Core-Shell Battery Binder to Prevent Separator Pore Blockage
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Solution Overview
Problem
The existing method of bonding a separator to an electrode sheet in batteries results in the binder swelling in the electrolyte, blocking the pores and impeding lithium ion movement, leading to poor cycle performance.
Innovation Solution
A binder with a core-shell structure is used, where the core is a crystalline polymer and the shell is an amorphous polymer, allowing bonding before electrolyte injection, with low swelling in the electrolyte, preventing pore blockage and enhancing ion mobility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the binder is used to bond the separator to the electrode sheet by swelling in the electrolyte, then the bonding strength is improved, but the pores of the separator are blocked and lithium ion movement is impeded
Solution Approach 1:
The binder is segmented into multiple functional components: a crystalline polymer matrix providing structural integrity and low swelling, an amorphous polymer providing adhesion, and an inorganic filler enhancing thermal stability. This segmentation allows each component to perform its specific function without causing pore blockage.
Solution Approach 2:
The binder is formulated as a composite material combining crystalline polymer, amorphous polymer, and inorganic filler in specific ratios. This composite structure provides both strong bonding capability and controlled swelling characteristics, preventing pore blockage while maintaining adhesion.
2Strength
If the binder swells greatly in the electrolyte to generate adhesion, then the bonding effect is improved, but the cycle performance deteriorates due to pore blockage
Solution Approach 1:
Different regions of the binder have different properties: the crystalline polymer regions provide low swelling and structural stability, while the amorphous polymer regions provide adhesion. This local differentiation allows the binder to achieve both strong bonding and maintained porosity during cycling.
Solution Approach 2:
The binder's swelling parameters are precisely controlled by adjusting the crystalline-to-amorphous polymer ratio and inorganic filler content. This parameter optimization ensures sufficient adhesion while limiting swelling-induced pore blockage, thereby improving cycle performance.
3Ease of manufacture
If a conventional binder is used for bonding, then the bonding process is simple, but the internal resistance increases due to blocked pores
Solution Approach 1:
The binder is pre-formulated with the optimal composite composition and uniform dispersion of all components before application. This preliminary preparation ensures that the binder maintains its functional properties during application and curing, achieving both ease of manufacture and low internal resistance.
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
This approach improves battery cycle performance by maintaining open pores and ensuring effective ion movement between electrode sheets, reducing internal resistance and misalignment issues.
Implementation Method 1
the amorphous polymer of the shell is melted, and the battery separator may be separately bonded with the positive electrode sheet and the negative electrode sheet
Implementation Method 2
the binder is used to swell in the electrolyte to generate adhesion, to bond the separator with the electrode sheet
Data Source
AI summary
A binder includes a bonding material particle. The bonding material particle includes a core and a shell. The core includes a crystalline polymer. The shell wraps at least a part of an outer surface of the core, and the shell includes an amorphous polymer.