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  • Electrochemistry of sodium ...
    Leite, Marina M.; Martins, Vitor L.; Vichi, Flavio M.; Torresi, Roberto M.

    Electrochimica acta, 01/2020, Letnik: 331
    Journal Article

    Sodium-ion batteries are a promising alternative to lithium-ion devices, but the development of proper negative electrode materials is still challenging. Here, the properties of a low-voltage sodium titanate material are evaluated. Sodium titanate nanotubes (NTO) were produced by an alkalyne alkaline hydrothermal treatment with TiO2 and consisted of a hydrated Na1.4H0.6Ti3O7 with a surface area of 128 m2 g−1. NTO electrode kinetics were studied by cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic intermittent titration techniques. The (de)intercalation of Na+ ions involved two redox pairs at 0.3/0.5 V and 1.0/1.2 V, associated with the present mixture of nanotubes and nanosheets. Surface processes had a 95% coulombic efficiency and a high contribution even at low scan rates, accounting for 47% of the total capacity at 0.5 mV s−1. Upon Na+ removal, the electronic resistance and the semiconductor capacitance increased. Battery tests performed on Na|NTO half-cells showed a reversible capacity of 90 mA h g−1 at 10 mA g−1 and near 100% coulombic efficiency at current rates ranging from 10 mA g−1 to 10 A g−1. Additionally, NTO presented a good capacity retention of 92% after 170 cycles at 100 mA g−1. •Surface process contribution is 47% at 0.5 V s−1 with 95% efficiency.•Finite-space diffusion model to fit EIS data considering particle-size distribution.•(Semi)conductive properties of NTO change with (de)sodiation.•Electrode capacity of 93 mA h g−1 at 10 mA g−1•92% capacity retention after 170 cycles at 100 mA g−1