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 TiO 2 nanocrystals into the continuous S‐doped carbon framework by carbonizing the as‐produced TiO 2 /poly(2‐thiophenemethanol) composites. This in situ crafting process spatially suppresses the growth of TiO 2 by the polymerization of ThM, thus producing size‐adjustable TiO 2 nanocrystals (5–50 nm) by tailoring the ratio of TTEO to ThM. It is found that smaller TiO 2 nanocrystals are generated using the lower TTEO‐to‐ThM ratio. When used as lithium‐ion batteries (LIBs) anode, TiO 2 /S‐doped carbon (TSC) shows larger reversible capacity, superior rate capability, and better cycling stability compared to pure TiO 2 . A typical TSC with the smallest TiO 2 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 TiO 2 and the improved electronic conductivity, structural stability, and surface/interface nature by the S‐doped carbon matrix.