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A flexible quasi-solid-state Ni-Zn battery is developed by using tiny ZnO nanoparticles and porous ultrathin NiO nanoflakes conformally deposited on hierar chical carbon-cloth-carbon-fiber (CC-CF) as the anode (CC-CF@ZnO) and cathode (CC-CF@NiO), respectively. The device is able to deliver high performance (absence of Zn dendrite), superior to previous reports on aqueous Ni-Zn batteries and other flexible electrochemical energy-storage devices.

First-principles calculations are performed to investigate the interaction of physisorbed small molecules, including CO, H 2 , H 2 O, NH 3 , NO, NO 2 , and O 2 , with phosphorene, and their energetics, charge transfer, and magnetic moment are evaluated on the basis of dispersion corrected density functional theory. Our calculations reveal that CO, H 2 , H 2 O and NH 3 molecules act as a weak donor, whereas O 2 and NO 2 act as a strong acceptor. While NO molecule donates electrons to graphene, it receives electrons from phosphorene. Among all the investigated molecules, NO 2 has the strongest interaction through hybridizing its frontier orbitals with the 3p orbital of phosphorene. The nontrivial and distinct charge transfer occurring between phosphorene and these physisorbed molecules not only renders phosphorene promising for application as a gas sensor, but also provides an effective route to modulating the polarity and density of carriers in phosphorene. In addition, the binding energy of H 2 on phosphorene is found to be 0.13 eV/H 2 , indicating that phosphorene is suitable for both stable room-temperature hydrogen storage and its subsequent facile release.

Li-ion batteries, which restrict their wide applications, especially for environments that require mechanical stability and extreme conditions. [8][9][10][11] Alternatively, fl exible supercapacitors, especially quasi-solid state ones, have received considerate attention recently. [12][13][14][15] Although some of the fl exible supercapacitors so far reported can provide high power density and long-term stability, the energy density is relatively low. [16][17][18][19] Thus great challenges still remain in developing the overall high-performance solid/quasi-solid-state fl exible electrochemical energy storage devices with both high energy density and high power density. [20][21][22][23][24] As a typical type of traditional aqueous rechargeable batteries, Ni/Fe battery has been studied for a long period of time, because of its relatively high safety, lowcost, and high energy density. [ 25,26 ] In general, it can provide better safety and lower cost as compared with Li-ion battery; its energy density is higher in contrast to that of common supercapacitors. However, the low power density and poor cycling ability have limited the wide application of Ni/Fe battery. [ 27 ] On the other hand, recent development of nanomaterials and nanotechnology has enabled advanced electrode materials that can greatly enhance the performance of Ni/Fe battery. For example, by proper synergizing of nanostructured active materials (FeO x , NiO, or Ni(OH) 2 ) with carbonaceous materials (such as graphene, carbon nanofi bers, and carbon nanotubes (CNTs)), the power density of Ni/Fe battery can be greatly enhanced. [ 28,29 ] In some of these previous studies, the active materials are controlled in powder forms, such that carbon black and polymer additives have been employed in electrodes, where heavy metal foils or foams are used as the current collectors. The gravimetric/volumetric capacity of the full cell is therefore limited and the cell can be hardly fl exible. Some other works have focused on fl exible electrode materials for Ni/Fe batteries, where the device is assembled using liquid electrolytes. [ 30,31 ] In addition to the overall electrochemical performance, it would be a plus to eliminate liquid electrolytes, such that the safety issue in connection with the potential leakage problem can be solved. In order to promote the application of Ni/Fe batteries as a class of energy storage components for fl exible electronics Aqueous Ni/Fe batteries have great potential as fl exible energy storage devices, owing to their low cost, low toxicity, high safety, and high energy density. However, the poor cycling stability has limited the widely expected application of Ni/Fe batteries, while the use of heavy metal substrates cannot meet the basic requirement for fl exible devices. In this work, a fl exible type of solid-state Ni/Fe batteries with high energy and power densities is rationally developed using needle-like Fe 3 O 4 and fl ake-like NiO directly grown on carbon cloth/carbon nanofi ber (CC-CF) matrix as the anode and cathode, respecti...

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