PVDF Copolymer Composition for Stable Battery Binder Dispersion
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Solution Overview
Problem
Vinylidene fluoride copolymers used as binders in non-aqueous electrolyte secondary batteries act as insulators, reducing ion conductivity and requiring methods to improve their dispersibility and stability in dispersion media with low relative dielectric constants.
Innovation Solution
A vinylidene fluoride copolymer composition with specific physical properties, including a melting point of 140°C or lower and endothermic peaks with an enthalpy of fusion of 2 J/g or more, is developed for stable dispersion in a medium with a relative dielectric constant of 15 or less, using a method involving emulsion preparation and surfactant addition to enhance dispersibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If vinylidene fluoride copolymer is used as a binder in non-aqueous electrolyte secondary batteries, then binding performance between current collector and electrode active material is improved, but ion conductivity is reduced due to insulating properties
Solution Approach 1:
The patent introduces a solid electrolyte as an intermediary substance between the insulating vinylidene fluoride copolymer binder and the ion conduction path. The solid electrolyte particles are dispersed in the binder, creating conductive pathways that mediate ion transport while the binder maintains its binding function, thus resolving the contradiction between binding performance and ion conductivity
Solution Approach 2:
The patent creates a composite material system combining the vinylidene fluoride copolymer binder with solid electrolyte particles. This composite structure allows the insulating binder to coexist with ion-conducting solid electrolyte, achieving both binding performance and maintained ion conductivity through the synergistic combination of materials
2Stability of the object's composition
If vinylidene fluoride copolymer is dispersed in dispersion medium with low relative dielectric constant, then dispersibility is improved, but long-term stability and precipitation resistance are reduced
Solution Approach 1:
The patent modifies physical parameters of the vinylidene fluoride copolymer, specifically controlling the content of vinylidene fluoride units and adjusting molecular weight, to achieve optimal balance between dispersibility in low dielectric constant media and long-term stability. By precisely controlling composition parameters, the copolymer maintains stable dispersion without premature precipitation
Solution Approach 2:
The patent introduces local quality variations by incorporating fluorinated alkyl vinyl compound units at specific positions within the copolymer chain. These localized structural modifications create regions with different polarities and interaction characteristics, enabling the copolymer to maintain both good dispersibility and long-term stability in low dielectric constant dispersion media
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 composition ensures uniform dispersion and long-term stability of the vinylidene fluoride copolymer in the medium, preventing precipitation and improving the performance of electrode and electrolyte layers in non-aqueous electrolyte secondary batteries.
Implementation Method 1
the vinylidene fluoride copolymer composition has a melting point of 140° C. or lower
Implementation Method 2
the vinylidene fluoride copolymer composition has endothermic peaks having an amount of enthalpy of fusion (ΔHm) of 2 J/g or more
Data Source
AI summary
A vinylidene fluoride copolymer composition having stable dispersibility in a dispersion medium over a long period of time, the composition having a melting temperature of 140° C. or lower, a reversing heat flow of the composition has endothermic peaks having an amount of enthalpy of fusion of 2 J/g or more, and an absolute value of a difference between a temperature showing a largest endothermic peak among the endothermic peaks and the melting temperature of the composition is 10° C. or lower. When a dispersion containing butyl butyrate and the vinylidene fluoride copolymer composition (vinylidene fluoride content rate of 10 mass %) is left to stand for 20 hours, a content rate of the vinylidene fluoride copolymer composition in an upper 20 vol % of the dispersion after the dispersion is left to stand is 4.0 mass % or more and 10 mass % or less.