EP-4333107-B1 - POSITIVE ELECTRODE MATERIAL FOR LITHIUM-SULFUR BATTERY AND LITHIUM-SULFUR BATTERY COMPRISING THE SAME

EP4333107B1EP 4333107 B1EP4333107 B1EP 4333107B1EP-4333107-B1

Inventors

JEONG, YO-CHAN
LEE, CHANG-HOON
YANG, SEUNG-BO

Dates

Publication Date: 20260506
Application Date: 20230620

Claims (12)

A positive electrode active material, comprising: a) particles A comprising a first porous carbon material, at least part of the first porous carbon material is crystalline, and catalyst particles deposited on the first porous carbon material; and b) particles B comprising a second porous carbon material, at least part of the second porous carbon material is crystalline, and sulfur infiltrated into the second porous carbon material, wherein the particles A and the particles B have different morphologies; the morphology of the particle represents a form, a shape, or a physiochemical or biochemical structure of the particle; a surface of at least some of the particles B is covered by the particles A, and wherein a coverage area of the particles B by the particles A is 20% to 50% of an entire outer area of the particles B; the first porous carbon material and the second porous carbon material are independently selected from at least one of carbon nanotubes (CNT), graphene, graphene oxide (GO), reduced graphene oxide (rGO), carbon black, graphite, graphite nanofiber (GNF), carbon nanofiber (CNF), activated carbon fiber (ACF), natural graphite, artificial graphite, expanded graphite, activated carbon or fullerene; the catalyst particles comprise vanadium nitride; or the catalyst particles comprise at least one of cobalt (Co) or iron (Fe).
The positive electrode active material according to claim 1, wherein a sphericity of the particles B is larger than a sphericity of the particles A; wherein the sphericity is defined according to the following equation 1: Ψ = π 1 3 6 V p 2 3 A p where Ψ denotes the sphericity, V p denotes a volume of the particle measured as set forth in the description, and A p denotes a surface area of the particle measured as set forth in the description.
The positive electrode active material according to claim 1 or 2, wherein 50% or more of the particles A cover at least a part of a surface of the particles B.
The positive electrode active material according to any of the claims 1 to 3, wherein a specific surface area of the particles A is larger than a specific surface area of the particles B, wherein the specific surface area is measured by BET method as set forth in the description.
The positive electrode active material according to any of the claims 1 to 4, wherein the particles A and the particles B are in contact with each other in at least one location at which the catalyst particles included in the particles A are present.
The positive electrode active material according to any of the claims 1 to 5, wherein a weight of the sulfur is 60 weight% to 90 weight% based on a total weight of the first porous carbon material and the second porous carbon material.
The positive electrode active material according to any of the claims 1 to 6, wherein the first porous carbon material and the second porous carbon material are different materials.
The positive electrode active material according to any of the claims 1 to 7, wherein the first porous carbon material and the second porous carbon material are a same material.
The positive electrode active material according to any of the claims 1 to 8, wherein each of the first porous carbon material and the second porous carbon material independently comprises at least one of bundled carbon nanotubes (CNT), entangled CNT or reduced graphene oxide (rGO).
The positive electrode active material according to any of the claims 1 to 9, wherein an elasticity measured as set forth in the description of each of the first porous carbon material and the second porous carbon material is larger than an elasticity measured as set forth in the description of an amorphous carbon material according to the definition provided in the description.
The positive electrode active material according to any of the claims 1 to 10, wherein an electrical conductivity of each of the first porous carbon material and the second porous carbon material is larger than an electrical conductivity of an amorphous carbon material according to the definition provided in the description.
A lithium-sulfur battery, comprising: a positive electrode, a negative electrode, a separator between the positive electrode and the negative electrode; and a nonaqueous electrolyte solution, wherein the positive electrode comprises a positive electrode active material and the positive electrode active material is defined in any one of the claims 1 to 11.

Description

TECHNICAL FIELD The present application claims priority to Korean Patent Application No. 10-2022-0110413 filed on August 31, 2022 No. 10-2023-0025408 filed on February 24, 2023, No. 10-2022-0110385 filed on August 31, 2022, No. 10-2022-0187899 filed on December 28, 2022 and No.10-2023-0042283 filed on March 30, 2023 in the Republic of Korea. The present disclosure relates to a positive electrode active material for a lithium-sulfur battery and a lithium-sulfur battery comprising the same. BACKGROUND ART A lithium-sulfur battery is a battery system using a sulfur-based material having a sulfur-sulfur (S-S) bond for a positive electrode active material and a lithium metal for 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) by the reduction reaction and is completely reduced to lithium sulfide (Li2S). Since sulfur used in the positive electrode active material is nonconductive, electrons generated by electrochemical reaction cannot move, and elusion of poly sulfide (LiSx) occurs during charging·discharging and low electrical conductivity of sulfur and lithium sulfide slows down the dynamics of electrochemical reaction, which degrades the battery life characteristics and rate characteristics. In these circumstances, recently, studies have been made to use platinum (Pt) that has been primarily used as an electrochemical catalyst to improve the dynamics of oxidation and reduction reactions of sulfur during charging·discharging of lithium-sulfur secondary batteries so as to improve the performance of the lithium-sulfur secondary batteries. However, since noble metal catalysts such as platinum are expensive, the high cost is the obstacle to the commercialization, and there are poisoning risks by oxidation and reduction reactions of sulfur during charging and discharging, so it is not easy to use as a positive electrode material of lithium-sulfur secondary batteries. Accordingly, there is a need for technology development of positive electrode materials that improve the dynamics of electrochemical reaction during charging and discharging of lithium-sulfur secondary batteries and can be commercialized with cost efficiency. Zhang et al., Adv. Energy Mater., 2017, 7, 1602543, discloses a sulfur/carbon composite based on 3D graphene nanosheet@carbon nanotube matrix as cathode for a lithium-sulfur battery. DISCLOSURE Technical Problem The present disclosure is directed to providing a new type of positive electrode active material for use in positive electrodes of lithium-sulfur batteries. Especially, it is an object of the present invention to positive electrode active material for use in a positive electrode of a lithium-sulfur battery overcoming drawbacks of the prior art, especially for improving the performance of the lithium-sulfur battery. Technical Solution To solve the above-described problem, according to an aspect of the present disclosure, there is provided a positive electrode active material of the following embodiments, wherein one or more of the embodiments may be combined with each other to realize the invention. The technical solution is subject of the independent claims. Further embodiments result from the subclaims and the following written description. Advantageous Effects The positive electrode active material according to an embodiment of the present disclosure is a new type for used in secondary batteries, especially lithium-sulfur batteries. Specifically, the positive electrode active material according to one or more embodiment(s) of the present invention is a new type of positive electrode active material suitable to significantly improve the loading amount and catalytic activity of sulfur. It is, therefore, possible to improve the performance of a secondary batte