Silicon-Graphite Negative Electrode Coating for Lower Battery Expansion
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Solution Overview
Problem
Conventional lithium-ion batteries with graphite negative electrodes face challenges in meeting fast charging requirements due to high expansion rates caused by lithium intercalation, which silicon-based negative electrode materials also experience despite efforts to reduce volume change.
Innovation Solution
A negative electrode plate is designed with a coating layer comprising a mixture of carbon and amorphous silicon, where the median particle size of graphite is smaller than that of silicon, enhancing lithium intercalation potential and reducing volume expansion by creating a gap that mitigates the influence of silicon expansion on the electrode thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon negative electrode materials are used to increase theoretical capacity, then electric capacity is improved, but volume expansion occurs during lithium intercalation
Solution Approach 1:
The patent embeds silicon-containing material particles inside graphite material particles, creating a core-shell structure where silicon is nested within graphite. This nesting approach allows silicon to provide high capacity while graphite constrains its volume expansion, resolving the contradiction between capacity improvement and volume stability.
Solution Approach 2:
The patent controls the particle size parameters of both silicon-containing material and graphite material, with graphite particle size being larger than silicon particle size. This parameter optimization ensures that silicon is properly embedded within graphite while maintaining appropriate spacing to accommodate expansion without excessive volume increase.
2Volume of moving object
If graphite material with small particle size is used, then gaps between substances are enlarged to reduce expansion influence, but manufacturing precision requirements increase
Solution Approach 1:
The patent specifies precise particle size parameters: silicon-containing material Dv50 is 5-15 μm while graphite material Dv50 is 10-20 μm. These controlled parameters ensure optimal gap formation for expansion accommodation while maintaining manufacturability through clear specification ranges rather than single values.
3Productivity
If silicon-containing material is mixed with graphite material, then lithium intercalation capability is improved, but device complexity increases
Solution Approach 1:
The patent creates a composite coating layer combining silicon-containing material and graphite material in specific proportions (silicon 5-30 wt%, graphite 70-95 wt%). This composite structure leverages the high capacity of silicon and the stability of graphite, improving lithium intercalation capability while maintaining a manageable single-layer coating structure.
Solution Approach 2:
The patent employs a nested structure where silicon-containing material particles are embedded within graphite material particles. This nesting approach simplifies the overall coating structure to a single layer while internally organizing materials to maximize lithium intercalation capability through the synergistic combination of both materials.
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
This design improves lithium intercalation capability and electric capacity while reducing the expansion rate of the battery, enabling better fast charging performance and cycle life.
Implementation Method 1
a lithium intercalation potential of the silicon-containing material is higher than a lithium intercalation potential of the graphite material, so that the silicon-containing material is prior to the graphite material for lithium intercalation
Implementation Method 2
The silicon negative electrode materials are prone to expansion caused by lithium intercalation during a charge-discharge cycle, expansion of silicon caused by lithium intercalation usually occurs inside a crystal lattice
Data Source
AI summary
Disclosed are a negative electrode plate and a battery. The negative electrode plate includes a current collector and a coating layer disposed on at least one side surface of the current collector. The coating layer includes a silicon-containing material and a graphite material, and a median particle size Dv50 of the graphite material is smaller than a median particle size Dv50 of the silicon-containing material; and the silicon-containing material is a mixture of carbon and amorphous silicon, and a ray diffraction pattern of the silicon-containing material does not have an obvious diffraction peak of silicon, thereby improving an electric capacity of the negative electrode plate, decreasing the influence of volume expansion on a thickness of the electrode plate caused by lithium intercalation of the silicon-containing material, and reducing an expansion rate of the battery.