EP-4738477-A1 - NEGATIVE ELECTRODE FOR LITHIUM-FREE SECONDARY BATTERY, MANUFACTURING METHOD THEREFOR, AND LITHIUM-FREE SECONDARY BATTERY COMPRISING SAME

EP4738477A1EP 4738477 A1EP4738477 A1EP 4738477A1EP-4738477-A1

Abstract

The present disclosure relates to a negative electrode for lithium-free secondary battery that can reduce side reactions on the negative electrode and improve the electrochemical characteristics and lifetime characteristics of a lithium-free secondary battery even while achieving reduction in weight and thickness, a preparation method thereof, and a lithium-free secondary battery comprising the same.

Inventors

KIM, Sanha
YANG, Inyeong
WON, Dongyeon

Assignees

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

Dates

Publication Date: 20260506
Application Date: 20241126

Claims (20)

A negative electrode for lithium-free secondary battery, comprising: a porous metal layer having a three-dimensional microstructure; and a conductive carbon nanostructure formed on the porous metal layer, wherein the porous metal layer comprises a metal mesh layer in which a fibrous metal having a diameter of a micron scale forms a network structure, and a metal nanostructure formed on the fibrous metal, and wherein at least some of the metal nanostructures are connected to each other to define a plurality of pores on the porous metal layer.
The negative electrode for lithium-free secondary battery of claim 1, further comprising a conductive metal layer supporting the porous metal layer.
The negative electrode for lithium-free secondary battery of claim 1, wherein the porous metal layer comprises copper.
The negative electrode for lithium-free secondary battery of claim 1, wherein the metal nanostructure comprises a metal nanorod or a metal nanofiber.
The negative electrode for lithium-free secondary battery of claim 1, wherein the conductive carbon nanostructure comprises a carbon nanotube.
The negative electrode for lithium-free secondary battery of claim 1, wherein the porous metal layer has a thickness 10 to 30µm.
The negative electrode for lithium-free secondary battery of claim 1, wherein the porous metal layer has a mass per unit area of 4.0 to 10.0 mg/cm 2 .
The negative electrode for lithium-free secondary battery of claim 4, wherein the fibrous metal has a diameter of 5 to 15µm, and the metal nanorod or metal nanofiber has a diameter of 100 to 700 nm.
The negative electrode for lithium-free secondary battery of claim 1, wherein the porous metal layer has a porosity of 55 to 70%.
The negative electrode for lithium-free secondary battery of claim 1, wherein the porous metal layer is made from a conductive metal in a reduced form, and is substantially free of an oxide of the conductive metal.
The negative electrode for lithium-free secondary battery of claim 1, further comprising a catalyst layer comprising aluminum or iron and formed on the porous metal layer, wherein the conductive carbon nanostructure is formed on the catalyst layer.
A method for preparing the negative electrode for lithium-free secondary battery of claim 1, the method comprising the steps of: performing an electrochemical etching on a metal mesh containing a conductive metal; re-depositing the conductive metal on the metal mesh on which the electrochemical etching has been performed, thereby forming a porous metal layer in which a metal nanostructure is formed on a fibrous metal having a network structure; and forming a carbon nanostructure while supplying a gaseous carbon source including an aliphatic hydrocarbon and a reducing gas in the presence of a metal catalyst.
The method for preparing the negative electrode for lithium-free secondary battery of claim 12, wherein the metal mesh comprises a metal wire having a diameter of 20 to 40 um, and has a mesh size of 200 to 500 mesh.
The method for preparing the negative electrode for lithium-free secondary battery of claim 12, wherein the electrochemical etching and the re-depositing the conductive metal are sequentially performed in the same electrolytic cell, comprising: a working electrode containing the metal mesh, a counter electrode containing the same conductive metal as the metal mesh, and an electrolyte containing ions of the conductive metal and an acid.
The method for preparing the negative electrode for lithium-free secondary battery of claim 12, wherein the electrochemical etching is performed under application of a constant current of 30 to 60 mA/cm 2 .
The method for preparing the negative electrode for lithium-free secondary battery of claim 12, wherein the re-deposition of the conductive metal is performed under application of a voltage of 2.2 V to 2.7 V.
The method for preparing the negative electrode for lithium-free secondary battery of claim 12, further comprising heat-treating the metal mesh or porous metal layer in the presence of hydrogen gas before the electrochemical etching or after the re-deposition of the conductive metal.
The method for preparing the negative electrode for lithium-free secondary battery of claim 17, wherein the heat treatment is performed after the re-deposition of the conductive metal, and the formation of the carbon nanostructure is continuously performed in the same reactor in which the heat treatment has been performed.
The method for preparing the negative electrode for lithium-free secondary battery of claim 17, wherein the heat treatment is performed at a temperature of 300 to 800°C for 5 minutes to 1.5 hours.
The method for preparing the negative electrode for lithium-free secondary battery of claim 12, wherein the metal catalyst comprises aluminum oxide and iron.

Description

[TECHNICAL FIELD] Cross-Reference to Related Application(s) This application claims priority to and the benefit of Korean Patent Application no. KR10-2023-0168063, filed on November 28, 2023 and Korean Patent Application no. KR10-2024-0165866, filed on November 20, 2024, the entire contents of which are incorporated herein by reference. The present disclosure relates to a negative electrode for lithium-free secondary battery that can reduce side reactions on the negative electrode, and can improve the electrochemical characteristics and lifetime characteristics of a lithium-free secondary battery, even while achieving reduction in thickness and weight, a preparation method thereof, and a lithium-free secondary battery comprising the same. [BACKGROUND ART] Lithium metal battery is a battery to which a negative electrode active material made from lithium metal (Li-metal) material is applied, and has the advantage of having a theoretically very high energy density and capacity as compared with a battery to which a graphite-based negative electrode is applied according to the prior art. Thus, research and development are ongoing to apply such a lithium metal battery to a battery that requires a high energy density. However, lithium metal batteries still have problems such as high side reactions and low reversibility that are not settled yet. Therefore, in order to compensate for the low reversibility of lithium metal batteries, attempts have been made to store excessive lithium in the negative electrode in advance and operate the lithium metal battery. However, as the N/P ratio of the secondary battery increases, the energy density of the lithium metal battery may decrease significantly, and cost and safety problems arise due to the excessive lithium, so these attempts have run up against limitations. Recently, there is a growing interest in a negative electrode-free secondary battery, also known as a lithium-free secondary battery or an anode-free secondary battery. This lithium-free secondary battery refers to a secondary battery that does not form a separate lithium metal layer on the negative electrode current collector during the preparation process, but includes the negative electrode current collector itself as the negative electrode. The lithium-free secondary battery can be defined as a battery that utilize lithium metal as the negative electrode active material, since lithium metal is electrodeposited on the negative electrode current collector at the time of charge. The lithium-free secondary battery can maximize the use of the high energy density of lithium metal while reducing safety issues caused by an excessive amount of lithium storage. However, in the case of such a negative electrode for lithium-free secondary battery, since the negative electrode current collector is not completely covered by a lithium metal layer and only a limited amount of lithium metal is utilized as the negative electrode active material, many side reactions including galvanic corrosion and rapid capacity loss may occur in the negative electrode. In addition, the negative electrode may exhibit problems in that lithium metal is unevenly deposited and grown on the negative electrode current collector, resulting in the formation of lithium dendrites. Previously, in order to induce uniform growth of lithium on the negative electrode current collector and suppress the formation of lithium dendrites, the method of expanding the surface area of the negative electrode by forming a three-dimensional porous microstructure on the negative electrode current collector has been studied. However, most existing negative electrodes for lithium-free secondary batteries inevitably had a large thickness and weight in order to form a three-dimensional porous microstructure on the metal current collector. For this reason, when applied to such a negative electrode for lithium-free secondary battery, there is a drawback in that the energy density per volume of the battery was greatly reduced. In addition, there still exist the drawbacks in that due to the large surface area of the negative electrode, side reactions between the current collector and the lithium metal and electrolyte electrodeposited at the time of charge may be further increased, which may significantly reduce the initial capacity of the secondary battery, and accelerates galvanic corrosion, and deteriorates lifetime characteristics of the secondary battery. [DETAILED DESCRIPTION OF THE INVENTION] [Technical Problem] Therefore, it is an object of the present disclosure to provide a negative electrode for lithium-free secondary battery that can reduce galvanic corrosions and side reactions on the negative electrode and enables uniform electrodeposition of a lithium metal, even while achieving reduction in thickness and weight, and a preparation method thereof. It is another object of the present disclosure to provide a lithium-free secondary battery that comprises the negative el