Hierarchically structured C@SnO2@C nanofiber bundles with high stability and effective ambipolar diffusion kinetics for high-performance Li-ion batteries
The implementation of transition metal oxides as anode materials for Li-ion batteries (LIBs) has been largely hindered by their huge volumetric change during the lithiation/delithiation cycles, which generally leads to electrode pulverization with a fast capacity fading. Slow ambipolar (ionic and electronic) diffusion kinetics are another disadvantage suffered by transition metal oxides. This intrinsic drawback inevitably causes a poor rate capability of transition metal oxides. SnO2 is an attractive candidate as an anode material for next-generation LIBs due to its high theoretical capacity, low cost and improved safety. In this article, a sandwich-structured carbon nanofiber@SnO2@carbon coating (C@SnO2@C) nanofiber bundle was facilely prepared by using collagen fiber, a typical fibrous protein, as the biotemplate as well as the carbon source. The hierarchical architecture of the C@SnO2@C nanofiber bundle guaranteed a good match between the electron transport kinetics and the Li+ diffusion kinetics, thus realizing efficient ambipolar diffusion. Another merit that originated from the configuration of the C@SnO2@C nanofiber bundle was the unique “breath” behavior, which effectively accommodated the volume change of SnO2 so as to ensure structural integrity with the formation of the smooth and thin solid electrolyte interphase (SEI). The C@SnO2@C nanofiber bundle showed obvious advantages both in rate capability and cycling stability as compared with those of conventional carbon/SnO2 nanocomposites, including a C@SnO2 nanofiber bundle and SnO2@C nanofiber bundle. Our strategy developed here may be extended for the synthesis of other high-performance anode materials, especially for transition metal oxides that suffered from poor electrical conductivity and/or huge volumetric change.