Polymer-Modified Lead-Acid Electrolyte for Acid Stratification Mitigation
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Solution Overview
Problem
Acid stratification in flooded lead acid batteries leads to reduced cycle and calendar life due to sulfuric acid consumption and non-uniform current distribution, causing density gradients and convective flows that result in voltage variations and sulfation, especially in partial-state-of-charge operations common in 'start-stop' vehicles.
Innovation Solution
Introducing an acid-soluble and acid-stable polymer with high molecular weight into the electrolyte to increase viscosity, thereby resisting convective flows and reducing acid stratification, which can be achieved by dissolving the polymer in the electrolyte or coating it onto the separator surfaces, or incorporating it into the separator structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the battery operates in partial-state-of-charge (PSOC) to meet start-stop vehicle requirements, then the battery can supply electrical functions during stopped phase and provide sufficient current to restart the engine, but acid stratification occurs leading to shorter cycle and calendar life
Solution Approach 1:
A polymer additive is introduced as an intermediary substance in the electrolyte to mitigate acid stratification. The polymer modifies the electrolyte's properties to reduce density gradients and convective flows, thereby preventing sulfation and extending battery life while maintaining PSOC operation capability
Solution Approach 2:
The physical and chemical parameters of the electrolyte are modified by adding a polymer substance. This changes the electrolyte's viscosity and density characteristics, reducing the severity of acid stratification during PSOC operation and improving overall battery reliability
2Power
If sulfuric acid is consumed at electrodes during discharge, then the battery can provide electrical energy, but density gradients form causing convective flows and acid stratification
Solution Approach 1:
The polymer additive acts as a mediator that reduces the impact of density gradients formed during discharge. By modifying the electrolyte's physical properties, the polymer dampens convective flows and maintains more uniform acid distribution even during high power discharge
Solution Approach 2:
The polymer is pre-added to the electrolyte before battery operation to establish modified electrolyte properties. This preliminary modification prevents severe stratification from developing during discharge, maintaining electrolyte uniformity throughout the discharge process
3Reliability
If current density is higher at the top of the electrode near the strap, then electrical connection is improved, but acid depletion occurs faster at the top leading to non-uniform acid distribution
Solution Approach 1:
The electrolyte's physical parameters are changed by polymer addition, modifying its viscosity and flow characteristics. This reduces the rate of acid depletion at high current density regions and promotes more uniform acid distribution across the electrode surface
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 increased viscosity effectively reduces acid stratification, leading to more uniform acid distribution and improved battery performance by minimizing voltage variations and preventing sulfation, thus extending the battery's life and maintaining performance in 'start-stop' vehicle applications.
Implementation Method 1
introducing an acid-soluble and acid-stable polymer with a high molecular weight into the electrolyte of a battery can be used to reduce acid stratification during use of the battery... the high molecular weight polymer solubilizes in the acid that serves as the electrolyte. The solubilized polymer is believed to increase viscosity near the surfaces of the electrodes. The increase in viscosity is believed to effectively partially immobilize the acid, thereby resisting convective flows and reducing acid stratification.
Implementation Method 2
the high molecular weight polymer solubilizes in the acid that serves as the electrolyte
Implementation Method 3
Multiple ways of introducing the acid-soluble and acid-stable polymer to the electrolyte have been discovered... coating it onto the separator surfaces, or incorporating it into the separator structure.
Data Source
AI summary
Methods of reducing acid stratification with an acid-soluble and acid-stable polymer with a high molecular weight are disclosed herein. Electrolytes and separators for an energy storage device are disclosed herein. The separator includes a coating containing an acid-soluble and acid-stable polymer with a high molecular weight. The electrolyte includes sulfuric acid and an acid-soluble and acid-stable polymer with a high molecular weight. Methods of making the separators disclosed herein and methods of making batteries are also disclosed herein.