Battery

A battery is a type of electrochemical system Electrochemical System  consisting of one or more cells where chemical energy is stored and converted into electrical energy to be used as a power source.  Batteries are normally two-electrode systems Two-Electrode System  composed of an anode Anode  and a cathode Cathode  separated by a solid or polymeric electrolyte, Electrolyte all in close proximity and often sealed inside some kind of vessel.  The vessel typically contains two external terminals that facilitate electrical contact with the anode and cathode.

 

There are two main types of batteries: primary and secondary (rechargeable).  The anode and cathode in a primary battery deliver electrical energy via an irreversible process, meaning they cannot therefore be restored to their initial states by applying electricity to the cell - i.e., primary batteries cannot be recharged or reused multiple times.  Once the usable energy has been depleted from a primary battery, it is either recycled or discarded.

 

The anode and cathode in a secondary battery deliver electrical energy via a reversible, or at least partially-reversible, process, meaning they can therefore be restored at least partially to their initial states by applying electricity to the cell - i.e., secondary batteries can be recharged and reused multiple times.  However, their efficiency generally decreases over time and repeated recharging cycles, eventually leading to a state where they can no longer be effectively recharged and must be either recycled or discarded.