Aqueous Slurry Coated Battery Separator Preventing Pore Closure
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Solution Overview
Problem
Current separators for lithium secondary batteries face challenges in achieving high thermal stability and electrochemical stability, leading to safety concerns and reduced battery capacity due to the use of organic solvents, which cause pore closure and environmental issues.
Innovation Solution
A separator with a coating layer composed of inorganic particles and a binder copolymer, including acrylamide, vinyl cyanide, and acrylic monomers, applied via an aqueous slurry and heat-dried to prevent pore closure, ensuring smooth lithium ion movement and improved thermal stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a thermal resistant resin coating layer is formed using an organic solvent, then thermal resistance is improved, but transmittance is lowered due to pore closure and environmental problems occur
Solution Approach 1:
The patent changes the solvent parameter from organic to aqueous, which fundamentally alters the interaction with the microporous membrane. The aqueous solvent does not penetrate and close the pores like organic solvents do, while still allowing the thermal resistant resin to form a coating layer that provides thermal resistance without compromising transmittance
Solution Approach 2:
The patent introduces a binder as an intermediary substance that facilitates the formation of the thermal resistant resin coating layer. The binder holds the resin particles together and adheres them to the microporous membrane surface, enabling effective thermal resistance without requiring organic solvents that would close the pores
2Temperature
If organic solvent is used to form coating layer, then thermal resistant resin coating is achieved, but basic functions of microporous membrane are hindered
Solution Approach 1:
By changing the solvent parameter from organic to aqueous, the patent preserves the microporous membrane's basic functions including shutdown capability. The aqueous solvent evaporates without penetrating deep into the pores, allowing the membrane's inherent safety mechanisms to remain functional while still providing thermal resistance through the coating layer
3Stability of the object's composition
If inorganic material is mixed in binder solution to improve thermal shrinkage, then thermal stability is improved, but manufacturing complexity increases due to multiple coating steps
Solution Approach 1:
The patent merges the thermal resistant resin and inorganic material into a single coating composition applied in one step. This combination approach provides both thermal resistance and thermal shrinkage prevention simultaneously, eliminating the need for separate coating steps and reducing manufacturing complexity while maintaining excellent thermal stability
Solution Approach 2:
The patent uses a composite coating layer consisting of thermal resistant resin particles and inorganic material particles bound together. This composite structure leverages the complementary properties of both materials - the resin provides thermal resistance while the inorganic material prevents thermal shrinkage - achieving superior thermal stability without complex multi-step manufacturing
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 provides a separator with a low thermal shrinkage ratio, high melt fracture temperature, and enhanced battery stability, preventing rapid lifespan decrease and ensuring electrical characteristics like capacity retention, while being environmentally friendly.
Implementation Method 1
applying an aqueous slurry including inorganic particles, a binder, and water on a porous substrate; and forming a coating layer by heat drying after applying the aqueous slurry
Implementation Method 2
a binder for binding the plurality of inorganic particles
Data Source
AI summary
Provided is a separator for a secondary battery including: a porous substrate; and a coating layer formed on the porous substrate, wherein the coating layer includes a plurality of inorganic particles and a binder for binding the plurality of inorganic particles, and the binder includes a copolymer of a monomer mixture including an acrylamide-based monomer, a vinyl cyanide monomer, and an acrylic monomer having a carboxyl group.