Separator Heat-Resistant Insulating Layer Moisture Control
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Solution Overview
Problem
Existing separators with heat resistant insulation layers for lithium ion secondary batteries face issues with increased adsorption moisture, which affects cycle performance and output performance due to the presence of inorganic particles and binders, leading to mechanical strength problems and potential short circuits.
Innovation Solution
A separator with a heat resistant insulation layer containing ceramic inorganic particles and a binder, where the mass ratio of inorganic particles to binder is optimized between 95:5 to 90:10, and the moisture balance ratio is set between 0.001 and 1.8 to control moisture content, preventing heat contraction and ensuring mechanical strength while maintaining lithium ion permeability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a heat resistant insulation layer containing inorganic particles and binder is formed on the separator, then heat resistance and mechanical strength are improved, but adsorption moisture increases leading to degraded cycle performance and output performance
Solution Approach 1:
The patent applies parameter changes by precisely controlling the mass ratio of inorganic particles to binder (95:5 to 90:10) and the moisture balance ratio (0.001 to 1.8). These parameter optimizations reduce adsorption moisture while maintaining the mechanical strength provided by the heat resistant insulation layer, thereby resolving the contradiction between improved strength and degraded cycle performance
Solution Approach 2:
The patent uses composite materials by forming a heat resistant insulation layer that combines inorganic particles (such as alumina, silica) with a binder polymer. This composite structure provides both the mechanical strength and heat resistance needed, while the optimized composition minimizes adsorption moisture that would otherwise degrade cycle performance
2Strength
If the content of binder in the heat resistant insulation layer is increased to improve mechanical strength, then heat resistance is maintained, but adsorption moisture increases affecting battery performance
Solution Approach 1:
The patent applies parameter changes by optimizing the binder content within a specific range (mass ratio of inorganic particles to binder of 95:5 to 90:10). This controlled parameter adjustment ensures sufficient mechanical strength and heat resistance while limiting adsorption moisture to levels that do not negatively impact output performance
3Reliability
If the separator uses thermoplastic resin to achieve shutdown function, then safety at high temperature is improved, but mechanical strength decreases due to thermal contraction
Solution Approach 1:
The patent uses composite materials by forming a heat resistant insulation layer containing inorganic particles and binder on the thermoplastic resin separator. This composite structure provides the mechanical strength needed to prevent thermal contraction, while the underlying thermoplastic resin separator maintains its shutdown function for safety
Solution Approach 2:
The patent applies segmentation by dividing the separator into two functional layers: the base thermoplastic resin separator that provides shutdown function, and the overlay heat resistant insulation layer that provides mechanical strength. This segmentation allows each layer to perform its specific function without compromising the other
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 optimized separator effectively prevents heat contraction, enhances mechanical strength, and improves both output performance and long cycle life by controlling adsorption moisture, thereby ensuring high safety and efficiency in lithium ion secondary batteries.
Implementation Method 1
forming a heat resistant insulation layer containing inorganic particles and an organic binder as main components
Implementation Method 2
the adsorption moisture amount in the separator is higher than that of a separator only including a porous substrate due to the presence of the heat resistant insulation layer containing the inorganic particles and the binder
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
A separator with a heat resistant insulation layer (1) includes a porous substrate (2), and a heat resistant insulation layer (3) formed on one surface or both surfaces of the porous substrate (2) and containing at least one kind of inorganic particles and at least one kind of a binder, wherein a content mass ratio of the inorganic particles to the binder in the heat resistant insulation layer is in a range from 99:1 to 85:15, a BET specific surface area of the inorganic particles is in a range from 3 m2/g to 50 m2/g, and a ratio of the moisture content per mass of the binder to the BET specific surface area of the inorganic particles is greater than 0.0001 and smaller than 2.