How to make a copper/zinc penny battery rechargeable?

Question

I just saw the copper+zinc+vinegar battery also known as "penny battery" and I thought it would be perfect to make at home since I don't know anything about chemistry.

On the Wikipedia page linked it is said that the process is irreversible, so the battery can't be recharged.

Searching a bit I've seen here that some company patented their copper/zinc rechargeable batteries (patent link).

However, I couldn't make heads of its structure; I'm not trying to make a industrial level battery, just a homemade simple thing.

In order to make it rechargeable, I just need to put the zinc and copper inside their own separator (like in lead-acid batteries in cars or lithium-ion batteries, I believe) and fill it with vinegar, right? Or there is something else to it?

Answer 1

The core of the claimed process is contained in sections 0042 to 0047 of the patent. To stop this being a link-only post and because the material is intersting and informative, here 'tis.

I have 'bolded' the two 'magic' portions.

Note also the diagrams in the patent.

---

From patent Rechargeable copper-zinc cell

It is therefore an object of this invention to provide a long cycle life rechargeable copper-zinc bipolar cell.

[0042] It is still further an object of this invention to provide a rechargeable copper-zinc bipolar cell comprising an electrochemical polymer membrane separator useful as an electron and proton conducting membrane. The polymer electrochemical membrane separator is not metal ions conducting.

[0043]These objects are accomplished by a combination of a bipolar electrode, a zinc electrolyte, a copper electrolyte and a metal-ion impermeable, polymer electrochemical membrane separator. The zinc electrolyte and the copper electrolyte are separated from each other by the bipolar electrode on one side and by the membrane separator on the other side. Discharging involves electro-depositing copper from the copper electrolyte on the negative side of the bipolar electrode while corroding zinc from the positive side of the bipolar electrode into the zinc electrolyte. The charging of the system involves the reverse of this process, electro-depositing zinc from the zinc electrolyte on the positive side of the bipolar electrode while corroding copper from the negative side of the bipolar electrode into the copper electrolyte.

[0044] The primary function of the metal-ion impermeable, polymer electrochemical membrane separator is to separate the copper half-cell from the zinc half-cell such that the copper ions and the zinc ions remain in their respective half-cells, but still permitting protons and electrons to pass through.

[0045] The bipolar electrode may be made of a single conductive material, or a combination of more than one conductive materials, or layers of material to give suitable conductivity, corrosion resistance, mechanical strength and electroplated material adhesion.

[0046] According to a first aspect of the present invention, there is provided a metal-ion impermeable, polymer electrochemical membrane separator comprising a first polymer, a second polymer and functionalizing groups.

[0047]Preferably, the metal-ion impermeable, polymer electrochemical membrane separator comprises polystyrene, polyethylene terephthalate and functionalizing groups. The membrane separator isolates copper and zinc on either side of the membrane separator with a permeation rate of less than 1 μmol/day.

The functional groups are chemically bonded to polystyrene and polyethylene terephthalate and contain a mixture of compounds which may include MePO3 and EtCO(OH).

Answer 2

how to make it rechargeable?

When you discharge (or charge) a battery, you literally are changing what the battery is made of. Chemical reactions happen at the surface of the electrodes that change the electrode material into something else, and change the electrolyte into something else.

The difference between a rechargeable* battery and a disposable battery is whether or not the "something else" stays mostly fixed in one place, where it can be changed back when the current is reversed, or whether it moves to somewhere else and becomes unavailable for re-charging.

Figuring out how to make a rechargeable battery is a problem that spans both chemical engineering and mechanical engineering.

---

* Most commercially produced, "disposable" batteries actually can be recharged. Just not very many times. When I was a kid I bought a battery charger that worked for old-style, "carbon-zinc" batteries. And I've seen battery chargers sold for modern "alkaline" batteries. But those batteries can only be recharged maybe five or ten times before their internal structure breaks down to the point where they (a) stop taking a useful charge, or (b) burst open and leak toxic, corrosive goo inside your device.

Likewise, most commercially produced, "rechargeable" batteries can only be recharged a limited number of times before either (a) or (b). It's just that the "rechargeable" ones can be recharged hundreds or thousands of times before it happens instead of five or ten times.

Answer 3

Try this as a starting point:

1. Cut two strips of metal, one from copper and one from zinc.
2. Attach wires to each one.
3. Take a lemon and push one strip into one end and the other strip into the other end.
4. Take a voltmeter and see what output voltage you are getting.
5. Attach some various loads and see how much current you can get out of it.

There you go, you have made a copper/zinc battery. Now you can experiment with different electrolytes than lemon juice. Try it with vinegar in a plastic or glass jar and suspend the metal strips in the liquid. Etc....