Right! Sulphation is what happens to lead-acid batteries as they age, and de-sulphation is the "cure". Uh, more or less; )
Here's the chemistry: The acid in the Lead-acid battery is sulphuric acid, and in the process of charging, the battery plates in their acid bath are prone to coughing up sulphide crystals. These crystals either float loose in the acid or attach themselves to the plates and such, slowing or stopping the flow of electrons needed in the business of charging and discharging. Enviroharvest (an alternative energy company in Ontario) says that "Sulphated battery plates (are) the primary cause of poor battery performance."
They go on to say, "A good desulphating unit uses sharp pulses of current at 800 KHz to set up a resonance which "jars, crushes, grinds or dissolves" sulphide crystals...so they can be recombined into the sulphuric acid of the battery electrolyte."
They did mention that desulphation didn't help with other kinds of battery ills...but it's worth a try.