Low-Melting Polyimide Electrode Binder Without Polar Solvents
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Solution Overview
Problem
The handling of polyimides as binder resins for electrodes in lithium ion secondary batteries is challenging due to low solvent solubility, requiring high-temperature imidization reactions that can adversely affect electrode materials and produce water, and the use of polar solvents is not preferable.
Innovation Solution
A polyimide-based resin with a melting point of 300°C or lower is used, allowing for excellent adhesion to a current collector at relatively low temperatures without the need for polar solvents or imidization reactions, achieved by incorporating an aliphatic component in the tetracarboxylic acid or diamine component and using a non-polar solvent.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If polyimide is used as a binder resin, then adhesion strength and toughness are improved, but handling difficulty increases due to low solvent solubility
Solution Approach 1:
The invention changes the chemical structure parameters of polyimide by introducing flexible spacers (alkylene groups with 3-20 carbon atoms) between aromatic rings, which modifies the polymer chain flexibility and solubility characteristics while maintaining adhesion strength and toughness properties
Solution Approach 2:
The invention creates a composite polyimide structure combining rigid aromatic rings for strength with flexible aliphatic spacers for solubility and processability, achieving both good adhesion and easy handling
2Strength
If high-temperature imidization reaction is used to form polyimide, then adhesion to current collector is improved, but electrode materials and solid electrolyte are adversely affected
Solution Approach 1:
The invention changes the imidization temperature parameter from conventional high temperatures (above 300°C) to lower temperatures (200-300°C) by using pre-formed polyimide resin, which maintains adhesion strength while preventing damage to electrode materials and solid electrolyte
Solution Approach 2:
The invention performs the imidization reaction in advance during resin synthesis to form ready-to-use polyimide binder, eliminating the need for subsequent high-temperature imidization treatment that would damage sensitive electrode materials
3Strength
If imidization reaction is performed to convert polyamic acid to polyimide, then binder strength is improved, but water is produced which adversely affects electrode materials
Solution Approach 1:
The invention performs the imidization reaction in advance during resin synthesis under controlled conditions, converting polyamic acid to polyimide before electrode fabrication, thereby eliminating subsequent water production that would damage electrode materials and solid electrolyte
Solution Approach 2:
The invention extracts and removes the harmful byproduct (water) from the electrode fabrication process by completing the imidization reaction beforehand, preventing water-related damage to sensitive components
4Ease of operation
If polar solvent is used to dissolve polyimide, then processability is improved, but environmental and safety concerns increase
Solution Approach 1:
The invention changes the solvent polarity parameter by using non-polar or low-polarity solvents instead of conventional polar solvents like NMP, achieving satisfactory processability while reducing environmental and safety concerns
Solution Approach 2:
The invention utilizes the thermal softening and melting properties of polyimide at elevated temperatures to achieve binder function and adhesion without requiring extensive solvent dissolution, thereby reducing dependence on problematic polar 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
This approach enables the formation of electrodes with strong adhesion to the current collector at lower temperatures, preventing adverse effects on electrode materials and electrolytes, and ensuring sufficient binding force without using polar solvents or producing water during the imidization process.
Implementation Method 1
a polyimide-based resin having a melting point of 300°C or lower
Data Source
AI summary
The present invention relates to a binder resin for electrodes consisting of a polyimide-based resin having a melting point of 300°C or lower. The present invention also relates to an electrode mixture paste comprising the binder resin for electrodes, an electrode active material, and a solvent; and an electrode comprising an electrode mixture layer comprising the binder resin for electrodes and an electrode active material; and a method for producing the electrode.