Lithium-ion Battery Tab Notch for Stress Reduction
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Solution Overview
Problem
Lithium-ion batteries face issues with lithium metal deposition on the electrode surface during charge/discharge cycles, leading to short-circuits, material loss, and reduced battery life, especially when the filling density of the active material is high or during high-rate charge/discharge, causing stress and bending in the tab sections.
Innovation Solution
The battery design incorporates a notch in the active material layer at the end of the tab section, where the tab and active material layer interface, to reduce stress and prevent bending, thereby suppressing lithium metal deposition by maintaining a consistent interelectrode distance and reducing electric resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the filling density of the active material layer is increased to enhance volume energy density, then the amount of active material contained in the battery case is increased, but stress is generated within the tab section during charge/discharge cycles, causing bending or creases
Solution Approach 1:
The active material layer is segmented by introducing a notch that divides it into multiple regions. This segmentation allows different portions of the active material layer to expand and contract independently during charge/discharge cycles, reducing stress concentration at the tab section boundary and preventing bending or creases while maintaining high filling density
Solution Approach 2:
The notch creates a local structural modification at the boundary between the tab section and active material layer. This local quality change allows the region near the tab to have different mechanical properties, accommodating stress differences between the rigid tab section and the expanding/contracting active material, thereby preventing structural failure
2Speed
If high-rate charge/discharge is performed to improve power output, then the charging and discharging speed is increased, but stress generated within the tab section causes bending or creases leading to electrode curving
Solution Approach 1:
The notch segments the active material layer to allow independent movement of different regions during high-rate charge/discharge. This segmentation reduces stress transmission to the tab section, preventing bending or creases even under rapid expansion and contraction conditions
Solution Approach 2:
The notch structure introduces dynamic flexibility to the electrode assembly, allowing the active material layer to adapt its configuration during high-rate charge/discharge cycles. This dynamic adjustment prevents stress accumulation that would otherwise cause structural failure
3Use of energy by moving object
If the tab section expands and contracts due to charge/discharge cycles, then the active material layer undergoes volume changes, but stress generated causes bending or creases in the tab section
Solution Approach 1:
The notch segments the active material layer into distinct regions that can expand and contract independently during charge/discharge cycles. This segmentation prevents uniform stress distribution that would cause bending, allowing the tab section to maintain its flat shape while the battery undergoes normal charge/discharge operations
Data Source
AI summary
A battery includes an electrode assembly having a positive electrode and a negative electrode. The positive electrode includes a positive electrode substrate, a positive electrode active material layer formed on the surface of the positive electrode substrate, and a positive tab section having a substrate-exposed portion in which the positive electrode active material layer is not formed on the surface. The positive electrode active material layer has a notch in the end of the positive electrode active material layer. The outer edge of the notch encloses an end of a boundary where the positive tab section and the positive electrode active material layer come into contact.