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US-20260128278-A1 - Electrode for Lithium Secondary Battery, Method of Preparing the Same and Lithium Secondary Battery Including the Same

US20260128278A1US 20260128278 A1US20260128278 A1US 20260128278A1US-20260128278-A1

Abstract

The present invention provides an electrode for a lithium secondary battery, which includes an electrode current collector, an electrode active material layer formed on the electrode current collector, and an insulating layer formed on the electrode current collector and overlapping the electrode active material layer in a partial region. Here, when the thickness of the electrode active material layer in the region in which the electrode active material layer and insulating layer do not overlap is d 1 , and the thickness of the insulating layer in the region in which the electrode active material layer and insulating layer do not overlap is d 2 , d 2 /d 1 is 0.02 to 0.4.

Inventors

  • Sung Chul Park
  • Ung Ju Lee
  • Koo Seung CHUNG

Assignees

  • LG ENERGY SOLUTION, LTD.

Dates

Publication Date
20260507
Application Date
20251230
Priority Date
20180201

Claims (16)

  1. 1 . An electrode for a lithium secondary battery, the electrode comprising: an electrode current collector; an electrode active material layer formed on the electrode current collector; and an insulating layer formed on the electrode current collector and overlapping and contacting the electrode active material layer in a partial region, wherein the insulating layer is positioned on the partial region of the electrode active material layer, wherein the thickness of the insulating layer at an end of the electrode active material layer is A 0 , the thickness of the insulating layer at an end of the insulating layer is A, and A/A 0 is at least 0.05 and less than 1.
  2. 2 . The electrode according to claim 1 , wherein a length of a region in which the electrode active material layer and the insulating layer overlap is 0.1 to 1.3 mm.
  3. 3 . The electrode according to claim 1 , wherein, in the region overlapping the electrode active material layer, a thickness of the insulating layer is decreased toward the electrode active material layer.
  4. 4 . The electrode according to claim 1 , wherein, in the region overlapping the electrode active material layer, a thickness of the insulating layer is continually decreased toward the electrode active material layer.
  5. 5 . The electrode according to claim 1 , wherein A 0 is 3 to 20 μm.
  6. 6 . The electrode according to claim 1 , wherein A is at least 0.15 and less than 20 μm.
  7. 7 . The electrode according to claim 1 , wherein a thickness of the electrode active material layer in a region in which the electrode active material layer and insulating layer do not overlap is d 1 , a thickness of the insulating layer in a region in which the electrode active material layer and insulating layer do not overlap is d 2 , and d 2 /d 1 is 0.02 to 0.4.
  8. 8 . The electrode according to claim 1 , wherein, in the region in which the electrode active material layer and insulating layer do not overlap, the thickness d 2 of the insulating layer is 3 to 20 μm.
  9. 9 . The electrode according to claim 1 , wherein, in the region in which the electrode active material layer and insulating layer do not overlap, the thickness d 1 of the electrode active material layer is 50 to 150 μm.
  10. 10 . The electrode according to claim 1 , wherein, in the region in which the electrode active material layer and the insulating layer overlap, the electrode active material layer is formed obliquely.
  11. 11 . A lithium secondary battery comprising the electrode for a lithium secondary battery of claim 1 .
  12. 12 . A method of preparing the electrode for a lithium secondary battery of claim 1 , the method comprising: forming an undried electrode active material layer by applying an active material slurry composition on an electrode current collector; forming an undried insulating layer by applying a composition for forming an insulating layer so as to overlap the undried electrode active material layer in a partial region; and simultaneously drying the undried electrode active material layer and the undried insulating layer.
  13. 13 . The method according to claim 10 , wherein a difference in viscosity between the active material slurry composition and the composition for forming an insulating layer is 5,000 cP or less at 25° C.
  14. 14 . The method according to claim 11 , wherein a viscosity of the composition for forming an insulating layer is 1,000 to 10,000 cP at 25° C.
  15. 15 . The method according to claim 11 , wherein a viscosity of the active material slurry composition is 5,000 to 15,000 cP at 25° C.
  16. 16 . The method according to claim 10 , wherein the composition for forming an insulating layer comprises a binder and a solvent, and a solid content of the composition for forming an insulating layer is 5 to 15 wt %.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application is a continuation of U.S. application Ser. No. 18/756,686, filed on Jun. 27, 2024, which is a continuation of U.S. patent application Ser. No. 16/959,857, filed on Jul. 2, 2020, now U.S. Pat. No. 12,057,566, which is a national phase entry under 35 U.S.C. § 371 of International Application No. PCT/KR2019/001469, filed on Feb. 1, 2019, which claims priority to and the benefit of Korean Patent Application No. 10-2018-0013008, filed on Feb. 1, 2018, the disclosures of which are hereby incorporated herein by reference. TECHNICAL FIELD The present invention relates to an electrode for a lithium secondary battery, a method of preparing the same, and a lithium secondary battery including the same. BACKGROUND ART According to the increase in the development and demand for mobile devices, the demand for a secondary battery as a power source is rapidly increasing, and therefore many studies on batteries capable of meeting various demands have been conducted. Typically, in terms of the shape of a battery, there is a high demand for a prismatic battery and a pouch-type battery, which can be applied to a product such as a mobile phone with a small thickness, and in terms of a material, there is a high demand for a lithium secondary battery such as a lithium cobalt polymer battery with a high energy density, a high discharge voltage and high safety. One of the major research projects on secondary batteries is enhancing safety. The main cause of battery safety-related accidents is caused by occurrence of an abnormal high temperature state due to a short circuit between a positive electrode and a negative electrode. In other words, to maintain electric insulation in a normal situation, a separator is disposed between the positive electrode and the negative electrode, but there is a limitation with only a conventional separator in an abnormal abuse situation in which a battery is overcharged or overdischarged, an internal short circuit occurs due to the dendritic growth of an electrode material or impurities, a sharp object such as a nail or a screw perforates a battery, or the battery is deformed excessively due to an external force. Generally, a microporous film consisting of a polyolefin resin is mainly used as a separator, but the film has a thermal resistance temperature of about 120 to 160° C., which means that the film has insufficient thermal resistance. Therefore, when an internal short circuit occurs, there is a problem in which a short-circuit part expands by shrinkage of the separator due to short-circuit reaction heat, leading to thermal runaway in which more and higher reaction heat is generated. In addition, generally, a secondary battery is produced in a prismatic shape by cutting a positive electrode and a negative electrode into a constant size, and overlapping the cut electrodes layer by layer. Here, as there is a very small needle-like sharp part at the edge of the positive electrode or negative electrode coated with a polymer electrolyte, when the electrodes are stacked, this part has a minute internal short circuit, leading to an adverse effect on battery performance. Particularly, since the edge is more irregular than the inside when being coated with a polymer electrolyte, there is a high probability of a short circuit due to non-uniform coating. In addition, when upper and lower electrode layers are perfectly overlapped while the electrodes are stacked, a short circuit between the positive electrode and the negative electrode may occur. As described above, various methods for reducing cell deformation, an external impact or the probability of a physical short circuit between a positive electrode and a negative electrode have been studied. For example, to prevent a short circuit in a completed battery caused by the contact of an electrode tab with the upper portion of an electrode assembly due to movement of the electrode assembly, a method of attaching an insulation tape with a predetermined size to an electrode tab adjacent to the upper portion of a current collector is used. As the insulation tape, generally, a polyimide film is used, and it is generally recommended that winding the insulation tape progresses from the upper portion of the current collector to a length slightly extending downward. In addition, to prevent unwinding, generally, the tape was wound about 2 to 3 times. However, winding of the insulation tape is very complicated, and when the insulation tape is wound from the upper portion of the current collector to a length slightly extending downward, such a portion may cause an increase in the thickness of the electrode assembly. Further, there is a problem that the tape tends to be unwound when the electrode tap is bent. Korean Unexamined Patent Application Publication No. 10-2015-0031724 discloses a secondary battery. PRIOR ART LITERATURE Patent Literature Korean Unexamined Patent Application Publication No. 10-2015-0031724 D