Negative Electrode Sheet Fluoride Coating Film Formation
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Solution Overview
Problem
The existing methods for producing negative electrode sheets result in breaking of active material particles during the film formation process, leading to a large amount of gas generation during initial battery charging due to shear stress, which affects the battery's performance.
Innovation Solution
A method involving a fluorination treatment to form a fluoride coating on the surface of negative electrode active material particles, followed by mixing with a binder and water to create a composite material that is then compressed into a film form, reducing particle breakage and allowing for a protective film to form, and applying an insulating coating solution before drying to create a stable negative electrode mixture layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If negative electrode composite material is compressed through a gap between rollers to form a film, then the negative electrode mixture layer is formed on the current collector foil, but shear stress causes negative electrode active material particles to break
Solution Approach 1:
The patent applies a fluorine-containing substance to the surface of negative electrode active material particles before granulation and film formation. This preliminary surface treatment creates a protective fluorinated layer that prevents particle breakage during the subsequent compression process through rollers, while still allowing the film to be formed properly.
Solution Approach 2:
The fluorine-containing substance forms a cushioning protective layer on the particle surfaces before the compression process occurs. This protective layer absorbs and distributes the shear stress during roller compression, preventing direct stress concentration on the particle cores and reducing breakage.
2Manufacturing precision
If negative electrode active material particles are broken during film formation, then the negative electrode mixture layer is formed, but a large amount of gas is generated during initial battery charging
Solution Approach 1:
The fluorine-containing substance is applied to particle surfaces before granulation and film formation, creating a protective fluorinated coating that prevents particle breakage during processing. This preliminary protection ensures particles remain intact, thereby preventing the generation of excessive gas during subsequent battery charging operations.
3Strength
If fluoride coating thickness is increased to protect particles from breakage, then particle integrity is improved, but internal resistance of the battery increases
Solution Approach 1:
The patent optimizes the concentration of the fluorine-containing substance and the application conditions to achieve a specific fluorine coating thickness range. This controlled parameter optimization provides sufficient protection against particle breakage while maintaining low internal resistance by preventing excessive coating buildup that would impede electrochemical reactions.
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 method significantly reduces the occurrence of particle breakage and gas generation during battery charging, while maintaining a low internal resistance by controlling the thickness of the fluoride coating and ensuring proper formation of the insulating layer.
Implementation Method 1
performing a fluorination treatment on the surfaces of the plurality of negative electrode active material particles to form a fluoride coating
Implementation Method 2
causing the negative electrode composite material to pass through a gap between two rollers that face each other, compressing the negative electrode composite material into a film
Implementation Method 3
forming a negative electrode mixture layer on the surface of the current collector foil by drying the film on the surface of the current collector foil
Data Source
AI summary
A method of producing a negative electrode sheet includes forming a fluoride coating on surfaces of a plurality of negative electrode active material particles by performing a fluorination treatment on the surfaces of the plurality of negative electrode active material particles; producing a negative electrode composite material containing a plurality of wet granules obtained by mixing and granulating the negative electrode active material particles with the fluoride coating on the surfaces, a binder, and water as a solvent; causing the negative electrode composite material to pass through a gap between two rollers that face each other, compressing the negative electrode composite material into a film, and attaching the film to a surface of a current collector foil; and forming a negative electrode mixture layer on the surface of the current collector foil by drying the film on the surface of the current collector foil.