Encapsulating Sn-Cu alloy particles into carbon nanofibers as improved performance anodes for lithium-ion batteries

The SnCu-SiO 2 @CNFs composite nanofibers are successfully fabricated by electrospinning and subsequent heat treatments, in which the Sn-Cu alloy particles are uniformly confined in carbon nanofibers (CNFs) in the presence of SiO 2 . The characterization results show that incorporating SiO 2 into the CNFs matrix can mitigate the problem of the phase separation between Sn-Cu alloy particles and CNFs and increase the fibrous structural integrity of the composite electrodes. Importantly, the SnCu-SiO 2 @CNFs-1.0 composite electrode displays the improved electrochemical performance when the amount of Cu(Ac) 2 is controlled at 1.0 mmol, in which the discharge specific capacity of the electrode not only delivers 501.8 mAh/g after 100 cycles at 100 mA/g, but also retains 467.4 mAh/g after rate cycles when the current density is abruptly recovered to 100 mA/g. Moreover, the SnCu-SiO 2 @CNFs-1.0 electrode can possess an enhanced Li + diffusion coefficient of approximately 1.58 × 10 −16 cm 2 s −1 and a high Warburg coefficient of 568.9 Ω cm 2 s −0.5 at room temperature. The enhanced electrochemical performance can be partly ascribed to the complete encapsulation of Sn-Cu alloy particles by the CNFs matrix, and partly to the promotion of the over-all electronic conductivity. Furthermore, the flexible and conductive CNFs matrix and the stable Cu 6 Sn 5 phase can conjoinedly accommodate the volume change of the electrodes during charge/discharge processes. Therefore, the facile strategy for encapsulating Sn-Cu alloy particles into CNFs may offer some a prospective instruction for the alloy anodes in the field of energy storage.