Negative Electrode Layering for Lithium Battery Adhesion

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Solution Overview

Problem

Lithium secondary batteries face challenges in achieving high capacity, adhesion, and life characteristics due to the weak affinity of silicon oxide with binders and volume expansion, which deteriorates electrode adhesion and life characteristics, especially in high-loading electrodes.

Innovation Solution

A negative electrode comprising a first mixture layer with natural graphite and silicon oxide, and a second mixture layer with artificial graphite, both with specific polymer binders and conductive materials, to enhance adhesion and output characteristics, with a layered structure optimizing thickness and material ratios.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If the amount of negative electrode active material is increased to achieve high capacity, then the energy density is improved, but the electrode thickness increases causing irregular binder distribution and deteriorated adhesion

Engineering Contradiction:

Improveamount of negative electrode active materialVSAvoidadhesion

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The negative electrode is divided into two distinct mixture layers: a first layer containing natural graphite and silicon oxide, and a second layer containing artificial graphite. This segmentation allows each layer to have optimized properties - the first layer provides high capacity while the second layer ensures good adhesion and binder distribution, resolving the contradiction between high active material content and maintained adhesion.

Inventive Principle:

Principle #1Segmentation

2Quantity of substance

If silicon oxide is used as negative electrode active material to achieve high capacity, then the energy density is improved, but the weak affinity with binder deteriorates adhesion and life characteristics

Engineering Contradiction:

Improvesilicon oxide contentVSAvoidadhesion and life characteristics

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

Silicon oxide is localized in the first negative electrode mixture layer where it can provide high capacity, while natural graphite is also present in this layer to compensate for the weak binder affinity. The second layer uses artificial graphite which has good adhesion properties. This local quality distribution allows silicon oxide to contribute to high capacity while the overall electrode structure maintains good adhesion and life characteristics.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The first negative electrode mixture layer uses a composite of natural graphite and silicon oxide, combining the high capacity of silicon oxide with the good adhesion properties of natural graphite. This composite approach allows the electrode to achieve high capacity while maintaining reliable adhesion to the current collector.

Inventive Principle:

Principle #40Composite materials

3Quantity of substance

If silicon oxide is used as negative electrode active material, then the capacity is improved, but the volume expansion degrades life characteristic

Engineering Contradiction:

Improvesilicon oxide contentVSAvoidlife characteristic

Core Design Contradiction:

Quantity of substanceVSDuration of action of stationary object

Solution Approach 1:

The patent changes the structural parameter of the electrode by creating a two-layer configuration. The first layer contains silicon oxide for high capacity, while the second layer with artificial graphite provides structural stability. This parameter change in electrode structure mitigates the detrimental effects of silicon oxide volume expansion on life characteristics.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS10454096B2Negative electrode for lithium secondary battery and lithium secondary battery comprising the same

Publication Date: 2019.10.22 LG ENERGY SOLUTION LTD

AI summary

Disclosed is a negative electrode for a lithium secondary battery having excellent electric conductivity and adhesion even though a high-loading negative electrode is used, and the negative electrode includes a negative electrode current collector; a first negative electrode mixture layer containing a first negative electrode active material, a first polymer binder and a first conductive material and formed on at least one surface of the negative electrode current collector; and a second negative electrode mixture layer containing a second negative electrode active material, a second polymer binder and a second conductive material and formed on an upper surface of the first negative electrode mixture layer, wherein the first negative electrode active material contains natural graphite and silicon oxide, and the second negative electrode active material contains artificial graphite.