WO2022097833A1 - Polymer binder suitable for silicon-based and carbon-based negative electrode material for lithium secondary battery and method for manufacturing same - Google Patents

Abstract

The present invention is an invention that is carried out with support from a business provided by Gyeongbuk Technopark foundation (business name "Regulation Free Special Zone Innovation Project (Commercialization Support) Special Zone Business Support", project name "Regulation Free Special Zone Battery Recycling Commercialization Support"). Specifically, the present invention relates to a polymer binder, wherein two or more polymers are formed through crosslinkage, and the crosslinkage comprises an ester linkage. The polymer binder consists of two or more polymers which are formed through crosslinkage, and has conductivity and restorative elasticity. In addition, the polymer binder is manufactured to include copper, thereby having high conductivity.

Description

Polymer binder suitable for silicon-based and carbon-based negative electrode materials for lithium secondary batteries and manufacturing method thereof

The present invention relates to a polymer binder for a lithium secondary battery and a method for manufacturing the same. When two or more kinds of water-based polymers are crosslinked to increase elasticity, when applied to a lithium secondary battery, the recovery ability of the negative electrode active material is improved. In addition, it is possible to improve the charging/discharging efficiency and lifespan characteristics of the lithium secondary battery by suppressing contraction and expansion of silicon while improving adhesion through strong interaction with silicon and carbon used in the negative electrode active material.

With the rapid development of the electronics, communication and computer industries, camcorders, mobile phones, notebook PCs, etc. are making remarkable progress, and high energy density and stable output of batteries are required as power sources to drive portable electronic devices. At the same time, an inexpensive and simple process in terms of productivity is also required. Among these batteries, the lithium ion battery is most actively developed and is widely applied to portable electronic devices.

The theoretical capacity of silicon is 4,200 mAh/g, which is the highest among materials applicable to the negative electrode of a lithium-ion battery. Silicon has advantages of high output and low price, but there is a problem in that a phase change occurs due to the reverse insertion and separation of lithium ions, and thus the volume expands by more than 300%. As a result, the stress inside the silicon causes cracks, which causes the structure to collapse. This structural collapse of the silicon blocks electron transfer in the electrode, resulting in an unusable space in the electrode, resulting in a decrease in the capacity and lifespan of the silicon.

On the other hand, the binder used when manufacturing the electrode used in the lithium secondary battery has been limited to the role of bonding the electrode active material and the current collector.

Korean Patent Application Laid-Open No. 10-2017-0033123 discloses that a method for producing a polymer binder is cross-linked and decomposed by a solvent. When cross-linked and decomposed by a solvent, air pollution may occur to process the solvent, and the remaining solvent may cause a chemical reaction to deteriorate the performance of the secondary battery.

[Prior art literature]

[Patent Literature]

(Patent Document 0001) Patent Publication No. KR 10-2017-0033123

The present application is intended to solve the problems of the prior art described above, and when two or more types of water-based polymers are formed by cross-linking to increase recovery elasticity, when applied to a negative active material for a secondary battery, silicon expansion and contraction prevents particle detachment And it is possible to achieve the effect of improving the lifespan of the secondary battery.

In the polymer binder of the present invention for achieving the above technical problem, two or more types of polymers are crosslinked, and the crosslinked includes an ester bond.

The polymer may include a polymer selected from the group consisting of polyacrylic acid, polyvinyl alcohol, polyvinyl acrylic acid, polyamide, polyvinylithene, polyamideimide, polyethylene, polypropylene, and combinations thereof, However, the present invention is not limited thereto.

The polymer binder may be one in which polyacrylic acid and polyvinyl alcohol are crosslinked, but is not limited thereto.

The polymer binder may be one represented by the following Chemical Formula 1 or Chemical Formula 2, but is not limited thereto.

[Formula 1]

[Formula 2]

In Formulas 1 and 2, n ₁ , n ₂ and m are each independently an integer of 10 to 10,000.

It may further include copper ions, but is not limited thereto.

The manufacturing method of the polymer binder of the present application comprises the steps of preparing a mixture by mixing two or more types of polymers, citric acid and glycerol; and reacting the mixture to form a crosslink.

The mixture may further include a copper compound, but is not limited thereto.

The reaction may be carried out at a temperature of 30°C to 200°C for 1 hour to 6 hours, but is not limited thereto.

In 100 parts by weight of the mixture, 60 parts by weight to 95 parts by weight of the polymer, 3 parts by weight to 20 parts by weight of the citric acid, and 3 parts by weight to 20 parts by weight of the glycerol may be mixed, but is not limited thereto.

The polymer may include a polymer selected from the group consisting of polyacrylic acid, polyvinyl alcohol, polyvinyl acrylic acid, polyamide, polyvinylithene, polyamideimide, polyethylene, polypropylene, and combinations thereof, However, the present invention is not limited thereto.

The copper compound may include a material selected from the group consisting of Cu(CH ₂ COO) ₂ , CuCl ₂ , Cu(NO ₃ ) ₂ , CuSO _{4 ,} CuSO ₄ ·5H ₂ O, and combinations thereof, However, the present invention is not limited thereto.

The cross-linking may include an ester bond, but is not limited thereto.

The lithium secondary battery of the present application includes the polymer binder.

The above-described problem solving means are merely exemplary, and should not be construed as limiting the present application. In addition to the exemplary embodiments described above, additional embodiments may exist in the drawings and detailed description.

The disclosed technology may have the following effects. However, this does not mean that a specific embodiment should include all of the following effects or only the following effects, so the scope of the disclosed technology should not be understood as being limited thereby.

According to the above-described problem solving means of the present application, the polymer binder according to the present application is made of two or more polymers cross-linked, so that expansion and contraction are freely possible, so that it can serve as a "smart ball". The smart ball can help in shrinking the silicon to its original shape after expansion when a voltage is applied by applying the negative active material for a lithium secondary battery to a lithium secondary battery. Since the smart ball is not only expandable but also contracted freely, the characteristics of the lithium secondary battery are reversible, so that the coulombic efficiency, periodicity, charge/discharge rate, lifespan, etc. can be improved.

In addition, since the polymer binder uses a water-based polymer, water may be used as a solvent. Since a chemical solvent is used to prepare a conventional polymer binder, a process for removing the solvent and contamination may occur, and the solvent is not completely removed, so that when applied to a lithium secondary battery, a chemical reaction occurs continuously and the lithium This may cause deterioration of the performance of the secondary battery. However, since the polymer binder of the present application uses water, an additional process for removing a separate solvent is not required.

1 is a flowchart of a method for manufacturing a polymer binder according to an embodiment of the present application.

Since the present invention can have various changes and can have various embodiments, specific embodiments are illustrated in the drawings and will be described in detail in the detailed description. However, this is not intended to limit the present invention to specific embodiments, and it should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention.

In describing each figure, like reference numerals are used for like elements. Terms such as first, second, etc. may be used to describe various elements, but the elements should not be limited by the terms. The above terms are used only for the purpose of distinguishing one component from another.

For example, without departing from the scope of the present invention, a first component may be referred to as a second component, and similarly, a second component may also be referred to as a first component. The term “and/or” includes a combination of a plurality of related listed items or any of a plurality of related listed items.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

Terms such as those defined in a commonly used dictionary should be interpreted as having a meaning consistent with the meaning in the context of the related art, and should not be interpreted in an ideal or excessively formal meaning unless explicitly defined in the present application. shouldn't

Throughout this specification, when a member is positioned “on”, “on”, “on”, “on”, “under”, “under”, or “under” another member, this means that a member is positioned on the other member. It includes not only the case where they are in contact, but also the case where another member exists between two members.

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

As used herein, the terms "about," "substantially," and the like are used in a sense at or close to the numerical value when the manufacturing and material tolerances inherent in the stated meaning are presented, and to aid in the understanding of the present application. It is used to prevent an unconscionable infringer from using the mentioned disclosure in an unreasonable way. Also, throughout this specification, "step to" or "step to" does not mean "step for".

Throughout this specification, the term "combination of these" included in the expression of the Markush form means one or more mixtures or combinations selected from the group consisting of the components described in the expression of the Markush form, and the components It is meant to include one or more selected from the group consisting of.

Hereinafter, the polymer binder for a lithium secondary battery of the present application and a method for manufacturing the same will be described in detail with reference to embodiments, examples, and drawings. However, the present application is not limited to these embodiments and examples and drawings.

The present application relates to a polymer binder in which two or more polymers are cross-linked, and the cross-linkage includes an ester bond.

The polymer binder may be one in which two or more types of polymers are crosslinked and have conductivity and restorative elasticity, but is not limited thereto.

The polymer binder may include an ester bond generated by cross-linking between polymers having a carboxyl group and a hydroxyl group.

The polymer binder has high mechanical resistance and recoverable deformability due to deformation.

The polymer binder is composed of two or more polymers cross-linked so that expansion and contraction are freely possible, thereby serving as a “smart ball”.

The smart ball can help in shrinking the silicon to its original shape after expansion when a voltage is applied by applying the negative active material for a lithium secondary battery to a lithium secondary battery. Conventionally, only research has been conducted to suppress the expansion of silicon used in lithium secondary batteries. However, in this case, when the silicone is expanded, it cannot shrink to its original shape and thus may exhibit irreversible characteristics. The present application has applied a smart ball to solve this problem, and since the smart ball is not only expandable but also contracted freely, the characteristics of the lithium secondary battery are reversible, so that the coulombic efficiency, periodicity, charge/discharge rate, lifespan, etc. can be improved. In addition, the electrical contact between the anode active materials for a lithium secondary battery is improved, so that destruction and detachment due to excessive expansion can be prevented.

Furthermore, since the polymer binder has conductivity, it is possible to improve the efficiency of the lithium secondary battery.

In addition, the polymer binder can be commercially manufactured at a low cost, so it is easy to reduce the cost of the process.

Moreover, the conventionally used polymer binder is a material used when manufacturing an electrode used in a lithium secondary battery, and only serves to allow the active material, the conductive material, and the current collector to adhere well to each other. On the other hand, the polymer binder of the present application may simultaneously perform a role of suppressing expansion of the anode active material and improving conductivity as well as an adhesion role.

The polymer binder may include a polymer selected from the group consisting of polyacrylic acid, polyvinyl alcohol, polyvinyl acrylic acid, polyamide, polyvinylithene, polyamideimide, polyethylene, polypropylene, and combinations thereof. , but is not limited thereto.

Since the polymer binder uses an aqueous polymer, water may be used as a solvent. Since a chemical solvent is used to prepare a conventional polymer binder, a process for removing the solvent and contamination may occur, and the solvent is not completely removed, so that when applied to a lithium secondary battery, a chemical reaction occurs continuously and the lithium This may cause deterioration of the performance of the secondary battery. However, since the polymer binder of the present application uses water, an additional process for removing a separate solvent is not required.

The polymer binder may be one in which polyacrylic acid and polyvinyl alcohol are crosslinked, but is not limited thereto.

In 100 parts by weight of the polymer binder, 60 to 95 parts by weight of the polyacrylic acid and 5 to 40 parts by weight of the polyvinyl alcohol may be included.

The polymer binder may be one represented by the following Chemical Formula 1 or Chemical Formula 2, but is not limited thereto.

In Formulas 1 and 2, n ₁ , n ₂ and m are each independently an integer of 10 to 10,000.

It may further include copper ions, but is not limited thereto.

The polymer binder may have increased electrical conductivity by further including the copper ions.

By including the copper ions, electrical conductivity is improved, and when the polymer binder is applied to a lithium secondary battery, the capacity may be increased.

The present application includes the steps of preparing a mixture by mixing two or more types of polymers, citric acid and glycerol; and reacting the mixture to form a cross-linkage.

1 is a flowchart of a method for manufacturing a polymer binder according to an embodiment of the present application.

First, a mixture is prepared by mixing two or more polymers, citric acid and glycerol (S100).

The polymer may include a polymer selected from the group consisting of polyacrylic acid, polyvinyl alcohol, polyvinyl acrylic acid, polyamide, polyvinylithene, polyamideimide, polyethylene, polypropylene, and combinations thereof, However, the present invention is not limited thereto.

The polymer may have a concentration of 2 wt% to 50 wt% when water is used as a solvent.

The polymer binder may be a smart ball (gel) having a repair ability by chemically crosslinking two or more kinds of water-based binders having a carboxyl group and a hydroxyl group capable of strongly bonding with the silicone.

The cross-linking may include an ester bond, but is not limited thereto.

The mixture may further include a copper compound, but is not limited thereto.

The copper compound may include a material selected from the group consisting of Cu(CH ₂ COO) ₂ , CuCl ₂ , Cu(NO ₃ ) ₂ , CuSO _{4 ,} CuSO ₄ ·5H ₂ O, and combinations thereof, However, the present invention is not limited thereto.

In 100 parts by weight of the mixture, 60 parts by weight to 95 parts by weight of the polymer, 3 parts by weight to 20 parts by weight of the citric acid, and 3 parts by weight to 20 parts by weight of the glycerol may be mixed, but is not limited thereto.

In 100 parts by weight of the mixture, 3 to 10 parts by weight of the copper compound may be mixed, but is not limited thereto.

Then, the mixture is reacted to form a cross-link (S200).

The reaction may be carried out at a temperature of 30°C to 200°C for 1 hour to 6 hours, but is not limited thereto.

When the reaction temperature is less than 30° C. and the reaction time is less than 1 hour, the crosslinking may not be sufficiently achieved.

The present application relates to a lithium secondary battery including the polymer binder.

Since the lithium secondary battery includes the polymer binder, coulombic efficiency periodicity, charge/discharge rate, lifespan, etc. may be improved.

The present invention will be described in more detail through the following examples, but the following examples are for illustrative purposes only and are not intended to limit the scope of the present application.

[Example 1]

First, the solid polymer PVA was mixed with deionized water at a ratio of 2:8 and stirred at room temperature with RPM150 for 1 hour prior to preparation.

Then, the solid polymer PAA was mixed with deionized water at a ratio of 2:8 and stirred at room temperature with RPM150 for 1 hour prior to preparation.

Then, citric acid: copper compound was prepared by mixing 8:2.

A polymer binder was prepared by mixing the PVA, PAA, citric acid and copper compound in a ratio of 1:8:1 and reacting at a temperature of 150° C. for 2 hours.

[evaluation]

The adhesive force of the polymer binder prepared in Example 1 with the current collector was measured, and the results are shown in Table 1 below.

The polymer binder of Example 1 was applied and dried on a copper foil film to obtain a polymer binder film. After the polymer binder film was cut at intervals of 5 mm, a 180° peel test was performed to measure the adhesive force between the polymer and the copper foil.

polymer binder	Adhesion (gf/mm)
Example 1	14.8
PVDF	0.9
PAA	10.4

According to the results shown in Table 1, it can be confirmed that the adhesive strength is excellent when compared with the industrial binders PVDF and PAA.

Cohesion force of the polymer binder prepared in Example 1 with the negative electrode active material was tested. A uniform slurry was prepared by mixing the polymer binder of Example 1 and the Si-C mixed slurry of the negative electrode active material with deionized water at a weight ratio of 2:8. The slurry was coated on a copper foil film, dried and rolled to obtain a negative electrode. After cutting the obtained negative electrode at intervals of 1 cm, a 180° peel test was performed using a commercially available tape, and the results are shown in Table 2 below.

polymer binder	Adhesion (gf/mm)
Example 1	1,237
PVDF	207
PAA	916

According to the results shown in Table 2, it can be confirmed that the polymer binder of Example 1 has better binding force with the negative electrode active material, compared to PVDF and PAA, which are industrial binders.

The electrical conductivity of the polymer binder prepared in Example 1 was measured, and the results are shown in Table 3 below. To measure the conductivity, the binder was applied to a thickness of 10 μm on a release paper, dried to obtain a binder film, and conductivity was measured using an E.C (electro conductivity) measuring device.

polymer binder	Conductivity (Ω.M)
Example 1	3.47 x 10 -2
PVDF	1.62 x 10 -2
PAA	1.01 x 10 -6

According to the results shown in Table 3, it can be confirmed that the polymer binder of Example 1 has the highest conductivity as compared to PVDF and PAA, which are industrial binders.

Conductivity was measured when the polymer binder prepared in Example 1 was applied to the negative electrode, and the results are shown in Table 4 below. A uniform slurry was prepared by mixing the polymer binder of Example 1 and the Si-C mixed slurry of the negative electrode active material with deionized water at a weight ratio of 2:8. The slurry was coated on a copper foil film, dried and rolled to obtain a negative electrode. The conductivity of the negative electrode was measured using an electro conductivity (EC) measuring instrument.

polymer binder	Conductivity (Ω.M)
Example 1	4.79x 10 -2
PVDF	2.84 x 10 -2
PAA	1.61 x 10 -4

According to the results shown in Table 4, it can be confirmed that the conductivity is the highest when the polymer binder of Example 1 is applied to the negative electrode, compared to PVDF and PAA, which are industrial binders.

The foregoing description of the present application is for illustration, and those of ordinary skill in the art to which the present application pertains will understand that it can be easily modified into other specific forms without changing the technical spirit or essential features of the present application. Therefore, it should be understood that the embodiments described above are illustrative in all respects and not restrictive. For example, each component described as a single type may be implemented in a dispersed form, and likewise components described as distributed may be implemented in a combined form.

The scope of the present application is indicated by the following claims rather than the above detailed description, and all changes or modifications derived from the meaning and scope of the claims and their equivalent concepts should be construed as being included in the scope of the present application.

Claims (13)

1. Two or more types of polymers are cross-linked, and the cross-linked polymer binder includes an ester bond.
2. The method of claim 1,

   The polymer is a polymer binder that contains a polymer selected from the group consisting of polyacrylic acid, polyvinyl alcohol, polyvinyl acrylic acid, polyamide, polyvinylithene, polyamideimide, polyethylene, polypropylene, and combinations thereof. . .
3. 3. The method of claim 2,

   The polymer binder is a polymer binder that consists of polyacrylic acid and polyvinyl alcohol cross-linked.
4. The method of claim 1,

   The polymer binder is a polymer binder represented by the following Chemical Formula 1 or Chemical Formula 2:

   [Formula 1]

   

   [Formula 2]

   

   In Formulas 1 and 2,

   The n ₁ , n ₂ and m are each independently an integer of 10 to 10,000.
5. The method of claim 1,

   A polymer binder that further comprises copper ions.
6. preparing a mixture by mixing two or more types of polymers, citric acid and glycerol; and

   A method of producing a polymer binder, including; forming a crosslink by reacting the mixture.
7. 7. The method of claim 6,

   The mixture further comprises a copper compound, the method for producing a polymer binder.
8. 7. The method of claim 6,

   The reaction is carried out for 1 hour to 6 hours at a temperature of 30 ℃ to 200 ℃, the method for producing a polymer binder.
9. 7. The method of claim 6,

   In 100 parts by weight of the mixture, 60 parts by weight to 95 parts by weight of the polymer, 3 parts by weight to 20 parts by weight of the citric acid, and 3 parts by weight to 20 parts by weight of the glycerol are mixed.
10. 7. The method of claim 6,

    The polymer is a polymer binder that contains a polymer selected from the group consisting of polyacrylic acid, polyvinyl alcohol, polyvinyl acrylic acid, polyamide, polyvinylithene, polyamideimide, polyethylene, polypropylene, and combinations thereof. manufacturing method.
11. 8. The method of claim 7,

    The copper compound is Cu(CH ₂ COO) ₂ , CuCl ₂ , Cu(NO ₃ ) ₂ , CuSO ₄ , CuSO ₄ ·5H ₂ O, and a polymer binder comprising a material selected from the group consisting of combinations thereof manufacturing method.
12. 7. The method of claim 6,

    The cross-linking is a method for producing a polymer binder comprising an ester bond.
13. A lithium secondary battery comprising the polymer binder according to any one of claims 1 to 5.

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