Secondary Battery Cushioning Material for Bending Resistance
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Solution Overview
Problem
Portable electronic devices face challenges with high-capacity secondary batteries due to their large size and weight, and when using film as an exterior body, they are prone to damage from external forces, such as bending, which can lead to stress concentration and generation of wrinkles and cracks.
Innovation Solution
Incorporating a cushioning material with a higher elastic modulus than the electrode group or stack, placed peripherally around the electrode group, to alleviate stress concentration and prevent damage when the battery is bent, allowing for a more flexible and durable design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If a film is used as an exterior body to reduce weight and thickness, then the secondary battery becomes lighter and thinner, but the strength and resistance to external force decrease
Solution Approach 1:
The exterior body is constructed as a composite structure comprising an outer film layer and an inner cushioning material layer. The film provides lightweight and thin characteristics, while the cushioning material (having higher elastic modulus than the electrode group) provides mechanical strength and stress absorption. This composite configuration resolves the contradiction by combining materials with complementary properties to achieve both weight reduction and strength maintenance.
2Length of moving object
If a film is used as an exterior body to achieve thin design, then the secondary battery thickness is reduced, but the resistance to bending and external force decreases
Solution Approach 1:
The cushioning material is pre-positioned within the exterior body structure, between the film and the electrode group, to provide beforehand protection against bending forces. When external bending force is applied, the cushioning material (with higher elastic modulus than the electrode group) absorbs and distributes the stress before it can reach the electrode group, preventing damage and maintaining reliability in thin battery designs.
3Quantity of substance
If the electrode group is made thicker to increase capacity, then the battery capacity increases, but stress concentration and wrinkle generation increase when bent
Solution Approach 1:
The cushioning material acts as an intermediary layer between the thick electrode group and the exterior film. When the battery is bent, this intermediary layer absorbs and distributes the mechanical stress, preventing stress concentration at the electrode-film interface that would otherwise lead to wrinkle generation and potential damage. This allows thicker electrode groups for higher capacity without proportionally increasing stress-related harmful effects.
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
The cushioning material reduces stress concentration and prevents wrinkles and cracks, enabling secondary batteries to maintain their shape and internal structure integrity even when bent, enhancing their resistance to repeated bending and flexibility.
Implementation Method 1
a cushioning material is provided in a peripheral region sandwiched by an exterior body... the cushioning material is thicker than the current collector... a material of the cushioning material is preferably an elastic material
Data Source
AI summary
In the case where a film having lower strength than a metal can is used as an exterior body of a secondary battery, a current collector provided in a region surrounded by the exterior body, an active material layer provided on a surface of the current collector, or the like might be damaged when force is externally applied to the secondary battery. A secondary battery resistant to external force is provided. A cushioning material is provided in a region sandwiched by an exterior body of the secondary battery. Specifically, the cushioning material is provided on the periphery of an electrode group including a positive electrode current collector, a positive electrode active material layer formed on at least one surface of the positive electrode current collector, a separator, a negative electrode current collector, and a negative electrode active material layer formed on at least one surface of the negative electrode current collector.