Separator Drying Control for Lithium-Ion Battery Curling
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Solution Overview
Problem
The existing separators with a heat-resistant insulating layer for lithium-ion secondary batteries tend to curl during manufacturing, leading to short circuits and reduced yield due to thermal contraction.
Innovation Solution
A method involving a drying step to control the water content of the heat-resistant insulating layer within a specific range, defined by the equation 1−4πX≤Y≤1+4πX, where X is the thickness-to-length ratio of the separator, to prevent curling and ensure proper lamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a heat-resistant insulating layer is laminated on the resin porous membrane to suppress thermal contraction, then heat resistance is improved, but curling occurs during manufacturing
Solution Approach 1:
The invention changes the water content parameter of the separator to a specific range (0.1-5% by weight) to control the dimensional stability during drying. By controlling this parameter, the differential shrinkage between the heat-resistant layer and substrate is reduced, preventing curling while maintaining heat resistance
Solution Approach 2:
The invention performs preliminary drying treatment before battery assembly to control the water content in advance. This preliminary action establishes the optimal moisture state that prevents subsequent curling during battery manufacturing processes
2Manufacturing precision
If the separator is dried to remove water content, then manufacturing precision is improved, but manufacturing complexity increases due to dew point control requirements
Solution Approach 1:
The invention implements feedback control by monitoring the dew point during drying and adjusting drying conditions accordingly. The dew point serves as a feedback parameter to determine when the water content reaches the target range, enabling precise control without excessive complexity
Solution Approach 2:
The invention defines specific dew point ranges corresponding to the target water content range. By controlling the dew point parameter during drying, the process achieves the desired water content (0.1-5% by weight) while maintaining manageable process complexity through clear parameter specifications
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
This approach effectively suppresses curling and improves the yield of lithium-ion secondary batteries by maintaining the shape stability of the separator during lamination, enhancing the battery's performance and manufacturing efficiency.
Implementation Method 1
a heat-resistant insulating layer provided separator having a heat-resistant insulating layer formed of oxide particles on one surface of the resin porous substrate
Implementation Method 2
a drying step is provided for drying the heat-resistant insulating layer provided separator so that the amount of water contained or water content in the heat-resistant insulating layer provided separator remains in a predetermined range
Data Source
AI summary
A method for producing a lithium ion secondary battery in which a positive electrode, a heat-resistant insulating layer provided separator having a heat-resistant insulating layer formed of oxide particles on one surface of a resin porous substrate, and a negative electrode are laminated on one another, and a nonaqueous electrolyte is impregnated in the heat-resistant insulating layer provided separator, includes drying the heat-resistant insulating layer provided separator before laminating so that the water content in the heat-resistant insulating layer provided separator remains in a predetermined range. In the drying, the water content in the heat-resistant insulating layer provided separator is decreased to the predetermined range by controlling the dew point and maintaining the predetermined range after reaching the predetermined range of water content.