Battery Separator Damage Detection by Rolling Pressure and Leakage Current
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Solution Overview
Problem
Conventional methods for detecting separator damage in lithium secondary batteries face challenges in reliably identifying defects with low voltage application and accurately locating the damage position, leading to potential misclassification of non-defective separators as defective and failure to identify the cause of defects.
Innovation Solution
A separator damage detecting apparatus and method that applies a voltage while pressing the electrode assembly using rollers or partial pressing plates to induce a temporary short circuit, enhancing defect detection ability and enabling precise localization of damage by measuring leakage current and roller movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a voltage lower than the dielectric breakdown voltage of the separator is applied, then the risk of false defect detection is reduced, but the separator defect detection ability is deteriorated
Solution Approach 1:
The electrode assembly is pressed in advance using a pressing plate to temporarily induce short circuit between positive and negative electrodes at defect locations before voltage application. This preliminary mechanical action creates a conductive path at defect sites, enabling detection at lower voltages without compromising detection sensitivity or causing false positives on good separators.
2Measurement precision
If a voltage higher than a proper level is applied, then the separator defect detection ability is improved, but a normal separator portion suffers from dielectric breakdown
Solution Approach 1:
The pressing operation is performed before voltage application to pre-establish short circuit paths at any existing defect locations. This ensures that subsequent low-voltage application will only detect actual defects rather than requiring high voltage that could damage healthy separators.
3Reliability
If surface pressure is applied to the electrode assembly, then the distance between electrodes is reduced to induce short circuit, but the pressure distribution varies depending on flatness of the pressure plate
Solution Approach 1:
A cylindrical pressing roller is used instead of a flat pressure plate. The curved surface of the roller ensures uniform pressure distribution across the electrode assembly width as it rolls, eliminating the pressure variation problems associated with flat plates and improving both reliability and precision of the detection process.
Solution Approach 2:
The pressing plate is transformed into a movable roller that rotates during the pressing operation. This dynamic rolling action provides consistent pressure application and improves uniformity compared to static pressing methods, while also enabling the roller to conform to slight variations in electrode assembly flatness.
4Loss of information
If the damage position of the separator is identified, then the cause of defect can be analyzed and process improvement is enabled, but conventional methods only determine whether separator is damaged or not
Solution Approach 1:
The system measures leakage current as a function of time during the rolling pressing operation. By correlating the timing of leakage current detection with the position of the roller, the system provides feedback that enables calculation of the exact damage position. This transforms a simple pass/fail detection into a diagnostic tool that provides actionable location information for process improvement.
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 apparatus improves defect detection reliability and accuracy by uniformly increasing pressure across unit cell areas, allowing for precise identification of damage positions and facilitating process improvements to prevent future defects.
Implementation Method 1
pressing an electrode assembly having a structure in which a positive electrode plate, a separator and a negative electrode plate are stacked, to induce a temporary short circuit
Implementation Method 2
detect a leakage current
Data Source
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AI summary
Disclosed is a separator damage detecting apparatus. The separator damage detecting apparatus detects a separator damage of a secondary battery by applying a voltage while pressing an electrode assembly having a structure in which a positive electrode plate, a separator and a negative electrode plate are stacked, to induce a temporary short circuit of a positive electrode plate and a negative electrode plate. The separator damage detecting apparatus includes a short circuit measuring unit configured to apply a voltage to the electrode assembly and detect a leakage current; and a pressing jig configured to roll-press at least one surface of the electrode assembly or consecutively press predetermined regions of the at least one surface of the electrode assembly.