Polymer Alloy Binder for Positive Electrodes
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Solution Overview
Problem
Current binder materials for positive electrodes in electric storage devices lack simultaneous excellence in ion conductivity, oxidation resistance, and adhesion, leading to compromised charge-discharge characteristics and mechanical durability.
Innovation Solution
A binder composition comprising polymer alloy particles synthesized from a combination of vinylidene fluoride, ethylene tetrafluoride, or propylene hexafluoride-based polymer A and an unsaturated carboxylic acid ester-based polymer B, with a specific particle size range of 50 to 400 nm, enhancing ion conductivity, oxidation resistance, and adhesion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If PVDF (fluorine-containing organic polymer) is used as electrode binder, then ion conductivity and oxidation resistance are improved, but adhesion deteriorates
Solution Approach 1:
The patent uses a composite binder system comprising PVDF (fluorine-containing polymer) combined with polyacrylonitrile or polyacrylamide. This composite approach allows the PVDF component to provide ion conductivity and oxidation resistance, while the polyacrylonitrile or polyacrylamide component provides enhanced adhesion to the active material particles and current collector, thereby resolving the contradiction between electrochemical performance and mechanical adhesion.
Solution Approach 2:
The patent optimizes the composition ratios and molecular weight parameters of the binder components. Specifically, it controls the weight ratio of PVDF to polyacrylonitrile or polyacrylamide, and adjusts the viscosity and molecular weight of the binder solution to achieve optimal adhesion while maintaining ion conductivity and oxidation resistance.
2Strength
If rubber-based polymer is combined with PVDF to improve adhesion, then adhesion is improved, but ion conductivity and oxidation resistance deteriorate
Solution Approach 1:
The patent replaces rubber-based polymers with polyacrylonitrile or polyacrylamide, which have different chemical properties. These polymers provide adhesion enhancement without the negative impact on ion conductivity and oxidation resistance that rubber-based polymers cause. The specific choice of polyacrylonitrile or polyacrylamide with controlled molecular weight and viscosity ensures compatibility with the electrochemical requirements.
3Reliability
If fluorine-containing organic polymer is used, then oxidation resistance is improved, but adhesion to active material particles and current collector deteriorates
Solution Approach 1:
The patent creates a composite binder where PVDF provides oxidation resistance while polyacrylonitrile or polyacrylamide provides adhesion to both active material particles and current collector. The synergistic combination allows each component to fulfill its primary function without compromising the other.
Solution Approach 2:
The binder composition is designed with different components serving different local functions: PVDF primarily provides oxidation resistance and ion conductivity, while polyacrylonitrile or polyacrylamide primarily provides adhesion. This functional differentiation allows optimization of each property independently through material selection and ratio control.
Data Source
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AI summary
The present invention relates to a binder composition for the positive electrode of an electric storage device, comprising: polymer alloy particles composed of a polymer A having a recurring unit derived from at least one selected from the group consisting of vinylidene fluoride, ethylene tetrafluoride and propylene hexafluoride and a polymer B having a recurring unit derived from an unsaturated carboxylic acid ester; and water, wherein the average particle diameter of the polymer alloy particles is 50 to 400 nm, the polymer alloy particles are synthesized by absorbing a monomer for constituting the polymer B to the polymer A and polymerizing the monomer for constituting the polymer B to synthesize the polymer B, and the monomer for constituting the polymer B is an unsaturated carboxylic acid ester, or a mixture of an unsaturated carboxylic acid ester and at least one monomer selected from the group consisting of an α,β-unsaturated nitrile compound, an unsaturated carboxylic acid, a conjugated diene compound, styrene, α-methylstyrene, p-methylstyrene, vinyltoluene, chlorostyrene, divinylbenzene, a carboxylic vinyl ester and an acid anhydride of an ethylenically unsaturated dicarboxylic acid.