Polyolefin Separator with PVDF Porous Layer for Battery Cycle Life
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Solution Overview
Problem
Conventional nonaqueous electrolyte secondary batteries have limitations in charge capacity after charge-discharge cycles, necessitating improvements in their charge capacity properties.
Innovation Solution
A nonaqueous electrolyte secondary battery configuration incorporating a polyolefin porous film separator, a porous layer with a polyvinylidene fluoride-based resin, and specific electrode plates, where the polyolefin film has a puncture strength of at least 26.0 gf/g/m2 and a critical load distance ratio within a certain range, and the porous layer contains a minimum of 35.0 mol% α-form polyvinylidene fluoride-based resin, enhancing interface barrier energies and structural stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional polyolefin porous film separator is used, then the battery structure is simple and easy to manufacture, but the charge capacity retention after charge-discharge cycles is poor
Solution Approach 1:
The patent applies composite materials by combining polyolefin porous film with a porous layer containing polyvinylidene fluoride-based resin. This composite structure integrates the mechanical strength and shutdown function of polyolefin with the electrochemical stability and interface barrier properties of PVDF resin, thereby improving charge capacity retention while maintaining manufacturability
Solution Approach 2:
The patent utilizes porous materials by incorporating a porous layer with controlled porosity onto the polyolefin separator. The porous structure allows electrolyte penetration and ion transport while providing a stable interface with electrode materials, enhancing charge capacity retention through improved electrochemical stability
2Strength
If the polyolefin porous film has high puncture strength, then the separator structural stability is improved, but the flexibility and ion permeability may be reduced
Solution Approach 1:
The patent applies local quality by creating a porous layer with specific properties on one or both surfaces of the polyolefin separator. This porous layer has controlled porosity, pore size distribution, and resin composition that optimize ion permeability and electrochemical stability locally at the separator-electrode interface, while the bulk polyolefin maintains high puncture strength
3Reliability
If the porous layer contains high α-form polyvinylidene fluoride-based resin content, then the interface barrier energy is improved, but the manufacturing precision and resin composition control become more difficult
Solution Approach 1:
The patent applies parameter changes by optimizing the α-form PVDF resin content to a specific range (35-90 mass%) and controlling the crystalline structure parameters. This parameter optimization achieves sufficient interface barrier energy (sum not less than 5000 J/mol) while maintaining feasible manufacturing precision through controlled resin composition and processing conditions
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 battery exhibits excellent charge capacity retention after charge-discharge cycles due to improved interface barrier energies and structural stability, preventing degradation and maintaining performance during high-rate charging and discharging.
Implementation Method 1
a nonaqueous electrolyte secondary battery separator including a polyolefin porous film
Implementation Method 2
a porous layer containing a polyvinylidene fluoride-based resin... the polyvinylidene fluoride-based resin containing an α-form polyvinylidene fluoride-based resin in an amount of not less than 35.0 mol%
Data Source
AI summary
A nonaqueous electrolyte secondary battery includes: a separator including a polyolefin porous film; a porous layer containing a polyvinylidene fluoride-based resin; a positive electrode plate; and a negative electrode plate, wherein a sum of interface barrier energies being a predetermined value, the polyolefin porous film having a puncture strength of a predetermined value, the value represented by Formula (1) below being not less than 0.00 and not more than 0.54,|1−T/M| Formula (1),and the polyvinylidene fluoride-based resin containing an α-form polyvinylidene fluoride-based resin in an amount of not less than 35.0 mol %.