Battery Separator Composite Layer Thickness Ratio
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing separators for non-aqueous electrolyte secondary batteries face challenges in achieving a balance between reduced thickness, maintaining lithium ion permeability, and ensuring safety and output performance, with previous proposals lacking clear correlations among these factors.
Innovation Solution
A separator comprising a first porous layer with a shutdown function and a second layer made of aramid resin and inorganic material, with a specific thickness ratio and composition to optimize durability, heat resistance, and lithium ion permeability, ensuring safety and output performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the separator thickness is reduced to improve housing efficiency, then the battery size is reduced, but the lithium ion permeability and safety are compromised
Solution Approach 1:
The separator uses a composite structure combining a polyolefin porous layer (providing shutdown function and lithium ion permeability) with a heat-resistant porous layer containing aramid resin and inorganic filler (providing thermal stability). This composite design allows the thin separator to maintain both safety and performance
Solution Approach 2:
Different regions of the separator have specialized functions: the polyolefin layer provides shutdown capability at low temperatures and lithium ion transport, while the heat-resistant layer with aramid resin and inorganic filler provides high-temperature stability. Each layer is optimized for its specific role to achieve overall performance
2Reliability
If a heat-resistant layer is added to ensure safety, then the heat resistance is improved, but the separator thickness increases
Solution Approach 1:
The heat-resistant layer uses finely controlled parameters: inorganic filler particle size of 0.01-1 μm, aramid resin content of 10-40 parts by weight per 100 parts inorganic filler, and layer thickness that keeps the total separator thickness optimized. These parameter optimizations achieve heat resistance without excessive thickness increase
Solution Approach 2:
The heat-resistant layer is designed with porosity of 20-80% to maintain lithium ion permeability while providing thermal stability. The porous structure allows ion transport through the heat-resistant layer, preventing it from becoming a barrier while still providing safety functionality
3Reliability
If the inorganic filler content is increased to improve heat resistance, then the thermal stability is improved, but the lithium ion permeability decreases
Solution Approach 1:
The inorganic filler particle size is optimized to 0.01-1 μm, and the filler content is controlled at 10-40 parts by weight per 100 parts aramid resin. The porosity is maintained at 20-80% to ensure sufficient lithium ion transport pathways while providing adequate thermal stability
Solution Approach 2:
The heat-resistant layer is designed with controlled porosity (20-80%) to maintain lithium ion permeability while containing the inorganic filler. The porous structure provides channels for ion transport, preventing the filler from completely blocking ion pathways while still providing thermal stability
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 separator is thin, durable, and maintains high output performance while ensuring safety, enabling size reduction and efficient housing in battery cases.
Implementation Method 1
The shutdown function is a function to cause melting when the battery generates heat, to close the pores, and block the migration of lithium ions. The porous layer having the shutdown function becomes a substantially non-porous layer at high temperatures.
Implementation Method 2
a separator formed by stacking a layer made of an aramid resin excellent in heat resistance and a porous layer having a shutdown function
Data Source
AI summary
A separator for use in a non-aqueous electrolyte secondary battery including a first porous layer (layer A) having a shutdown function which becomes substantially a non-porous layer at a high temperature, and a second porous layer (layer B) including an aramid resin and an inorganic material, wherein a ratio (TA/TB) of a thickness (TA) of the layer A relative to a thickness (TB) of the layer B is 2.5 or more and 13 or less.