KR-102962587-B1 - POSITIVE ELECTRODE SLURRY COMPOSITION FOR LITHIUM SECONDARY BATTERY, POSITIVE ELECTRODE AND LITHIUM SECONDARY BATTERY COMPRISING THE SAME

KR102962587B1KR 102962587 B1KR102962587 B1KR 102962587B1KR-102962587-B1

Abstract

The present invention relates to a positive electrode slurry composition for a lithium secondary battery, a positive electrode, and a lithium secondary battery including the same. More specifically, when manufacturing a positive electrode for a lithium secondary battery including a slurry coating process, the processability of manufacturing a positive electrode for a lithium secondary battery can be increased by using a positive electrode slurry composition having thixotropy that can secure flowability sufficient to flexibly respond to changes in the slurry coating speed when manufacturing a positive electrode for a lithium secondary battery.

Inventors

이충현
김택경
최란

Assignees

주식회사 엘지에너지솔루션

Dates

Publication Date: 20260507
Application Date: 20210708

Claims (12)

It comprises a positive electrode active material, a conductive material, a binder, a thickener, an additive, and a solvent, wherein The above-mentioned thickener comprises lithiated carboxymethyl cellulose (LiCMC), and The above additive is a positive electrode slurry composition for a lithium secondary battery comprising a carbodiimide-based compound, wherein The above-mentioned cathode active material comprises one or more selected from the group consisting of elemental sulfur ( S8 ), Li2Sn (n ≥ 1, where n is an integer), organic sulfur compounds, and carbon-sulfur polymers [( C2Sx ) n , 2.5 ≤ x ≤ 50, n ≥ 2, where x and n are integers], and A positive electrode slurry composition for a lithium secondary battery, wherein the above positive electrode slurry composition has a thixotropic index (T) represented by the following mathematical formula 1 of 0.1 to 0.4: <Mathematical Formula 1> Tixotropy index (T) = (viscosity of anode slurry composition at a rotational speed of 10 rpm) / (viscosity of anode slurry composition at a rotational speed of 1 rpm), The above viscosity was measured at 25℃.
In paragraph 1, A positive electrode slurry composition for a lithium secondary battery, wherein the above-mentioned carbodiimide compound comprises one or more selected from the group consisting of 1-ethyl-3-[3-(dimethylamino)propyl]-carbodiimide hydrochloride (EDC), 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide, N,N'-diisopropylcarbodiimide, and N,N'-di-tert-butylcarbodiimide.
In paragraph 1, A positive electrode slurry composition for a lithium secondary battery, wherein the above-mentioned thickener is included in an amount of 0.5% to 5% by weight based on the total weight of the solid content of the above-mentioned positive electrode slurry composition.
In paragraph 1, A positive electrode slurry composition for a lithium secondary battery, wherein the above additive is included in an amount of 0.01% to 5% by weight based on the total weight of the solid content of the positive electrode slurry composition.
In paragraph 1, The above solvent may include one or more selected from organic solvents and aqueous solvents, and The above organic solvent comprises one or more selected from the group consisting of N-methyl-2-pyrrolidone (NMP), methoxypropyl acetate, butyl acetate, glycol acid, butyl ester, butyl glycol, methylalkylpolysiloxane, alkylbenzene, propylene glycol, xylene, monophenyl glycol, aralkyl-modified methylalkylpolysiloxane, polyether-modified dimethylpolysiloxane copolymer, polyether-modified dimethylpolysiloxane copolymer, polyacrylate, alkylbenzene, diisobutyl ketone, organic-modified polysiloxane, butanol, isobutanol, modified polyacrylate, modified polyurethane, and polysiloxane-modified polymer. A positive electrode slurry composition for a lithium secondary battery, wherein the above-mentioned aqueous solvent comprises water.
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A positive current collector; and a positive active material layer formed on one surface of the positive current collector, comprising: A positive electrode for a lithium secondary battery, wherein the positive electrode active material layer is formed from the positive electrode slurry composition of claim 1.
(S1) A step of coating the anode slurry composition of claim 1 onto one surface of an anode current collector; (S2) A step of drying the coating layer formed in the above (S1) step; and (S3) A step of rolling the coating layer to form an anode active material layer; comprising a method for manufacturing an anode for a lithium secondary battery according to claim 8.
In Paragraph 9, A method for manufacturing a positive electrode for a lithium secondary battery, wherein the above coating method is one or more selected from the group consisting of bar coating, roll-to-roll coating, spin coating, nozzle printing, inkjet printing, slot coating, and dip coating.
A lithium secondary battery comprising a positive electrode, a negative electrode, a separator, and an electrolyte according to paragraph 8.
In Paragraph 11, The above lithium secondary battery is a lithium secondary battery, which is a lithium-sulfur secondary battery.

Description

Positive ELECTRODE SLURRY COMPOSITION FOR LITHIUM SECONDARY BATTERY, POSITIVE ELECTRODE AND LITHIUM SECONDARY BATTERY COMPRISING THE SAME The present invention relates to a positive electrode slurry composition for a lithium secondary battery, a positive electrode, and a lithium secondary battery comprising the same. The demand for rechargeable batteries is increasing due to the rapid recent advancements in the fields of electronic devices and electric vehicles. In particular, as portable electronic devices become smaller and lighter, there is a growing demand for rechargeable batteries with high energy density to meet these demands. Among secondary batteries, lithium-sulfur secondary batteries are batteries that use a sulfur-based compound having sulfur-sulfur bonds as the positive electrode active material, and a carbon-based material in which the insertion and extraction of metal ions such as lithium or alkali metals, or lithium ions, occur, or silicon or tin that form an alloy with lithium as the negative electrode active material. Specifically, the lithium-sulfur secondary battery stores and generates electrical energy by utilizing an oxidation-reduction reaction in which the sulfur-sulfur bonds break and the oxidation number of sulfur decreases during discharge, which is a reduction reaction, and the oxidation number of sulfur increases and the sulfur-sulfur bonds are reformed during charging, which is an oxidation reaction. In particular, sulfur, which is used as a cathode active material in lithium-sulfur secondary batteries, has a theoretical energy density of 1,675 mAh/g, which is about five times higher than that of cathode active materials used in conventional lithium secondary batteries, making it a battery capable of exhibiting high power and high energy density. In addition, sulfur is attracting attention as an energy source for medium-to-large devices such as electric vehicles as well as portable electronic devices due to its advantages of being inexpensive, having abundant reserves for easy supply, and being environmentally friendly. Sulfur is an insulator with no electrical conductivity, with an electrical conductivity of about 5 x 10⁻³⁰ S/cm, so there is a problem with the movement of electrons generated by electrochemical reactions. Therefore, it is combined with an electrically conductive material such as carbon, which can provide electrochemical reaction sites, and is used as a sulfur-carbon composite. In order to use the above sulfur-carbon composite as a cathode material, a method of manufacturing a cathode through a slurry process in which a slurry is prepared using the above sulfur-carbon composite, a conductive material, a binder, and a thickener, and then the slurry is applied to a current collector is generally used. However, conventional cathode slurries for lithium-sulfur secondary batteries have low thixotropy, so sufficient flowability is not guaranteed when the cathode slurry is applied to a solution coating process. Accordingly, when manufacturing the cathode slurry, a dispersion agent and/or rheology modifier that are affinity to the sulfur-carbon composite, which is the cathode active material, are sometimes used; however, even if these are used, there is no significant change in flowability, and rather, the charge/discharge performance is weakened by the use of the said dispersion agent and/or rheology modifier. Meanwhile, recently, research results have been disclosed regarding the improvement of the flowability of the anode slurry by applying a carboxymethylcellulose-based material as a binder when manufacturing the anode composition. For example, Korean Published Patent No. 2016-0071740 includes carboxymethylcellulose (CMC) as a binder when preparing the anode composition to provide a water-based anode composition for imparting stable and flexible electrode plate characteristics. However, when only carboxymethylcellulose is used as a binder, the slurry with low thixotropy does not spread properly when the coating speed changes during the slurry coating process, which causes a problem in that the anode active material layer cannot be formed uniformly. Lei Qui et al. (Carbohydrate polymers, Vol.112, (2014) pp.532-538) disclose a cathode composition for a lithium secondary battery comprising lithiated carboxymethyl cellulose (LiCMC) as a binder. However, when only lithiated carboxymethyl cellulose is used as a binder, the thixotropy is weak during the preparation of the cathode slurry, and thus the cathode composition cannot adequately respond to changes in the coating speed during the cathode active material layer coating process, resulting in a problem where the cathode active material layer cannot be formed uniformly. As such, research is being conducted to improve the rheological properties of cathode slurries in order to enhance processability during the manufacturing of cathodes for lithium secondary batteries and to improve the charge-discharge performance of the