Core-Shell Binder for Separator-Electrode Adhesion in Batteries
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Solution Overview
Problem
Battery cells face issues with gaps forming between electrode plates and separators, leading to deteriorated cycling performance due to insufficient adhesion force, particularly with polyvinylidene fluoride polymers having low crystallinity.
Innovation Solution
A core-shell structured binder is developed, comprising a polyvinylidene fluoride polymer core and a polyacrylate polymer shell, with a raspberry-shaped structure to enhance adhesion, where the polyacrylate polymer encapsulates the polyvinylidene fluoride polymer to improve crystallinity and adhesion performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If polyvinylidene fluoride polymer is used as binder, then adhesion force between separator and electrode plate is improved, but crystallinity is insufficient resulting in poor adhesion performance
Solution Approach 1:
The patent uses a core-shell structured binder composed of polyvinylidene fluoride polymer core and polyacrylate polymer shell. The core provides adhesion force while the shell improves crystallinity, creating a composite material that simultaneously achieves both adhesion performance and structural stability.
Solution Approach 2:
The binder adopts a core-shell structure where the polyacrylate polymer shell encapsulates the polyvinylidene fluoride polymer core. This nested structure allows the inner core to provide adhesion while the outer shell provides crystallinity, with both components working together in a hierarchical arrangement.
2Strength
If polyvinylidene fluoride polymer with high crystallinity is used, then adhesion performance is improved, but the polymer becomes too rigid reducing flexibility
Solution Approach 1:
The core-shell binder structure creates different local properties: the core layer provides adhesion strength while the shell layer provides flexibility. This spatial differentiation of material properties allows the binder to simultaneously achieve rigidity where needed and flexibility where needed.
Solution Approach 2:
By combining polyvinylidene fluoride polymer (providing adhesion) with polyacrylate polymer (providing flexibility), the composite binder achieves a balance between strength and adaptability that neither material could achieve alone.
3Strength
If shell layer completely encapsulates core layer, then adhesion is improved, but specific surface area is reduced
Solution Approach 1:
The shell layer partially encapsulates the core layer rather than completely covering it, leaving portions of the core surface exposed. This partial encapsulation maintains sufficient adhesion while preserving more surface area compared to complete encapsulation.
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 binder significantly increases the adhesion force between the separator and electrode plates, improving cycling performance and maintaining battery hardness, thereby enhancing kinetic and cycling performance.
Implementation Method 1
the polyacrylate polymer is used to encapsulate the polyvinylidene fluoride polymer to obtain the core-shell-structured binder, so that the crystallinity of the polyvinylidene fluoride polymer in the core-shell-structured binder is improved
Data Source
AI summary
This application relates to the field of battery technologies, and in particular, to a binder and a preparation method thereof, and a separator, electrode assembly, battery cell, battery, and electric apparatus containing such binder. The binder includes a core layer structure and a shell layer structure provided on surface of the core layer structure, where the core layer structure includes a polyvinylidene fluoride polymer, and the shell layer structure includes a polyacrylate polymer. Polyvinylidene fluoride is a homopolymer with a crystallinity of about 50%, resulting in insufficient adhesion force. Therefore, in this application, the polyacrylate polymer is used to encapsulate the polyvinylidene fluoride polymer to obtain a core-shell-structured binder, so that the crystallinity of the polyvinylidene fluoride polymer in the core-shell-structured binder is improved, and adhesion performance of the core-shell-structured binder is improved, thereby increasing adhesion force between a separator and an electrode plate via the binder.