Laminated Separator with Crystal Form Alpha Resin
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Solution Overview
Problem
Nonaqueous electrolyte secondary batteries face issues with separator curling due to adhesive material coatings, leading to increased internal resistance and degraded cycle characteristics, and difficulties in handling during battery production.
Innovation Solution
A laminated body comprising a porous base material with a polyolefin-based resin and a porous layer containing a polyvinylidene fluoride-based resin with controlled crystal forms, specifically with a phase difference of not more than 80 nm and a porosity of 30-60%, is used as a separator to prevent curling and reduce internal resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a separator is coated with an adhesive material such as polyvinylidene fluoride to increase adhesiveness between the separator and electrodes, then the adhesiveness is improved, but the separator curls visibly which causes handling difficulties during production
Solution Approach 1:
The invention changes the crystal form parameter of the polyvinylidene fluoride-based resin from conventional forms to specifically crystal form α, which has different physical properties including lower shrinkage during battery assembly. This parameter change maintains the adhesive function while eliminating the curling problem that occurs with other crystal forms.
Solution Approach 2:
The invention uses a composite structure where the porous base material and the porous layer containing polyvinylidene fluoride-based resin with crystal form α are combined. The porous base material provides structural support and dimensional stability, while the porous layer provides adhesiveness, creating a composite that achieves both good adhesion and flatness without curling.
2Reliability
If the porous base material has higher porosity to improve electrolyte penetration, then ion conductivity is improved, but the mechanical strength decreases making the separator more vulnerable
Solution Approach 1:
The composite structure combines a porous base material with high porosity (30-80%) for excellent ion conductivity with a porous layer containing polyvinylidene fluoride-based resin for mechanical reinforcement. The base material ensures efficient electrolyte penetration and ion transport, while the porous layer provides the necessary mechanical strength and structural integrity, allowing the separator to maintain both high ion conductivity and adequate mechanical strength.
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 effectively prevents separator curling and lowers internal resistance in nonaqueous electrolyte secondary batteries, enhancing their cycle characteristics and ease of handling during production.
Implementation Method 1
the porous base material having (i) a phase difference of not more than 80 nm with respect to light with a wavelength of 590 nm
Implementation Method 2
the polyvinylidene fluoride-based resin containing crystal form α in an amount of not less than 34 mol % with respect to 100 mol % of a total amount of the crystal form α and crystal form β contained in the polyvinylidene fluoride-based resin
Implementation Method 3
a porous layer disposed on at least one surface of the porous base material, the porous layer containing a polyvinylidene fluoride-based resin
Implementation Method 4
the porous base material having (ii) a porosity within a range of 30% to 60%
Data Source
AI summary
A laminated body includes: a porous base material containing a polyolefin-based resin as a main component, the porous base material having a predetermined phase difference and porosity; and a porous layer disposed on at least one surface of the porous base material, the porous layer containing a polyvinylidene fluoride-based resin, the polyvinylidene fluoride-based resin containing crystal form α in an amount of not less than 34 mol % with respect to 100 mol % of a total amount of the crystal form α and crystal form β contained in the polyvinylidene fluoride-based resin.