An Activity Coefficient Model Based on the Hydration for Electrolyte Solutions

2013 ◽  
Vol 781-784 ◽  
pp. 379-382
Author(s):  
Lian Ying Wu ◽  
Xian Zhen Xu ◽  
Yang Dong Hu
Keyword(s):  
Activity Coefficient ◽  
Electrolyte Solution ◽  
Elevated Temperatures ◽  
Electrolyte Solutions ◽  
Solute Molecule ◽  
Water Molecules ◽  
Model Based ◽  
Activity Coefficient Model

This paper proposes a hypothesis of hydration. It assumes that the solute in the electrolyte solution exists as molecules, and each solute molecule is surrounded by h water molecules. On this basis, this paper deduces the activity coefficient formulas, and the model is applied to binary electrolyte solutions at room and elevated temperatures.

scholarly journals Anion Coordination Improves High-Temperature Performance and Stability of NaPF6-Based Electrolytes for Supercapacitors

Energies ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4409
Author(s):  
J. Landon Tyler ◽  
Robert L. Sacci ◽  
Jagjit Nanda
Keyword(s):  
Thermal Stability ◽  
Electrolyte Solution ◽  
Elevated Temperatures ◽  
Electrochemical Impedance ◽  
Cycle Life ◽  
Stable Complex ◽  
Complexing Agents ◽  
Anion Coordination ◽  
Decomposition Processes ◽  
Hexamethyl Phosphoramide

Electrolyte stability can be improved by incorporating complexing agents that bind key decomposition intermediates and slow down decomposition. We show that hexamethyl-phosphoramide (HMPA) extends both the thermal stability threshold of sodium hexafluorophosphate (NaPF6) in dimethoxyethane (DME) electrolyte and the cycle life of double-layer capacitors. HMPA forms a stable complex with PF5, an intermediate in PF6 anion thermal degradation. Unbound, this intermediate leads to autocatalytic degradation of the electrolyte solution. The results of electrochemical impedance spectroscopy (EIS) and galvanostatic cycling measurements show large changes in the cell without the presence of HMPA at higher temperatures (≥60 °C). Fourier transform infrared spectroscopy (FTIR) on the liquid and gas phase of the electrolyte shows without HMPA the formation of measurable amounts of PF5 and HF. The complimentary results of these measurements proved the usefulness of using Lewis bases such as HMPA to inhibit the degradation of the electrolyte solution at elevated temperatures and potentially lead to improve cycle life of a nonaqueous capacitor. The results showed a large increase in capacitance retention during cycling (72% retention after 750,000 cycles). The results also provide evidence of major decomposition processes (0% capacitance retention after 100,000 cycles) that take place at higher temperatures without the additive of a thermal stability additive such as HMPA.

Surface charging parameters of charged particles in symmetrical electrolyte solutions

2020 ◽  
Vol 22 (35) ◽  
pp. 20123-20142
Author(s):  
Hadi Saboorian-Jooybari ◽  
Zhangxin Chen
Keyword(s):  
Charge Density ◽  
Surface Charge ◽  
Electrolyte Solution ◽  
Surface Charge Density ◽  
Potential Surface ◽  
Research Work ◽  
Charged Particles ◽  
Electrolyte Solutions ◽  
Surface Charging ◽  
Curvature Dependence

This research work is directed at development of accurate physics-based formulas for quantification of curvature-dependence of surface potential, surface charge density, and total surface charge for cylindrical and spherical charged particles immersed in a symmetrical electrolyte solution.

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