The First Open-Framework Cadmium Phosphate, K4[Cd3(HPO4)4(H2PO4)2], with a Layered Structure

Li2NaV2(PO4)3has been prepared in the rhombohedral NASICON structure via ion exchange from Na3V2(PO4)3. As a lithium-insertion cathode material, Li2NaV2(PO4)3 exhibits a specific discharge capacity of 96 mAh g-1 at a current density of 0.50 mA cm-2 with a clear plateau near 3.7 V versus lithium metal. Approximately 10% of the capacity is lost through the first 50 cycles, after which the capacity appears to stabilize. During charge and discharge, the Na+ ions tend to remain immobilized in the A(1) site of the NASICON structure, suggesting a direct A(2)A(2) lithium-transport mechanism.