All-Dry Synthesis of NMC from [Ni,Mn,Co]3O4 Spinel Precursors

Oxides in the NixMn0.5-x/2Co0.5-x/2-O system were investigated as precursors in the all-dry synthesis of NMC622 (LiNi0.6Mn0.2Co0.2O2). Single-phase spinel precursors in this system were found to have the highest compositional homogeneity. To synthesize NMC, NixMn0.5-x/2Co0.5-x/2-O precursors were heated with Li2CO3 and NiO (to attain the correct NMC stoichiometry) in air or oxygen. This represents a different strategy in NMC synthesis compared to conventional hydroxide precursors that have the same composition as the final NMC. The most homogeneous and best performing NMC (171.9 mAh g(-1) with 90% after 183 cycles) were obtained by using precursors that were essentially single-phase cubic spinel (0.070 <= x <= 0.091 in NixMn0.5-x/2Co0.5-x/2-O) even though such precursors had compositions that had significantly less Ni content than the target NMC622 composition. These findings demonstrate an alternate route for obtaining compositional homogeneity in NMC all-dry synthesis.