Negative Electrode Layer Structure for Stable SEI and Li-Ion Kinetics
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Solution Overview
Problem
Conventional secondary battery negative electrode plates have limited energy density, poor cycling performance, and low capacity retention due to inadequate selection of active materials, leading to reduced charging and discharging efficiency.
Innovation Solution
A negative electrode plate with a surface layer and substrate layer having specific ID/IG values, controlled within certain ranges, to form a dense and stable SEI film, enhancing lithium ion insertion/extraction efficiency and maintaining balanced kinetic performance, along with a primer layer for improved adhesion and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional negative electrode active materials are used, then the negative electrode plate can be manufactured with standard materials, but the cycling capacity retention rate and first Coulombic efficiency are insufficient
Solution Approach 1:
The negative electrode active material layer is divided into a surface layer and a substrate layer with different ID/IG value ranges. The surface layer has lower ID/IG values (0.55-0.78) to form stable SEI films, while the substrate layer has higher ID/IG values (0.78-0.96) to provide capacity. This segmentation allows each layer to perform its specific function optimally, resolving the contradiction between cycling performance and material selection flexibility.
Solution Approach 2:
Different regions of the negative electrode active material layer are assigned different properties through controlling ID/IG values. The surface layer is optimized for SEI film formation with lower ID/IG values, while the substrate layer is optimized for lithium ion storage with higher ID/IG values. This local quality differentiation improves cycling capacity retention rate while maintaining manufacturing feasibility.
2Productivity
If the negative electrode active material layer has high surface defect degree, then lithium ion insertion/extraction efficiency improves, but SEI film stability deteriorates
Solution Approach 1:
The negative electrode active material layer is segmented into surface and substrate layers with different ID/IG value ranges. The surface layer (ID/IG: 0.55-0.78) provides stability for SEI film formation, while the substrate layer (ID/IG: 0.78-0.96) provides high lithium ion insertion/extraction efficiency. This segmentation resolves the contradiction between SEI film stability and lithium ion efficiency.
Solution Approach 2:
The ID/IG ratio parameter is used to control the surface defect degree of the negative electrode active material layer. By optimizing this parameter within specific ranges for different layers, the patent achieves both stable SEI film formation and high lithium ion insertion/extraction efficiency, resolving the contradiction between these two opposing requirements.
3Device complexity
If a single-layer negative electrode active material layer is used, then the structure is simple, but the kinetic performance is unbalanced
Solution Approach 1:
The negative electrode active material layer is segmented into surface and substrate layers with different ID/IG value ranges. This segmentation enables balanced kinetic performance by optimizing both SEI film formation (surface layer) and lithium ion storage (substrate layer), while maintaining relatively simple overall structure.
Solution Approach 2:
The patent uses composite material structure with surface layer and substrate layer having different ID/IG characteristics. This composite approach achieves balanced kinetic performance by combining materials with different properties in a coordinated manner, resolving the contradiction between structural simplicity and performance balance.
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 cycling capacity retention rate and first Coulombic efficiency of secondary batteries, maintaining balanced kinetic performance and energy density by controlling surface defects and electrolyte infiltration.
Implementation Method 1
a surface defect degree of the negative electrode active material layer can be controlled, which is conducive to formation of a dense and stable SEI film on a surface of the negative electrode active material layer
Implementation Method 2
the negative electrode active material layer has a improved efficiency of insertion/extraction of lithium ions
Data Source
AI summary
A negative electrode plate includes: a negative electrode current collector; and a negative electrode active material layer that contains negative electrode active substance particles and that is disposed on at least one side of the negative electrode current collector. The negative electrode active material layer includes: a surface layer with an ID1/IG1 value of A, where 0.55≤A≤0.78; and a substrate layer with an ID2/IG2 value of B located between the negative electrode current collector and the surface layer, where 0.78≤B≤0.96. The negative electrode active material layer satisfies: 0.60≤A/B≤1.0.