Composition Optimization of Layered Lithium Nickel Manganese Cobalt Oxide Materials Synthesized via Ultrasonic Spray Pyrolysis

Lithium-rich, layered composites of x Li 2 MnO 3 ·(1− x )Li(Ni 1/3 Mn 1/3 Co 1/3 )O 2 were synthesized via spray pyrolysis to identify the chemistry yielding optimal electrochemical performance for materials produced by this method. The x values selected for optimization were x = 0.3, 0.5, 0.7, equivalent to Li 1.14 Mn 0.46 Ni 0.2 Co 0.2 O 2 , Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O 2 and Li 1.26 Mn 0.6 Ni 0.07 Co 0.07 O 2 , respectively. The materials were annealed at 850°C or 900°C for 2 hours, and then tested in coin cells. Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O 2 annealed at 900°C displayed the best electrochemical performance with excellent capacity retention, displaying a reversible capacity of 236 mAhg −1 after 100 cycles when cycled between 2.0–4.8 V at C/10 rate, where 1C = 280 mAg −1 . The cycling profiles display voltage fade, presumably due to a layered-spinel phase transformation. The synthesis method leads to high purity and excellent uniformity at the nanoscale, and the materials have less voltage fade compared to similar materials produced by co-precipitation. Voltage fade is more pronounced when the upper cut-off voltage is 4.8 V, as opposed to 4.6 V. A decrease in the Li 2 MnO 3 content of the material reduces voltage fade, such that x = 0.3 (or Li 1.14 Mn 0.46 Ni 0.2 Co 0.2 O 2 ) shows the best structural stability over cycling.