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EP-4191702-B1 - NEGATIVE ELECTRODE FOR SECONDARY BATTERY COMPRISING ACTIVE MATERIAL LAYER HAVING DIFFERENT COMPOSITION, ELECTRODE ASSEMBLY AND SECONDARY BATTERY COMPRISING THE SAME

EP4191702B1EP 4191702 B1EP4191702 B1EP 4191702B1EP-4191702-B1

Inventors

  • NOH, TAEGYUN

Dates

Publication Date
20260506
Application Date
20220630

Claims (12)

  1. A negative electrode (100) for secondary battery in which a negative electrode active material layer is formed on at least one surface of a negative electrode current collector (101), wherein the negative electrode active material layer includes a first negative electrode active material layer (111), and a second negative electrode active material layer (112) formed on one side or both sides of the first negative electrode active material layer (111) in a planar, and wherein the first negative electrode active material layer (111) includes uncoated graphite as a first negative electrode active material, and the second negative electrode active material layer (112) includes carbon-coated graphite as a second negative electrode active material.
  2. The negative electrode (100) for secondary battery according to claim 1, wherein: the negative electrode (100) includes a first inclined portion (121) on one end side, a second inclined portion (122) on the other end side, and a flat portion (123) located between the first inclined portion (121) and the second inclined portion (122) in a planar, and a first negative electrode active material layer (111) is formed on the flat portion (123), and a second negative electrode active material layer (112) is formed on the first inclined portion (121) and the second inclined portion (122).
  3. The negative electrode (100) for secondary battery according to claim 1, wherein: graphite of the first negative electrode active material and the second negative electrode active material is artificial graphite or natural graphite.
  4. The negative electrode (100) for secondary battery according to claim 1, wherein: carbon of the second negative electrode active material includes low-crystalline carbon, amorphous carbon, or a mixture thereof.
  5. The negative electrode (100) for secondary battery according to claim 1, wherein: the carbon is coated in an amount of 5 to 20% by weight based on the total weight of the carbon-coated graphite.
  6. The negative electrode (100) for secondary battery according to claim 1, wherein: the first negative electrode active material layer (111) and the second negative electrode active material layer (112) include at least one selected from the group consisting of a binder and a conductive material, in which the types thereof are different, or the content ratios of constituents are different.
  7. The negative electrode (100) for secondary battery according to claim 6, wherein: the first negative electrode active material includes uncoated graphite as an active material: styrene-butadiene rubber (SBR) as a binder: carbon black or carbon nanotubes (CNT) as a conductive material in a weight ratio of 93~97: 1~5: 0.1~5, and the second negative electrode active material includes carbon-coated graphite as an active material: styrene-butadiene rubber (SBR) as a binder: carbon black or carbon nanotubes (CNT) as a conductive material in a weight ratio of 93~97: 1~5: 0.1~5.
  8. The negative electrode (100) for secondary battery according to claim 1, wherein: a volume ratio of the first negative electrode active material layer (111) and the second negative electrode active material layer (112) is 4:6 to 6:4.
  9. An electrode assembly (200, 300) for secondary battery comprising the negative electrode (100) for secondary battery according to claim 1, wherein the electrode assembly (200) includes a separator (220) interposed between a positive electrode (210) and a negative electrode (220), and wherein the positive electrode (210) has a positive electrode active material layer (212) formed on at least one surface of a positive electrode current collector (211).
  10. The electrode assembly (200, 300) for secondary battery according to claim 9, wherein: the positive electrode active material layer (212) includes a first positive electrode active material layer (312), and a second positive electrode active material layer (313) formed on one side or both sides of the first positive electrode active material layer (312) in a planar and having a composition different from that of the first positive electrode active material layer (312).
  11. The electrode assembly (200, 300) for secondary battery according to claim 10, wherein: the first positive active material layer (312) and the second positive active material layer (313) include at least one selected from the group consisting of a positive active material, a binder, and a conductive material included in each layer, in which the types thereof are different, or the content ratios of components are different.
  12. A secondary battery in which the electrode assembly (200, 300) for secondary battery according to claim 9, and an electrolyte are incorporated in a battery case.

Description

[TECHNICAL FIELD] Cross Citation with Related Application(s) This application claims the benefit of Korean Patent Application No. 10-2021-0091135 filed on July 12, 2021 with the Korean Intellectual Property Office. The present disclosure relates to a negative electrode for secondary battery including an active material layer having different composition, an electrode assembly and a secondary battery including same. [BACKGROUND] Along with the technology development and increased demand for mobile devices, demand for secondary batteries as energy sources has been increasing rapidly. Among such secondary batteries, a lithium secondary battery exhibiting energy density and operating potential, and having long cycle life and low self-discharge rate is now commercialized and widely used. Also, as interest in environmental issues grows in recent years, studies are frequently conducted on an electric vehicle (EV), a hybrid electric vehicle (HEV) and the like which can replace a vehicle using fossil fuels such as a gasoline vehicle and a diesel vehicle, which are one of the main causes of air pollution. As a power source for such electric vehicle (EV) and hybrid electric vehicle (HEV), lithium secondary batteries with high energy density, high discharge voltage, and output stability are mainly studied and used. Such lithium secondary batteries are being developed as a model that can perform rapid charging in response to the needs of consumers, and for this purpose, design of the battery is performed in the direction of high energy density, long life, and low swelling. However, as the charge rate of rapid charging increases, lithium precipitation occurs on the negative electrode of the battery, which occurs locally at first, but eventually causes problems that worsen the battery life retention and swelling. By the way, the electrodes for secondary battery have different coating amounts for each position due to the sliding phenomenon caused by the coating of the electrode active material slurry during the manufacturing process, and accordingly, the electrodes are different in the charge/discharge characteristics, so that the negative electrode has a difference in the lithium deposition rate, which will affect the long-term performance of the battery. Therefore, there is a need to develop a technology capable of solving these problems. [DETAILED DESCRIPTION OF THE INVENTION] [Technical Problem] It is an object of the present disclosure to provide a negative electrode for secondary battery that can solve the lithium precipitation imbalance problem caused by the difference in the loading amount on a plane caused by the sliding phenomenon during the manufacture of the electrode active material layer, thereby preventing rapid deterioration of battery performance, an electrode assembly and a secondary battery including the same. [Technical Solution] According to one aspect of the present disclosure, there is provided a negative electrode for secondary battery in which a negative electrode active material layer is formed on at least one surface of a negative electrode current collector, wherein the negative electrode active material layer includes a first negative electrode active material layer, and a second negative electrode active material layer formed on one side or both sides of the first negative electrode active material layer in a planar, andwherein the first negative electrode active material layer includes uncoated graphite as a first negative electrode active material, and the second negative electrode active material layer includes carbon-coated graphite as a second negative electrode active material. Wherein, the negative electrode includes a first inclined portion on one end side, a second inclined portion on the other end side, and a flat portion located between the first inclined portion and the second inclined portion in the planar, and a first negative electrode active material layer may be formed on the flat portion, and a second negative electrode active material layer may be formed on the first inclined portion and the second inclined portion. The graphite of the first negative electrode active material and the second negative electrode active material may be artificial graphite or natural graphite, and carbon of the second negative electrode active material may be low-crystalline carbon, amorphous carbon, or a mixture thereof. Wherein, the carbon may be coated in an amount of 5 to 20% by weight based on the total weight of the carbon-coated graphite. Further, the first negative electrode active material layer and the second negative electrode active material layer include at least one selected from the group consisting of a binder and a conductive material, in which the types thereof may be different, or the content ratios of constituents may be different. Specifically, the first negative electrode active material may include uncoated graphite as an active material: styrene-butadiene rubber (SBR) as a