KR101683737B1 - Binder composite for anode-coating agent of secondary battery, Binder for anode of secondary battery using the same and Manufacturing method thereof - Google Patents

Abstract

The present invention relates to a binder composition for a coating agent for a negative electrode of a secondary battery, a binder using the same for a coating agent for a negative electrode of a secondary battery, and to a preparation method thereof. The binder for a coating agent for a negative electrode of a secondary battery has excellent solubility in water, and maintains proper viscosity, thereby having excellent storage stability while having excellent heat resistance. Thus, a negative electrode material prepared by using the coating agent for a secondary battery has low electrical resistance, and a secondary battery having improved charging and discharging characteristics can be provided by using the negative electrode material. The binder composition comprises: carboxymethyl cellulose; a catalyst; polyalkylene glycol; and a solvent.

Description

Technical Field The present invention relates to a binder composition for an anode coating agent for a secondary battery, a binder for an anode coating agent for a secondary battery using the same, and a method for manufacturing the same,

The present invention relates to a binder composition for a negative electrode coating agent for a secondary battery, a binder for a negative electrode coating agent for a secondary battery manufactured using the binder composition, and a method for producing the binder. The present invention relates to an invention capable of increasing the charge / discharge efficiency of a secondary battery due to its low electrical resistance.

As technology development and demand for mobile devices are increasing, the demand for secondary batteries as energy sources is rapidly increasing. Among such secondary batteries, lithium secondary batteries having high energy density and voltage, long cycle life and low self- It has been commercialized and widely used.

Such a lithium secondary battery uses graphite as a negative electrode active material, charging and discharging proceed while repeating the process in which lithium ions in the positive electrode are inserted into the negative electrode and desorbed. The theoretical capacity of the battery varies depending on the kind of the electrode active material, but the charging and discharging capacities decrease with the progress of the cycle.

This phenomenon is the biggest cause of the separation of the electrode active material or between the electrode active material and the current collector due to the change of the volume of the electrode due to the progress of the charging and discharging of the battery, so that the active material fails to function. In addition, lithium ions inserted into the negative electrode may not be properly discharged during the insertion or desorption, and the active sites of the negative electrode may be reduced. As a result, the charge / discharge capacity and lifetime characteristics of the battery may decrease as the cycle progresses.

Particularly, in order to increase the discharge capacity, when a material such as silicon, tin, silicon-tin alloy having a large discharging capacity is mixed with natural graphite having a theoretical discharge capacity of 372 mAh / g is used, The volume expansion of the negative electrode material is remarkably increased. As a result, the negative electrode material is separated from the electrode material. As a result, the capacity of the battery is drastically lowered due to repeated cycles.

Conventionally, techniques for adding a material such as polyvinylidene fluoride (PVdF), which is a solvent-based binder, have been proposed in order to prevent separation between the electrode active material or between the electrode active material and the current collector with strong adhesive force. However, Can not solve the fundamental problem of increasing the resistance and lowering the output.

In order to prevent this, various negative electrode coating materials for secondary batteries have been developed, but conventional negative electrode coating agents have a problem of low storage stability and heat resistance.

Japan Patent Publication No. 2012-501515 (2012.01.19) Korean Patent Publication No. 2014-0096961 (2014.08.06)

In the case of a binder used as an anode coating material for a conventional secondary battery, problems such as low heat resistance and storage stability are problematic and solubility is low. However, a compound having an optimum ratio of a specific composition has heat resistance, storage stability and excellent solubility Have been found to be suitable for use as a binder for secondary battery anode coatings. That is, the present invention provides a binder composition for an anode coating agent for a secondary battery, a binder for an anode coating agent for a secondary battery prepared using the binder composition, and a method for efficiently producing the binder.

In order to solve the above-mentioned problems, the binder composition for an anode coating agent for a secondary battery of the present invention comprises carboxymethyl cellulose (CMC); A catalyst comprising at least one member selected from the group consisting of NH ₄ OH, NaOH, NaCl, KOH, KCl, LiCl, LiBr, HCl, Acetic acid, Acrylic acid, H ₂ SO ₄ and HNO ₃ ; (C 2 -C 4 alkylene) glycol (PAG) containing at least one functional group selected from a hydroxyl group, a carboxylic acid group, an amine group, a halogenated group and an epoxy at the terminal; And a solvent.

In one preferred embodiment of the present invention, the binder composition for an anode coating for a secondary battery of the present invention comprises 1 to 5 wt% of CMC, 0.5 to 3 wt% of PAG, 0.1 to 2 wt% of catalyst, and 90 to 98 wt% .

In a preferred embodiment of the present invention, the CMC of the binder composition of the present invention is pH 7 ~ 8, and a weight average molecular weight of 500,000 to 1,000,000, from the Na ^+, K ^+, Li ^+, Rb ^+, Cs ⁺ and Fr ⁺ The degree of substitution may be 0.7 to 0.8 substituted by a group I ion including at least one selected.

In one preferred embodiment of the present invention, when 1 wt% of CMC is dissolved in distilled water, the viscosity of the dissolved solution may be 600 to 1,500 cps (25 DEG C).

In one preferred embodiment of the present invention, the PAG of the binder composition of the present invention may have a weight average molecular weight of 250 to 4,000.

In one preferred embodiment of the present invention, the PAG of the binder composition of the present invention is a poly (ethylene glycol) diglycidyl ether and a poly (propylene glycol) diglycidyl ether ether) may be included.

Another object of the present invention is to provide a method for producing a binder for a negative electrode coating agent for a secondary battery using the above-described composition, which comprises reacting a binder composition for a negative electrode coating agent for a secondary battery, Stage 1; Adjusting the pH of the reaction solution to 6.5 to 8; a third step of mixing the pH-adjusted reaction solution with methanol to obtain a precipitate; Crushing the precipitate to produce fine particles; 5) washing the fine particles; And drying the washed fine particles in a solvent to form a binder.

In one preferred embodiment of the present invention, the reactant may be a mixture of at least one selected from the group consisting of a hydroxyl group, a carboxylic acid group, an amine group, a halogenated group, and an epoxy group through a bond of at least one selected from an ester bond and an ether bond. May be grafted with a poly (C2-C4 alkylene) glycol (PAG) containing a functional group at the terminal.

In one preferred embodiment of the present invention, the reaction of the first step may be carried out at 15 ° C to 80 ° C for 1 hour to 8 hours.

In one preferred embodiment of the present invention, the ester bond and the ether bond ratio between CMC and PAG may differ depending on the type of the catalyst used in the binder composition in the first step.

As a preferred embodiment of the present invention, the reactant using NH ₄ OH as a catalyst in Step 1 may have a higher ester bond between CMC and PAG in the reactant than the reactant using NaOH, KOH or NaCl as a catalyst.

In one preferred embodiment of the present invention, the drying in step 6 may be performed at 40 ° C to 60 ° C for 2 to 12 hours.

Still another object of the present invention is to provide a binder for a negative electrode coating composition for a secondary battery produced by the above-described composition and process.

As a preferred embodiment of the present invention, the binder for a negative electrode coating agent for a secondary battery of the present invention is a binder for a negative electrode coating agent of the present invention, which comprises reacting at least one functional group selected from hydroxyl group, carboxylic acid group, amine group, halogenated group and epoxy, (PAG-g-CMC) grafted with a poly (C2-C4 alkylene) glycol (PAG)

In one preferred embodiment of the present invention, the binder for a negative electrode coating agent for a secondary battery of the present invention is in a powder form, and 10 to 100 parts by weight of PAG may be grafted to 100 parts by weight of CMC.

In one preferred embodiment of the present invention, the binder for a negative electrode coating agent for a secondary battery of the present invention may have a viscosity of 450 to 850 cps (25 ° C) when 1 wt% of the binder is dissolved in distilled water (99 wt%) at 25 ° C .

In one preferred embodiment of the present invention, the binder for the negative electrode coating solution for a secondary battery of the present invention may have a viscosity of 100 to 500 cps (50 ° C) when 1 wt% of the binder is dissolved in distilled water (99 wt%) at 50 ° C .

As a preferred embodiment of the present invention, a binder for a negative electrode coating solution for a secondary battery of the present invention is prepared by dissolving 1% by weight of a binder in distilled water (99% by weight) at 25 캜 for 7 days in a dark room and at 25 캜, At the time of measurement, the viscosity change rate may be 10% or less.

As a preferred embodiment of the present invention, the binder for a negative electrode coating agent for a secondary battery of the present invention may have a thermal decomposition temperature Td _{5% loss} value of 200 ° C or higher.

Still another object of the present invention is to provide a solid content including a binder for an anode coating agent for a secondary battery, an aqueous emulsion type binder and an electrode active material; And a solvent for a negative electrode coating for a secondary battery.

The coating agent for an anode of a secondary battery prepared by introducing the binder for a cathode coating agent for a secondary battery of the present invention is excellent in storage stability, heat resistance, and ionic conductivity, and the anode for a secondary battery manufactured using the same has low battery resistance. Can be used to provide a secondary battery with improved charge / discharge characteristics.

Fig. 1 is a FT-IR measurement graph conducted in Experimental Example 3. Fig.

The term PAG as used in the present invention means a poly (C2-C4 alkylene) glycol having at least one functional group selected from a hydroxyl group, a carboxylic acid group, an amine group, a halogenated group and an epoxy at the terminal.

Also, CMC means carboxymethylcellulose, and PAG-g-CMC means carboxymethylcellulose grafted with PAG.

Hereinafter, the present invention will be described in more detail.

The coating agent for an anode of a secondary battery of the present invention is a slurry-type coating agent in which a solid agent and a solvent are mixed. Carboxymethyl cellulose (CMC) powder grafted with a specific material is introduced as a binder component to reduce the electrical resistance And the ion conductivity of the secondary battery can be improved by improving the battery capacity and lifetime efficiency of the secondary battery.

When the solid content is less than 40% by weight, the content of the solvent is increased and the viscosity of the coating agent is lowered. Thus, Dewetting may occur. If the solid content exceeds 48% by weight, the content of the solvent may be relatively low, resulting in an excessively high viscosity of the coating agent, resulting in a problem of deterioration of coatability.

In the present invention, the solid content includes a binder and an electrode lubricant.

In the present invention, the binder may contain the PAG-g-CMC powder and the water-based emulsion type binder in a weight ratio of 1: 1 to 2, preferably 1: 1.2 to 1.8, wherein the weight ratio of the aqueous emulsion- 1, the amount of the PAG-g-CMC powder or the electrode lubricant may be relatively low if the amount of the PAG-g-CMC powder is too small to cause the electrode lubricant to have a low binding force (and / There may be a problem of not maintaining an appropriate viscosity at the time of coating or decreasing the capacity efficiency of the electrode.

The aqueous emulsion type binder may be a binder commonly used in the art, and preferably at least one selected from styrene butadiene rubber (SBR), acrylic rubber, butadiene rubber, isoprene rubber, and polyurethane resin.

The content of the binder in the total weight of the solid is preferably from 0.5 to 5% by weight, more preferably from 1.5 to 4.5% by weight, and still more preferably from 2 to 4% by weight. %, There may be a problem that the electrode activator in the coating layer is separated from the electrode, and when it is used in an amount exceeding 5% by weight, the content of the electrode activator may be decreased and the capacity efficiency of the secondary battery may be decreased.

Among the solid components, the electrode activator plays a role of generating electric current by flowing current through a process of reversibly inserting / desorbing lithium ions. The electrode active material includes graphite powder, crystalline or amorphous carbon, graphite, activated carbon, Metal, lithium alloy, and silicon alloy, and graphite powder, crystalline or amorphous carbon, and silicon alloy may be preferably used. The content of the electrode lubricant is in the range of the total weight of the solid content excluding the binder.

Among the coating agent components of the present invention, water can be used as the solvent, and the content of the solvent in the entire coating agent is the balance of the solid content.

In the present invention, the grafted carboxymethyl cellulose (PAG-g-CMC) is a powder type, and CMC is a compound having at least one functional group selected from a hydroxyl group, a carboxylic acid group, an amine group, The poly (ethylene glycol) diglycidyl ether and the poly (propylene glycol) diglycidyl ether (PAG) are preferably used as the poly (C2 to C4 alkylene) glycol ), And more preferably polyethylene glycol diglycidyl ether. The PAG-g-CMC is obtained by grafting PAG with CMC by binding of at least one selected from an ester bond and an ether bond between PAG and CMC.

The PAG has a weight average molecular weight of 250 to 4,000, preferably a weight average molecular weight of 300 to 2,500, more preferably a weight average molecular weight of 400 to 800, and the PAG has a weight average molecular weight of 250 , There may be a problem that the ion conductivity and the electric resistance are not reduced when the binder is used as a binder of the secondary battery. If the molecular weight exceeds 4,000, the interaction between the CMC molecules becomes small due to the length of the grafted molecular chain, There may be a problem of reduction.

The PAG-g-CMC is obtained by grafting 10 to 100 parts by weight, preferably 25 to 80 parts by weight, more preferably 35 to 70 parts by weight of PAG to 100 parts by weight of CMC.

The CMC before the graft has a pH of 7 to 8 and has a weight average molecular weight of 500,000 to 1,000,000 and is substituted with a group I ion containing at least one selected from Na ⁺ , K ⁺ , Li ⁺ , Rb ⁺ , Cs ⁺ and Fr ⁺ The degree of substitution may be from 0.7 to 0.8, preferably from pH 7.4 to 8.0, the weight average molecular weight is from 750,000 to 950,000, and the degree of substitution is from 0.75 to 0.8, wherein the pH of the CMC is 7 to 8 There may be a problem that the stability of the material itself is deteriorated and the viscosity is decreased. If the weight average molecular weight of CMC is less than 500,000, there may be a problem of degradation in operation at a high temperature due to a decrease in physical properties due to a low molecular weight. If the weight average molecular weight exceeds 1,000,000, a problem of exceeding an appropriate viscosity level due to high molecular weight Can be. If the degree of substitution of the CMC is less than 0.7, there may be a problem that the solubility of the CMC in the solvent is lowered. When the degree of substitution exceeds 0.8, an unnecessarily highly substituted salt interacts with the lithium ion of the battery, There may be a problem.

This CMC before grafting has a viscosity of 600 to 1,500 cps (25 DEG C) when 1 wt% of CMC is dissolved in distilled water (99 wt%) at 25 DEG C while the grafted PAG-g- (25 DEG C), preferably 450 to 700 cps (25 DEG C), when dissolved in distilled water. The PAG-g-CMC powder has a viscosity of 100-500 cps (50 ° C), preferably 150-350 cps (50 ° C) when 1 wt% of the PAG-g-CMC powder is dissolved in distilled water (99 wt% to be.

The PAG-g-CMC powder was prepared by dissolving 1% by weight of the solution in 25% of distilled water (99% by weight) in a dark room at 25 ° C for 7 days, , Preferably not more than 8%, more preferably not less than 1% and not more than 5%, which is very excellent in storage stability.

The PAG-g-CMC powder, which is a binder component of the present invention, has a thermal decomposition temperature Td _{5% loss} value of 200 ° C or higher, preferably 210 ° C or higher, a Td _{5% loss} value of 174 ° C, The heat resistance is very excellent when compared.

A method of producing the PAG-g-CMC will now be described.

A first step of preparing a reaction solution comprising a reaction product in which a composition comprising the CMC, the PAG, a catalyst and a solvent is mixed and reacted; Adjusting the pH of the reaction solution to 6.5 to 8; a third step of mixing the pH-adjusted reaction solution with methanol to obtain a precipitate; Crushing the precipitate to produce fine particles; 5) washing the fine particles; And drying the cleaned microparticles. The PAG-g-CMC can be prepared by carrying out a process comprising:

In the first step, CMC of the composition is the same as that described above, and it may contain 1 to 5 wt%, preferably 1.5 to 4 wt% of the total weight of the composition. If the content of CMC is less than 1% by weight, there may be a problem that the yield and reactivity are lowered at the time of synthesis. When the content of CMC is more than 5% by weight, the monomer may not be uniformly mixed at a too high viscosity, It is recommended to use it within the range.

The composition may contain 0.2 to 5% by weight, preferably 0.7 to 3% by weight, of the PAG in the total weight. If the PAG content is less than 0.2% by weight, the degree of graphing of the PAG in the CMC may be too low, so that the ion conductivity may not be effective when applied to the electrode. If the PAG content is more than 5% by weight, It is preferable to use it within the above range.

In addition, the catalyst may be at least one selected from the group consisting of NH ₄ OH, NaOH, NaCl, KOH, KCl, LiCl, LiBr, HCl, Acetic acid, Acrylic acid, H ₂ SO ₄ and HNO ₃ , Preferably at least one selected from NH ₄ OH, NaOH, NaCl and KOH can be used. When PAG is grafted to CMC, it is grafted by ester bond and / or ether bond. In the first step reaction, the degree of ester bond and ether bond can be controlled depending on the type of catalyst.

For example, when PAG-g-CMC is prepared using NH ₄ OH, NaOH, KOH and NaCl as catalysts, the ester bond of PAG-g-CMC in the order of NH ₄ OH >>>>NaOH> KOH and NaCl, Tend to increase, and as a result, PAG-g-CMC having a high ester bond shows a tendency to increase in heat resistance and solubility in water.

In the first step, the catalyst may be used in an amount of 0.1 to 2% by weight, preferably 0.5 to 1.5% by weight. When the catalyst content is less than 0.1% by weight, the grafting reaction of PAG can not proceed If it exceeds 2% by weight, there may be a problem that it acts as an impurity after completion of polymerization due to unnecessary addition.

 Water may be used as the solvent in the composition of the first stage, and the content thereof is an amount excluding the content of CMC, PAG and catalyst in the entire composition.

The first stage reaction can be carried out at a room temperature of 15 ° C to 80 ° C for 1 hour to 8 hours, preferably 20 ° C to 60 ° C for 3 hours to 8 hours.

The second step is a step of adjusting the pH of the reaction solution to 6.5 to 8, preferably 6.7 to 7.5. If the pH is outside the above range, an acidic substance or basic substance existing in an excessive amount due to the neutralization reaction is not properly performed In step 3, the precipitate may act as an impurity and adversely affect the pH. Therefore, it is preferable to adjust the pH within the above range. The pH adjuster may be any of those generally used in the art. For example, acetic acid may be used.

 Step 4 is a step of grinding the precipitate obtained by filtering in Step 3 to obtain fine particles, and it is preferable that the fine particles are pulverized to have an average particle size of about 50 탆 to 200 탆, preferably about 50 탆 to 160 탆 .

The five-step washing method is not particularly limited. For example, the fine particles may be washed with acetone 2-3 times.

The drying in step 6 is a step of drying the washing liquid. In a preferable example, the washed fine particles can be dried in a vacuum oven at 40 to 60 ° C for about 2 to 12 hours.

A method of manufacturing a secondary battery anode according to an embodiment of the present invention in which the coating agent is introduced into a coating layer will be described as follows: a first step of coating the anode collector with the anode collector to form a coating layer; A second step of thermally drying the negative electrode collector on which the coating layer is formed; A third step of compressing the thickness of the negative electrode collector on which the thermally dried coating layer is formed by performing a roll-press process; And drying the negative electrode current collector having the compressed coating layer formed thereon, thereby producing a negative electrode for a secondary battery.

The negative electrode current collector in the first step may be a conventional negative electrode material used as an anode current collector in the art. For example, one selected from the group consisting of copper foil, aluminum, stainless steel and nickel may be used. But is not limited thereto.

The thermal drying in the second step may be performed at 95 ° C to 120 ° C, preferably at 95 ° C to 110 ° C. If the thermal drying temperature is less than 95 ° C, the solvent may not sufficiently evaporate. If it exceeds 120 ° C, there may be a problem that the negative electrode collector is oxidized or the polymeric binder is thermally deformed.

The above-described coating agent of the present invention and a secondary battery electrode prepared using the same have low electrical resistance and high ion conductivity, which is introduced into a secondary battery, preferably a lithium secondary battery, Can be provided.

Hereinafter, the present invention will be described in more detail with reference to the following examples. However, the following examples should not be construed as limiting the scope of the present invention, and should be construed to facilitate understanding of the present invention.

[ Example ]

Preparation Example  One : PAG -g- CMC  Synthesis of powder

1% by weight of NH ₄ OH as a catalyst, 2% by weight of CMC (carboxymethyl cellulose) as a monomer and 97% by weight of distilled water as a solvent were added to a reactor equipped with a thermostat and a nitrogen purge apparatus, Lt; / RTI >

At this time, the CMC had a pH of 7.8, a Mw of 900,000 to 910,000, and a degree of substitution with Na ⁺ of 0.77.

Next, 25 parts by weight of PEGDE (poly (ethylene glycol) diglycidyl ether) having a weight average molecular weight of 500 was added to the inside of the reaction vessel twice per 100 parts by weight of the CMC, and the external gas was prevented from penetrating into the reactor The stirring was carried out while maintaining the temperature at 25 while adjusting.

As the stirring progressed, it was observed that the PEGDE was uniformly mixed, and the reaction was maintained for about 5 hours or more.

After completion of the reaction, acetic acid was added little by little to adjust the pH to between 6.5 and 7.5, and precipitated in methanol to obtain a solid polymer material, which was then pulverized into fine particles using a pulverizer.

The pulverized fine particle polymer material was washed with acetone 2-3 times, and then the washed solid polymer material was dried in a vacuum oven at 52 ° C to 55 ° C for about 24 hours to obtain a final product.

Preparation Example  2

PAG-g-CMC powder was prepared in the same manner as in Preparation Example 1 except that 1 wt% of NaOH was used instead of NH ₄ OH as a catalyst.

Preparation Example  3

Prepared in the same manner as in Preparation Example 1, except that PAG-g-CMC powder was prepared using 1 wt% of KOH instead of NH ₄ OH as a catalyst.

Preparation Example  4

The preparation of PAG-g-CMC powder was carried out in the same manner as in Preparation Example 1 except that 1 wt% of NaCl was used instead of NH ₄ OH as a catalyst.

Preparation Example  5

G-CMC powder was prepared in the same manner as in Preparation Example 1 except that the CMC had a pH of 7.5, a weight average molecular weight of 620,000 to 630,000 and a degree of substitution of 0.79 with Na ⁺ of 0.79. .

Preparation Example  6

The measurement was carried out in the same manner as in Preparation Example 1, except that 20 parts by weight of PEGDE was added to 100 parts by weight of CMC twice over 10 parts by weight of PEGDE.

Preparation Example  7

Was measured in the same manner as in Preparation Example 1, except that 80 parts by weight of PEGDE was added to the CMC in an amount of 40 parts by weight twice over 100 parts by weight of CMC.

Example of comparison preparation  One

The CMC of Example 1 was prepared as a binder.

Example of comparison preparation  2

But measured in the same manner as in Example 1, above, and CMC instead of pH 7.5, a weight average molecular weight is 300,000 ~ 310,000, the PAG-g-CMC powder using a 0.71 in CMC substitution to Na ⁺ also (Degree of substitution) .

Example of comparison preparation  3

The measurement was conducted in the same manner as in Example 1, except that a total of 8 parts by weight of PEGDE over 2 parts of 4 parts by weight of PEGDE relative to 100 parts by weight of CMC was used.

Example of comparison preparation  4

The measurement was conducted in the same manner as in Example 1, except that 120 parts by weight of PEGDE was added to 100 parts by weight of CMC twice over 60 parts by weight of PEGDE.

Experimental Example  One : PAG -g- CMC  Measurement of viscosity of powder and storage stability measurement

Each of the PAG-g-CMC powders prepared in the preparation examples and comparative preparation examples was added to distilled water in an amount of 1 wt%, and dissolved at 25 ° C and 50 ° C, respectively. The viscosity of the solution was measured with a Brookfield viscometer And the results are shown in Table 1 below.

The viscosity of the solution measured at 25 캜 was stored in a dark room at 25 캜, and the viscosity was measured again after 7 days. The results are shown in Table 1 below.

division 25 ℃ Viscosity 50 ℃ Viscosity After 7 days
25 ℃ Viscosity Viscosity change rate Preparation Example 1 560 cps 200 cps 539 cps 3.8% Preparation Example 2 530 cps 195 cps 501 cps 5.5% Preparation Example 3 525 cps 193 cps 495 cps 5.7% Preparation Example 4 510 cps 178 cps 471 cps 7.6% Preparation Example 5 522 cps 200 cps 501 cps 4.0% Preparation Example 6 620 cps 250 cps 570 cps 8.1% Preparation Example 7 515 cps 190 cps 478 cps 7.2% Comparative Preparation Example 1 810 cps 390 cps 718 cps 11.4% Comparative Preparation Example 2 673 cps 290 cps 601 cps 10.7% Comparative Preparation Example 3 800 cps 374 cps 729 cps 8.9% Comparative Preparation Example 4 274 cps 103 cps 232 cps 15.3%

The results of the viscosity measurement of the above Table 1 show that the viscosity change rate of PAG-g-CMC of Preparation Examples 1 to 7 is as low as 10% or less, whereas in Comparative Preparation Examples 1 to 2 and Comparative Preparation Example 4, The viscosity change rate exceeded 10%.

Particularly, in Comparative Preparation Example 4 in which PEGDE was used in an amount exceeding 100 parts by weight, the rate of increase in viscosity change was very large as compared with Example 7.

Experimental Example  2 : PAG -g- CMC  Measurement of heat resistance of powder

The TGA of each of the PAG-g-CMC powders prepared in the preparation examples and comparative preparation examples was measured to determine the thermal decomposition temperature (Td _{5% loss} ). The results are shown in Table 2 below.

division Td _{5% loss} Preparation Example 1 215 ° C Preparation Example 2 201 ℃ Preparation Example 3 200 ℃ Preparation Example 4 202 ° C Preparation Example 5 210 ℃ Preparation Example 6 201 ℃ Preparation Example 7 212 ° C Comparative Preparation Example 1 174 ° C Comparative Preparation Example 2 176 ° C Comparative Preparation Example 3 183 DEG C Comparative Preparation Example 4 213 ° C

In the case of PAG-g-CMC (Comparative Preparation Example 3) in which the PAG was less than 10 parts by weight, the viscosity change rate was low and the storage stability was excellent. However, when the pyrolysis temperature was less than 200 ° C And the results were low.

Experimental Example  3: FT-IR measurement

The PAG-g-CMC powder of Preparation Examples 1 to 3 and the FT-IR of CMC of Comparative Preparation Example 1 were measured, and the measurement results thereof are shown in Fig.

Referring to FIG. 1, it can be seen that an ester bond peak was observed only at the catalyst at 1730 cm ^-1 using NH ₄ OH. In the case of Preparation 2 and Preparation Example 3 using NaOH or KOH, no ester peak was observed I did.

In the preparation examples 1 to 3, the ether binding peak was overlapped with the ether functional group present in the CMC itself and thus could not be confirmed.

Example 1: Secondary  Manufacture of battery negative electrode

Solids were prepared by mixing PAG-g-CMC powder, styrene-butadiene rubber (SBR) and graphite with electrode lubricant of Preparation Example 1 in the composition ratios shown in Table 3 below.

Next, 45% by weight of the solid content and 55% by weight of distilled water were mixed and kneaded with a homogenizer mixer to prepare a coating agent for a secondary battery negative electrode.

Next, the coating for secondary battery anode was cast on a copper foil having a thickness of 9 mu m to a thickness of 105 mu m by the doctor blade method .

Next, the coated cathode was put in an oven, and then dried at 100 DEG C for 6 hours or more, and then subjected to a roll press process to compress it to a thickness of 46 mu m.

Next, the compressed negative electrode was dried for 2 hours or longer under vacuum drying conditions to prepare a negative electrode for a secondary battery.

Example  2 ~ Example  9 and Comparative Example  1 ~ Comparative Example  5

A negative electrode for a secondary battery was prepared in the same manner as in Example 1 except that a coating agent having the composition and composition ratio shown in Table 3 was prepared and then the negative electrode for a secondary battery was prepared by the same process.

division Solids Solids: Solvent PAG-g-CAC powder SBR Graphite Example 1 Preparation Example 1 1 wt% 1.5 wt% 97.5 wt% 45 wt%: 55 wt% Example 2 Preparation Example 2 1 wt% 1.5 wt% 97.5 wt% 45 wt%: 55 wt% Example 3 Preparation Example 3 1 wt% 1.5 wt% 97.5 wt% 45 wt%: 55 wt% Example 4 Preparation Example 4 1 wt% 1.5 wt% 97.5 wt% 45 wt%: 55 wt% Example 5 Preparation Example 5 1 wt% 1.5 wt% 97.5 wt% 45 wt%: 55 wt% Example 6 Preparation Example 6 1 wt% 1.5 wt% 97.5 wt% 45 wt%: 55 wt% Example 7 Preparation Example 7 1 wt% 1.5 wt% 97.5 wt% 45 wt%: 55 wt% Example 8 Preparation Example 1 1 wt% 1.5 wt% 97.5 wt% 42 wt%: 58 wt% Example 9 Preparation Example 1 1 wt% 1.5 wt% 97.5 wt% 48 wt%: 52 wt% Comparative Example 1 Comparative Preparation Example 1 1 wt% 1.5 wt% 97.5 wt% 45 wt%: 55 wt% Comparative Example 2 Preparation Example 1 1.5 wt% 1 wt% 97.5 wt% 45 wt%: 55 wt% Comparative Example 3 Preparation Example 1 1 wt% 3 wt% 94.5 wt% 45 wt%: 55 wt% Comparative Example 4 Preparation Example 1 1 wt% 1.5 wt% 97.5 wt% 35 wt%: 65 wt% Comparative Example 5 Preparation Example 1 1 wt% 1.5 wt% 97.5 wt% 55 wt%: 45 wt%

Manufacturing example 1: Secondary  Manufacture of batteries

A 1 M LiPF ₆ electrolytic solution containing a cathode of Example 1, a cathode composed of LiCoO ₂ , and ethylene carbonate (EC) / dimethyl carbonate (DMC) / diethylene carbonate (DEC) in a 1: 1: The secondary cell was fabricated with coin cell of CR 2032 type.

At this time, the coin cell was fabricated in a glove box to block air contact and was used after being immersed in a constant temperature oven at 25 ° C for 24 hours so that the electrolytic solution could penetrate well.

Manufacturing example  2 to 9 and Comparative Manufacturing Example  1-5

A secondary battery was produced in the same manner as in Example 1 except that each of the negative electrodes of Examples 2 to 9 and Comparative Production Examples 1 to 5 was used in place of the negative electrode of Example 1, 9 and Comparative Production Examples 1 to 5, respectively.

Experimental Example  4: Battery performance evaluation

Each of the secondary batteries (coin cells) prepared in the production example and the comparative production example was measured for the electrical resistance of the negative electrode using an AC impedance measuring instrument. The results are shown in Table 4 below.

division Battery resistance (mΩ) Production Example 1 50.2 Production Example 2 51.2 Production Example 3 51.5 Production Example 4 51.9 Production Example 5 50.6 Production Example 6 51.2 Production Example 7 50.5 Production Example 8 50.4 Production Example 9 50.1 Comparative Preparation Example 1 56.3 Comparative Preparation Example 2 52.1 Comparative Production Example 3 50.4 Comparative Production Example 4 55.7 Comparative Preparation Example 5 54.6

As shown in Table 4, the battery resistance values of Comparative Examples 1 to 9 were relatively lower than those of Comparative Preparation Example 1, and the battery resistance values of Production Example 1 were lower than those of Production Examples 2 to 4 It looked.

In Comparative Preparation Example 2, in which the PAG-g-CMC powder and SBR were used in a weight ratio of less than 1: 1, the battery resistance value was increased as compared with Production Example 1, and the PAG-g- In Comparative Production Example 3 in which SBR was used in a weight ratio of 1: 2, there was almost no change in electric resistance when compared with Production Example 1. [

Further, in Comparative Production Example 4 in which the solid content was less than 40% by weight and Comparative Production Example 5 in which the solid content was more than 48% by weight, the electrical resistance value was greatly increased as compared with Production Example 1.

Experimental Example  5: Charging and discharging  Experiment

Charging and discharging tests were carried out at 25 ° C and 0.2 C-rate at 0 to 1.5 V voltage ranges, respectively, in the production examples and the comparative production examples, and the results are shown in Table 5 below.

division Charge / discharge measurement value
(mAh / g) Production Example 1 350 Production Example 2 347 Production Example 3 347 Production Example 4 347 Production Example 5 348 Production Example 6 346 Production Example 7 347 Production Example 8 348 Production Example 9 348 Comparative Preparation Example 1 330 Comparative Preparation Example 2 325 Comparative Production Example 3 342 Comparative Production Example 4 319 Comparative Preparation Example 5 322

The charge / discharge measurement values in Table 5 show that the results of Comparative Charge Preparation Examples 1 to 2 and Comparative Production Examples 4 to 5 show low charge / discharge measurement results, whereas in Production Examples 1 to 9, 340 mAh / g.

Experimental Example 6: Secondary  The C- rate star Charging and discharging  Experiment

The charging and discharging characteristics of the secondary batteries of Production Example 1 and Comparative Production Example 1 were tested for each C-rate using a Battery Cycler System (WBCS3000). The results are shown in Table 6 below.

Xc / 0.1C (%) division charge Discharge Production Example 1
(%) Comparative Preparation Example 1
(%) Production Example 1
(%) Comparative Preparation Example 1
(%) 0.2C 100 100 100 100 1C 99.6 99.6 99.7 99.7 2C 97.5 96.3 97.3 96.6 3C 92.1 89.2 91.7 88.9 5C 75.6 64.7 76.9 65.7

The charge / discharge characteristics of each C-rate in Table 6 are as follows. In the conditions up to 2C, the change in capacity efficiency is insignificant. However, in the high-speed charging and discharging condition of 3C or higher, the electrode using PAG- It was confirmed that the capacity efficiency was excellent.

Claims (17)

delete delete delete delete delete delete A first step of preparing a reaction solution containing a reactant in which a binder composition is mixed and reacted;
Adjusting the pH of the reaction solution to 6.5 to 8;
a third step of mixing the pH-adjusted reaction solution with methanol to obtain a precipitate;
Crushing the precipitate to produce fine particles;
5) washing the fine particles; And
And drying the washed fine particles,
The binder composition includes carboxymethylcellulose (CMC); A catalyst comprising at least one selected from the group consisting of NH ₄ OH, NaOH, NaCl, KOH, KCl, LiCl, LiBr, HCl, Acetic acid, Acrylic acid, H ₂ SO ₄ and HNO ₃ ; (C 2 -C 4 alkylene) glycol (PAG) which contains at least one functional group selected from a hydroxyl group, a carboxylic acid group, an amine group, a halogenated group, an ester group and an epoxy group at the terminal; And a solvent. The method for producing a binder for a negative electrode coating agent for a secondary battery according to claim 1,
8. The process of claim 7,
Wherein the carboxymethyl cellulose (CMC) comprises at least one functional group selected from the group consisting of a hydroxyl group, a carboxylic acid group, an amine group, a halogenated group, an ester group and an epoxy group through at least one bond selected from an ester bond and an ether bond, (C4) alkylene) glycol (PAG). ≪ / RTI >
[8] The method of claim 7, wherein the reaction of step 1 is performed at 15 [deg.] C to 80 [deg.] C for 1 hour to 8 hours.
The method according to claim 7, wherein the ester bond and the ether bond ratio between CMC and PAG are different depending on the type of the catalyst used in the binder composition in the first stage,
Wherein the reactant using NH ₄ OH as a catalyst has a higher ester bond between CMC and PAG in the reactant than the reactant using NaOH, KOH or NaCl as a catalyst.
The method of claim 7, wherein the drying in step 6 is performed at 40 ° C to 60 ° C for 2 to 12 hours.
delete Carboxymethylcellulose (CMC); A catalyst comprising at least one member selected from the group consisting of NH ₄ OH, NaOH, NaCl, KOH, KCl, LiCl, LiBr, HCl, acetic acid, acrylic acid, H ₂ SO ₄ and HNO ₃ ; (C 2 -C 4 alkylene) glycol (PAG) which contains at least one functional group selected from a hydroxyl group, a carboxylic acid group, an amine group, a halogenated group, an ester group and an epoxy group at the terminal; And a solvent;
(PAG-g-PAG) grafted with a poly (C 2 -C 4 alkylene) glycol (PAG) containing at least one functional group selected from hydroxyl group, carboxylic acid group, amine group, halogenated group, ester group and epoxy group at the terminal, CMC)
The PAG-g-CMC is in powder form,
Wherein the PAG-g-CMC is grafted with 10 to 100 parts by weight of PAG relative to 100 parts by weight of CMC.
14. The method of claim 13,
The viscosity of the solution obtained by dissolving the binder for secondary battery anode coating agent in 1 wt% of distilled water at 25 ° C and 99 wt% of distilled water is 450 to 850 cps (25 ° C)
Wherein the viscosity of the solution obtained by dissolving 1 wt% of the binder for the secondary battery negative electrode coating agent in 99 wt% of distilled water at 50 DEG C is 100 to 500 cps (50 DEG C).
15. The method according to claim 14, wherein a solution in which 1 wt% of a binder for a secondary battery anode coating solution is dissolved in 99 wt% of distilled water at 25 DEG C is stored for 7 days in a dark room and at 25 DEG C, And a binder for a negative electrode coating agent for a secondary battery.
14. The binder for an anode coating for a secondary battery according to claim 13, wherein the binder has a Td _{5% loss} value of at least 200 deg. C as a thermal decomposition temperature.
A solid content including a binder for a negative electrode coating agent for a secondary battery, an aqueous emulsion type binder and an electrode active material; And
A coating agent for an anode for a secondary battery comprising a solvent.

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