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

KGaA, Weinheim. 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 (TiO2-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 Li4.4Sn alloy is inserted into the pores surrounding the initial Sn nanoparticles in TiO2-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 TiO2-x-C substrate, resulting in many smaller Sn nanoparticles remaining in the pores. Batteries containing these porous TiO2-x-C-Sn nanofibers exhibit a high capacity of 957 mAh g-1after 200 cycles at 0.1 A g-1and can cycle over 10 000 times at 3 A g-1while 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.