UCLA

Fast charging of Ni-rich layered oxide cathodes is limited by slow Li⁺ transport and large structural changes at high states of charge. This thesis investigated nanostructuring and multi-element doping as a combined strategy for developing cobalt-free Ni-rich cathodes. NM-MgNbMo, NM-MgAlMo, and NM-MgTiNbMo were synthesized using a polymer-assisted micelle-templated sol–gel method and compared with bulk and less porous NMC-811. X-ray diffraction confirmed the layered α-NaFeO₂-type structure and distinct interlayer spacings; NM-MgNbMo had the least apparent cation mixing and largest spacing, supporting easier Li⁺ transport and faster kinetics, while partial disorder may provide a stabilizing pillaring effect. NM-MgNbMo exhibited the best high-rate performance among the doped samples, maintaining approximately 36 mAh/g at 32C when the capacity of bulk NMC-811 approached zero. CV and GITT measurements were also consistent with comparatively low apparent polarization for NM-MgNbMo. After 1000 cycles at 8C, NM-MgNbMo retained the highest absolute capacity, whereas NM-MgTiNbMo showed the highest fractional retention from a lower initial capacity. Operando X-ray diffraction showed substantially smaller c-lattice changes in the doped samples than in the NMC-811 references. Overall, NM-MgNbMo provided the best balance between high-rate capacity and structural stability, while NM-MgTiNbMo favored structural stability at the cost of accessible capacity.