Simultaneous Polymerization Enabled the Confinement of Size-Adjustable TiO2 Nanocrystals in S-Doped Carbons for High-Rate Anode Materials

Homogeneous confinement of metal oxide nanoparticles into the heteroatom-doped carbon matrix is highly desirable but remains challenging to develop high-performance anode materials. Herein, a facile simultaneous polymerization of 2-thiophenemethanol (ThM) and titanium ethoxide (TTEO) is proposed to incorporate ultrafine anatase TiO2 nanocrystals into the continuous S-doped carbon framework by carbonizing the as-produced TiO2/poly(2-thiophenemethanol) composites. This in situ crafting process spatially suppresses the growth of TiO2 by the polymerization of ThM, thus producing size-adjustable TiO2 nanocrystals (5-50 nm) by tailoring the ratio of TTEO to ThM. It is found that smaller TiO2 nanocrystals are generated using the lower TTEO-to-ThM ratio. When used as lithium-ion batteries (LIBs) anode, TiO2/S-doped carbon (TSC) shows larger reversible capacity, superior rate capability, and better cycling stability compared to pure TiO2. A typical TSC with the smallest TiO2 nanocrystals (8 nm) shows the reversible capacity as high as 386 mAh g(-1) at 50 mA g(-1), and retains 55% of initial capacity at 500 mA g(-1), and 96.8% capacity after 500 cycles at 1000 mA g(-1). The excellent electrochemical performance is attributed to the shortened ion diffusion path of ultrafine TiO2 and the improved electronic conductivity, structural stability, and surface/interface nature by the S-doped carbon matrix.