Composite PTFE Binder for Uniform Conductive Electrode Mixing
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Solution Overview
Problem
Current binder materials for energy storage devices face challenges such as poor distribution of conductive additives in fluoropolymer matrices, high dielectric constants, safety, environmental, and cost issues with solvents like NMP, and the inability of PTFE to form a homogenous mixture with conductive additives due to its high melting point and insolubility in NMP.
Innovation Solution
Development of composite binder materials comprising polytetrafluoroethylene (PTFE) integrated with a low-melting point thermoplastic and a conductive additive, which aids in adhesion to current collectors and ensures uniform distribution of conductive properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If PTFE is used as binder material, then chemical stability and electrochemical inertness are improved, but distribution of conductive additives and ability to form homogenous mixture deteriorate due to high melting point and insolubility in NMP
Solution Approach 1:
The patent introduces a low-melting-point fluoropolymer as an intermediary substance that bridges PTFE and conductive additives. This mediator enables the conductive additives to distribute uniformly throughout the PTFE matrix by providing a processing temperature window where the low-melting-point fluoropolymer is molten and can facilitate mixing, while PTFE remains solid and provides structural stability.
Solution Approach 2:
The patent creates a composite binder system combining PTFE with a low-melting-point fluoropolymer. This composite material leverages the chemical stability and electrochemical inertness of PTFE while incorporating the processability and melting characteristics of the low-melting-point fluoropolymer, thereby achieving both homogeneity and reliability.
2Reliability
If PTFE is used as binder material, then chemical stability is improved, but adhesion to current collector deteriorates due to high melting point preventing flow and mechanical bonding
Solution Approach 1:
The patent changes the temperature parameter during processing to below the melting point of PTFE but above the melting point of the low-melting-point fluoropolymer. This parameter change allows the low-melting-point fluoropolymer to flow and form mechanical bonds with the current collector, while PTFE remains solid and maintains chemical stability.
3Ease of manufacture
If PVdF is used as binder material, then processability is improved, but dielectric constant increases leading to safety and environmental concerns
Solution Approach 1:
The patent changes the chemical composition parameter by replacing PVdF with PTFE combined with a low-melting-point fluoropolymer. This substitution maintains processability through the melting behavior of the low-melting-point fluoropolymer while reducing the dielectric constant, as fluoropolymers generally exhibit lower dielectric constants compared to PVdF.
4Loss of substance
If dry blending PTFE with conductive additive is performed, then solvent use is reduced, but distribution uniformity deteriorates due to high melting point of PTFE
Solution Approach 1:
The patent changes the temperature parameter during mixing to a range where the low-melting-point fluoropolymer is molten but PTFE remains solid. This temperature parameter change enables the molten low-melting-point fluoropolymer to act as a matrix that facilitates uniform distribution of conductive additives, while avoiding the need for solvents.
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 composite binder materials provide excellent adhesion strength, uniformity, and tensile strength in electrode mixtures, overcoming the limitations of existing binder materials by enabling efficient conductive pathways and improved processing temperatures.
Implementation Method 1
a low-melting point thermoplastic... PTFE will not flow through or over any surface and cannot form a mechanical bond... the temperatures needed to melt PTFE even if it could be made to flow exceeds the upper temperature capabilities
Implementation Method 2
both fluoropolymers are insulators. A conductive additive must be added to the PTFE or PVdF if there is to be current flow in a cathode
Data Source
AI summary
Composite binder materials for energy storage applications are disclosed. The composite binder materials include a fluoropolymer, such as polytetrafluoroethylene (PTFE), integrated with a conductive additive and a low-melting point thermoplastic. Methods of making the composite binder materials are also disclosed. The methods include providing an emulsion of the fluoropolymer, mixing the low-melting point thermoplastic and the particulate conductive additive into the emulsion of the fluoropolymer to form a mixture, and coagulating the mixture to produce a coagulum including the composite binder material. The disclosure also provides a binder powder for an electrochemical device capable of providing an electrode mixture sheet having excellent uniformity of tensile strength. The disclosure relates to a binder powder for an electrochemical device, containing a non-fibrillated fibrillatable resin and a thermoplastic polymer.