Composite Separator for Secondary Battery Thermal Safety
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Solution Overview
Problem
Conventional separators for lithium secondary batteries face challenges with high thermal shrinkage, puncture strength, and electrical safety, particularly when used in stack-type batteries with increased capacity and area, leading to potential overheating and fire risks.
Innovation Solution
A porous composite separator with a thermal resistant coating layer formed by applying two or more kinds of inorganic particles on a porous substrate using dual slot die coating and multi-stage drying, where the particles are separated into layers based on specific gravity, size, and shape differences, enhancing mechanical strength and gas permeability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the separator is thinned to achieve higher capacity, then the capacity and output are improved, but the mechanical properties such as puncture strength and tensile strength are deteriorated
Solution Approach 1:
The patent applies composite materials by forming a coating layer containing inorganic particles (such as alumina, boehmite) and binder polymers on the porous substrate. This composite structure enhances the mechanical strength and thermal stability of the thin separator, allowing it to maintain high capacity while improving puncture strength and tensile strength.
Solution Approach 2:
The patent utilizes porous materials by employing a porous substrate with controlled pore structure and forming a porous coating layer. The porous structure maintains high ion permeability for capacity while the coating layer provides mechanical reinforcement to prevent puncture and deformation.
2Ease of manufacture
If conventional separators are used in stack type secondary batteries, then the production process is simple, but alignment defects occur and thermal shrinkage and puncture strength are significantly low
Solution Approach 1:
The patent applies parameter changes by modifying the physical and chemical parameters of the separator, including forming a coating layer with specific inorganic particles and binder polymers, controlling pore size and distribution, and optimizing thickness parameters. These parameter changes improve thermal shrinkage resistance and puncture strength while maintaining manufacturability.
3Quantity of substance
If the separator is thinned for higher capacity, then the capacity increases, but thermal safety is lowered due to damage or deformation at elevated temperatures
Solution Approach 1:
The patent addresses thermal expansion by selecting inorganic particles with low thermal expansion coefficients (such as alumina and boehmite) for the coating layer. These particles maintain dimensional stability at elevated temperatures, preventing separator deformation and maintaining thermal safety while allowing the separator to remain thin for high capacity.
Solution Approach 2:
The patent uses composite materials combining inorganic particles with high thermal stability and binder polymers to form a coating layer that resists thermal degradation. This composite structure prevents separator damage at elevated temperatures, ensuring thermal safety while maintaining the thin design for high capacity.
4Reliability
If existing coated separators are used, then some safety improvement is achieved, but poor penetration properties, poor appearance due to electrolyte reaction, and deterioration of life characteristics occur
Solution Approach 1:
The patent optimizes parameters including the type and ratio of inorganic particles, binder polymer selection, coating thickness, and pore structure. These parameter optimizations ensure chemical stability with the electrolyte, preventing appearance degradation and maintaining life characteristics while preserving safety improvements.
Solution Approach 2:
The patent employs specifically designed composite materials where inorganic particles provide structural stability and chemical inertness, while binder polymers provide adhesion and flexibility. This composite formulation prevents electrolyte-induced degradation and maintains battery life while ensuring safety.
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 thermal safety, puncture strength, and electrolyte impregnation, resulting in a battery with enhanced capacity retention and reduced risk of internal short circuits, while simplifying the production process.
Implementation Method 1
the particles are separated into layers based on specific gravity, size, and shape differences
Implementation Method 2
the particles are separated into layers based on specific gravity, size, and shape differences
Implementation Method 3
pores inside the film are impregnated with an electrolyte to provide a migration channel of lithium ions
Implementation Method 4
the separator is a subsidiary material which prevents an internal short circuit of a positive electrode and a negative electrode
Data Source
AI summary
Provided are a composite separator for a secondary battery, a method for producing the same, and a lithium secondary battery including the same. Specifically, a composite separator for a secondary battery showing excellent physical properties such as thermal safety and electrochemical safety and also allowing simplification of a separator production process, a method for producing the same, and a lithium secondary battery including the same are provided.