Synthesis and preliminary electrochemical characterization of LiNi{sub 0.5}Co{sub 0.5}O{sub 2} powders obtained by the complex sol-gel process (CSGP)

Complex Sol-Gel Process (CSGP) was applied to the preparation of LiNi{sub 0.5}Co{sub 0.5}O{sub 2}. Starting sol-solutions were prepared in two different ways: I, in which aqueous ammonia was added to a starting solution of Li{sup +}-Ni{sup 2+}-Co{sup 2+} acetate-ascorbate, and II in which LiOH was added to a solution of Ni{sup 2+} - Co{sup 2+} and NH{sub 4{sup +}} acetate-ascorbate. It was found that in the absence of ascorbic acid, or at its lower content ({le}0.2 M on 1M {Sigma} Li{sup +} - Ni{sup 2+} - Co{sup 2+}) precipitation of Ni hydroxides occurred. Regular sols were concentrated {approximately}3 times, gelled and dried at 140 C. Intensive foaming was observed for samples during further heating. Consequently for scaling up to 200g in a run a preliminary long drying procedure followed by self-ignition step ({approximately}400 C) was introduced. Thermal transformation of the gel to solid was studied by TG, DTA, XRD and IR. The main feature of this step is carbonate formation. The final structure LiNi{sub 0.5}Co{sub 0.5}O{sub 2} is observed after heating for 1h at 800 C. For larger scale production the extension of firing time was necessary. Electrochemical properties of the LiNi{sub 0.5}Co{sub 0.5}O{sub 2} compound, prepared by the CSGPmore » were evaluated and considered satisfactory.« less