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KR-102962585-B1 - LITHIUM METAL ELECTRODE AND LITHIUM SECONDARY BATTERY COMPRISING THE SAME

KR102962585B1KR 102962585 B1KR102962585 B1KR 102962585B1KR-102962585-B1

Abstract

The present invention relates to a lithium electrode and a lithium secondary battery including the same, and more specifically, by providing a protective layer comprising a two-dimensional material and an intrinsically porous polymer on the surface of a lithium metal layer, the formation of dendrites is suppressed and lithium ion transport characteristics are improved, thereby enabling a long lifespan of the lithium secondary battery.

Inventors

  • 김명성
  • 김윤정
  • 김수현
  • 김기현

Assignees

  • 주식회사 엘지에너지솔루션

Dates

Publication Date
20260507
Application Date
20210602

Claims (12)

  1. Anode containing a positive electrode active material; A cathode comprising a lithium electrode; and A lithium-sulfur battery comprising an electrolyte interposed between the anode and the cathode, The above positive active material includes a compound containing sulfur, and The above lithium electrode is A lithium metal layer; and a protective layer formed on at least one surface of the lithium metal layer, comprising The above protective layer comprises a two-dimensional material and an intrinsically porous polymer, and The above two-dimensional material comprises one or more selected from the group consisting of graphene, graphene oxide, molybdenum disulfide, hexagonal boron nitride, and graphite-type carbon nitride, and The above intrinsic porous polymer is a lithium-sulfur battery comprising a repeating structure represented by the following chemical formula 1. [Chemical Formula 1]
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  3. In paragraph 1, A lithium-sulfur battery comprising one or more types selected from the group consisting of graphene oxide and graphite-type carbon nitride, wherein the above two-dimensional material.
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  5. In paragraph 1, A lithium-sulfur battery in which the weight ratio of the above two-dimensional material and the intrinsic porous polymer is 1:1 to 1:20.
  6. In paragraph 1, A lithium-sulfur battery having a protective layer thickness of 0.1 to less than 5 μm.
  7. In paragraph 1, A lithium-sulfur battery having a lithium metal layer thickness of 20 to 200 μm.
  8. (a) A step of preparing a first solution by dispersing a two-dimensional material in a first solvent; (b) a step of preparing a second solution by dissolving an intrinsic porous polymer in a second solvent; (c) a step of preparing a coating solution by mixing the first solution and the second solution; and (d) a step of applying the coating solution to at least one surface of the lithium metal layer, and The above two-dimensional material comprises one or more selected from the group consisting of graphene, graphene oxide, molybdenum disulfide, hexagonal boron nitride, and graphite-type carbon nitride, and A method for manufacturing a lithium electrode comprising a repeating structure represented by the following chemical formula 1, wherein the above intrinsic porous polymer. [Chemical Formula 1]
  9. In paragraph 8, A method for manufacturing a lithium electrode, wherein the first solvent and the second solvent are the same or different and comprise one or more selected from the group consisting of tetrahydrofuran, toluene, cyclohexane, N-methyl-2-pyrrolidone, dimethylformamide, dimethylacetamide, tetramethylurea, dimethyl sulfoxide, and triethyl phosphate.
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Description

Lithium electrode and lithium secondary battery comprising the same The present invention relates to a lithium electrode and a lithium secondary battery including the same. As the scope of application for lithium secondary batteries expands to include not only portable electronic devices and communication devices but also electric vehicles (EVs) and electric storage systems (ESS), there is a growing demand for higher capacity and higher energy density of lithium secondary batteries used as power sources for these devices. Conventional lithium-ion batteries utilize graphite for the negative electrode and lithium cobalt oxide (LCO) for the positive electrode, achieving an energy density of approximately 700 Wh/kg. However, as previously mentioned, the demand for high-energy-density lithium-ion batteries is expanding, leading to a continuous need to increase their energy density. For instance, increasing energy density is necessary to extend the driving range of electric vehicles to over 500 km on a single charge. To increase the energy density of lithium secondary batteries, the use of lithium electrodes containing lithium metal is increasing. Specifically, lithium metal has the advantage of enabling the realization of high-capacity, high-energy-density batteries, as it has a very high theoretical specific capacity of 3,860 mAh/g and a very low standard reduction potential (Standard Hydrogen Electrode; SHE) of -3.045 V. However, lithium metal is a highly reactive and difficult-to-handle metal, posing a problem in processing. Furthermore, when a lithium electrode is used as the negative electrode of a lithium secondary battery, the lithium metal readily reacts with the electrolyte, water, impurities within the battery, or lithium salts to form a solid electrolyte interface layer (SEI layer), a type of passivation film, on the surface. This passivation film causes local differences in current density, which promotes the formation of dendritic dendrites by the lithium metal during charging. As charging and discharging progress, these dendrites gradually grow, causing an internal short circuit between the positive and negative electrodes. Additionally, dendrites possess mechanically weak points (bottle necks) that form dead lithium, which loses electrical contact with the current collector during discharge. This reduces battery capacity, shortens cycle life, and negatively affects battery stability. To improve upon the problems of such lithium electrodes, lithium electrodes with protective layers having various compositions or shapes are being studied. For example, Korean published patent No. 2018-0041086 relates to a protective layer formed by applying a slurry containing fluorocarbon or fluorine metal and a PVdF-based resin to a lithium metal anode. Although a lithium metal anode formed with a protective layer containing the above composition can prevent the formation of dendrites, there is a problem in that uniform lithium ion distribution and effective solid electrolyte interface layer formation on the anode surface are not smoothly achieved so that uniform plating and stripping of lithium metal can be achieved during charging and discharging to improve battery performance. In addition, Korean Patent Publication No. 2016-0052351 discloses that the stability and lifespan characteristics of a lithium secondary battery can be improved by suppressing the growth of lithium dendrites through the inclusion of a lithium dendrite-absorbing material in a polymer protective film formed on the surface of a lithium metal electrode. However, due to the polymer protective film, it is difficult to achieve a uniform distribution of lithium ions on the electrode surface, and it is difficult to apply this to lithium-sulfur batteries. In addition, Qiuli Yang et al. and Gi Hyeon Moon et al. disclose that dendrite formation can be suppressed by uniformly distributing lithium ions on the surface of a lithium metal anode by forming a protective film on the lithium metal anode using polymers of intrinsic microporosity (PIM) having intrinsic pores within the polymer structure. However, when the protective film formed on the lithium metal anode contains only polymers of intrinsic microporosity, the movement of lithium ions is limited to only the pores contained in the polymers of intrinsic microporosity, which leads to a decrease in lithium ion conductivity and a problem of large overvoltage occurring during the charging and discharging process. As such, various studies have been conducted to prevent the growth of lithium metal dendrites in batteries using lithium electrodes as anodes, but research results on protective layers that enable the improvement of overall battery performance are insufficient. Therefore, there is still a need to develop lithium electrodes that can realize high-capacity, high-energy-density, and long-life lithium secondary batteries by preventing the formation of dendrites on the lithium electrode. FIG. 1 is a