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EP-4071857-B1 - NEGATIVE ELECTRODE ACTIVE MATERIAL, AND NEGATIVE ELECTRODE AND SECONDARY BATTERY INUDING THE SAME

EP4071857B1EP 4071857 B1EP4071857 B1EP 4071857B1EP-4071857-B1

Inventors

  • CHOI, JUNG HYUN
  • PARK, HANG AH
  • SHIN, SUN YOUNG
  • KIM, JE YOUNG
  • LEE, YONG JU

Dates

Publication Date
20260513
Application Date
20210127

Claims (11)

  1. A negative electrode active material comprising: a silicon-based core; and an outer coating layer formed on the silicon-based core and including polyimide, wherein the polyimide comprises a fluorine-containing imide unit.
  2. The negative electrode active material of claim 1, wherein the outer coating layer is included in an amount of more than 0 wt% and 4.5 wt% or less in the negative electrode active material.
  3. The negative electrode active material of claim 1, wherein the outer coating layer contains fluorine in an amount of from 10 wt% to 50 wt%.
  4. The negative electrode active material of claim 1, wherein the fluorine-containing imide unit is represented by the following Chemical Formula 1: in the Chemical Formula 1, A 1 is a C4 to C30 tetravalent organic group, B 1 is a C6 to C30 divalent organic group, and at least one of A 1 and B 1 contains fluorine.
  5. The negative electrode active material of claim 1, further comprising an inner carbon coating layer formed between the silicon-based core and the outer coating layer.
  6. The negative electrode active material of claim 5, wherein the inner carbon coating layer is included in an amount of from 1 wt% to 10 wt% based on a total weight of the silicon-based core and the inner carbon coating layer.
  7. The negative electrode active material of claim 1, wherein the silicon-based core includes a silicon-based particle comprising a compound represented by Chemical Formula 2 below and a metal distributed on a surface of the silicon-based particle, an inside of the silicon-based particle, or on the surface and the inside of the silicon-based particle, and the metal is at least one selected from the group consisting of Li, Mg, Al, Ca, and Ti: [Chemical Formula 2] SiO x (0≤x<2).
  8. The negative electrode active material of claim 7, wherein the metal is included in an amount of from 0.1 wt% to 25 wt% in the silicon-based core.
  9. The negative electrode active material of claim 1, wherein the negative electrode active material has an average particle diameter (D 50 ) of from 0.1 µm to 20 µm.
  10. A negative electrode comprising: a negative electrode current collector; and a negative electrode active material layer formed on the negative electrode current collector and including a negative electrode material, wherein the negative electrode material includes the negative electrode active material according to claim 1.
  11. A secondary battery comprising: the negative electrode according to claim 10; a positive electrode disposed to face the negative electrode; a separator interposed between the negative electrode and the positive electrode; and an electrolyte.

Description

TECHNICAL FIELD Cross-Reference to Related Application This application claims priority to and the benefit of Korean Patent Application No. 10-2020-0010814, filed on January 30, 2020. Technical Field The present invention relates to a negative electrode active material, and a negative electrode and a secondary battery including the same. BACKGROUND ART Recently, in response to the rapid spread of electronic devices using batteries, such as mobile phones, notebook computers, electric vehicles, and the like, demand for secondary batteries having a small size, a light weight, and relatively high capacity is rapidly increasing. In particular, lithium secondary batteries have been in the spotlight as a driving power source for portable devices due to having a light weight and high energy density. Accordingly, research and development efforts for enhancing the performance of lithium secondary batteries have been continuously made. In general, lithium secondary batteries include a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, an electrolyte, an organic solvent, and the like. In addition, in the positive electrode and the negative electrode, an active material layer including a positive electrode active material or a negative electrode active material may be formed on a current collector. In the positive electrode, a lithium-containing metal oxide such as LiCoO2, LiMn2O4, or the like is generally used as the positive electrode active material, and in the negative electrode, a carbon-based active material or a silicon-based negative electrode active material, which does not contain lithium, is used as the negative electrode active material. In particular, the silicon-based negative electrode active material among the negative electrode active materials has attracted attention due to having about 10 times higher capacity than that of the carbon-based negative electrode active materials and has an advantage in that even a thin electrode is used to achieve high energy density due to high capacity. However, the silicon-based negative electrode active material exhibits a large degree of volumetric expansion according to charging and discharging, leading to a great deal of side reactions with an electrolyte. Accordingly, the silicon-based negative electrode active material exhibits poor performance in terms of cycle fading, high-temperature lifetime characteristics, and high-temperature storage characteristics and thus is not commonly used. Therefore, there is a demand for the development of a secondary battery capable of preventing side reactions with an electrolyte and enhancing lifetime characteristics while achieving the high capacity and energy density of the silicon-based negative electrode active material. Korean Unexamined Patent Publication No. 10-2017-0074030 relates to a negative electrode active material for a lithium secondary battery, a method of preparing the same, and a lithium secondary battery including the same and discloses a negative electrode active material including a porous silicon-carbon composite, but there is a limitation in solving the above-described problems. Korean Patent Publication No. 10-2018-0122962 relates to a production method of a negative electrode active material which comprises the following steps: preparing a silicon-based compound containing SiOx (0.5 < x < 1.3); disposing a polymer layer containing a polymer compound on the silicon-based compound; disposing a metal catalyst layer on the polymer layer; heat-treating the silicon-based compound in which the polymer layer and the metal catalyst layer are disposed; and removing the metal catalyst layer. European Patent Publication No. 3 264 504 provides a negative electrode active material layer including a polyimide-coated active material particle, wherein an active material particle is coated with a polyimide layer derived from a monomeric polyimide precursor, and an aqueous binder. [Related-Art Documents] Patent Documents] Korean Unexamined Patent Publication No. 10-2017-0074030Korean Patent Publication No. 10-2018-0122962European Patent Publication No. 3 264 504 DETAILED DESCRIPTION OF THE INVENTION TECHNICAL PROBLEM The present invention is directed to providing a negative electrode active material excellent in high-temperature lifetime performance, high-temperature storage performance, and output performance in use of a silicon-based negative electrode active material. The present invention is also directed to providing a negative electrode including the above-described negative electrode active material. The present invention is also directed to providing a secondary battery including the above-described negative electrode. TECHNICAL SOLUTION One aspect of the present invention provides a negative electrode active material which includes: a silicon-based core; and an outer coating layer formed on the silicon-based core and including polyimide, wher