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KR-102962582-B1 - METHOD OF MANUFACTURING POSITIVE ELECTRODE FOR LITHIUM-SULFUR BATTERY

KR102962582B1KR 102962582 B1KR102962582 B1KR 102962582B1KR-102962582-B1

Abstract

The present invention relates to a method for manufacturing a positive electrode for a lithium-sulfur battery, comprising: (1) a step of preparing a positive electrode active material slurry by mixing a sulfur-carbon composite and a binder; (2) a step of applying the positive electrode active material slurry to one surface of a current collector; (3) a first drying step of drying the current collector coated with the slurry using hot air and medium infrared rays; and (4) a second drying step of further drying using a laser heat source after the first drying step.

Inventors

  • 곽호범
  • 김윤경
  • 송현민
  • 김윤현
  • 김정원
  • 신동석

Assignees

  • 주식회사 엘지에너지솔루션
  • 엘지전자 주식회사

Dates

Publication Date
20260507
Application Date
20201125

Claims (8)

  1. (1) A step of preparing an anode active material slurry by mixing a sulfur-carbon composite and a binder; (2) A step of applying the above positive active material slurry to one surface of a current collector; (3) A first drying step of drying the current collector coated with the above slurry using hot air and medium infrared rays; and (4) A second drying step in which additional drying is performed using a laser heat source having a wavelength of 950 to 1000 nm after the first drying step; comprising a method for manufacturing a positive electrode for a lithium-sulfur battery.
  2. In Article 1, The above (4) step A method for manufacturing a positive electrode for a lithium-sulfur battery, comprising the step of drying by irradiating a laser heat source in the form of surface light emission.
  3. In Article 1, The above (4) step A method for manufacturing a positive electrode for a lithium-sulfur battery, comprising the step of drying by irradiating a surface-emitting laser heat source with dimensions of 5 to 20 cm in width and 3 to 10 cm in length.
  4. In Article 1, The above (4) step A method for manufacturing a positive electrode for a lithium-sulfur battery, comprising the step of irradiating a laser heat source with an output of 160 to 750 W.
  5. In Article 1, The above (4) step A method for manufacturing a positive electrode for a lithium-sulfur battery, comprising the step of irradiating a laser heat source for 0.1 to 2 seconds.
  6. delete
  7. In Article 1, The above (4) step A method for manufacturing a positive electrode for a lithium-sulfur battery, comprising the step of irradiating a laser heat source having a cumulative energy density of 3 to 6 J/ cm² .
  8. In Article 1, When compared to the lithium-sulfur battery anode that has completed the first drying step (3) above A method for manufacturing a lithium-sulfur battery anode, wherein the sulfur loss rate of the lithium-sulfur battery anode after the second drying of step (4) above is 0.1 to 1.1 weight%.

Description

Method of manufacturing positive electrode for lithium-sulfur battery The present invention relates to a method for manufacturing a positive electrode for a lithium-sulfur battery, and specifically, to a method for manufacturing a positive electrode for a lithium-sulfur battery comprising a drying step using a laser heat source. As the range of applications for secondary batteries expands from small portable electronic devices to medium and large electric vehicles (EVs), energy storage systems (ESS), and electric ships, the demand for lithium secondary batteries with high capacity, high energy density, and long lifespan is surging. Among these, a lithium-sulfur battery refers to a battery system that uses a sulfur-based material with an 'S-S bond (Sulfur-Sulfur Bond)' as the positive electrode active material and lithium metal as the negative electrode active material. Sulfur, the main material of the aforementioned positive electrode active material, possesses characteristics such as having a low atomic weight and being abundant in resources, making it easy to procure and inexpensive to lower battery manufacturing costs, as well as being environmentally friendly due to its non-toxicity. In particular, lithium-sulfur batteries have a theoretical discharge capacity of 1,675 mAh/g-sulfur and can theoretically achieve a high energy storage density of 2,600 Wh/kg relative to weight. Because this is a very high figure compared to the theoretical energy densities of other battery systems currently under research (Ni-MH batteries: 450 Wh/kg, Li-FeS batteries: 480 Wh/kg, Li- MnO2 batteries: 1,000 Wh/kg, Na-S batteries: 800 Wh/kg) and lithium-ion batteries (250 Wh/kg), they are receiving significant attention in the market for medium and large-sized secondary batteries currently under development. The above lithium-sulfur battery has a positive electrode, a negative electrode, a separator, and an electrolyte as basic components, and among them, the positive electrode corresponds to the main components of the lithium-sulfur battery in that the positive electrode active material can have a significant impact on battery performance. The above positive electrode can be manufactured by first adding a binder and a solvent to the positive electrode active material to prepare a fluid form of positive electrode active material slurry, and then applying the slurry onto a current collector and drying it. Regarding the manufacturing process of the aforementioned lithium-sulfur battery, questions have been raised about the stability of the battery, as highly reactive lithium metal is used as the anode, and if moisture within the electrode is not sufficiently removed, side reactions between the anode and the electrolyte occur, accelerating battery degradation and potentially generating gas within the battery. To address this, various attempts have been made to remove moisture contained within the positive electrode of the lithium-sulfur battery. For example, there were attempts to apply the vacuum drying method used in lithium-ion batteries directly; however, the loss rate of sulfur, the active material, was high, and lowering the temperature or vacuum level to prevent this made it difficult to sufficiently remove moisture from the electrode. Furthermore, high-temperature drying methods caused problems where the active material was easily lost or melted due to the low melting and volatilization points of sulfur, leading to deformation of the electrode's shape itself. It has been pointed out that drying using conventional medium-wave infrared is not only ineffective in preventing sulfur loss but also requires a long drying time of several minutes; while improvements to the drying section and driving speed are necessary to address this, there are limitations in that additional spatial constraints must be considered to extend the drying section. Therefore, there is a need for research and development on a manufacturing method for lithium-sulfur battery cathodes that incorporates an improved drying method capable of minimizing the loss of sulfur contained in the cathode active material, while simultaneously improving cathode production speed by shortening drying time and ensuring excellent moisture content reduction through uniform heat transfer within the cathode and irradiating a large area at once. FIG. 1 is a schematic diagram showing a drying apparatus including a surface-emitting laser used during secondary drying for the manufacture of a positive electrode for a lithium-sulfur battery according to an embodiment of the present invention. Figure 2 is a graph showing the moisture content in the anode prepared according to the method for preparing a lithium-sulfur battery anode according to the embodiments and comparative examples of the present invention. FIGS. 3, FIGS. 4, and FIGS. 5 are graphs showing the sulfur content in a cathode prepared according to the method for preparing a cathode for a lithium-sulfur battery according