Salt Water Battery Technology

Certainly.

Electricity is the movement of charge from point A to B. In a circuit these charges are negative (free electrons in copper wire) and travel from a negative to positive region. 

Salt water also has a charge, in fact most water has a charge due to freely flowing ionic compounds absorbed within the water. These ions are what causes electrocution through water to occur. 

In theory by containing this ionic solution (Sea Water in this case) and building a circuit around it a resting charge will always be present. This charge differs when the circuit is running to power something.

Sea water is not pure salt (NaCl) and Water (H2O) however the system will still in theory work the same due to principal of ionic charges.

Pros:
Sea Water is the most abundant and easily accessible supply on Earth.
Very little skill required to produce a battery.
No harmful start chemicals.

Cons:
Not very efficient so will require larger area to operate same as say a 12v lithium battery.
Could cause potentially harmful reactants (I am not fully sure and would require to run a prototype to assess).
Will corrode Cathode and Anode over time.

Equations used in quick theoretical testing:

NaCl (aq) --(Electricity)--> NaOH + HCl or NaOH + H2 + Cl2


If Hydrogen gas is produced it is a possibility to exploit its reactivity and combustion to burn it with pure Oxygen (O2) to create energy and as a result produce pure water (H2O). This water is not drinkable as it would burn due to its neutrality and as a result sone ions would have to be absorbed in.

Thank you for the excellent presentation.

So, in the beginning I thought you meant to use saltwater as a conductive substance to carry electrons from a copper rod to say, a steel rod. This is a galvanic effect, I made some it the past, they work great and are super fun to make, the provide a good current but the rods eventually corrode because of the galvanic action.

But if I understand your post correctly you seem to instead propose that we store the electric charge in the saltwater ions themselves (causing them to turn into sodium hydroxide + [HCl / H2+Cl2])? And that when those negative ions are then connected to ground, there would be a current flow that we could use? If I understand this correctly then this means we'd eliminate the need for metal rods in the building of the battery? Am I understanding you correctly?

The second point is electrolysis where you pass electricity through the salt water. What I mean is to exploit the charge the water already has to pass through 2 metal rods.

I see. So, say, one rod is copper, the other is iron, and the charge will flow from one rod to the other (due to the rods being of dissimilar metals) through the salt water (the salt helping to make the water more conductive). Is that correct?

If this is what you are referring to then this could be considered a Galvanic Cell

galvanizeit.org/design-and-fabrication/design-considerations/dissimilar-metals-in-contact#:~:text=The%20galvanic%20cell%20is%20similar,by%20an%20external%2C%20conductive%20path.

They are great fun to make, I made some and they pack a surprisingly good charge. However it will involve corrosion of one of the rods, requiring replacement.

The idea of storing a charge into the saltwater itself is also interesting. Since saltwater is made of water and salt ions I wonder if itd be possible to dissociate those ions when charging, and get a charge back when those ions reassemble.

Yesterday Ive made a quick setup to test that. I stuck two electrodes of similar metal (two straightened paperclips actually) inside a plastic test tube, about 1 cm (1/2 inch) apart. I then filled the test tube with salty water.

I measured the two electrodes with a multimeter. As expected there was no current. This is therefore not a galvanic cell.

I then connected the electrodes to about 10 volts, "charging" the saltwater. As expected a tiny amount of hydrogen was being produced at the negative electrode, proving that the saltwater was definitely getting affected. I let the thing "charge" for a few minutes.

After a few minutes I disconnected the charger and measured the two saltwater's paperclip-electrodes once again. The saltwater was giving off about 150 milliVolts at 3 microAmperes. This electric current steadily decreased over the course of three minutes, at the end of which the current reversed direction (about -5 milliVolts) before settling back to 0 after yet a few more minutes.

This is extremely significant because it's obvious the charge (over 0.15 Volt) was coming from the saltwater itself, not from the tiny paperclip electrodes. This is definitely not a galvanic cell since the two electrodes are of the same metal. So we've successfully stored a charge, albeit for only a few minutes, in the saltwater itself.

I have to assume that the charger was performing some kind of electrolysis on the saltwater molecules, splitting them into two ionized components (the presence of hydrogen does indicate electrolysis is happening) that are more complex than just oxygen and hydrogen. When the charger was disconnected those ions might have been trying to recombine, generating an electric current in the process. After a few minutes the ions were done recombining, the saltwater became electrically neutral once again, and ceased to give any electricity.

Also very interesting is that I was able to re-charge the saltwater once again, and once again when I disconnected the charger I got a steadily declining electric current from the saltwater. So this saltwater thing also seems to have some level of rechargeable capacity.

(By the way these days paperclips come coated in plastic so I had to strip that plastic off my paperclips before I could actually use them as electrodes. If you leave the plastic coating on, the paperclips won't conduct any electricity and you won't be able to replicate this experiment. I used table salt and mixed it with heated-snow water until the water was definitely saturated, meaning there was some salt that couldn't dissolve at the bottom of the test tube. The electrodes were both immersed a good inch (about 2.5 centimeters) into the salty water, but didn't reach all the way down to this salt deposit.)

You wouldn't get any readable measurements from a tiny amount of liquid.

Well the surprising thing is, I did

I am guessing the saltwater separated into two chemicals each with a different charge polarity, and a current showed up on my multimeter (up to 0.15 Volt)

This was without any use of membranes to keep the chemicals separated, which is very impressive

I'll post pictures of the setup when I get the time

Okie dokie. I am a bit confused and I think we are on same page but could be thinking of different things so when I get back home I will set up my own test and show pictures.

So yesterday I repeated the experiment, and Ive had the same approximate results again. This time I have pictures.



Figure 1: This is the test tube of saltwater. Just plain water with plain table salt. There's some salt deposit at the bottom again. Nothing fancy.

Figure 2: Before we begin the experiment I wanted to demonstrate that both electrodes are made of the same metal: paperclips. This isn't a galvanic cell, so the current we'll be measuring later on isn't due to any galvanic action.

Figure 3: I stick the electrodes (paperclips) into the test tube. There's about 1 cm (half an inch) between the electrodes.

Figure 4: The test tube was so small it was pretty wobbly when I'd attach alligator clips to it. So I stabilized the base with a wrench.

Figure 5: We measure the current flowing between the two electrodes. As expected, there's no current flowing. Once again this also proves it isn't a galvanic cell.

Figure 6: We begin charging the thing. Those cables are from my homemade charger. We're passing 10 Volts into the saltwater.

Figure 7: After 10 minutes of charging we remove the charger's cables. We stop charging the thing. We then measure the electrodes once again. It was 6:00 PM when I did. As you may notice, the multimeter is set to measure DC voltage. It's measuring a current of 0.15 V immediately after we had disconnected the charger. The saltwater has stored a charge! We have ourselves a battery!

Figure 8: After a minute (6:01 PM), the current as measured by the multimeter has dropped to zero. This may sound like a crappy battery (well, it is just saltwater after all), but wait, there's more.

Figure 9: (6:02 PM) the current reversed direction. We now have a smaller, but more stable current coming off from the saltwater.

Figure 10: (6:03 PM) over the next minute the current steadily increased to -0.022 Volt. If you swap the cables polarity at this point, the multimeter will be reading a positive number. So if you're upset with the current direction just swap the cables with one another.

Figure 11: (6:04 PM) it's been 4 minutes now and the saltwater is still giving off a stable -0.022V current.

Figure 12: (6:04 PM) It's good to know the voltage of the current, but what about its volume? Turns out it's giving off 2 microAmperes.

Figure 13: (6:05 PM) Its been 5 minutes. The current voltage drops by a single point, to -0.021 Volt. This is impressive considering it's just a friggin tube of saltwater with two paperclips. The saltwater really is acting as a rudimentary battery.

Figure 14: (6:06 PM) Finally another drop of one point. We're at -0.020V. The current will continue dropping steadily for the next quarter of an hour or so.

Figure 15: Just wanted to show a top shot of the thing. Nothing fancy. Of course, it's important the two paperclip electrodes don't touch one another.


So the behaviour of the thing is really consistent with that of a battery. You charge it up, then you disconnect the charger, after which the thing will give off a current. Super impressive is the fact the electrodes are of the same metal. So the subsequent current is directly coming from some chemical action in the saltwater itself, without involving any expensive dissimilar metals rods. This has considerable implications. Basically, it demonstrates it's possible to store a charge in saltwater itself!

This is what I meant. When you said charge up I thought you meant pass electricity through rather than just the salt water. Salt water batteries are such a good and cheap idea and can be manufactured really fast in virtually anyclimate.

Well when I charge the thing up, both paperclips act as electrodes, and some kind of electrolysis happens in the saltwater. My guess is, it doesn't just split water but also the Na and Cl ions. When you disconnect the charger, I'd guess the Na and Cl ions would then form a current until they recombine. I'm not sure I'm not a chemist lol

Yeah, its super cheap