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Polymer-Ionic Liquid Gel Electrolytes for Lithium-Ion Batteries
Published in Prasanth Raghavan, Fatima M. J. Jabeen, Polymer Electrolytes for Energy Storage Devices, 2021
Ion-transference number: The ion-transference number, otherwise known as the ion-transport number, is defined as the total electric current carried in an electrolyte by a given electrolyte-ion. It can be either a cation or an anion. For example, in sodium chloride solution, less than half of the current is carried by the Na+ ions (cations) and the remainder by the Cl- ions (anions). The sum of the transport numbers for all the electrolyte-ions in a given solution always equals unity. The ion-transference numbers for Li+-ion electrolytes can be determined by various methods, such as potentiostatic polarization, galvanostatic polarization, the electromotive force method, and nuclear magnetic resonance spectroscopy [16]. But this is different in the case of a PILGE. An ion-transference number of ~1 is desirable for the PILGE. In typical polymer electrolytes, a single ion-conducting system (such as cation conduction) is observed. Many of the PILGEs reported in the literature show a cation-transference number ≤0.5, which indicates that only half of the ions can move inside a PILGE. When this value is closer to unity, a greater number of cations will be able to move through the polymer electrolyte and hence the power density of the LIB becomes very high.
Recent developments of electromembrane desalination processes
Published in Environmental Technology Reviews, 2018
Derya Y. Koseoglu-Imer, Ahmet Karagunduz
where, i is the current density, I is the current, A is the membrane surface, The current density i can be related to the specific conductivity ĸ by:In an electrolyte solution, the current is carried by both ions. However, cations and anions usually carry different portions of the overall current. In ion-exchange membranes the current is carried preferentially by the counterions. The fraction of the current that is carried by a certain ion is expressed by the ion transport number which is given by:where, Ti is the transport number of the component, the subscript j refers to all ions involved in the charge transport. The transport number Ti indicates the fraction of the total current that is carried by the ion i, the sum of the transport number of all ions in a solution is 1. The membrane permselectivity is an important parameter for determining the performance of a membrane in a certain ion-exchange membrane separation process. It describes the degree to which a membrane passes an ion of one charge and retains an ion of the opposite charge. The permselectivities of AEMs and CEMs can be defined by the following relations;Here ψ is the permselectivity of a membrane, the superscripts cm and am refer to CEMs and AEMs, respectively, and the subscripts c and a refer to cation and anion, respectively.
Effect of functionalised silver nanoparticle on the elastic constants and ionic transport of a nematic liquid crystal
Published in Liquid Crystals, 2019
Shivaraja S. J., R. K. Gupta, Sandeep Kumar, Manjuladevi V
NLC nanocomposites of 5PCH with 0.2, 0.5 and 1 wt% of f-AgNPs were prepared. Planar cells were prepared using indium tin oxide coated glass substrate treated with polyimide and unidirectionally rubbed using soft cloth. The thickness of the empty cells was measured using a fibre optic spectrometer (Ocean Optics) by interferometry technique. The average thickness of the cells was about ~10 µm. The liquid crystal nanocomposites were filled into the cells in the isotropic phase by capillary action method. The differential scanning calorimetry (DSC) measurements were carried out using Shimadzu, DSC60 to determine the transition temperature of pure NLC and its f-AgNPs doped nanocomposites. The optical texture of the LC cells was observed using polarising optical microscope (OLYMPUS BX53M). The optical textures of NLC were observed at room temperature by placing LC cell between crossed polarisers with rubbing direction of LC cell at 45° to either of the polarisers. A He-Ne laser of 633 nm was incident on the LC cell between crossed polarisers with rubbing direction of the LC cell maintained 45° to both polariser and analyser. The transmitted intensity from the LC cells as a function of temperature was measured using a photodiode and birefringence of the NLC and its nanocomposites were estimated using these data. The dielectric constant measurements of nanocomposites in planar cells as a function of temperature at 1 as well as 10 kHz were carried out [31]. The empty capacitance (C0) of the cell was calculated before filling the sample. The ratio of capacitance of the filled cell to the capacitance of the empty cell gives the dielectric constant (ε). The dielectric constant and conductivity measured when the applied field is parallel to molecular long axis of calamitic LC molecules are ε|| and σ||, respectively. ε^ and σ^ are the dielectric constant and conductivity when the applied field is perpendicular to long axis of calamitic LC molecules. The values of ε⊥,σ⊥ and ε||, σ|| are obtained by applying a voltage of 0.4 V (<Vth) and 5 V (≫Vth) to the planar cell, respectively. The dielectric anisotropy Δε is the difference between ε|| and ε⊥. The temperature of the LC cell was varied using a homemade hot stage with an accuracy of ±0.1°C. The ion transport number measurements of 5PCH as well as its f-AgNPs nanocomposites were carried out using dc polarisation technique by applying a voltage of 0.5 V [32]. The accuracy of measurement of physical quantities in this work is about ±1%.