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EP-4738460-A1 - CATHODE MATERIAL FOR LITHIUM-SULFUR BATTERY AND LITHIUM-SULFUR BATTERY INCLUDING SAME

EP4738460A1EP 4738460 A1EP4738460 A1EP 4738460A1EP-4738460-A1

Abstract

The present disclosure relates to a carbon composite for use in a positive electrode of a lithium-sulfur battery and a method for producing the same, and the carbon composite includes a porous carbon material, and a catalyst located on at least one of an outer surface of the porous carbon material and an inner surface of pores of the porous carbon material, wherein the catalyst includes transition metal alloy particles and a carbon coating layer on at least part of a surface of the transition metal alloy particles, wherein the transition metal alloy particles include cobalt (Co) and iron (Fe), and wherein at least part of the carbon coating layer includes a crystalline carbon.

Inventors

  • JEONG, YO-CHAN
  • LEE, JINWOO
  • SON, Donghyeok
  • YANG, SEUNG-BO
  • LEE, CHANG-HOON
  • HAN, Seongjun

Assignees

  • LG Energy Solution, Ltd.
  • Korea Advanced Institute of Science and Technology

Dates

Publication Date
20260506
Application Date
20240912

Claims (17)

  1. A carbon composite comprising: a porous carbon material, and a catalyst located on at least one of an outer surface of the porous carbon material and an inner surface of pores of the porous carbon material, wherein the catalyst includes transition metal alloy particles and a carbon coating layer on at least part of a surface of the transition metal alloy particles, wherein the transition metal alloy particles include cobalt (Co) and iron (Fe), and wherein at least part of the carbon coating layer includes a crystalline carbon.
  2. The carbon composite according to claim 1, wherein the transition metal alloy particles include cobalt-iron alloy particles of body-centered cubic structure.
  3. The carbon composite according to claim 1, wherein an average particle size (D 50 ) of the carbon composite is in a range between 100 nm and 100 µ m.
  4. The carbon composite according to claim 1, wherein an average particle size (D 50 ) of the catalyst is 100 nm or less.
  5. The carbon composite according to claim 1, wherein a ratio of a thickness of the carbon coating layer to an average particle size (D 50 ) of the transition metal alloy particles is 40% or less.
  6. The carbon composite according to claim 1, wherein a thickness of the carbon coating layer is 10 nm or less.
  7. The carbon composite according to claim 1, wherein the carbon coating layer has a single layer structure or a multilayer structure of 10 or less layers.
  8. The carbon composite according to claim 1, wherein an amount of the catalyst is in a range between 5 wt% and 50 wt% based on 100 wt% of the carbon composite.
  9. The carbon composite according to claim 1, wherein the porous carbon material includes carbon nanotubes (CNT), graphene, graphene oxide (GO), reduced graphene oxide (rGO), carbon black, graphite, graphite nanofiber (GNF), carbon nanofiber (CNF), activated carbon fiber (ACF), activated carbon, fullerene, or two or more of them.
  10. The carbon composite according to claim 1, wherein the porous carbon material includes carbon nanotubes (CNT), and wherein the carbon nanotubes include entangled CNT.
  11. A method for producing the carbon composite according to any one of claims 1 to 10, the method comprising: mixing a cobalt (Co)-containing precursor, an iron (Fe)-containing precursor, a carbon layer precursor and a porous carbon material to obtain a transition metal-carbon layer precursor polymer/porous carbon material (M-CPP/C), and thermally treating the transition metal-carbon layer precursor polymer/porous carbon material to obtain the carbon composite.
  12. The method for producing the carbon composite according to claim 11, wherein the carbon layer precursor includes dopamine, polydopamine, melamine, 1,10-phenanthroline, polyaniline, carbon nitride (g-CN), glucose, phenylenediamine or a mixture thereof.
  13. The method for producing the carbon composite according to claim 11, wherein the thermal treatment is performed at a temperature ranging from 600°C to 1,000°C.
  14. A positive electrode active material comprising the carbon composite according to any one of claims 1 to 10, and a sulfur-based compound.
  15. A lithium-sulfur battery comprising: a positive electrode, a negative electrode and an electrolyte solution, wherein the positive electrode includes the positive electrode active material according to claim 14.
  16. The lithium-sulfur battery according to claim 15, wherein an E/S ratio is 8 µL/mg or less, and a sulfur loading in the positive electrode is 2.25 mg s /cm 2 or more, and wherein the E/S ratio indicates a ratio of a volume of the electrolyte solution and a sulfur weight in the positive electrode.
  17. The lithium-sulfur battery according to claim 15, wherein an E/S ratio is 3 µL/mg or less, and an energy density is 380 Wh/kg or more.

Description

TECHNICAL FIELD The present disclosure relates to a positive electrode material for a lithium-sulfur battery and a lithium-sulfur battery including the same. The present application claims priority to Korean Patent Application No. 10-2023-0125127 filed on September 19, 2023 and Korean Patent Application No. 10-2024-0119502 filed on September 3, 2024 in the Republic of Korea, the disclosures of which are incorporated herein by reference. BACKGROUND A lithium-sulfur battery is a battery system using a sulfur-based material having a sulfur-sulfur (S-S) bond as a positive electrode active material and a lithium metal as a negative electrode active material. Sulfur, a main component of the positive electrode active material, is abundant in nature and can be found around the world, is non-toxic and has low atomic weight. As secondary batteries are used in a wide range of applications including electric vehicles (EVs) and energy storage systems (ESSs), attention is drawn to lithium-sulfur batteries theoretically having higher energy storage density by weight (~2,600 Wh/kg) than lithium-ion secondary batteries having lower energy storage density by weight (~250 Wh/kg). During discharging, lithium-sulfur batteries undergo oxidation at the negative electrode active material, lithium, by releasing electrons into lithium cation, and reduction at the positive electrode active material, the sulfur-based material, by accepting electrons. Through the reduction reaction, the sulfur-based material is converted to sulfur anion by the S-S bond accepting two electrons. The lithium cation produced by the oxidation reaction of lithium migrates to the positive electrode via an electrolyte, and bonds with the sulfur anion produced by the reduction reaction of the sulfur-based compound to form a salt. Specifically, sulfur before the discharge has a cyclic S8 structure, and it is converted to lithium polysulfide (Li2Sx) through the reduction reaction and is completely reduced to lithium sulfide (Li2S). Meanwhile, the amount of the electrolyte solution in a lithium-sulfur battery is the most important factor to be considered among many factors that determine the price and energy density of the lithium-sulfur battery. First, generally, in the materials of which the lithium-sulfur battery is made, because the lithium-sulfur battery includes the very thin lithium negative electrode and the electrolyte solution based on a high-priced lithium salt, the manufacturing cost of the lithium-sulfur battery is quite high. In contrast, the energy density of the lithium-sulfur battery relies on how much energy the manufactured cell produces compared to the total weight, and a ratio of the total cell weight to the energy produced is affected by sulfur loading per unit area at the positive electrode and the ratio of sulfur in the composite, but is more greatly affected by a ratio of electrolyte to sulfur (E/S) or a ratio of the amount of the electrolyte solution to the amount of sulfur in the positive electrode. Additionally, the ratio of the energy produced to the total cell weight is more greatly affected by capacity resulting from lithium-sulfur electrochemical reaction than the operating voltage. Accordingly, it is necessary to design stable lithium-sulfur batteries to minimize the amount of the electrolyte solution and achieve high reversible capacity in cells having low E/S ratios. In particular, since sulfur used in the positive electrode active material is nonconductive, the migration of electrons produced by electrochemical reaction is inhibited, and there are problems with the elution of polysulfide (LiSx) during charging and discharging and degradation in battery life and rate characteristics caused by slow kinetic activity in the electrochemical reaction due to low electrical conductivity of sulfur and lithium sulfide. In these circumstances, recently, many studies have been made to improve the performance of lithium-sulfur secondary batteries by improving the kinetic activity in the redox reaction of sulfur during charging and discharging by use of platinum (Pt) which has been primarily used as electrochemical catalysts. However, noble metal catalysts such as platinum are difficult to commercialize due to high costs and have poisoning risks by the redox reaction of sulfur during charging and discharging, so it is not easy to use as positive electrode materials of lithium-sulfur secondary batteries. Accordingly, there is a need for development of positive electrode materials for improving the kinetic activity in the electrochemical reaction during charge and discharge of lithium-sulfur secondary batteries and the cost efficiency for commercialization. DISCLOSURE Technical Problem The present disclosure is designed to solve the above-described problem, and therefore, the present disclosure is directed to providing a positive electrode material with improved lithium polysulfide adsorption and increased kinetic activity in the redox reaction