Thin Secondary Battery Separator Anisotropic Expansion Wrinkle Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
High capacity secondary batteries face challenges in miniaturization and weight reduction due to container size and weight constraints, with issues of wrinkle formation on sheet-shaped separators affecting charge-discharge behavior and heat radiation properties during electrolyte penetration.
Innovation Solution
A method involving a sheet-shaped separator with expansion anisotropy, where the electrolyte solution penetrates without fixing the separator's maximum expanding direction, maintaining the direction parallel to the penetration, to prevent wrinkle formation and ensure tight sealing, thereby enhancing heat radiation and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a sheet-shaped separator subjected to stretch processing is used, then heat radiation properties are improved, but wrinkles are formed on the separator causing deterioration in charge-discharge behavior
Solution Approach 1:
The patent applies parameter changes by controlling the stretching conditions of the separator to achieve anisotropic expansion. Specifically, the separator is stretched in one direction more than in the perpendicular direction, creating different expansion rates along different axes. This controlled anisotropy allows the separator to expand preferentially in the direction that enhances heat radiation while minimizing wrinkle formation in directions that would compromise charge-discharge performance.
Solution Approach 2:
The patent employs asymmetry by creating a separator with directionally dependent expansion properties. The stretching process induces asymmetric structural characteristics where the separator expands differently along orthogonal directions. This asymmetric expansion behavior enables optimized heat radiation in the direction of greater expansion while maintaining dimensional stability in the direction of lesser expansion, thereby preventing wrinkle formation that would deteriorate charge-discharge behavior.
2Reliability
If the separator is fixed during electrolyte penetration, then wrinkle formation is prevented, but expansion anisotropy cannot be utilized for heat radiation optimization
Solution Approach 1:
The patent applies dynamics by making the separator's expansion behavior conditional rather than fixed. During electrolyte penetration, the separator is allowed to expand dynamically in response to moisture absorption, but this expansion is guided by the pre-established anisotropic structure. The separator freely expands in the direction that maximizes heat radiation while the anisotropic constraints prevent excessive expansion and wrinkle formation in perpendicular directions, thus simultaneously achieving wrinkle prevention and heat radiation optimization.
3Quantity of substance
If a block-shaped container main body is used to contain multiple unit batteries, then high capacity is achieved, but the container size and weight increase
Solution Approach 1:
The patent applies flexible shells and thin films by replacing rigid block-shaped containers with flexible laminate film wrappers. Each unit battery is individually wrapped in a thin, flexible laminate film that provides necessary containment and protection. This flexible wrapping eliminates the need for heavy rigid containers and internal partition walls, significantly reducing the overall container main body weight while maintaining the ability to contain multiple unit batteries in various configurations.
Solution Approach 2:
The patent employs segmentation by treating each unit battery as an independent, self-contained module wrapped in its own flexible laminate film. This segmentation allows each unit to be optimized independently and enables flexible arrangement of multiple units without requiring a monolithic rigid container. The segmented approach with flexible individual wrappers reduces overall system weight compared to a single large rigid container with internal partitions.
4Temperature
If the separator expands anisotropically during electrolyte penetration, then heat radiation is enhanced, but thickness fluctuation and poor appearance occur
Solution Approach 1:
The patent applies parameter changes by precisely controlling the stretching parameters of the separator during manufacturing. By adjusting the stretching ratio, temperature, and duration, the separator acquires a controlled anisotropic structure with predictable expansion characteristics. This controlled parameter setting ensures that during electrolyte penetration, the separator expands primarily in the direction that enhances heat radiation while maintaining sufficient dimensional stability to prevent excessive thickness fluctuation and preserve acceptable appearance.
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 approach results in a high capacity, thin-type secondary battery with improved heat radiation properties, reduced thickness fluctuations, and increased design freedom, while minimizing facility investment costs and maintaining quality stability.
Implementation Method 1
a sheet-shaped separator subjected to stretch processing... penetration of an electrolytic solution to wet the separator... expansion anisotropy during penetration of an electrolytic solution
Implementation Method 2
wrinkles are formed due to effects of expansion anisotropy during thermal shrinkage of the separator through high temperature drying for water removal
Data Source
AI summary
To provide a high capacity thin-type secondary battery suitably formed into a module and having no thickness fluctuation, excellent quality stability, and excellent heat radiation properties, by using a sheet-like separator having expansion anisotropy due to penetration of an electrolytic solution. A method of producing a thin-type secondary battery includes the steps of: sandwiching a sheet-like separator having expansion anisotropy due to penetration of an electrolytic solution, by a sheet-like electrode pair; inserting the separator sandwiched by the electrode pair and injecting the electrolytic solution, into a thin-type outer wrapper having an opened portion; penetrating the electrolytic solution into the separator without fixing motion of the separator in a maximum expanding direction and in a state where the maximum expanding direction of the separator and a penetrating direction of the electrolytic solution are substantially parallel to each other; and sealing the opened portion into a tightly sealed state.