Spiral-Wound Electrode Assembly with Extended Trailing Edge
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Solution Overview
Problem
Existing electrochemical cells with spiral-wound electrode assemblies face challenges in maximizing the utilization of active materials while maintaining low impedance over the discharge life, particularly due to limitations in the interfacial anode-to-cathode ratio and surface area issues, which affect performance in demanding applications like digital cameras.
Innovation Solution
The design features a spiral-wound electrode assembly with an interfacial anode-to-cathode ratio of less than 1.2, where the second electrode's trailing edge extends past the first electrode's trailing edge, and includes a tab affixed to the second electrode positioned inward, optimizing the use of active materials and reducing impedance growth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the interfacial anode-to-cathode ratio is increased to maximize utilization of active materials, then the capacity increases, but the impedance growth accelerates due to reduced surface area of electrical connection
Solution Approach 1:
The patent transitions from a conventional planar tab connection to a three-dimensional spiral-wound structure with extended trailing edges. This dimensional change allows the electrode assembly to maintain a smaller interfacial anode-to-cathode ratio while preserving adequate electrical connection surface area through the spiral geometry, thereby resolving the contradiction between active material utilization and impedance stability.
Solution Approach 2:
The spiral-wound configuration nests multiple layers of electrodes within each other, creating a compact structure where the trailing edges extend outward. This nesting allows the electrode assembly to achieve high active material utilization in the inner regions while maintaining electrical connection integrity at the outer trailing edges, simultaneously addressing both capacity and impedance concerns.
2Reliability
If the interfacial anode-to-cathode ratio is decreased to maintain low impedance, then the electrical connection surface area is preserved, but the utilization of active materials is reduced
Solution Approach 1:
The electrode assembly is segmented into distinct functional zones: the inner spiral-wound region optimized for active material utilization with reduced anode-to-cathode ratio, and the outer trailing edge region optimized for electrical connection with extended surface area. This segmentation allows each zone to fulfill its specific function without compromising the other, resolving the contradiction between material utilization and impedance stability.
Solution Approach 2:
Different regions of the electrode assembly have different local characteristics: the inner regions have a smaller anode-to-cathode ratio to maximize active material utilization, while the outer trailing edges have extended surface area to maintain low impedance. This local differentiation of properties allows the system to simultaneously achieve high capacity and low impedance, resolving the apparent contradiction.
3Ease of manufacture
If traditional spiral-wound configuration is used with equal electrode lengths, then the manufacturing is simplified, but the impedance growth occurs due to insufficient electrical connection surface area
Solution Approach 1:
The patent introduces asymmetry by extending the trailing edges of the electrodes beyond the wound portion of the spiral assembly. This asymmetric configuration creates additional surface area for electrical connection at the trailing edges without significantly complicating the manufacturing process, as it builds upon the conventional spiral-wound structure. The asymmetry resolves the contradiction by providing the needed connection surface area while maintaining manufacturing feasibility.
Data Source
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AI summary
A spiral-wound electrode assembly an electrochemical cell with the spiral-wound electrode assembly, and a method of manufacturing an electrochemical cell with the spiral-wound electrode assembly are disclosed. The spiral-wound electrode assembly (400) has a first electrode (410) that has a first electrode active material, a leading edge and a trailing edge (440). The assembly has a second electrode (420) that includes a second electrode active material, a leading edge and a trailing edge (450). A separator (not shown) is located between the first electrode and the second electrode. The electrode assembly has an interfacial anode-to-cathode ratio of less than about 1.2. The first electrode, second electrode, and separator are wound so that the first electrode forms a layer at the outermost radius of the electrode assembly and so that the trailing edge of the second electrode extends past the trailing edge of the first electrode by a distance X.