KR20230082858A - Aqueous binder composition for lithium secondary battery having a storage stabililty and a long cycle life - Google Patents

Abstract

The present invention relates to an aqueous binder composition for lithium secondary batteries with excellent storage stability and cycle life. Specifically, the aqueous binder composition for lithium secondary batteries of the present invention is environmentally friendly by using water rather than an organic solvent in manufacturing a polyimide precursor for application as a binder for a negative electrode active material of a lithium secondary battery and suppresses detachment from a current collector due to contraction and expansion of the negative electrode active material layer during repeated charging and discharging of a lithium secondary battery and/or interfacial detachment between negative electrode active material layers, thereby maximizing the discharge capacity and charge/discharge efficiency of lithium secondary batteries. Also, the aqueous binder composition for lithium secondary batteries minimizes shortening of charge/discharge cycle life.

Description

Aqueous binder composition for lithium secondary battery having a storage stability and a long cycle life}

The present invention relates to an aqueous binder composition for a lithium secondary battery having excellent storage stability and cycle life. Specifically, the present invention is environmentally friendly by using water instead of an organic solvent in preparing a polyimide precursor for application as a binder for an anode active material of a lithium secondary battery, and at the same time, it is an anode active material during repeated charging and discharging of a lithium secondary battery. By suppressing separation from the current collector due to contraction and expansion of the layer and/or interface separation between the negative electrode active material layers, the discharge capacity and charge/discharge efficiency of the lithium secondary battery can be maximized and the shortening of the charge/discharge cycle life can be minimized, It relates to an aqueous binder composition for a lithium secondary battery.

Lithium secondary batteries are mainly used in information and communication devices such as mobile phones and laptops, but recently, their use is expanding not only in these information and communication devices, but also in other industries such as electric vehicles.

Currently, graphite-based materials, which are generally used as anode active materials for mobile lithium secondary batteries such as cell phones and laptops, have a very small maximum electric capacity of about 370mAh/g, so there is a limit to their application. In addition, as an anode active material capable of such a high capacity, a silicon-based material may be used. These materials can manufacture a lithium secondary battery with a high capacity of 500 mAh/g or more depending on the material design.

However, the silicon-based negative active material greatly contracts and expands the volume of the negative active material during charging and discharging of the lithium secondary battery, and as a result, the negative active material is separated from the current collector such as copper foil or the interface between the negative active materials occurs. Therefore, there is a problem in that the current collection in the negative electrode may be deteriorated, and furthermore, the charge/discharge cycle life of the lithium secondary battery is deteriorated.

On the other hand, in the case of applying a binder such as SBR / CMC, which is mainly used as a binder for conventional graphite-based negative electrode active materials, water can be used as a solvent, but the volume expansion and cycle life of the negative electrode are insufficient to solve the above problems. In addition, as a method to solve this problem, a method of using polyimide having excellent adhesive strength and excellent mechanical properties as a binder for negative electrode active materials has been proposed, but since the solvent is an organic solvent such as NMP, its use is limited due to environmental problems. , Water-based polyimide precursors using imidazoles in which methyl groups such as 1,2-dimethylimidazole are substituted in an aqueous medium are being developed, but storage stability is greatly reduced and volume expansion inhibition of the negative electrode is difficult to apply as a binder for lithium secondary batteries. It has not yet reached a satisfactory level.

Therefore, there is an urgent need for a new binder composition for an anode active material of a lithium secondary battery capable of maximizing the cycle life of a lithium secondary battery by suppressing shrinkage and expansion of the anode active material layer during repeated charging and discharging of the lithium secondary battery.

An object of the present invention is to prepare an environmentally friendly binder using water without using an organic solvent in preparing an amic acid oligomer for application as an aqueous binder composition for a lithium secondary battery. In addition, it has excellent storage stability and mechanical strength, and when applied to lithium secondary batteries, it is used for anode active materials of new lithium secondary batteries that can maximize cycle life while suppressing contraction and expansion of the anode active material layer during repeated charging and discharging. It is an object to provide a water-based binder composition.

In order to solve the above problems, the present invention,

As an aqueous binder composition for a lithium secondary battery,

An aqueous binder composition for a lithium secondary battery comprising an amic acid oligomer represented by Formula 1 below is provided.

[Formula 1]

In Formula 1,

X is a divalent organic group containing an aromatic or aliphatic group having 4 to 18 carbon atoms;

Y is a tetravalent organic group containing an aromatic or aliphatic group having 4 to 18 carbon atoms;

Z is a divalent organic group containing a double bond of 2 to 12 carbon atoms,

n is an integer from 10 to 50;

Here, an aqueous binder composition for a lithium secondary battery is provided, which further comprises a water-soluble imidazole represented by Chemical Formula 2 and a thermal initiator represented by Chemical Formula 3 below.

[Formula 2]

[Formula 3]

Further, the amic acid oligomer of Formula 1 is formed by reacting diamine of Formula 4 with acid dianhydride of Formula 5 and then capping both ends with an acid anhydride containing a double bond of Formula 6 below. An aqueous binder composition for secondary batteries is provided.

[Formula 4]

[Formula 5]

[Formula 6]

Definitions of X, Y and Z in Chemical Formulas 4 to 6 are the same as in Chemical Formula 1.

Meanwhile, the content of the thermal initiator of Formula 3 is 0.1% by weight or less based on the total weight of the amic acid oligomer of Formula 1, providing an aqueous binder composition for a lithium secondary battery.

Furthermore, the molar ratio of the diamine of Formula 4, the acid dianhydride of Formula 5 and the acid anhydride of Formula 6 is 100:90:20 to 100:98:4, characterized in that, to provide an aqueous binder composition for a lithium secondary battery .

In addition, the content of the water-soluble imidazole of Formula 2 is 1.8 to 4 times the mole based on the number of moles of the diamine of Formula 4, providing an aqueous binder composition for a lithium secondary battery.

And, the diamine of Formula 4 is 4,4'-methylenedianiline (4,4'-methylenedianiline), 4,4'-oxydianiline (4,4'-oxydianiline), 3,4'-oxydianiline (3,4'-Oxydianiline), 1,6-diaminohexane (1,6-diaminohexane), 1,4-cyclohexane diamine (1,4-Cyclohexane Diamine), 2,2-bis (3-amino- 4-hydroxyphenyl) -hexafluoropropane (2,2-Bis (3-amino-4-hydroxyphenyl) -hexafluoropropane), 1,3-bis (3-aminophenoxy) benzene (3-Bis (3- aminophenoxy)benzene), 2,2-bis(3-amino-4-hydroxyphenyl)propane), 1,3-bis(3-aminopropyl) ) Tetramethyldisiloxane (1,3-Bis (3-aminopropyl) tetramethyldisiloxane), 4,4'-methylenebiscyclohexylamine (4,4'-Methylenebiscyclohexylamine), m-phenylenediamine (m-phenylenediamine), p -phenylenediamine (p-phenylenediamine), m-xylenediamine (m-xylenediamine), 3,3'-dimethylbenzidine (3,3'-dimethylbenzidine), 3,5-diaminobenzoic acid ), 2,4-diaminobenzenesulfonyl acid, 4,4-benzophenonediamine, 3,3'-dimethyl-4,4'-diaminodiamine Cyclohexylmethane (3,3'-Dimethyl-4,4'-diamino dicyclohexylmethane) and 5,5'-methylene-bis (anthranilic acid) selected from the group consisting of It provides an aqueous binder composition for a lithium secondary battery, characterized in that it comprises one or more.

In addition, the acid dianhydride of Formula 5 includes 3,3',4,4'-benzophenonetetracarboxylic dianhydride, pyromellitic dianhydride, 3,3',4,4'-biphenyl tetracarboxylic dianhydride (3,3',4,4'-Biphenyl tetracarboxylic dianhydride), 1,2,3,4-cyclopentanetetracarboxylic acid anhydride (1 ,2,3,4-cyclopentanetetracarboxylic dianhydriede), 1,2,3,4-cyclobutanetetracarboxylic dianhydriede), 4,4'-oxydiphthalic anhydride (4 ,4'-oxidiphthalic anhydride) and 5-(2,5-dioxotetrahydrofuryl)-3-methyl-3-cyclohexene-1,2,-dicarboxylic acid anhydride (5-(2,5-Dioxotetrahydrofuryl ) -3-Methyl-3-Cyclohexene-1,2-Dicarboxylic Anhydride) to provide an aqueous binder composition for a lithium secondary battery, characterized in that it comprises at least one selected from the group consisting of.

Furthermore, the acid anhydride containing the double bond of Formula 6 is 4-cyclohexene-1,2-dicarboxylic anhydride, 5-norbornene-2,3-dicarboxylic acid 5-Norbornene-2,3-dicarboxylic Anhydride, Allylsuccinic Anhydride, Exo-3,6-Epoxy-1,2,3,6-Tetrahydrophthalic Anhydride (exo-3,6-Epoxy -1,2,3,6-tetrahydrophthalic Anhydride), 3-Methyl-4-cyclohexene-1,2-dicarboxylic anhydride (3-Methyl-4-cyclohexene-1,2-dicarboxylic Anhydride), maleic anhydride ( maleic anhydride) and bicyclo[2.2.2]oct-5-ene-2,3-dicarboxylic anhydride (Bicyclo[2.2.2]oct-5-ene-2,3-dicarboxylic Anhydride) 1 It provides an aqueous binder composition for a lithium secondary battery, characterized in that it comprises more than species.

The aqueous binder composition for an anode active material of a lithium secondary battery according to the present invention does not use an organic solvent such as NMP, which is harmful to the human body and expensive, but uses water as a solvent, thereby providing an environmentally friendly, low-cost binder, and has storage properties. At the same time, it shows an excellent effect of maximizing the stability of the lithium secondary battery and the charge/discharge cycle through the suppression of the volume expansion of the negative electrode.

1 is a graph showing cycle life evaluation of a lithium secondary battery to which a binder composition prepared in Example 1 is applied.

Hereinafter, preferred embodiments of the present invention will be described in detail. However, the present invention is not limited to the embodiments described herein and may be embodied in other forms. Rather, the embodiments introduced herein are provided so that the disclosed content will be thorough and complete, and the spirit of the present invention will be sufficiently conveyed to those skilled in the art.

The present invention relates to an aqueous binder composition for a lithium secondary battery, and specifically, after reacting a diamine compound of Chemical Formula 4 with an acid dianhydride of Chemical Formula 5 in water as a reaction solvent, both ends are capped with an acid anhydride having a double bond of Chemical Formula 6. and an amic acid oligomer of Formula 1, an imidazole of Formula 2, and a thermal initiator of Formula 3.

[Formula 1]

[Formula 2]

[Formula 3]

[Formula 4]

[Formula 5]

[Formula 6]

In Chemical Formulas 1 to 6, X is a divalent organic group containing an aromatic or aliphatic group having 4 to 18 carbon atoms, Y is a tetravalent organic group containing an aromatic or aliphatic group having 4 to 18 carbon atoms, and Z is a group having 2 to 12 carbon atoms. It is a divalent organic group containing a double bond of, n is an integer from 10 to 50.

When the number of carbon atoms in X and Y exceeds 18 or the number of carbon atoms in Z exceeds 12, solubility in water is low, making it impossible to obtain a desired level of amic acid oligomer.

In addition, when n is less than 10, the degree of polymerization is too low, and physical properties of the binder are deteriorated, and when n exceeds 50, storage stability is deteriorated.

Examples of specific diamines of Formula 4 include 4,4'-methylenedianiline, 4,4'-oxydianiline, and 3,4'-oxydianiline. Aniline (3,4'-Oxydianiline), 1,6-diaminohexane (1,6-diaminohexane), 1,4-cyclohexane diamine (1,4-Cyclohexane Diamine), 2,2-bis (3-amino) -4-hydroxyphenyl) -hexafluoropropane (2,2-Bis (3-amino-4-hydroxyphenyl) -hexafluoropropane), 1,3-bis (3-aminophenoxy) benzene (3-Bis (3 -aminophenoxy)benzene), 2,2-bis (3-amino-4-hydroxyphenyl) propane (2,2-Bis (3-amino-4-hydroxyphenyl) propane), 1,3-bis (3-amino propyl) tetramethyldisiloxane (1,3-Bis (3-aminopropyl) tetramethyldisiloxane), 4,4'-methylenebiscyclohexylamine (4,4'-Methylenebiscyclohexylamine), m-phenylenediamine (m-phenylenediamine), p-phenylenediamine, m-xylenediamine, 3,3'-dimethylbenzidine, 3,5-diaminobenzoic acid acid), 2,4-diaminobenzenesulfonyl acid, 4,4-benzophenonediamine, 3,3'-dimethyl-4,4'-diamino It may be dicyclohexylmethane (3,3'-Dimethyl-4,4'-diamino dicyclohexylmethane), 5,5'-methylenebis anthranilic acid (5,5'-Methylene-bis (anthranilic acid)), etc. It is not limited.

In addition, the acid dianhydride of Formula 5 is, for example, 3,3',4,4'-benzophenonetetracarboxylic dianhydride (3,3',4,4'-benzophenonetetracarboxylic dianhydride), pyromellitic acid anhydride (pyromellitic dianhydride), 3,3',4,4'-biphenyl tetracarboxylic dianhydride, 1,2,3,4-cyclopentanetetracarboxylic acid 1,2,3,4-cyclopentanetetracarboxylic dianhydriede, 1,2,3,4-cyclobutanetetracarboxylic dianhydriede, 4,4'-oxydiphthal 4,4'-oxidiphthalic anhydride, 5-(2,5-dioxotetrahydrofuryl)-3-methyl-3-cyclohexene-1,2,-dicarboxylic anhydride (5-(2, 5-Dioxotetrahydrofuryl) -3-Methyl-3-Cyclohexene-1,2-Dicarboxylic Anhydride), etc., but is not limited thereto.

In addition, the acid anhydride containing the double bond of Formula 6 is, for example, 4-cyclohexene-1,2-dicarboxylic anhydride, 5-norbornene-2,3 -Dicarboxylic anhydride (5-Norbornene-2,3-dicarboxylic anhydride), allylsuccinic anhydride, exo-3,6-epoxy-1,2,3,6-tetrahydrophthalic anhydride (exo-3, 6-Epoxy-1,2,3,6-tetrahydrophthalic Anhydride), 3-Methyl-4-cyclohexene-1,2-dicarboxylic Anhydride, Male Maleic anhydride, Bicyclo[2.2.2]oct-5-ene-2,3-dicarboxylic anhydride, etc. , but is not limited thereto.

Meanwhile, it is possible to prepare an amic acid oligomer having a structure of Formula 1 by adding water-soluble imidazole having a structure of Formula 2 to enable a polymerization reaction while using water as a solvent and dissolving a monomer in an aqueous medium. After preparing the amic acid oligomer, a water-soluble thermal initiator having a structure of Chemical Formula 3 may be additionally included in order to be applied as a binder composition.

In the present invention, a method for preparing an amic acid oligomer having a double bond in Z through capping at both ends of the structure of Chemical Formula 1 is as follows.

In preparing the amic acid oligomer of Chemical Formula 1, it is preferable to use water as a solvent and add the diamine, acid dianhydride, and acid anhydride in a molar ratio of 100:90:20 to 100:98:4. If the molar ratio of acid dianhydride to diamine molar ratio of 100 is 90 or less and the molar ratio of acid anhydride at the terminal is 20 or more, the degree of polymerization is too low, and physical properties may deteriorate. It is too high and unstable, so there is a risk of deterioration in storage stability. In addition, in the case of a binder using an acid anhydride that does not use an end group or does not have a double bond even if it is used, the decomposition reaction proceeds rapidly due to the aqueous solvent during thermal curing, and the tensile strength is significantly lowered, so the volume of the negative electrode of the lithium secondary battery It fails to suppress expansion and significantly reduces cycle life.

Meanwhile, in preparing the amic acid oligomer, imidazole having a structure of Chemical Formula 2 may be used. When imidazoles are substituted with one or more methyl groups, such as 1,2-dimethylimidazole or 1-methylimidazole, they remain in the binder composition even after the reaction is completed and act as a catalyst to slowly progress the imidation and crosslinking reaction even at low temperatures below 25 ° C. During storage, the viscosity rises rapidly, making it difficult to use it in the actual cathode manufacturing process. In the case of imidazole having the structure of Chemical Formula 2 in which the ethyl group is substituted, it is possible to improve the storability by remaining in the binder composition even after the reaction is completed and minimizing the catalytic role. The amount of imidazole of the formula (2) is preferably 1.8 to 4 times the mole of the diamine to be added. If it is 1.8 times mole or less, the monomer is not dissolved in the aqueous solvent or causes a decrease in polymerization reactivity, and if it is 4 times mole or more, there is a concern that properties as a binder for a lithium secondary battery may be deteriorated.

Meanwhile, the reaction temperature is 50° C. to 100° C. for 6 hours to 48 hours to prepare an amic acid oligomer having double bonds at both ends.

In addition, 0.1% by weight or less of a water-soluble thermal initiator having a structure of Chemical Formula 3 may be included relative to the prepared amic acid oligomer having a structure of Chemical Formula 1. If it exceeds 0.1% by weight, there is a risk of deteriorating the properties of the binder. In the case of the thermal initiator having the structure of Chemical Formula 1, it is possible to further improve the tensile strength due to the crosslinking reaction of double bonds at both ends during thermal curing while maintaining the storage stability of the amic acid oligomer.

[Example]

Example 1. Preparation of aqueous amic acid oligomer

190 g of distilled water was added to a 500 mL four-necked round flask, 13.5 g (0.14 mol) of imidazole of formula 2 was added, 13.9 g (0.07 mol) of MDA was added and dissolved, 14.5 g (0.67 mol) of PMDA, CHA 1.07g (0.007mol) was added and reacted at 70° C. for 12 hours to prepare an amic acid oligomer having a solid content of 13wt% and a viscosity of 3,200 cps.

Example 2. Preparation of aqueous amic acid oligomer

236 g of distilled water was added to a 500 mL four-necked round flask, 0.14 mol of imidazole of Formula 2 was added, 0.07 mol of MDA was added and dissolved, 0.67 mol of BTDA and 0.007 mol of CHA were added, and 12 hours at 70 ° C. By reacting, an amic acid oligomer having a solid content of 13wt% and a viscosity of 2,400 cps was prepared.

Example 3. Preparation of aqueous amic acid oligomer

224 g of distilled water was added to a 500 mL four-necked round flask, 0.14 mol of imidazole of Formula 2 was added, 0.07 mol of MDA was added and dissolved, 0.67 mol of BPDA and 0.007 mol of CHA were added, and 12 hours at 70 ° C. By reacting, an amic acid oligomer having a solid content of 13wt% and a viscosity of 2,800 cps was prepared.

Example 4. Preparation of aqueous amic acid oligomer

231 g of distilled water was added to a 500 mL four-necked round flask, 0.14 mol of imidazole of Formula 2 was added, 0.07 mol of MDA was added and dissolved, 0.67 mol of ODPA and 0.007 mol of CHA were added, and 12 hours at 70 ° C. By reacting, an amic acid oligomer having a solid content of 13wt% and a viscosity of 2,300 cps was prepared.

Example 5. Preparation of aqueous amic acid oligomer

191 g of distilled water was added to a 500 mL four-necked round flask, 0.14 mol of imidazole of Formula 2 was added, 0.07 mol of ODA was added and dissolved, 0.67 mol of PMDA and 0.007 mol of MA were added, and 12 hours at 70 ° C. By reacting, an amic acid oligomer having a solid content of 13wt% and a viscosity of 3,800 cps was prepared.

Example 6. Preparation of aqueous amic acid oligomers

237 g of distilled water was added to a 500 mL four-necked round flask, 0.14 mol of imidazole of Formula 2 was added, 0.07 mol of ODA was added and dissolved, 0.67 mol of BTDA and 0.007 mol of MA were added, and 12 hours at 70 ° C. By reacting, an amic acid oligomer having a solid content of 13wt% and a viscosity of 2,900 cps was prepared.

Example 7. Preparation of aqueous amic acid oligomer

225 g of distilled water was added to a 500 mL four-necked round flask, 0.14 mol of imidazole of Formula 2 was added, 0.07 mol of ODA was added and dissolved, 0.67 mol of BPDA and 0.007 mol of MA were added, and 12 hours at 70 ° C. By reacting, an amic acid oligomer having a solid content of 13wt% and a viscosity of 3,200 cps was prepared.

Example 8. Preparation of aqueous amic acid oligomer

232 g of distilled water was added to a 500 mL four-necked round flask, 0.14 mol of imidazole of Formula 2 was added, 0.07 mol of ODA was added and dissolved, 0.67 mol of ODPA and 0.007 mol of MA were added, and 12 hours at 70 ° C. By reacting, an amic acid oligomer having a solid content of 13wt% and a viscosity of 2,700 cps was prepared.

Example 9. Preparation of water-based amic acid oligomers

191 g of distilled water was added to a 500 mL four-necked round flask, 0.14 mol of imidazole of Formula 2 was added, 0.07 mol of p-PDA was added and dissolved, 0.67 mol of PMDA and 0.007 mol of MA were added, and at 70 ° C. By reacting for 12 hours, an amic acid oligomer having a solid content of 13wt% and a viscosity of 3,300 cps was prepared.

Example 10. Preparation of aqueous amic acid oligomers

237 g of distilled water was added to a 500 mL four-necked round flask, 0.14 mol of imidazole of Formula 2 was added, 0.07 mol of p-PDA was added and dissolved, 0.67 mol of BTDA and 0.007 mol of MA were added, and at 70 ° C. By reacting for 12 hours, an amic acid oligomer having a solid content of 13wt% and a viscosity of 3,100 cps was prepared.

Comparative Example 1. Preparation of water-based polyamic acid

182 g of distilled water was added to a 500 mL four-necked round flask, 0.14 mol of DMI was added, 0.07 mol of MDA was added and dissolved, and 0.07 mol of PMDA was added and reacted at 70 ° C for 12 hours to obtain a solid content of 13 wt% and a viscosity of 4,900 Polyamic acid of cps was prepared.

Comparative Example 2. Preparation of aqueous amic acid oligomer

177 g of distilled water was added to a 500 mL four-necked round flask, 0.14 mol of DMI was added, 0.07 mol of MDA was added and dissolved, 0.67 mol of PMDA and 0.007 mol of PA were added, and reaction was performed at 70 ° C for 12 hours to obtain a solid content of 13 wt. %, an amic acid oligomer having a viscosity of 2,500 cps was prepared.

Comparative Example 3. Preparation of aqueous amic acid oligomer

190 g of distilled water was added to a 500 mL four-necked round flask, 0.14 mol of MI was added, 0.07 mol of MDA was added and dissolved, and 0.07 mol of PMDA was added and reacted at 70 ° C for 12 hours to obtain a solid content of 13 wt% and a viscosity of 4,600 An amic acid oligomer of cps was prepared.

Experimental Example 1. Storage stability evaluation (viscosity increase rate)

After measuring the initial viscosity of each of the binder compositions of Examples 1 to 10 and Comparative Examples 1 to 3 as a binder composition, the viscosity change rate after storage at 5 ° C. for 30 days and the viscosity change rate after storage at 25 ° C. for 5 days were measured, respectively. The results are shown in Table 1.

- Viscosity increase rate (%) = (final viscosity - initial viscosity) / initial viscosity * 100 %

Experimental Example 2. Evaluation of tensile strength

As a binder composition, 0.08w% of the water-soluble thermal initiator having the structure of Chemical Formula 3 was added and mixed with respect to the solid content of each of the binder compositions of Examples 1 to 10 and Comparative Examples 1 to 3, and then coated on a copper foil having a thickness of 18um for 2 hours at 300 ° C. After curing, a film having a total thickness of 45 to 50 um was prepared and the tensile strength was measured with a universal testing machine, and the results are shown in Table 1.

Experimental Example 3. Battery Characteristics Evaluation

A negative electrode plate was manufactured using each of the binder compositions obtained from Examples 1 to 10 and Comparative Examples 1 to 3. The negative electrode composition ratio was prepared by mixing 8% by weight of a binder, 70% by weight of graphite as a negative electrode active material, 18% by weight of silicon alloy, and 4% by weight of super-P as a conductive material in an aqueous medium to prepare a negative electrode slurry, and then the negative electrode slurry was prepared with copper It was applied to a current collector and dried at 300° C. for 2 hours to prepare a negative electrode. At this time, the loading amount of the negative electrode was 4.0 mg/cm ² .

Coin-type lithium secondary batteries were manufactured using the negative electrode prepared above, and the following characteristics of the negative electrode active material layer were respectively evaluated, and the results are shown in Table 1 below.

- Anode volume expansion rate (%) = (thickness when charging after 1 cycle - initial thickness) / initial thickness × 100 %

- Battery life = discharge capacity at the 50th cycle/discharge capacity at the first cycle × 100 %

MDA: 4,4'-methylenedianiline

ODA:　4,4'-oxydianiline

PPDA:　p-phenylenediamine

PMDA: pyromellitic dianhydride

BTDA: 3,3',4,4'-Benzophenonetetracarboxylic dianhydride

BPDA :　3,3',4,4'-Biphenyl tetracarboxylic dianhydride

ODPA:4,4'-Oxydiphthalic Anhydride

CHA: 4-Cyclohexene-1,2-dicarboxylic Anhydride,

MA: maleic anhydride;

PA: Phthalic anhydride

MI: 1-methylimidazole

DMI: 1,2-dimethylimidazole

Furtherance Early
viscosity
(cp) viscosity rise rate
(%) Seal
robbery
(Mpa) volume
rate of expansion
(%) battery
life span
(%) Diamine acid dianhydride acid anhydride imidazole 5℃ 25℃ Example 1 MDA PMDA CHA chemical formula 2 3,200 4 8 75 35 95 Example 2 MDA BTDA CHA chemical formula 2 2,400 3 6 68 38 92 Example 3 MDA BPDA CHA chemical formula 2 2,800 5 8 71 34 96 Example 4 MDA ODPA CHA chemical formula 2 2,300 4 8 81 33 93 Example 5 ODA PMDA MA chemical formula 2 3,500 4 9 82 32 95 Example 6 ODA BTDA MA chemical formula 2 2,900 7 12 75 37 94 Example 7 ODA BPDA MA chemical formula 2 3,200 3 7 81 34 93 Example 8 ODA ODPA MA chemical formula 2 2,700 4 9 71 35 96 Example 9 p-PDAs PMDA MA chemical formula 2 3,300 3 6 64 39 96 Example 10 p-PDAs BTDA MA chemical formula 2 3,100 6 11 61 37 94 Comparative Example 1 MDA PMDA - DMI 4,900 33 124 55 48 90 Comparative Example 2 MDA PMDA PA DMI 2,500 13 34 42 54 85 Comparative Example 3 MDA PMDA - MI 4,600 29 94 48 52 88

As shown in Table 1, the viscosity increase of the binder compositions prepared in Examples 1 to 10 is suppressed to within 7% when refrigerated at 5 ° C for 30 days, and the viscosity increase is reduced to less than 12% even when stored at 25 ° C for 5 days. suppression is possible Therefore, after preparing the negative electrode slurry in the electrode manufacturing process, it is easy to store at room temperature, so it is suitable for process application. However, the viscosity of the binder compositions prepared in Comparative Examples 1 to 3 rapidly increases when stored at room temperature, making it difficult to use them in actual electrode processes.

On the other hand, the binders prepared in Examples 1 to 10 exhibited excellent storage stability as well as excellent tensile strength, and even when battery characteristics were evaluated using the binders, the volume expansion inhibitory effect of the negative electrode was excellent, and the cycle life was excellent. characteristics were shown.

1 shows cycle life evaluation after manufacturing a coin cell with the binder composition prepared in Example 1. Compared to the initial discharge capacity, 95% of the discharge capacity was maintained after 50 cycles.

Claims (9)

As an aqueous binder composition for a lithium secondary battery,
An aqueous binder composition for a lithium secondary battery comprising an amic acid oligomer represented by Formula 1 below.
[Formula 1]

In Formula 1,
X is a divalent organic group containing an aromatic or aliphatic group having 4 to 18 carbon atoms;
Y is a tetravalent organic group containing an aromatic or aliphatic group having 4 to 18 carbon atoms;
Z is a divalent organic group containing a double bond of 2 to 12 carbon atoms,
n is an integer from 10 to 50; According to claim 1,
A water-based binder composition for a lithium secondary battery, characterized in that it further comprises a water-soluble imidazole of Formula 2 and a thermal initiator of Formula 3 below.
[Formula 2]

[Formula 3]

According to claim 1 or 2,
The amic acid oligomer of Chemical Formula 1 is formed by reacting diamine of Chemical Formula 4 with acid dianhydride of Chemical Formula 5 and then capping both ends with an acid anhydride containing a double bond of Chemical Formula 6, for use in a lithium secondary battery. A water-based binder composition.
[Formula 4]

[Formula 5]

[Formula 6]

Definitions of X, Y and Z in Chemical Formulas 4 to 6 are the same as in Chemical Formula 1. According to claim 2,
The content of the thermal initiator of Formula 3 is 0.1% by weight or less based on the total weight of the amic acid oligomer of Formula 1, characterized in that, the aqueous binder composition for a lithium secondary battery. According to claim 3,
A molar ratio of the diamine of Formula 4, the acid dianhydride of Formula 5 and the acid anhydride of Formula 6 is 100:90:20 to 100:98:4, characterized in that, the aqueous binder composition for a lithium secondary battery. According to claim 3,
An aqueous binder composition for a lithium secondary battery, characterized in that the content of the water-soluble imidazole of Formula 2 is 1.8 to 4 times mole based on the number of moles of diamine of Formula 4. According to claim 3,
The diamine of Formula 4 is 4,4'-methylenedianiline (4,4'-methylenedianiline), 4,4'-oxydianiline (4,4'-oxydianiline), 3,4'-oxydianiline (3 ,4'-Oxydianiline), 1,6-diaminohexane (1,6-diaminohexane), 1,4-cyclohexane diamine (1,4-Cyclohexane Diamine), 2,2-bis (3-amino-4- Hydroxyphenyl) -hexafluoropropane (2,2-Bis (3-amino-4-hydroxyphenyl) -hexafluoropropane), 1,3-bis (3-aminophenoxy) benzene (3-Bis (3-aminophenoxy) benzene), 2,2-bis (3-amino-4-hydroxyphenyl) propane (2,2-Bis (3-amino-4-hydroxyphenyl) propane), 1,3-bis (3-aminopropyl) tetra Methyldisiloxane (1,3-Bis(3-aminopropyl)tetramethyldisiloxane), 4,4'-methylenebiscyclohexylamine, m-phenylenediamine, p-phenyl Rendiamine (p-phenylenediamine), m-xylenediamine (m-xylenediamine), 3,3'-dimethylbenzidine (3,3'-dimethylbenzidine), 3,5-diaminobenzoic acid (3,5-diaminobenzoic acid), 2,4-diaminobenzenesulfonyl acid, 4,4-benzophenonediamine, 3,3'-dimethyl-4,4'-diaminodicyclohexyl One selected from the group consisting of methane (3,3'-Dimethyl-4,4'-diamino dicyclohexylmethane) and 5,5'-methylene-bis (anthranilic acid) Aqueous binder composition for a lithium secondary battery, characterized in that it comprises the above. According to claim 3,
The acid dianhydride of Formula 5 is 3,3',4,4'-benzophenonetetracarboxylic dianhydride, pyromellitic dianhydride, 3, 3',4,4'-biphenyl tetracarboxylic dianhydride (3,3',4,4'-Biphenyl tetracarboxylic dianhydride), 1,2,3,4-cyclopentanetetracarboxylic anhydride (1,2 ,3,4-cyclopentanetetracarboxylic dianhydriede), 1,2,3,4-cyclobutanetetracarboxylic dianhydriede), 4,4'-oxydiphthalic anhydride (4,4 '-oxidiphthalic anhydride) and 5-(2,5-dioxotetrahydrofuryl)-3-methyl-3-cyclohexene-1,2,-dicarboxylic anhydride (5-(2,5-Dioxotetrahydrofuryl)- 3-Methyl-3-Cyclohexene-1,2-Dicarboxylic Anhydride) characterized in that it comprises at least one selected from the group consisting of, an aqueous binder composition for a lithium secondary battery. According to claim 3,
The acid anhydride containing the double bond of Chemical Formula 6 is 4-cyclohexene-1,2-dicarboxylic acid anhydride, 5-norbornene-2,3-dicarboxylic acid anhydride ( 5-Norbornene-2,3-dicarboxylic Anhydride), Allylsuccinic Anhydride, Exo-3,6-Epoxy-1,2,3,6-Tetrahydrophthalic Anhydride (exo-3,6-Epoxy-1 ,2,3,6-tetrahydrophthalic Anhydride), 3-Methyl-4-cyclohexene-1,2-dicarboxylic Anhydride, maleic anhydride ) and at least one selected from the group consisting of bicyclo [2.2.2] oct-5-ene-2,3-dicarboxylic anhydride Characterized in that, the aqueous binder composition for a lithium secondary battery comprising a.

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