Battery Separator Slurry Dispersion for Low-Aggregation Inorganic Coatings
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Solution Overview
Problem
Existing methods for manufacturing separators for lithium secondary batteries face challenges in dispersing inorganic particles homogeneously, leading to issues such as increased resistance and decreased air permeability, which can result in short-circuits and explosions during high-temperature conditions.
Innovation Solution
A method involving a combination of contact and non-contact type dispersion processes is used to prepare a slurry for forming an inorganic composite porous layer. This method includes using beads with an average particle diameter at least 200 times larger than the inorganic particles in the contact type dispersion instrument, followed by high-pressure homogenization to achieve uniform dispersion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional milling step is used to disperse inorganic particles, then mixing and dispersing is performed, but inorganic particles are aggregated and dispersibility is insufficient
Solution Approach 1:
The patent replaces the conventional mechanical milling system with an ultrasonic wave-based dispersion system. The ultrasonic waves generate cavitation bubbles that collapse and create intense local shear forces, effectively dispersing inorganic particles without the aggregation problems associated with mechanical milling. This substitution of mechanical action with acoustic field action resolves the contradiction between ease of manufacture and manufacturing precision.
Solution Approach 2:
The patent utilizes the phase transition phenomenon of cavitation bubbles (formation and collapse) generated by ultrasonic waves. These bubbles undergo rapid formation and collapse cycles, creating micro-shocks and shear forces that disperse inorganic particles effectively. This phase transition mechanism enables superior dispersibility compared to conventional mechanical methods while maintaining process simplicity.
2Quantity of substance
If inorganic particles are aggregated in slurry, then composite particles are generated, but air permeability decreases and resistance value increases
Solution Approach 1:
The patent replaces mechanical mixing that causes aggregation with ultrasonic wave-based dispersion. The ultrasonic cavitation creates intense local shear forces that prevent particle aggregation, ensuring uniform distribution of inorganic particles in the slurry. This results in maintained air permeability and appropriate resistance values by preventing the formation of aggregated composite particles.
3Reliability
If polymer porous support is used as separator substrate, then short-circuit prevention is achieved, but heat resistance is low and shrinking occurs at high temperature
Solution Approach 1:
The patent creates a composite structure by coating inorganic particles onto the polymer porous support. This composite separator combines the short-circuit prevention capability of the polymer substrate with the high heat resistance of inorganic particles. The inorganic coating layer prevents shrinking and melting at high temperatures while the underlying polymer structure maintains the porosity needed for ion transport and short-circuit prevention.
Solution Approach 2:
The patent utilizes the porous structure of both the polymer substrate and the inorganic particle coating. The porous structure allows efficient ion transport between electrodes while the inorganic particles provide thermal stability. The combination maintains porosity for electrical isolation function while adding heat resistance through the inorganic component.
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
The proposed method effectively disperses inorganic particles homogeneously, reducing the generation of secondary particles and improving the physical properties of the separator, such as reduced surface protrusions and enhanced mechanical stability, thereby preventing internal short-circuits and ensuring safer battery operation.
Implementation Method 1
the contact type dispersion instrument includes beads having an average particle diameter at least 200 times larger than the average particle diameter (D50) of the inorganic particles
Implementation Method 2
carrying out dispersion of the inorganic particles in the slurry, wherein the dispersion is carried out by using two types of dispersion instruments of a contact type dispersion instrument and a non-contact type dispersion instrument
Implementation Method 3
followed by high-pressure homogenization to achieve uniform dispersion
Implementation Method 4
non-contact type dispersion instrument
Data Source
AI summary
A method for manufacturing a separator disperses inorganic particles homogeneously in a slurry. The separator obtained by this method causes low aggregation of the inorganic particles to show reduced defects of surface protrusions in its appearance and can provide excellent physical properties. This method for manufacturing a separator includes preparing a slurry containing inorganic particles, a binder polymer and a solvent. The method additionally includes; carrying out dispersion of the inorganic particles in the slurry, and the dispersion is carried out by using two types of dispersion instruments of a contact type dispersion instrument and a non-contact type dispersion instrument. The contact type dispersion instrument includes beads having an average particle diameter at least 200 times larger than the average particle diameter (D50) of the inorganic particles. The method additionally includes applying the slurry to at least one surface of a polymer porous support, followed by drying.