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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A quasi-solid-state sodium-ion capacitor is demonstrated with nanoporous disordered carbon and macroporous graphene as the negative and positive electrodes, respectively, using a sodium-ion-conducting gel polymer electrolyte. It can operate at a cell voltage as high as 4.2 V with an energy density of record high 168 W h kg(-1).

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A nanocomposite of molybdenum trioxide (a-MoO 3 ) nanobelts coated with polypyrrole has been fabricated by a simple in situ polymerization route. The structure, morphology and electrochemical performance of the nanocomposite were investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and electrochemical measurements. It was found that the polypyrrole acted as a conducting matrix and a coating agent, which effectively improves the conductivity of the MoO 3 nanobelts and inhibits the dissolution of molybdenum ions during cycling. The supercapacitor based on the PPy@MoO 3 nanocomposite as the anode, activated carbon as the cathode and 0.5 M K 2 SO 4 aqueous solution as the electrolyte exhibits better rate capability as well as excellent cycling performance compared to the virginal MoO 3 .

Nanoporous selenium was prepared by a simple mechanical method adopting nano-CaCO3 as a template. When used as a cathode, it can exhibit relatively high capacity and good cycling behaviour. These results present great promise for this new cathode material for rechargeable lithium batteries of high energy density.

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