KR-102963786-B1 - NEGATIVE ACTIVE MATERIAL FOR RECHARGEABLE LITHIUM BATTERY, METHOD OF PREPARING THE SAME, AND RECHARGEABLE LITHIUM BATTERY INCLUDING THE SAME

Abstract

The present invention relates to a negative electrode active material for a lithium secondary battery comprising spherical natural graphite particles, wherein the spherical natural graphite particles have a structure in which flake-like natural graphite fragment particles are organized and assembled in a cabbage-like or random manner, phosphorus (P) atoms are bonded to the edge planes of all or some of the flake-like natural graphite fragment particles constituting the interior or surface of the spherical natural graphite particles, and an amorphous and/or semicrystalline carbon coating layer is formed on the edge planes and basal planes of all or some of the flake-like natural graphite fragment particles. The invention also relates to a negative electrode active material for a lithium secondary battery, a method for manufacturing the same, and a lithium secondary battery comprising the same.

Inventors

• 이성만
• 노윤상

Assignees

• 강원대학교산학협력단

Dates

Publication Date

20260513

Application Date

20220826

Priority Date

20220209

Claims (13)

1. As a negative electrode active material for a lithium secondary battery containing spherical natural graphite particles, The above-mentioned spherical natural graphite particles have a structure in which flaky natural graphite fragment particles are organized and assembled in a cabbage-like or random manner, and Phosphorus (P) atoms are bonded to the edge planes of all or some of the above-mentioned flake-like natural graphite fragment particles, and A negative electrode active material for a lithium secondary battery, characterized in that an amorphous or semicrystalline carbon coating layer is formed on the edge plane and basal plane of all or some of the above-mentioned flake-like natural graphite fragment particles.
2. In paragraph 1, A negative electrode active material for a lithium secondary battery characterized in that phosphorus (P) atoms are bonded only to the surface of the edge plane, not the basal plane, of the flake-like natural graphite fragment particles.
3. In paragraph 1, A negative electrode active material for a lithium secondary battery characterized by phosphorus (P) atoms being bonded in the form of COP or CPO to the edge surface of flake-like natural graphite fragment particles.
4. In paragraph 1, A negative electrode active material for a lithium secondary battery, characterized in that the content of an amorphous and semicrystalline carbon coating layer formed on the edge surface and base surface of all or some of the flake-like natural graphite fragment particles is 3 to 10 weight% based on the total weight of the negative electrode active material.
5. In paragraph 1, The above amorphous or semicrystalline carbon coating layer is formed from a carbon precursor comprising at least one selected from gum arabic, citric acid, thiaric acid, sucrose, vinylidene fluoride, carboxymethylcellulose (CMC), hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer (EPDM), sulfonated EPDM, starch, phenolic resin, furan resin, furfuryl alcohol, polyacrylic acid, sodium polyacrylate, polyacrylonitrile, polyimide, epoxy resin, cellulose, styrene, polyvinyl alcohol, polyvinyl chloride, coal-based pitch, petroleum-based pitch, mesophase pitch, low molecular weight heavy oil, glucose, gelatin, and sugars, characterized as a negative electrode active material for a lithium secondary battery.
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13. A cathode comprising a cathode active material according to any one of claims 1 to 5; Anode; and electrolyte; Lithium secondary battery.

Description

Negative active material for rechargeable lithium battery, method of preparing the same, and rechargeable lithium battery including the same The present invention relates to a negative electrode active material for a lithium secondary battery, a method for manufacturing the same, and a lithium secondary battery comprising the negative electrode active material for a lithium secondary battery. The demand for lithium-ion batteries as an energy source for mobile devices as well as electric vehicles is rapidly increasing, and in relation to the expansion of their application ranges, there is a need to improve the performance of lithium-ion batteries, including stability at high temperatures and long lifespan characteristics. Currently, crystalline graphite materials are used as negative electrode active materials for lithium secondary batteries, and crystalline graphite is divided into artificial graphite and natural graphite. The use of artificial graphite is increasing because it has relatively superior high-temperature life characteristics and swelling characteristics compared to natural graphite. However, the above artificial graphite is typically obtained by heating and carbonizing a carbon precursor at a high temperature of about 2800°C or higher under an inert atmosphere to remove impurities and undergo a graphitization process, so the manufacturing cost is high and there is a problem that the lithium storage capacity is somewhat smaller than that of natural graphite due to the limit of the degree of graphitization. Currently commercialized natural graphite is used by assembling flaky natural graphite fragments into a cabbage-like or random shape to form a spherical structure, and then coating the surface with amorphous carbon. However, in the case of the carbon-coated spherical natural graphite mentioned above, during repeated charge and discharge cycles, the carbon coating layer on the surface undergoes mechanical cracking, which leads to a side reaction with the electrolyte inside the spherical graphite particles and additionally forms an SEI film (generally referred to as internal SEI). Due to gas generation and swelling caused by these side reactions, the high-temperature lifespan degradation and the high-temperature lifespan and output characteristics are found to be insufficient for application in electric vehicles, etc., and thus, further performance improvement is required. The aforementioned side reaction is caused by the decomposition of the electrolyte on the surface of graphite particles, and it is known that the edge sites, which are the active sites of the graphite particles, further accelerate this decomposition reaction. Therefore, it is necessary to develop technology to resolve the problems caused by side reactions with the electrolyte and to improve structural stability by stabilizing the surface of the flake-like natural graphite fragment particles constituting the surface and interior of spherical natural graphite. Figure 1 is the XPS analysis result of a highly oriented pyrolytic graphite sample prepared according to Experimental Example 1 of the present invention. Figure 2 is a scanning electron microscope (SEM) image of the negative electrode active material according to Example 1. Figure 3 is a scanning electron microscope (SEM) image of the cathode active material according to Comparative Example 1. Figure 4 is a scanning electron microscope (SEM) image of the cathode active material according to Comparative Example 2. Figure 5 shows the change in capacity retention rate according to the progress of charge-discharge cycles at 45°C for the negative electrode active materials according to Example 1 and Comparative Examples 1 and 2, respectively. In describing the present invention, if it is determined that a detailed description of related known functions or configurations could unnecessarily obscure the essence of the invention, such detailed description will be omitted. Since embodiments according to the concept of the present invention may be subject to various modifications and may take various forms, specific embodiments are illustrated in the drawings and described in detail in this specification or application. However, this is not intended to limit embodiments according to the concept of the present invention to specific disclosed forms, and it should be understood that they include all modifications, equivalents, and substitutions that fall within the spirit and scope of the present invention. The terms used herein are merely for describing specific embodiments and are not intended to limit the invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this specification, terms such as “comprising” or “having” are intended to specify the existence of the described features, numbers, steps, actions, components, parts, or combinations thereof, and should be understood as not precluding the existence or addition of one or m