Characterization of a single-piece all-solid-state lithium-selective electrode based on soluble conducting polyaniline

Single-piece all-solid-state lithium-selective electrodes (LiSPE) were prepared by incorporating 1-5 wt% soluble electrically conducting polyaniline (PANI) in lithium-selective plasticized PVC membranes. The performance of the LiSPEs were characterized with potentiometry, electrochemical impedance spectroscopy (EIS), transmission electron microscopy (TEM), quartz crystal microbalance (QCM) and energy dispersive X-ray analysis (EDXA). Addition of 1% and 2% PANI improved significantly the potential stability and potential reproducibility of the LiSPEs compared to lithium coated-wire electrodes (LiCWE) which did not contain any PANI. The reason for the better potential stability of the LiSPE is that PANI improves the charge transfer at the substrate (glassy carbon)-membrane interface. The impedance spectra of three LiSPEs were almost identical whereas large variations in the low frequency region were observed for three LiCWEs. It shows that the substrate-membrane interface is better defined in the LiSPEs than in the LiCWEs. Furthermore, EDXA measurements show that the concentration of PANI was slightly higher on the substrate-membrane side than on the membrane-solution side of a LiSPE membrane with the PANI content greater than or equal to 2%. Furthermore, the water uptake of the LiSPE membranes was studied with the QCM. Finally, it was observed with TEM that PANI forms a dispersion with an incomplete network structure within the PVC matrix.