Dual-Composition Graphite Anode for Uniform Lithium Deposition
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Solution Overview
Problem
Lithium precipitation imbalance occurs on the negative electrode of secondary batteries due to differences in loading amounts caused by the sliding phenomenon during the manufacturing process, leading to rapid deterioration of battery performance and swelling.
Innovation Solution
A negative electrode with a first and second negative electrode active material layer, where the first layer consists of uncoated graphite and the second layer consists of carbon-coated graphite, is designed to address the lithium precipitation imbalance by forming inclined and flat portions on the electrode surface, ensuring uniform lithium deposition rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a single-layer negative electrode structure is used, then the electrode structure is simple and easy to manufacture, but the battery capacity is insufficient and lithium deposition occurs during fast charging
Solution Approach 1:
The negative electrode is divided into two distinct layers: a first negative electrode layer containing soft carbon material and a second negative electrode layer containing hard carbon material. This segmentation allows each layer to perform specialized functions - the soft carbon layer accommodates volume expansion during lithiation while the hard carbon layer provides structural stability and prevents lithium deposition, thereby increasing battery capacity and enabling fast charging without the complexity of a single-layer structure.
Solution Approach 2:
Different regions of the negative electrode are assigned different material properties - the soft carbon material in the first layer provides high lithium insertion capacity and flexibility to accommodate volume changes, while the hard carbon material in the second layer provides structural rigidity and prevents lithium dendrite formation. This local differentiation of material qualities optimizes performance for both high capacity and fast charging while maintaining a relatively simple two-layer structure.
2Productivity
If soft carbon material is used to increase lithium insertion capacity, then battery capacity improves, but volume expansion causes electrode degradation
Solution Approach 1:
The negative electrode is segmented into two functional layers: the first layer uses soft carbon material optimized for high lithium insertion capacity and volume expansion accommodation, while the second layer uses hard carbon material optimized for structural stability and dimensional maintenance. This segmentation allows each material to excel at its specialized function without compromising the other, resolving the contradiction between capacity and structural integrity.
Solution Approach 2:
The negative electrode employs a composite structure combining soft carbon material and hard carbon material in distinct layers. The soft carbon component (such as lithiated polymer or amorphous carbon) provides high lithium insertion capacity and flexibility for volume changes, while the hard carbon component (such as graphitized carbon or ordered carbon) provides structural rigidity and prevents electrode degradation, creating a synergistic composite that achieves both high capacity and structural stability.
3Strength
If hard carbon material is used to maintain structural stability, then electrode strength improves, but lithium insertion capacity is limited
Solution Approach 1:
The negative electrode is divided into two layers where the first layer uses soft carbon material specifically selected for high lithium insertion capacity, while the second layer uses hard carbon material specifically selected for structural stability. This segmentation allows the soft carbon layer to maximize lithium uptake without being constrained by structural requirements, while the hard carbon layer provides the necessary structural framework, thereby overcoming the capacity limitation of hard carbon when used alone.
4Speed
If fast charging is implemented, then charging speed increases, but lithium deposition occurs on the electrode surface
Solution Approach 1:
The second layer of the negative electrode is specifically designed with hard carbon material that has distinct local properties - higher structural order and surface characteristics - that are optimized for fast lithium insertion and prevention of lithium deposition. This local quality differentiation at the electrode surface enables fast charging rates while maintaining reliability by preventing dendrite formation and lithium plating, which would otherwise occur during rapid charging.
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 solution improves the rapid charging characteristics and prevents battery performance deterioration by uniformly distributing lithium deposition across the electrode surface, enhancing the battery's capacity and life characteristics.
Implementation Method 1
capacity retention rate after five hundred lithiation-delithiation cycles
Implementation Method 2
capacity retention rate after five hundred lithiation-delithiation cycles
Implementation Method 3
volume expansion of the negative electrode during charging
Data Source
Figure 1~2
Figure 3
AI summary
The present disclosure relates to a negative electrode for secondary battery in which a negative electrode active material layer is formed on at least one surface of a negative electrode current collector, wherein the negative electrode active material layer includes a first negative electrode active material layer, and a second negative electrode active material layer formed on one side or both sides of the first negative electrode active material layer in a planar, and wherein the first negative electrode active material layer includes uncoated graphite as a first negative electrode active material, and the second negative electrode active material layer includes carbon-coated graphite as a second negative electrode active material, and to an electrode assembly and a secondary battery including same.