Battery Cell Compression Screening for Self-Discharge Defects
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Solution Overview
Problem
Existing methods fail to detect abnormal self-discharge in electrochemical cells before assembly into batteries, leading to economic and environmental losses due to defective cells being assembled, which can cause entire battery or module discard and potential recall campaigns.
Innovation Solution
A method and apparatus for monitoring self-discharge in electrochemical cells by arranging and compressing cells along a specific direction, measuring voltage differences, and discarding cells with abnormal self-discharge before assembly, using a support structure and detection system to identify latent defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If voltage measurement is performed only after cell assembly into batteries, then defective cells can be detected, but entire batteries or modules must be discarded due to latent defects, causing economic and environmental losses
Solution Approach 1:
The patent applies preliminary action by performing voltage measurements on individual cells before they are assembled into batteries. This allows defective cells to be identified and discarded individually, preventing the need to discard entire batteries or modules that would otherwise be contaminated by latent defects. The measurement process is conducted in advance during the storage period, enabling early detection of abnormal self-discharge phenomena.
2Measurement precision
If periodic voltage measurement is performed on stored cells, then abnormal self-discharge can be detected, but measurement precision is insufficient to detect latent defects that only manifest under compression
Solution Approach 1:
The patent applies parameter changes by introducing a compression force to the cell during voltage measurement. This changes the physical state of the cell, reducing the distance between electrodes and enabling the detection of latent defects such as metal contamination or separator damage that would not cause abnormal self-discharge under normal storage conditions. The compression parameter is applied temporarily during the measurement process to reveal defects that remain dormant without compression.
3Measurement precision
If cells are compressed to detect latent defects, then measurement precision improves, but device complexity increases due to additional compression mechanisms
Solution Approach 1:
The patent applies universality by designing a monitoring device that combines both compression functionality and voltage measurement capabilities in a single integrated system. The device can switch between normal storage mode and measurement mode, where the same device structure serves dual purposes: storing cells during extended periods and performing compressed voltage measurements to detect latent defects. This multi-functionality reduces the need for separate dedicated compression testing equipment.
4Loss of time
If extended storage period is used for cell monitoring, then more time for defect detection, but self-discharge increases and measurement timing becomes critical
Solution Approach 1:
The patent applies feedback by continuously monitoring the voltage of cells during the extended storage period and comparing measurements taken at different time points. The system provides feedback on the rate of self-discharge, allowing operators to identify cells with abnormal self-discharge rates that indicate latent defects. This feedback mechanism enables early detection without requiring the cell to undergo excessive self-discharge, optimizing the measurement timing within the extended storage window.
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
Enables early detection of defective cells, preventing assembly into batteries and reducing economic and environmental impacts by discarding only defective cells, thus avoiding recalls and improving manufacturing efficiency.
Implementation Method 1
lithium batteries, thanks to their high energy density, allow electric drive systems to be more and more implemented in the automotive industry. In particular, lithium ions currently represent, from a chemical point of view, the state of the art in the production of high-capacity batteries.
Implementation Method 2
The cells are subjected to self-discharge phenomena. In particular, over time a cell tends to decrease its charge (namely, its 'state of charge', simultaneously decreasing its voltage), even if the cell is not used, for example while the cell is stored.
Data Source
AI summary
A method for monitoring self-discharge phenomena of electrochemical cells, comprising the steps of: a) providing a plurality of electrochemical cells, wherein each cell has a first dimension and a second dimension, extending respectively along a first direction and a second direction orthogonal to one another, greater than a third dimension extending along a third direction orthogonal to the first direction and the second direction, wherein each cell comprises a casing and a plurality of layers arranged inside the casing, wherein the layers comprise at least one first electrode layer, at least one second electrode layer and at least one first separator layer interposed between the first electrode layer and the second electrode layer; b) arranging the cells so that a straight line extending along the third direction intersects the cells; c) compressing the cells along the third direction; d) measuring a voltage of each cell of the plurality of cells to detect whether a self-discharge value of said cell is greater than a predetermined threshold, wherein step c) is prior to or at least partially simultaneous with step d), and step d) is prior to a step of assembling the cells into one or more batteries.