The authors report on conductivity studies carried out on lithium solvated electron solutions (LiSES) prepared using 1,3,5-triphenylbenzene (TPB) and corannulene as electron receptors.
The overall goal of this experiment is to show the preparation method of LISES and to measure some of their physical chemical properties in view of their application in rechargeable batteries. This method can help answer key questions in the physical chemistry field about the preparation and physical properties of lithium sulfated argon solutions. The main advantage of this technique is that it provides an inert material in the liquid state at ambient temperature.
The implications of this technique extend toward next generation refillable lithium batteries for electric vehicles. Currently some ion batteries require overnight charging, whereas refillable batteries may be recharged in ten minutes. Visual demonstration of this method is critical as the steps to make the LISES need to be repeated exactly for the best results and to avoid potential hazards.
The synthesis will be demonstrated by Andrew Lunchev, a PhD student in the group of professor Andrew Grimsdale. Place four grams of acetophenone in 100 milliliters of absolute ethanol in a triple neck 250 milliliter round bottom flask, equipped with a magnetic stir bar, reflux condenser, dropping funnel, gas bubbler, nitrogen inlet and thermometer. Place the reaction mixture under a nitrogen atmosphere.
Then cool the mixture to zero degrees Celsius. Using the dropping funnel, add 2.1 equivalents of silicon tetrachloride to the mixture in a single portion. Monitor the reaction mixture for ten minutes, during which gaseous hydrogen chloride will form.
Then heat the mixture to 40 degrees Celsius while stirring and continue stirring for 20 hours. Then cool the reaction mixture to room temperature and add ice water in a 1:1 mass ratio with the reaction mixture. Extract twice with dichloromethane.
Combine the extracts and wash them with 100 milliliters of saturated sodium chloride solution. Then dry the mixture of anhydrous magnesium sulfate. Filter the mixture to remove the magnesium sulfate and concentrate the filtrate with a rotary evaporator.
Recrystalization from ethanol yields 1, 3, 5-triphenlybenzene. Perform all preparation of the litium sulfated electron solutions in an argon filled glovebox. First place 12 milliliters of tetrahydrofuran in each of nine glass vials.
Then dissolve six millimoles of TPB in each of four of the vials to form a 0.5 molar solution. To each of the remaining five vials add 0.6 millimoles of corannulene to form a 0.05 molar solution. To prepare TPB based LISES with lithium TPB molar ratios ranging from one to four, add six, 12, 18 and 24 millimoles of metallic lithium to the four vials of TPB solution Then, to prepare core based LISES with lithium core molar ratios ranging from one to five, add 0.6, 1.2, 1.8, 2.4, and 3 millimoles of metallic lithium to the five vials of core solution.
Add a borosilicate glass-coated magnetic stir bar to each of the vials, close the vials and seal the vials with laboratory film. Stir all mixtures overnight to completely dissolve the metallic lithium. Perform the procedure in a glovebox with a calibrated conductivity meter capable of measuring solution temperature Immediately before measuring the conductivity of the LISES samples, remove each tightly sealed sample from the glovebox.
Wrap the vial in an additional layer of laboratory film and cool the sample to approximately 10 degrees Celsius. Do not allow the sample to freeze solid. Transfer the cooled sample back into the glovebox, purging the antichamber at least five times to exclude moisture from condensation.
Record conductivity measurements for each sample until the sample returns to room temperature. Keeping the probe immersed in the solution throughout. Plotting conductivity of the corannulene-based LISES against temperature reveals a linear relationship with a negative slope, indicating metallic conductivity behavior.
Using this relationship the temperature coefficient and the conductivity at ambient temperature can be determined for each lithium-corannulene molar ratio tested. The conductivity of 135-triphenlybenzene based LISES increases when the lithium to TPB ratio increases from one to two. The conductivity then decreases as the ratio continues to increase.
Previously studied naphthalene and biphenyl based LISES demonstrates similar metallic conductivity behavior and changes in conductivity with changing molar ratios. Once mastered, this technique can be done in one hour if it is performed properly. Well attempting this procedure it is important to remember to always prepare an LISES in a controlled, dry environment, such as in an argon filled glovebox and to never expose an LISES to the ambient atmosphere.
Following this procedure, other methods like preparing a liquid cathode can be performed in order to answer additional questions about the concept of liquid anode and liquid cathode lithium cell.
