Button Cell Coil Electrode Thermal Fuse Safety
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Solution Overview
Problem
Button cells without a flange are less resilient to axial mechanical loads and prone to leaks due to volume changes during charging and discharging of lithium-ion systems, and they face safety risks from overcharging and short circuits.
Innovation Solution
A button cell design featuring two metallic housing halves separated by an electrically insulating seal, with a flat base and cover area, and a coil arrangement of electrodes and separators, including metallic conductors and a thermal fuse to prevent overcharging, and a non-positive connection between housing halves to prevent flanging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If button cells are designed without a flange (non-positive connection between housing halves), then ease of manufacture is improved, but axial mechanical strength deteriorates making them less resilient to axial loads during charging and discharging
Solution Approach 1:
The housing is divided into two separate half-housings that are joined without a flange connection. This segmentation allows for simpler manufacturing of individual components while the overall structure maintains adequate mechanical strength through the sealing arrangement and internal support elements.
Solution Approach 2:
Instead of relying on axial flange connection for strength, the design transitions to a sealing arrangement where the sealing element and internal structural support provide the necessary mechanical resilience in the axial direction, effectively moving the load-bearing function to different structural elements.
2Device complexity
If button cells use a non-positive connection between housing halves, then device complexity is reduced, but reliability deteriorates due to increased susceptibility to leaks under axial mechanical loads
Solution Approach 1:
A sealing element is introduced as an intermediary component between the two half-housings. This sealing element prevents direct contact and potential leakage paths while maintaining the non-positive connection design, thereby preserving both simplicity and reliability.
Solution Approach 2:
The sealing element and internal structural arrangement are designed to preemptively accommodate axial mechanical loads that occur during charging and discharging, preventing leaks before they can occur by providing a compliant sealing interface.
3Use of energy by moving object
If lithium-ion cells are overcharged beyond 4.2V, then energy capacity is increased, but safety deteriorates due to lithium deposition, gassing, and potential explosive combustion
Solution Approach 1:
A control system with voltage monitoring is implemented to detect the charging voltage level and provide feedback to stop or modulate charging when the 4.2V threshold is reached, preventing overcharging and associated safety hazards while maximizing safe energy capacity.
Solution Approach 2:
Safety mechanisms are built into the cell design that preemptively counteract overcharging effects, such as protective coatings on electrodes, pressure relief valves, and thermal management systems that activate before dangerous conditions develop, allowing higher energy density while maintaining safety.
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
Enhances axial stability and safety by preventing leaks and overcharging-induced damage, ensuring reliable operation and preventing explosive combustion.
Implementation Method 1
a button cell (200) according to one of the preceding claims, characterized in that at least one of the conductors (211, 212) is provided with a thermal fuse (213)
Data Source
Figure 1(A)~1(B)
Figure 2
AI summary
A button cell comprises two housing halves: a metallic cell cup and a metallic cell lid, separated by an electrically insulating seal. These halves form a housing with a flat base and a parallel flat lid. The cell also includes an electrode-separator assembly with at least one positive and at least one negative electrode within the housing, as well as metallic contacts that electrically connect the positive and negative electrodes to each of the housing halves. The cell cup and the cell lid each have a flat base, a cylindrical outer shell, a rim, and a cut edge. The cell lid is inserted into the cell cup so that the outer shells of the cell cup and cell lid overlap.The electrode-separator assembly is in the form of a spiral winding, the ends of which face the flat bottom and top sections. At least one of the arresters is equipped with a thermal fuse. The arresters are metal foils. At least one section of the arrester(s) in the bottom or top section of the housing lies flat against the inside of the housing half(s). The button cell includes a separate insulating material that prevents direct electrical contact between the ends of the winding and the at least one section.