KR-20260066938-A - NEGATIVE ELECTRODE FOR LITHIUM SECONDARY BATTERY, METHOD FOR PREPARING LITHIUM SECONDARY BATTERY, AND LITHIUM SECONDARY BATTERY COMPRISING NEGATIVE ELECTRODE

KR20260066938AKR 20260066938 AKR20260066938 AKR 20260066938AKR-20260066938-A

Abstract

The present application relates to a negative electrode for a lithium secondary battery, a method for manufacturing a lithium secondary battery, and a lithium secondary battery comprising a negative electrode.

Inventors

박인복
전찬수
박승원
이상민

Assignees

주식회사 엘지에너지솔루션

Dates

Publication Date: 20260512
Application Date: 20241105

Claims (13)

A negative electrode for a lithium secondary battery comprising: a negative electrode current collector layer; and a negative electrode active material layer comprising a silicon-based active material provided on one or both sides of the negative electrode current collector layer. The above negative electrode active material layer comprises a first negative electrode active material layer; and a second negative electrode active material layer formed on the first negative electrode active material layer. The ratio of the second cathode active material layer to the above cathode active material layer is 30% or less, and The silicon-based active material in the above negative electrode active material layer comprises 1 part by weight or more and 30 parts by weight or less, and A negative electrode for a lithium secondary battery having a capacity proportion of 25% or more and 100% or less based on the total capacity of the second negative electrode active material layer, achieved by the silicon-based active material in the second negative electrode active material layer.
In claim 1, The ratio of the second cathode active material layer to the above cathode active material layer is 1% or more and 30% or less, and A negative electrode for a lithium secondary battery having a ratio of the first negative electrode active material layer to the above negative electrode active material layer of 70% or more and 99% or less.
In claim 1, A negative electrode for a lithium secondary battery, wherein the silicon-based active material comprises 10 parts by weight or more and 30 parts by weight or less based on 100 parts by weight of the second negative electrode active material layer.
In claim 1, A negative electrode for a lithium secondary battery comprising 10 parts by weight or less of the silicon-based active material based on 100 parts by weight of the first negative electrode active material layer.
In claim 1, A negative electrode for a lithium secondary battery, wherein the negative electrode active material layer further comprises one or more mixtures selected from the group consisting of carbon-based active materials, metal-based active materials capable of alloying with lithium, and lithium-containing nitrides.
In claim 5, A negative electrode for a lithium secondary battery comprising, based on 100 parts by weight of the negative electrode active material layer, 1 part by weight or more and 30 parts by weight or less of a silicon-based active material; and 70 parts by weight or more and 99 parts by weight or less of a carbon-based active material.
In claim 1, The above silicon-based active material comprises one or more selected from the group consisting of SiOx (0<x<2), Si/C, and Si alloys, for a negative electrode for a lithium secondary battery.
In claim 1, The above silicon-based active material is a negative electrode for a lithium secondary battery comprising Si/C.
anode; A negative electrode for a lithium secondary battery according to any one of claims 1 to 8; A separator provided between the anode and the cathode; and A lithium secondary battery containing an electrolyte.
Step of preparing a negative electrode for a lithium secondary battery; and A method for manufacturing a lithium secondary battery comprising the step of assembling a negative electrode; a positive electrode; a separator; and an electrolyte for the lithium secondary battery, wherein The step of preparing a negative electrode for a lithium secondary battery comprises: a step of preparing a negative electrode current collector layer; a step of forming a first negative electrode active material layer by applying a first negative electrode active material layer composition to one or both sides of the negative electrode current collector layer to form a first negative electrode active material layer, and a step of forming a negative electrode active material layer by applying a second negative electrode active material layer composition to the upper portion of the first negative electrode active material layer to form a second negative electrode active material layer. The ratio of the second cathode active material layer to the above cathode active material layer is 30% or less, and The silicon-based active material in the above negative electrode active material layer comprises 1 part by weight or more and 30 parts by weight or less, and A method for manufacturing a lithium secondary battery in which the proportion of capacity realized by the silicon-based active material in the second negative electrode active material layer is 25% or more and 100% or less based on the total capacity of the second negative electrode active material layer.
In claim 10, The method includes the step of pre-lithiating a cathode having a first cathode active material layer and a second cathode active material layer formed on the cathode current collector layer. A method for manufacturing a lithium secondary battery, wherein the step of pre-lithiating the above-mentioned cathode comprises a lithium electrolytic plating process; a lithium metal transfer process; a lithium metal deposition process; or a stabilized lithium metal powder (SLMP) coating process.
In claim 10, The step of forming the second cathode active material layer on the first cathode active material layer includes a wet-on-dry process, and The above wet-on-dry process includes the step of applying a first cathode active material layer composition; A step of forming a first cathode active material layer by partially drying or fully drying the above-described coated first cathode active material layer composition; and A method for manufacturing a lithium secondary battery comprising the step of applying the above-mentioned second negative electrode active material layer composition to the above-mentioned first negative electrode active material layer.
In claim 10, The step of forming the second cathode active material layer on the first cathode active material layer includes a wet-on-wet process, and The above wet-on-wet process comprises the step of applying a first cathode active material layer composition; and A method for manufacturing a lithium secondary battery comprising the step of applying the second negative electrode active material layer composition to the first negative electrode active material layer composition while the first negative electrode active material layer composition is in an undried state.

Description

Negative electrode for lithium secondary battery, method for preparing lithium secondary battery, and lithium secondary battery comprising a negative electrode The present application relates to a negative electrode for a lithium secondary battery, a method for manufacturing a lithium secondary battery, and a lithium secondary battery comprising a negative electrode. Due to the rapid increase in the use of fossil fuels, there is a growing demand for alternative or clean energy. As part of this effort, the fields of power generation and energy storage utilizing electrochemical reactions are the most actively researched. Currently, a representative example of an electrochemical device utilizing such electrochemical energy is the secondary battery, and its scope of application is steadily expanding. With the increasing technological development and demand for mobile devices, the demand for secondary batteries as an energy source is rapidly rising. Among these secondary batteries, lithium-ion batteries, which possess high energy density and voltage, long cycle life, and low self-discharge rates, have been commercialized and are widely used. Furthermore, active research is being conducted on methods to manufacture high-density electrodes with higher energy density per unit volume for use in such high-capacity lithium-ion batteries. Generally, a secondary battery consists of a positive electrode, a negative electrode, an electrolyte, and a separator. The negative electrode includes a negative electrode active material that inserts and extracts lithium ions from the positive electrode, and silicon-based particles with a large discharge capacity may be used as the negative electrode active material. In particular, driven by the recent demand for high-density energy batteries, active research is being conducted on methods to increase capacity by using silicon-based compounds, such as Si/C or SiOx, as anode active materials. These compounds possess a capacity more than 10 times greater than that of graphite-based materials. However, while silicon-based compounds—high-capacity materials—offer superior capacity characteristics compared to conventionally used graphite, their volume expands rapidly during the charging process, disrupting conductive pathways and degrading battery performance; consequently, capacity drops from the outset. Furthermore, silicon-based anodes do not achieve uniform lithium ion charging along the depth of the anode during repeated charge and discharge cycles; instead, reactions proceed at the surface, accelerating surface degradation. Consequently, performance improvements are required in terms of battery cycleability. Accordingly, to resolve the aforementioned problems when using silicon-based compounds as negative electrode active materials, various measures are being discussed, such as controlling the driving potential, coating additional thin films on the active material layer, controlling the particle size of silicon-based compounds to suppress volume expansion itself, or developing binders to control the volume expansion of silicon-based compounds to prevent the interruption of conductive paths. Furthermore, research is also being conducted to complement the lifespan characteristics of silicon-based negative electrodes by limiting the proportion of silicon-based active material used during initial charging and discharging and providing a reservoir function through the method of pre-lithiation of the silicon-based active material layer. However, since the aforementioned methods can actually degrade battery performance, there are limitations to their application; consequently, there are still limitations to the commercialization of anode batteries with high silicon-based compound content. Furthermore, as the proportion of silicon-based active material in the silicon-based active material layer increases, pre-lithiation becomes concentrated on the anode surface, leading to damage to the silicon-based active material on the surface and causing problems in improving lifespan characteristics due to uneven pre-lithiation. In addition, while it is necessary to increase the content of silicon-based active materials to ensure rapid charging, increasing the charging speed to a certain level causes lithium to precipitate on the surface, leading to stability issues. Accordingly, since the direct use of silicon-based active materials results in significant volume expansion, they are used in other forms (such as SiO). Although these materials offer superior rapid charging performance compared to graphite, their use in large quantities is limited due to numerous challenges that need to be addressed, such as side reactions and volume expansion. Therefore, even when silicon-based compounds are used as active materials, it is possible to prevent electrode surface degradation during charge and discharge cycles and secure rapid charging performance; furthermore, research is needed to improve cycle performance