A flexible and hydrophobic polyurethane elastomer used as binder for the activated carbon electrode in capacitive deionization

Activated carbon (AC) is widely used as an electrode material in capacitive deionization (CDI) process. The AC electrode is generally fabricated by a slurry mixture containing AC, polymer binder and conductive additive on the current collector. Polyvinylidene fluoride (PVDF) is often used as the electrode binder. The rigidness of PVDF can generate the mechanical crack at the electrode interface and then lead to loss in electrode performance. In this study, a flexible and moisture cured hydrophobic polyurethane (PU) elastomer was investigated as a novel binder for the AC electrode. It was formed from polytetramethylene glycol (PTMEG), 2, 4-toluene diisocyanate (TDI) and glycerin monostearate (GMS) diol. Two electrochemical techniques, including the cyclic voltammetry (CV) and the electrochemical impedance spectrometry (EIS) were used to characterize the electrochemical properties of the PU-bonded electrode. The experimental results indicate that this binder can be considered as a PVDF-analogy binder. In comparison to the PVDF binder, the CV and EIS results indicate that the polar urethane and urea groups and high flexibility of PTMEG and GMS in this PU elastomer binder can improve the rigidness problem and have comparable and stable capacitive performance. The deionization result also shows more stable electrosorption-desorption behavior for the PU-bonded electrode.