Wound Battery Electrode Structure to Prevent Separator Shorting
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Solution Overview
Problem
Current secondary batteries face challenges in achieving higher reliability due to stress on the separator caused by expansion and contraction during charging and discharging, leading to potential short circuits.
Innovation Solution
The design incorporates a wound electrode body with a specific configuration where the inner periphery side negative electrode active material layer is not provided in the region overlapping with the inner periphery side positive electrode active material layer, allowing the negative electrode to bend towards the central axis, thereby reducing stress on the separator and preventing short circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the inner periphery side negative electrode active material layer is provided in the region overlapping with the inner periphery side positive electrode active material layer, then the battery capacity is increased, but the separator stress increases leading to potential short circuits
Solution Approach 1:
The patent extracts the problematic overlap region by intentionally leaving the inner peripheral surface of the negative electrode current collector uncovered with active material in the region overlapping with the positive electrode active material layer. This removes the source of stress concentration while preserving active material in other regions to maintain battery capacity.
Solution Approach 2:
The patent applies local quality by creating a non-uniform distribution of negative electrode active material, specifically excluding it from the inner peripheral region that overlaps with the positive electrode, while maintaining active material coverage in other regions. This localized modification reduces separator stress at the critical overlap zone without sacrificing overall battery capacity.
2Reliability
If the negative electrode is constrained to prevent bending, then the separator is protected from stress, but the electrode structure becomes more complex
Solution Approach 1:
Instead of adding constraints to prevent bending, the patent extracts the problematic element (negative electrode active material) from the stress-prone region. This allows the negative electrode to bend naturally toward the central axis during charging-discharging cycles without compromising separator integrity, thereby avoiding additional structural complexity.
3Reliability
If the electrode active material layers are arranged to allow negative electrode bending, then the separator stress is reduced, but the manufacturing precision requirements increase
Solution Approach 1:
The patent applies local quality by selectively modifying the negative electrode active material distribution only in the inner peripheral overlap region, while maintaining standard construction in other areas. This localized approach simplifies manufacturing compared to requiring precise positioning of all layers, as it only necessitates controlling the absence of material in a specific zone.
Data Source
AI summary
A positive electrode includes: a positive electrode current collector including an inner peripheral surface and an outer peripheral surface; an inner periphery side positive electrode active material layer; and an outer periphery side positive electrode active material layer. A negative electrode includes: a negative electrode current collector including an inner peripheral surface and an outer peripheral surface; an inner periphery side negative electrode active material layer; and an outer periphery side negative electrode active material layer. An innermost wind portion of the negative electrode is located on an inner side relative to an innermost wind portion of the positive electrode. An inner periphery side edge of the outer periphery side negative electrode active material layer is located closer to a central axis of a wound electrode body than an inner periphery side edge of the inner periphery side negative electrode active material layer.