Li-ion storage characteristics and migration mechanisms of intrinsic, doped, and oxygen-deficient CeO2 and La2O3: A study using DFT+<i>U</i>

Rare-earth oxides (REOs) represented by CeO2 and La2O3 became a focal point in the study of Li-ion battery (LIB) electrode materials. However, leveraging defects to tune the intrinsic electronic structure of REO to enhance electrochemical performance, as well as understanding the underlying physical mechanisms at the atomic level, remained an open challenge. Density functional theory plus U calculations revealed that doping and oxygen vacancies not only regulated Li-ion insertion stability but also reduced the migration energy barriers in CeO2. Doping also decreased the volume change rate of CeO2 during Li-ion insertion. Oxygen vacancies lowered the Li-ion migration energy barrier in CeO2 from 1.516 to 0.903 eV. In comparison, Li-ion migration energy barriers in the La2O3 series structures were significantly lower than those in CeO2. Experimental results confirmed that the Li-ion diffusion coefficient of La2O3 was markedly higher than that of CeO2. Upon Li-ion insertion, the bandgap of CeO2 decreased from 2.18 to 1.60 eV, and density of states analysis revealed the profound impact of lithiation on the electronic structure. This comprehensive study enhances the understanding of the application potential of these typical rare-earth oxide materials in LIBs.