Li2CuVO4: A high capacity positive electrode material for Li-ion batteries

• We have been able to grow Li2CuVO4 single crystals.
• We solved the crystal structure using single crystal data.
• Li2CuVO4 is a good ionic conductor at temperatures above 100 °C.
• Interestingly, 2 lithium atoms can be reversibly extracted/inserted from/in Li2CuVO4.
• Li2CuVO4 shows high rate capability with a capacity of 175 mA h g−1 at 1C rate.

The new compound Li2CuVO4 was synthesized by a solid state reaction route, and its crystal structure was determined from single crystal X-ray diffraction data. Li2CuVO4 was characterized by galvanometric cycling, cycle voltammetry, and electrochemical impedance spectroscopy. The structure of Li2CuVO4 is isotypic to Pmn21-Li3VO4. It can be described as a disordered wurtzite structure with rows of Li1/Cu1 atoms alternating with rows of (Li2/Cu2)-V-(Li2/Cu2) atoms along [100]. All cations are tetrahedrally coordinated. The lithium and copper atoms are statistically disordered over two crystallographic sites. The electrochemical cycling between 2.0 and 4.7 V indicates that almost two lithium atoms could be extracted and re-intercalated. This delivers a maximum discharge capacity of 257 mA h g−1 at a C/50 rate (theoretical capacity = 139 mA h g−1 for one lithium). Li2CuVO4 shows also high rate capability with a capacity of 175 mA h g−1 at 1C rate. This demonstrates that Cu-based compounds can be very interesting as electrodes for Li-ion batteries if Cu-dissolution is avoided.

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