NMC622 Rock-Salt Oxide Precursor Synthesized by a Molten-Salt Process.

Abstract

Single-phase rock-salt (RS) Ni-Mn-Co oxides were synthesized from NiO, MnO, and CoO powder mixtures with or without sodium sulfate as molten-salt flux and subsequently used as precursors for the all-dry synthesis of LiNi_0.6Mn_0.2Co_0.2O₂ (NMC622). Pelletization and the utilization of a molten salt were both effective in improving the crystallinity and compositional inhomogeneity of RS precursors, to such a degree that RS precursors prepared with the molten-salt method required only simple hand mixing of the oxide components to achieve a similar level of compositional homogeneity as RS precursors prepared with more than an hour of intense grinding. The enhanced homogeneity of the RS precursor made with a molten-salt process also translated into enhanced homogeneity and electrochemical performance in its product NMC. These results show that utilizing a molten salt in RS-precursor synthesis can potentially reduce cost and processing steps in all-dry NMC synthesis.