Influence of molecular weight of polyvinylidene fluoride on the flow behavior of slurry and electrochemical properties of coated electrode

In capacitive deionization (CDI) technology, PVDF is commonly used as a binder for carbon electrodes. The molecular weight (MW) of PVDF has a significant impact on the microstructure and electrochemical performance of the electrodes. Therefore, selecting the appropriate MW of PVDF is crucial for the application of electrodes. This study examined electrodes prepared with four different PVDF MWs (400,000 to 900,000). It was found that the electrodes made from different MW PVDF showed similar porosity and pore size distribution. The phenomenon of PVDF and carbon coil around was more pronounced when a higher MW of PVDF was used. As inherent to hydrophobicity and low conductivity of PVDF, which hinder the conductive pathway, make the electrode performance deteriorate. High addition of PVDF blocked the active site and affected adsorption. High MW electrodes have a longer life and stronger network, but proper reduction of MW may improve electrochemical properties. The structure of the slurry plays a key role in determining electrode properties. High MW PVDF showed more entanglement and permeation at higher concentrations. Lower MW PVDF forms a homogeneous cross-linking structure that can quickly rebuild if destroyed. However, too low MW weakens intermolecular forces.