US-20260128309-A1 - Cathode Slurry Composition, Cathode for Secondary Battery and Lithium Secondary Battery

Abstract

A cathode slurry composition according to an aspect includes a cathode active material, an acrylic dispersant, and a solvent. The cathode slurry composition has a solids content of 65% by weight or more, and a shear viscosity value of 150 Pa·s or less measured at a temperature of 25° C. and a shear rate of 1/s. According to the aspect, a cathode slurry composition having excellent dispersibility, flowability, and the like, as aggregation between cathode active material particles is suppressed, and having a relatively high solids content and low shear viscosity may be provided. According to the cathode slurry composition, a cathode for a secondary battery may be formed having excellent processability without limitations on electrode loading design, coating speed setting, and the like.

Inventors

• Byoung Ho KO

Assignees

• SK ON CO., LTD.

Dates

Publication Date

20260507

Application Date

20260107

Priority Date

20221129

Claims (10)

1. 1 . A cathode slurry composition comprising: a cathode active material, an acrylic dispersant, and a solvent, wherein the cathode active material has an average particle diameter (D50) of less than 5 μm, wherein, in the cathode slurry composition, a solids content is 65% by weight or more, a shear viscosity value measured at a temperature of 25° C. and a shear rate of 1/s is 150 Pa·s or less, and wherein an R PA value according to Equation 1 below is 1.2 or less, R PA = | ( PA 0 - PA 1 ) | / PA 0 [ Equation ⁢ 1 ] in Equation 1, R PA is a change rate in a phase angle before and after shearing of a slurry, PA 0 is a phase angle (°) of a slurry before shearing, and PA 1 is a phase angle (°) of a slurry after shearing.
2. 2 . The cathode slurry composition of claim 1 , wherein the acrylic dispersant comprises a polyacrylate-based compound.
3. 3 . The cathode slurry composition of claim 1 , wherein the acrylic dispersant is included in an amount of 0.1 to 10% by weight based on a solids content.
4. 4 . The cathode slurry composition of claim 1 , wherein the cathode active material comprises a lithium iron phosphate-based (LFP) active material.
5. 5 . The cathode slurry composition of claim 1 , further comprising: a conductive material dispersion.
6. 6 . The cathode slurry composition of claim 5 , wherein the conductive material dispersion comprises an additional acrylic dispersant.
7. 7 . A cathode for a secondary battery, wherein the cathode slurry for a secondary battery is formed of the cathode slurry composition according to claim 1 .
8. 8 . The cathode for a secondary battery of claim 7 , wherein an electrode adhesion value is greater than 0.30 N/18 mm.
9. 9 . The cathode for a secondary battery of claim 7 , wherein an electrode resistance value is less than 10.0 Ω·cm.
10. 10 . A lithium secondary battery, comprising: the cathode for a secondary battery according to claim 7 .

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application is a continuation of U.S. patent application Ser. No. 18/509,427, filed Nov. 15, 2023, which claims priority to Korean Patent Application No. 10-2022-0162155 filed Nov. 29, 2022, the disclosures of which are hereby incorporated by reference in their entireties. BACKGROUND OF THE INVENTION Field of the Invention The present disclosure relates to a cathode slurry composition, a cathode for a secondary battery, and a lithium secondary battery. Description of Related Art Recently, research into an electric vehicle (EV) that can replace a fossil fuel powdered vehicle, one of the main causes of air pollution, has been actively conducted. A lithium secondary battery having a high discharge voltage and output stability is mainly used as a power source of such an electric vehicle (EV), and demand and interest for a cathode for a secondary battery having excellent performance are also increasing. A lithium-transition metal composite oxide (e.g., an NCM-based active material) or a lithium iron phosphate-based (LFP) active material containing lithium is mainly used as an active material for the cathode for a secondary battery, and a cathode slurry obtained by dissolving such a cathode active material is coated on a substrate such as a cathode current collector, or the like, and then dried to prepare a cathode for a secondary battery. In general, when a size of particles of the cathode active material is reduced, ionic conductivity may be improved, but a specific surface area is also increased, so that an aggregation phenomenon between the particles may be intensified. When the aggregation phenomenon between the particles of the active material in a slurry intensifies, dispersion of the active material may be difficult, so there may be a limitation in increasing a solids content of the slurry, and viscosity of the slurry may increase, which may decrease flowability and processability. As such, depending on the characteristics of the cathode slurry (solids content, viscosity, and the like), there may be restrictions on cathode loading design, coating speed settings, and the like, and adhesion, resistance characteristics, and the like, of the finally formed cathode for a secondary battery may also be affected. Accordingly, there is a demand for development of a cathode slurry capable of forming a cathode for a secondary battery having improved performance with excellent processability. SUMMARY OF THE INVENTION An aspect of the present disclosure to provide a slurry composition capable of forming a cathode for a secondary battery without limitations in electrode loading design, coating speed setting, and the like. Another aspect of the present disclosure to provide a cathode for a secondary battery having improved adhesion between a current collector and a cathode layer, and having a relatively low resistance value due to excellent ion conductivity and a lithium secondary battery including the same. According to an aspect a cathode slurry composition includes: a cathode active material, an acrylic dispersant, and a solvent, wherein, in the cathode slurry composition, a solids content is 65% by weight or more, and a shear viscosity value measured at a temperature of 25° C. and a shear rate of 1/s is 150 Pa·s or less. The acrylic dispersant may include a polyacrylate-based compound. The acrylic dispersant may be included in the cathode slurry composition in an amount of 0.1 to 10% by weight based on a solids content. The slurry composition may have an RPA value of 1.2 or less according to Equation 1 below. RPA=|(PA0 - PA1)|/PA0[Equation⁢ 1] In Equation 1, RPA is a change rate of a phase angle before and after shearing of a slurry, PA0 is a phase angle (°) of a slurry before shearing, and PA1 is a phase angle (°) of a slurry after shearing. The cathode active material may have an average particle diameter (D50) of less than 5 μm. The cathode active material may include a lithium iron phosphate (LFP)-based active material. The cathode slurry composition may further include a conductive material dispersion. The conductive material dispersion may include an additional acrylic dispersant. A cathode for a secondary battery according to an aspect is formed of a cathode slurry composition according to any one of the above-described embodiments. The cathode for a secondary battery may have an electrode adhesion value of greater than 0.30 N/18 mm. The cathode for a secondary battery may have an electrode resistance value of less than 10.0 Ω·cm. A lithium secondary battery according to an embodiment includes a cathode for a secondary battery formed of the cathode slurry composition according to any one of the above-described embodiments. BRIEF DESCRIPTION OF THE DRAWINGS The above and other aspects, features and other advantages of the present disclosure will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings,