Comprehensive Study of Al- and Zr-Modified LiNi_0.8Mn_0.1Co_0.1O₂ through Synergy of Coating and Doping

LiNi0.8Mn0.1Co0.1O2 (NMC811) is one of the most promising Li-ion battery cathodes for next-generation electric vehicles. Enrichment of Ni cations in NMC811 enables its high capacity and energy density, but meanwhile, it triggers instability of cyclic performance and shortens the lifespan. To improve the cyclic stability of NMC811, we studied and compared properties of aluminum (Al) and zirconium (Zr) as synergetic coating and doping materials for modification and rationally combined their advantages after investigation. For comparison, either Al2O3 or ZrO2 thin films were conformally coated on the surfaces of NMC811 particles by atomic layer deposition, followed by a postannealing of coated NMC811 at 750 °C for uniform surface doping. Al and Zr modifications improved the electrochemical performance of NMC811 in different manners; NMC811, with Al modification, showed better stability but with a sacrifice of capacity, while the capacity of Zr-modified NMC811 was only slightly reduced and Zr-doping facilitated Li+ transport. Therefore, Al-surface modification and Zr doping were combined based on our comparison.