Battery Separator Puncture Evaluation Using Substrate Support
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Solution Overview
Problem
Conventional puncture strength tests are inadequate for evaluating the strength of battery separators, as they do not accurately simulate the conditions within a battery and fail to distinguish the separator's strength from the underlying electrode material, especially when the separator is bonded to the electrode.
Innovation Solution
An evaluation method involving a test piece with the separator supported by a substrate, where a puncturing tool is inserted in the thickness direction to measure the load at a predetermined short circuit resistance, simulating the deformation of a separator inside a battery, and evaluating the separator based on the short circuit load and displacement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional puncture strength test is used to evaluate separator strength, then the test is simple to perform, but the results do not accurately reflect the separator's strength in actual battery conditions
Solution Approach 1:
An electrode unit is introduced as an intermediary test object that combines the separator with electrode materials. This allows the test to evaluate the separator's strength in a configuration that closely mimics actual battery conditions, where the separator is bonded to electrodes and constrained from extending in the thickness direction.
Solution Approach 2:
The separator is pre-bonded to the electrode to form an electrode unit before testing. This preliminary bonding action creates the constrained configuration that exists in actual batteries, ensuring that the separator cannot extend in the thickness direction during the puncture test, thus providing accurate strength evaluation.
2Reliability
If the separator is bonded to the electrode to form an electrode unit, then the actual battery conditions are simulated, but it becomes difficult to distinguish the separator's strength from the electrode material's strength
Solution Approach 1:
The electrode unit is extracted as a complete test object that includes both the separator and electrode materials bonded together. By testing the electrode unit as a whole rather than trying to separate the measurements, the method captures the actual load-bearing behavior of the separator in its operational context, where it is constrained by the electrode.
3Strength
If the separator is allowed to extend in the thickness direction during testing, then the puncture strength is higher, but this does not reflect the actual battery environment where there is little space for extension
Solution Approach 1:
The separator is pre-bonded to the electrode to form an electrode unit before testing. This preliminary bonding action creates the constrained configuration that exists in actual batteries, ensuring that the separator cannot extend in the thickness direction during the puncture test, thus providing accurate strength evaluation.
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
This method effectively assesses the separator's ability to maintain insulation without breaking when a foreign object enters, providing a reliable index for design, development, and production by measuring the short circuit load and displacement, which correlates with the separator's strength within a battery environment.
Implementation Method 1
measuring an electrical resistance between the puncturing tool and the substrate while the puncturing tool is being stuck into the separator
Data Source
AI summary
A separator is placed on a surface of a substrate to prepare a test piece. A puncturing tool is stuck into the separator, from a side of the test piece opposite to where the substrate is placed, in a thickness direction of the separator. An electrical resistance between the puncturing tool and the substrate is measured. The separator is evaluated based on a magnitude of a load applied to the puncturing tool at the time when the electrical resistance has decreased to a predetermined value. Each of the substrate and the puncturing tool is electrically conductive.