Three dimensional titanium dioxide nanotube arrays induced nanoporous structures and stable solid electrolyte interphase layer for excellent sodium storage in ether-based electrolyte

The commercial feasibility of sodium ion batteries (SIBs) is currently limited by the lack of anode materials that simultaneously provide high-rate capability and long cycle stability. In this study, we report three-dimensional (3D) anatase TiO₂ nanotube arrays (TiO₂ NTAs) as an SIB anode for excellent sodium storage when paired with ether-based electrolyte. The TiO₂ NTAs anode exhibits minimal capacity decay over 3000 cycles at 1C and 5000 cycles at 20C in ether-based electrolyte, demonstrating both excellent rate capability and long-term cycle stability. Structural analysis reveals novel discovery that the 3D TiO₂ NTAs develop into unique nanoporous structures that sustain during repeated redox cycles in ether-based electrolyte. On the one hand, these nanoporous structures can provide more accessible areas for Na⁺ intercalation and de-intercalation, enabling fast Na⁺ intercalation. On the other hand, they also promote the formation of a thin and stable solid electrolyte interphase (SEI) in ether-based electrolyte that facilitates long-term cycle stability. Our investigation advances the performance of TiO₂ as a promising SIBs anode material and also offers valuable insights into the impact of unique nanoporous structure to the excellent electrochemical performance.