KR101491062B1 - A separator and electrochemical device including the same - Google Patents

Abstract

The present invention discloses a separator and an electrochemical device including the separator. A separator according to the present invention comprises: a first porous substrate having a melting point of 150 ° C or higher; A second porous substrate formed on an upper surface of the first porous substrate and having a melting point lower than 120 캜; And a porous coating layer formed on the upper surface of the second porous substrate and including inorganic particles and a binder polymer.
According to the present invention, the safety of the electrochemical device is improved due to the presence of the porous coating layer having inorganic particles, and a porous substrate having a relatively low melting point is positioned between the porous substrate and the porous coating layer having a relatively high melting point, The porous substrate in the intermediate layer serves as a resistor when the chemical element generates heat, thereby improving the safety of the electrochemical device and improving the output of the electrochemical device by including the porous substrate having a relatively high melting point.

Description

[0001] The present invention relates to a separator and an electrochemical device including the same,

The present invention relates to a separator used in an electrochemical device such as a lithium secondary battery, and an electrochemical device including the separator. More particularly, the present invention relates to a separator having a porous coating layer formed on a porous substrate and an electrochemical device including the separator.

Recently, interest in energy storage technology is increasing. As the application fields of cell phones, camcorders, notebook PCs and even electric vehicles are expanding, efforts for research and development of electrochemical devices are becoming more and more specified. The electrochemical device has received the most attention in this respect. Of these, the development of a rechargeable secondary battery has become a focus of attention. Recently, in developing such a battery, Research and development on the design of electrodes and batteries are underway.

Among the currently applied secondary batteries, the lithium secondary battery developed in the early 1990s has advantages such as higher operating voltage and higher energy density than conventional batteries such as Ni-MH, Ni-Cd and sulfuric acid-lead batteries using an aqueous electrolyte solution .

Such electrochemical devices are produced in many companies, but their safety characteristics are different. It is very important to evaluate the safety and safety of such an electrochemical device. The most important consideration is that the electrochemical device should not injure the user in case of malfunction. For this purpose, the safety standard strictly regulates the ignition and fuming in the electrochemical device. In the safety characteristics of the electrochemical device, there is a high possibility that the electrochemical device is overheated and thermal explosion occurs or an explosion occurs when the separator is penetrated. Particularly, the polyolefin-based porous substrate commonly used as a separator of an electrochemical device exhibits extreme heat shrinkage behavior at a temperature of 100 ° C or more owing to the characteristics of the manufacturing process including material properties and elongation, . ≪ / RTI >

In order to solve the safety problem of such an electrochemical device, a separator in which a porous coating layer is formed by coating a mixture of inorganic particles and a binder polymer on at least one surface of a porous substrate having a plurality of pores has been proposed. In such a separator, the inorganic particles in the porous coating layer formed on the porous substrate serve as a kind of spacer capable of maintaining the physical form of the porous coating layer, thereby suppressing heat shrinkage of the porous substrate upon overheating of the electrochemical device, Thereby preventing direct contact between the cathode and the anode even when the substrate is damaged.

On the other hand, when a polypropylene based material having a relatively high melting point is used as the porous base material, there is a problem that the output of the electrochemical device is improved but the safety is lowered as compared with the case of using the polyethylene based material. Use of a low-polyethylene-based material has a problem in that the safety is improved as compared with the case of using a polypropylene-based material, but the output of the electrochemical device is lowered.

Accordingly, it is an object of the present invention to provide a separator which improves the output of an electrochemical device and improves safety, and an electrochemical device including the same.

According to an aspect of the present invention, there is provided a porous substrate comprising: a first porous substrate having a melting point of 150 ° C or higher; A second porous substrate formed on an upper surface of the first porous substrate and having a melting point lower than 120 캜; And a porous coating layer formed on the upper surface of the second porous substrate, the porous coating layer comprising inorganic particles and a binder polymer.

The first porous substrate may be at least one selected from the group consisting of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polyester, polyacetal, polyimide, polyamide, polyamideimide, polycarbonate, polyetheretherketone, polyaryletherketone , Polyvinylidene fluoride, and copolymers comprising at least two repeating units thereof; Polyester-based elastomer; And a polyamide-based elastomer; or a mixture of two or more thereof.

The second porous substrate may be any one selected from the group consisting of ultra low density polyethylene, low density polyethylene, linear low density polyethylene, metallocene polyethylene, olefin block copolymer (OBC) and polyolefin elastomer Or a mixture of two or more of them.

The diameter of the first inorganic particles may be 0.1 탆 to 10.0 탆.

The binder polymer may be at least one selected from the group consisting of polyvinylidene fluoride-co-hexafluoro propylene, polyvinylidene fluoride-co-trichlorethylene, But are not limited to, polymethyl methacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, polyethylene-co-vinyl acetate, polyethylene oxide oxide, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethylpullulan, cyanoethylpolyvinylalcohol, Cyanoethylcellulose, cyano One selected from the group consisting of cyanoethylsucrose, pullulan, carboxyl methyl cellulose, acrylonitrile-styrene-butadiene copolymer, and polyimide. Or a mixture of two or more thereof.

The separator may further include a binder layer on at least one surface thereof.

The thickness of the binder layer may be 0.1 mu m to 3.0 mu m.

According to another aspect of the present invention, there is provided an electrochemical device comprising a cathode, an anode, a separator interposed between the cathode and the anode, and a non-aqueous electrolyte, wherein the separator is a separator of the present invention .

Here, the electrochemical device may be a lithium secondary battery.

According to one embodiment of the present invention, the safety of the electrochemical device is improved due to the presence of the porous coating layer comprising inorganic particles, and a porous substrate having a relatively low melting point is formed between the porous substrate and the porous substrate, And the porous substrate in the intermediate layer acts as a resistor when the electrochemical device generates heat, thereby further improving the safety of the electrochemical device.

At the same time, by including a porous substrate having a relatively high melting point, it improves the output of the electrochemical device.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate exemplary embodiments of the invention and, together with the description of the invention, It should not be construed as limited.
1 is a view showing a separator according to an embodiment of the present invention.
2 is a view showing a separator further comprising a binder layer on one surface of a porous coating layer according to another embodiment of the present invention.
3 is a view illustrating a separator further comprising a binder layer on one surface of a first porous substrate according to another embodiment of the present invention.
4 is a view showing a separator further comprising a binder layer on one surface of the porous coating layer and on one surface of the first porous substrate according to another embodiment of the present invention.

Hereinafter, the present invention will be described in detail. The terms and words used in the present specification and claims should not be construed as limited to ordinary or dictionary terms and the inventor may appropriately define the concept of the term in order to best describe its invention It should be construed as meaning and concept consistent with the technical idea of the present invention. Therefore, the constitution described in the embodiments described herein is merely the most preferred embodiment of the present invention, and does not represent all the technical ideas of the present invention, so that various equivalents And variations are possible.

1 is a view showing a separator according to an embodiment of the present invention.

1, a separator 100 according to the present invention includes a first porous substrate 20 having a melting point of 150 ° C or higher; A second porous substrate (10) formed on an upper surface of the first porous substrate (20) and having a melting point lower than 120 캜; And a porous coating layer 30 formed on the upper surface of the second porous substrate 10 and including inorganic particles 31 and a binder polymer 32. The stability of the electrochemical device is improved due to the presence of the porous coating layer 30 having the inorganic particles 31 and the porous coating layer 30 having a relatively high melting point is formed between the first porous substrate 20 and the porous coating layer 30, The second porous substrate 10 having a relatively low point is located and the second porous substrate 10 in the intermediate layer during the heat generation of the electrochemical device serves as a resistance body to further improve the safety of the electrochemical device, By including the first porous substrate 20 having a relatively high point, the output of the electrochemical device is improved.

The first porous substrate may be at least one selected from the group consisting of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polyester, polyacetal, polyimide, polyamide, polyamideimide, polycarbonate, polyetheretherketone, polyaryletherketone , Polyvinylidene fluoride, and copolymers comprising two or more of these repeating units; Polyester-based elastomer; And a polyamide-based elastomer, or a mixture of two or more thereof, and the second porous substrate may be composed of an ultra-low density polyethylene, a low density polyethylene, a linear low density polyethylene, a metallocene polyethylene, an olefin An olefin block copolymer (OBC) and a polyolefin elastomer, or a mixture of two or more thereof.

The ultra low density polyethylene, low density polyethylene, linear low density polyethylene, metallocene polyethylene, olefin block copolymer (OBC) and polyolefin elastomer used in the present invention are not particularly limited as long as the melting point is less than 120 캜.

The thicknesses of the first porous substrate and the second porous substrate are not particularly limited, but are 1 탆 to 100 탆, or 5 탆 to 50 탆.

Also, the pore size and porosity present in the first porous substrate and the second porous substrate are not particularly limited, but may be 0.001 μm to 50 μm and 20% to 80%, respectively.

The diameter of the inorganic particles is not particularly limited, but may be, for example, 0.1 to 10 μm or 0.2 to 5.0 μm for forming a porous coating layer having a uniform thickness and a proper porosity.

The inorganic particles usable in the present invention are not particularly limited as long as they are electrochemically stable. That is, the inorganic particles usable in the present invention are not particularly limited as long as oxidation and / or reduction reaction does not occur in the operating voltage range of the applied electrochemical device (for example, 0 to 5 V based on Li / Li ⁺ ). Particularly, when inorganic particles having a high dielectric constant are used as the inorganic particles, the dissociation of the electrolyte salt, for example, the lithium salt in the liquid electrolyte, can be increased, and the ion conductivity of the electrolyte can be improved.

The binder polymer may be at least one selected from the group consisting of polyvinylidene fluoride-co-hexafluoro propylene, polyvinylidene fluoride-co-trichlorethylene, But are not limited to, polymethyl methacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, polyethylene-co-vinyl acetate, polyethylene oxide oxide, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethylpullulan, cyanoethylpolyvinylalcohol, Cyanoethylcellulose, cyano One selected from the group consisting of cyanoethylsucrose, pullulan, carboxyl methyl cellulose, acrylonitrile-styrene-butadiene copolymer, and polyimide. Or a mixture of two or more of them, but the present invention is not limited thereto.

A separator according to an embodiment of the present invention comprises: preparing a first porous substrate having a plane melting point of 150 ° C or higher having pores; Forming a second porous substrate having a melting point lower than 120 캜 on an upper surface of the first porous substrate; Coating a slurry containing inorganic particles, a binder polymer, and a solvent on the upper surface of the second porous substrate to form a porous coating layer.

The first porous substrate and the second porous substrate may be independently fabricated by a dry method or a wet method, and then they may be laminated to each other by a lamination method.

The method of forming the porous coating layer using the slurry is not particularly limited as long as it is a conventional coating method in the art. For example, a dip coating, a die coating, a roll coating, a comma (comma ) Coating.

The solvent contained in the coated slurry may be dried according to a method commonly used in the art.

The drying method of the solvent may be carried out batchwise or continuously using an oven or a heating chamber at a temperature range condition considering the vapor pressure of the solvent used.

Here, the solvent used in the present invention is not particularly limited as long as the inorganic particles are dispersed while dissolving the binder polymer and the solvent is capable of dissolving the binder polymer, but it may be more advantageous that the boiling point is low. This is to facilitate subsequent solvent removal. Non-limiting examples of usable solvents include acetone, tetrahydrofuran, methylene chloride, chloroform, dimethylformamide, N-methyl-2-pyrrolidone, cyclohexane, water or mixtures thereof.

The content of the binder polymer is not particularly limited, but may be 3 to 35 parts by weight, or 5 to 25 parts by weight based on 100 parts by weight of the solvent. When the content of the binder polymer satisfies the above range, adhesion of the separator to the electrode is improved, and the viscosity of the slurry is appropriately controlled, so that the handling in the manufacturing process can be made easier.

2 to 4 are views showing a separator further comprising a binder layer according to another embodiment of the present invention.

2 to 4, a binder layer 40 may be further formed on one surface of the porous coating layer 30, and a binder layer 50 may be further formed on one surface of the first porous substrate 20 And may further include a binder layer 40 or 50 on one surface of the first porous substrate 20 and on one surface of the porous coating layer 30.

The binder layer may be made of the same material as the above-mentioned binder polymer, and the thickness of the binder layer may be 0.1 to 3.0 mu m or 0.2 to 2.0 mu m.

By further including the binder layer, adhesion of the electrochemical device to the electrode is improved to facilitate manufacture of the electrochemical device. By satisfying the numerical range, it is possible to easily manufacture the electrochemical device without degrading the performance of the electrochemical device do.

At this time, the binder layer may be formed on at least one surface of the separator by coating a binder layer slurry in which a binder polymer and a solvent are mixed.

On the other hand, the electrochemical device according to the present invention includes a cathode, an anode, a separator interposed between the cathode and the anode, and a non-aqueous electrolyte, wherein the separator is the separator of the present invention described above.

The electrochemical device of the present invention includes all devices that perform an electrochemical reaction, and specific examples thereof include capacitors such as all kinds of primary, secondary cells, fuel cells, solar cells, or super-capacitor devices . Particularly, a lithium secondary battery including a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery, or a lithium ion polymer secondary battery is preferable.

The electrode to be applied to the electrochemical device according to the present invention is not particularly limited, and the electrode active material may be bound to an electrode current collector according to a conventional method known in the art. Examples of the cathode active material include, but are not limited to, lithium manganese oxide, lithium cobalt oxide, lithium nickel oxide, lithium iron oxide, or a combination thereof A lithium complex oxide may be used. As a non-limiting example of the anode active material, a conventional anode active material that can be used for an anode of an electrochemical device can be used. In particular, lithium metal or a lithium alloy, carbon, petroleum coke, activated carbon, Lithium-adsorbing materials such as graphite or other carbon-based materials and the like are preferable. Non-limiting examples of the cathode current collector include aluminum, nickel, or a combination thereof, and examples of the anode current collector include copper, gold, nickel, or a copper alloy or a combination thereof Foil to be manufactured, and the like.

The electrolyte salt included in the nonaqueous electrolyte solution which can be used in the present invention is a lithium salt. The lithium salt can be used without limitation as those conventionally used in an electrolyte for a lithium secondary battery. Examples of the anion of the lithium salt include F^-, Cl^-, Br^-, I^-, NO₃ ^-, N (CN)₂ ^-, BF₄ ^-, ClO₄ ^-, PF₆ ^-, (CF₃)₂PF₄ ^-, (CF₃)₃PF₃ ^-, (CF₃)₄PF₂ ^-, (CF₃)₅PF^-, (CF₃)₆P^-, CF₃SO₃ ^-, CF₃CF₂SO₃ ^-, (CF₃SO₂)₂N^-, (FSO₂)₂N^- _,CF₃CF₂(CF₃)₂CO^-, (CF₃SO₂)₂CH^-, (SF₅)₃C^-, (CF₃SO₂)₃C^-, CF₃(CF₂)₇SO₃ ^-, CF₃CO₂ ^-, CH₃CO₂ ^-, SCN^- And (CF₃CF₂SO₂)₂N^-And the like.

Examples of the organic solvent included in the above-mentioned non-aqueous electrolyte include those commonly used in electrolytic solutions for lithium secondary batteries, such as ether, ester, amide, linear carbonate, cyclic carbonate, etc., Can be mixed and used.

Among them, a carbonate compound which is typically a cyclic carbonate, a linear carbonate, or a mixture thereof may be included.

Specific examples of the cyclic carbonate compound include ethylene carbonate (EC), propylene carbonate (PC), 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, Propylene carbonate, 2,3-pentylene carbonate, vinylene carbonate, vinylethylene carbonate, and halides thereof, or a mixture of two or more thereof. Examples of such halides include, but are not limited to, fluoroethylene carbonate (FEC) and the like.

Specific examples of the linear carbonate compound include any one selected from the group consisting of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate, ethyl methyl carbonate (EMC), methyl propyl carbonate and ethyl propyl carbonate And mixtures of two or more of them may be used as typical examples, but the present invention is not limited thereto.

In particular, ethylene carbonate and propylene carbonate, which are cyclic carbonates in the carbonate-based organic solvent, are high-viscosity organic solvents having a high dielectric constant and can dissociate the lithium salt in the electrolyte more easily. In addition, such cyclic carbonates can be used as dimethyl carbonate and diethyl carbonate When a low viscosity, low dielectric constant linear carbonate is mixed in an appropriate ratio, an electrolyte having a higher electric conductivity can be produced.

As the ether in the organic solvent, any one selected from the group consisting of dimethyl ether, diethyl ether, dipropyl ether, methyl ethyl ether, methyl propyl ether and ethyl propyl ether or a mixture of two or more thereof may be used , But is not limited thereto.

Examples of the ester in the organic solvent include methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate,? -Butyrolactone,? -Valerolactone,? -Caprolactone,? -Valerolactone, ε-caprolactone, or a mixture of two or more thereof, but the present invention is not limited thereto.

The injection of the nonaqueous electrolyte solution can be performed at an appropriate stage of the manufacturing process of the electrochemical device according to the manufacturing process and required properties of the final product. That is, it can be applied before assembling the electrochemical device or in the final stage of assembling the electrochemical device.

The electrochemical device according to the present invention is capable of lamination, stacking, and folding processes of a separator and an electrode in addition to a conventional winding process. The outer shape of the electrochemical device is not particularly limited, but may be a cylindrical shape, a square shape, a pouch shape, a coin shape, or the like using a can.

The foregoing description is merely illustrative of the technical idea of the present invention and various changes and modifications may be made by those skilled in the art without departing from the essential characteristics of the present invention. Therefore, the embodiments disclosed in the present invention are intended to illustrate rather than limit the scope of the present invention, and the scope of the technical idea of the present invention is not limited by these embodiments. The scope of protection of the present invention should be construed according to the following claims, and all technical ideas within the scope of equivalents should be construed as falling within the scope of the present invention.

Example

Example  1-1. Separator  Produce

(1) Preparation of slurry

Alumina as inorganic particles, polyvinylidene fluoride-hexafluoropropylene as a binder polymer, and acetone as a solvent at a weight ratio of 25.5: 4.5: 70.0 to prepare a slurry.

(2) Production of separator

A first porous substrate made of polypropylene having a thickness of 8 탆 and a melting point of 165 캜 was prepared and a second porous substrate made of a low density polyethylene having a thickness of 8 탆 and a melting point of 115 캜 was formed on the first porous substrate by a lamination method .

The prepared slurry was coated on the upper surface of the second porous substrate by a slot coating method to form a porous coating layer to prepare a separator.

Example  1-2. Separator  Produce

A slurry was prepared by mixing polyvinylidene fluoride-hexafluoropropylene as a binder polymer and acetone as a solvent at a weight ratio of 10:90, and the slurry was coated on the porous coating layer by a roll coating method to form a binder layer , A separator was produced in the same manner as in Example 1-1.

Example  2-1. Manufacture of electrochemical device (lithium secondary battery)

(1) Manufacture of cathode

90 parts by weight of a lithium cobalt composite oxide as cathode active material particles, 5 parts by weight of carbon black as a conductive material and 5 parts by weight of PVDF as a binder were added to 40 parts by weight of N-methyl-2-pyrrolidone (NMP) A cathode active material slurry was prepared. The cathode active material slurry was applied to an aluminum (Al) thin film of a cathode current collector having a thickness of 100 탆 and dried to produce a cathode, followed by roll pressing.

(2) Manufacture of anode

95 parts by weight, 2 parts by weight and 3 parts by weight, respectively, of a carbon powder as an anode active material, polyvinylidene fluoride (PVdF) as a binder and carbon black as a conductive material were dissolved in a solvent N-methyl- Was added to 100 parts by weight of NMP to prepare an anode active material slurry. The anode active material slurry was coated on a copper (Cu) thin film as an anode current collector having a thickness of 90 탆 and dried to produce an anode, followed by roll pressing.

(3) Production of lithium secondary battery

The unit cells were assembled by the stacking method using the cathode, the anode and the separator manufactured by the above-described method. Then, an electrolyte (ethylene carbonate (EC) / propylene carbonate (PC) / diethyl carbonate (DEC) = 3/2/5 (volume ratio)) was injected to produce a lithium secondary battery.

Example  2-2

A lithium secondary battery was produced in the same manner as in Example 2-1, except that the separator manufactured in Example 1-2 was used as the separator.

Comparative Example  One. Separator  Produce

A separator was produced in the same manner as in Example 1, except that the polypropylene material having a porous base material of 16 占 퐉 and a melting point of 165 占 폚 was used alone.

Comparative Example  2. Manufacture of lithium secondary battery

A lithium secondary battery was produced in the same manner as in Example 2-1 except that the separator prepared in Comparative Example 1 was used.

Characteristic evaluation 1- Separator  Safety experiment

The separator prepared in Example 1-1 and Comparative Example 1 was impregnated with an electrolytic solution and the ion conductivity according to the temperature was measured. In the case of the separator fabricated in Example 1-1, the resistance increased sharply at 130 ° C to prevent further lithium ion transfer, whereas in the case of the separator fabricated in Comparative Example 1, the same effect occurred only after the temperature was raised to 170 ° C I could confirm.

Characteristic evaluation 2-ignition test of lithium secondary battery

The lithium secondary batteries manufactured in Examples 2-1 and 2-2 and Comparative Example 2 were placed in a 55 ° C chamber and the nails having a diameter of 3 mm were passed at a rate of 8 cm / sec to compare the safety, The lithium secondary battery manufactured in 2-1 and 2-2 did not continue to ignite even after passing through the nail, whereas the lithium secondary battery of Comparative Example 2 ignited in 15 minutes after the nail penetration.

10: Second porous substrate
20: First porous substrate
30: Porous coating layer
31: inorganic particles
32: binder polymer
40, 50: binder layer

Claims (9)

A first porous substrate having a melting point of 150 ° C or higher;
A second porous substrate formed on an upper surface of the first porous substrate and having a melting point lower than 120 캜; And
And a porous coating layer formed on an upper surface of the second porous substrate, the porous coating layer having inorganic particles and a binder polymer, the porous coating layer suppressing heat shrinkage of the first porous substrate or the second porous substrate. The method according to claim 1,
Wherein the first porous substrate is selected from the group consisting of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polyester, polyacetal, polyimide, polyamide, polyamideimide, polycarbonate, polyetheretherketone, polyaryletherketone, poly Vinylidene fluoride and copolymers comprising two or more of these repeating units; Polyester-based elastomer; And a polyamide-based elastomer; or a mixture of two or more thereof. The method according to claim 1,
The second porous substrate is characterized in that it is formed of any one selected from the group consisting of ultra low density polyethylene, low density polyethylene, linear low density polyethylene, metallocene polyethylene, olefin block copolymer and polyethylene elastomer, or a mixture of two or more thereof . The method according to claim 1,
Wherein the inorganic particles have a diameter of 0.1 to 10.0 占 퐉. The method according to claim 1,
The binder polymer may be at least one selected from the group consisting of polyvinylidene fluoride-co-hexafluoro propylene, polyvinylidene fluoride-co-trichlorethylene, But are not limited to, polymethyl methacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, polyethylene-co-vinyl acetate, polyethylene oxide, Cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethylpullulan, cyanoethylpolyvinylalcohol, cyanoethylpolyvinylalcohol, Ethylcellulose, cyanoethylcellulose, One selected from the group consisting of cyanoethylsucrose, pullulan, carboxyl methyl cellulose, acrylonitrile-styrene-butadiene copolymer and polyimide. Or a mixture of two or more thereof. The method according to claim 1,
Wherein the separator further comprises a binder layer on at least one surface of the separator. The method according to claim 6,
Wherein the thickness of the binder layer is 0.1 to 3.0 占 퐉. An electrochemical device comprising a cathode, an anode, a separator interposed between the cathode and the anode, and a non-aqueous electrolyte,
Wherein the separator is the separator according to any one of claims 1 to 7. 9. The method of claim 8,
Wherein the electrochemical device is a lithium secondary battery.

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