A novel free-standing type cathode of rechargeable Li-O 2 battery composed of only Co 3 O 4 catalyst and Ni foam current collector was designed and realized by a simple chemical deposition reaction. The carbon and binder are no longer necessary for the air electrode. The new air electrode was found to yield obviously higher specific capacity and improved cycle efficiency than the conventional carbonsupported one with almost the highest discharge voltage (2.95 V), the lowest charge voltage (3.44 V), the highest specific capacity (4000 mAh g À1 cathode ) and the minimum capacity fading among the Li-O 2 batteries reported to date. During its discharge process, the discharge products would deposit at the surface and in the pores of the free-standing catalysts. The improved performance was attributed to the abundant available catalytic sites of the particularly structured air electrode, the intimate contact of the discharge product with the catalyst, the effective suppression of the volume expansion in the electrode during subsequent deposition/decomposition of the discharge products, the good adhesion of the catalyst to the current collector, and the open pore system for unrestricted access of the reactant molecules to and from active sites of the catalysts. Furthermore, EIS study pointed out the intrinsic distinction resulting in the different performance between the new electrode and the conventional carbon-supported electrode. The new free-standing type electrode represents a critical step toward developing high-performance Li-O 2 batteries.

An aqueous rechargeable battery system is assembled by using metallic zinc and Na(0.95)MnO2 as the negative and positive electrodes, respectively. It is cheap and environmentally friendly, and its energy density is 78 Wh kg(-1). Its cycling performance is very good with only 8% capacity loss after 1000 cycles at 4 C between 1 and 2 V.

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Porous graphene oxide foams were prepared by unidirectional freeze-drying technology and used to investigate the reaction between graphene oxide (GO) and SO 2 . The structure and composition changes of the graphene oxide were monitored by X-ray photoelectron spectrometry (XPS), Raman, X-ray diffraction (XRD), Thermogravimetric analysis (TGA), and ultraviolet-visible spectroscopy (UV-vis), and the product of the reaction was analyzed by an EDTA titration. The results show that SO 2 was oxidized to SO 3 and the GO was reduced. GO not only acts as the oxidant in the reaction, but also as the catalyst to catalyze the reaction of SO 2 and O 2 to form SO 3 . This catalytic action is more active in the aqueous GO suspensions than in the foams. The GO foams can adsorb SO 2 and convert it to SO 3 which then changes to SO 4 2À on contact with water. This offers a new effective method of converting noisome SO 2 gas to SO 3 at room temperature.