EP-4273967-B1 - PREPARATION METHOD FOR A POROUS CARBON MATERIAL HAVING IMPURITIES REMOVED THEREFROM

EP4273967B1EP 4273967 B1EP4273967 B1EP 4273967B1EP-4273967-B1

Inventors

SONG, Myeongjun
PARK, Intae
CHOI, RAN
LEE, HYUNSOO
KIM, Yonghwi
PARK, Seonghyo
YANG, Seungbo

Dates

Publication Date: 20260506
Application Date: 20221124

Claims (4)

A method for preparing a porous carbon material from which impurities were removed, which comprises the steps of (a) putting a porous carbon material having a specific surface area of 200 to 1,700 m 2 /g into an airtight container, and then purging by injecting an inert gas; and (b) applying microwaves to the porous carbon material; wherein in step (b), the microwaves are applied to the porous carbon material under the condition that MPPT according to Equation 1 below is 2,000 to 10,000 W*s/g: MPPT W * s / g = Microwave Power W × Times S / Weight of carbon material g wherein the Times is the amount of time in seconds during which the microwaves are applied, and it is in excess of 10 seconds.
The method for preparing a porous carbon material according to claim 1, wherein the porous carbon material is selected from the group consisting of carbon nanotubes; graphene (multilayer graphene flake, MGF); graphite; carbon black selected from the group consisting of carbon black, acetylene black, Ketjen black, Denka black, thermal black, channel black, furnace black and lamp black; carbon fiber; and a mixture containing two or more of them.
The method for preparing a porous carbon material according to claim 2, wherein the porous carbon material is selected from the group consisting of carbon nanotubes, graphene (multilayer graphene flake, MGF), carbon black and Ketjen black.
The method for preparing a porous carbon material according to claim 1, wherein the pore volume of the porous carbon material is 1.5 cm 3 /g or more.

Description

[Technical Field] The present invention relates to a porous carbon material from which impurities were removed, its preparation method, a positive electrode for a lithium-sulfur battery comprising the carbon material as a positive electrode active material and a lithium-sulfur battery, and more particularly to a porous carbon material from which impurities were removed, which can improve the charging overvoltage problem of a lithium-sulfur battery by applying a porous carbon material, from which impurities such as moisture were removed through pre-treatment, to a positive electrode for the lithium-sulfur battery, and its preparation method, a positive electrode for a lithium-sulfur battery comprising the carbon material as a positive electrode active material and a lithium-sulfur battery. [Background Art] As interest in energy storage technology continues to increase, since its application is expanding from energy for mobile phones, tablets, laptops and camcorders to even energy for electric vehicles (EVs) and hybrid electric vehicles (REVs), research and development of electrochemical devices are gradually increasing. The field of electrochemical devices is an area that is receiving the most attention in this respect. Among them, the development of secondary batteries such as a lithium-sulfur battery capable of being charged/discharged has become a focus of attention. In recent years, in developing these batteries, in order to improve capacity density and specific energy, it has led to research and development in designs for new electrodes and batteries. Among these electrochemical devices, a lithium-sulfur battery (Li-S battery) has a high energy density (theoretical capacity) and thus is in the spotlight as a next-generation secondary battery that can replace a lithium-ion battery. In such a lithium-sulfur battery, a reduction reaction of sulfur and an oxidation reaction of lithium metal occur during discharging. In this case, sulfur forms lithium polysulfide (LiPS) having a linear structure from S8 having a ring structure. This lithium-sulfur battery is characterized by showing a stepwise discharging voltage until the polysulfide is completely reduced to Li2S. However, the biggest obstacle of the lithium-sulfur battery in the commercialization is the lifetime, and the charging/discharging efficiency is reduced during the charging/discharging process, and the lifetime of the battery is deteriorated. There are various reasons for the deterioration of the lifetime of the lithium-sulfur battery, such as side reactions of electrolytes (sedimentation of by-products following the decomposition of the electrolyte), instability of lithium metal (dendrite grows on the lithium negative electrode, resulting in a short circuit), and sedimentation of by-products from the positive electrode (leaching of the lithium polysulfide from the positive electrode). That is, in a battery using a sulfur-based compound as a positive electrode active material and an alkali metal such as lithium as a negative electrode active material, leaching and shuttle phenomena of lithium polysulfide are occurred during the charging/discharging, and the lithium polysulfide is transferred to the negative electrode, reducing the capacity of the lithium-sulfur battery, and as a result, there is a big problem that the lithium-sulfur battery has a reduced lifetime and reduced reactivity. That is, since the polysulfide leached from the positive electrode has a high solubility in the organic electrolyte, unwanted movement (PS shuttling) may occur toward the negative electrode through the electrolyte, and as a result, a decrease in capacity due to irreversible loss of the positive electrode active material and a decrease in the lifetime of the battery due to deposition of sulfur particles on the surface of lithium metal due to side reactions are occurred. On the other hand, in order to build a lithium-sulfur battery with a high energy density of about 400 Wh/kg or more or 600 Wh/L or more, an electrolyte and positive electrode active material system that can operate even under conditions of high loading (about 4.0 mAh/cm2 or more) and low porosity (about 60% or less) is required. That is, the behavior of such a lithium-sulfur battery can vary greatly depending on the electrolyte. The electrolyte when sulfur in the positive electrode is leached into the electrolyte in the form of lithium polysulfide (LiPS) is called catholyte and the electrolyte when sulfur hardly leaches out in the form of lithium polysulfide is called sparingly solvating electrolyte (SSE). Since the lithium-sulfur battery utilizing the existing catholyte system is dependent on the liquid phase reaction through the production of an intermediate product (intermediate polysulfide) in the form of Li2Sx (catholyte type), there is a problem that it does not fully utilize sulfur's high theoretical discharging capacity (1,675 mAh/g), and rather, the lifetime of the battery is drastically red