Inserting Sn Nanoparticles into the Pores of TiO_2−x–C Nanofibers by Lithiation

Tin holds promise as an anode material for lithium‐ion batteries (LIBs) because of its high theoretical capacity, but its cycle life is limited by structural degradation. Herein, a novel approach is exploited to insert Sn nanoparticles into the pores of highly stable titanium dioxide–carbon (TiO_2−x–C) nanofiber substrates that can effectively localize the postformed smaller Sn nanoparticles, thereby address the problem of structural degradation, and thus achieve improved anode performance. During first lithiation, a Li_4.4Sn alloy is inserted into the pores surrounding the initial Sn nanoparticles in TiO_2−x–C nanofibers by its large volume expansion. Thereafter, the original Sn nanoparticle with a diameter of about 150 nm cannot be recovered by the delithiation because of the surface absorption between inserted Sn nanoparticles and the TiO_2−x–C substrate, resulting in many smaller Sn nanoparticles remaining in the pores. Batteries containing these porous TiO_2−x–C–Sn nanofibers exhibit a high capacity of 957 mAh g⁻¹ after 200 cycles at 0.1 A g⁻¹ and can cycle over 10 000 times at 3 A g⁻¹ while retaining 82.3% of their capacity, which represents the longest cycling life of Sn‐based anodes for LIBs so far. This interesting method can provide new avenues for other high‐capacity anode material systems that suffer from significant volume expansion.