Prospects for Employing Lithium Copper Phosphates as High-Voltage Li-Ion Cathodes

Abstract

Three compositions of lithium copper phosphates: Li 2 CuPO 4 , Li 2 Cu 5 (PO 4 ) 4 , and Li 2 CuP 2 O 7 have been studied as high-voltage cathode materials for Li-ion batteries, following computational predictions of high operating voltages. An assisted-microwave preparation of Li 2 CuPO 4 , which is otherwise difficult to prepare in nearly-pure form, has been developed. The electrochemical performance of all three compounds has been investigated. The cyclability of these materials is found to be poor due to structural changes, irreversible reduction to metallic copper even at potentials as high as 2.5 V, and the possibility of dissolution into the electrolyte. Some general understanding in regard to the use of Cu compounds in redox electrodes is presented.