Controlling Molten-Salt Assisted Calcination for Single-Crystal Growth of Ni-Rich NMC Cathode Materials

Ni-rich LiNixMnyCozO2 (NMC) cathodes (with x ≥ 0.8, x + y + z = 1) attract strong attention for their high energy density in electric vehicle (EV) batteries. However, the application of Ni-rich cathodes has been limited by their low capacity retention, stemming from inherent structural and interfacial instabilities. A promising approach is to synthesize single crystal particles that are relatively more resistant to intergranular fracture and surface degradation. Molten-salt-assisted calcination is an effective method to synthesize single-crystal NMC with significant control over crystal growth and morphology. However, a deeper understanding of the underlying crystallization mechanism and optimization are needed for practical improvements. Previous studies involved large volumes of molten salt that inefficiently necessitate multiple rinsing steps and generates more waste. In this project, molten-salt mediated transformation of Ni0.85Mn0.05Co0.15(OH)2 precursor (P-NMC) particles to LiNi0.85Mn0.05Co0.15O2 particles in reduced volume of molten salt (KCl) is investigated with a focus on crystal growth mechanism and its electrochemical response. Our results highlight that reducing the volume of molten salt (KCl) led to partial dissolution and heterogeneous nucleation-growth, resulting in larger primary particles with improved cycling performance. This finding offers new insights into the role of the molten-salt to NMC mass ratio as an important parameter in manufacturing single-crystal Ni-rich NMC cathodes. Figure 1