Segmented Silicon-Graphite Negative Electrode for Cycle Stability
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Solution Overview
Problem
Lithium-ion secondary batteries with conventional negative electrodes have limitations in cycle characteristics, which affect their performance and longevity.
Innovation Solution
A negative electrode configuration for lithium-ion secondary batteries is introduced, featuring a current collector with multiple layers of silicon-based and graphite active materials, where the silicon-based layers are arranged in island or stripe form and a graphite layer is applied separately, using specific binders and conductive materials to manage expansion and stress during charging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based active material is used in the negative electrode, then battery capacity is improved, but expansion stress during charging deteriorates cycle characteristics
Solution Approach 1:
The negative electrode is divided into multiple layers: a first negative electrode mixture layer containing silicon-based active material and a second negative electrode mixture layer containing graphite. This segmentation allows the silicon-based material to provide high capacity while the graphite layer and binder structure manage expansion stress, improving cycle characteristics.
Solution Approach 2:
The negative electrode uses a composite structure combining silicon-based active material with graphite in separate layers. The silicon-based layer provides high capacity while the graphite layer and binder system work together to accommodate volume changes, resolving the contradiction between capacity and cycle stability.
2Ease of manufacture
If conventional negative electrode structure is used, then manufacturing is simple, but cycle characteristics are insufficient
Solution Approach 1:
The negative electrode is segmented into two distinct mixture layers applied in sequence. The first layer contains silicon-based active material with binder and conductive material, while the second layer contains graphite. This segmented structure can be manufactured using conventional coating processes, maintaining ease of manufacture while improving cycle characteristics through the functional division of layers.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration improves the cycle characteristics of lithium-ion secondary batteries by distributing expansion stress and maintaining ion and electron conduction paths, leading to enhanced capacity retention and reduced resistance.
Implementation Method 1
the first negative electrode active material comprises at least one of elemental silicon, a silicon alloy, and a silicon oxide
Implementation Method 2
each of the first layers comprises a first negative electrode active material and a first conductive material
Data Source
AI summary
Disclosed is a negative electrode capable of improving cycle characteristics of a lithium-ion secondary battery. The negative electrode has the cross-sectional configuration comprising a negative electrode current collector, a plurality of first layers, and a second layer. Each of the first layers comprises a first negative electrode active material of at least one of elemental silicon, a silicon alloy, and a silicon oxide, and a first conductive material. The second layer comprises a second negative electrode active material of graphite and does not comprise silicon. In the cross-sectional configuration, the surface of one side of the negative electrode current collector has a plurality of first regions and a second region between the first regions, the first layers are in contact with the respective first regions, and the second layer is in contact with both the second region and surfaces of one side of the first layers.