Preparation of coaxial Sn-Co alloy/CNFs 3D freestanding membrane anode by electrochemical Co-deposition for lithium-ion batteries

2019 
Coaxial Sn-Co alloy/CNFs nanocomposite three-dimensional (3D) membrane is synthesized via a facile electrochemical co-deposition method using the CNFs membrane with 3D network structure as the flexible freestanding substrate. The as-synthesized nanocomposite membrane is characterized using scanning electron microscopy (SEM), transition electron microscopy (TEM), energy dispersive spectrometer (EDS), and X-ray diffraction (XRD). The results reveal that nanoscaled Sn-Co alloy layer is uniformly covered onto the surface of CNFs; the thickness of Sn-Co alloy shell layer can be controlled to about 60–110 nm. EDS result exhibits that the atomic percentage of Sn, Co, and C in the as-synthesized nanocomposite membrane is 53.25 at%, 20.19 at%, and 26.56 at%, respectively. The nanocomposite membrane with the unique 3D network structure is flexible after Sn-Co alloy deposition. Its electrochemical performances are investigated by the cyclic voltammetry, galvanostatic charge/discharge cycling, and rate cycles. Its discharge specific capacity for 2nd and 50th cycle is 1260 mAh g−1 and 788 mAh g−1, respectively, and the capacity attenuation ratio is about 0.75%/cycle at a current density of 50 mA g−1. The excellent electrochemical performance of the coaxial Sn-Co alloy/CNFs nanocomposite 3D membrane is mainly contributed to the high mechanical strength, good flexibility, and high electrical conductivity of CNFs substrate, which offers a possible solution of Sn volume change and poor electronic conduction during charge/discharge process.
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