Redox-Active Alkali Insertion Materials as Inner Contact Layer in All-Solid-State Ion-Selective Electrodes

Abstract

Lithium insertion materials, such as LiFePO4, have been widely studied as the electrode materials for rechargeable batteries. Alkali ions can be reversibly inserted/extracted into/from their crystal lattices associated with electrochemical redox. In this study, we apply lithium, sodium, and potassium insertion materials as inner contacting layers for the all-solid-state ion-selective electrodes which are covered with the outer ion-selective poly(vinyl chloride) membrane containing ionophore and plasticizer. The introduction of alkali insertion materials layer between Pt substrate and ion selective membrane is highly efficient for the stabilization of membrane potential and its prompt response when alkaline ion activity in analyte changes compared to those of the electrode without alkali insertion materials. Electrochemical measurements reveal that alkali insertion materials as the inner contact layers stabilize the membrane potential because of drastic reduction of interface resistance at the electrode, and thus improves ion-sensing performance.