ИСТИНА

LiNixMnxCo1-2xO2 materials are a promising alternative to LiCoO2 as cathode materials for lithium-ion batteries. Among their advantages there are an outstanding combination of high specific electrochemical capacity (up to 230 mAh g-1) and a potential reversibility at high discharge potentials (4.6 – 4.8 V) promoting the higher energy density of the battery. In spite of a large number of research groups involved in the studies of Li(Li,Ni,Mn,Co)O2-based cathode materials, only a few synthesis methods are usually applied in their studies. First of all it concerns the coprecipitation of transition metal hydroxides. Freeze-drying technique has been widely used for the preparation of inorganic materials based on complex oxides (e.g. high-temperature superconductors, ferrites etc.) but its application for the synthesis of Li,Ni,Mn,Co)O2 is rather limited. In the present study LiNi1/2Mn1/2O2, LiNi0.45Co0.1Mn0.45O2, LiNi0.4Co0.2Mn0.4O2 and LiNi0.35Co0.3Mn0.35O2 were synthesized using three different combinations of freeze-dried salt precursors (mixture of nitrates, acetates and combined mixture). The processes of thermal decomposition of freeze-dried salt precursors were studied by thermal analysis. The obtained materials were studied by X-Ray diffraction and scanning electron microscopy. It was found that the optimal synthesis conditions were the annealing of freeze-dried mixture of nitrates at 900ºC for 3 hours, because at lower temperatures the degree of crystallinity remains rather low. Cell parameters increase with the decrease in cobalt content (for example, for LiNi0.35Co0.3Mn0.35O2 a=2.8582(3) Å, c=14.2231(14) Å), the c/a ratio, 001/104 peak height ratio, 018/110 peak splitting, which give information about cation ordering in LiNixMnxCo1-2xO2 structure, increases with the cobalt content. Average particle size is about 70-100 nm for LiNi1/2Mn1/2O2 and slightly increases with cobalt content. As expected, particle size increases with the annealing temperature. The particle size distribution is rather wide in the case of the materials obtained from nitrate precursor and more narrow in the case of the materials obtained from the acetate precursor. Electrochemical measurements on the obtained materials are in progress. This work was supported by the Federal Targeted Program “Scientific and Scientific–Pedagogical Specialists of Innovational Russia” for 2009–2013 (state contract # P699).