Battery Separators with Controlled Pore Structure for Acid Distribution
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Solution Overview
Problem
Lead-acid batteries face challenges in achieving uniform electrolyte distribution and preventing acid stratification, which leads to performance issues and premature failure due to the competition between the separator and plate surfaces for electrolyte, resulting in uneven acid concentration and potential short circuits.
Innovation Solution
A battery separator made from glass fibers with controlled density, specific surface area, and mean pore size, as defined by the equation mean pore size < (270 * basis weight)^0.53 * 1.6 * specific surface area * (65 * density - 1.8), allowing for a higher percentage of coarser fibers to achieve desired attributes like wet tensile strength and pore size without increasing cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If finer glass fibers are used to achieve smaller mean pore size and higher wet tensile strength, then separator performance improves, but manufacturing cost increases
Solution Approach 1:
The patent applies parameter changes by establishing a mathematical relationship between mean pore size, basis weight, specific surface area, and density. This allows optimization of fiber composition and separator structure to achieve desired performance attributes without necessarily using finer fibers, thereby controlling manufacturing cost while maintaining reliability.
Solution Approach 2:
The patent uses composite materials by combining glass fibers with different characteristics (varying diameters, lengths, and compositions) to create a separator that achieves the required mean pore size and wet tensile strength. This composite approach allows using a mix of fiber types including coarser fibers, reducing the need for expensive finer fibers while maintaining performance.
2Manufacturing precision
If the separator holds up electrolyte strongly through capillary forces, then electrolyte distribution improves, but acid stratification occurs due to competition with plate surfaces
Solution Approach 1:
The patent changes physical parameters of the separator including mean pore size, basis weight, specific surface area, and density to optimize electrolyte distribution. By controlling these parameters within specific ranges, the separator achieves balanced capillary action that distributes electrolyte uniformly without causing excessive holding that leads to stratification.
Solution Approach 2:
The patent utilizes porous materials by carefully designing the separator's pore structure with controlled mean pore size, porosity, and specific surface area. This optimized porous structure allows appropriate electrolyte penetration and distribution while preventing the capillary forces from being too strong, thereby avoiding acid stratification caused by excessive electrolyte retention.
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 ensures balanced performance attributes in battery separators, improving wet tensile strength and acid distribution, reducing the risk of acid stratification and premature failure, while potentially lowering costs by using more affordable coarser fibers.
Implementation Method 1
the separator (the capillary forces tend to hold the electrolyte rather strongly)
Implementation Method 2
all areas are wetted as much as possible by the same amount and concentration of acid so that there is perfectly uniform distribution of electrolyte throughout the plate stack
Data Source
AI summary
Disclosed are battery separators comprising glass fibers and having a basis weight (gsm), a specific surface area (m2/g), a density (gsm/mm) and a mean pore size (μm), which satisfy the equation disclosed herein. Also disclosed are batteries comprising the battery separators, and processes for making the separators.