process (ii) is performed at a temperature in a range of 20 ° C. to 70 ° C. for 1 day to 7 days. The method of claim 7, wherein the aging process (ii) is a high temperature aging process performed for 0.5 days to 1.5 days at a temperature in the range of 50 ℃ to 70 ℃, and at a temperature in the range of 20 ℃ to 30 ℃, 1 Method of manufacturing a secondary battery comprising a room temperature aging process performed for one to five days. The method of manufacturing a secondary battery according to claim 1, wherein the capacity class setting process of step (iii) is performed through a full charge and a full discharge process. The method of claim 1, wherein the shipping charging step of the step (iii) is performed by charging in the range of SOC 40% to SOC 60%. delete According to claim 1, wherein the thickness of the electrode assembly of the secondary battery subjected to the process (iii) is in the range of 2% or more to 3% or less based on the thickness of the electrode assembly of the secondary battery before performing the process (iii) The manufacturing method of the secondary battery characterized by the increase in the inside. The method of claim 1, wherein the process (iv) is performed by applying pressure under vacuum conditions. delete delete delete delete delete

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