High-Molecular-Weight PTFE Binder for Solvent-Free Electrode Sheets
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Solution Overview
Problem
Existing polytetrafluoroethylene (PTFE) binders for electrochemical devices struggle to form electrode mixture sheets with high strength, and they often require organic solvents, which increase costs and complexity.
Innovation Solution
A PTFE with a number average molecular weight of 3.0 × 10^6 or more is used as an electrochemical device binder, which has a water content of 0.050% by mass or less and primary particles with an average aspect ratio of 2.0 or lower, enabling the formation of high-strength electrode mixture sheets without organic solvents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional PTFE binders are used for electrochemical devices, then the binding function is provided, but the electrode mixture sheet strength is insufficient
Solution Approach 1:
The patent applies parameter changes by specifying a number average molecular weight of 3.0 × 10^6 or more for the PTFE binder, which is a significant increase from conventional PTFE binders. This molecular weight parameter change results in improved electrode mixture sheet strength while maintaining adequate binding function, directly resolving the technical contradiction between strength and reliability
2Ease of manufacture
If organic solvents are used in PTFE binder formulation, then processing is facilitated, but production costs and complexity increase
Solution Approach 1:
The patent extracts and eliminates organic solvents from the PTFE binder formulation, achieving a solvent-free binder system. This is accomplished by optimizing the PTFE particle characteristics (number average molecular weight of 3.0 × 10^6 or more, aspect ratio of 2.0 or lower) to provide adequate processing and binding performance without requiring organic solvents, thereby reducing production costs and process complexity
3Strength
If PTFE with high molecular weight is used, then electrode mixture sheet strength is improved, but water content control becomes more critical
Solution Approach 1:
The patent applies parameter changes by simultaneously optimizing multiple PTFE characteristics: number average molecular weight (3.0 × 10^6 or more), aspect ratio (2.0 or lower), and water content (0.050% by mass or less). This multi-parameter optimization approach enables the use of high molecular weight PTFE for improved strength while maintaining strict water content control to prevent processing issues
Solution Approach 2:
The patent applies preliminary action by pre-drying the PTFE binder to reduce water content to 0.050% by mass or less before use in electrode mixture preparation. This preliminary water removal action prevents water-related processing problems that could arise from using high molecular weight PTFE, thereby enabling the strength benefits to be realized without manufacturing precision issues
Data Source
AI summary
The disclosure aims to provide a polytetrafluoroethylene for use in electrochemical device binders which enables formation of an electrode mixture sheet with high strength, and an electrochemical device binder, an electrode mixture, an electrode, and a secondary battery. Provided is a polytetrafluoroethylene for use in electrochemical device binders, the polytetrafluoroethylene having a number average molecular weight of 3.0 × 106 or more.