Compatibility of LiCoPO 4 Cathode Material with Li 1.5 Al 0.5 Ge 1.5 (PO 4 ) 3 Lithium-Ion-Conducting Solid Electrolyte

— The stability of the LiCoPO 4 electrode material in contact with a NASICON-type lithium ion conducting solid electrolyte having the composition Li 1.5 Al 0.5 Ge 1.5 (PO 4 ) 3 (LAGP) and a wide range of electrochemical stability has been studied for the first time. We have found the optimal temperature at which there is no reaction between the starting components of the composites and they retain their chemical and thermal stability. Cosintering a mechanical mixture of synthesized single-phase LiCoPO 4 and LAGP powders with a submicron particle size at 750°C, we have obtained a stable LiCoPO 4 /LAGP two-phase composite whose room-temperature electrical conductivity is three orders of magnitude higher than that of the lithium cobalt double phosphate. Composites based on LiCoPO 4 and the LAGP ionic conductor can be regarded as promising cathode materials for all-solid-state lithium ion batteries.