First-principles study of slag impurity doped Na₂Ti₃O₇ as anode material for Na-ion batteries

Abstract

Abstract Na 2 Ti 3 O 7 (NTO) has attracted significant attention as a promising anode material for sodium-ion batteries (SIBs). However, its practical electrochemical performance is hindered by its inherently low electronic conductivity. To address this limitation, researchers have turned to elemental doping as an effective strategy to enhance the conductivity of NTO electrodes. Interestingly, the process of purifying titanium for NTO synthesis often yields Al and Ca impurities, which can be harnessed as cost-effective dopants. In this study, we employ first-principles calculations to conduct a comprehensive investigation into the structural, electronic, and sodium ion diffusion properties of NTO when doped with Al and Ca, either individually or in combination. Doping system structure has good stability. Our findings reveal that both Al or Ca single-doping Our findings reveal that all the Al and Ca single-doping, and AlCa co-doping transform NTO from semiconducting into metallicity. Notably, the sodium ion migration barriers for Ca single-doping greatly decrease (0.13 eV) compared with that of pristine NTO (0.23 eV), indicating fast ion transport. The insights gained from our research hold promise for the development of cost-effective multi-component anode materials for SIBs.