Synthesis and Preliminary Electrochemical Characterization of LiNi_0.5Co_0.5O₂ Powders Obtained by the Complex Sol-Gel Process (CSGP)

Abstract

Complex Sol-Gel Process (CSGP) was applied to the preparation of LiNi0.5Co0.5O2. 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+- Co2+ and NH4+ acetate-ascorbate. It was found that in the absence of ascorbic acid, or at its lower content (≤0.2 M on 1M σ Li+- Ni2+- Co2+) precipitation of Ni hydroxides occurred. Regular sols were concentrated ∼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 (∼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 LiNi0.5Co0.5O2 is observed after heating for Ih at 800°C. For larger scale production the extension of firing time was necessary. Electrochemical properties of the LiNi0.5Co0.5O2 compound, prepared by the CSGP were evaluated and considered satisfactory.

Novel Sol-Gel Synthesis of LiMn₂O₄ and LiNi_xCo_1-xO₂ Powders

“…Key electrochemical properties important for Li-battery applications were measured for some of the specimens that were heated for 1 h (Table 2). The values obtained for these oxides were comparable to values reported in literature for layered oxides of this composition, including samples that were prepared by routine by routine CSGP, but lengthy and laborious procedures for decarbonization were eliminated [1][2][3]7,[20][21][22][23].…”

“…They are the only known materials that are capable of reversibly intercalating lithium at high cell voltages. In previous papers [1][2][3][4][5][6], we described a new variant of sol-gel processing, the complex sol-gel process (CSGP). It proved suitable for synthesizing both LiMn 2 O 4 and LiNi x Co 1-x O 2 .…”

“…Subsequent thermal treatment has been accompanied by violent self-ignition. For oxides that contain Ni [1][2][3][4][5][6], appreciable concentrations of carbonates have been observed in the final products made by CSGP and poorer electrochemical properties have resulted [9]. Formation of carbonates during our processing can be attributed to use of ASC in the sols.…”

Electrochemical characterization of a lithiated mixed nickel-cobalt oxide (LiNi0.5Co0.5O2) prepared by sol-gel process

“…1 confirm the formation of a unique phase with the expected layered (SG=R3m) structure. However, the shape of the peak at The details of this sol-gel synthesis can be found elsewhere [15]. The chemical analysis of the powders gave the real composition of LiNi0.sCo0.4901.985 and the SEM analysis the mean particle radius ranging from 1 to 10 ktm, Fig 2. …”

“…In this work we have studied LiNixCovxO2 samples with x=0.5, prepared using the Complex Sol-Gel Process (CSGP) patented by the INCT (Poland) and ANL (USA) teams [11][12][13][14]. The advantages of the sol-gel over the solid-state process are well known: the synthesized compounds show high homogeneity in composition and in particle dimension; furthermore lower temperature and/or less time is needed for the reaction to occur completely.…”