Abstract
Biomass derived carbon materials have been widely used as electrode materials; however, in most cases, only electrical double layer capacitance (EDLC) is utilized and therefore, only low energy density can be achieved. Herein, we report on redox-active carbon spheres that can be simply synthesized from earth-abundant glucose via a hydrothermal process. These carbon spheres exhibit a specific capacity of ∼210 mA h gCS(-1), with high redox potentials in the voltage range of 2.2-3.7 V vs. Li, when used as positive electrode in lithium cells. Free-standing, flexible composite films consisting of the carbon spheres and few-walled carbon nanotubes deliver high specific capacities up to ∼155 mA h gelectrode(-1) with no obvious capacity fading up to 10,000 cycles, proposing to be promising positive electrodes for lithium-ion batteries or capacitors. Furthermore, considering that the carbon spheres were obtained in an aqueous glucose solution and no toxic or hazardous reagents were used, this process opens up a green and sustainable method for designing high performance, environmentally-friendly energy storage devices.
Highlights
Replacing fossil fuels with various types of clean and renewable energy sources is vital in order to effectuate the world’s sustainable development.[1]
The carbon spheres were prepared from an aqueous solution of glucose (3 mg mL−1) via a hydrothermal carbonization (HTC) process at 200 °C for 18 h, during which the transparent glucose solution was transformed into a brownish colloidal dispersion (Fig. 1a)
The sizes of synthesized carbon spheres are mainly in the range of 60–100 nm as shown in Fig. S1c.† Free-standing composite films were fabricated via filtering the aqueous mixture of carbon spheres and few-walled carbon nanotubes (FWNTs), where sub-millimeter long FWNTs were employed as a conductive agent (Fig. 1c inset)
Summary
Replacing fossil fuels with various types of clean and renewable energy sources is vital in order to effectuate the world’s sustainable development.[1]. These carbon spheres exhibit a specific capacity of ∼210 mA h gCS−1, with high redox potentials in the voltage range of 2.2–3.7 V vs Li, when used as positive electrode in lithium cells.
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