Lead-Acid Battery Separators With Solvent-Free Microporous Membranes
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Solution Overview
Problem
Current lead acid battery separators, such as AGM and polyethylene-based separators, face challenges including high costs, limited puncture resistance, and environmental concerns due to the use of organic solvents in their production, which affect their performance and manufacturing efficiency.
Innovation Solution
The development of nonporous polymer sheets that form microporous membranes through cavitation and biaxial stretching or dissolution of acid-soluble fillers, eliminating the need for solvent extraction and enhancing puncture resistance and electrical properties, while being cost-competitive and environmentally friendly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If AGM separators are used to achieve high porosity and uniform electrolyte distribution, then electrical resistance is reduced, but puncture resistance deteriorates
Solution Approach 1:
The patent uses a composite structure combining a non-woven fabric base layer with a microporous membrane layer. The non-woven fabric provides mechanical strength and puncture resistance, while the microporous membrane provides high porosity and low electrical resistance. This composite approach allows both contradictory requirements to be satisfied simultaneously.
Solution Approach 2:
Different regions of the separator have different functions: the non-woven fabric layer handles mechanical support and puncture resistance, while the microporous membrane layer handles ionic conduction and electrolyte distribution. Each layer is optimized for its specific function, resolving the contradiction between strength and electrical properties.
2Reliability
If polyethylene separators with precipitated silica are used to achieve acid wettability, then electrical properties improve, but manufacturing complexity increases due to solvent extraction requirements
Solution Approach 1:
The patent eliminates the need for organic solvent extraction by using a water-based foaming process. The porogen (foaming agent) is removed through water washing instead of organic solvents, simplifying the manufacturing process and eliminating environmental concerns associated with solvent recovery systems.
Solution Approach 2:
The patent replaces the chemical solvent extraction process with a physical foaming process followed by water washing. This substitution eliminates the need for complex solvent recovery systems and reduces manufacturing complexity while achieving the same porosity and electrical properties.
3Strength
If thicker separators are used to improve puncture resistance, then strength increases, but electrical resistance increases
Solution Approach 1:
The patent uses a microporous membrane with controlled porosity (30-80%) that allows ionic conduction through the separator. The porous structure provides low electrical resistance pathways for ion transport, enabling the use of thinner separators that maintain both puncture resistance and low electrical resistance simultaneously.
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 new approach results in battery separators with improved puncture strength, reduced electrical resistance, and enhanced porosity, meeting the performance requirements of lead acid batteries without the use of organic solvents, thus addressing environmental and health concerns.
Implementation Method 1
nonporous polymer sheets in which the porosity manifests itself after cavitation and/or biaxial stretching to form a microporous membrane
Implementation Method 2
nonporous polymer sheets in which the porosity manifests itself after dissolution of an acid soluble filler to form a microporous membrane
Data Source
AI summary
This disclosure relates to battery separators for use in lead acid batteries. In particular, the disclosure relates to nonporous polymer sheets in which the porosity manifests itself after cavitation and/or biaxial stretching to form a microporous membrane. The disclosure also relates to nonporous polymer sheets in which the porosity manifests itself after dissolution of an acid soluble filler to form a microporous membrane. In addition to meeting all battery performance requirements, these microporous membranes eliminate environmental and health concerns because they do not require the use of an organic solvent during their production.