Flexible high energy density zinc-ion batteries enabled by binder-free MnO_(2)/reduced graphene oxide electrode

We demonstrate a rechargeable zinc-ion battery with high energy density and cyclability using MnO_(2)and reduced graphene oxide(MnO_(2)/rGO)electrode.The flexible and binder free electrode,with high MnO_(2)mass ratio(80 wt%of MnO_(2)),is fabricated using vacuum filtration without any additional additives other than rGO.Compared to batteries with conventional MnO_(2)electrodes,the Zn-MnO_(2)/rGO battery shows a significant enhanced capacity(332.2 mAh g^(-1)at 0.3 A g^(-1)),improved rate capability(172.3 mAh g^(-1)at 6 A g^(-1))and cyclability.The capacity retention remains 96%after 500 charge/discharge cycles at 6 A g^(-1).The high MnO_(2)mass ratio makes MnO_(2)/rGO electrode advantageous when the capacity is normalized to the whole electrode,particularly at high rates.The calculated gravimetric energy density of Zn-MnO_(2)/rGO battery is 33.17Wh kg^(-1),which is comparable to the existing commercial lead-acid batteries(30-40Wh kg^(-1)).Furthermore,the discharge profile and capacity of our Zn-MnO_(2)/rGO battery shows no deterioration during bending test,indicating good flexibility.As a result,zinc-ion battery is believed to be a promising technology for powering next generation flexible electronics.

The influence of H_(2)O and O_(2) on the optoelectronic properties of inverted quantum-dot light-emitting diodes

The influence of H_(2)O and O_(2) on the performances of Mg-doped zinc oxide (ZnMgO) and ZnMgO-based inverted quantum-dot light-emitting diodes (QLEDs) are studied. With the involvement of H_(2)O from ambience, ZnMgO exhibits a high conductivity, whereas the resultant QLEDs show a low efficiency. The efficiency of QLEDs can be enhanced by annealing ZnMgO in H_(2)O-free glovebox;however, the uniformity and the current of the devices are degraded due to the presence of O_(2), which adsorbs on the surface of ZnMgO and captures the free electrons of ZnMgO. By exposing the devices with ultraviolet (UV) irradiation, the adsorbed O_(2) can be released, consequently leading to the increase of driving current. Our work discloses the influence of the annealing ambience on the conductivity of ZnMgO, and reveals the interaction of H_(2)O/O_(2) and UV with the ZnMgO and its effect on the performance of the resultant inverted QLEDs, which could help the community to better understand the mechanisms of ZnMgO-based QLEDs.