Flexible Secondary Battery with Patterned Active Material
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Solution Overview
Problem
The challenge lies in developing a thin and lightweight secondary battery that can withstand bending without cracking, as traditional metal cans are heavy and difficult to manufacture, and laminate films with lower strength may damage the active material layers when bent, leading to positional shifts and stress issues with electrodes.
Innovation Solution
A secondary battery design featuring a current collector with active material layers formed in a pattern, such as stripes or meandering shapes, using laser processing to remove parts of the active material layer, allowing for flexibility and stress relief, and incorporating a meandering current collector shape to maintain structural integrity during bending.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a metal can is used as an exterior body, then the secondary battery has high strength and reliability, but the weight increases and thickness cannot be reduced
Solution Approach 1:
The patent replaces the rigid metal can with a flexible laminate film comprising multiple layers (resin film, aluminum foil, and heat-seal resin). This thin-film structure significantly reduces weight and enables flexible battery designs while maintaining sufficient mechanical strength through the composite laminate structure. The film can be molded into thin profiles that metal cans cannot achieve.
Solution Approach 2:
The exterior body uses a composite laminate structure combining different materials (resin, aluminum foil, heat-seal resin) to achieve optimal balance between strength, weight, and flexibility. Each layer contributes specific properties: the resin provides structural integrity, the aluminum foil provides barrier properties and strength, and the heat-seal resin enables sealing. This composite approach resolves the contradiction between strength and weight.
2Weight of moving object
If a laminate film is used as an exterior body, then the secondary battery becomes thinner and lighter, but the active material layer may be damaged when force is externally applied
Solution Approach 1:
The patent incorporates a buffer layer or cushioning structure between the exterior film and the active material layer to absorb and distribute external forces before they reach the fragile active material. This pre-cushioning prevents direct transmission of impact forces that could cause cracking or damage to the active material layers.
Solution Approach 2:
The multi-layer laminate film structure itself acts as a protective composite material system where each layer contributes to force distribution and protection of the internal components. The combination of rigid and flexible layers creates a protective envelope that shields the active material from external damage while maintaining the thin and light profile.
3Adaptability or versatility
If electrodes are bent with different curvatures, then the flexible secondary battery can be formed, but the end portion of the electrode far from the curvature center shifts or extends
Solution Approach 1:
The patent divides the electrode into multiple segments or sections along its length, with each segment having optimized curvature characteristics. This segmentation allows different portions of the electrode to bend at different rates, preventing excessive displacement at the ends while maintaining overall flexibility. The electrode can be designed with varying thickness or stiffness along its length to control bending behavior.
Solution Approach 2:
The patent introduces additional design dimensions such as varying electrode thickness, adding support layers, or creating three-dimensional electrode structures that can accommodate bending stresses. By transitioning from a simple flat electrode to a multi-dimensional structure with controlled geometry, the electrode can flex without excessive end displacement, maintaining manufacturing precision while achieving flexibility.
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
This design enables a flexible and reliable secondary battery that can be bent without cracking, maintaining electrode position and reducing stress, thus suitable for use in wearable electronic devices and vehicles.
Implementation Method 1
part of the active material layer is removed by laser light irradiation
Data Source
AI summary
An electronic device having a novel structure, specifically, an electronic device having a novel structure that can be changed into various appearances is provided. Specifically, after an active material layer is formed on one or both surfaces of a current collector, the active material layer in a bent region is partly removed. The removed region of the active material layer can be in a linear shape, a dot shape, or a matrix shape, for example. After the active material layer is formed on one or both surfaces of the current collector, laser processing for removing part of the active material layer in an irradiation region is performed using laser light or the like. On the region where the surface of the current collector is exposed, the active material layer is not provided, and this region is a region that does not function as a battery. Owing to this region, a secondary battery with a wide movable region can be achieved.