Segmented Silicon-Graphite Anode Layout for Cycle Stability
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Solution Overview
Problem
Lithium-ion secondary batteries with conventional negative electrodes have room for improvement in terms of cycle characteristics.
Innovation Solution
A negative electrode configuration for lithium-ion secondary batteries, comprising a negative electrode current collector, a plurality of first layers, and a second layer, where the first layers contain a silicon-based active material and a conductive material, and the second layer consists of graphite without silicon, with a specific surface arrangement and binder usage to enhance expansion distribution and stress management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional negative electrode structure is used, then the manufacturing process is simple, but the cycle characteristics are insufficient
Solution Approach 1:
The negative electrode active material layer is divided into multiple layers with different compositions and functions. The first layer contains silicon-based active material for high capacity, while the second layer contains graphite-based active material for structural stability. This segmentation allows each layer to perform its specific function, improving cycle characteristics while maintaining a manageable structural complexity.
Solution Approach 2:
The patent employs a composite electrode structure combining silicon-based materials (high capacity) with graphite-based materials (structural stability). This composite approach leverages the advantages of both material types, achieving improved cycle characteristics through the synergistic effect of different materials working together in a multi-layer configuration.
2Use of energy by moving object
If silicon-based active material is used to increase capacity, then the energy density improves, but expansion stress causes degradation
Solution Approach 1:
The electrode is segmented into functional layers: the first layer with silicon-based material provides high energy density, while the second layer with graphite-based material provides structural stability. This segmentation isolates the expansion stress of silicon to specific regions, preventing it from degrading the entire electrode structure.
Solution Approach 2:
Different regions of the electrode are assigned different material compositions tailored to their specific functions. The silicon-containing regions maximize energy density, while the graphite-containing regions provide structural reinforcement and stress distribution. This local optimization of material properties resolves the contradiction between high energy density and structural stability.
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
The proposed negative electrode configuration significantly improves the cycle characteristics of lithium-ion secondary batteries by distributing expansion stress and maintaining ion and electron conduction paths, leading to enhanced performance and durability.
Implementation Method 1
the first negative electrode active material comprises at least one of elemental silicon, a silicon alloy, and a silicon oxide... distributing expansion stress
Implementation Method 2
each of the first layers comprises a first negative electrode active material and a first conductive material... maintaining ion and electron conduction paths
Implementation Method 3
maintaining ion and electron conduction paths... lithium-ion secondary battery
Data Source
Figure 1A~1B
Figure 2A~2C
Figure 3~4
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.