Separator Stress Control for Battery Cycle Stability
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Solution Overview
Problem
Non-aqueous electrolyte secondary battery cells, particularly those used in vehicles, experience temporary deterioration in output power immediately after charge/discharge cycles due to stress from electrode swelling and shrinking, which is exacerbated by high-current cycles within a narrow State Of Charge range.
Innovation Solution
The battery cells are designed with a separator configured to maintain a specific stress range of 0.5 MPa to 14 MPa at a compressed depth corresponding to 5% of the negative electrode active material layer thickness, reducing compressive stress on electrodes and preventing non-uniformity in the ion conduction path.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If charge/discharge cycles are repeated at high current within narrow SOC range, then power output requirements are met, but temporary deterioration occurs due to electrode swelling and shrinking stress
Solution Approach 1:
The patent applies parameter changes by controlling the stress on the separator within a specific range (0.5 MPa to 14 MPa) during charge/discharge cycles. This stress parameter control prevents excessive compression that would cause pore closure and ion conductivity loss, thereby reducing temporary deterioration while maintaining power output requirements for high-current applications
Solution Approach 2:
The patent implements beforehand cushioning by pre-configuring the separator with specific mechanical properties and stress tolerance before operation. The separator is designed to withstand swelling and shrinking stresses during high-current cycles, cushioning against the harmful effects of electrode expansion and contraction before they can cause damage
2Reliability
If separator compression resistance is increased to prevent clogging, then ion conductivity is maintained, but electrode deformation and micro-short circuits increase
Solution Approach 1:
The patent changes the parameter of separator stress from a single property (compression resistance) to a controlled range (0.5-14 MPa). This allows the separator to have sufficient resistance to prevent clogging while maintaining flexibility to accommodate electrode swelling and shrinking, thereby preventing both ion conductivity loss and electrode deformation
Solution Approach 2:
The separator acts as an intermediary between the electrodes, mediating the interaction between ion transport requirements and electrode mechanical changes. By controlling separator stress within the specified range, it facilitates ion conductivity while simultaneously protecting electrodes from excessive compression and deformation
3Adaptability or versatility
If high-current cycles are performed within narrow SOC range, then vehicle application requirements are met, but temporary deterioration is exacerbated
Solution Approach 1:
The patent applies parameter changes by establishing a specific stress range (0.5-14 MPa) that enables the battery to withstand high-current cycling within narrow SOC ranges typical of vehicle applications. This parameter control maintains cycle stability while meeting the adaptability requirements for automotive use
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 configuration effectively suppresses temporary deterioration and micro-short circuits, maintaining performance and reducing the incidence of wrinkles and deformation in electrodes, thereby enhancing the battery's cycle stability and output power.
Implementation Method 1
a stress that is caused at a specific compressed depth in the separator, which corresponds to 5% of the thickness of the negative electrode active material layer, is 0.5 MPa or more and 14 MPa or less
Data Source
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AI summary
Provided are an electric storage device that reduces temporary deterioration, and an electric storage apparatus that includes a plurality of such electric storage devices. An electric storage device includes: a container; an electrode assembly contained in the container, the electrode assembly including a positive electrode having a positive electrode substrate and a positive electrode active material layer that is formed on the positive electrode substrate and contains a positive electrode active material, a negative electrode having a negative electrode substrate and a negative electrode active material layer that is formed on the negative electrode substrate and contains a negative electrode active material, and a separator interposed between the positive and negative electrodes; and an electrolyte contained in the container, wherein the separator is configured such that a stress caused at a specific compressed depth in the separator, which corresponds to 5% of the thickness of the negative electrode active material layer, is 0.5 MPa or more and 14 MPa or less. An electric storage apparatus includes a plurality of electric storage devices described above.