PVDF Membrane Adhesive Bonding Without Collapse
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Solution Overview
Problem
Microporous membranes used in electrochemical cells, such as batteries and supercapacitors, are fragile and prone to holes or tears, leading to electrode shorts and reduced performance due to blockages that prevent ion passage, rendering the devices unusable.
Innovation Solution
A method involving an adhesive mixture of a solvent capable of dissolving PVDF, but with a non-solvent having higher surface energy to prevent membrane collapse, is used to bond PVDF microporous films to electrodes, creating a tacky surface for adherence without damage, allowing for the construction of multiple-layered electrochemical cells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a solvent capable of dissolving PVDF is used to bond the microporous film to the electrode, then the adhesive bonding strength is improved, but the microporous membrane may collapse due to excessive solvent penetration
Solution Approach 1:
The patent changes the chemical composition parameters of the adhesive by incorporating a non-solvent component with high surface energy into the solvent system. This parameter modification allows the adhesive to provide sufficient bonding strength while preventing excessive solvent penetration that would collapse the microporous structure. The non-solvent component adjusts the overall solvent power and evaporation characteristics of the adhesive mixture.
Solution Approach 2:
The patent creates a composite adhesive system combining a PVDF-solvent component with a high surface energy non-solvent component. This composite adhesive formulation achieves both strong bonding to the PVDF membrane and electrode while maintaining the membrane's microporous structure, as the non-solvent portion does not dissolve the PVDF but provides adhesion through high surface energy interactions.
2Stability of the object's composition
If the adhesive contains only solvent to dissolve PVDF, then the membrane becomes tacky for bonding, but the microporous structure collapses due to excessive dissolution
Solution Approach 1:
The patent modifies the adhesive composition parameters by adding a non-solvent component that adjusts the dissolution equilibrium. The non-solvent reduces the overall solvent power of the mixture, preventing excessive dissolution of the PVDF membrane while maintaining sufficient tackiness for bonding. The specific ratio of solvent to non-solvent is controlled to achieve the optimal balance between membrane activation and structural preservation.
Solution Approach 2:
The non-solvent component acts as an intermediary substance that mediates between the solvent's dissolving action and the membrane's structural integrity. It allows controlled interaction between the solvent and PVDF membrane, enabling tackiness development while preventing complete dissolution or collapse of the microporous structure through its high surface energy and non-dissolving characteristics.
3Shape
If a high surface energy non-solvent is added to the adhesive, then the membrane structure is preserved, but the bonding strength may be reduced
Solution Approach 1:
The patent formulates a composite adhesive where the solvent component provides strong chemical bonding to PVDF through dissolution, while the non-solvent component with high surface energy provides secondary adhesion mechanisms and preserves membrane structure. The synergistic combination of these two components in specific ratios achieves both strong overall bonding and membrane structure preservation, with each component compensating for the other's limitations.
Solution Approach 2:
The patent optimizes the concentration parameters of both solvent and non-solvent components in the adhesive formulation. By carefully controlling the ratio and amounts of each component, the adhesive achieves sufficient bonding strength through the solvent-PVDF interaction while the non-solvent's high surface energy provides additional adhesion contribution that compensates for any reduction in bonding strength, simultaneously preserving the membrane's microporous structure.
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 adhesive solution effectively bonds PVDF membranes to electrodes without collapsing the membrane, enhancing ion conduction and cell performance, and can be used for repairing pinholes and filling voids, resulting in improved electrochemical cell stability and performance.
Implementation Method 1
an adhesive comprising: a solvent capable of dissolving said PVDF of said microporous film
Implementation Method 2
a non-solvent having a surface energy higher than a surface energy of said solvent
Implementation Method 3
causes the PVDF membrane to become tacky and adhere to an electrode
Implementation Method 4
said adhesive is applied to said first electrode; and said adhesive is allowed to dry
Data Source
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AI summary
An electrochemical cell may have a PVDF microporous membrane that may be adhesively bonded to electrodes. The adhesive may be a mixture of a solvent and non-solvent that may cause the PVDF membrane to become tacky and adhere to an electrode without collapsing. An adhesively bonded cell may be constructed using multiple layers of adhesively bonded membranes and electrodes. In some embodiments, the adhesive solution may be used as a sizing to prepare electrodes for bonding.