Microporous Battery Separator for High Absorbency and Strength
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Solution Overview
Problem
Existing separators for electricity storage devices face challenges in achieving high liquid absorbency and strength, particularly due to issues with pore formation, heat shrinkage, and interference from inorganic fillers during manufacturing processes.
Innovation Solution
A microporous membrane comprising an inorganic filler and polyolefin resin, with specific ratios and properties, including a content ratio of 20-100 wt% inorganic filler, average pore size of 100-1500 nm, and air permeability of 340 s/100 ml or less, facilitates lamellar pore opening and high liquid absorbency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a separator for an electric power storage device is compressed in the stacking direction of electrodes to improve battery assembly efficiency and reduce defects, then the production speed and quality are improved, but the cycle life of the battery is reduced due to residual stress and deformation
Solution Approach 1:
The compression process is segmented into multiple stages with different compression forces. A first compression force is applied initially, followed by a second compression force after a predetermined time period, allowing the separator to adapt progressively rather than承受ing sudden high stress that would cause permanent deformation
Solution Approach 2:
The compression is applied periodically in two stages: first compression at initial assembly, then second compression after a time interval. This periodic approach allows stress relaxation between compression events, preventing cumulative damage to the separator structure while still achieving the necessary compression for battery assembly efficiency
2Manufacturing precision
If a separator is compressed to reduce internal stress and improve battery quality, then production quality is improved, but the separator may deform and reduce cycle life
Solution Approach 1:
The separator is pre-compressed with a first compression force before final battery assembly, allowing it to adapt to the battery structure in advance. This preliminary compression reduces the need for excessive force during final assembly, preventing permanent deformation while ensuring proper fit and quality
Solution Approach 2:
The multi-stage compression approach acts as a cushioning mechanism, distributing the compressive stress over time rather than applying it all at once. This prevents shock loading that would cause separator deformation, while still achieving the necessary compression for battery quality
3Duration of action of stationary object
If no compression is applied to the separator, then cycle life is maintained, but production efficiency decreases and defects increase
Solution Approach 1:
The compression force is made dynamic rather than static, changing over time with two distinct compression stages. This dynamic approach allows the system to achieve high production efficiency through initial compression while preserving cycle life through stress relaxation periods, unlike constant compression which would permanently damage the separator
Data Source
Figure 1
AI summary
Provided are: a separator for an electric power storage device, the separator having high liquid absorption and high strength; and an electric power storage device in which the separator is used. The separator for an electric power storage device includes a microporous membrane (A) containing an inorganic filler and a polyolefin resin. The microporous membrane (A) has a MFR of 0.05-5 inclusive, includes not less than 20 mass% but less than 100 mass% of the organic filler, has an average pore diameter of 100-1500 nm inclusive for the pores in a cross-section ND-MD, and has an air permeability of 340 sec/100 mL or less.