Polyolefin Separator Laminate for Battery Safety
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Solution Overview
Problem
Non-aqueous electrolyte secondary batteries face challenges in maintaining safety and performance capabilities, particularly in preventing internal short circuits due to breakage, and existing evaluation methods fail to ensure high safety while maintaining these characteristics.
Innovation Solution
A laminate comprising a porous film with polyolefin as the main component and a porous layer with fine particles, where the difference in test force between electrical conduction and dielectric breakdown in a nail penetration test is measured, ensuring a safety level by preventing internal short circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If inorganic compounds or particles are added to the separator to improve safety by preventing internal short circuits, then safety is improved, but the rate characteristic and resistance characteristic of the battery deteriorate
Solution Approach 1:
The patent uses a porous coating layer containing inorganic fine particles with specific pore structures to maintain ion permeability while providing safety functions. The porous structure allows electrolyte penetration and ion transport, preventing deterioration of rate and resistance characteristics while the inorganic particles provide thermal stability and prevent internal short circuits.
Solution Approach 2:
The patent creates a composite separator structure by coating inorganic fine particles onto the porous film substrate. This composite structure combines the mechanical strength and ion permeability of the porous film with the thermal stability and safety features of the inorganic particles, resolving the contradiction between safety improvement and performance maintenance.
2Reliability
If the separator structure is modified to enhance safety features, then internal short circuit prevention is improved, but the battery performance capabilities deteriorate
Solution Approach 1:
The patent applies inorganic fine particles locally on the separator surface through a coating layer, rather than uniformly throughout the entire separator structure. This localized modification provides safety enhancement at the electrode interface while maintaining the bulk separator's ion permeability and electrical properties, thus preserving battery performance.
Solution Approach 2:
The patent carefully controls parameters such as particle size (0.1-10 μm), coating layer thickness (1-20 μm), and inorganic content (1-50 wt%) to optimize the balance between safety and performance. By adjusting these parameters, the separator provides adequate safety protection without excessively increasing resistance or reducing ion transport capability.
Data Source
AI summary
Provided is a laminate which is capable of ensuring a high level of safety by preventing an internal short circuit due to, for example, breakage of a non-aqueous electrolyte secondary battery while maintaining various performance capabilities of the non-aqueous electrolyte secondary battery. A laminate (10) includes: a porous film containing polyolefin as a main component; and a porous layer containing fine particles; the porous layer being laminated to at least one side of the porous film, in an electrical conduction test by nail penetration in which test a difference between (a) a test force of the laminate (10) which is brought into electrical conduction and (b) a test force of the laminate (10) in which a dielectric breakdown occurs, the difference being obtained by subtracting the test force (b) from the test force (a), is measured by use of a nail (2) of N50 specified in JIS A 5508 and under a condition in which the nail (2) descends at a descending speed of 50 μm/min, the difference being not less than 5 N and not more than 50 N.