Polyolefin Battery Separator ISR Testing Under Compression
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Solution Overview
Problem
Conventional battery separators face challenges in maintaining low electrical resistance under pressure and elasticity, which can lead to short circuits and safety issues due to electrode swelling and contraction, and existing testing methods do not adequately simulate real battery conditions.
Innovation Solution
Development of a microporous membrane with multiple layers of polyolefin, designed to maintain low electrical resistance and high elasticity under compression, along with improved testing methods such as the internal short resistance test and wetting test apparatus to assess separator performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional battery separators are used, then manufacturing cost is reduced, but electrical resistance increases under pressure leading to safety issues
Solution Approach 1:
The separator is constructed as a multilayer composite structure combining polyolefin base layers with ceramic coating layers. This composite design allows the polyolefin to provide mechanical strength and shutdown function, while the ceramic coating maintains low electrical resistance under compression pressure, preventing short circuits even when electrodes swell and contract.
Solution Approach 2:
The invention modifies the electrical resistance parameter of the separator by applying ceramic coatings with specific dielectric properties. The ceramic layer changes the overall electrical characteristics of the separator, maintaining stable resistance values under varying compression pressures caused by electrode expansion and contraction during battery cycling.
2Adaptability or versatility
If separator elasticity is increased to handle electrode swelling, then battery performance is improved, but manufacturing complexity increases
Solution Approach 1:
The separator is divided into distinct functional layers: a polyolefin base layer providing mechanical elasticity and shutdown function, and a ceramic coating layer providing electrical stability. This segmentation allows each layer to be optimized independently for its specific function while maintaining overall separator performance.
Solution Approach 2:
The multilayer separator structure performs multiple functions simultaneously: the polyolefin base provides mechanical elasticity to accommodate electrode swelling, thermal shutdown capability at elevated temperatures, while the ceramic coating maintains low electrical resistance under compression. This multi-functionality is achieved through a single integrated separator component.
3Measurement precision
If existing testing methods are used, then testing simplicity is maintained, but measurement accuracy deteriorates
Solution Approach 1:
The testing method replaces conventional mechanical puncture strength testing with an electrical measurement approach. By measuring electrical resistance through the separator under controlled compression, the test directly evaluates the separator's ability to prevent short circuits, providing more relevant and accurate data for battery safety assessment.
Solution Approach 2:
The testing apparatus uses electrical fields as an intermediary to assess separator performance. Instead of directly measuring mechanical properties that may not correlate with short circuit prevention, the test uses electrical resistance measurement as an intermediary parameter that directly reflects the separator's functional performance in preventing electrode shorting.
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 microporous membrane exhibits reduced electrical resistance and improved elasticity, enhancing battery safety and performance by effectively handling electrode expansion and contraction, while the new testing methods provide more accurate simulations of battery conditions, improving separator evaluation.
Implementation Method 1
the microporous membrane exhibits an elastic recovery from 50% to 100%
Implementation Method 2
the microporous membrane has an electrical resistance (ER) of less than 10 Ω/mm at a compression pressure of 1,000 lbs
Implementation Method 3
an impedance or LCR device in communication with the conductive blocks
Data Source
AI summary
In one aspect, a method of measuring the internal short resistance of a battery separator comprising one or more layers of a polyolefin is provided. A method comprises applying a force via a force component comprising a ball to a test stack, the test stack comprising an anode, a separator, and a cathode, deforming the test stack until an electrical short occurs, and determining an ISR value for the separator, the value corresponding to an overall ISR, or at least in one of the MD, TD, or Z-direction.