KR20210095289A - Cell pouch for rechargeable battery having improved hydrofluoric acid resistance and method for preparing the same - Google Patents

Abstract

Disclosed are a cell pouch and a manufacturing method thereof, wherein the cell pouch has two or more multilayer sealant layers, nano-sized calcium carbonate is included in the sealant layers, calcium carbonate is not included in the innermost sealant layer in contact with an electrolyte, and calcium carbonate is included in the sealant layer adjacent to the innermost layer. The corresponding cell pouch is excellent in strength, durability, water vapor and other gas barrier properties, thermal adhesiveness, thermal adhesiveness with electrode terminals, and the like required for the cell pouch and can improve hydrofluoric acid resistance. Accordingly, the deterioration of adhesion between a metal and the sealant layer due to hydrofluoric acid gas can be improved.

Description

Cell pouch for rechargeable battery having improved hydrofluoric acid resistance and method for manufacturing the same

The present specification relates to a cell pouch for a secondary battery having improved hydrofluoric acid resistance and a method for manufacturing the same, and more specifically, a sealant layer, which is an inner layer of a barrier layer of the cell pouch, is applied in multiple layers, and is applied to the sealant layer. It relates to a cell pouch in which an inorganic additive is applied to a polymer material and a method for manufacturing the same.

Lithium secondary batteries (LIBs) are being applied to many applications such as small and medium-sized batteries based on various advantages such as high energy density and excellent output.

However, since a moisture-sensitive electrolyte is used, strict moisture management is required during the manufacturing process. For reference, when moisture penetrates into the secondary battery, the fluorine (F) component contained in the electrolyte and moisture (H ₂ O) react to generate hydrofluoric acid (HF).

Hydrofluoric acid (HF) has a boiling point of 19.5 ^o C and can exist either as a liquid or as a gas. It is a highly permeable and toxic substance. When it occurs inside the battery, the internal pressure of the battery may be increased. In addition, even if a very small amount of hydrofluoric acid is generated inside the battery, it may affect the adhesive layer between the metal of the barrier layer and the sealant layer and cause delamination of the interface.

On the other hand, polypropylene (PP) is a material with excellent mechanical properties and chemical stability, and is widely used as a sealant layer material, which is an inner layer of a cell pouch for secondary batteries, because of its excellent thermal adhesion and heat resistance. Although such polypropylene is relatively stable to hydrofluoric acid, it is difficult to protect the adhesive layer with the metal, which is a component of the barrier layer, when the hydrofluoric acid gas is generated due to weak gas permeability, and thus the adhesive strength may be deteriorated.

Secondary battery manufacturers are conducting hydrofluoric acid resistance evaluation in case moisture penetrates into the battery. That is, in order to evaluate the hydrofluoric acid resistance of the secondary battery, the stability of the cell pouch is evaluated after moisture has been arbitrarily permeated, and a cell pouch with improved hydrofluoric acid resistance is required.

Japanese Patent No. 5463902 Publication

In exemplary embodiments of the present invention, in one aspect, by improving the inner layer material of the cell pouch, the resistance to hydrofluoric acid (HF) that may be generated by the reaction of the electrolyte and moisture, that is, the cell pouch for secondary batteries with improved hydrofluoric acid resistance, and An object of the present invention is to provide a manufacturing method thereof.

In exemplary embodiments of the present invention, in another aspect, as described above, while hydrofluoric acid resistance is improved, the strength, durability, water vapor and other gas barrier properties required for a cell pouch, thermal adhesiveness, and thermal adhesiveness with electrode terminals It is also intended to provide an excellent cell pouch and a method for manufacturing the same.

In exemplary embodiments of the present invention, as a cell pouch having two or more sealant layers, calcium carbonate having a nano size of less than 1000 nm is included in the sealant layer, and the sealant layer, which is the innermost layer in contact with the electrolyte, includes calcium carbonate. It does not, and provides a cell pouch, characterized in that calcium carbonate is included in the sealant layer adjacent to the innermost layer.

In exemplary embodiments of the present invention, as a method for manufacturing a cell pouch, nano-sized calcium carbonate is included in one or more sealant layers when manufacturing a cell pouch having two or more sealant layers, but carbonic acid is provided in the innermost layer in contact with the electrolyte. It provides a method of manufacturing a cell pouch comprising; preventing calcium from being included, and allowing calcium carbonate to be included in the sealant layer adjacent to the innermost layer.

In exemplary embodiments of the present invention, as a method for improving hydrofluoric acid resistance of a cell pouch, nano-sized calcium carbonate is included in one or more sealant layers when manufacturing a cell pouch having two or more sealant layers, but the most It provides a method for improving hydrofluoric acid resistance of a cell pouch, comprising the steps of not containing calcium carbonate in the inner layer, and allowing calcium carbonate to be included in the sealant layer adjacent to the innermost layer.

The cell pouch according to the exemplary embodiments of the present invention is excellent in strength, durability, water vapor and other gas barrier properties, thermal adhesiveness, thermal adhesiveness with electrode terminals, etc. required for a cell pouch, and hydrofluoric acid resistance is improved. can Accordingly, it is possible to improve the deterioration of the adhesion between the metal and the sealant layer due to the hydrofluoric acid gas.

1 is a schematic diagram showing a layer configuration of a cell pouch according to an exemplary embodiment of the present invention.
2 is a schematic diagram showing an inner layer configuration of a cell pouch according to an exemplary embodiment of the present invention.

Nano size in this specification means less than 1000 nm.

In the present specification, n-CaCO ₃ refers to a nano-sized calcium carbonate additive. For example, it may mean a calcium carbonate additive of, for example, 900 nm or less.

In the present specification, m-CaCO ₃ means a calcium carbonate additive of 1 μm or more.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

In exemplary embodiments of the present invention, in the cell pouch for a secondary battery, the sealant layer of the cell pouch is composed of two or more multi-layers, and nano-sized calcium carbonate is included in the sealant layer, but the innermost layer in contact with the electrolyte That is, calcium carbonate is included in the sealant layer adjacent to the innermost layer while not including calcium carbonate in the innermost layer of the multilayer sealant layer.

1 is a schematic diagram showing a layer configuration of a cell pouch according to an exemplary embodiment of the present invention.

1, the cell pouch is composed of an outer layer, a barrier layer, and a sealant layer of an inner layer. Usually, the outer layer or outermost layer is composed of nylon or a mixed material of nylon and PET (polyethylene terephthalate), OPP (stretched polypropylene), polyethylene, and the like. As the required characteristics of the outer layer or the outermost layer, heat resistance, pinhole resistance, chemical resistance, moldability, insulation, and the like are required.

The barrier layer is required to formability together with barrier properties to water vapor or other gases. In this respect, a moldable metal such as aluminum (Al), iron (Fe), copper (Cu), nickel (Ni), etc. is used for the barrier layer, and aluminum is currently the most used.

In the sense that the sealant layer of the inner layer is a layer in contact with the electrolyte along with thermal adhesion and moldability, electrolyte resistance and insulation resistance are required.

Exemplary embodiments of the present invention allow the sealant layer to be formed in a multilayer structure of one or more layers, preferably two or more layers.

2 is a schematic diagram showing an inner layer configuration of a cell pouch according to an exemplary embodiment of the present invention.

2 illustrates a sealant layer having a three-layer structure, a sealant A layer in contact with a barrier layer (metal layer), a sealant B layer as an intermediate layer, and a sealant C layer in direct contact with an electrolyte. The sealant A layer is required to have electrolyte resistance, hydrofluoric acid resistance, and insulation properties as well as adhesion to the metal as a barrier layer. The sealant B layer also requires heat resistance and thermal adhesion, as well as electrolyte resistance, hydrofluoric acid resistance and insulation. The sealant C layer is required to have thermal adhesion, electrolyte resistance, and insulation as well as slip properties and stenosis adhesion.

In exemplary embodiments of the present invention, in the multilayer sealant layer of two or more layers as described above, nano-sized calcium carbonate is included and the innermost layer in contact with the electrolyte, that is, the innermost layer among the multilayer sealant layers (in the case of FIG. 2 ) Sealant C layer) should not contain calcium carbonate. The reason is that when nano-sized CaCO ₃ is directly exposed to the electrolyte, it may be eluted from the sealant layer made of polypropylene or the like into the electrolyte, so it should not be applied to the direct contact layer. In addition, calcium carbonate is included in the sealant layer adjacent to the innermost layer.

Accordingly, the cell pouch has excellent strength, durability, water vapor and other gas barrier properties, thermal adhesiveness, thermal adhesiveness with electrode terminals, etc. Resistance, that is, hydrofluoric acid resistance may be improved.

In detail, hydrofluoric acid can be removed with an inorganic material such as calcium as shown in the following formula.

[Formula 1]

Ca ₂ + HF -> CaF ₂ + H ₂

[Formula 2]

Ca ^{2 +} + 2F ^- -> CaF ₂

In exemplary embodiments of the present invention, among these calcium-based additives, in particular, nano-sized calcium carbonate (CaCO ₃ ) is used. Calcium carbonate is commonly used is to use a micro-size i.e., 1㎛ or more, such as 1 ~ 50㎛ amount of m-CaCO _3, such m-CaCO ₃ is the interfacial adhesion between the polypropylene as the major component of the cell inner pouch Not good.

On the other hand, nano-sized n-CaCO ₃ of less than 1000 nm has a larger surface area than the same amount of m-CaCO ₃ , and by dispersing an appropriate amount in polypropylene, heat resistance can be improved.

In an exemplary embodiment, the nano-sized n-CaCO ₃ may be less than 1000 nm, such as 950 nm or less or 900 nm or less, and may be 200 nm to 900 nm as a non-limiting example. For example, n-CaCO ₃ may be 900 nm or less, 800 nm or less, 700 nm or less, 600 nm or less, 500 nm or less, 400 nm or less, 300 nm or less, 200 nm or more, 300 nm or more, 400 nm or more, 500 nm or more, 600 nm or more, 700 nm or more, 800 nm or more, but is not limited thereto. However, in the case of less than 200 nm, the dispersibility is not good, so processing is difficult, and there is a high possibility that the physical properties may not be uniform.

For reference, the size of calcium carbonate may be measured from, for example, an SEM photograph of calcium carbonate before application of the cell pouch product, and may be an average value of the size of calcium carbonate particles obtained from the SEM photograph.

In an exemplary embodiment, the nano-sized n-CaCO ₃ is preferably adjusted to a certain content. Preferably, n-CaCO ₃ is included in the sealant B layer in an amount of greater than 2% by weight and not more than 15% by weight of the layer composition. When it exceeds 15 wt%, the mechanical properties of each sealant layer are improved, but thermal adhesion properties, electrolyte resistance properties, and metal adhesion properties may be excessively deteriorated. On the other hand, in the case of 2 wt% or less, resistance to hydrofluoric acid may not appear. As an example, n-CaCO ₃ is 15 wt% or less, 14 wt% or less, 13 wt% or less, 12 wt% or less, 11 wt% or less, 10 wt% or less, 9 wt% or less, 8 wt% or less in the corresponding sealant layer composition. % or less, 7 wt% or less, 6 wt% or less, 5 wt% or less, 4 wt% or less, 3 wt% or less, or 2 wt% or more, 3 wt% or more, 4 wt% or more, 5 wt% or less % or more, 6% by weight or more, 7% by weight or more, 8% by weight or more, 9% by weight or more, 10% by weight or more, 11% by weight or more, 12% by weight or more, 13% by weight or more, 14% by weight or more there is.

Preferably, n-CaCO ₃ may be used in an amount of 5 wt% or more and 10 wt% or more, more preferably 5 wt% or more and less than 10 wt% or 5 wt% to 9 wt%.

As described above, the sealant layer film, which is the inner layer of the cell pouch for secondary batteries, is designed as a multilayer, but hydrofluoric acid resistance can be stably implemented by controlling the _{n-CaCO 3 content in the intermediate layer, not in the direct contact layer with the electrolyte.}

Referring back to FIG. 2 , in an exemplary embodiment, the sealant C layer, which is the direct contact layer, preferably has a thickness corresponding to about 10 to 20% of the total sealant layer, and is at least 3 to 10 μm thick. it is suitable If it is too thin, the adhesion between the sealant layer stenosis and the electrolyte resistance may be deteriorated, and if it is too thick, the thermal adhesion may be deteriorated.

In addition, since slip property is required for the sealant C layer, which is the direct contact layer, it is preferable to include at least one additive such as an anti-blocking agent and a slip agent (eg, amide-based). As the anti-blocking agent, inorganic particles such as zeolite and silicon particles are added, and by containing the anti-blocking agent, it is made to protrude on the film surface. On the other hand, the slip agent uses erucamide, behen-amide, oleamide, silicone oil, etc., and by containing the slip agent, the film surface can be made slippery.

In addition, it is preferable that the additive has a content of 1 to 10 wt% in the composition of the sealant C layer, which is the direct contact layer. A content of less than 1% is difficult to realize physical properties, and an amount of 10% or more is transferred to the opposite side of the film in contact with heat adhesion and may adversely affect adhesion with the substrate.

However, as mentioned above, since it is in direct contact with the electrolyte, it is preferable not to include an additive that can be eluted by the electrolyte, such as a calcium carbonate additive.

On the other hand, the sealant B layer, which is the intermediate layer, preferably has a thickness corresponding to 50 to 80% of the total sealant layer, and is preferably at least 10 to 40 μm or more. Since most of the properties required for the sealant layer can be realized from this intermediate layer, it should be thicker than the sealants A and C layers.

In addition, since the intermediate layer is relatively thick compared to the direct contact layer or the metal contact layer, there is an advantage in that it is easy to control the amount of the n-CaCO 3 additive. In such an intermediate layer, it is preferable that the melting point (Tm) of the intermediate layer raw material is 150° C. or higher for heat resistance.

In addition, the sealant layer A, which is the barrier layer contact layer, preferably has a thickness corresponding to 10 to 20% of the total sealant layer for metal adhesion and electrolyte resistance.

On the other hand, in exemplary embodiments of the present invention, there is provided a secondary battery external to the cell pouch described above.

In an exemplary embodiment, the secondary battery may be a lithium secondary battery.

In an exemplary embodiment, the secondary battery may be a small or medium-large secondary battery, and the medium-large secondary battery may be, for example, for an electric vehicle or an energy storage device.

In exemplary embodiments of the present invention, as a method for manufacturing a cell pouch, nano-sized calcium carbonate is included in one or more sealant layers when manufacturing a cell pouch having two or more sealant layers, but carbonic acid is provided in the innermost layer in contact with the electrolyte. It provides a method of manufacturing a cell pouch comprising; preventing calcium from being included, and allowing calcium carbonate to be included in the sealant layer adjacent to the innermost layer.

In exemplary embodiments of the present invention, as a method for improving hydrofluoric acid resistance of a cell pouch, nano-sized calcium carbonate is included in one or more sealant layers when manufacturing a cell pouch having two or more sealant layers, but the most It provides a method for improving hydrofluoric acid resistance of a cell pouch, comprising the steps of not containing calcium carbonate in the inner layer, and allowing calcium carbonate to be included in the sealant layer adjacent to the innermost layer.

Exemplary embodiments of the present invention are described in more detail through the following examples. The embodiments disclosed in this specification are illustrated for the purpose of explanation only, and the embodiments of the present invention may be embodied in various forms and should not be construed as being limited to the embodiments described herein.

[Examples and Comparative Examples]

A known nylon layer was used for the outermost layer common to Examples and Comparative Examples, and a known AL Foil was used for the barrier layer. In addition, polypropylene resin was used in the sealant A, B, and C layers other than calcium carbonate. After each material was mixed and melted, a film was manufactured through T-die extrusion.

In Examples and Comparative Examples, as shown in FIG. 2 , the sealant layer was composed of three layers. Hereinafter, the layer structure of each Example and Comparative Example is described.

comparative example 1: n- CaCO ₃ no addition

In Comparative Example 1, the total thickness of the sealant layer was designed to be 50 μm, the sealant A and C layers were configured to be 4 to 5 μm, and the sealant B layer was designed to be 35 to 40 μm. n-CaCO ₃ was not added.

comparative example 2: sealant on the C floor n- CaCO ₃ 10% by weight adding

In Comparative Example 2, the total thickness of the sealant layer was designed to be 50 μm, the sealant A and C layers were configured to be 4 to 5 μm, the sealant B layer was designed to be 35 to 40 μm, and n-CaCO in the sealant C layer ₃ (200-900 nm; hereinafter the same) was added in an amount of 10% by weight of the total composition of the sealant C layer.

comparative example 3: sealant A floor only n- CaCO ₃ 10% by weight adding

In Comparative Example 3, the total thickness of the sealant layer was 50 μm, the sealant A and C layers were 4 to 5 μm, and the sealant B layer was designed to be 35 to 40 μm, and only the sealant A layer was designed with n-CaCO ₃ was added in an amount of 10% by weight of the total composition of the sealant A layer.

comparative example 4: sealant on the B floor n- CaCO ₃ 2% by weight adding

In Comparative Example 4, the total thickness of the sealant layer was designed to be 50 μm, the sealant A and C layers were configured to be 4 to 5 μm, and the sealant B layer was designed to be 35 to 40 μm, and n-CaCO in the sealant B layer ₃ was added at 2% by weight of the total composition of the sealant B layer.

Example 1: sealant on the B floor n- CaCO ₃ 5% by weight adding

In Example 1, the total thickness of the sealant layer was designed to be 50 μm, the sealant A and C layers were configured to be 4 to 5 μm, and the sealant B layer was designed to be 35 to 40 μm, and n-CaCO in the sealant B layer ₃ was added at 5% by weight of the total composition of the sealant B layer.

Example 2: sealant on the B floor n- CaCO ₃ 10% by weight adding

In Example 2, the total thickness of the sealant layer was designed to be 50 μm, the sealant A and C layers were configured to be 4 to 5 μm, the sealant B layer was designed to be 35 to 40 μm, and n-CaCO in the sealant B layer ₃ was added in an amount of 10% by weight of the total composition of the sealant B layer.

Example 3: sealant on the B floor n- CaCO ₃ 15% by weight adding

In Example 3, the total thickness of the sealant layer was designed to be 50 μm, the sealant A and C layers were configured to be 4 to 5 μm, and the sealant B layer was designed to be 35 to 40 μm, and n-CaCO in the sealant B layer ₃ was added at 15% by weight of the total composition of the sealant B layer.

Example 4: sealant on the B floor n- CaCO ₃ 20% by weight adding

In Example 4, the total thickness of the sealant layer was designed to be 50 μm, the sealant A and C layers were configured to be 4 to 5 μm, and the sealant B layer was designed to be 35 to 40 μm, and n-CaCO in the sealant B layer ₃ was added at 20% by weight of the total composition of the sealant B layer.

Example 5: sealant on the B floor m- CaCO ₃ 20% by weight adding

In Example 5, the total thickness of the sealant layer was designed to be 50 μm, the sealant A and C layers were configured to be 4 to 5 μm, and the sealant B layer was designed to be 35 to 40 μm, and m-CaCO in the sealant B layer ₃ (2-5 μm) was added in an amount of 20% by weight of the total composition of the sealant B layer.

[evaluation]

After each sealant layer was constituted as described above to manufacture a cell pouch, comparative evaluation of hydrofluoric acid resistance and the like was performed. Specifically, the initial peel strength evaluation, hydrofluoric acid resistance strength evaluation, and thermal bonding strength evaluation were performed as follows.

Initial peel strength evaluation

(1) A specimen was prepared by cutting the cell pouch into 1.5 cm in width and 15 cm in length.

(2) The peel strength was measured by peeling the metal layer and the sealant layer.

hydrofluoric acid resistance evaluation

(1) After cutting the cell pouch into 10cm wide and 20cm long, both sides were heat-bonded.

(2) Electrolyte and water (10,000 ppm of electrolyte + water is included in the electrolytic solution + water) were put inside the cell pouch with two sides and were heat-bonded to prepare a pack.

(3) Stored at high temperature (85°C) for 24 hours.

(4) Discard the electrolyte solution inside the pack and prepare a sample as described above for initial peel strength evaluation (width 1.5 cm, length 15 cm).

(5) The peel strength between the metal layer and the sealant layer was measured.

heat adhesion evaluation

(1) A sample was prepared by cutting the cell pouch into 4.5 cm in width and 15 cm in length.

(2) The specimen was folded in the longitudinal direction so that the sealant layers were in contact with each other.

(3) After thermal bonding at 180° C., a specimen with a width of 15 cm was prepared.

(4) The adhesive strength of the heat-bonded surface was measured.

The evaluation results are shown in Tables 1 and 2 below.

Test Items Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Initial peel strength (N/15mm) 14 14 8 13 Hydrofluoric acid resistance (N/15mm) 5 4 One 5 Thermal bonding strength (N/15mm) 120 50 65 120

Test Items Example 1 Example 2 Example 3 Example 4 Example 5 Initial peel strength
(N/15mm) 14 13 14 14 14 Hydrofluoric acid resistance (N/15mm) 11 10 11 11 8 Thermal bonding strength (N/15mm) 120 110 100 80 70

As can be seen from the table above, as in Comparative Example 2, when n-CaCO ₃ was added to the C layer, the hydrofluoric acid resistance was similar to that of Comparative Example 1, but the thermal adhesiveness was significantly inferior. In Comparative Example 3, the adhesion to the substrate (initial peel strength) was reduced, and accordingly, both the hydrofluoric acid resistance and the thermal adhesion strength were reduced.

In Comparative Example 4, _{the amount of n-CaCO 3} added to the B layer was too small to show efficacy, resulting in similar results to Comparative Example 1.

In Example 1, a larger amount of n-CaCO ₃ than in Comparative Example 4 was added, and hydrofluoric acid resistance was improved by this effect.

In Examples 2 to 4, a larger amount of n-CaCO ₃ was added than in Example 1, and the effect of improving initial peel strength and hydrofluoric acid resistance was confirmed. However, as the amount of n-CaCO ₃ added increased, the thermal bonding strength gradually decreased.

In Example 5, m-CaCO ₃ was added in the same amount as in Example 4, but the effect of reducing the thermal adhesive strength occurred, and it was confirmed that the hydrofluoric acid resistance was not significantly improved.

In conclusion, it can be seen that Examples 1 and 2 exhibit the best physical properties.

Although non-limiting and exemplary embodiments of the present invention have been described above, the technical spirit of the present invention is not limited to the accompanying drawings or the above description. It will be apparent to those skilled in the art that various types of modifications are possible within the scope of the present invention without departing from the spirit of the present invention, and also, such modifications will fall within the scope of the claims of the present invention.

Claims (17)

A cell pouch having two or more layers of sealant, comprising:
Including nano-sized calcium carbonate of less than 1000 nm in the sealant layer,
A cell pouch, characterized in that the sealant layer, which is the innermost layer in contact with the electrolyte, does not contain calcium carbonate, and the sealant layer adjacent to the innermost layer contains calcium carbonate.
The method of claim 1,
A cell pouch, characterized in that calcium carbonate is contained in an amount of more than 2% by weight and not more than 15% by weight based on a total weight of 100% by weight of the sealant layer composition adjacent to the innermost layer.
The method of claim 1,
The nano-sized calcium carbonate is a cell pouch, characterized in that 200 ~ 900nm.
The method of claim 1,
The two or more sealant layers include a sealant A layer in contact with the barrier layer, a sealant B layer as an intermediate layer, and a sealant C layer in direct contact with the electrolyte,
The cell pouch, characterized in that the calcium carbonate is included in the sealant B layer.
5. The method of claim 4,
The calcium carbonate is included in the sealant B layer,
A cell pouch, characterized in that calcium carbonate is contained in an amount of more than 2% by weight and not more than 15% by weight based on 100% by weight of the sealant B layer composition.
6. The method of claim 5,
A cell pouch, characterized in that calcium carbonate is contained in an amount of 5 wt% to 10 wt% based on 100 wt% of the sealant B layer composition.
6. The method of claim 5,
A cell pouch, characterized in that calcium carbonate is contained in an amount of 5% to 9% by weight based on 100% by weight of the sealant B layer composition.
5. The method of claim 4,
The sealant layers A and C have a thickness corresponding to 10 to 20% of the total sealant layer,
The cell pouch, characterized in that the sealant B layer has a thickness corresponding to 50 to 80% of the total sealant layer.
5. The method of claim 4,
The cell pouch, characterized in that the sealant C layer contains at least one additive of an anti-blocking agent and a slip agent.
5. The method of claim 4,
The resin included in the sealant layer B has a melting point (Tm) of 150° C. or higher.
The method of claim 1,
Cell pouch, characterized in that the sealant layer contains a polypropylene resin.
A secondary battery, characterized in that it is externally covered with the cell pouch of any one of claims 1 to 11.
13. The method of claim 12,
The secondary battery is a secondary battery, characterized in that the lithium secondary battery.
14. The method of claim 13,
The secondary battery is a secondary battery, characterized in that for an electric vehicle or an energy storage device.
The method for manufacturing the cell pouch of any one of claims 1 to 11,
When manufacturing a cell pouch having two or more sealant layers, nano-sized calcium carbonate is included in one or more sealant layers,
A method for manufacturing a cell pouch, comprising: preventing calcium carbonate from being contained in the innermost layer in contact with the electrolyte, and allowing calcium carbonate to be contained in the sealant layer adjacent to the innermost layer.
As a method of improving hydrofluoric acid resistance of a cell pouch,
When manufacturing a cell pouch having two or more sealant layers, nano-sized calcium carbonate is included in one or more sealant layers,
The method for improving hydrofluoric acid resistance of a cell pouch, comprising: preventing calcium carbonate from being contained in the innermost layer in contact with the electrolyte, and allowing calcium carbonate to be contained in the sealant layer adjacent to the innermost layer.
17. The method of claim 16,
The method is a method for improving the hydrofluoric acid resistance of the cell pouch. Compared to the case where calcium carbonate is not included in the sealant layer, calcium carbonate is added so as to improve the hydrofluoric acid resistance while not lowering the initial peel strength and thermal adhesion strength. A method of improving hydrofluoric acid resistance of a cell pouch.

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