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 prep ared by incorporating 1-5 wt% soluble electrically conducting polyaniline ( PANI) in lithium-selective plasticized PVC membranes. The performance of th e LiSPEs were characterized with potentiometry, electrochemical impedance s pectroscopy (EIS), transmission electron microscopy (TEM), quartz crystal m icrobalance (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 sub strate (glassy carbon)-membrane interface. The impedance spectra of three L iSPEs were almost identical whereas large variations in the low frequency r egion 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 o n 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, t he water uptake of the LiSPE membranes was studied with the QCM. Finally, i t was observed with TEM that PANI forms a dispersion with an incomplete net work structure within the PVC matrix. (C) 1999 Elsevier Science B.V. All ri ghts reserved.