Article

Li-Air Rechargeable Battery Based on Metal-free Graphene Nanosheet Catalysts

Energy Technology Research Institute, National Institute of Advanced Industrial Science and Technology, Umezono 1-1-1, Central 2, Tsukuba, Ibaraki 305-8568, Japan.
ACS Nano (Impact Factor: 12.88). 03/2011; 5(4):3020-6. DOI: 10.1021/nn200084u
Source: PubMed

ABSTRACT

Metal-free graphene nanosheets (GNSs) were examined for use as air electrodes in a Li-air battery with a hybrid electrolyte. At 0.5 mA cm(-1), the GNSs showed a high discharge voltage that was near that of the 20 wt % Pt/carbon black. This was ascribed to the presence of sp(3) bonding associated with edge and defect sites in GNSs. Moreover, heat-treated GNSs not only provided a similar catalytic activity in reducing oxygen in the air, but also showed a much more-stable cycling performance than GNSs when used in a rechargeable Li-air battery. This improvement resulted from removal of adsorbed functional groups and from crystallization of the GNS surface into a graphitic structure on heat treatment.

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    • "In addition, compared with the stacked structure of graphite, such as carbon black, the graphene sheet with a twodimensional (2-D) structure allows ready access of oxygen and electrolyte from both sides, contributing to more effective mass transport and thereby higher catalytic activity. Graphene nanosheets have been applied before in aprotic Li-air batteries as aStandard Li 2 S 6 (0.2 mM) solution was also prepared as a reference and is shown in Fig. 4b.bifunctional catalyst, but the cell performance degrades fast due to the corrosion of carbon during the high-voltage charge process[47]. Here, the corrosion problem during the charge process is avoided by using the decoupled air electrodes with NiCo 2 O 4 on nickel foam as the OER electrode[24]. "
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    • "Owing to its ultra-large specific surface area, high carrier mobility and extraordinary lithium ion/atom storage capacity, graphene sheet has been considered as one of the most promising anode materials for lithium ion battery (LIB) [1] [2] [3] [4] [5] [6] [7]. However , there are two problems remained to be overcome using bare graphene sheets as anode materials [2]. "
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    • "Several different types of related rGO have been tested as the Li–air battery cathode material, such as ''normal'' rGO [17] [18], doped rGO [20] [21], and metal containing rGO [22] [23] [24] [25]. rGO cathodes have been tested for both the aprotic [17] [18] and hybrid [26] Li–air battery systems with promising results. Even though rGO has been investigated [19] [27] [28], the difference of the functional groups in the graphene oxide (GO) and their relation with the functional groups in rGO has not been explored in detail. "
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