Battery Separator Composite Structure for Voltage Resistance
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Solution Overview
Problem
Nonaqueous electrolyte secondary battery separators, despite being shaped into a bag-like form, can still experience short circuits due to deterioration at specific points under voltage stress between the cathode and anode, necessitating an enhancement in voltage-withstanding properties.
Innovation Solution
A nonaqueous electrolyte secondary battery separator with a porous film made of polyolefin-based resin, featuring a peeling strength of at least 0.2 N and puncture strength change of no more than 15% through a blocking test, ensuring effective heat-sealing and structural integrity to prevent short circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a separator is shaped into a bag-like form by heat-sealing porous films, then the separator can prevent short circuits between cathode and anode, but the separator deteriorates under voltage stress and short circuits may still occur
Solution Approach 1:
The invention uses a composite structure consisting of a porous film and a heat-sealing film layered together. The porous film provides short circuit prevention functionality while the heat-sealing film enhances voltage-withstanding properties. This composite material approach resolves the contradiction by combining materials with complementary properties to achieve both reliable short circuit prevention and improved voltage resistance.
Solution Approach 2:
The invention changes the physical and chemical parameters of the separator by specifying particular properties for the porous film (porosity, pore size distribution) and the heat-sealing film (melting point, sealing strength). By optimizing these parameters, the separator maintains its short circuit prevention capability while significantly improving its voltage-withstanding properties to prevent deterioration under voltage stress.
2Reliability
If the separator uses porous film structure, then ion permeability is maintained, but the voltage-withstanding property deteriorates under operating conditions
Solution Approach 1:
The composite structure combines a porous film that maintains ion permeability with a heat-sealing film that provides enhanced voltage-withstanding strength. The porous film allows ion transport while the heat-sealing film reinforces the structure to resist voltage-induced deterioration, resolving the contradiction between maintaining ion permeability and improving voltage resistance.
Solution Approach 2:
The invention applies different material properties to different parts of the separator structure. The porous film region maintains high ion permeability for electrochemical performance, while the heat-sealing film region provides enhanced mechanical strength and voltage resistance. This local differentiation of material qualities allows the separator to simultaneously achieve good ion permeability and improved voltage-withstanding properties.
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 solution achieves a nonaqueous electrolyte secondary battery with excellent voltage-withstanding properties, maintaining safety by preventing short circuits and ensuring reliable operation.
Implementation Method 1
a separator is shaped into a bag-like form by heat-sealing respective surfaces of two porous films
Implementation Method 2
the blocking test being carried out by (i) sandwiching, by a jig of 100 mm×100 mm, two 80 mm×80 mm pieces of the nonaqueous electrolyte secondary battery separator, (ii) allowing the two 80 mm×80 mm pieces to rest under a load of 3.5 kg at a temperature of 133° C.±1° C. for 30 minutes
Data Source
AI summary
Provided is a nonaqueous electrolyte secondary battery separator excellent in voltage-withstanding property. This nonaqueous electrolyte secondary battery separator has (i) a film thickness of not more than 20 μm, (ii) a peeling strength, measured by a blocking test, of not less than 0.2 N, and (iii) a puncture strength that changes through the blocking test by not more than 15%. The blocking test is carried out by (i) sandwiching, by a jig of 100 mm×100 mm, two 80 mm×80 mm pieces of a separator, (ii) allowing the two 80 mm×80 mm pieces to rest for 30 minutes under a load of 3.5 kg at a temperature of 133° C.±° C., (iii) removing the load, (iv) cooling the two 80 mm×80 mm pieces to room temperature, (vi) cutting out a specimen of 27 mm×80 mm from the two 80 mm×80 mm pieces, and then (vi) measuring a peeling strength of the specimen at 100 mm/min.