KR20140140980A - Electrode for lithium secondary battery and lithium secondary battery comprising the same - Google Patents

Abstract

The present invention relates to an electrode active material slurry including a) an electrode active material, b) a conductive material, c) a binder, and d) a thickener. The thickener includes: a first cellulose-based compound of which the weight average molecular weight is 500, 000 or greater and less than 2,000,000; and a second cellulose-based compound of which the weight average molecular weight is 100,000 or greater and less than 500,000.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrode for a lithium secondary battery and a lithium secondary battery including the electrode,

The present invention relates to an electrode for a lithium secondary battery comprising as a thickener two or more kinds of cellulosic compounds having different weight average molecular weights and a lithium secondary battery having improved capacity and rate characteristics.

As technology development and demand for mobile devices increase, the demand for batteries as energy sources is rapidly increasing. Accordingly, a variety of researches on batteries that can meet various demands have been conducted.

Examples of the battery include a prismatic secondary battery and a pouch type secondary battery in terms of form, and a lithium secondary battery such as a lithium ion battery or a lithium ion polymer battery having high energy density, discharge voltage, and output stability in terms of material.

The lithium secondary battery includes a positive electrode and a negative electrode, and a separator interposed therebetween. The positive electrode and the negative electrode may be formed by coating an electrode active material slurry in which electrode active material particles and a binder are dispersed in a solvent directly on a current collector and drying or coating the electrode active material slurry on an upper portion of a separate support, And a film is laminated on the current collector.

In order to facilitate the coating process, it is necessary to control the viscosity of the electrode active material slurry. The viscosity, the solid concentration, the thickness of the coating layer, the evaporation rate of the solvent at the coating rate, and the evaporation rate of the solvent all organically influence each other.

Recently, studies have been made to prepare an electrode active material slurry having improved viscosity and dispersibility, an electrode for a lithium secondary battery using the same, and a lithium secondary battery.

The present invention provides an electrode active material slurry comprising at least two cellulosic compounds having different weight average molecular weights as thickening agents.

Also, the present invention provides an electrode for a lithium secondary battery having improved electrochemical characteristics by including the slurry of the electrode active material, and a lithium secondary battery comprising the same.

The present invention provides an electrode active material slurry comprising at least two cellulosic compounds having different weight average molecular weights as thickening agents.

Specifically, in the present invention,

The electrode active material slurry includes a) an electrode active material, b) a conductive material, c) a binder, and d) a thickening agent,

The d) thickener includes a first cellulosic compound having a molecular weight of 500,000 or more and less than 2,000,000 and a second cellulosic compound having a molecular weight of 100,000 or more and less than 500,000.

The mixing ratio of the first cellulosic compound: the second cellulose compound in the thickener is preferably 2.0 to 85%: 98 to 25% by weight.

Further, in the present invention, And

And the electrode active material layer formed on the metal current collector.

The present invention also provides a secondary battery including the electrode for the lithium secondary battery.

In the present invention, an electrode active material slurry improved in solidification, coating stabilization, and dispersibility improvement effects is prepared by containing two or more kinds of cellulose compounds different in weight average molecular weight (Mw) as a thickener, This improved lithium secondary battery electrode and a lithium secondary battery including the same can be manufactured.

Hereinafter, the present invention will be described in detail in order to facilitate understanding of the present invention. Herein, terms and words used in the present specification and claims should not be construed to be limited to ordinary or dictionary meanings, and the inventor may appropriately define the concept of the term to describe its own invention in the best way. It should be construed as meaning and concept consistent with the technical idea of the present invention.

Electrode active material Slurry  Produce

At present, it is the resistance characteristic of the battery that determines the output performance of the lithium secondary battery. This resistance characteristic is greatly influenced by the dispersion state of the materials in the anode or cathode active material. For example, when the active material, the conductive material and the binder existing in the active material layer do not have a uniform dispersion state, they are likely to be ruptured, and a channel through which current can flow in the electrode is not formed locally, Or a current concentration phenomenon may occur, thereby deteriorating the performance and stability of the battery. Furthermore, the electrode may be ruptured during the manufacture of the electrode.

Therefore, in preparing an electrode for a lithium secondary battery, it is essential to control the dispersibility and viscosity of the electrode active material slurry.

The binder functions not only to bond the negative electrode active material particles together but also to maintain the binding between the negative electrode active material particles and the current collector, and it is possible to prevent the electrode from rupturing by giving an excellent adhesive force. As a typical example of such a binder, a styrene butadiene rubber (SBR) aqueous binder using water as a dispersion medium is known.

Further, the use of carboxymethyl cellulose (CMC) as a thickening agent in the preparation of slurries for the positive and negative electrode active materials has the advantage of not only stabilizing the viscosity of the upper and lower portions of the solution but also improving the dispersibility.

However, when the above-mentioned thickener is used, it is difficult to obtain a uniform dispersibility due to the difference in specific gravity between the electrode active material and the conductive material, and the amount of the solvent (water) is increased due to the increase of the viscosity with the increase of the content of the thickener in the electrode active material slurry Not only the amount of solid content precipitated in the slurry decreases but also the content of the electrode active material in the slurry is decreased due to an increase in the amount of the thickener used, so that the electrode capacity decreases and the battery characteristics deteriorate.

Accordingly, in the present invention, it is possible to provide an electrode active material slurry having uniform dispersibility and improved viscosity by containing two or more kinds of cellulose compounds having different average molecular weights (Mw) as thickening agents.

Specifically, in one embodiment of the present invention

1. An electrode active material slurry comprising a) an electrode active material, b) a conductive material, c) a binder, and d) a thickening agent,

And d) a first cellulosic compound having a viscosity of less than 500,000 and less than 2,000,000 and a second cellulosic compound having a molecular weight of less than 100,000 and less than 500,000.

In the electrode active material slurry of the present invention, (a) The electrode active material may be a positive electrode active material or a negative electrode active material, specifically, a negative electrode active material. The electrode active material may include about 80 to 97% by weight based on the total weight of the electrode active material slurry.

At this time, the cathode active material may include a manganese-based spinel active material, a lithium metal oxide, or a mixture thereof. Further, the lithium metal oxide may be selected from the group consisting of a lithium-manganese-based oxide, a lithium-nickel-manganese-based oxide, a lithium-manganese-cobalt oxide, and a lithium-nickel-manganese-cobalt oxide, is _{LiCoO 2, LiNiO 2, LiMnO 2} , LiMn 2 O 4, Li 1 + x (Ni a Mn b Co 1 -abx) O 2 (-0.1≤x≤0.1,0≤a≤1, x + a + b = 1) or Li _{1 + x} (Mn _2-xy Co _y ) O ₄ (-0.1 _{? X?} 0.1, _{0 ? Y? 2} ), LiNi _{1 -Y} Co _Y O ₂ , LiCo _{1 -Y} Mn _Y O ₂ , LiNi _{1 - Y} Mn _Y O ₂ (Where 0? Y <1), LiMn _{2 - z} Ni _z O ₄ , LiMn _{2 - z} Co _z O ₄ (Where 0 &lt; Z &lt; 2).

The negative electrode active material may be a carbonaceous negative electrode active material such as crystalline carbon, amorphous carbon, or carbon composite. The carbonaceous negative electrode active material may be used alone or as a mixture of two or more thereof. Preferably, the carbonaceous active material is graphite, such as natural graphite and artificial graphite, Carbon.

In the slurry of the electrode active material of the present invention, the conductive material (b) is not particularly limited as long as it has conductivity without causing side reactions with other elements of the battery. For example, natural graphite, artificial graphite, Carbon black, carbon black, carbon black, carbon black, carbon black, carbon black, carbon black, carbon black, ketjen black, channel black, furnace black, lamp black, summer black, carbon nanotubes, fullerene, Phenylene derivatives, or a mixture of two or more thereof. The conductive material is usually included in an amount of 0.05 to 3 parts by weight based on 100 parts by weight of the active material powder.

In the electrode active material slurry of the present invention, the binder (c) is a component for binding the active material particles in the electrode active material slurry and holding the formed body, and may specifically include an aqueous binder such as styrene-butadiene rubber But are not limited to, for example, vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HEP), polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, polyvinyl alcohol, poly (EPDM), sulfonated EPDM, polytetrafluoroethylene (PTFE), and polyvinylidene fluoride (PVdF), as well as polyvinyl pyrrolidone, polyethylene, tetrafluoroethylene, polypropylene, polyacrylic acid, ethylene-propylene-diene monomer And at least one non-aqueous binder selected from the group consisting of acrylonitrile-butadiene rubber or styrene-butadiene rubber One or more kinds of aqueous binders selected from the group consisting of rubber and acrylic rubber may be used alone or in combination. It is more preferable that the water-based binder has a larger binding effect than the non-aqueous binder and can increase the proportion of the active material of the same volume so that an aqueous binder capable of high capacity can be used in combination.

If the content of the SBR binder is less than 1.0% by weight, the electrode active material may be detached. If the amount of the binder exceeds 2.0% by weight, the binder may be contained in an amount of 1.0 to 2.0% by weight based on the total weight of the active material slurry. Battery performance may be degraded.

In the slurry of the electrode active material of the present invention, the cellulose compound based on two or more weight average molecular weights (Mw), which is the thickener (d), is a water-soluble polymer component included in order to improve the solid content- Is high and excellent in coating property and is excellent in adhesive force, it is possible to prevent the active material from falling off from the current collector and to achieve excellent performance characteristics of the battery.

The one cellulosic compound having a molecular weight of 500,000 or more and less than 2,000,000 may be exemplified by carboxymethyl cellulose (CMC), and examples thereof include methylcellulose, ethylcellulose, hydroxyethyl (CMCNa), or at least one selected from the group consisting of cellulose, benzyl cellulose, trityl cellulose, cyanoethyl cellulose, carboxyethyl cellulose, aminoethyl cellulose, nitrocellulose, cellulose ether and carboxymethylcellulose sodium salt And mixtures thereof.

The second cellulosic compound having a molecular weight of 100,000 or more and less than 500,000 can be exemplified by carboxymethyl cellulose (CMC), such as methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, benzyl cellulose, trityl cellulose, Ethylcellulose, carboxyethylcellulose, aminoethylcellulose, nitrocellulose, cellulose ether, and carboxymethylcellulose sodium salt (CMCNa), or a mixture of two or more thereof.

That is, the first and second cellulose-based compounds are all CMC, or the same cellulose-based compounds may be used, or different cellulosic-based compounds may be used.

At this time, the mixing ratio of the first cellulosic compound: the second cellulose compound in the thickener may be 2.0 to 85% by weight: 98 to 25%.

The ratio of the total content of the two or more kinds of cellulose compounds having different average molecular weights (Mw) as the binder: thickener in the electrode active material slurry may be 1 to 3: 1 by weight.

If the total content of the binder: cellulose compound is less than 1: 1, the binding strength of the electrode and the phase stability of the electrode active material slurry can not be improved. If the ratio is more than 3: 1, They may not be in a dispersed state and may clump. In this case, a channel through which an electric current can flow in the electrode is not locally formed, so that the resistance inside the battery increases, or current concentration phenomenon occurs, which may hinder the performance and stability of the battery.

, And the degree of substitution (DS) of the first cellulosic compound and the second cellulose compound may be 1.1 to 1.3, respectively. If the degree of substitution of the first and second cellulose compounds is more than 1.3, the dispersibility of the inorganic particles such as the active material and the conductive agent may be deteriorated and the cohesive force may be weak, so that the performance of the battery may be weakened.

At this time, as the average number of substitution groups substituted on the cellulose per repeating unit of cellulose, the solubility of the cellulose compound in water may vary depending on the degree of substitution. In general, when the cellulose compound has a high degree of substitution, the solubility in water increases, and when the degree of substitution is low, the solubility in water decreases. For example, the higher the degree of substitution, the more ionized portions (increased solubility), the easier the network formation, and thus the inorganic particles such as the negative electrode active material and the conductive agent are uniformly dispersed and uniformly coated on the entire surface of the metal collector. The solubility of the cellulose compound in water may affect the dispersion characteristics of the electrode active material slurry. The better the solubility in water, the better the dispersibility of the electrode active material slurry. Also, if the dispersibility of the electrode active material slurry is improved, the solid content ratio can be increased under the same viscosity. Further, if the dispersibility of the electrode active material slurry is improved, the solid content ratio can be increased under the same viscosity. When an electrode is manufactured using the electrode active material slurry thus prepared, a smooth current flow can be formed inside the electrode.

As described above, the electrode active material slurry of the present invention can prevent agglomeration of the negative electrode slurry by containing two or more kinds of cellulosic compounds having different weight average molecular weights (Mw) as thickening agents, for example, a first cellulosic compound having a high weight average molecular weight And a second cellulosic compound having a low weight average molecular weight, it is possible to obtain a uniform high viscosity mixing effect between the conductive material and the active material to obtain uniform dispersion and viscosity of the electrode active material slurry, .

Electrode Manufacturing

In an embodiment of the present invention,

Metal collectors; And an electrode active material layer of the present invention formed on the metal current collector.

The electrode may include both an anode and a cathode, and may be specifically a cathode.

The electrode of the present invention can be produced by a conventional method known in the art. For example, the electrode active material slurry can be coated (coated) on a current collector of a metal material, compressed and dried to produce an electrode.

According to one embodiment of the present invention, the electrode active material slurry requires a solvent to form an electrode, and examples of the solvent that can be used include NMP (N-methylpyrrolidone), DMF (dimethylformamide) Acetamide and the like, or water, and these solvents may be used alone or in combination of two or more. However, when a negative electrode is formed, water is used as a solvent. The amount of the solvent used is sufficient to dissolve and disperse the electrode active material, the binder and the conductive agent in consideration of the coating thickness of the electrode active material slurry and the production yield.

The current collector of the metal material may be any metal that has high conductivity and can easily adhere to the slurry of the electrode active material and is not reactive in the voltage range of the battery. Non-limiting examples of the positive electrode current collector include aluminum, nickel, or a foil produced by a combination of these. Non-limiting examples of the negative electrode current collector include copper, gold, nickel, or a copper alloy or a combination thereof Foil and so on.

Secondary battery manufacturing

According to an embodiment of the present invention, there is provided a secondary battery including the electrode.

The lithium secondary battery of the present invention may include all conventional lithium secondary batteries such as a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery, or a lithium ion polymer secondary battery.

Since the lithium secondary battery includes an electrode having excellent adhesion of the active material powder to the metal current collector and excellent bonding property between the active material powders, it is possible to prevent the active material powder from falling off due to the volume change of the active material powder during charging and discharging, The capacity deterioration accompanying the cycle can be prevented. Also, since the amount of the binder which is nonconductive in the electrode can be reduced, the impedance of the electrode is reduced, thereby improving the high-rate current characteristics of the battery.

The lithium secondary battery of the present invention can be produced by a conventional method known in the art. For example, a porous separator may be placed between the anode and the cathode, and a non-aqueous electrolyte may be added.

The separator may be a porous polymer film such as a porous polymer film made of a polyolefin-based polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, or an ethylene / methacrylate copolymer Or may be a laminate of two or more kinds. In addition, nonwoven fabrics made of conventional porous nonwoven fabrics, for example, glass fibers having a high melting point, polyethylene terephthalate fibers, or the like can be used, but the present invention is not limited thereto.

The lithium salt that can be included in the non-aqueous electrolyte used in the present invention may be any of those commonly used in an electrolyte for a lithium secondary battery, and examples thereof include F ^- , Cl ^- , Br ^- , I ^{- _{, NO 3 -, N (CN}} ) 2 -, BF 4 -, ClO 4 -, PF 6 -, (CF 3) 2 PF 4 -, (CF 3) 3 PF 3 -, (CF 3) 4 PF 2 - ^{_{, (CF 3) 5 PF -}} , (CF 3) 6 P -, CF 3 SO 3 -, CF 3 CF 2 SO 3 -, (CF 3 SO 2) 2 N -, (FSO 2) 2 N -, CF _{3 CF 2 (CF 3) 2} CO -, (CF 3 SO 2) 2 CH -, (SF 5) 3 C -, (CF 3 SO 2) 3 C -, CF 3 (CF 2) 7 SO 3 -, CF ₃ CO ₂ ^- , CH ₃ CO ₂ ^- , SCN ^-, and (CF ₃ CF ₂ SO ₂ ) ₂ N ^- .

The external shape of the lithium secondary battery of the present invention is not particularly limited, but may be a cylindrical shape, a square shape, a pouch shape, a coin shape, or the like using a can.

The lithium secondary battery of the present invention can be used as a power source for various electronic products. For example, a portable telephone, a mobile phone, a game machine, a portable television, a notebook computer, a calculator, and the like, but is not limited thereto.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail with reference to examples. However, the embodiments according to the present invention can be modified into various other forms, and the scope of the present invention should not be construed as being limited to the embodiments described below. The embodiments of the present invention are provided to enable those skilled in the art to more fully understand the present invention.

Example

&Lt; Anode active material Slurry  Manufacturing>

(Example 1)

Sintered graphite and scaly graphite were mixed in a weight ratio of 9: 1 as an anode active material to prepare an anode active material. Subsequently, the prepared carboxymethylcellulose having a weight average molecular weight of 900,000 as a negative active material, a conductive material (spherical and flake graphite having a particle diameter of 30 nm), a binder (SBR) and a thickener, and a second carboxyimide having a weight average molecular weight of 140,000 Methyl cellulose (75: 25 weight ratio) were mixed at a weight ratio of 97: 1: 1: 1 and mixed with water (H ₂ O) as a solvent to prepare a uniform negative electrode active material slurry. The viscosity of the negative electrode active material slurry was 2850 cps.

(Example 2)

Sintered graphite and scaly graphite were mixed in a weight ratio of 9: 1 as an anode active material to prepare an anode active material. Subsequently, the prepared carboxymethylcellulose having a weight average molecular weight of 1,260,000 as a negative active material, a conductive material (spherical and flake graphite having a particle size of 30 nm), a binder (SBR) and a thickener, and a second carboxyimide having a weight average molecular weight of 140,000 Methyl cellulose (75: 25 weight ratio) were mixed at a weight ratio of 97: 1: 1: 1 and mixed with water (H ₂ O) as a solvent to prepare a uniform negative electrode active material slurry. The viscosity of the negative electrode active material slurry was 2620 cps.

(Example 3)

Sintered graphite and scaly graphite were mixed in a weight ratio of 9: 1 as an anode active material to prepare an anode active material. Subsequently, the obtained first negative electrode active material, conductive material (spherical and flake graphite having a particle diameter of 30 nm), binder (SBR), and a thickening agent, a first carboxymethyl cellulose having a weight average molecular weight of 1,800,000 and a second carboxy Methyl cellulose (75: 25 weight ratio) were mixed at a weight ratio of 97: 1: 1: 1 and mixed with water (H ₂ O) as a solvent to prepare a uniform negative electrode active material slurry. The viscosity of the negative electrode active material slurry was 3300 cps.

(Comparative Example 1)

Sintered graphite and scaly graphite were mixed in a weight ratio of 9: 1 as an anode active material to prepare an anode active material. Subsequently, carboxymethylcellulose having a weight average molecular weight (Mw) of 1,800,000 as a binder and a spherical and flinty graphite having a particle size of 30 nm as a conductive agent, SBR as a binder and carboxymethylcellulose having a weight ratio of 97: 1: 1: 1 And mixed with water (H ₂ O) as a solvent to prepare a uniform negative electrode active material slurry. The viscosity of the negative electrode active material slurry was 3500 cps.

(Comparative Example 2)

Sintered graphite and scaly graphite were mixed in a weight ratio of 9: 1 as an anode active material to prepare an anode active material. SBR and carboxymethyl cellulose having a weight average molecular weight (Mw) of 140,000 were mixed in a weight ratio of 97: 1: 1: 1 as a binder, a negative electrode active material, a spherical and flinty graphite having a particle size of 30 nm as a conductive agent, And they were mixed together with water (H ₂ O) as a solvent to prepare a uniform negative electrode active material slurry. The viscosity of the negative electrode active material slurry was 1650 cps.

&Lt; Production of lithium secondary battery >

(Example 4)

The negative electrode active material slurry prepared in Example 1 was coated on a copper (Cu) thin film as an anode current collector having a thickness of 10 mu m and dried to produce a negative electrode, followed by roll pressing to produce a negative electrode .

(NMP) as a solvent, 96 wt% of LiCoO ₂ as a positive electrode active material, 3 wt% of carbon black as a conductive agent, and 3 wt% of polyvinylidene fluoride (PVdF) To prepare a positive electrode mixture slurry. The positive electrode mixture slurry was applied to an aluminum (Al) thin film having a thickness of about 20 탆 and dried to produce a positive electrode, followed by a roll press to prepare a positive electrode.

A polyolefin separator was interposed between the positive electrode and the negative electrode, and then an electrolyte in which 1 M LiPF ₆ was dissolved was injected into a solvent in which ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed at a volume ratio of 30:70, A secondary battery was manufactured.

(Example 5)

A coin-type lithium secondary battery was prepared in the same manner as in Example 5 except that the slurry of the negative electrode active material prepared in Example 2 was used in place of the slurry of the negative electrode active material prepared in Example 1.

(Example 6)

A coin-type lithium secondary battery was prepared in the same manner as in Example 5 except that the slurry of the negative electrode active material prepared in Example 3 was used in place of the slurry of the negative electrode active material prepared in Example 1.

(Comparative Example 3)

A coin type lithium secondary battery was prepared in the same manner as in Example 5 except that the slurry of the negative electrode active material prepared in Comparative Example 1 was used in place of the slurry of the negative electrode active material prepared in Example 1.

(Comparative Example 4)

A coin-type lithium secondary battery was prepared in the same manner as in Example 5, except that the slurry of the negative electrode active material prepared in Comparative Example 2 was used in place of the slurry of the negative electrode active material prepared in Example 1.

Experimental Example

Experimental Example  1: anode active material Slurry  Sedimentation measurement

150 ml of each of the negative electrode active material slurries prepared in Examples 1 to 3 and Comparative Examples 1 and 2 was placed in a 200 ml glass bottle and the time for 10% solids to settle was measured based on the total slurry volume, Respectively.

Settling time (hr) Example 1 21 Example 2 22 Example 3 24 Comparative Example 1 18 Comparative Example 2 2

Experimental Example  2: Capacity and efficiency characteristics of lithium secondary battery

The cells prepared in Examples 4 to 6 and Comparative Examples 3 and 4 were charged to a constant current (0.5 C) to 5 mV and then charged at 5 mV until the current reached 0.005 C and then terminated. The discharge of the battery was discharged at a constant current (0.5 C) to 1.0 V. The capacitance (dQ / dV) after the first charging / discharging was measured and the results are shown in Table 2 below.

1 ^st charge / discharge result dQ / dV (reduction peak differential amount) Capacity (mAh / g) efficiency (%) Example 4 365 94.8 -38 Example 5 360 93.5 -36 Example 6 364 94.3 -36 Comparative Example 3 357 92.1 -60 Comparative Example 4 359 91.0 -50

As shown in Table 2, in the case of the batteries of Examples 4 to 6 containing two or more kinds of cellulosic compounds different in weight average molecular weight (Mw) according to the present invention, in Comparative Examples 3 and 4 using carboxymethylcellulose alone It was found that the capacity and efficiency of the lithium secondary battery were superior to those of the battery.

Experimental Example 3: Capacity and Efficiency of Lithium Secondary Battery

The batteries prepared in Examples 4 to 6 and Comparative Example 2 prepared above were charged at 25 ° C until the constant voltage (CV) of 1.0 V and the constant current (CC) of 1/20 V were reached. Thereafter, the battery was allowed to stand for 10 minutes and then discharged at a constant current of 1 C until it reached 1.5 V to measure the discharge capacity of the first cycle. The discharge capacity was measured by charging and discharging at 1.0 C and by varying charge and discharge conditions. The results are shown in Table 3 below.

5.0 C charge CC time (hour) ^A Discharge 0.2C 1.0C ^B efficiency(%) Example 4 1.38 368 352 95.6 Example 5 1.22 366 346 94.5 Example 6 1.37 365 345 94.5 Comparative Example 3 0.60 356 314 88.2 Comparative Example 4 0.70 357 323 89.3

 Referring to Table 3, in the batteries of Examples 4 to 6, the time for a constant current (CC) of 1.0 C was 1 hour or more, and that of Comparative Examples 3 and 4 was 1 hour or less. In the case of 0.2 C, there was no significant difference in the initial discharge characteristics. However, in the case of 1.0 C, the batteries of Examples 4 to 6 were remarkably excellent and the discharging efficiency was 90% or more in the batteries of Examples 4 to 6 It can be confirmed that it is remarkably superior to Examples 3 and 4.

Claims (15)

1. An electrode active material slurry comprising a) an electrode active material, b) a conductive material, c) a binder, and d) a thickening agent,
Wherein the thickener comprises a first cellulosic compound having a weight average molecular weight of 500,000 or more and less than 2,000,000 and a second cellulosic compound having a weight average molecular weight of 100,000 or more and less than 500,000. The method according to claim 1,
Wherein the electrode active material comprises about 80 to 97% by weight based on the total weight of the electrode active material slurry. The method according to claim 1,
Wherein the conductive material comprises 0.05 to 3 parts by weight based on 100 parts by weight of the electrode active material powder. The method according to claim 1,
Wherein the binder is a styrene-butadiene-based rubber. The method of claim 4,
The binder is selected from the group consisting of vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HEP), polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, polyvinyl alcohol, polyvinyl pyrrolidone, polyethylene , A single substance selected from the group consisting of tetrafluoroethylene, polypropylene, polyacrylic acid, ethylene-propylene-diene monomer (EPDM), sulfonated EPDM, polytetrafluoroethylene (PTFE) and polyvinylidene fluoride Or a mixture of two or more thereof. The method according to claim 1,
Wherein the binder comprises 1.0 to 2.0% by weight based on the total weight of the electrode active material slurry. The method according to claim 1,
The first cellulosic compound may be selected from the group consisting of carboxymethylcellulose (CMC), methylcellulose, ethylcellulose, hydroxyethylcellulose, benzylcellulose, tritethylcellulose, cyanoethylcellulose, carboxyethylcellulose, aminoethylcellulose, nitrocellulose, And carboxymethylcellulose sodium salt (CMCNa). 2. The electrode active material slurry as claimed in claim 1, The method according to claim 1,
The second cellulosic compound may be selected from the group consisting of carboxymethylcellulose (CMC), methylcellulose, ethylcellulose, hydroxyethylcellulose, benzylcellulose, tritylcellulose, cyanoethylcellulose, carboxyethylcellulose, aminoethylcellulose, nitrocellulose, And carboxymethylcellulose sodium salt (CMCNa), or a mixture of two or more thereof. The method according to claim 1,
Wherein the mixing ratio of the first cellulosic compound: the second cellulosic compound is from 2.0 to 85% by weight: 98 to 25%. The method according to claim 1,
Wherein the weight ratio of the binder to the thickener in the electrode active material slurry is 1 to 3: 1 by weight. The method according to claim 1,
Wherein the substitution degree of the first cellulosic compound in the thickener is 1.1 to 1.3 and the degree of substitution of the second cellulosic compound is 1.1 to 1.3. Metal collectors; And
An electrode active material slurry layer according to claim 1 formed on the metal current collector. The method of claim 12,
Wherein the electrode active material slurry is a positive electrode active material slurry or a negative electrode active material slurry. A secondary battery comprising the electrode according to claim 12. 15. The method of claim 14,
Wherein the secondary battery is a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery, or a lithium ion polymer secondary battery.