Embedding anatase TiO2 nanoparticles into holely carbon nanofibers for high-performance sodium/lithium ion batteries

Titanium dioxide (TiO2) has been considered as a promising anode material for alkaline ion batteries (AIBs), yet the low electrical conductivity and sluggish reaction kinetics have restricted its practical applications, while rational structure design can significantly overcome these drawbacks. Herein, we report a one-step fabrication of ultrafine anatase TiO2 nanoparticles within holely carbon nanofibers (denoted as A-TiO2 @HCNFs) via a facile electrospinning method and subsequent annealing treatment. The chemical reaction between TEOS (Si(OC2H5)4) and PVDF ((CH2CF2)n) in the precursor induces the generation of numerous holes (via 4HF + SiO2 = SiF4↑+ 2 H2O) during the carbonization process by annealing in Ar at 800 °C, leading to the formation of holely structure and the suppression of the anatase-to-rutile phase transformation. When employed as anode materials for AIBs, the A-TiO2 @HCNFs exhibit a high sodium storage capacity of 206.8 mAh g−1 at 1.0 A g−1 after 500 cycles and a superior rate performance of 188.4 mAh g−1 at 5.0 A g−1, and a lithium storage capacity is 354.0/233.9 mAh g−1 at 0.2/1.0 A g−1 after 100/500 cycles with an excellent rate performance of 145.6 mAh g−1 at 5.0 A g−1. The superior electrochemical performance is related to the unique structure with integration of ultrafine anatase TiO2 nanoparticles and holely carbon nanofibers, which bring many advantages including improved electrical conductivity, sufficient reaction sites and robust structure stability.