1D hydrogen titanium oxide hydrate with large interlayer spacing as an intercalation-type anode material for...

Low-temperature-resistant sodium-ion batteries (SIBs) are widely regarded as a key technology for future energy storage needs. Nevertheless, the large ionic radius of Na⁺ necessitates anode materials with expanded interlayer spacing to enable fast ion transport and sufficient storage capacity. Herein, a one-dimensional (1D) hydrogen titanium oxide hydrate (H₂Ti₂O₅∙H₂O) with an expanded interlayer spacing and abundant anion vacancies was successfully constructed through hydrothermal synthesis. When evaluated as a SIB anode, the material delivers an initial specific capacity of 175.7 mAh g^-1 at a current density of 50 mA g^-1. Notably, it maintains a capacity of 105.0 mAh g^-1 even when the current density is increased to 500 mA g^-1. Remarkably, it exhibits excellent cycling stability with a highly reversible capacity of 102.1 mAh g^-1 retained after 1000 cycles at 500 mA g^-1. In addition, the assembled full cell with H₂Ti₂O₅∙H₂O anode exhibits good electrochemical performance, even at extremely low-temperature condition (-40 °C), with a capacity retention of 79.3 %, relative to that at 25 °C. Through the comprehensive analysis of in-situ electrochemical spectroscopy, complemented by ex-situ XRD detection and DFT calculation, additional pseudo-capacitance intercalation Na⁺ storage behavior and fast ion transport kinetics of 1D H₂Ti₂O₅∙H₂O are ascertained. This work provides fundamental insights for designing advanced intercalation anodes to achieve durable and robust SIBs.