Enabling high capacity and reversible Li storage in indium(III) oxide anode surrounded by carbon nanotube matrix

In ₂O ₃ is one of the post-transition metal oxides that can be a potential anode material for the Li-ion batteries (LIBs) because of its high theoretical capacity (869 mAh g ⁻¹) and low operating voltage (0.8 V vs Li/Li ⁺ ) compared to other metal oxides. However, they have rarely been used in practical applications because of typical challenges such as irreversible capacity, unstable cycling stability, and poor coulombic efficiency. In this study, carbon nanotubes (CNTs) were successfully combined with In ₂O ₃ nanoparticles (NPs) via a solvothermal process. The In ₂O ₃ NPs and CNTs were homogeneously mixed by controlling the CNT dispersion (functionalization and appropriate solvent) and mixing sequence (dissolving the In ₂O ₃ precursor in the CNT-dispersed solution followed by thermal annealing). In addition, an increase in the oxygen vacancies in the In ₂O ₃ NPs by controlling the thermal annealing conditions (In ₂O ₃ /CNT_Ar) could enhance robust binding with CNTs, increase the number of Li-ion binding sites, and improve the electrical conductivity. Therefore, at an appropriate ratio of In ₂O ₃ and CNT (92:8, w/w), the In ₂O ₃/CNT_Ar demonstrated remarkable cycling performance (830 mAh g ⁻¹ at a current density of 200 mA g ⁻¹ after 100 cycles) and rate capability (65% retention at 5 A g ⁻¹ relative to 100 mA g ⁻¹), which outperformed most In ₂O ₃-based anodes previously studied. Therefore, In ₂O ₃/CNT_Ar is a promising anode material for use in next-generation LIBs.