Does battery weigh less when it is discharged?

Does battery weigh less when it is discharged?

To find its answer first we have to look inside a battery.
Battery is a group of cells which contains two electrode (i) Anode and (ii) Cathode each electrode form a half cell where oxidation and reduction goes side by side. See what happens in a battery when it gives out electrical energy or works as galvanic cell. Let me to take very common and a simple example of a cell.

Take two beaker one filled with ZnSO4 and another with CuSO4 and two electrodes one made up of zinc and another of copper. Now each of them is dipped into their corresponding ion containing solution. Means Zn dipped into ZnSO4 solution and Cu dipped into CuSO4 solution. And each electrode is connected with wires which is connected to a bulb, for our convenient we can connect a switch. And a salt bridge should be connected between both beakers. This salt bridge completes the circuit.

Now at zinc electrode Zn2+ starts mixing with the solution due to which zinc electrode becomes negative and solution becomes positive. It is because, when Zn 2+ comes from zinc electrode, it left 2 electrons in the zinc electrode due to which it turns negative. And as Zn 2+ dissolved in the solution that is why the solution becomes positive. At the same time, at copper electrode Cu 2+ ion from the CuSO4 solution get deposited at copper electrode. Due this process copper electrode gets positive charge and at the same time copper sulphate solution get negative charge.

This is spontaneous chemical reaction in which chemical energy is converting into electrical energy. Not any mass is coming out from the system.

Now, see what happens in a Lithium ion battery while charging and discharging.

First of all let me compare a lithium ion battery with above battery. In lithium ion battery currently lithium cobalt oxide is used as cathode and anode is made up of mixture lithium and graphite. And as like the cell which I have described above lithium ion cell also works in the same manner while discharging. Hence there is no loss of mass while discharging of lithium ion battery and also there is no gain of mass while charging of lithium ion battery. While discharging of lithium ion battery oxidation takes place at graphite-lithium electrode and reduction takes place at lithium cobalt oxide. And while charging these processes get reversed.
Discharging is a spontaneous process in which chemical energy get converted into electrical energy that is we get ‘G’ negative. On the other hand, charging is non-spontaneous process in which we apply electrical energy to make potential difference in the cell and when this potential difference reaches the equilibrium our phone notifies battery is full and from now no further reaction will takes place in the cell. Well, this is a short post only about the myth I am not going to make this more puzzling, and as this is Simple Science.😉

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