Single‐Crystal LiNixMnyCo1−x−yO2 Cathodes for Extreme Fast Charging

Ni‐rich layered LiNixMnyCo1−x−yO2 (NMCs, x ≥ 0.8) are poised to be the dominating cathode materials for lithium‐ion batteries for the foreseeable future. Conventional polycrystalline NMCs, however, suffer from severe cracking along the grain boundaries of primary particles and capacity loss under high charge and/or discharge rates, hindering their implementation in fast‐charging electric vehicular (EV) batteries. Single‐crystal (SC) NMCs are attractive alternatives as they eliminate intergranular cracking and allow for grain‐level surface optimization for fast Li transport. In the present study, the authors report synthetic approaches to produce SC LiNi0.8Co0.1Mn0.1O2 (NMC811) samples with different morphologies: Oct‐SC811 with predominating (012)‐family surface and Poly‐SC811 with predominating (104)‐family surface. Poly‐SC811, representing the first experimentally synthesized NMC811 single crystals with (104) surface, delivers superior performance even at the ultra‐high rate of 6 C. Through detailed X‐ray analysis and electron microscopy characterization, it is shown that the enhanced performance originates from better chemical and structural stabilities, faster Li+ diffusion kinetics, suppressed side reactions with electrolyte, and excellent cracking resistance. These insights provide important design guidelines in the future development of fast‐charging NMC‐type cathode materials. Synthetic approaches to produce Ni‐rich LiNixMnyCo1−x−yO2 single‐crystal samples with well‐defined morphologies and surfaces are reported. Polyhedron‐shaped LiNi0.8Co0.1Mn0.1O2 crystals with (104)‐family surface are found to deliver much better fast‐charging performance than the conventional polycrystalline counterpart. The improvement is attributed to enhanced chemical and structural stabilities, faster Li+ diffusion, suppressed side reactions with electrolyte and excellent particle cracking resistance.