Sycamore-fruit-like SnO2@C nanocomposites: Rational fabrication, highly reversible capacity and superior rate capability anode material for Li storage

SnO2-based nanostructures have attracted considerable interest as promising high-capacity anode materials for lithium ion batteries (LIBs). Herein, we present a facile hydrothermal-carbonization approach to rationally fabricate a novel sycamore-fruit-like SnO2-based anode material (denoted as H7-500) for LIBs to simultaneously achieve high capacity, long-term cycling stability and ultrahigh rate capability. Structural analyses reveal that H7-500 possesses a sycamore-fruit-like hierarchical structure and is composed of 6-8 nm SnO2 nanoparticles coated with 1.7 nm thin carbon skins embedded on the surface region of 400 nm highly porous carbon spheres. The formation of sycamore-fruit-like structure is confirmed to be promoted by the Ostwald ripening. H7-500 delivers capabilities of 1242.3,1116.5, 1004.8, 878, 745.8 and 488.7 mAh . g(-1) at 0.1, 0.2, 0.5, 1, 2 and 5 A g(-1), respectively. A high capacity of 905.4 mAh . g(-1) sustains after 300 cycles at 1 A g(-1) and a capacitance of 413.4 mAh . g(-1) maintains after 1000 cycles at 5 A g(-1). Notably, H7-500 electrodes exhibit excellent sustainable stability and endurability with sustainable capacities of 177.8 mAh . g(-1) at 10 A g(-1) over 4000 cycles and 133.4 mAh . g(-1) at 20 A g(-1) over 10000 cycles, respectively. Frequently tuning the rate between 0.1 and 10 A g(-1) has no effect on the capacity and cycling stability of H7-500. The sycamore-fruit-like H7-500 shows excellent structural stability during the charge/discharge process. The unique structure not only solves the conventional problem of pulverization, particle aggregation and volume changes but also enhances structural integrity and the reversible reaction, and accelerates the reaction rate. These features render the materials excellent electrochemical performances with high capacity, superior rate capability and long-term cycling stability. The present results may also provide insights into the ongoing extensive endeavor to improve the properties of other electrode materials. (C) 2019 Elsevier Ltd. All rights reserved.