Porous TiO2 urchins have been synthesized by a hydrothermal route using TiO2/oleylamine as precursors with subsequent ion-exchange and calcination. The resultant material consists of porous spherical cores and nanochains-constructed shells with straight channels. Electrochemical measurements indicate the TiO2 urchins deliver superior lithium storage capability in terms of high capacity (206.2 mA h g-1 at 0.5 C), superior rate performance (94.4 mA h g-1 at 20 C) and stable cycling stability (94.3% capacity retention over 1000 cycles at 10 C versus the third cycle). Such performance enhancement is mainly due to the increased electrode/electrolyte contact interface, reduced Li+ diffusion pathways and improved mass transfer of electrolyte in the unique 3D interconnected hierarchical network. In addition, ex-situ XRD, SEM and TEM analyses further reveal high structure integrity of the porous TiO2 urchins during the electrochemical lithiation, leading to enhanced lithium storage stability. Moreover, we detected that some anatase nanocrystals evolved into electrochemically inactive Li1TiO2 dots (∼10 nm in size) during long-term electrochemical cycling. Our findings provide more insights for better understanding of the structure evolution and capacity decay mechanism in porous TiO2 nanostructures.
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