Core-Shell Polymer Adhesive for Li-Ion Battery Separator Bonding
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Solution Overview
Problem
Conventional lithium ion secondary batteries experience decreased adhesion properties between the separator and electrodes in electrolytic solutions, leading to low-temperature output issues and reduced battery performance.
Innovation Solution
A core-shell structured particulate polymer adhesive is used, where the core portion swells significantly in the electrolytic solution and the shell portion provides additional adhesion, enhancing the bonding between the separator and electrodes, while non-conductive fibers improve mechanical strength and ion diffusivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional adhesive is used in lithium ion secondary battery, then the battery can be assembled, but the adhesion property between separator and electrode decreases in electrolytic solution, leading to low-temperature output problems
Solution Approach 1:
The adhesive uses a polymer with specific swelling degree parameters (5-30 times in electrolytic solution) and controlled glass transition temperature (0-150°C) to maintain adhesion stability. By optimizing these physical parameters, the adhesive prevents electrode separation in electrolytic solution while maintaining low-temperature output performance.
Solution Approach 2:
The adhesive is formulated as a composite system combining polymer matrix with specific particulate fillers having core-shell structure. This composite structure provides both adhesion functionality and mechanical strength, resolving the contradiction between maintaining bond strength and ensuring low-temperature electrical output.
2Reliability
If polymer with high swelling degree is used to improve adhesion, then adhesion property improves, but internal resistance increases, reducing low-temperature output
Solution Approach 1:
The polymer's swelling degree is precisely controlled within 5-30 times range, and glass transition temperature is set between 0-150°C. This parameter optimization ensures sufficient adhesion while preventing excessive swelling that would increase internal resistance and reduce low-temperature power output.
Solution Approach 2:
The adhesive exhibits different properties in different states: in dry state it provides mechanical bonding, while in electrolytic solution the polymer swells to provide adhesion and ion conductivity. This local quality differentiation allows the adhesive to satisfy both adhesion and low-temperature output requirements simultaneously.
3Reliability
If adhesive layer is added to improve bonding, then adhesion property improves, but device complexity increases
Solution Approach 1:
The adhesive layer performs multiple functions simultaneously: it bonds the separator to the electrode, provides ion conductivity through polymer swelling, and maintains structural stability. This multi-functionality reduces the need for additional components, thereby not increasing device complexity despite improving adhesion.
Solution Approach 2:
The adhesive is applied as a thin layer with controlled thickness and composition, optimizing the balance between adhesion performance and structural complexity. The polymer's swelling behavior is tuned to provide necessary functionality without creating excessive bulk or complexity in the battery 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 solution results in improved adhesion, low-temperature output, and high-temperature cycle properties of lithium ion secondary batteries by maintaining a stable internal resistance and preventing electrode separation, thus enhancing overall battery performance.
Implementation Method 1
the core portion is formed from a polymer having a swelling degree in an electrolytic solution of 5 times or more and 30 times or less
Data Source
AI summary
An adhesive for a lithium ion secondary battery, for bonding members for constituting a lithium ion secondary battery, the adhesive including a particulate polymer, wherein the particulate polymer has a core-shell structure including a core portion and a shell portion that partially covers an outer surface of the core portion, the core portion is formed from a polymer having a swelling degree in an electrolytic solution of 5 times or more and 30 times or less, and the shell portion is formed from a polymer having a swelling degree in an electrolytic solution of more than 1 time and 4 times or less.