Raspberry Core-Shell Binder for Separator Adhesion in Battery Cells
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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, primarily attributed to the crystallinity of conventional polyvinylidene fluoride binders.
Innovation Solution
A core-shell structured binder is developed, comprising a polyacrylate polymer core and a polyvinylidene fluoride polymer shell with reduced crystallinity, featuring a raspberry-shaped structure to enhance adhesion performance by exposing the core layer and increasing the specific surface area, thereby improving the adhesion force between the separator and electrode plates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polyvinylidene fluoride polymer is used as binder, then chemical stability and electrochemical performance are improved, but adhesion force between separator and electrode plate deteriorates due to high crystallinity
Solution Approach 1:
The patent uses a core-shell structured binder composed of polyacrylate polymer core and polyvinylidene fluoride polymer shell. This composite structure combines the chemical stability and electrochemical performance of PVDF with the adhesive properties of polyacrylate, resolving the contradiction between reliability and adhesion strength.
Solution Approach 2:
The binder exhibits different properties in different regions: the core layer provides adhesion functionality while the shell layer provides chemical stability. This local differentiation allows the binder to simultaneously achieve good adhesion force and electrochemical performance.
2Reliability
If shell layer structure completely encapsulates core layer structure, then chemical stability is improved, but adhesion performance deteriorates due to reduced core layer exposure
Solution Approach 1:
The shell layer structure does not completely encapsulate the core layer structure, but rather partially covers it. This partial action allows the core layer to remain exposed and maintain adhesion performance while still providing chemical stability through the shell layer.
Solution Approach 2:
The binder is divided into discrete shell structures distributed on the core layer surface, rather than forming a continuous encapsulating layer. This segmentation maintains both chemical stability from the shell and adhesion from the exposed core regions.
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 improved adhesion force reduces the likelihood of gaps between electrode plates and separators, enhancing the cycling performance and kinetic properties of battery cells, including better shape retention and increased service life.
Implementation Method 1
Polyvinylidene fluoride is a homopolymer with a crystallinity of about 50%, resulting in insufficient adhesion force. Therefore, in this application, the polyvinylidene fluoride polymer is used to encapsulate the polyacrylate 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, and adhesion performance of 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 a surface of the core layer structure, where the core layer structure includes a polyacrylate polymer, and the shell layer structure includes a polyvinylidene fluoride polymer.