Cross-linked Binder for Lithium Battery Electrodes
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Solution Overview
Problem
Conventional binders for lithium batteries, such as PVdF and SBR/CMC, face challenges in maintaining mechanical properties and adhesion when used with electrode active materials that undergo significant volume changes, leading to issues like bubble formation and curved electrode surfaces.
Innovation Solution
A cross-linked binder composed of polyimide, poly(acrylic acid), and polyvinyl alcohol, cross-linked via ester bonds, is developed to enhance mechanical properties and adhesion, suppressing bubble formation and improving the flatness and efficiency of electrode plates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional binders (PVdF, SBR/CMC) are used with electrode active materials undergoing large volume change, then adhesion and mechanical properties deteriorate, but using alternative binders (polyimide, polyvinyl alcohol) causes bubble formation and curved electrode surfaces
Solution Approach 1:
The invention uses a composite binder system combining polyimide and polyvinyl alcohol in specific weight ratios (95:5 to 50:50). This composite approach leverages the strong adhesion of polyimide while using polyvinyl alcohol as a foam suppressant, resolving the contradiction between achieving good adhesion and preventing bubble formation that occurs when using either binder alone.
Solution Approach 2:
The invention optimizes the weight ratio parameters of polyimide and polyvinyl alcohol to achieve the desired balance. By adjusting these compositional parameters within specific ranges, the binder system maintains excellent adhesion while effectively suppressing bubble formation and electrode curvature.
2Strength
If polyvinyl alcohol is used as binder, then adhesion improves, but bubbles are formed during electrode slurry preparation causing curved surfaces
Solution Approach 1:
The invention uses polyimide as an intermediary substance that modifies the behavior of polyvinyl alcohol. The polyimide component suppresses the foam-forming tendency of polyvinyl alcohol while maintaining the adhesion benefits, allowing polyvinyl alcohol to function as an effective binder without causing electrode curvature.
Solution Approach 2:
By creating a composite binder system where polyimide and polyvinyl alcohol work together in specific ratios, the invention achieves both good adhesion and electrode flatness, eliminating the harmful effects of using polyvinyl alcohol alone.
3Reliability
If binder is used to maintain mechanical properties during volume change, then adhesion improves, but bubble formation occurs reducing electrode quality
Solution Approach 1:
The composite binder system combines the mechanical property maintenance capability of polyimide with the adhesion benefits of polyvinyl alcohol, while the specific composition ratios ensure bubble suppression, achieving reliable mechanical performance without harmful bubble formation.
Solution Approach 2:
By optimizing the weight ratio parameters of the binder components, the invention achieves the right balance between maintaining mechanical properties during volume change and suppressing bubble formation, with polyimide content ranging from 50-95 wt%.
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 new binder improves the initial efficiency, Coulombic efficiency, discharge capacity, and capacity retention of lithium batteries by maintaining electrode flatness and stability, while reducing bubble formation and enhancing adhesion.
Implementation Method 1
the cross-linked product is cross-linked by at least two ester bonds or at least one ester bond and at least one amide bond
Implementation Method 2
the cross-linked product is cross-linked by at least two ester bonds or at least one ester bond and at least one amide bond
Implementation Method 3
bubbles are formed by polyvinyl alcohol during preparation of an electrode slurry... a binder capable of suppressing formation of bubbles
Implementation Method 4
heat-treating the mixture to prepare a cross-linked product and prepare the binder
Data Source
AI summary
A binder includes a cross-linked product of at least a first polymer, a second polymer, and a third polymer, wherein the cross-linked product is cross-linked by at least two ester bonds; the first polymer includes polyimide, polyamic acid, a copolymer thereof, or a combination thereof, wherein the first polymer includes a structural unit including an alkali metal and a structural unit including at least one hydroxyl functional group; the second polymer includes poly(acrylic acid), poly(methacrylic acid), a copolymer thereof, or a combination thereof; and the third polymer includes polyvinyl alcohol, polyacrylamide, polymethacrylamide, a copolymer thereof, or a combination thereof.