Lead-Acid Battery Separator Rib Profiles for Acid Starvation
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Solution Overview
Problem
Lead acid batteries operating in partial state of charge (PSoC) face issues with acid starvation, stratification, and reduced cycle life due to NAM swelling, which affects electrode contact and electrolyte distribution, leading to performance degradation and reduced battery life.
Innovation Solution
A novel lead acid battery separator with a porous membrane and a unique rib design, incorporating performance-enhancing additives and a shish-kebab morphology, which provides increased porosity, tortuosity, and wettability, ensuring better acid diffusion and resistance to swelling-induced deflection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional separators are used in lead acid batteries operating in partial state of charge, then the battery structure is simple and manufacturing is easy, but acid starvation and stratification occur leading to reduced battery life
Solution Approach 1:
The separator is divided into multiple functional layers including a base layer and an overlay layer with distinct rib structures. The overlay layer contains ribs with optimized dimensions and spacing to prevent NAM swelling while maintaining acid flow pathways, thereby segmenting the separator functionality to simultaneously achieve reliability and controlled complexity
Solution Approach 2:
The separator employs composite construction with a base layer made of porous polyolefin material and an overlay layer with specific rib profiles and porosity characteristics. This composite structure combines materials with different properties to resist swelling forces while maintaining acid diffusion, improving battery life without excessive complexity
2Strength
If the separator ribs are made thicker to resist NAM swelling, then separator strength and swelling resistance improve, but acid diffusion to electrodes is hindered
Solution Approach 1:
The rib structures are designed with non-uniform cross-sections featuring varying thicknesses - thicker at the base for strength and swelling resistance, tapering to thinner edges to maintain acid diffusion pathways. This local quality variation allows the separator to simultaneously achieve high swelling resistance while preserving acid availability to electrodes
Solution Approach 2:
The separator ribs are constructed with controlled porosity and interconnected pore structures that allow acid to penetrate through and around the ribs. The porous nature of the rib materials themselves provides additional acid diffusion pathways, maintaining acid availability while the overall rib structure provides the necessary mechanical strength to resist NAM swelling
3Reliability
If the separator is made more resilient to resist deflection, then electrode contact is maintained, but electrical resistance increases
Solution Approach 1:
The separator is designed with dynamic resiliency characteristics that allow it to deflect elastically in response to NAM swelling forces and then recover. This dynamic behavior maintains continuous electrode contact during battery cycling without requiring excessive static stiffness, thereby maintaining reliability while minimizing electrical resistance
Solution Approach 2:
The separator design merges the rib structures with the base layer to create an integrated resilient framework. The ribs are not separate additions but are integrally formed with the base layer, creating a unified structure that provides both mechanical support for electrode contact and maintains electrical conductivity pathways, reducing overall electrical resistance
4Stability of the object's composition
If the rib spacing is reduced to improve acid distribution, then acid stratification is reduced, but manufacturing precision requirements increase
Solution Approach 1:
The separator design incorporates self-aligning rib features that automatically position themselves during the manufacturing process, reducing dependence on tight tolerances. The rib structures are designed to naturally space themselves through mold features or material properties, achieving uniform acid distribution while minimizing manufacturing precision requirements
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 improved separator enhances acid availability, reduces acid stratification, and extends battery life by maintaining electrode contact, improving charge acceptance, and lowering electrical resistance, thus matching the performance of more expensive AGM batteries.
Implementation Method 1
improving acid diffusion
Implementation Method 2
increasing, enhancing, or improving wettability
Data Source
AI summary
Disclosed herein are exemplary embodiments of improved separators for lead acid batteries, improved lead acid batteries incorporating the improved separators, and vehicles, devices, or systems incorporating the same. A lead acid battery separator is provided with a porous membrane with a plurality of ribs extending from a surface thereon. The plurality of ribs preferably includes both positive ribs and negative ribs having similar heights. The ribs are provided with a plurality of discontinuous peaks arranged such as to provide resilient support for the porous membrane in order to resist forces exerted by active material swelling and thus mitigate the effects of acid starvation associated with such swelling, and increasing the acid availability at the electrodes. A lead acid battery is further provided that incorporates the provided separator. Such a lead acid battery may be a flooded lead acid battery, an enhanced flooded lead acid battery, a gel battery, an AGM battery, and may be provided as operating in a partial state of charge. Systems incorporating such a lead acid battery are also provided, such as a vehicle or any other energy storage system, such as solar or wind energy collection. Other exemplary embodiments are provided such as to have any one or more of the following: increased or improved acid availability, reduced or mitigated acid starvation, and other improvements.