PVDF Porous Layer Separator for High-Rate Battery Discharge
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Solution Overview
Problem
Conventional nonaqueous electrolyte secondary batteries have limitations in high-rate discharge characteristics, specifically in terms of discharge capacity, due to insufficient internal resistance reduction and capacitance optimization of electrode plates.
Innovation Solution
The battery design includes a polyolefin porous film separator with a porous layer containing a polyvinylidene fluoride-based resin, where the α-form polyvinylidene fluoride-based resin constitutes at least 35.0 mol % of the total content, and electrode plates with specific capacitance ranges (1 nF to 1000 nF for the positive electrode and 4 nF to 8500 nF for the negative electrode per 900 mm², optimized by viscoelasticity measurements and NMR spectrum analysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional nonaqueous electrolyte secondary battery uses a polyolefin porous film separator, then the internal resistance increase rate is reduced, but the high-rate discharge capacity characteristic is insufficient
Solution Approach 1:
The patent introduces a porous layer containing polyvinylidene fluoride-based resin with specific crystal forms (α-form and β-form) on the polyolefin porous film separator. This porous structure promotes ion solvation and desolvation, enhancing high-rate discharge capacity while maintaining internal resistance stability through the controlled porosity and resin composition.
Solution Approach 2:
The patent creates a composite structure by combining the polyolefin porous film separator with a porous layer containing polyvinylidene fluoride-based resin. This composite material integrates the thermal stability and shutdown function of polyolefin with the ion-conducting properties of PVDF resin, resolving the contradiction between reliability and productivity.
2Productivity
If the porous layer contains polyvinylidene fluoride-based resin with specific crystal forms, then ion solvation and desolvation are promoted, but the manufacturing precision requirements increase
Solution Approach 1:
The patent specifies precise parameters for the PVDF resin including crystal form composition (α-form and β-form ratios), molecular weight range, and porosity. By controlling these parameters within defined ranges, the invention achieves optimal ion permeability while providing clear manufacturing specifications that balance precision requirements with producibility.
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
This configuration enhances the discharge capacity characteristic during high-rate discharge by promoting ion solvation and desolvation, improving permeability and output characteristics, thereby correcting uneven capacity distribution and maintaining structural stability under high-rate conditions.
Implementation Method 1
enhances the discharge capacity characteristic during high-rate discharge by promoting ion solvation and desolvation
Implementation Method 2
a nonaqueous electrolyte secondary battery separator including a polyolefin porous film; a porous layer containing a polyvinylidene fluoride-based resin
Data Source
AI summary
A nonaqueous electrolyte secondary battery in accordance with an embodiment of the present invention includes: a separator including a polyolefin porous film; a porous layer containing a polyvinylidene fluoride-based resin; and a positive electrode plate and a negative electrode plate each of which has a capacitance in a specific range, the polyolefin porous film having a parameter X of not more than 20, and the polyvinylidene fluoride-based resin containing not less than 35.0 mol % of an α-form polyvinylidene fluoride-based resin.