Battery Separator Coating for Faster Electrolyte Wetting
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Solution Overview
Problem
Existing separators for secondary batteries do not effectively improve electrolyte impregnation while minimizing the addition of surfactants, which is crucial for battery lifespan and capacity.
Innovation Solution
A separator with a coating layer comprising an acrylate-based binder and a small amount of fluorine-based nonionic surfactant, where the binder constitutes 10 wt% or less and the surfactant 0.001 wt% or less of the total inorganic material and binder, with a coating layer density of 2 g/m³ or less, enhancing electrolyte impregnation and retention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a coating layer with inorganic material and binder is formed on polyolefin substrate to improve safety, then high temperature resistance is improved, but electrolyte impregnation rate deteriorates
Solution Approach 1:
The coating layer is designed with a porous structure having specific porosity (30-70%) and pore size (0.01-10 μm) to facilitate electrolyte penetration. The porous structure allows the electrolyte to efficiently wet and impregnate the coating layer while maintaining the safety functions, thus resolving the contradiction between improved temperature resistance and reduced electrolyte impregnation rate.
Solution Approach 2:
The invention optimizes specific parameters of the coating layer including porosity (30-70%), pore size (0.01-10 μm), and binder content (1-10 wt%) to achieve balanced performance. By carefully controlling these parameters, the coating layer provides both high temperature resistance and adequate electrolyte impregnation, resolving the technical contradiction.
2Reliability
If surfactant is added to coating layer to improve electrolyte impregnation, then electrolyte impregnation rate is improved, but internal resistance increases
Solution Approach 1:
The invention precisely controls the surfactant concentration within a narrow range (0.001-0.01 wt%) to achieve adequate electrolyte impregnation while minimizing the increase in internal resistance. This optimized parameter approach allows the system to benefit from improved wetting without suffering from excessive energy loss.
Solution Approach 2:
The surfactant acts as an intermediary substance that facilitates electrolyte penetration into the porous coating structure. By using a minimal amount of surfactant as a mediator, the invention achieves improved electrolyte impregnation while keeping the negative impact on internal resistance to a minimum.
3Strength
If binder content in coating layer is increased to improve adhesion, then adhesion strength is improved, but electrolyte impregnation rate deteriorates
Solution Approach 1:
The invention optimizes the binder content within a specific range (1-10 wt%) to achieve the right balance between adhesion strength and electrolyte impregnation. This controlled parameter approach ensures that the coating layer maintains adequate bonding to the substrate while preserving sufficient porosity for electrolyte penetration.
Solution Approach 2:
The coating layer is designed with non-uniform local properties where the binder is distributed to provide adequate adhesion at the substrate interface while maintaining higher porosity in the bulk structure for electrolyte impregnation. This local differentiation of properties resolves the contradiction between adhesion and wetting.
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 solution significantly improves electrolyte impregnation and retention, maintaining an 80% capacity retention rate after 150 charge-discharge cycles, and ensures symmetrical electrolyte diffusion, preventing asymmetry and reducing internal resistance.
Implementation Method 1
the additive may be a fluorine-based nonionic surfactant
Implementation Method 2
improves wettability of a separator substrate by suppressing the generation of bubbles in a slurry
Implementation Method 3
The coating layer has a porous structure by the inorganic material and the binder. A volume in which a liquid electrolyte solution is placed is increased by virtue of the porous structure
Data Source
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AI summary
The present invention is a separator for a secondary battery having a coating layer formed on a separator substrate, wherein the coating layer is formed on at least one surface of the separator substrate, the coating layer comprises an acrylate-based binder and an additive, and the additive is a fluorine-based non-ionic surfactant, and provides a separator for a secondary battery with significantly improved electrolyte impregnation rate.