To determine optimum conditions for the synthesis of LiNiO 2 by the combustion method, syntheses were carried out in air and under oxygen at various calcination temperatures and for different times. The electrochemical properties of the prepared samples were then investigated. The optimum conditions are preheating at 400°C for 30 min in air in the mole ratio of urea to nitrate 3.6 and calcination at 750°C for 36 h under O 2 . The LiNiO 2 synthesized under these conditions had a first discharge capacity of 189 mAh g )1 at 0.1 C-rate and relatively good cycling performance. This sample has a larger value of I 003 /I 104 (smaller cation mixing) and a smaller R-factor (larger hexagonal ordering). Cycling performance was investigated in various voltage ranges. The first discharge capacity increased as the upper limit of the voltage range rose. The first discharge capacity was small but cycling performance was good when the sample was cycled in the voltage range with the lowest upper limit.
The optimum conditions for synthesizing LiNi 1-y Co y O 2 (y=0.1, 0.3 and 0.5) by a simplified combustion method, in which the preheating step is omitted, and the electrochemical properties of these materials were investigated. The optimum condition for synthesizing LiNi 0.9 Co 0.1 O 2 by the simplified combustion method is calcination at 800°C for 12 h in air in 3.6 mole ratio of urea to nitrate. The LiNi 0.9 Co 0.1 O 2 synthesized under these conditions shows the smallest R-factor{(I 006 +I 102 )/I 101 } and the largest I 003 /I 104 , indicating better hexagonal ordering and less cation mixing, respectively. The LiNi 0.7 Co 0.3 O 2 synthesized at 800°C for 12 h in air in 3.6 mole ratio of urea to nitrate has the largest first discharge capacity 156.2 mA h g )1 at 0.5C and shows relatively good cycling performance. This sample shows better hexagonal ordering and less cation mixing than the other samples. The particle size of the LiNi 0.7 Co 0.3 O 2 is relatively small and its particles are spherical with uniform particle size.
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