Search

Manganese oxide (MnO 2) is proven to be an efficient cathode material in zinc-ion batteries (ZIBs). However, its poor electronic conductivity strongly limits the performance of Zn–MnO 2 batteries. In order to improve performance beyond typical graphitic carbon additives, a binary conductive additive, a combination of carbon nanohorns (CNHs) and carbon nanotubes (CNTs), is added into the MnO 2 electrode to establish high-speed electron-channels in the CNTs/CNHs network with an efficient "line-to-surface-to-point" microstructure. In this electrode, the high aspect-ratio CNTs create a conducting highway for the collected charges, while the CNHs provide extra surface area for electron transfer. Moreover, the specific surface area of the electrode increases due to the introduction of CNHs, which increases the Zn2+ diffusion coefficient. As a result, the corresponding battery reaches a high specific capacity (343 mAh g−1 at 0.3 A g−1), excellent rate performance (191.3 mAh g−1 at 3 A g−1) and long-life cycle. Moreover, it achieves an admirable specific energy density of 466 W h kg−1, together with a peak power density of 9.4 kW kg−1 (normalized to the weight of MnO 2), the performance of which is among the best reported ZIBs. This work reveals new pathways to improve the performance of MnO 2 cathodes for ZIBs. Image 1 [ABSTRACT FROM AUTHOR]

We present a stable inkjet printable graphene ink, formulated in isopropyl alcohol via liquid phase exfoliation of chemically pristine graphite with a polymer stabilizer. The rheology and low deposition temperature of the ink allow uniform printing. We use the graphene ink to fabricate counter electrodes (CE) for natural and ruthenium-based dye-sensitized solar cells (DSSCs). The repeatability of the printing process for the CEs is demonstrated through an array of inkjet-printed graphene electrodes, with ∼5% standard deviation in the sheet resistance. As photosensitizers, we investigate natural tropical dye extracts from Pennisetum glaucum , Hibiscus sabdariffa and Caesalpinia pulcherrima . Among the three natural dyes, we find extracts from C . pulcherrima exhibit the best performance, with ∼0.9% conversion efficiency using a printed graphene CE and a comparable ∼1.1% efficiency using a platinum (Pt) CE. When used with N719 dye, the inkjet-printed graphene CE shows a ∼3.0% conversion efficiency, compared to ∼4.4% obtained using Pt CEs. Our results show that inkjet printable graphene inks, without any chemical functionalization, offers a flexible and scalable fabrication route, with a material cost of only ∼2.7% of the equivalent solution processed Pt-based electrodes. [ABSTRACT FROM AUTHOR]