As a promising alloy-type anode material for rechargeable batteries, the metal germanium (Ge) shows high capacity, but it suffers from a fast capacity fading problem caused by a large volume expansion during lithiation/delithiation cycles. In this study, via a facile electrospinning method, we optimized the combination structure of Ge quantum dots (QDs) and carbon nanofibers (CNFs). Specifically, Ge QDs with a diameter of 4-7 nm were highly dispersed in porous (pore size 10-150 nm) CNFs. The hybridized Ge/CNF nanocomposite exhibited remarkable Li storage performances such as high reversible capacity (1204 mA h g-1 at a current density of 200 mA g-1), high capacity retention (87.1% after 100 cycles) and excellent rate property (760 mA h g-1 at 3000 mA g-1). The improved electrochemical performance was due to the synergistic effects of Ge QDs and carbon nanofibers; this effectively alleviated the volume expansion problem, prevented the agglomeration of Ge, maintained the structural stability of the nanocomposite, and improved the electrode kinetics of diffusion of Li ions.
Inspired by the biological metabolic process, some biomolecules with reversible redox functional groups have been used as promising electrode materials for rechargeable batteries, supercapacitors and other charge-storage devices. Although these biomolecule-based electrode materials possess remarkable beneficial properties, their controllable synthesis and morphology-related properties have been rarely studied. Herein, one dimensional nanostructures based on juglone biomolecules have been successfully fabricated by an antisolvent crystallization and self-assembly method. Moreover, the size effect on their electrochemical charge-storage properties has been investigated. It reveals that the diameters of the one dimensional nanostructure determine their electron/ion transport properties, and the juglone nanowires achieve a higher specific capacitance and rate capability. This work will promote the development of environmentally friendly and high-efficiency energy storage electrode materials.Currently, the development of high-performance electrochemical energy-storage materials and devices is attracting intensive interest. Conventional electrode materials involving transition metal compounds, 1-4 elementary substances, 5-8 and conductive polymers, 9-12 with superior charge storage properties have been widely investigated. However, the poor biocompatibility, rising prices and depletion issues limit their sustainable applications due to their intrinsic material properties. 13 Thus, exploring naturally abundant and renewable charge-storage materials with promising electrochemical performance is of great signicance. In the biological system, its metabolic process mainly relies on ions transport and energy exchanges of redox-active biomolecules with special functional groups such as carbonyl groups, carboxyl groups, and pteridine centres. 14 Due to their abundance, sustainability, environmental benignity, these renewable and nature-derivable biomolecules with well-dened charge-storage behaviors are ideal alternatives to conventional electrode materials for the next-generation green energy-storage devices. [15][16][17] For instance, biomolecules such as lignin, 18 melanin, 19 riboavin, 20 juglone 21 and humic acid 22 have been demonstrated as promising electrode materials for the rechargeable batteries, supercapacitors and other charge-storage devices. Although these biomolecule-based electrode materials possess remarkable benecial properties, they are still confronted with several serious problems of poor conductivity and high electrochemical reaction impedance. 23 For some conventional inorganic and organic active electrode materials, decreasing their size has been demonstrated to be effective strategies to enhance the electrochemical reaction kinetics by exposing more active sites to electrolytes and conductive agent. 8,24,25 These results have strongly motivated us to develop biomolecule-based nanostructures, and investigated their sizecorrelative charge storage behavior. 26,27 Herein, one dimensional (1D) nanostruc...
A facile green solution route using only GeO2 powder, graphene oxide and purified water has been developed to prepare a GeO2/graphene composite, in which the GeO2 particles are wrapped in graphene nanosheets.
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