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EP-4261928-B1 - POSITIVE ELECTRODE FOR LITHIUM SECONDARY BATTERY AND LITHIUM SECONDARY BATTERY COMPRISING SAME

EP4261928B1EP 4261928 B1EP4261928 B1EP 4261928B1EP-4261928-B1

Inventors

  • Cho, Hyunah
  • AHN, Jeehyun
  • LEE, CHANGHOON

Dates

Publication Date
20260506
Application Date
20221027

Claims (8)

  1. A positive electrode for a lithium secondary battery, the positive electrode comprising a positive electrode active material layer, wherein the positive electrode active material layer comprises a sulfur-carbon composite which is a positive electrode active material, a binder, and a metal oxide-based additive; wherein the metal oxide-based additive comprises niobium tungsten oxide; and the metal oxide-based additive is contained in an amount of 2 to 10% by weight based on the total weight of the positive electrode active material layer.
  2. The positive electrode according to claim 1, wherein the binder comprises one or more selected from the group consisting of styrene-butadiene rubber (SBR)/carboxymethyl cellulose (CMC), poly(vinyl acetate), polyvinyl alcohol, polyethylene oxide, polyvinyl pyrrolidone, alkylated polyethylene oxide, crosslinked polyethylene oxide, polyvinyl ether, poly(methyl methacrylate), polyvinylidene fluoride, copolymer of polyhexafluoropropylene and polyvinylidene fluoride, poly(ethyl acrylate), polytetrafluoroethylene, polyvinylchloride, polyacrylonitrile, polyvinylpyridine, polystyrene, polyacrylic acid, derivatives thereof, blends thereof, and copolymers thereof.
  3. The positive electrode according to claim 1, wherein the positive electrode active material layer is formed on at least one surface of the positive electrode current collector.
  4. The positive electrode according to claim 3, wherein the positive electrode current collector comprises stainless steel, aluminum, nickel, titanium, or sintered carbon.
  5. A lithium secondary battery comprising the positive electrode of claim 1, a negative electrode, and an electrolyte solution.
  6. The lithium secondary battery according to claim 5, wherein the negative electrode comprises lithium metal.
  7. The lithium secondary battery according to claim 6, wherein the lithium secondary battery is a lithium-sulfur secondary battery.
  8. The lithium secondary battery according to claim 6, wherein the lithium secondary battery is a pouch-type lithium secondary battery.

Description

Field of Disclosure This application is a National Stage Application of International Application No. PCT/KR2022/016525, filed on October 27, 2022, which claims the benefit of priority based on Korean Patent Application No. 2021-0159053, filed on November 18, 2021. The present disclosure relates to a positive electrode for a lithium secondary battery and a lithium secondary battery comprising the same. Background Recently, with the rapid development in the field of electronic devices and electric vehicles, the demand for secondary batteries is increasing. Particularly, with the trend toward miniaturization and weight reduction of portable electronic devices, there is a growing demand for secondary batteries having a high energy density that can cope with them. Among the secondary batteries, a lithium-sulfur secondary battery is a secondary battery that uses sulfur-based compounds having a sulfur-sulfur bond as a positive electrode active material, and uses alkali metals such as lithium, carbon-based materials in which intercalation and deintercalation of metal ions such as lithium ions occur, or silicon or tin, which forms an alloy with lithium, as a negative electrode active material. Specifically, in the case of the lithium-sulfur secondary battery, during the discharging which is a reduction reaction, as the sulfur-sulfur bond is cut off, the oxidation number of sulfur decreases, and during the charging which is an oxidation reaction, as the oxidation number of sulfur increases, the sulfur-sulfur bond is re-formed. Through this oxidation-reduction reaction, electrical energy is stored and generated. Particularly, in the case of lithium-sulfur secondary batteries, sulfur used as a positive electrode active material in the lithium-sulfur secondary batteries has a theoretical energy density of 1.675 mAh/g, and thus has a theoretical energy density of about five times higher than the positive electrode active material used in conventional lithium secondary batteries, and thus they are batteries capable of expressing high power and high energy density. In addition, since sulfur has the advantage of being cheap and rich in resources and thus being readily available and environmentally friendly, sulfur is drawing attention as an energy source not only for portable electronic devices but also for medium- and large- devices such as electric vehicles. However, in the lithium-sulfur secondary battery, polysulfide is formed and leached at the positive electrode during operation, and a shuttling phenomenon may occur, and thus there is a problem that the positive electrode active material is irreversibly lost and the lifetime characteristics of the battery are lowered. In order to solve the problem of degradation of the lifetime characteristics of the lithium-sulfur secondary battery, researches are being conducted on adding polysulfide adsorbents or redox mediators to the positive electrode or coating the surface of the separator with polysulfide adsorbing or repelling materials, etc. For example, Japanese Laid-open Patent Publication No. 2004-179160 and Korean Laid-open Patent Publication No. 2015-046861 disclose a positive electrode for a lithium-sulfur secondary battery containing an inorganic additive, but there are some limitations in improving the lifetime characteristics of the battery. Therefore, there is a continuing demand for the development of materials that can exhibit significant effects in improving the lifetime characteristics of a lithium-sulfur secondary battery. Related Art Japanese Patent Publication No. 2004-179160Korean Patent Publication No. 2015-046861KR 2019 0051448 A discloses a method for manufacturing maghemite. More specifically, crystalline lepidocrocite (γ-FeOOH) is manufactured by controlling a reaction time and a reaction temperature of NaBH4 and Fe(NO3)3 · 9 H2O, and then thermally treating the same in a non-active gas condition to manufacture a high purity of maghemite (γ-Fe2O3).LIU SHOUFA ET AL: "Electrochemical behavior study of carbon nanofiber/ MnO composites as sulfur host for highly effective polysulfide absorbent", IONICS, vol. 27, no. 1 , pages 207-212. Summary The inventors of the present disclosure have confirmed that if niobium tungsten oxide, which is a metal oxide-based additive, is added to the positive electrode for the lithium-sulfur secondary battery, the discharging capacity of the positive electrode and the lifetime characteristics of the battery are improved. Therefore, it is an object of the present disclosure to provide a positive electrode for a lithium secondary battery with improved discharging capacity and lifetime characteristics. It is another object of the present disclosure to provide a lithium secondary battery comprising the positive electrode for the lithium secondary battery having excellent discharging capacity and lifetime characteristics. The above objects are achieved in accordance with the subject-matter of the independent claims. Further embod