Flexible Battery Electrodes Using Composite Binder Systems
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Solution Overview
Problem
Current methods for preparing flexible lithium-ion battery electrodes using aqueous suspensions often result in inhomogeneous, brittle, and non-flexible films due to the use of toxic solvents and inadequate binder systems, leading to poor encapsulation and mechanical strength.
Innovation Solution
A composition comprising at least partially hydrolysed polyvinyl acetate, polyalkylene glycol, and a conductive component, with specific mass ratios, in an aqueous or alcohol-based solvent system, which allows for the formation of homogeneous, flexible, and crack-free films without the need for pressing, using a method that involves forming a liquid suspension and applying it to a substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If aqueous suspensions with conventional binders (cellulose derivatives, PVAc, PEG-based copolymers) are used, then environmental friendliness is improved, but film flexibility and mechanical strength deteriorate
Solution Approach 1:
The invention uses a composite binder system combining at least partially hydrolysed polyvinyl acetate (5-50 wt%) with polyalkylene glycol (50-95 wt%). This composite approach leverages the adhesive properties of hydrolysed PVAc and the flexibility-enhancing properties of polyalkylene glycol to achieve both environmental friendliness and superior mechanical performance. The synergistic combination resolves the contradiction by providing a binder system that is both eco-friendly (aqueous-based) and mechanically robust.
Solution Approach 2:
The invention specifically controls the hydrolysis degree of polyvinyl acetate (5-50 wt%) and the molecular mass of polyalkylene glycol (Mn < 9000 g/mol) to optimize film properties. By adjusting these parameters, the binder system achieves optimal balance between adhesion, flexibility, and mechanical strength while remaining environmentally friendly. The controlled hydrolysis degree prevents excessive brittleness while maintaining binding efficiency.
2Object-affected harmful factors
If aqueous suspensions with conventional binders are used, then toxicity is reduced, but film homogeneity and encapsulation quality worsen
Solution Approach 1:
The invention optimizes the hydrolysis degree parameter of polyvinyl acetate (5-50 wt%) to achieve optimal dispersion and encapsulation. This parameter control ensures homogeneous distribution of active material particles while maintaining aqueous-based environmental friendliness. The specific hydrolysis range prevents particle aggregation and ensures uniform film formation without requiring toxic organic solvents.
Solution Approach 2:
The composite binder system of hydrolysed PVAc and polyalkylene glycol works synergistically to achieve homogeneous film structure. The PVAc component provides structured encapsulation while polyalkylene glycol ensures uniform distribution, resulting in homogeneous films with excellent encapsulation quality using only aqueous solvents.
3Device complexity
If conventional binder systems are used without pressing, then process simplicity is improved, but film density and mechanical strength deteriorate
Solution Approach 1:
The binder system exhibits self-organizing and self-binding properties that enable film formation with adequate density and strength without requiring external pressing. The hydrolysed PVAc and polyalkylene glycol components work together to create internal structural coherence, allowing the film to self-densify during drying. This eliminates the need for complex pressing equipment while maintaining mechanical integrity.
Solution Approach 2:
The composite binder system provides inherent structural support and binding strength that compensates for the absence of pressing. The synergistic combination of PVAc and polyalkylene glycol creates a robust matrix that maintains film density and mechanical strength through its own internal properties rather than external compression.
4Ease of operation
If cellulose derivative binders are used, then aqueous processing is enabled, but film flexibility and crack resistance worsen
Solution Approach 1:
The invention extracts and replaces the problematic cellulose derivative binder with a superior alternative system based on hydrolysed PVAc and polyalkylene glycol. This extraction eliminates the brittleness and poor flexibility issues inherent in cellulose-based binders while maintaining aqueous processing capability. The new binder system is specifically selected to provide both environmental friendliness and mechanical flexibility.
Solution Approach 2:
The composite binder system of hydrolysed PVAc and polyalkylene glycol provides both aqueous processability and superior flexibility. The polyalkylene glycol component specifically addresses the flexibility deficiency of conventional aqueous binders, while the hydrolysed PVAc maintains water-based processing. Together they create a crack-resistant, flexible film structure.
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 solution enables the creation of flexible, homogeneous, and mechanically resistant films with good electrochemical performance, capable of being used in batteries without a substrate, offering improved rate capability and conductivity while being environmentally friendly and cost-effective.
Implementation Method 1
an at least partially hydrolysed polyvinyl acetate component... wherein the mass ratio between the at least partially hydrolysed polyvinyl acetate component and the positive or negative electrode active component equal at least 0.12 and at most 0.30
Implementation Method 2
A polyalkylene glycol component having a number average molecular mass Mn lower than 9000 g/mol... wherein the mass ratio between the polyalkylene glycol component and the positive or negative electrode active component equal at least 0.012 and at most 0.10
Implementation Method 3
in an aqueous or alcohol-based solvent system, which allows for the formation of homogeneous, flexible, and crack-free films
Data Source
AI summary
A composition comprises: an at least partially hydrolysed polyvinyl acetate component having an hydrolysation degree of at least 5%; a polyalkylene glycol component having a number average molecular mass Mn lower than 9000 g/mol and consisting of one or more substances selected from the group consisting of polyethylene glycol, polypropylene glycol, copolymers of ethylene glycol and propylene glycol, and their derivatives; a positive or negative electrode active component; and a conductive component; wherein the mass ratio between the at least partially hydrolysed polyvinyl acetate component and the positive or negative electrode active component equals at least 0.12 and at most 0.30, and wherein the mass ratio between the polyalkylene glycol component and the positive or negative electrode active component equals at least 0.012 and at most 0.10.