Shell-Coated Electrode Material for Stable Aqueous Battery Slurries
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Solution Overview
Problem
Aqueous binders used in positive electrodes are prone to oxidation, leading to uneven distribution and weakened binding, resulting in decreased electrode capacity and degraded cycle characteristics, while conventional non-aqueous binders like PVDF require organic solvents, increasing environmental impact.
Innovation Solution
The use of a non-aqueous binder that covers the entire surface of the electrode active material in a shell shape, dispersed in an aqueous solvent, ensuring uniform distribution and reducing solvent use.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If an aqueous binder is used for a positive electrode, then environmental load is reduced by avoiding organic solvents, but the binder is oxidized and deteriorated under positive electrode environment
Solution Approach 1:
The binder system is segmented into two distinct components: a water-soluble polymer component (providing aqueous compatibility and low environmental load) and a fluorinated polymer component (providing oxidation resistance). This segmentation allows each component to perform its specialized function, resolving the contradiction between environmental friendliness and chemical stability.
Solution Approach 2:
The invention uses a composite binder material comprising both a water-soluble polymer and a fluorinated polymer. This composite structure combines the advantages of both materials: the water-soluble polymer enables aqueous processing and reduces environmental impact, while the fluorinated polymer provides the necessary oxidation resistance for positive electrode environments, thus resolving the contradiction between environmental load and binder stability.
2Object-affected harmful factors
If a nonaqueous binder is dispersed in an aqueous solvent, then environmental load is reduced, but the binder is unevenly distributed and binding is weakened
Solution Approach 1:
The binder is segmented into two functional components with complementary properties: the water-soluble polymer ensures homogeneous distribution in the aqueous slurry, while the fluorinated polymer provides the required oxidation resistance. This segmentation resolves the contradiction by allowing the water-soluble component to achieve uniform distribution without compromising the oxidation resistance provided by the fluorinated component.
Solution Approach 2:
The water-soluble polymer acts as an intermediary that facilitates uniform dispersion of the binder system in the aqueous solvent. This intermediary component enables the fluorinated polymer (which would otherwise be difficult to disperse uniformly in water) to be evenly distributed, thus resolving the contradiction between environmental friendliness and distribution uniformity.
3Strength
If PVDF is used as a binder, then mechanical strength and adhesiveness are improved, but organic solvent use increases environmental load
Solution Approach 1:
The invention creates a composite binder system that replaces the organic solvent-dependent PVDF with a combination of water-soluble polymer and fluorinated polymer. This composite maintains the mechanical strength and adhesiveness properties of conventional PVDF binders while eliminating the need for organic solvents, thus resolving the contradiction between strength performance and environmental load.
Solution Approach 2:
The invention changes the fundamental parameter of solvent type from organic to aqueous, while maintaining the performance characteristics of the binder through the use of fluorinated polymer components. This parameter change allows the system to achieve both reduced environmental load and maintained mechanical strength, resolving the contradiction between these two requirements.
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 enhances binding between active materials and the current collector, maintaining electrode capacity and improving cycle characteristics while minimizing solvent use.
Implementation Method 1
the entire surface of the electrode active material is covered in a shell shape with a nonaqueous binder
Implementation Method 2
dispersed in an aqueous solvent
Data Source
Figure 1~2
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Figure 5~7
AI summary
An electrode material 1 for a secondary battery, which is capable of suppressing a decrease in an electrode capacity and having excellent cycle characteristics, includes an electrode active material 10, and the entire surface or part of the surface of the electrode active material 10 is covered in a shell shape with a nonaqueous binder 20.