KR101385254B1 - Binder for Electrode Material and Secondary Battery Employed with the Same - Google Patents

Abstract

The present invention relates to a binder for electrode mixture and a secondary battery comprising the same, and more particularly to the electrode mixture CMC and a method for manufacturing the same, by using the CMC according to the present invention as a binder of the electrode mixture, in particular charge / discharge In spite of the large volume change of the negative electrode active materials, the bonding strength between the active materials and the current collector can be stably maintained, and the cracks due to the volume expansion of the active materials can be minimized, thereby enabling the commercialization of a high capacity silicon or tin-based negative electrode active material, thereby enabling high-capacity lithium. It can greatly contribute to the manufacture of a secondary battery.

Description

Binder for Electrode Mixture and Secondary Battery Comprising the Same {Binder for Electrode Material and Secondary Battery Employed with the Same}

The present invention relates to a binder for electrode mixture and a secondary battery comprising the same.

Secondary batteries are rechargeable, easy to miniaturize, and large in capacity, and typically include nickel-hydrogen (Ni-MH) batteries, lithium (Li) batteries, and lithium ion (Li-ion) batteries.

Here, the lithium ion battery uses lithium-transition metal oxide as the positive electrode active material, carbon or carbon composite material as the negative electrode active material, and a liquid electrolyte in which lithium salt is dissolved in one or more organic solvents including an oxygen group, a nitrogen group, and a sulfate group. It is used to generate an electromotive force when lithium ions are moved between the positive electrode and the negative electrode so that charging and discharging are performed.

In such a lithium ion battery, electrodes such as a positive electrode and a negative electrode are somewhat different depending on the type of battery, but are made of an active material made of lithium-transition metal oxide and carbon and polyvinylidene fluoride (PVDF). A slurry is prepared by mixing a binder, an organic solvent of N-methyl-2-pyrrolidone (NMP) and a conductive agent of carbon (for positive electrode), and then aluminium (Al) and copper (Cu) It is manufactured by the process of coating on the base material of foil, drying and roll-pressing again, and then cutting to predetermined size.

However, the binder used in the above electrode production has excellent high-rate charging and discharging characteristics, but the adhesive force is weak, resulting in dropping of the active material, which in turn reduces the life of the battery.

In consideration of this problem, US Pat. No. 5,380,606 discloses a binder of an electrode as polyamic acid, polyamide resin, polyvinylpyrrolidone and hydroxyalkylcellulose. It is proposed a mixed binder containing at least one polymer selected from the group selected to improve the life and reliability of the battery.

However, the above-mentioned mixed binder has to be subjected to high temperature heat treatment at 200 to 400 ° C. in order to remove the polyamic acid added during the drying process of the electrode plate, so that the operation of the process is complicated and difficult, and the physical properties of the electrode change during the heat treatment. There is this.

On the other hand, styrene butadiene rubber (SBR) is used as a binder having strong adhesive strength, which is used for manufacturing an electrode of a secondary battery. This adhesive strength is strong, but when the electrode is composed of a low rolling rate springback phenomenon occurs, thereby reducing the life of the battery due to the drop off of the active material by volume expansion during electrode charging, discharging.

Meanwhile, carboxymethyl cellulose (hereinafter referred to as 'CMC') is an environmentally friendly binder that dissolves or disperses well in water and satisfies conditions such as electrochemical stability, insolubility to organic solvents, and adhesion. Known.

However, the CMC is currently developed in Japan, the United States, etc., occupies most of the world market, and thus the domestic market relies on total imports.

Accordingly, the present inventors have found a binder and a method for producing the same, which are electrochemically stable and have a bonding force capable of adhering an active material to a substrate without being dissolved in an organic solvent in a battery, thereby completing the present invention.

KR 10-1994-0011483 A, June 21, 1994

In order to solve the above problems of the prior art, the present invention can increase the dispersion of the conductive agent in the electrode mixture and increase the electrolyte absorption of the electrode, thereby improving the battery characteristics such as initial capacity, cycle characteristics, etc. of the finished battery To provide a new composition ratio of the electrode mixture CMC.

The present invention is to provide a secondary battery electrode, characterized in that the manufacturing including the electrode mixture CMC.

The present invention for achieving this purpose is to increase the dispersion of the conductive agent in the electrode mixture and to increase the electrolyte absorption of the electrode, the electrode composition of a new composition ratio that can improve the battery characteristics such as initial capacity, cycle characteristics of the finished battery It provides a method for producing a CMC.

The present invention provides a CMC for electrode mixture having a weight average molecular weight (Mw) 800,000 to 900,000 prepared by the above method.

The present invention provides a secondary battery electrode, characterized in that the manufacturing including the electrode mixture CMC.

The binder according to the present invention is characterized in that the weight average molecular weight (Mw) 800,000 to 900,000 as a binder for electrode mixture of the secondary battery.

The binder according to the present invention is a binder for electrode mixture of a secondary battery, the viscosity is 250 to 300 cps when the substitution degree is 1 to 2, 1% by weight of an aqueous solution, the content of metal ions measured by ICP analysis is 150 to 250 ppm.

Hereinafter, the present invention will be described in detail.

CMC for electrode mixture according to the present invention has a weight average molecular weight (Mw) of 1,000,000 to 5,000,000 natural cellulose 1 to 40% by weight, IPA (isopropanol) and ethanol mixed alcohol 10 to 80% by weight, sodium hydroxide (NaOH) 1 to 30 It provides a CMC composition for electrode mixture comprising a weight%, 1 to 30% by weight chloroacetic acid (MCA).

In the present invention, the natural cellulose may be a mixed pulp of cotton fiber pulp and wood pulp, the mixing ratio of the cotton fiber pulp and wood pulp is a weight ratio, the weight ratio is preferably 1: 1, but is not limited thereto. .

The CMC for electrode mixture according to the present invention is 1 to 40% by weight of natural cellulose, preferably 10 to 30% by weight. If it is less than 1% by weight, the coating state of the surface of the active material is insufficient, and the contact area between the surface of the active material and the electrolyte is wide, resulting in poor battery safety. Moreover, there exists a problem that the adhesiveness of the electrode of a polymer and an electrical power collector, or binding property between electrode active materials falls, and the discharge capacity in a repetitive first discharge falls.

In addition, if it exceeds 40% by weight, the film formed on the surface of the electrode becomes too thick, the lithium ion permeability at the interface between the electrode active material and the electrolyte is poor, the internal resistance increases, and there is a problem that the first discharge capacity is lowered.

The present invention

1) preparing a mixed solution by adding 1 to 30% by weight of sodium hydroxide (NaOH) to 10 to 80% by weight of an IPA (isopropanol) and ethanol mixture;

2) preparing an alkaline cellulose by adding 1 to 40% by weight of the natural cellulose having a weight average molecular weight (Mw) of 1,000,000 to 5,000,000 to the mixed solution;

3) preparing a reactant by adding 1 to 30% by weight of chloroacetic acid (MCA) to the alkaline cellulose;

4) neutralizing the reaction by adding hydrochloric acid or nitric acid solution diluted in ethanol;

5) washing and filtering the neutralized reactants; And

6) drying the filtered reaction to obtain sodium carboxymethyl cellulose (CMC);

It provides a weight average molecular weight (Mw) comprising 800,000 to 900,000 of the method for producing a CMC electrode mixture comprising a.

The present invention is a CMC (sodium carboxymethyl cellulose) prepared by the above method, the weight average molecular weight (Mw) of 800,000 to 900,000, when the substitution degree of 1 to 2, the aqueous solution of 1% by weight of 250 to 300 cps, ICP analysis It provides a CMC for electrode mixture, characterized in that the content of the metal ion is measured by 150 to 250 ppm.

Natural cellulose according to the present invention can be used that the weight average molecular weight (Mw) is 1,000,000 to 5,000,000, more preferably 2,500,000 to 3,500,000 can be used.

When the weight average molecular weight (Mw) of the natural cellulose is less than 1,000,000, it is difficult to exert the electrolytic solution and elastic force in the electrode mixture binder of the secondary battery produced, resulting in a decrease in adhesive strength and a charge and discharge efficiency, and when exceeded 5,000,000, Absorption and swelling of excess electrolyte due to high affinity may cause detachment of the electrode from the current collector, which is not preferable.

In the present invention, the sodium hydroxide concentration of step 1) is characterized in that 50%.

In the present invention, the chloroacetic acid concentration of step 3) is characterized in that 30%.

More specifically, when the sodium hydroxide concentration of CMC is 50%, and monochloroacetic acid (MCA) concentration is 30%, mercuryization and etherification reactions occur completely to increase the solubility or dispersion in water, and the control CMC ( HB-45 (manufactured by Daichi, Japan), similar values were found, and it was confirmed that the original function could be performed as a binder for electrode mixture.

In the present invention, the hydrochloric acid, nitric acid or chelating agent of step 4) has an important meaning for the removal of metal impurities present in the CMC prepared by using the reactivity of the metal as well as the neutralization of the reactants and obtaining a high purity CMC.

The chelating agent may use ethylenediaminetetraacetic acid (EDTA), preferably one or more selected from EDTA-2Na, EDTA-3Na or EDTA-4Na, but is not limited thereto.

For example, when the CMC containing Zn is dispersed in ethanol diluted in water, and then reacted by mixing 1 to 20% by weight of EDTA-4Na and citric acid together with the metal indicator, the Zn metal ion is separated from the metal indicator. It can be separated and combined with EDTA-4Na or citric acid to extract Zn impurities.

In other words, when the metal component in the secondary battery CMC is included, the battery performance must be minimized by generating a serious problem that shortens the battery life as well as the battery performance to express the battery performance, the step 4) according to the present invention Has an important meaning.

[Reaction Scheme 1]

Ca ⁺² + 2HCl → CaCl₂ + H ² ↑

2Fe ^{+ 3} + 6HCl → 2FeCl ₃ + 3H ² ↑

CuO + 2HNO3 => Cu (NO ₃ ) ₂ + H2O

Cu + 4HNO ₃ => Cu (NO ₃ ) ₂ + 2H ₂ O + 2NO ₂

[Reaction Scheme 2]

Zn + In (metal indicator) → Zn-In

Zn-In + EDTA → Zn-EDTA (chelated material) + In (metal indicator)

In the present invention, the CMC is produced by the above method, characterized in that the content of metal ions measured by ICP analysis is 150 to 250 ppm.

In the present invention, the CMC is prepared by the above method, the degree of substitution is 1 to 1.5, characterized in that the viscosity when the aqueous solution 1% by weight is 250 to 300 cps.

CMC is water soluble, but like other water soluble polymers, it swells during dissolution and dissolves slowly.

When the degree of substitution of the CMC according to the present invention has a viscosity of less than 1 or 1% by weight of an aqueous solution of less than 250 cps, it is difficult for a binder to bind to the surface of the inorganic particles, and when the degree of substitution is more than 1.5 or 1% by weight of an aqueous solution. When the viscosity exceeds 300 cps, dissolution in a hydrophilic organic solvent occurs, which causes uneven reactions or imparts a viscosity of the binder to maintain the strength during manufacture of the electrode plate, which is not preferable.

In another aspect, the present invention provides a secondary battery electrode, characterized in that prepared by the electrode mixture prepared by the CMC (sodium Carboxymethyl cellulose).

More specifically, when the weight average molecular weight (Mw) 800,000 to 900,000, the substitution degree of 1 to 2, the aqueous solution of 1% by weight of 250 to 300 cps, the content of metal ions measured by ICP analysis is 150 to 250 ppm It provides a secondary battery electrode, characterized in that the manufacturing including the electrode mixture CMC characterized in that.

The secondary battery electrode is manufactured by coating an electrode mixture, in which an electrode active material, a binder, and optionally a conductive agent, a filler, and the like are mixed with a current collector. Specifically, the electrode mixture may be added to a predetermined solvent to prepare an electrode slurry, and then coated on a current collector such as a metal foil, dried, and rolled to prepare a predetermined sheet-shaped electrode.

The binder can be used both as a binder of the negative electrode and / or a positive electrode, more preferably used as a binder of the negative electrode. In particular, a binder having a high capacity but having a large volume change during charging and discharging may be a preferred binder when a silicon-based active material, a tin-based active material, a silicon-carbon-based active material, or the like is used as the negative electrode active material.

The silicon or tin-based negative active material is meant to include silicon (Si) particles, tin (Sn) particles, silicon-tin alloys, their respective alloy particles, composites, and the like. Typical examples of the alloy include, but are not limited to, solid solutions such as aluminum (Al), manganese (Mn), iron (Fe), titanium (Ti), intermetallic compounds, eutectic alloys, and the like. .

The binder may be included in about 1 to 50% by weight, preferably 2 to 20% by weight based on the total weight of the electrode mixture. If the content of the binder is too small, it is difficult to expect a role as a binder capable of withstanding the volume change generated during charging and discharging. On the contrary, the content of the binder is too high because it causes a decrease in the electrode capacity and an increase in resistance.

Preferred examples of the solvent used in the preparation of the electrode slurry include dimethyl sulfoxide (DMSO), N-methyl pyrrolidon (NMP), and the like. It can be used up to 400% by weight and is removed during the drying process.

In addition to the electrode active material and the binder of the present invention, the electrode mixture as described above may further include other components, such as a viscosity modifier, a conductive agent, a filler, a coupling agent, an adhesion promoter, or a combination of two or more thereof.

The viscosity modifier is a component that adjusts the viscosity of the electrode mixture so that the mixing process of the electrode mixture and the coating process on the current collector thereof can be facilitated. Examples of such viscosity regulators include polyvinylidene fluoride, It is not limited. In some cases, the above-described solvent may play a role as a viscosity adjusting agent.

The conductive agent is a component for further improving the conductivity of the electrode active material, and the conductive agent is not particularly limited as long as it has conductivity without causing chemical change in the battery. For example, natural graphite or artificial graphite may be used. Graphite; Carbon black such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, and summer black; Conductive fibers such as carbon fibers and metal fibers; Metal powders such as carbon fluoride, aluminum, and nickel powder; Conductive whiskeys such as zinc oxide and potassium titanate; Conductive metal oxides such as titanium oxide; Conductive materials such as polyphenylene derivatives and the like can be used.

The filler is an auxiliary component that suppresses the expansion of the electrode, and is not particularly limited as long as it is a fibrous material without causing chemical changes in the battery. Examples of the filler include olefin polymers such as polyethylene and polypropylene; Fibrous materials such as glass fibers and carbon fibers are used.

The coupling agent is an auxiliary component for increasing the adhesion between the active material and the binder, characterized in that it has two or more functional groups, such a coupling agent, for example, one functional group is silicon, tin, or graphite It may be a material that reacts with a hydroxyl group or a carboxyl group on the surface of the active material to form a chemical bond, and other functional groups form a chemical bond through a reaction with the polymer binder. Specific examples of the coupling agent include triethoxysilylpropyl tetrasulfide, mercaptopropyl triethoxysilane, aminopropyl triethoxysilane, and chloropropyl triethoxysilane ( chloropropyl triethoxysilane, vinyl triethoxysilane, methacryloxypropyl triethoxysilane, glycidoxypropyl triethoxysilane, isocyanatepropyl triethoxysilane (isocyanatopropyl Silane coupling agents, such as triethoxysilane) and cyanatopropyl triethoxysilane, are mentioned, but it is not limited to these.

The adhesion promoter is an auxiliary component added to improve the adhesion of the negative electrode active material to the current collector, for example oxalic acid, adipic acid, formic acid, acrylic acid Derivatives, itaconic acid derivatives, and the like.

In the electrode according to the present invention, a current collector is a site where electrons move in an electrochemical reaction of an active material, and a negative electrode current collector and a positive electrode current collector exist.

The negative electrode collector is generally made to have a thickness of 3 to 500 mu m. Such an anode current collector is not particularly limited as long as it has conductivity without causing chemical change in the battery, and may be formed of a material such as copper, stainless steel, aluminum, nickel, titanium, fired carbon, surface of copper or stainless steel A surface treated with carbon, nickel, titanium, silver or the like, an aluminum-cadmium alloy, or the like can be used.

The cathode current collector generally has a thickness of 3 to 500 mu m. Such a positive electrode current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery. For example, the surface of stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel Surface treated with carbon, nickel, titanium, silver, or the like may be used.

These current collectors may form fine concavities and convexities on the surface thereof to enhance the bonding strength of the electrode active material, and may be used in various forms such as films, sheets, foils, nets, porous bodies, foams, and nonwoven fabrics.

Among the electrode active materials, a carbon-based material, a silicon-based material, a tin-based material, a silicon-carbon-based material, and the like may be used. The positive electrode active material may be lithium cobalt oxide (LiCoO ₂ ), lithium nickel oxide (LiNiO ₂ ), or the like. Layered compounds of or compounds substituted with one or more transition metals; Lithium manganese oxides such as Li _{1 + x} Mn _{2 - x} O ₄ (where x is 0 to 0.33), LiMnO ₃ , LiMn ₂ O ₃ , LiMnO _2, and the like; Lithium copper oxide (Li ₂ CuO ₂ ); Vanadium oxides such as LiV ₃ O ₈ , LiFe ₃ O ₄ , V ₂ O ₅ and Cu ₂ V ₂ O ₇ ; Ni-site-type lithium nickel oxide represented by the formula LiNi _{1- x} M _x O ₂ , wherein M = Co, Mn, Al, Cu, Fe, Mg, B, or Ga, and x = 0.01 to 0.3; LiMn _{2 -x} M _x O ₂ , wherein M = Co, Ni, Fe, Cr, Zn or Ta, and x = 0.01 to 0.1, or Li ₂ Mn ₃ MO 8, where M = Fe, Co, Ni , Lithium manganese composite oxide represented by Cu or Zn); A LiMn ₂ O ₄ disulfide compound in which a part of Li in the formula is substituted with an alkaline earth metal ion; Fe ₂ (MoO ₄ ) ₃ and the like can be used.

By using the CMC according to the present invention as a binder of the electrode mixture, the bonding strength between the active materials and the current collector can be stably maintained despite the large volume change of the negative electrode active materials during charging and discharging, and cracks due to the volume expansion of the active materials Since it can minimize the commercialization of a high capacity silicon or tin-based negative electrode active material can greatly contribute to the production of large capacity lithium secondary battery.

1 is a graph illustrating a C-rate ratio of an electrode manufactured by using sodium carboxymethyl cellulose (CMC) according to the present invention.
(A: Use of CMC of Preparation Example, B: Use of CMC (HB-45: manufactured by Daiichi Japan) of Control)
2 is a graph showing the discharge capacity recovery rate after the initial cycle and 500 cycles of the electrode prepared by including the sodium carboxymethyl cellulose (CMC) according to the present invention,
(Cell-G: using CMC of preparation example, Cell-N: using CMC of control (HB-45: Daiichi Japan))
Figure 3 is a graph of the peel strength of the electrode prepared including the CMC (sodium Carboxymethyl cellulose) according to the present invention.

The present invention will be described in more detail with reference to the following examples. However, the following examples are provided to aid understanding of the present invention, and the scope of the present invention is not limited by these examples in any sense.

Hereinafter, the technical and scientific terms used herein will be understood by those skilled in the art without departing from the scope of the present invention. Descriptions of known functions and configurations that may be unnecessarily blurred are omitted.

[ Manufacturing example  1] high purity CMC Manufacturing Method

20% by weight (171.8 g) of cellulose mixed with fiber pulp having a weight average molecular weight (Mw) of 3,000,000 and soft wood pulp (Canada kamloops acid) in a 1: 1 weight ratio 15% by weight of aqueous 50% NaOH solution (128.8 g), IPA (isopropanol) and 54% by weight (463.9 g) of ethanol mixed alcohol were added to a kneader agitator (high viscosity stirrer) and stirred for 1 h while maintaining 37 ° C. for mercerization reaction.

After completion of the mercerization reaction, 11% by weight (94.5 g) of 30% monochloroacetic acid (MCA) aqueous solution was added to proceed the etherification at constant temperature, and the reaction of the etherification reaction was completed by diluting with ethanol. Neutralized with% hydrochloric acid solution. The neutralized reactant was washed three times with a mixture of ethanol and water, and the resulting reaction was filtered and finally washed with ethanol and dried (80 ° C./1 h) to obtain CMC powder.

[ Manufacturing example  2] high purity CMC Manufacturing Method

To prepare a CMC powder in the same manner as in Preparation Example 1, the reaction after the etherification was neutralized with a 30% EDTA solution diluted with ethanol.

[compare Manufacturing example  One]

To prepare a CMC powder in the same manner as in Preparation Example 1, 5% monochloroacetic acid (MCA) aqueous solution was used in the etherification reaction.

[compare Manufacturing example  2]

To prepare a CMC powder in the same manner as in Preparation Example 1, 15% monochloroacetic acid (MCA) aqueous solution was used in the etherification reaction.

[compare Manufacturing example  3]

To prepare a CMC powder in the same manner as in Preparation Example 1, 25% monochloroacetic acid (MCA) aqueous solution was used during the etherification reaction.

[compare Manufacturing example  4]

To prepare a CMC powder in the same manner as in Preparation Example 1, 40% NaOH aqueous solution was added during mercerization, and 30% monochloroacetic acid (MCA) aqueous solution was used during etherification.

[compare Manufacturing example  5]

A CMC powder was prepared in the same manner as in Preparation Example 1, except that 45% NaOH aqueous solution was added during mercerization, and 30% monochloroacetic acid (MCA) aqueous solution was used during etherification.

[compare Manufacturing example  6]

To prepare a CMC powder in the same manner as in Preparation Example 1, 55% NaOH aqueous solution was added during mercerization, and 30% monochloroacetic acid (MCA) aqueous solution was used during etherification.

[ Test Example  One] CMC Degree of substitution

Degree of Substitution (DS) of CMC of Preparation Example and CMC of Comparative Preparation Examples 1 to 6 was measured. CMC (HB-45: manufactured by Daiichi Japan) was used as a control. The degree of substitution used Green's method (J. W., cellulose Ether, In method in carbohydrate chemistry, whistler, R. L., Vol. 3, Academic press, New York, 1963, pp. 322).

[Formula 1]

(S is the dry mass of CMC (g), C is the volume of HCl standard solution (ml), N is the normal concentration of HCl solution, f is the correction coefficient of HCl standard solution).

Degree of substitution Solubility (%) Control 1.0 99 Production Example 1 1.1 99 Production Example 2 1.15 99 Comparative Preparation Example 1 0.39 60 Comparative Production Example 2 0.7 75 Comparative Production Example 3 0.78 82 Comparative Production Example 4 0.5 63 Comparative Preparation Example 5 0.67 74 Comparative Preparation Example 6 0.65 67

From the results of Table 1, sodium hydroxide concentration of Preparation Example CMC according to the present invention was completely dissolved in water and dispersed in water due to mercerization and etherification reactions under conditions of 50% and monochloroacetic acid (MCA) concentration of 30%. Also increased, showing a similar value to the control CMC (HB-45: manufactured by Daichi Japan), it was confirmed that the original function can be performed as a binder for electrode mixture.

[ Test Example  2] CMC Viscosity Measurement of Viscosity  : Brookfield Viscometer )

The viscosity of the CMC of Preparation Example and CMC of Comparative Preparation Examples 1 to 6 was measured. The viscosity was measured using a Brookfield Viscometer in the following manner. CMC (HB-45: manufactured by Daiichi Japan) was used as a control.

A solution of 2% was prepared by dissolving 6 g of each CMC powder of Preparation Example and Comparative Preparation Example in 294 g of distilled water.

Add distilled water to a 400 ml beaker and add a small amount of the prepared solution at a high speed of stirring for 4 minutes at 4,000 rpm, and then store it in a thermostat for 20 minutes to remove bubbles and take the spindle accurately and measure the viscosity with a Brookfield Viscometer. It was. At this time, the temperature of the CMC solution is set to 25 ℃.

Viscosity Control 275 Production Example 1 270 Production Example 2 273 Comparative Preparation Example 1 210 Comparative Production Example 2 241 Comparative Production Example 3 257 Comparative Production Example 4 219 Comparative Preparation Example 5 245 Comparative Preparation Example 6 232

From the results of Table 2, in the case of the CMC of the preparation example according to the present invention, the viscosity at 1% by weight of the aqueous solution was 270 cps or more, which was similar to that of the control CMC (HB-45: manufactured by Daiichi Japan). In the case of the production example, it was confirmed that the viscosity shows a viscosity of 245 cps or less.

The above result is also a result confirming that the CMC of the present invention can maintain or increase the lifespan characteristics of a battery manufactured as a binder for electrode mixture.

[ Test Example  3] CMC Investigation of metal content

The metal component content of CMC of the said manufacture example and CMC of the comparative manufacture examples 1-6 was investigated. The metal content was measured by inductively coupled plasma (ICP) analysis. CMC (HB-45: manufactured by Daiichi Japan) was used as a control.

Total amount of metal impurities ppm
(Fe, Al, Ca, Mg) Control 150 Production Example 1 200 Production Example 2 165 Comparative Preparation Example 1 450 Comparative Production Example 2 420 Comparative Production Example 3 250 Comparative Production Example 4 425 Comparative Preparation Example 5 350 Comparative Preparation Example 6 325

In the case of CMC of Preparation Example according to the present invention from the results of Table 3, the content of metal ions (Fe, Al, Ca, Mg) measured by ICP analysis is 200 ppm or less, and the control CMC (HB-45: Daiichi Japan). Product)), but in the case of Comparative Preparation Example it could be confirmed that it contains more than 350 ppm metal impurities.

The above result is also a result of confirming that the CMC of the present invention can improve the characteristics of a battery produced as a binder for electrode mixture and maintain or increase the lifespan characteristics of the battery.

[ Test Example  4]

The CMC of Preparation Example 2 having the best evaluated physical properties among the Preparation Examples and the CMC of Comparative Preparation Example 3 having the best evaluated physical properties among the Comparative Preparation Examples were selected, and the conventional battery was prepared including the selected CMC. The battery was manufactured by the method. CMC (HB-45: manufactured by Daiichi Japan) was used as a control.

The discharge capacity for each C-rate was measured, and the discharge efficiency was calculated by converting it into a percentage. In this case, the discharge efficiency was calculated by comparing the discharge capacity for each C-rate with respect to the initial discharge capacity (0.2C discharge capacity), which is a standard discharge capacity, and the discharge capacity for each C-rate is 0.2C, the standard discharge capacity. 0.5C, 1.0C, 2C discharge capacity, 2C discharge capacity compared to 0.2C was measured.

division Control Production Example 2 Comparative Production Example 3 0.2C Discharge capacity (mAH / g) 1332.23 1331.86 1330.25 Discharge efficiency (%) 100 100 100 0.2C contrast
0.5C discharge Discharge capacity (mAH / g) 1321.19 1321.69 1290.17 Discharge efficiency (%) 99.17 99.24 96.98 0.2C contrast
1.0C discharge Discharge capacity (mAH / g) 1320.15 1321.14 1141.03 Discharge efficiency (%) 99.09 99.20 85.76 0.2C contrast
2.0C discharge Discharge capacity (mAH / g) 1302.80 1306.60 1107.21 Discharge efficiency (%) 97.79 98.10 83.23

At this time, expressions such as 0.2C, 0.5C, 1.0C and 2.0C are used to indicate the current values of charging and discharging. In the art, 1C means charging or discharging with a current equal to a battery's rated capacity, and 0.1C means that one tenth of the battery's rated capacity is being charged or discharged.

For example, when a secondary battery having a rated capacity of 1000 mAh is charged or discharged at a current of 1000 mAh, this is called 1C charging or 1C discharge, and it is assumed that charging or discharging ends in 1 hour.

In this case, if the secondary battery having a rated capacity of 1000 mAh is charged or discharged with a current of 2000 mAh, this is called 2C charging or 2C discharge, in which case charging or discharging is completed in 30 minutes.

In addition, when the secondary battery having a rated capacity of 1000 mAh is charged or discharged at a current value of 500 mAh, it is referred to as 0.5C charging or 0.5C discharge, and in this case, the cell is brought to a predetermined current at a predetermined time as in charging in two hours. The concept of C-rate is used to indicate charging or discharging.

This means that the capacities of the currents charged or discharged at the same time are different from each other, and thus, the crate is simply defined as the current capacity ratio per hour.

That is, in the present invention, for example, 0.5C discharge capacity compared to 0.2C means the discharge capacity when discharged at 0.5C, 0.5C discharge efficiency compared to 0.2C is 0.5 when discharged at 0.2C It means the discharge efficiency compared with the discharge capacity when discharged at C. When discharged at 0.5C than discharged at 0.2C, the discharge is performed with a larger current, which means that the discharge is completed at a faster time. In other words, it means that the capacity of the current discharged within the same time is larger than 0.5C.

As can be seen from the results in Table 4, the initial charge and discharge efficiency shows that there is no significant difference in the production examples and the comparative production examples.

However, as the ratio of C-rate increases, it can be seen that the discharge efficiency is lower than that of the comparative example in the case of the comparative manufacturing example, in particular, in the case of 2.0C discharge compared to 0.2C, the discharge efficiency is significantly lower than the manufacturing example. It can be seen.

This means that as the ratio of C-rate increases to discharge with a larger current, that is, as the current consumption increases within the same time in an electronic device using a secondary battery, the capacity of a battery that can be discharged decreases. do.

[ Test Example  5]

Using the battery prepared in Test Example 4 was investigated the life (Cycle life) during charging / discharging.

Production Example 2 Control Comparative Production Example 3 0.5 C 1393.67 1398.41 1386.12 1C 1372.12 1377.64 1351.47 1C / 0.5C 98.45 98.51 97.50 100 Cycle capacity retention rate (%) 96.82% 97.36% 92.69% 150 Cycle capacity retention rate (%) 95.56% 96.16% 87.98% 200 Cycle capacity retention rate (%) 94.19% 94.68% 77.23% Expansion of electrode volume after 100 cycles (%) 691 689 -
(Active material separation)

As can be seen from the results of Table 5, the battery of the manufacturing example was confirmed that all excellent in terms of initial capacity, efficiency, cycle capacity retention rate, the initial efficiency and initial capacity was similar to the battery using the CMC of the control, the battery It was confirmed that the cycle characteristics of the similar.

The result is a result of confirming that the CMC of Preparation Example 4 has a natural function as a binder for electrode mixture, similar to the C-rate ratio of Test Example 4 carried out.

[ Test Example  6]

Based on the result of the said Test Example 5, the electrode peel test of the battery manufactured including the CMC of a manufacture example and CMC of a control (HB-45: Daiichi Japan) was performed.

A 50 μm polyimide film was bonded to both sides of the adhesive film with a hot roll laminate (80 ° C., 0.3 m / min, 0.3 MPa) by an experimental method, and cured at 170 ° C. for 1 hour. The laminated cured material was cut into width 10mm, and it produced into the evaluation sample. The value at the time of peeling at a tensile speed of 50 mm / min at the angle of 180 degree using the UTM-4-100 type Tensilon made from T0Y0 BALWIN was calculated | required. The values used two samples.

Tension drawing
(tensile Extension)
(mm) Peel strength
(N / m) Production Example 2 Electrode-G1 0.55 12.34 Electrode-G2 0.58 12.00 Control
Electrode-N1 0.60 12.80 Electrode-N2 0.61 12.50

As can be seen from the results of Table 6, it was confirmed that the CMC of the production example had a natural function as a binder for electrode mixture similarly to the CMC of the control.

From the above results, it can be seen that the CMC of the present invention has excellent binder properties for electrode mixture that overcomes reliability of quality in replacing the binder which was dependent on the existing imports.

Claims (9)

1) preparing a mixed solution by adding 1 to 30% by weight of sodium hydroxide (NaOH) having a concentration of 50% to 10 to 80% by weight of an IPA (isopropanol) and an ethanol mixture;
2) preparing an alkaline cellulose by adding 1 to 40% by weight of the natural cellulose having a weight average molecular weight (Mw) of 1,000,000 to 5,000,000 to the mixed solution;
3) preparing a reactant by adding 1 to 30% by weight of chloroacetic acid (MCA) having a concentration of 30% to the alkaline cellulose;
4) neutralizing the reaction by adding a chelating agent solution of dilute hydrochloric acid, nitric acid, or ethylenediaminetetraacetic acid (EDTA) in ethanol;
5) washing and filtering the neutralized reactants; And
6) drying the filtered reaction to obtain sodium carboxymethyl cellulose (CMC);
It has a weight average molecular weight (Mw) comprising 800,000 to 900,000, the substitution degree is 1 to 1.5, the viscosity when the aqueous solution 1% by weight is 250 to 300 cps, the content of metal ions measured by ICP analysis is 150 to Method for producing CMC for electrode mixture is 250 ppm. delete delete delete delete delete delete delete The secondary battery electrode, characterized in that it comprises a sodium carboxymethyl cellulose (CMC) according to claim 1.

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