something gets " used up" in a battery that eventually dies and goes flat.?

Question

Is it because the current is used up or the energy is used up. Explain

Answer 1

Simply stated:

It is important to remember that batteries do not produce electricity, they store electricity in the form of chemical energy (H2SO4 or sulfuric acid) This electrolyte is the only physical connection between the positive and negative terminals. A battery's state of charge can be tested by merely checking the electrolyte acid and water mixture and comparing it to plain water - this is called the specific gravity of the electrolyte.

As the battery discharges, both electrodes inside the battery undergo a chemical change to form lead sulphate on the plates as the battery discharges. Recharging the battery simply reverses this process and partially renews the chemical electrolyte.
Eventually the plates become more and more sulphated until the ability of the chemical change which releases the energy becomes poor enough as to render the battery "used up."

Answer 2

Essentially, a battery is a "voltaic cell", which probably means very little to you, so let me explain.

A redox (reduction/oxidation) chemical reaction, which is a reaction where electrons are transferred, is the primary "driving force" of a battery. Essentially, once this chemical reaction reaches equilibrium, there are no more electrons flowing through the circuit, and the battery "dies".

Rechargeable batteries simply add energy to reverse the reaction direction, and allow the battery to resume its normal operation.

Hope this helps!

Romi @ University of Waterloo