RESUMEN
An electrolyte using 2,3,4,5,6-pentafluorophenyl methanesulfonate (PFPMS) as a versatile additive is investigated through calculating the molecular orbital energies of additives and solvents and designing the electrolyte composition, and the comparative performances of LiNi0.5Co0.2Mn0.3O2/graphite cells operating in a wide-temperature range are improved. It is revealed that PFPMS can form interfacial films on both the cathode and anode surfaces, resulting in a decrease of the cell impedance and the side reactions between the active materials and electrolyte. Compared to the cells without additive of 74.9% and those with vinylene carbonate (VC) of 76.7%, the cycling retention of the cell with 1.0 wt % PFPMS reaches 91.7% after 400 cycles at room temperature. In particular, for the high-temperature storage at 60 °C for 7 d, the cell containing 1.0 wt % PFPMS exhibits optimal capacity retention of 86.3% and capacity recovery of 90.6%; for the low-temperature discharge capacity retention at -20 °C, the cell with 1.0 wt % PFPMS maintains at 66.3% at 0.5 C, while for the cells without additive and containing 1.0 wt % VC, their retention values are 55.0 and 62.1%, respectively. The excellent cycling, wide-temperature practicability, and rate capability of the cells with PFPMS demonstrate that the electrolyte with PFPMS additive is promising for applications in LiNi0.5Co0.2Mn0.3O2/graphite batteries.
RESUMEN
In this work, a new category of anionic Gemini surfactants with a rigid space, disodium 2,2'-(1, 4-phenylene bis (methylene)) bis (alkane-1-sulfate) (CmArCm, m=8, 10, 12, 14), were developed. They showed excellent surface activity and remarkable micellization tendency in aqueous solutions as measured by the equilibrium surface tension method. It was noticed that both the surface activity and micellization ability of CmArCm were gradually strengthened upon increasing the hydrophobic chain length m. Those Gemini surfactants were employed as capping reagents to fabricate three-dimensional (3D) hierarchical silver microparticles (AgMPs) successfully even in a large-scale of gram-level. The morphological evolution of these microparticles in different conditions was investigated systematically by various techniques including scanning electron microscopy (SEM), high-resolution transmission electron microscope (HRTEM), powder X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR). The possible formation mechanism of surfactant assisted AgMPs was also proposed. It was found that the morphology of AgMPs could be tailored from nut-like, lichi-like, to coral-like microparticles by simply varying the concentration of surfactant. However, the hydrophobic chain length m of CmArCm showed a little influence on the morphology of AgMPs. Moreover, the surface-enhanced Raman scattering of Rhodamine 6G results evidently confirmed the superior surface activity of synthesized AgMPs.
