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.

Automated summary

This study presents synthetic approaches to produce different morphologies of SC LiNi0.8Co0.1Mn0.1O2 (NMC811) samples and analyzes their performance. The results show that Poly-SC811 with a predominating (104) surface exhibits superior performance even under high charge rates, attributed to its better chemical and structural stabilities, faster Li+ diffusion kinetics, suppressed side reactions with electrolyte, and excellent cracking resistance.