Negative Electrode Layering for Void-Stable High-Density Batteries
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Solution Overview
Problem
High-density negative electrode plates for non-aqueous electrolyte secondary batteries face challenges in maintaining void distribution consistency during compression, leading to reduced cycle capacity retention due to the crush of spherical graphite particles and insufficient electron conduction paths.
Innovation Solution
A method involving the application of a first and second negative electrode slurry with specific graphite powders and cellulose-based binders, where the second layer has a higher binder fraction to act as a buffer, ensuring consistent void distribution and electron conduction, utilizing highly spherical graphite particles and smaller particles to form a stable electron path.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If spherical graphite particles are used to increase void formation, then energy density is improved, but the particles are easily crushed during compression, reducing cycle capacity retention
Solution Approach 1:
The patent uses a composite material system consisting of spherical graphite particles (first graphite powder with circularity ≥0.94) combined with irregular graphite particles (second graphite powder). This composite structure allows the spherical particles to provide high energy density and void formation, while the irregular particles act as a buffer to prevent crushing during compression, thereby maintaining cycle capacity retention rate of 80% or more after 500 cycles.
Solution Approach 2:
The patent applies different particle types in specific locations and proportions within the electrode plate. The spherical graphite particles are distributed to maximize void formation and energy density, while irregular graphite particles are incorporated as a protective phase. The binder content is also locally optimized at 0.7-3.0 mass% to provide adequate binding strength without excessive compression, creating local quality variations that resolve the contradiction between energy density and reliability.
2Quantity of substance
If high-density negative electrode plate is produced, then energy density is improved, but the distribution of voids becomes inconsistent, lowering output characteristics
Solution Approach 1:
The composite material system of spherical and irregular graphite particles creates a hierarchical structure that maintains consistent void distribution throughout the electrode plate. The irregular particles fill gaps and provide structural support, ensuring uniform void distribution even in high-density configurations, thereby maintaining both energy density and manufacturing precision.
Solution Approach 2:
The patent optimizes specific parameters including the circularity of first graphite powder (≥0.94), the D50 ratio of second to first graphite powder (0.06-0.40), and binder content (0.7-3.0 mass%). These parameter changes enable the production of high-density electrode plates with consistent void distribution, resolving the contradiction between energy density and manufacturing precision.
3Quantity of substance
If spherical graphite particles are compressed to increase density, then energy density is improved, but electron conduction paths are disrupted, reducing cycle capacity
Solution Approach 1:
The composite material system ensures continuous electron conduction paths by combining spherical graphite particles with irregular graphite particles and conductive binder. The irregular particles and binder network provide alternative conduction pathways that remain intact during compression, maintaining electron conductivity even as density increases to improve energy density.
Solution Approach 2:
The patent optimizes the binder content (0.7-3.0 mass%) and particle size distribution (D50 ratio of 0.06-0.40) to ensure adequate electron conduction. These parameter changes create a robust conductive network that maintains electron flow during compression, resolving the contradiction between energy density improvement and electron conduction reliability.
Data Source
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AI summary
(A) A first layer is formed by applying a first negative electrode slurry to the surface of a negative electrode substrate (22). (B) A second layer is formed by applying a second negative electrode slurry to the surface of the first layer. The first negative electrode slurry includes a first negative electrode composite material. The second negative electrode slurry includes a second negative electrode composite material. Each of the first negative electrode composite material and the second negative electrode composite material includes a negative electrode active material and a cellulose-based binder. The negative electrode active material includes a first graphite powder and a second graphite powder. The first negative electrode composite material includes the cellulose-based binder at a first mass fraction. The second negative electrode composite material includes the cellulose-based binder at a second mass fraction.