KR20220055846A - Coin-type secondary battery with anti-corrosion layer on inner surface of battery case - Google Patents

Abstract

Provided is a coin-type secondary battery capable of efficiently suppressing corrosion of a coin-type secondary battery case due to contact with an electrolyte. The battery includes: a coin-type electrode assembly including a cathode, an anode, and a separator interposed between the cathode and the anode; a first case accommodating the electrode assembly; a second case covering a upper portion of the first case; a spring and a spacer filling an inner space except the electrode assembly in the inside of the first case and the second case; wherein the first case, the second case, the spring, and the spacer are made of metal; an anti-corrosion layer made of one type selected from the group consisting of a primer layer, a conductive polymer layer, and a conductive epoxy layer is formed on the surface of the first case, the second case, the spring, and the spacer in contact with an electrolyte; and the primer layer includes graphene.

Description

A coin-type secondary battery with an anti-corrosion layer formed on the inner surface of the battery case {COIN-TYPE SECONDARY BATTERY WITH ANTI-CORROSION LAYER ON INNER SURFACE OF BATTERY CASE}

The present invention relates to a coin-type secondary battery in which a corrosion-preventing layer is formed on the inner surface of a battery case.

Due to the rapid increase in the use of fossil fuels, the demand for the use of alternative energy or clean energy is increasing.

Currently, a secondary battery is a representative example of an electrochemical device using such electrochemical energy, and its use area is gradually expanding.

In recent years, as technology development and demand for portable devices such as portable computers, portable phones, and cameras increase, the demand for secondary batteries as an energy source is rapidly increasing. A lot of research has been done on an eco-friendly lithium secondary battery, and it has also been commercialized and widely used.

In general, a lithium secondary battery has a structure embedded in a battery case in a state in which a non-aqueous electrolyte is impregnated in an electrode assembly comprising a positive electrode, a negative electrode, and a porous separator.

In this case, in general, the secondary battery is a stack/folding type or a cylindrical or prismatic secondary battery, stacked or stacked/folding type for accommodating a wound electrode assembly in a metal can as a battery case depending on the shape of the battery case. It is divided into a pouch-type battery in which the electrode assembly is embedded in a pouch-type battery case of an aluminum laminate sheet, and a coin-type secondary battery in which a coin-type electrode assembly is accommodated in an upper case made of metal and a lower case.

Here, the exterior material of the coin-type secondary battery, ie, the battery case, is generally made of metal, and in particular, made of stainless steel (SUS).

However, when such a metal comes into contact with an electrolyte, corrosion occurs, and in particular, when an imide-based lithium salt is used, there is a problem that corrosion is deepened.

Accordingly, conventionally, the battery case of these coin cells is coated with a cheap metal such as Cr, Zn, and Sn, which does not easily corrode, to inhibit corrosion. , there was a problem of causing browning on the metal surface.

Therefore, it is necessary to develop a technology for a coin-type secondary battery capable of effectively preventing corrosion of a metal can regardless of the type of electrolyte by solving this problem.

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

Specifically, an object of the present invention is to provide a coin-type secondary battery capable of effectively suppressing corrosion of the coin-type secondary battery case due to contact with an electrolyte.

Coin-type secondary battery according to an embodiment of the present invention for achieving this object, a coin-type electrode assembly including a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode;

a first case for accommodating the electrode assembly;

a second case covering the upper end of the first case; and

a spring and a spacer filling an inner space excluding the electrode assembly in the first case and the second case;

including,

The first case, the second case, the spring, and the spacer are made of metal,

A corrosion prevention layer made of one selected from the group consisting of a primer layer, a conductive polymer layer, and a conductive epoxy layer is formed on the surface of the first case, the second case, the spring, and the spacer in contact with the electrolyte,

The primer layer is characterized in that it includes graphene.

In this case, the metal may be made of any one selected from the group consisting of aluminum, nickel, stainless steel (SUS), copper, iron, bronze, and brass.

Also, the coin-type secondary battery may further include a gasket sealing the first case and the second case.

The anti-corrosion layer may be formed to a thickness of 0.01 μm to 100 μm.

Meanwhile, in one specific example, the primer layer may further include a binder polymer together with graphene.

The conductive polymer layer is polyethylenedioxythiophene/polystyrenesulfonate (PEDOT/PSS; poly(3,4-ethylenedioxythiophene)/poly(4-styrene sulfonate), polyaniline (PANI; polyaniline), polypyrrole (PPy; polypyrrole), poly It may include one or more conductive polymers selected from the group consisting of thiophene (PT), polyacetylene (PA), and poly para-phenylene vinylene (PPV).

The conductive epoxy layer may include at least one conductive filler selected from the group consisting of gold, platinum, silver, copper, or nickel metal powder, carbon or carbon fiber, graphite, and composite powder, and an epoxy polymer. there is.

As described above, in the coin-type secondary battery according to an embodiment of the present invention, by forming a corrosion prevention layer on the surface that can be in contact with the electrolyte of the first case and the second case, the spring and the spacer, corrosion by the electrolyte This can be effectively prevented, and/or suppressed.

In addition, since the corrosion-preventing layer has conductivity, it is possible to effectively prevent corrosion by covering the entire portion that can be corroded by the electrolyte without lowering the conductivity.

1 is an exploded perspective view of a coin-type secondary battery according to an embodiment of the present invention.
2 is a cross-sectional schematic view of a coin-type secondary battery according to an embodiment of the present invention.

Hereinafter, the present invention will be described in more detail to help the understanding of the present invention.

The terms or words used in the present specification and claims are not to be construed as being limited to their ordinary or dictionary meanings, and the inventor may properly define the concept of the term in order to best describe his invention. Based on the principle that there is, it should be interpreted as meaning and concept consistent with the technical idea of the present invention.

The terminology used herein is used to describe exemplary embodiments only, and is not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly dictates otherwise.

In addition, throughout the specification, when a part "includes" a certain component, this means that other components may be further included, rather than excluding other components, unless otherwise stated.

According to one embodiment of the present invention,

a coin-shaped electrode assembly including a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode;

a first case for accommodating the electrode assembly;

a second case covering the upper end of the first case; and

a spring and a spacer filling an inner space excluding the electrode assembly in the first case and the second case;

including,

The first case, the second case, the spring, and the spacer are made of metal,

A corrosion prevention layer made of one selected from the group consisting of a primer layer, a conductive polymer layer, and a conductive epoxy layer is formed on the surface of the first case, the second case, the spring, and the spacer in contact with the electrolyte,

The primer layer is provided with a coin-type secondary battery including graphene.

In this case, the metal forming the first case, the second case, the spring, and the spacer may be made of any one selected from the group consisting of aluminum, nickel, stainless steel (SUS), copper, iron, bronze, and brass, respectively. , specifically, may be made of aluminum, or stainless steel (SUS), and more specifically, may be made of stainless steel (SUS).

Depending on the type of material used as the electrolyte, these metals are highly corrosive, so that their lifespan characteristics are deteriorated, and they can no longer be used, or safety may be threatened.

Accordingly, in the present invention, in the coin-type secondary battery in which the first case, the second case, the spring, and the spacer are made of metal, the first case, the second case, the spring, and the spacer are disposed on the surface in contact with the electrolyte. It is characterized in that by forming an anti-corrosion layer, corrosion by the electrolyte is prevented.

Meanwhile, the coin-type secondary battery may further include a gasket sealing the first case and the second case.

Since the gasket is generally made of an insulating material, it is not necessary to form an anti-corrosion layer. However, an anti-corrosion layer may be formed on the surface of the gasket, and this structure is not excluded.

In the present invention, a perspective view of a coin-type secondary battery having such a corrosion-preventing layer is shown in FIG. 1 below, and a schematic cross-section is shown in FIG. 2 .

1 and 2 together, the coin-type secondary battery 100 of the present application includes an electrode assembly 110, a first case 120 accommodating the electrode assembly 110; a second case 130 assembled to cover the upper end of the first case 120 ; and a spring 160 and a spacer 170 filling an inner space excluding the electrode assembly in the first case and the second case.

At this time, the electrode assembly 110 includes a positive electrode 111, a negative electrode 112, and a separator 113 interposed between the positive electrode 111 and the negative electrode 112, in this case, the positive electrode 111, The negative electrode 112 and the separator 113 have a coin-shaped structure.

Meanwhile, since the first case 120 , the second case 130 , the spring 160 , and the spacer 170 are made of metal, in order to prevent corrosion due to the reaction with the electrolyte, the surface in contact with the electrolyte Corrosion prevention layers 151, 152, 153, and 154 made of one selected from the group consisting of a primer layer, a conductive polymer layer, and a conductive epoxy layer are respectively formed thereon.

Meanwhile, the coin-type secondary battery 100 may further include a gasket 140 sealing the first case 120 and the second case 130 .

The anti-corrosion layer may be formed to a thickness of 0.01 μm to 100 μm, specifically 0.5 μm to 30 μm, and more specifically, 1 μm to 10 μm.

Outside of the above range, if it is too thin, it is not possible to exhibit a sufficient anti-corrosion effect, and if it is too thick, conductivity may be deteriorated or bulk energy density may be lowered, which is not preferable.

In addition, the corrosion-resistant layers 151 , 152 , 153 , and 154 are conductive materials, considering that the cases, springs, and spacers of the coin-type secondary battery are made of metal, and these themselves serve as electrode terminals. It is preferable to include In particular, when the corrosion-preventing layers 151 , 152 , 153 , and 154 are formed entirely on the inner surface of the case, securing conductivity is a very important problem as much as corrosion prevention. Even if corrosion is prevented, if the conductivity is not sufficiently secured, the performance as a secondary battery is eventually deteriorated, and thus the meaning of the invention is inevitably reduced.

Accordingly, the corrosion protection layers 151 , 152 , 153 , and 154 may be formed of one selected from the group consisting of a primer layer, a conductive polymer layer, and a conductive epoxy layer.

In this case, the primer layer may include graphene as a carbon-based material rather than a general carbon material, and further may further include a binder polymer.

When the graphene is used, compared to the case where other carbon-based materials are used, superior conductivity may be exhibited. According to the present invention, since securing conductivity is an important element in a coin-type secondary battery, it is essential to ensure sufficient conductivity. It is important to use

The binder polymer is used for bonding between the first case 120, the second case 130, the spring 160, and the spacer 170 made of metal and the primer layer, and is not limited as long as it has a general binding component. No, for example, polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene , polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene butyrene rubber, and may be at least one selected from the group consisting of fluororubber.

In this case, the graphene and the binder polymer may be included in a weight ratio of 1:99 to 99:1, specifically 3:7 to 7:3 by weight.

Outside the above range, when the content of graphene is small, sufficient conductivity cannot be obtained, and conversely, when the content of the binder polymer is too small, sufficient binding force of the primer layer cannot be obtained, which is not preferable.

Such a primer layer can use a coating film forming method commonly used in the art, for example, gravure (gravure) coating, slot die (slot die) coating, spin coating, spray coating, bar coating, dip coating and The same wet coating method or a dry coating method such as thermal evaporation, E-beam evaporation, Chemical Vapor Deposition, or sputtering may be used.

For the conductive polymer layer, polymers commonly known as conductive polymers may be used, for example, polyethylenedioxythiophene/polystyrenesulfonate (PEDOT/PSS; poly(3,4-ethylenedioxythiophene)/poly(4-styrene) sulfonate), polyaniline (PANI; polyaniline), polypyrrole (PPy; polypyrrole), polythiophene (PT; polythiophene), polyacetylene (PA; polyacetylene), polypara-phenylene vinylene (PPV; poly para-phenylene vinylene) It may include one or more conductive polymers selected from the group consisting of.

The conductive polymer layer may be formed by preparing a conductive polymer melt or a mixed solution dissolving them in a solvent, and performing various wet coating methods as described in the primer layer coating method. In this case, when the conductive polymer is mixed with a solvent, the solvent may be a polar organic solvent, for example, chloroform, dichloromethane, m-cresol, tetrahydrofuran (THF), and dimethylformamide (DMF). and the like.

On the other hand, since the conductive polymer itself exerts binding force, a separate binding material is not required.

However, for stronger binding, the same binder polymer as disclosed in the primer layer may be additionally included, and in this case, the content may be included in an amount of 0.1 to 10% by weight based on the total weight of the conductive polymer layer.

The conductive epoxy layer may include a conductive filler and an epoxy polymer.

Here, the conductive filler may be at least one selected from the group consisting of gold, platinum, silver, copper, or nickel metal powder, carbon or carbon fiber, graphite, and composite powder.

The epoxy polymer is a component for binding the conductive filler, but is not limited, for example, acrylic, epoxy, polyurethane, silicone, polyimide, phenolic, polyester polymer material, composite polymer resin and It may be at least one selected from the group consisting of low-melting glass.

On the other hand, the conductive epoxy layer may be classified into a room temperature drying type, a room temperature curing type, a heat curing type, a high temperature firing type, a UV curing type, and the like, depending on how it is manufactured.

The room temperature drying type can be formed by including a conductive filler in an acrylic polymer and a solvent such as an acrylic polymer and drying at room temperature, and the room temperature curing type is a two-component type, further comprising a highly reactive curing agent, a conductive filler and It can be formed by curing a solvent containing an epoxy polymer.

In addition, the thermosetting type mainly uses an epoxy-based epoxy polymer and can be formed by applying heat to a solvent containing a conductive filler. can be formed by

In this case, the conductive filler and the epoxy polymer may also be included in a weight ratio of 1:99 to 99:1, specifically 7:3 to 3:7 by weight.

Outside the above range, when too little conductive filler is included, conductivity is lowered and resistance is increased, and when too little epoxy polymer is included, binding force of conductive filler cannot be obtained, which is not preferable.

On the other hand, the anti-corrosion layer is more preferably a configuration that can effectively prevent corrosion by an electrolyte solution even after long-term use while having excellent conductivity, and specifically, it may be a conductive polymer layer or a conductive epoxy layer.

Meanwhile, the positive electrode 111 has a coin-shaped structure including a positive electrode active material layer 111b formed on one surface of the positive electrode current collector 111a.

Like the positive electrode 111 , the negative electrode 112 also has a coin-shaped structure including a negative electrode active material layer 112b formed on one surface of the negative electrode current collector 112a.

Since the types and structures of the current collectors used for the positive and negative electrodes, the positive electrode active material, the negative electrode active material, other conductive materials, binders, separators, electrolytes, and the like are known in the prior art, a detailed description thereof will be omitted in the present application.

However, the electrolyte contains a non-aqueous electrolyte and a lithium salt, and the coin-type secondary battery according to the present invention is more effective when a lithium imide-based salt is used as the lithium salt.

The lithium imide-based salt is lithium bis (fluorosulfonyl) imide (Lithium bis (fluorosulfonyl) imide), lithium bis (trifluoromethanesulfonyl) imide (Lithium bis (trifluoromethanesulfonyl) imide) or lithium bis (purple) Luoroethylsulfonyl)imide may be used, and preferably, the lithium imide-based salt is lithium bis(fluorosulfonyl)imide or lithium bis(trifluoromethanesulfonyl)imide. de is

Hereinafter, preferred examples of the present invention, comparative examples and experimental examples for evaluating them will be described. However, it is obvious to those skilled in the art that various changes and modifications are possible within the scope and spirit of the present description only by illustrating the present description, and it is natural that such modifications and modifications belong to the appended claims. will be.

<Preparation Example 1> (Primer layer precursor solution)

As a conductive material, 10 g of graphene was added to 200 g of NMP solvent, and then dispersed by applying an H-NBR dispersant, and 5 g of PVdF was mixed as a binder to prepare a primer layer precursor solution.

<Preparation Example 2> (Primer layer precursor solution)

As a conductive material, 10 g of natural graphite was added to 200 g of NMP solvent, then H-NBR dispersant was applied to disperse it, and 5 g of PVdF was mixed as a binder to prepare a primer layer precursor solution.

<Preparation Example 3> (Primer layer precursor solution)

As a conductive material, 10 g of acetylene black was added to 200 g of NMP solvent, then H-NBR dispersant was applied to disperse it, and 5 g of PVdF was mixed as a binder to prepare a primer layer precursor solution.

<Preparation Example 4> (Conductive polymer layer precursor solution)

As a conductive polymer, 10 g of polypyrrole was mixed with 100 g of solvent dimethylformamide (DMF) and stirred (40 °C) for 48 hours with a magnetic bar to prepare a conductive polymer layer precursor solution.

<Preparation Example 5> (Conductive Epoxy Layer Precursor Solution)

8331S product (a silver-containing two-component electrically conductive epoxy adhesive) from MG chemicals was used.

<Example 1>

As a coin-type battery case, the primer layer precursor solution prepared in Preparation Example 1 is coated on the surface where the first case, the second case, the spring, and the spacer can contact the electrolyte as shown in FIG. 1 below (spray) coated). The positive electrode active material (LiNi _0.6 Co _0.2 Mn _0.2 O ₂ ) 95% by weight, Super-P (conductive material) 2.5% by weight, and PVDF (binder) 2.5% by weight of the positive electrode mixture as a solvent NMP (N-methyl-2) -pyrrolidone) was added to prepare a positive electrode slurry, and then coated (100 μm) on an aluminum current collector substrate to prepare a coin-shaped positive electrode.

An anode slurry was prepared by adding an anode mixture of 95 wt% artificial graphite, 2.5 wt% Super-P (conductive material), and 2.5 wt% PVDF (binder) to NMP (N-methyl-2-pyrrolidone) as a solvent. After that, a coin-shaped negative electrode was prepared by coating (100 μm) on a copper current collector substrate.

An electrode assembly is prepared by interposing a polyethylene-based separator between the prepared positive electrode and the negative electrode, and the electrode assembly is embedded in the coin-shaped case as shown in FIG. 1 below, and 1 M LiFSI is dissolved in a volume ratio of 1:1 Ethylene carbonate (EC) and dimethyl carbonate (DMC) solutions were injected as electrolytes, and then sealed with a gasket to prepare a coin-type secondary battery.

<Example 2>

Example 1, except that the conductive polymer layer precursor solution prepared in Preparation Example 4 was coated on the surface where the coin-shaped first case, the second case, the spring, and the spacer can contact the electrolyte in Example 1 A coin-type secondary battery was manufactured in the same manner as described above.

<Example 3>

Example 1 except that the conductive epoxy layer precursor solution prepared in Preparation Example 5 was coated on the surface where the coin-shaped first case, the second case, the spring, and the spacer in Example 1 can contact the electrolyte A coin-type secondary battery was manufactured in the same manner as described above.

<Comparative Example 1>

The same as in Example 1, except that the primer layer precursor solution prepared in Preparation Example 2 was coated on the surface where the coin-shaped first case, the second case, the spring, and the spacer in Example 1 can contact the electrolyte. Similarly, a coin-type secondary battery was manufactured.

<Comparative Example 2>

The same as in Example 1, except that the primer layer precursor solution prepared in Preparation Example 3 was coated on the surface where the coin-shaped first case, the second case, the spring, and the spacer in Example 1 can contact the electrolyte. Similarly, a coin-type secondary battery was manufactured.

<Comparative Example 3>

A coin-type secondary battery was prepared in the same manner as in Example 1, except that in Example 1, no coating was applied to the surface where the coin-type first case, the second case, the spring, and the spacer could come into contact with the electrolyte. prepared.

<Experimental Example 1>

The coin cell batteries prepared in Examples 1 to 3 and Comparative Examples 1 to 3 were charged and discharged 100 times under the following conditions, and then the discharge capacity retention rate was calculated 100 times compared to the discharge capacity at one time, and the results are shown in Table 1 below. indicated.

Charge: 0.3C, CC/CV, 4.25V, 1/20C cut-off

Discharge: 0.3C, CC, 3.0V, cut-off

100 capacity retention rate (%) Example 1 99 Example 2 96 Example 3 99 Comparative Example 1 95 Comparative Example 2 97 Comparative Example 3 62

Referring to Table 1, it can be seen that when the corrosion prevention layer is formed according to the present invention, it exhibits superior lifespan characteristics compared to Comparative Example 3 in which no action is taken.

<Experimental Example 2>

The rate evaluation was performed on the coin cell batteries prepared in Example 1 and Comparative Examples 1 and 2 under the following conditions.

[1 to 3 ^rd cycle charge/discharge conditions]

Charge: 0.1C, CC/CV, 4.25V, 1/20C cut-off

Discharge: 0.1C, CC, 3.0V, cut-off

[4 to 6 ^th cycle charge/discharge conditions]

Charge: 0.1C, CC/CV, 4.25V, 1/20C cut-off

Discharge: 2C, CC, 3.0 V, cut-off

The capacity retention ratio of the 2C average discharge capacity value obtained in the 4th to 6th cycle compared to the 0.1C average discharge capacity value obtained in the initial 3 times of charging and discharging was calculated, and the results are shown in Table 2 below.

2C discharge capacity retention rate (%) Example 1 89 Comparative Example 1 60 Comparative Example 2 75

Referring to Table 2, when the primer layer containing a conductive material other than graphene is coated according to Comparative Examples 1 and 2, corrosion of the metal in Experimental Example 1 can be prevented, so that although the lifespan characteristics are excellent, Compared with the case of using a pin, it can be confirmed that the conductivity is reduced by the coating, which is not preferable because the rate characteristic is lowered.

Those of ordinary skill in the art to which the present invention pertains will be able to make various applications and modifications within the scope of the present invention based on the above content.

Claims (7)

a coin-shaped electrode assembly including an anode, a cathode, and a separator interposed between the anode and the cathode;
a first case for accommodating the electrode assembly;
a second case covering the upper end of the first case; and
a spring and a spacer filling an inner space excluding the electrode assembly in the first case and the second case; including,
The first case, the second case, the spring, and the spacer are made of metal,
A corrosion prevention layer made of one selected from the group consisting of a primer layer, a conductive polymer layer, and a conductive epoxy layer is formed on the surface of the first case, the second case, the spring, and the spacer in contact with the electrolyte,
The primer layer is a coin-type secondary battery comprising graphene. According to claim 1,
The metal is a coin-type secondary battery made of any one selected from the group consisting of aluminum, nickel, stainless steel (SUS), copper, iron, bronze, and brass. According to claim 1,
The coin-type secondary battery further includes a gasket sealing the first case and the second case. According to claim 1,
The anti-corrosion layer is a coin-type secondary battery formed to a thickness of 0.01 ㎛ to 100 ㎛. According to claim 1,
The primer layer is a coin-type secondary battery further comprising a binder polymer. According to claim 1,
The conductive polymer layer is polyethylenedioxythiophene/polystyrenesulfonate (PEDOT/PSS; poly(3,4-ethylenedioxythiophene)/poly(4-styrene sulfonate), polyaniline (PANI; polyaniline), polypyrrole (PPy; polypyrrole), poly Coin-type secondary battery comprising at least one conductive polymer selected from the group consisting of thiophene (PT; polythiophene), polyacetylene (PA; polyacetylene), and poly para-phenylene vinylene (PPV) . According to claim 1,
The conductive epoxy layer is a coin-type containing one or more conductive fillers selected from the group consisting of gold, platinum, silver, copper, or nickel metal powder, carbon or carbon fiber, graphite, and composite powder, and an epoxy polymer. secondary battery.

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