Co-Fe layered double hydroxides (Co1−xFex LDHs) were synthesized by a chemical co-precipitation method. It was found that the molor ratio of Co to Fe had a significant effect on the electrochemical activity. The specific capacitance of 869 F g−1 was achieved when the molor ratio of Co to Fe was equal to 0.74:0.26. The Co0.74Fe0.26 LDH sample had a BET specific surface area of 202.9 m2 g−1 and total pore volume of 0.6 cm3 g−1, which led to the high liquid–solid interfacial area and further increased the utilization of the active materials. Additionally, the Co0.74Fe0.26 LDH electrode exhibited a good electrochemical stability with beyond 99.5% of the initial capacitance over 1000 consecutive cycles at 1 A g−1. It is a promising electrode material for supercapacitor.
Due to the hydrophobic nature of multiwalled carbon nanotube (MWNT), sodium dodecylbenzene sulfonate (SDBS) was adopted as a surfactant to synthesize a well-dispersed, homogeneous MWNT aqueous suspension. By simple stirring mixing of the resultant MWNT suspension with nano-sulfur aqueous suspension, a novel porous sulfur/multiwalled carbon nanotube composite (S/MWNT) was synthesized. This preparation method based on the suspension mixing possesses the advantages of simplicity and low cost. Homogeneous dispersion and integration of MWNT in the composite results in a porous, highly conductive and mechanically flexible framework with enhanced electronic conductivity and ability to absorb the polysulfides into its porous structure. The cell with this S/MWNT composite cathode demonstrates a high reversibility, resulting in a stable reversible specific discharge capacity of 708 mAh g−1 after 100 cycles at 0.1 C. Furthermore, the S/MWNT composite cathode with sulfur content of 62.5 wt% exhibits a good rate capability with discharge capacities of 946, 780 and 516 mAh g−1 at 0.5, 1 and 1.5 C, respectively.
Lithium-ion secondary cells are widely used for the space applications, today. Among these applications, REIMEI, which was launched in 2005, was one of the first satellites using lithium-ion battery. The off-the-shelf type cells designed using spinel manganese oxide for the positive and the graphitized carbon for the negative electrode were used. The cell case was made of aluminum laminated film and the structure was reinforced by the aluminum case filled with epoxy resin. Today, ten years has passed, and the battery experienced 55,000 cycles for charge and discharge. The current distribution between two batteries almost coincided together even after the long term operation, which revealed the stable performance of the lithium-ion secondary cells under the microgravity in space.
The effect of addtives, such as pyridine-4-carbohydrazide (P4CH) and 1,10-phenanthroline (PH), on the electrodeposition efficiency and brightness of aluminum (Al) prepared by a constant-current deposition from baths of aluminum chloride (AlCl3)-1-ethyl-3-methylimidazolium chloride (EMIC)-toluene was examined using a scanning electron microscope (SEM), an atomic force microscope (AFM) and X-ray diffraction (XRD). P4CH achieved higher surface brightness of the electrodeposited Al than one of the Al film prepared with PH as an additive. The relationship between surface brightness and surface roughness could be confirmed with the prepared Al films. P4CH strongly adsorbs onto the deposited Al surface than PH, as the result, smooth Al surface was formed under the influence of adsorbed P4CH on deposited Al surfaces in AlCl3-EMIC-toluene-P4CH.