Patent Application
20160315367
Rechargeable batteries with aluminium anode, supercapacitors, electricity storage for renewable energy production
The interest of electrical energy storage is well known, concerning portable telephones, computers, tablets, cars and grid transporting electricity.
Batteries have to fulfil many objectives: quantity of energy stored, weight, number of load cycles, cost of production, safety.
Traditional batteries are based on two different chemical reactions taking place each one on the surface of one electrode in the presence of an electrolyte.
The Gibbs Energy difference between the reaction in each electrode determines the maximum voltage which can be obtained.
The redox potential is defined as the difference between the ionization potential of a gaseous metal atom and the solvation potential of that atom in the electrolyte. This solvation may include ionic bonds.
In the case of aluminium, both the ionization potential and the solvation in the electrolyte are very high, therefore their difference is small, and the redox potential is defined as this difference.
In order to obtain the full advantage of the high ionization energy and corresponding potential of aluminium to 3 positive charges, it is necessary to avoid the solvation.
To ionize aluminium it is necessary to supply 577.5 kJoule/mole for the first electron, 1816.7 kJoule/mole for the second electron and 2744.8 kJoule/mole for the third electron. The energy necessary for full ionization is therefore 5139.0 kJoule/mole. This value corresponds to a tension of 53.27 Volt. In earlier aluminium batteries (ref. 1, 2, 3, 5), the reaction converts aluminium metal into aluminium III chloride, the enthalpy difference between initial and final state is 704.2 kJoule /mole, while the Gibbs energy is 628.8 kJ/mole. This Gibbs energy corresponds to 6.52 Volt. In fact, aluminium rechargeable batteries are described which generate a tension inferior to 2.5 Volt.
Our idea was to take advantage of the full ionization energy and corresponding tension of aluminium. We tried a plasma battery (ref 4), where we ionised the aluminium vapour in a plasma. However, the energy consumption for the production of the plasma state is too high and local plasma tension fluctuates strongly.
We searched for a process at room temperature to take advantage of the full ionization energy of aluminium in a rechargeable battery.
A new battery is claimed where in the loaded state one electrode is aluminium metal and the second electrode is a supercapacitor constituted by a double layer of aluminium ions with 3 positive charges separated by a dielectric layer from iodine or bromine ions with one negative charge, graphene or a polymeric conductor (ref. 6, 7).
In the unloaded state the new battery has one electrode made of aluminium metal and a second electrode consisting of neutral iodine or bromine contained in a vessel with a dielectric wall.
In this way, the new battery presents an enthalpy difference between the aluminium ions and the aluminium metal which is the ionization energy of 5139 kJ/mole, corresponding to 53.27 Volt.
Earlier batteries present an enthalpy difference between aluminium metal and aluminium chloride of 704.2 kJ/mole (Gibbs Energy 628.8 kJ/mole), which corresponds to 6.52 Volt.
Our invention creates a battery with a high storage capacity of electrical energy, because it eliminates the need of chemical reactions taking place in one electrode, which is substituted by a capacitor. Therefore, the redox potential corresponds to the high ionization energy of aluminium.
We used a glass ampoule with 20 mm diameter and 200 mm height, with a round bottom and a flanged top. The top contains
The supercapacitor (ref 7) is constituted by a glass pipe with rough surface to increase the specific contact surface.
This glass pipe has a round bottom, and presents 5 mm interior diameter, 7 mm exterior diameter.
In the glass pipe is iodine in a 100 mm height, which was previously molten to fill the pipe. The iodine is connected to the stainless steel wire in a length of 50 mm.
The space between the aluminium electrode and the supercapacitor was filled with a mixture of N-Methyl Imidazole (NMI) and bis (trifluormethanesulfonyl) imide (Imide) in a proportion of 0.1 mole of imide to 1.0 mole of NMI.
After eliminating the air at a pressure below 0.1 milibar, we applied to the electrodes a continuous tension of 60 Volt so that electrons were pumped from the aluminium electrode to the supercapacitor. After 30 minutes we stopped the loading process and measured the tension between the electrodes, which was 42.2-43.5 Volt.
The energy which we recovered from the battery was 90% of the energy we spend to load the battery.
This process was repeated 100 cycles, with no significant differences.
