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CN-116325234-B - Negative electrode for secondary battery, negative electrode slurry, and method for producing negative electrode

CN116325234BCN 116325234 BCN116325234 BCN 116325234BCN-116325234-B

Abstract

The purpose of the present invention is to provide a secondary battery negative electrode having improved life characteristics, a slurry for a negative electrode, and a method for manufacturing a negative electrode. The negative electrode for a secondary battery contains at least a graphite-based material and a silicon-based material as negative electrode active materials, and a conductive material, wherein the graphite-based material contains a granulated product of artificial graphite and natural graphite, at least a part of the natural graphite in the granulated product is partially flaked to form flaked portions, and the flaked portions are in contact with the silicon-based material or other artificial graphite and the granulated product of natural graphite, or are composited with the silicon-based material.

Inventors

  • MATSUHARA KEIKO
  • GAO LIANGHUI

Assignees

  • 株式会社LG新能源

Dates

Publication Date
20260512
Application Date
20211224
Priority Date
20201225

Claims (11)

  1. 1. A negative electrode for a secondary battery comprises at least a graphite material and a silicon material as negative electrode active materials, and a conductive material, Wherein the graphite-based material comprises a granulated product of artificial graphite and natural graphite, At least a part of the natural graphite in the granulated product is partially flaked to form flaked portions, and The flaked portion is contacted with the silicon-based material or other synthetic graphite and granulated product of natural graphite, or forms a composite with the silicon-based material, Wherein "partially flaking" means that the surface portions of the natural graphite are not completely exfoliated and separated from the natural graphite, but the surface portions of the natural graphite are partially exfoliated, curled and flaked.
  2. 2. The anode for a secondary battery according to claim 1, wherein the silicon-based material comprises either one or both of silicon oxide and silicon-based alloy.
  3. 3. The negative electrode for secondary battery according to claim 2, wherein the silicon-based alloy contains at least one selected from the group consisting of titanium, vanadium, chromium, manganese, iron, cobalt, nickel, and copper.
  4. 4. The anode for a secondary battery according to claim 1, wherein the conductive material is carbon black.
  5. 5. The negative electrode for a secondary battery according to claim 1, wherein a weight ratio of the graphite-based material to the silicon-based material is 98:2 to 50:50.
  6. 6. The negative electrode for a secondary battery according to claim 1, wherein the granulated product contains artificial graphite and natural graphite in a weight ratio of 60:40 to 90:10.
  7. 7. A secondary battery comprising the anode as defined in any one of claims 1 to 6, a cathode, a separator interposed between the anode and the cathode, and an electrolyte.
  8. 8. A negative electrode slurry for a secondary battery for manufacturing the negative electrode for a secondary battery according to any one of claims 1 to 6, the negative electrode slurry comprising: graphite-based material and silicon-based material as negative electrode active materials, conductive material, solvent, and at least one of thickener and binder, The solids content in the slurry is 60 wt% or more relative to the weight of the slurry, Wherein the graphite-based material comprises a granulated product of artificial graphite and natural graphite, Wherein at least a portion of the natural graphite in the granulated product is partially flaked to form flaked portions.
  9. 9. The negative electrode slurry of claim 8, wherein the solids content in the slurry is 65-75 wt% relative to the weight of the slurry.
  10. 10. A method of manufacturing the negative electrode for a secondary battery according to any one of claims 1 to 6, comprising the steps of: mixing a graphite-based material and a silicon-based material as negative electrode active materials, a conductive material, a solvent, and at least one of a thickener and a binder to prepare a slurry having a solid content of 60 wt% or more with respect to the weight of the slurry; Performing a hard mixing of the slurry, wherein at least a portion of the natural graphite in the granulated product is partially flaked to form flaked portions in the step of performing the hard mixing of the slurry, and The slurry is applied to a current collector to obtain a negative electrode, Wherein the graphite-based material is a granulated product of artificial graphite and natural graphite.
  11. 11. The method of claim 10, further comprising the step of adding a binder and a solvent to the slurry after the step of performing hard mixing of the slurry.

Description

Negative electrode for secondary battery, negative electrode slurry, and method for producing negative electrode Technical Field The present disclosure relates to a negative electrode (negative electrode) for a secondary battery, a negative electrode slurry, and a method for manufacturing a negative electrode. The present application claims priority from japanese patent application 2020-216840 filed on 12/25/2020, the disclosure of which is incorporated herein by reference. Background As technology development and demand for mobile instruments and electric vehicles increase, demand for secondary batteries as energy sources is increasing. Among such secondary batteries, lithium ion secondary batteries having high energy density and voltage, long cycle life, and low self-discharge rate have been commercialized and widely used. Recently, active researches have been conducted to provide such lithium ion secondary batteries having high capacity. Silicon-based materials such as silicon oxide or silicon-based alloy have a higher theoretical capacity density than currently mainly used carbonaceous materials such as graphite, and thus have been studied so far as negative electrode materials for improving the energy density of lithium ion secondary batteries. In particular, silicon oxides (SiO x (0 < x < 2), such as SiO) in silicon-based materials have been partially commercialized due to relatively low expansion rates. However, such silicon oxides exhibit an initial efficiency at least 20% lower than that of graphite, and when used alone, the difference in irreversible capacity increases compared to the positive electrode (positive electrode). Thus, such silicon oxides are actually used by mixing with carbonaceous materials in a content of several percent. In addition, silicon-based alloys having a lower irreversible capacity than silicon oxide show a problem in terms of expansion rate, and thus use in combination with graphite has been examined so that the expansion rate of the entire electrode can be reduced. However, carbonaceous materials and silicon-based materials exhibit different powder properties, conductivity, expansion rate, and the like. Therefore, when a carbonaceous material is used in combination with a silicon-based material, it is difficult to form a structure in which all the active materials are utilized while maintaining a conductive path between the carbonaceous material and the silicon-based material under conditions of expansion and contraction caused by repeated charge and discharge. In this case, the capacity of the carbonaceous material and the capacity of the silicon-based material having a higher expansion coefficient are becoming increasingly unusable. Further, when artificial graphite is used as a carbonaceous material, it shows an advantage of lower expansion ratio than natural graphite, but it is hard and difficult to deform even under pressing, and voids are easily formed in the gaps with the silicon-based material from the start of manufacturing the electrode, so that silicon-based material particles having a small particle diameter are isolated, thereby causing deterioration of initial capacity or deterioration of capacity after repeated charge and discharge. Therefore, in order to secure a conductive path in a negative electrode including both a carbonaceous material and a silicon-based material, a method of forming a composite of a non-conductive silicon-based material and a conductive carbonaceous material (for example, patent document 1 or patent document 2), or a method of adding a nanocarbon material such as graphene or carbon nanotube as a conductive material (for example, patent document 3) has been proposed. However, in the former case, there is a problem that it is difficult to secure a conductive path between particles. In addition, in the latter case, there is a problem in that the nanocarbon material is difficult to be uniformly dispersed in the entire anode, and the nanocarbon material is very expensive. [ Prior Art literature ] [ Patent literature ] Patent document 1 Japanese patent application laid-open No. 2019-067579 Patent document 2 International publication No. 2012/140790 Patent document 3 Japanese patent laid-open No. 2020-013218 Disclosure of Invention Technical problem The present disclosure is directed to solving the problems of the related art, and therefore, the present disclosure is directed to providing a negative electrode for a secondary battery capable of stably repeating charge and discharge by forming a high-level and strong conductive path in the negative electrode, thereby providing improved life characteristics, and to providing a negative electrode slurry and a manufacturing method of the negative electrode. Technical proposal According to a first embodiment of the present disclosure, there is provided a negative electrode for a secondary battery, comprising at least a graphite-based material and a silicon-based material as a negative electrod