10.1016/j.jpowsour.2010.06.097
Synthesis and electrochemical properties of LiNi0.8Co0.2O2 nanopowders for lithium ion battery applications 
Nitrates of lithium, cobalt and nickel are utilized to synthesize LiNi0.8Co0.2O2 cathode material through sol-gel technique. Various synthesis parameters such as calcination time and temperature as well as chelating agent are studied to determine the optimized condition for material processing. Using TG/DTA techniques, the optimized calcination temperatures are selected. Different characterization techniques such as ICP, XRD and TEM are employed to characterize the chemical composition, crystal structure, size and morphology of the powders. Micron and nano-sized powders are produced using citric/oxalic and TEA as chelating agent, respectively. Selected powders are used as cathode material to assemble batteries. Charge-discharge testing of these batteries show that the highest discharge capacity is 173 mAh g-1 at a constant current of 0.1 mA cm-2, between 3.0 and 4.2 V. This is obtained in a battery assembled with the nanopowder produced by TEA as chelating agent. The stoichiometric values of lithium, nickel and cobalt nitrate salts in a cationic ratio of Li:Ni:Co equal to 1:0.8:0.2 were dissolved in distilled water. Three chelating agents including triethanolamine (TEA), citric acid, oxalic acid are used in this investigation. These agents were used in a molar ratio of 1 with respect to the total metal cations by dissolving in distilled water. The solution was then added to the nitrate solution and was heated under constant stirring at 80 degC for 1 h. The resulting sol was heated at 100 degC to form the gel which was dried subsequently. To remove the moisture and achieve the dried mass, the obtained gel was successively dried at 100, 120, 150, 200 degC for 2 h per each step and 5 h at 240 degC. The thermal behavior of LiNi0.8Co0.2O2 powders was determined by thermogravimetric/differential thermal analysis (TG/DTA) conducted on the dried gel at a heating rate of 5 degC min-1 up to 1100 degC in the air using a Perkin Elmer analyzer. The tests were conducted in the air using alumina pans. The initial sample weights for TEA, oxalic and citric were 460, 250 and 290 mg, respectively. The dried mass was heated at 500, 600, 700, 800 and 900 degC for varying durations and slowly cooled to room temperature. Inductively coupled plasma (ICP) analysis was performed using an ARL 3410 unit to confirm the stoichiometry of lithium, nickel and cobalt in the synthesized powders. The resulting powders had molar ratios of Li: Ni:Co in the order of 1:0.8:0.2, respectively.
batteries
highest discharge capacity
173 mAh g-1
mAh g-1
batteries
constant current
0.1 mA cm-2
mA cm-2
batteries
3.0
batteries
4.2
Li:Ni:Co
cationic ratio
1:0.8:0.2
agents
molar ratio
1
solution
heated
80 degC
degC
solution
heated
1 h
h
resulting sol
heated
100 degC
degC
obtained gel
successively dried
100, 120, 150, 200 degC
degC
obtained gel
dried
5 h
h
thermogravimetric/differential thermal analysis (TG/DTA) conducted on the dried gel
heating rate
5 degC min-1
degC min-1
thermogravimetric/differential thermal analysis (TG/DTA) conducted on the dried gel
1100 degC
degC
obtained gel
successively dried
2 h
h
obtained gel
dried
240 degC
degC
TEA
sample weights
460, 250 and 290 mg
mg
oxalic
sample weights
250 and 290 mg
mg
citric
sample weights
290 mg
mg
dried mass
heated
500, 600, 700, 800 and 900 degC
degC
Ni:Co
order
1:0.8:0.2