Promotional role of Li4Ti5O12 as Li+ conductor and structural stabilizer on Sn@C anode cyclability

Nano-Sn confined to matrixes for fabricating high capacity and long cycle life anodes has attracted extensive attention in recent years, but using Li+ conductor as structure stabilizer to construct matrixes have not been studied yet. Sn-based anodes using spinel Li4Ti5O12 as Li+ conductor and structure stabilizer can prolong the cycle life of electrodes, which is due to “zero strain” property and high Li+ conductivity coefficient of Li4Ti5O12. Herein, spherical (nano-Sn/Li4Ti5O12)@C was designed, synthesized and investigated, which was labeled as (n-Sn/L)@C. Nano-Sn and nano-Li4Ti5O12 pieces were mixed uniformly in inner carbon shell, where some vacuum space was beneficial for Sn expanding/shrinking during Li+ insertion/extraction. Moreover, Li+ diffusion coefficient of (n-Sn/L)@C-1 and (n-Sn/L)@C-2 was high as 6.09 × 10−8 and 9.47 × 10−9 cm2 s−1, whereas the value of Sn@C was 7.54 × 10−10 cm2 s−1. The charge capacity (corresponding to the reversible capacity on full cell) loss of per cycle of (n-Sn/L)@C-1 and (n-Sn/L)@C-2 from 1st to 350th cycle was only 0.081% and 0.094% at 500 mA g−1, while the value of Sn@C was 0.160%. The enhanced electrochemical performances of (n-Sn/L)@C benefited from intimate contact of nano-Li4Ti5O12 and nano-Sn within the carbon shell, and high Li+ conductivity of Li4Ti5O12.