In Situ synthesis of Three-Dimensional Self-Assembled SnO2 - Reduced Graphene Oxide Architecture for Lithium Ion Batteries
Authors: Kim Hyun-Kyung , Kim Kwang-Bum , Roh Kwang Chul , Jeong Jun Hui , Roh Ha-Kyung 
Published: February 2020

The structure of graphene, a single layer of carbon atoms patterned in a hexagonal lattice, results in an unusual combination of characteristics including outstanding electronic properties, high thermal conductivity, good optical properties, high mechanical strength, and a large surface area. As such, graphene has attracted considerable attention worldwide for potential applications in sensors, catalysis, energy-storage devices, and environmental fields. Although most of this previous research has focused on two-dimensional (2-D) specimens and devices,1 these 2-D graphene sheets must be integrated into macroscopic 3-D structures to take full advantage of their properties and associated benefits.2

Of the available techniques for integrating nanostructured building blocks into macroscopic materials, the fabrication of self-assembled, 3-D graphene structures has been recognized as one of the most effective, as it is capable of harnessing nanoscale properties to provide novel functionalities of hierarchically structured macroscopic devices. Furthermore, superstructures assembled in this way exhibit unique collective physiochemical properties different from those of the individual components and bulk material, which help enrich the variety of graphene-based materials and broaden their capacity for practical application.3A number of different interactions such as dipole interactions, electrostatic attraction or repulsion, hydrophilic/hydrophobic interactions, and hydrogen bonding have also been utilized in the self-assembly process itself.
Studies pertaining to composites of graphene and nanoparticles have flourished in recent years, as such materials combine the advantages of both graphene and nanoparticles and therefore have potential for application in catalysis, sensors, and energy fields.4 More recently, the capture of pre-prepared metal oxide nanoparticles or metal salts in 3-D graphene networks has been reported as possible with the assistance of a suitable reducing agent (NaHSO3, Na2S, vitamin C, HI, and hydroquinone).5

In most previous studies, nanometer-sized 3-D structured metal oxide (MO)–graphene has been synthesized by physically mixing the MO with graphene oxide (GO), dispersing it in an aqueous solution, and then adding a reducing agent. In this process, MO particles are randomly captured and aggregated between the graphene sheets, which significantly inhibits their nanoscale effects.6 Consequently, most such materials are instead prepared from 2-D graphene nanosheets onto which nanoparticles have been deposited or adsorbed, and there are still very few reports on different routes for directly preparing 3-D graphene–nanoparticle composites.7

With this in mind, we herein report on a self-assembled, 3-D RGO architecture that is prepared with electrochemically active SnO2 interfacially anchored between highly conductive RGO structures. This was achieved with a simple one-pot synthesis in which a SnCl2 was used not only as a reducing agent to transform GO into highly conductive 3-D RGO but also as a precursor to form a 3-D SnO2 structure under carefully controlled reduction conditions. The 3D SnO2-RGO composite synthesized in this manner is electrochemically assessed for use as a binder-free anode in high-rate Li-ion batteries.
More details on the synthetic procedure, electrochemical and structural properties will be presented at the meeting.
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