Amorphous Carbon-Coated Graphite for Battery Electrode Coating
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Solution Overview
Problem
The manufacturing of lithium-ion secondary batteries faces challenges in reducing the time and energy required for the drying process of the negative electrode active material layer, while maintaining low resistance and preventing dilatancy, which can cause clogging issues during the coating process.
Innovation Solution
The use of negative electrode active material particles with graphite particles partially covered by an amorphous carbon film, having a specific weight ratio of amorphous carbon and a linseed oil absorption number within certain ranges, helps in achieving a high solid content concentration without dilatancy, thereby reducing manufacturing costs and maintaining low resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the proportion of solvent is increased in the paste-like mixture to improve coating processability, then the coating can be applied smoothly, but the drying time and energy consumption increase significantly
Solution Approach 1:
The patent changes the particle size parameter of graphite particles to a specific range (0.3 μm to 3 μm) and controls the amorphous carbon coating amount (0.1 mass% to 15.0 mass%), which modifies the paste rheology and allows for reduced solvent content while maintaining coating processability, thereby reducing drying time
2Loss of time
If the concentration of solid content in the mixture is increased to reduce solvent proportion and drying time, then drying time and energy consumption are reduced, but dilatancy occurs causing clogging during coating
Solution Approach 1:
The patent uses a composite structure of graphite particles coated with amorphous carbon, where the amorphous carbon layer (0.1 mass% to 15.0 mass%) acts as a lubricant and prevents particle aggregation, eliminating dilatancy even at high solid content concentrations (50 mass% or more), thus preventing clogging while maintaining short drying times
Solution Approach 2:
By controlling the particle size (0.3 μm to 3 μm) and amorphous carbon coating amount, the patent optimizes the paste flow characteristics to prevent dilatancy, enabling high solid content concentration without clogging during coating
3Reliability
If graphite particles with high oil absorption number are used to reduce battery resistance, then lithium ion transfer is improved and resistance decreases, but the paste becomes difficult to handle and dilatancy increases
Solution Approach 1:
The patent creates a composite where graphite particles are coated with amorphous carbon in a controlled amount (0.1 mass% to 15.0 mass%). This composite structure maintains the high oil absorption number of graphite (reducing battery resistance) while the amorphous carbon layer prevents excessive paste thickening and dilatancy, improving handleability
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 configuration allows for a lithium-ion secondary battery with low resistance and resistance increase rate, while preventing dilatancy and clogging, thus optimizing the manufacturing process and battery performance.
Implementation Method 1
the negative electrode active material particles have a linseed oil absorption number Y (mL/100 g) of 35 (mL/100 g)≤Y≤70 (mL/100 g)... This can inhibit dilataney from occurring in the negative electrode mixture
Implementation Method 2
the prepared mixture is coated onto a current collector, then dried, and press-rolled
Data Source
AI summary
A Lithium-ion secondary battery (100A) has a negative electrode current collector (241A) and a negative electrode active material layer (243A) coated on the negative electrode current collector (241A). The negative electrode active material layer (243A) contains negative electrode active material particles (710A). The negative electrode active material particles (710A) include graphite particles each at least partially covered by an amorphous carbon film (750). The weight ratio X of the amorphous carbon film (750) in the negative electrode active material particles (710A) is 0.02≤X≤0.06. The negative electrode active material particles (710A) have a linseed oil absorption number Y (mL/100 g) of 35 (mL/100 g)≤Y≤70 (mL/100 g).