Electrochemical insertion of lithium and sodium into (MoO2)2P2O7

Insertion of lithium and sodium into phosphate (MoO2)2P2O7 was investigated electrochemically to determine the usefulness as a possible cathode for ion-transfer secondary batteries. Specific charges of up to 250 mAhg-1 were obtained for A/(MoO2)2P2O7(A:Li,Na) cells with liquid organic electrolytes in the first reduction half-cycle at room temperature. Intercalation processes under constant current densities of 0.2 mA cm-2 were reversible within the range of composition 0.85 < x < 4.0 for lithium and 0.5 < x < 3.1 for sodium in Ax(MoO2)2P2O7(A:Li,Na), respectively. Structural changes induced by lithium or sodium intercalation were followed by ex situ X-ray diffraction measurements, and the phase change from the crystal to the amorphous was observed in both cases.