Natural Graphite Anode Coating for Fast-Charge Expansion Control
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Solution Overview
Problem
Existing secondary batteries using natural graphite face challenges in controlling volume expansion and electrolyte side reactions, which deteriorate battery performance and lifespan.
Innovation Solution
A negative electrode with natural graphite and a carbon coating layer, optimized for particle size distribution (D50 of 6 µm to 9.2 µm, half-width of 5.0 µm to 5.5 µm, and specific surface area of 0.6 m²/g to 2.2 m²/g, to mitigate stress and control volume expansion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If natural graphite is used as negative electrode active material, then battery capacity is improved, but volume expansion occurs during charging and discharging
Solution Approach 1:
The patent uses composite materials by coating natural graphite particles with a specific carbon coating layer. This composite structure allows the natural graphite to maintain its high capacity while the carbon coating layer constrains the volume expansion, resolving the contradiction between capacity and volume stability.
Solution Approach 2:
The patent changes physical parameters of the natural graphite particles, specifically controlling particle size (D50 of 6-9.2 μm) and half-width (5.0-5.5 μm), to optimize the balance between capacity and volume expansion control. These parameter adjustments help mitigate stress inside the particles during charging/discharging cycles.
2Volume of moving object
If carbon coating layer is disposed on natural graphite, then volume expansion is partially controlled, but electrolyte side reactions are not sufficiently controlled
Solution Approach 1:
The patent optimizes the carbon coating layer thickness to 0.5-5 nm, which is sufficient to control volume expansion while being thin enough to minimize electrolyte side reactions. This precise parameter control resolves the contradiction between volume control and side reaction prevention.
Solution Approach 2:
The patent applies local quality by creating a thin carbon coating layer only on the surface of natural graphite particles. This localized treatment provides volume control where needed while maintaining the bulk properties of natural graphite for high capacity, and the thinness reduces electrolyte side reactions.
3Stress or pressure
If particle size is reduced to control volume expansion, then stress inside particles is reduced, but specific surface area increases leading to more electrolyte side reactions
Solution Approach 1:
The patent optimizes particle size parameters (D50: 6-9.2 μm, half-width: 5.0-5.5 μm) to achieve the right balance. This specific size range reduces internal stress during charging/discharging while limiting the specific surface area to minimize electrolyte side reactions, resolving the contradiction between stress reduction and side reaction control.
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
Improves rapid charging performance and extends battery lifespan by reducing internal stress and electrolyte side reactions.
Implementation Method 1
the stress inside the natural graphite may be mitigated
Implementation Method 2
the degree of volume expansion of natural graphite in the negative electrode active material particles may be reduced
Implementation Method 3
a current may be evenly transmitted into a negative electrode
Implementation Method 4
a region in which electrolyte side reaction occurs is not sufficiently controlled
Data Source
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AI summary
The present invention relates to a negative electrode and a secondary battery including the same, the negative electrode including a current collector and a negative electrode active material layer, wherein the negative electrode active material layer includes negative electrode active material particles, the negative electrode active material particles include natural graphite and a carbon coating layer disposed on the natural graphite, on a particle size distribution, the negative electrode active material particles have a D50 of 6 µm to 9.2 µm and a half-width of 5.0 µm to 5.5 µm, and the specific surface area of the negative electrode active material particles is 0.6 m2/g to 2.2 m2/g.