Abstract
New and novel 3D hierarchical porous graphene aerogels (HPGA) with uniform and tunable meso-pores (e.g., 21 and 53 nm) on graphene nanosheets (GNS) were prepared by a hydrothermal self-assembly process and an in-situ carbothermal reaction. The size and distribution of the meso-pores on the individual GNS were uniform and could be tuned by controlling the sizes of the Co3O4 NPs used in the hydrothermal reaction. This unique architecture of HPGA prevents the stacking of GNS and promises more electrochemically active sites that enhance the electrochemical storage level significantly. HPGA, as a lithium-ion battery anode, exhibited superior electrochemical performance, including a high reversible specific capacity of 1100 mAh/g at a current density of 0.1 A/g, outstanding cycling stability and excellent rate performance. Even at a large current density of 20 A/g, the reversible capacity was retained at 300 mAh/g, which is larger than that of most porous carbon-based anodes reported, suggesting it to be a promising candidate for energy storage. The proposed 3D HPGA is expected to provide an important platform that can promote the development of 3D topological porous systems in a range of energy storage and generation fields.
Highlights
Sites for hosting lithium[10,11]
By combining the synergistic effects of the macro-porosity of the graphene aerogel (GA) network architecture and the meso-porosity of graphene nanosheets (GNS), the as-prepared hierarchical porous graphene aerogel (HPGA) samples possessed a high density of ion diffusion channels that facilitate charge transport and storage at high rates, which results in high Li ions storage capacities for more than 100 cycles of continuous charge/discharge (1100 mAh/g at current density of 0.1 A/g)
The oxygenated functionalities decreased significantly and the π -conjugation was largely restored which results in increased incompatibility with polar solvents and π − π stacking interaction[33,34]
Summary
Sites for hosting lithium[10,11]. the diffusion distance of lithium ions in nanostructured carbon is short, leading to improved rate performance[7,12]. A better design of a graphene electrode material is essential to further boosting the performance of graphene in LIBs. Compared to 2D graphene nanosheets (GNS), micro- or meso-porous GNS has a larger specific surface area and a larger number of additional defects in the basal plane of graphene, which increases the number of electrochemical active reversible storage sites[16,17,18,19,20,21]. Numerous novel approaches have been explored to inhibit the aggregation and stacking of GNS30–33 This issue may be addressed by the recently developed 3D graphene aerogel (GA), which is assembled by cross-linked individual graphene sheets and exhibiting a continuously interconnected porous network, large surface area, low mass density, and high electrical conductivity[34,35]. HPGA may be an effective electrode material for other high-performance energy storage and generation devices
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