The Ion Recharger is a booster for energy weapons. It is the counterpart of the ion modulator for ship weapons. It increases the damage dealt to shields, but reduces the damage dealt to armor.
The ion modulator isn't as useful as focused apertures, but when they're mixed with Tachyon beam turrets or ECHO ray turrets, they can lay down very high levels of damage to shields and deplete them rapidly, allowing your other combat modules that would be equipped with different weapons not using the ion recharger to deal damage to the ships armor more quickly.
Like stated above, the ion recharger isn't the best option. The better choice would normally be focused apertures, which increase the effectiveness of its ability to combat long range, fleets of destroyers when the decoys in the said fleet stray too close to the turret.