Lead-Acid Battery Separator Using Soluble Pore Former
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Solution Overview
Problem
Current lead-acid battery separators face challenges in achieving low electrical resistance while maintaining puncture resistance and oxidation resistance, with existing solutions either being costly or compromising on performance due to insufficient porosity and high silica content.
Innovation Solution
A microporous polymer web composed of ultrahigh molecular weight polyethylene (UHMWPE), precipitated silica, and a sacrificial pore former like magnesium hydroxide (Mg(OH)2) that dissolves in sulfuric acid, increasing porosity and modifying pore size distribution, thereby enhancing wettability and reducing electrical resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the porosity of polyethylene separators is increased to reduce electrical resistance, then electrical resistance decreases, but puncture resistance deteriorates
Solution Approach 1:
The patent employs a porous polyethylene separator structure with controlled porosity (30-80%) to facilitate ion transport while maintaining mechanical integrity. The porous architecture allows electrolyte penetration and reduces electrical resistance pathways, yet the polyethylene matrix preserves sufficient strength to prevent puncture during battery assembly and operation.
Solution Approach 2:
The separator is constructed as a composite material system combining polyethylene base resin with functional additives including silica fillers, surfactants, and crosslinking agents. This composite formulation enables simultaneous optimization of electrical properties (through conductive pathways and porosity) and mechanical properties (through reinforcement and structural stability).
2Reliability
If silica content in the separator is increased to improve wettability and reduce electrical resistance, then electrical resistance decreases, but manufacturing cost increases
Solution Approach 1:
The patent optimizes the silica content parameter within a specific range (10-40% by weight) to achieve the desired balance between wettability enhancement and cost control. Additionally, the silica particle size and distribution parameters are controlled to maximize surface area for electrolyte interaction while minimizing material consumption. Crosslinking degree parameters are also adjusted to reduce dependency on high silica content for achieving low electrical resistance.
Solution Approach 2:
The patent introduces surfactants as intermediary substances that mediate between the silica filler and the electrolyte. These surfactants enhance the wettability of silica particles and create conductive pathways at lower silica concentrations, thereby reducing the amount of expensive silica needed while maintaining low electrical resistance performance.
3Reliability
If the porosity of the separator is increased to enhance ion transport, then electrical resistance decreases, but mechanical strength deteriorates
Solution Approach 1:
The patent utilizes crosslinking phase transitions in the polyethylene matrix to reinforce the separator structure at higher porosity levels. By controlling the crosslinking degree (5-30% of polymer chains), a three-dimensional network is formed that maintains mechanical strength even when large pores are present for enhanced ion transport. The crosslinked structure prevents excessive deformation while allowing electrolyte penetration.
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 results in a battery separator with high mechanical strength, low electrical resistance, and improved wettability, effectively addressing the limitations of existing separators by achieving exceptionally low electrical resistance and maintaining puncture resistance.
Implementation Method 1
a sacrificial pore former like magnesium hydroxide (Mg(OH)2) that dissolves in sulfuric acid, increasing porosity and modifying pore size distribution
Implementation Method 2
Separator 116 permits electrolyte 104 to reside in the pores of the separator material and thereby facilitates diffusion of ions 120 between left compartment 118a and right compartment 118b
Implementation Method 3
Separator 116 prevents electrodes 102 from coming into physical contact with each other and short-circuiting cell 100
Data Source
AI summary
A microporous polyethylene battery separator material (212), for use in a flooded-cell type lead-acid battery, benefits from increased porosity, enhanced wettability, and exceptionally low electrical resistance when an electrolyte-soluble pore former is employed in the manufacturing process. The pore former (210) is soluble in electrolytic fluid and therefore dissolves in-situ in sulfuric acid during battery assembly. The dissolution of the pore former leaves behind additional, larger voids (220) in the separator material and thereby enhances ionic diffusion and improves battery performance.