KR101631847B1 - Anode slurry for lithium-ion battery, and method for fabricating thereof - Google Patents

Abstract

Disclosure of Invention Technical Problem [8] The present invention relates to a method for preventing the reduction of battery life due to volume expansion and shrinkage due to charge / discharge while using a silicon-based anode mix, and to prevent sedimentation, thereby uniformly distributing the anode mixture to the cathode and decreasing the sintering temperature The present invention provides a binder for a lithium ion secondary battery having improved adhesion properties, an excellent recovery rate, and an excellent stiffness, which is improved compared to conventional binders, and a lithium ion secondary battery having the same. The binder for a lithium ion secondary battery comprises a carboxylic acid (-COOH) and a synthetic binder chemically synthesized from a second binder containing an amine (NR3, wherein R is hydrogen, alkyne, alkane). According to the present invention, The use of a negative electrode mixture containing silicon suppresses the volume expansion and contraction caused by charge and discharge It prevents the decrease of the life of life and prevents sedimentation of solids caused by the use of some binders, uniformly distributing the negative electrode mixture to the electrodes, uniformly forming the electrode density, and improving the manufacturing process characteristics by reducing the sintering temperature of the negative electrode mixture And has excellent adhesion, excellent recovery rate, and excellent rigidity as compared with the conventional binder, thereby greatly improving the performance of the lithium ion secondary battery.

Description

TECHNICAL FIELD The present invention relates to an anode mixture for a lithium ion secondary battery, and a method for manufacturing the same. BACKGROUND ART [0002]

The present invention relates to a negative electrode material for a lithium ion secondary battery and a method for manufacturing the same. More specifically, the present invention relates to a positive electrode material for a lithium ion secondary battery, which prevents or suppresses separation due to volume expansion and contraction of a negative electrode material for a negative electrode of a lithium ion secondary battery, To an anode mixture for a lithium ion secondary battery that improves process characteristics while realizing an electrode density, and a method for manufacturing the same.

Lithium ion secondary batteries are one of the energy storage devices that store energy.

The lithium ion secondary battery has a higher energy density than the nickel cadmium battery, has no memory effect, is environmentally friendly, has a long life cycle, can output a high voltage, and can be miniaturized Recently, it is widely used in small portable electronic products such as mobile phones, tablet PCs and camcorders.

Conventional lithium ion secondary batteries include a positive electrode, a negative electrode, a separator, and an electrolytic solution as main components.

Conventionally, a cathode of a lithium ion secondary battery includes lithium oxide, and a cathode includes a carbon compound such as graphite capable of storing lithium ions. The separator prevents direct contact between the anode and the cathode, And serves as a medium for allowing lithium ions to move.

Recently, a technique for increasing the reversible capacity of a lithium ion secondary battery by changing a negative electrode material of a lithium ion secondary battery from a carbon-based material to a silicon-based material has been studied.

However, when the anode material of the lithium ion secondary battery is changed from the carbon material to the silicon material, the reversible capacity of the lithium ion secondary battery having a silicon-based negative electrode can be greatly increased. On the other hand, Deterioration of the electrode due to volume expansion and contraction of the material, and peeling of the binder of the silicon-based material from the negative electrode, thereby significantly shortening the battery life.

In order to solve the problem caused by employing the silicon-based negative electrode of such a lithium ion secondary battery, Korean Unexamined Patent Publication No. 2007-0110569, published on November 20, 2007, discloses a binder containing polyacrylic acid physically mixed with polyurethane And a lithium secondary battery based thereon disclose a binder in which polyurethane is physically mixed with polyacrylic acid.

In order to solve the problems caused by employing a silicon-based negative electrode of a lithium ion secondary battery, Korean Unexamined Patent Publication No. 2014-0012464, published on Feb. 3, 2014, a silicon alloy based negative electrode active material, an anode active material composition containing the same, A manufacturing method thereof and a technique in which an organic binder including a polyamideimide is used for a lithium secondary battery are disclosed.

When a negative electrode material mixture is prepared by using a binder, a silicon-based active material, a conductive material, and a solvent having polyacrylic acid as a binder of a silicon-based negative electrode of a lithium ion secondary battery, the solubility of a solid component including a silicon-based active material, And when the negative electrode mixture having the settling phenomenon is applied to the negative electrode, the electrode density of the negative electrode becomes uneven.

On the other hand, when a negative electrode mixture containing a polyamideimide, a silicone-based active material, a conductive material and a solvent is used as a binder of a silicon-based negative electrode of a lithium ion secondary battery, the sintering temperature of the negative electrode mixture containing polyamideimide Which is very high as compared with the negative electrode material mixture.

Korean Patent Publication No. 2007-0110569, an electrode mixture containing polyacrylic acid physically mixed with polyurethane as a binder, and a lithium secondary battery based thereon (2007. 11. 20) Korean Unexamined Patent Publication No. 2014-0012464, a silicon alloy-based negative electrode active material, a negative electrode active material composition containing the same, a manufacturing method thereof, and a lithium secondary battery (Apr.

Disclosure of Invention Technical Problem [8] The present invention relates to a method for preventing the reduction of battery life due to volume expansion and shrinkage due to charge / discharge while using a silicon-based anode mix, and to prevent sedimentation, thereby uniformly distributing the anode mixture to the cathode and decreasing the sintering temperature To provide an anode mixture for a lithium ion secondary battery having improved adhesion, excellent recovery and excellent rigidity compared to conventional binders, and a method for producing the same.

In one embodiment, the binder for a lithium ion secondary battery is formed by chemically synthesizing a first binder containing a carboxylic acid (-COOH) and a second binder containing an amine (NR3, wherein R is hydrogen, alkyne, alkane) And a synthetic binder.

The first binder of the binder for a lithium ion secondary battery includes polyacrylic acid (PAA), and the second binder includes poly (amide imide) (PAI).

The synthetic binder of the binder for a lithium ion secondary battery contains an amide (C (O) -NR) group as a functional group.

In one embodiment, a method for producing a binder for a lithium ion secondary battery includes dissolving a first binder containing a carboxylic acid (-COOH) in a solvent, adding an amine (NR3, only R Providing a second binder comprising hydrogen, alkyne, alkane, and a reaction inducing agent for inducing a reaction of the first and second binders to the solvent to synthesize a synthetic binder.

In the method for producing a binder for a lithium ion secondary battery, the reaction inducing agent includes sulfuric acid, the solvent includes water, and the step of synthesizing the synthetic binder includes refluxing the first binder, the second binder, reflux conditions for 24 hours, and the ratio of the first binder, the second binder and the reaction inducing agent is 1: 1: 0.02.

A lithium ion secondary battery includes a positive electrode coated with a positive electrode mixture containing a positive electrode active material, a conductive agent and a binder on a positive electrode, a negative electrode coated with a negative electrode mixture mixed with a negative electrode active material, a conductive agent, and a binder on the negative electrode, A separator for separating the anode and the cathode, and an electrolyte for ion transfer between the anode and the cathode, wherein the binder contained in the cathode mixture comprises a first binder containing carboxylic acid (-COOH) , Provided that R is hydrogen, alkyne, alkane). The present invention also relates to a synthetic binder obtained by chemically synthesizing a second binder.

Wherein the first binder of the lithium ion secondary battery comprises polyacrylic acid (PAA), and the second binder includes polyamide (amide imide) (PAI) (C (O) -NR) group as a functional group.

INDUSTRIAL APPLICABILITY The negative electrode material mixture for a lithium ion secondary battery and the method for manufacturing the same according to the present invention can prevent the reduction of the battery life by suppressing the volume expansion and contraction due to charging and discharging caused by using the negative electrode material mixture containing silicon in order to increase the capacity, It is possible to prevent the settling phenomenon of solids from occurring when using some binders, uniformly distribute the negative electrode mixture to the electrode to uniformly form the electrode density, to reduce the sintering temperature of the negative electrode mixture to improve the manufacturing process characteristics, , Excellent recovery rate, and excellent rigidity, thereby greatly improving the performance of the lithium ion secondary battery.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view showing a synthetic binder obtained by synthesizing a first binder, a second binder, and first and second binders constituting a synthetic binder according to an embodiment of the present invention.
FIG. 2 is a flow chart showing a process of manufacturing the synthetic binder shown in FIG. 1. FIG.
3 is a graph showing the functional groups of the synthetic binder by FT-IR analysis of the synthetic binder shown in Fig.
4 is a graph showing 13 C-NMR (nuclear magnetic resonance) analysis of the synthetic binder shown in Fig.
FIG. 5 is a graph showing the binding force of a binder including a synthetic binder, a binder containing polyacrylic acid, and a binder containing polyamide imide according to an embodiment of the present invention.
6A is a graph showing the recovery rate and the stiffness after forming a negative electrode mixture containing a binder, a binder containing polyacrylic acid (PAA), and a binder containing polyamide amide (PAI) on the electrode.
FIG. 6B is a graph showing the recovery rates of the binders of FIG. 6A.
6C is a graph showing the rigidity of each binder.
FIG. 7 is a cross-sectional view conceptually showing a lithium ion secondary battery including a negative electrode coated with a negative electrode mixture containing the synthetic binder shown in FIG. 1;
8 is a graph showing the electrochemical evaluation results of a lithium ion secondary battery including the synthetic binder of FIG.

In the following description, only parts necessary for understanding the embodiments of the present invention will be described, and the description of other parts will be omitted so as not to obscure the gist of the present invention.

The terms and words used in the present specification and claims should not be construed as limited to ordinary or dictionary meanings and the inventor is not limited to the meaning of the terms in order to describe his invention in the best way. It should be interpreted as meaning and concept consistent with the technical idea of the present invention. Therefore, the embodiments described in the present specification and the configurations shown in the drawings are merely preferred embodiments of the present invention, and are not intended to represent all of the technical ideas of the present invention, so that various equivalents And variations are possible.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view showing a synthetic binder obtained by synthesizing a first binder, a second binder, and first and second binders constituting a synthetic binder according to an embodiment of the present invention.

Referring to FIG. 1, a synthetic binder (PAA-PAI) 300 is formed by synthesizing a first binder 100 and a second binder 200.

The synthetic binder 300 according to one embodiment of the present invention may be included in a negative electrode mixture formed on the negative electrode of a lithium ion secondary battery, for example.

The negative electrode material mixture may include an active material including silicon and graphite, a conductive agent for increasing the conductivity of the active material, a solvent, and a synthetic binder.

The first binder 100 for synthesizing the composite binder 300 may be a material containing a carboxylic acid (-COOH) as shown in FIG. 1, for example, the first binder 100 may be a poly Acrylic acid (PAA).

Polyacrylic acid (PAA) which is the first binder 100 suppresses the volume expansion and contraction caused by silicon (Si) contained in the negative electrode mixture formed in the negative electrode of the lithium ion secondary battery, Thereby preventing it from being desorbed.

On the other hand, the first binder 100 has the advantage of preventing volume expansion and contraction of the negative electrode mixture and preventing peeling or separation of the negative electrode mixture from the negative electrode, and has an advantage that the negative electrode mixture can be sintered at a low temperature 1 binder 100 has the disadvantage that the active material contained in the negative electrode mixture and the conductive agent are easily precipitated in the solvent and it is difficult to realize a uniform electrode density.

The second binder 200 for synthesizing the composite binder 300 comprises an amine (NR3, where R is hydrogen, alkyne, alkane) as shown in Figure 1, and in an embodiment of the present invention, The binder 200 may comprise, for example, poly (amide imide) (PAI).

Since the second binder 200 for synthesizing the synthetic binder 300 has excellent sedimentation preventing property compared to polyacrylic acid (PAA) which is the first binder 100, the uniform electrode density of the negative electrode mixture formed on the negative electrode can be realized .

However, in order to apply the negative electrode mixture containing polyamide imide (PAI), which is the second binder 200 for synthesizing the synthetic binder 300, to the negative electrode of the lithium ion secondary battery, the negative electrode mixture maintains a constant strength Since the second binder 200 containing polyamide imide (PAI) requires a high sintering temperature of about 300 DEG C or more, the electrode density of the anode mix including the second binder 200 is formed to be very uniform Despite its advantages, it has a disadvantage that fairness is not very good.

In one embodiment of the present invention, a polyacrylic acid (PAA) which is a first binder 100 containing carboxylic acid and a synthetic binder (PAI) which is a composite of polyamideimide (PAI) which is a second binder 200 containing amine The advantages of the first binder 100 and the second binder 200 are maintained through the first binder 100 and the second binder 200. The drawbacks of the first and second binders 100 and 200 are that the composite binder PAI- The present invention is applied to a negative electrode of a battery to prevent the negative electrode mixture from being separated and separated from the negative electrode according to volume expansion and contraction caused by charging and discharging. The active material and the conductive agent are uniformly distributed in the negative electrode mixture, And the sintering temperature is reduced to improve the processability.

In particular, in one embodiment of the present invention, the synthetic binder 300 formed by synthesizing the first binder 100 and the second binder 200 includes an amide (C (O) -NR) group as a functional group.

The amide (C (O) -NR) group, which is a functional group formed in the synthetic binder 300, is a compound in which the synthetic binder 300 comprises a first binder 100 comprising polyacrylic acid (PAA) and a polyamide imide So that excellent binding force, recovery rate, rigidity, improved sedimentation characteristics, and improved physical properties can be exhibited compared to the second binder 200.

FIG. 2 is a flow chart showing a process of manufacturing the synthetic binder shown in FIG. 1. FIG.

1 and 2, in order to produce the synthetic binder 300, a step of dissolving the first binder 100 in water as a solvent is performed (step S10)

For example, in order to produce the synthetic binder 300, polyacrylic acid (PAA), for example, the first binder 100, is dissolved in water as a solvent.

After dissolving the first binder 100 in water as a solvent, the second binder 200 is provided to the solution in which the first binder 100 is dissolved (step S20)

In addition, stirring is performed for 24 hours under a reflux condition in which a reaction inducing agent is added to induce a reaction period of the first binder 100 and the second binder 200 (Step S30). In an example, the reaction inducing agent may be, for example, sulfuric acid.

In one embodiment of the present invention, the ratio of the first binder 100, the second binder 200, and the reaction inducing agent may be 1: 1: 0.02. For example, when the first binder 100 is about 5 [g], the second binder 200 may be about 5 [g] and the reaction inducing agent may be about 0.1 [g].

After the first binder 100, the second binder 200 and the reaction inducing agent are dissolved in water and stirred to produce the synthetic binder 300, unreacted first and second unreacted components The second binders 100 and 200 are removed from the synthetic binder 300 by filtration through filtration and the remaining water is also removed by using a pressurized distillation apparatus.

Subsequently, a small amount of impurities which can be formed during the synthesis of the first and second binders 100 and 200 are removed by decantation a plurality of times with ethyl acetate and diethyl ether. Step S50)

Thereafter, the unreacted first and second binders (100, 200), water and remaining synthetic binder remaining after the impurities are removed are dried under vacuum for 24 hours to prepare a synthetic binder 300 (Step S60)

3 is a graph showing the functional groups of the synthetic binder by FT-IR analysis of the synthetic binder shown in Fig.

1 and 3, polyacrylic acid (PAA) which is the first binder 100 and polyamide imide (PAI) which is the second binder 200 are laminated on the synthetic binder 300 The synthetic binder 300 was found to be a mixture of the polyacrylic acid (PAA) and the second binder (B) contained in the first binder 100, which is the starting material, as a result of the chemical structure analysis of the synthetic binder 300 by FT- (PAI) of about 1705 cm ^-1 , and an absorption peak of about 1705 cm ^-1 is observed at about 1705 cm ^-1 in the analysis graph of the synthetic binder 300. As a result, (C (O) -NR), which is a functional group generated in the synthetic binder 300, is an absorption peak not observed in the first binder 100 and the second binder 200, .

4 is a graph showing 13 C-NMR (nuclear magnetic resonance) analysis of the synthetic binder shown in Fig.

1 and 4, 13 C-NMR (nuclear magnetic resonance) analysis of the synthetic binder 300 shows that amide (C (O) -NR), a functional group newly introduced into the synthetic binder 300, Is observed at about 178 ppm which means the carbon of the amide formed through polymerization of polyacrylic acid (PAA) which is the first binder 100 and polyamide imide (PAI) which is the second binder 200 (C (O) -NR) functional group is successfully formed on the synthesized binder 300 synthesized by polymerizing the first binder 100 and the second binder 200.

FIG. 5 is a graph showing the binding force of a binder including a synthetic binder, a binder containing polyacrylic acid, and a binder containing polyamide imide according to an embodiment of the present invention.

1 and 5, a synthetic binder 300 synthesized by polymerizing first and second binders 100 and 200 according to an embodiment of the present invention, a binder containing polyacrylic acid (PAA), and a polyamide imide (PAI) binder were tested as follows.

First, a synthetic binder 300, a binder containing polyacrylic acid (PAA) and a binder containing polyamide imide (PAI) according to an embodiment of the present invention are prepared, and then an active material and a conductive agent are mixed A negative electrode material mixture (active material: binder: conductive agent = 8: 1: 1) was prepared. The negative electrode material mixture was fixed on a slide glass, and a double-faced tape was disposed on the top surface of the negative electrode material mixture. (PAA) and the negative electrode mixture containing polyamide imide (PAI) were observed in the case of the negative electrode mixture containing the polyacrylic acid (PAA).

6A is a graph showing the recovery rate and the stiffness after forming a negative electrode mixture containing a binder, a binder containing polyacrylic acid (PAA), and a binder containing polyamide amide (PAI) on the electrode. FIG. 6B is a graph showing the recovery rates of the binders of FIG. 6A. 6C is a graph showing the rigidity of each binder.

Referring to FIGS. 1 and 6A to 6C, after the preparation of the electrode according to the binder, the recovery rate and stiffness of the negative electrode mixture using the microindentor were evaluated. As a result, a force of about 10 mN was applied to the electrode including the negative electrode mixture, Measure the rigidity, which is the depression depth.

Then, the recovery rate and the stiffness of the negative electrode mixture according to the binder are analyzed by measuring the recovery rate, which is the recovery rate of the negative electrode mixture, after removing the force of about 10 mN.

The binder containing polyacrylic acid (PAA) exhibits the advantages of stiffness with a relatively small depth at which the electrode is pressed but has a low recovery rate. The polyamide imide (PAI) has a relatively low stiffness and excellent recovery Respectively.

In the case of the composite binder 300 having both the characteristics of the two binders, the recovery rate is about 35.1% higher than that of the conventional binder containing polyacrylic acid (PAA) or polyamide imide (PAI) (PAI), because the rigidity of the binder containing polyamide imide (PAI) was improved compared to that of the binder containing polyacrylic acid (PAA). do.

Hereinafter, the results of the measurement of the solid content change rate after the experiment of storing the binder at room temperature will be described with reference to [Table 1].

Polyacrylic acid binder Polyamide imide binder Synthetic binder Settled solid content (%) 20.0 1.3 3.5

In general, the sedimentation characteristics of a solid active material, a binder, and a conductive material in a negative electrode material mixture containing a binder, an active material, a conductive material, and a solvent are very important factors for determining the electrode density. The active material, the binder and the conductive material, It is not possible to obtain a uniform electrode density, so that the performance of the lithium ion secondary battery is largely deteriorated, which greatly affects the mass productivity of the binder, and the sedimentation property of the negative electrode mixture is determined by the characteristics of the binder.

[Table 1] Referring to Table 1, in the case of the negative electrode mixture containing polyacrylic acid binder, the sedimentation solid content is 20%, and in the case of the polyacrylic acid binder, the solid content is precipitated deeply in the molten material.

The negative electrode mixture containing a polyamide imide (PAI) binder has a sedimentation solids content of 1.3%, and the polyamide imide (PAI) binder has a characteristic that sedimentation occurs very low in the solvent.

On the other hand, in the case of the synthetic binder 300 formed by polymerizing polyacrylic acid (PAA) and polyamide imide (PAI), precipitated solid content is 3.5%, which is somewhat higher than that of polyamideimide (PAI) Settling is low in the solvent compared to the binder.

FIG. 7 is a cross-sectional view conceptually showing a lithium ion secondary battery including a negative electrode coated with a negative electrode mixture containing the synthetic binder shown in FIG. 1;

The lithium ion secondary battery 500 includes a cathode 510, a cathode 520, a separator 530, and an electrolyte 540.

The anode 510 includes an anode electrode 511 and a cathode mixture 515.

The positive electrode mixture 515 includes a positive electrode active material containing lithium oxide, a conductive agent for improving the conductivity of the positive electrode active material, and a binder, and the positive electrode mixture 515 is applied or formed on the surface of the positive electrode 511.

The cathode 520 includes a cathode electrode 521 and a cathode mixture 525.

The negative electrode 521 is spaced apart from the positive electrode 511. The negative electrode mixture 525 is composed of a negative electrode active material mixed with silicon and graphite in a ratio of 3: 7, a conductive agent for improving the conductivity of the negative electrode active material, .

In one embodiment of the present invention, the active material, synthetic binder, and conductive agent included in the negative electrode mixture 525 are prepared at a ratio of 8: 1: 1. The cathode mixture 525 is applied and formed on the surface of the cathode electrode 511. [

The separation membrane 530 has a structure having pores through which the electrolytic solution passes. For example, PE (poly (ethylene) is used as the separation membrane.

The electrolyte solution 540 contains EC: EMC in a ratio of 1: 2, and the electrolyte solution 540 includes 1M LiPF ₆ and 10% F-EC.

In one embodiment of the present invention, the synthetic binder contained in the negative electrode material mixture 525 is formed by chemically synthesizing a first binder 100 containing a carboxylic acid, a second binder containing an amine, .

The first binder 100 comprises, for example, polyacrylic acid (PAA), the second binder 200 comprises, for example, polyamide imide (PAI) C (O) -NR) group.

8 is a graph showing the electrochemical evaluation results of a lithium ion secondary battery including the synthetic binder of FIG.

PAA 1st 50th 100th 150th 200th 250th 300th Capacity (mAh / g) 974.1 675.0 598.2 518.6 451.8 397.6 372.3 Retention rate (%) 100 69.3 61.4 53.2 46.4 40.8 38.2 PAI 1st 50th 100th 150th 200th 250th 300th Capacity (mAh / g) 871.7 640.5 530.8 369.2 299.2 277.6 262.5 Retention rate (%) 100 73.5 60.9 42.4 34.3 31.8 30.1 PAA-PAI 1st 50th 100th 150th 200th 250th 300th Capacity (mAh / g) 1120.9 84.56 742.4 665.2 620.9 574.0 527.1 Retention rate (%) 100 75.4 66.2 59.3 55.4 51.2 47.0

8 and Table 2, the configuration of the lithium ion secondary battery is manufactured in the same manner as in Fig. 7, and the evaluation voltage condition is 1.5 [V] to 0.01 [V] Were evaluated about 300 times.

As a result of the evaluation, the lithium ion secondary battery including the synthesized binder exhibited a capacity of 1120.9 [mAh / g] at the first charge in terms of the storage capacity, and a lithium ion secondary battery including a binder using polyacrylic acid (PAA) (MAh / g) in the case of a lithium ion secondary battery including a binder using polyamide imide (PAI), and a capacity of 871.7 [mAh / g] The lithium ion secondary battery including the binder has the highest capacity.

After carrying out 300 times of charge and discharge, the capacity maintenance ratio of the lithium ion secondary battery including the synthetic binder was about 47%, and the capacity maintenance ratio of about 38.2% in the case of the lithium ion secondary battery including polyacrylic acid (PAA) And a capacity maintenance ratio of about 30.1% in the case of a lithium ion secondary battery including a synthetic binder including polyamide imide. As a result, the lithium ion secondary battery including the synthetic binder has the highest capacity retention rate.

As described above in detail, by using the negative electrode mixture containing silicon to increase the capacity, it is possible to prevent the reduction of the battery life by suppressing the volume expansion and contraction due to the charging and discharging caused by charging and discharging, It is possible to uniformly distribute the negative electrode mixture to the electrode by uniformly distributing the negative electrode mixture and to reduce the sintering temperature of the negative electrode mixture to improve the manufacturing process characteristics and to improve the adhesion strength, Thereby greatly improving the performance of the lithium ion secondary battery.

It should be noted that the embodiments disclosed in the drawings are merely examples of specific examples for the purpose of understanding, and are not intended to limit the scope of the present invention. It will be apparent to those skilled in the art that other modifications based on the technical idea of the present invention are possible in addition to the embodiments disclosed herein.

100 ... first binder 200 ... second binder
300 ... synthetic binder

Claims (8)

An active material including silicon and graphite;
A conductive agent for increasing the conductivity of the active material;
A first binder containing a carboxylic acid (-COOH) and a second binder containing an amine (NR3, wherein R is hydrogen, alkyne, alkane) are polymerized in a ratio of 1: 1 through a reaction inducing agent, A displayed composite binder; And
And a solvent including the active material, the conductive agent, and the synthetic binder,
Wherein the first binder is a polyacrylic acid (PAA) that inhibits volume expansion and contraction caused by the silicon, and the second binder is a polyamide imide resin that prevents sedimentation in the solvent and lowers the sintering temperature Poly (amide imide), PAI)
Wherein the sedimented solid content precipitated in the solvent is 3.5% or less.
[Chemical Formula 1]

delete The method according to claim 1,
Wherein the synthetic binder comprises an amide (C (O) -NR) group as a functional group. Dissolving a first binder containing a carboxylic acid (-COOH) in a solvent, adding an amine (NR3, wherein R is a group of the formula: Hydrogen, alkyne, alkane), and a reaction inducing agent for inducing a reaction of the first and second binders to the solvent and polymerizing to synthesize a synthetic binder; And
Comprising the steps of: mixing an active material containing silicon and graphite, a conductive agent for increasing the conductivity of the active material, and a synthetic binder in a solvent,
Wherein the first binder is polyacrylic acid (PAA), the second binder is poly (amide imide) (PAI), and the synthetic binder is amide (C (O) Lt; / RTI > group)
Wherein the sedimented solid content precipitated in the solvent is 3.5% or less. delete 5. The method of claim 4,
Wherein the first binder, the second binder, and the reaction inducing agent are stirred for 24 hours under reflux conditions in the step of synthesizing the synthetic binder, wherein the reaction inducing agent comprises sulfuric acid and the solvent comprises water , And the ratio of the first binder, the second binder, and the reaction inducing agent is 1: 1: 0.02. delete delete

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