Nguyen Dang Nam

Triethyl and tributyl phosphite as flame-retarding additives in Li-ion batteries

This study examined the influence of triethyl and tributyl phosphite (TEP and TBP) additives on the electrochemical performance of lithium-ion cells. The cell performance of the TEP- and TBP-containing electrolytes was evaluated by cyclic voltammetry, thermogravimetric analysis, electrochemical impedance spectroscopy, Fourier transform infrared spectroscopy and scanning electron microscopy. The flammability of the electrolytes was also investigated by measuring the self-extinguishing time of the electrolytes. The results showed that the TEP and TBP additives suppressed the flammability of the electrolyte, with a significant improvement in cell performance observed for the TEP additive. In addition, TEP and TBP additives improved the thermal stability of the battery and its electrochemical cell performance. Overall, 5 wt% TEP and TBP can be used as a flame-retarding additive to improve the cell performance of Li-ion batteries due to the decrease in cell impedance and SEI formation.

Effect of cold rolling on the corrosion properties of low-alloy steel in an acid-chloride solution

This study examines the effect of a cold-rolling process on the electrochemical properties of low-alloy steel with different rolling percentages ranging from 0 to 80% in terms of the thickness reduction in an acid-chloride solution. From X-ray diffraction analysis, a cold-rolled texture is composed mainly of 〈111〉//ND γ-fibers and the pole density increases with an increase in the degree of deformation. Scanning electron microscopy shows a decrease in the grain size of low-alloy steel with an increase in the degree of cold reduction. Moreover, the corrosion rate decreases with an increase in the degree of cold reduction due to the low-energy grain boundaries of the oriented grains. From potentiodynamic test, it was confirmed that the potential and the current density were decreased with increasing cold rolling reduction. In addition, electrochemical impedance spectroscopy results revealed an increase in the charge transfer resistance of the low-alloy steel with increased levels of cold rolling.

Tris(4-fluorophenyl) Phosphine and Tris(2,2,2-trifluoroethyl) Phosphite as Flame-Retarding Additives in Li-Ion Batteries

Tris(4-fluorophenyl) phosphine (TFPP) and tris(2,2,2trifluoroethyl) phosphite (TTFP) were used as flame-retarding additives in Li-ion battery electrolytes. The cell performance of the TFPP- and TTFP-containing electrolytes was examined by cyclic voltammetry, differential scanning calorimetry, electrochemical impedance spectroscopy and scanning electron microscopy. The flammability of the electrolytes was also examined by measuring the self-extinguishing time of the electrolytes. The results showed that the TTFP additive suppressed the flammability of the electrolyte, improved the thermal stability of the battery and its electrochemical cell performance. On the other hand, the TFPP additive only improved the thermal stability of the electrolyte at the expense of a slight decrease in electrochemical cell performance. The results show that TTFP is a better flameretarding additive in the electrolyte of Li-ion batteries than TFPP.

Electrochemical behavior of CrN coating for polymer electrolyte membrane fuel cell

CrN films on a bipolar plate in polymer electrolyte membrane fuel cells have several advantages owing to their excellent corrosion resistance and mechanical properties. Three CrN samples deposited at various radio frequency (RF) powers by RF magnetron sputtering were evaluated under potentiodynamic, potentiostatic and electrochemical impedance spectroscopy conditions. The electrochemical impedance spectroscopy data were monitored for 168 h in a corrosive environment at 70 °C to determine the coating performance at +600 mVSCE under simulated cathodic conditions in a polymer electrolyte membrane fuel cell. The electrochemical behavior of the coatings increased with decreasing RF power. CrN films on the AISI 316 stainless steel substrate showed high protective efficiency and charge transfer resistance, i.e. increasing corrosion resistance with decreasing RF power. X-ray diffraction confirmed the formation of a CrN(200) preferred orientation at low RF power.

Effect of Flame-Retarding Additives on Surface Chemistry of Electrodes in Li-Ion Batteries

This study examined the properties of 1 wt.% vinylene carbonate, vinyl ethylene carbonate, and diphenyloctyl phosphate additive electrolytes as a promising way of beneficially improving the surface and cell resistance of Li-ion batteries. The additive electrolytes were dominant both in surface formation and internal resistance. In particular, electrochemical impedance spectroscopy, Fourier transform infrared spectroscopy and scanning electron microscopy confirmed that diphenyloctyl phosphate is an excellent additive to the electrolyte in the Li-ion batteries due to the improved co-intercalation of the solvent molecules.