Microwave solid-state synthesis and electrochemical properties of carbon-free Li 3V 2(PO 4) 3 as cathode materials for lithium batteries

Abstract

Monoclinic Li 3V 2(PO 4) 3 can be rapidly synthesized at 750 °C for 5 min (MW5m) by using microwave solid-state synthesis method. The refined cell parameters and atomic coordination of the sample MW5m show some deviations compared with those of the sample synthesized in conventional solid-state synthesis method, especially the coordinate of Li atoms. Compared with the electrochemical properties of the carbon-coating sample Li 3V 2(PO 4) 3, the carbon-free sample MW5m presents well electrochemical properties. In the cut-off voltage of 3.0–4.3 V, MW5m sample presents a specific charge capacity of 132 mAh g −1, almost equivalent to the reversible cycling of two lithium ions per Li 3V 2(PO 4) 3 formula unit (133 mAh g −1), and specific discharge capacity of 126.4 mAh g −1. In the cut-off voltage of 3.0–4.8 V, MW5m shows an initial specific discharge capacity of 183.4 mAh g −1 at 0.1 C, near the theoretical discharge capacity. In the cycle performance, the capacity fade of Li 3V 2(PO 4) 3 is dependent on the cut-off voltage and the preparation method, more capacity lost at relatively higher charge/discharge voltage. The reasons for the excellent electrochemical properties of Li 3V 2(PO 4) 3 rapidly synthesized in microwave field are discussed in detail.