NEW LITHIUM-ION CONDUCTING COMPOUNDS 3LI(3)N-MI (M = LI, NA, K, RB) AND THEIR APPLICATION TO SOLID-STATE LITHIUM-ION CELLS

In the quasi-binary systems Li3N-MI (M=Li, Na, K, Rb) new intermediate compounds 3Li(3)N-MI? were synthesized by a solid-stare reaction betw een Li3N and MI at 600 degrees C., They were isomorphous and had a tet ragonal unit cell. Their sintered bodies exhibited lithium-ion conduct ivity of 1.1 x 10(-4)-7.0 X 10(-5) S cm(-1) at room temperature. The g rain boundary resistances were negligibly small because of their goad sinterability. The decomposition voltages were approximately 2.5-2.8 V , much higher than that of Li3N. Even the compacts of the powdered com pounds showed total conductivities more than 10(-5) S cm(-1). This all owed the cell construction of the solid-state lithium-ion cell, C/3Li( 3)N-KI/LiTiS2,, simply by pressing the powdered electrolyte and electr ode materials. The cell was able to charge and to discharge at a const ant current of 15 mu A cm(-2) at room temperature: however, severe pol arization in the positive electrodes limited the charge/discharge perf ormance. (C) 1997 Elsevier Science S.A.