Battery world - part 1

The 2019 Nobel Prize in Chemistry was awarded for developing the design of lithium-ion batteries. Unlike some of the other verdicts of the Nobel Committee, this one did not surprise - quite the contrary. Lithium-ion batteries power smartphones, laptops, portable power tools and even electric cars. Three scientists, John Goodenough, Stanley Whittingham and Akira Yoshino, deservedly received diplomas, gold medals and 9 million SEK for distribution. 

You can read more about the rationale for the award in a previous issue of our chemistry cycle - and the article itself ended with the announcement of a more detailed presentation of the issue of cells and batteries. It's time to keep your promise.

First, a brief explanation of the naming inaccuracies.

Link this is the only circuit that generates voltage.

Battery consists of correctly connected cells. The goal is to increase voltage, capacitance (energy that can be drawn from the system), or both.

battery it is a cell or battery that can be recharged when it is depleted. Not every chip has these properties - many are disposable. In everyday speech, the first two terms are often used interchangeably (this will also be the case in the article), but one must be aware of the difference between them (1).

1. Batteries consisting of cells.

Batteries have not been invented for the last decades, they have a much longer history. You may have already heard about the experience Galvaniego i Volts at the turn of the XNUMXth and XNUMXth centuries, which marked the beginning of the use of electric current in physics and chemistry. However, the history of the battery began even earlier. It was a long time ago …

... long time in Baghdad

In 1936 a German archaeologist Wilhelm Koenig found an earthenware vessel near Baghdad dating back to the XNUMXrd century BC. The find did not seem unusual, given that civilization on the Euphrates and Tigris flourished for thousands of years.

However, the contents of the vessel were mysterious: a rusted roll of copper sheet, an iron rod, and remnants of natural resin. Koenig puzzled over the purpose of the artifact until he remembered visiting the Alley of Jewelers in Baghdad. Similar designs were used by local craftsmen to cover copper products with precious metals. The idea that it was an ancient battery did not convince other archaeologists that no evidence of electricity survived at that time.

So (that's what the find was called) is this a real thing or a fairy tale from 1001 nights? Let the experiment decide.

You will need: copper plate, iron nail and vinegar (note that all these materials were known and widely available in antiquity). Replace the resin to seal the vessel and replace it with plasticine as insulation.

Do the experiment in a beaker or flask, although using an earthenware vase will give the test an authentic flavor. Using sandpaper, clean metal surfaces from plaque and attach wires to them.

Roll the copper plate into a roll and place it in the vessel, and insert the nail into the roll. Using plasticine, fix the plate and the nail so that they do not touch each other (2). Pour vinegar (approx. 5% solution) into the vessel and, using a multimeter, measure the voltage between the ends of the wires connected to the copper plate and the iron nail. Set the instrument to measure DC current. Which of the poles is the "plus" and which is the "minus" of the voltage source?

2. Sketch of a modern copy of the battery from Baghdad.

The meter shows 0,5-0,7 V, so the Baghdad battery is working! Please note that the positive pole of the system is copper, and the negative pole is iron (the meter shows a positive voltage value in only one option for connecting wires to terminals). Is it possible to get electricity from the built copy for useful work? Yes, but make some more models and connect them in series to increase the voltage. The LED needs about 3 volts - if you get that much from your battery, the LED will light up.

The Baghdad battery was repeatedly tested for its ability to power small-sized equipment. A similar experiment was carried out several years ago by the authors of the cult program MythBusters. Mythbusters (do you still remember Adam and Jamie?) also came to the conclusion that the structure could serve as an ancient battery.

So did mankind's adventure with electricity begin over 2 years ago? Yes and no. Yes, because even then it was possible to design power supplies. No, because the invention did not become widespread - no one needed it then and for many centuries to come.

Connection? It's simple!

Thoroughly clean the surfaces of metal plates or wires, aluminum, iron, etc. Insert samples of two different metals into a juicy fruit (which will facilitate the flow of electricity) so that they do not touch each other. Connect the multimeter clamps to the ends of the wires sticking out of the fruit, and read the voltage between them. Change the types of metals used (as well as fruits) and keep trying (3).

3. Fruit cell (aluminum and copper electrodes).

In all cases links were created. The values ​​of the measured voltages differ depending on the metals and fruits taken for the experiment. Combining fruit cells into a battery will allow you to use it to power small electronic equipment (in this case, it requires a small amount of current, which you can get from your design).

Connect the ends of the wires sticking out of the extreme fruits to the wires, and these, in turn, to the ends of the LED. As soon as you have connected the battery poles to the corresponding "terminals" of the diode and the voltage has exceeded a certain threshold, the diode will light up (diodes of different colors have a different initial voltage, but about 3 volts should be enough).

An equally attractive power source is an electronic watch - it can operate on a “fruit battery” for a long time (although a lot depends on the model of the watch).

Vegetables are in no way inferior to fruits and also allow you to build a battery out of them. Because? Take a few pickles and an appropriate amount of copper and aluminum sheets or wires (you can replace these with steel nails, but you'll get lower voltage from a single link). Assemble a battery and when you use it to power the integrated circuit from the music box, the cucumber choir will sing!

Why cucumbers? Konstantin Ildefons Galchinsky argued that: "If the cucumber does not sing and at any time, he probably cannot see by the will of heaven." It turns out that a chemist can do things that even poets have not dreamed of.

Bivakov battery

In an emergency, you can design a battery yourself and use it to power an LED. True, the light will be dim, but it is better than none.

What will you need? A diode, of course, and in addition, an ice cube mold, copper wire, and steel nails or screws (metals should have their surfaces cleaned to facilitate the flow of electricity). Cut the wire into pieces and wrap the head of the screw or nail with one end of the fragment. Make several steel-copper layouts in this way (8-10 should be enough).

Pour moist soil into the recesses in the mold (you can additionally pour salt water, which will reduce electrical resistance). Now insert your structure into the cavity: the screw or nail should go into one hole, and the copper wire into the other. Place the next ones so that there is steel in the same cavity with copper (metals could not come into contact with each other). The whole forms a series: steel-copper-steel-copper, etc. Arrange the elements in such a way that the first and last cavities (the only ones containing individual metals) lie next to each other.

Here comes the climax.

Insert one leg of the diode into the first recess in the row and the other leg into the last. Is it shining?

If so, congratulations (4)! If not, look for errors. An LED diode, unlike a conventional light bulb, must have a polarity connection (do you know which metal is the "plus" and which is the "minus" of the battery?). It is enough to insert the legs in the direction opposite to the ground. Other causes of failure are too low voltage (minimum 3 volts), open circuit or short circuit in it.

4. "Earth battery" in operation.

In the first case, increase the number of components. In the second, check the connection between the metals (also seal the ground around them). In the third case, make sure that the ends of copper and steel do not touch each other underground and that the soil or mortar with which you wetted it does not connect adjacent pits.

The experiment with the "earth battery" is interesting and proves that electricity can be obtained from almost nothing. Even if you don't have to use a built structure, you can always impress campers with your MacGyver-like skills (probably only remembered by senior technicians) or master survivalist.

How do cells work?

A metal (electrode) immersed in a conductive solution (electrolyte) is charged from it. The minimum amount of cations goes into solution, while electrons remain in the metal. How many ions are in solution and how many excess electrons are in the metal depends on the type of metal, solution, temperature, and many other factors. If two different metals are immersed in an electrolyte, a voltage will arise between them due to the different number of electrons. When connecting the electrodes with a wire, electrons from a metal with a large number of them (negative electrode, i.e. cell anode) will begin to flow into a metal with a smaller number of them (positive electrode - cathode). Of course, during the operation of the cell, a balance must be maintained: metal cations from the anode go into solution, and the electrons delivered to the cathode react with the surrounding ions. The entire circuit is closed by an electrolyte that provides ion transport. The energy of electrons flowing through a conductor can be used for useful work.