Li-Ion Electrode Binder Copolymers for Adhesion Without High Viscosity
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Solution Overview
Problem
Existing fluoropolymers used as binders for lithium-ion battery electrodes face a challenge in achieving high adhesion to the current collector while maintaining low viscosity in the electrode-forming formulation to facilitate easy handling and coating processes.
Innovation Solution
Development of vinylidene fluoride copolymers containing specific vinyl and carboxyl group-containing monomers, randomly distributed to maintain low viscosity and enhance adhesion, using a polymerization process that ensures uniform distribution of these monomers within the polymer backbone.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the fluoropolymer molecular weight is increased to improve adhesion and mechanical properties, then the adhesion of electrodes to current collector is improved, but the viscosity of electrode-forming formulation increases making handling and coating difficult
Solution Approach 1:
The patent changes the chemical composition parameters of the fluoropolymer by incorporating specific comonomers (carboxyl-containing vinyl monomers at 0.1-5 mol% and hydroxyl-containing vinyl monomers at 0.1-5 mol%) to achieve high adhesion without requiring high molecular weight, thus avoiding increased viscosity. This compositional parameter change allows decoupling adhesion improvement from viscosity increase
Solution Approach 2:
The patent creates a composite polymer structure by combining VDF units with specific functional monomers (carboxyl-containing and hydroxyl-containing vinyl monomers) to achieve synergistic effects where the functional groups provide adhesion enhancement without the need for high polymer molecular weight, thereby maintaining low formulation viscosity
2Strength
If the fluoropolymer molecular weight is increased to improve mechanical properties, then the mechanical strength of electrodes is improved, but the viscosity of electrode-forming formulation increases making handling difficult
Solution Approach 1:
The patent changes the chemical composition parameters by incorporating specific comonomers to achieve improved mechanical properties through enhanced interfacial adhesion rather than increased molecular weight, thus avoiding the viscosity penalty associated with high molecular weight polymers
Data Source
AI summary
The present invention pertains to vinylidene fluoride copolymers comprising recurring units derived from hydrophilic monomers and to their use as binder for electrodes in Li-ion batteries.