Synthesis and Preliminary Electrochemical Characterization of LiNi 0.5 Co 0.5 O 2 Powders Obtained by the Complex Sol-Ge
- PDF / 448,249 Bytes
- 6 Pages / 414.72 x 648 pts Page_size
- 19 Downloads / 170 Views
ABSTRACT Complex Sol-Gel Process (CSGP) was applied to the preparation of LiNi0 .SCo 0 .50 2. Starting sol-solutions were prepared in two different ways: I, in which aqueous ammonia was added to a starting solution of Li -Ni2 -Co2 ' acetate-ascorbate, and II in which LiOH was added to a solution of Ni2+- Co 2+ and NH4+ acetate-ascorbate. It was found that in the absence of ascorbic acid, or at its lower content (•0.2 M on IM I Li'- Ni2+- Co 2+) precipitation of Ni hydroxides occurred. Regular sols were concentrated -3 times, gelled and dried at 140TC. 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 (-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 LiNi0 .5 Co 0.50 2 is observed after heating for lh at 800TC. For larger scale production the extension of firing time was necessary. Electrochemical properties of the LiNio.5Co 0.50 2 compound, prepared by the CSGP were evaluated and considered satisfactory. INTRODUCTION
Lithiated transition metal oxides having a layered structure and the general formula LiMO 2, have been extensively studied as positive electrode active materials for lithium or lithium-ion batteries. Recently LiNi.Col.O 2,especially at x=0.5, is being considered for such applications because of its higher capacity and lower material cost as compared to LiCoO 2 [1,2]. LiNio.5Co0. 50 2 is generally prepared by a solid state processes in which long times, high temperatures and oxygen atmosphere are applied [1-4]. According to the author's best knowledge it has never been synthesized by the sol-gel process. The goal of the present study was the application of the Complex Sol-Gel Process (CSGP) patented by INCT (Poland) and ANL (USA) teams [6] to the fabrication of high temperature superconductors The process has also been successfully applied to the synthesis of Li.Mn 20 4±8 [5]. EXPERIMENTAL The experimental procedures were similar as in former experiments on the synthesis of Li0.ss. 1 1M.n20 4±8 by CSGP described in [5]. Starting sol-solutions were prepared in two different 2 2 ways: I, in which aqueous ammonia (Am) was added to the starting solution of Li÷-Ni +-Co1 2 2 acetate (AC)-ascorbate (ASC), and II in which LiOH was added to the solution of Ni +- Co ' and NH4+ acetate-ascorbate. For evaluation of the CSGP results some experiments, without addition of ascorbic acid were carried out. All reagents used were of A.R. grade. Concentrated solutions were prepared by dissolving the reagents in deionized water (equipment produced by ,,Deionizatori" Genoa, Italy). Molar concentrations of the starting solutions were: LiAC-3.429M; 347 Mat. Res. Soc. Symp. Proc. Vol. 496 0 1998 Materials Research Society
3.429M; NiAC2-0.641M; CoAC2- 1.161M, NH4 OH- 12,1; LiOH- 4.25M. Solid ascorbic acid was added to the acetate solutions. Li concentrations in the starting
Data Loading...
