The logic behind this this process is that dry cell batteries are based on containing several chemical compounds which react with each other to create compounds with lower electrical potencial producing movement of electrons (eletricity for those who didnt do phisics or chemisty), as anyone who's studied chemistry knows, chemicals will tend towards a state with less energy, in rechargable batteries, the chemical reactions can be reversed by applying energy to the battery, creating a inverse electron flow,

now, the process isnt perfect, and some sideproducts are created, some inefficiency occures becuase of non perfect conditions for the reaction and other causes, aswell as applying current when the chemical reaction is incomplete on sime types of batteries (memory effect),

now, the idea behind this trick is to remove a large amount of energy from the battery to take it to a complete "uncharged" state, as in to reverte it to the original unreacted components, also hoping that the excessive removal of energy will allow the side products to break up to the original reactants.

How to prolong lithium-based batteries

http://www.batteryuniversity.com/parttwo-34.htm