Formation mechanisms of Ni-rich LiNi1-x-yMnxCoyO2 battery cathode materials in flame aerosol synthesis

We report on the synthesis of Ni-rich LiNi0.8Co0.1Mn0.1O2 (NCM811) Li-ion battery cathode materials using micron-scale aqueous metal nitrate solution droplets delivered to non-premixed flames. The objective is to investigate the effect of the solution composition and synthesis conditions on the particle properties and electrochemical performance in comparison to LiNi0.33 Co0.33Mn0.33O2 (NCM111).

It is found that NCM111 solutions form predominantly spherical particles from single droplets, whereas Ni-rich solutions form irregularly-shaped particles because the lower solubility of the Ni nitrate precursor causes precipitation at the droplet surface and subsequent collapse of the shell-like structure. After annealing, NCM111 retains the secondary particle structure, but NCM811 forms irregular shapes with a broad size distribution of primary features because the higher decomposition temperature of NCM811 precursor solutions limits the oxidation and particle formation in the aerosol phase.

Electrical preheating of the aerosol stream ahead of the flame and controlling the flame temperature can be used to adjust the morphology and crystallinity of the final annealed product. All cathode materials show reasonable first cycle efficiency and discharge capacity. For NCM811, higher preheating temperatures (450 K) with lower flame temperatures (1350 K) show the best cycling performance.

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