Battery Electrode-Separator Laminate for Thermal Shrinkage Stability
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Solution Overview
Problem
Conventional laminates for secondary batteries fail to achieve a balance of high adhesion between the electrode and separator, leading to high internal resistance and instability.
Innovation Solution
A laminate for a secondary battery is designed with a specific relationship between shear peel strength and maximum heat shrinkage force of the separator, ensuring A > B in a temperature range of 25°C to α°C, where A is the shear peel strength and B is the maximum heat shrinkage force, using an adhesive material that includes water-insoluble and water-soluble polymers to enhance adhesion and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional adhesive materials are used to bond the electrode and separator, then the production process is simple, but the adhesion strength is insufficient leading to high internal resistance and instability
Solution Approach 1:
The patent changes the chemical composition parameters of the adhesive material by incorporating specific polymers (polyacrylic acid, polyacrylamide, carboxymethyl cellulose, or starch) with defined molecular characteristics. This parameter change enables the adhesive to achieve both high adhesion strength and battery stability simultaneously, resolving the contradiction between strength and reliability.
Solution Approach 2:
The patent creates a composite adhesive system by combining water-soluble polymers with specific functional groups (carboxyl, hydroxyl, or amino groups) that can interact with both the electrode and separator surfaces. This composite approach enhances interfacial bonding while maintaining structural integrity, thereby achieving both strong adhesion and long-term stability.
2Stability of the object's composition
If the separator heat shrinkage force is increased to improve thermal stability, then the separator maintains its structure better at high temperature, but the adhesion between electrode and separator deteriorates
Solution Approach 1:
The patent applies local quality by designing the adhesive material with specific functional groups concentrated at the bonding interface between electrode and separator. These localized functional groups (carboxyl, hydroxyl, or amino groups) provide strong chemical interaction at the interface while allowing the separator bulk to maintain its thermal stability through its inherent polyolefin structure.
Solution Approach 2:
The adhesive material acts as an intermediary substance between the electrode and separator. It contains polymer chains with functional groups that can form hydrogen bonds or other interactions with both surfaces, mediating the interface while the separator's polyolefin base material maintains thermal shrinkage resistance. This intermediary role allows both thermal stability and adhesion to coexist.
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 laminate achieves excellent adhesiveness between the electrode and separator, resulting in a secondary battery with low internal resistance and enhanced stability, inhibiting thermal runaway and maintaining stability during temperature changes.
Implementation Method 1
an adhesive material, wherein, when a value measured for shear peel strength between the electrode and the separator with varying temperature is taken to be A
Implementation Method 2
a value of maximum heat shrinkage force for the separator determined by thermomechanical analysis is taken to be B
Data Source
AI summary
A laminate for a secondary battery includes an electrode and a separator that are stacked via an adhesive material. For this laminate, when a value measured for shear peel strength between the electrode and the separator with varying temperature is taken to be A (mN/mm2), a value of maximum heat shrinkage force for the separator determined by thermomechanical analysis is taken to be B (mN/mm2), and a temperature at which heat shrinkage force for the separator determined by thermomechanical analysis decreases to a value (mN/mm2) that is 20% higher than a value (mN/mm2) of heat shrinkage force at 30° C. is taken to be a heat shrinkage end temperature α (° C.), A has a value satisfying A>B in a temperature range of not lower than 25° C. and not higher than the heat shrinkage end temperature α° C.