Electrochemical Properties of Electrodes Derived from NaTi₃O₆OH•2H₂O in Sodium and Lithium Cells

Materials derived from the layered compound NaTi₃O₆OH·2H₂O, also known as “sodium nonatitanate” or NNT, have recently been found to undergo reversible sodium or lithium intercalation processes at very low potentials. While practical discharge capacities in lithium cells can be above 200 mAh/g, making them of interest for high-energy applications, the presence of mobile sodium in the materials complicates the cycling behavior. A simple ion-exchange process prior to incorporation in electrochemical cells removes all sodium ions, producing the lithiated form of the material. The lithiated material (LNT) performs similarly to NNT in lithium cells, although coulombic inefficiencies are somewhat higher. A comparison is made between the behavior of NNT in sodium cells and that of NNT and the lithiated analog in lithium cells.