RESUMO
Here, we present K0.28MnO2·0.15H2O, which has a two-dimensional open framework, as an intercalation host for potassium ions. K0.28MnO2·0.15H2O has a layered structure consisting of edge-sharing MnO6 octahedra with a large basal spacing of â¼7.3 Å, which facilitates K+-ion mobility. Water molecules in the interlayers between the MnO2 layers play an important role as a pillar to support the structure during repetitive de/potassiation cycles, as confirmed by an operando X-ray diffraction study. As a result, the large K+ ions readily migrate into the crystal structure, resulting in satisfactory electrochemical performance in K-cells. With the aid of the structural pillar, the K0.28MnO2·0.15H2O cathode delivers a high reversible capacity of 150 mA h g-1 over 100 cycles at a rate of 0.1 C (15 mA g-1), with acceptable power capability up to 5 C-rates.
RESUMO
We measured the thermal conductivity of Araneus ventricosus' spider dragline silk using a suspended microdevice. The thermal conductivity of the silk fiber was approximately 0.4Wm-1K-1 at room temperature and gradually increased with an increasing temperature in a manner similar to that of other disordered crystals or proteins. In order to elucidate the effect of ß-sheet crystals in the silk, thermal denaturation was used to reduce the quantity of the ß-sheet crystals. A calculation with an effective medium approximation supported this measurement result showing that the thermal conductivity of ß-sheet crystals had an insignificant effect on the thermal conductivity of SDS. Additionally, the enhancement of bonding strength in a glycine-rich matrix by atomic layer deposition did not increase the thermal conductivity. Thus, this study suggests that the disordered part of the glycine-rich matrix prevented the peptide chains from being coaxially extended via the cross-linking covalent bonds.
