Could well be a myth.
But the guy that repaired my Ni-MH ones talks about it on his web site, Li-ION section copied below...I had no reason to doubt him.
As a battery repair man it would be a bit short sighted of him business-wise to limit his potential repair service unnecessarily.
Do you have any reason to think he is mistaken?
Alan
Lithium Ion- Advantages, disadvantages
Advantages are no memory effect, much greater capacity for same weight as Nimh or Nicad. Ability to hold full charge for long periods. Disposal is non toxic.
Disadvantages include - liable to explode if overcharged, or damage if cell voltage drops too low. For power tools this can be an abrupt stop as sensors detect this. Generally not as good power output as Nicad or Nimh (tends to die under heavy loads). Complicated charging circuits with circuit boards inside the battery.
What equipment should I buy - NICAD, NIMH or Li-ION?
My advise would be to avoid Lithium Ion batteries and stick to the traditional HQ NICAD or NIMH type.
Reason for this is because manufacturers of Lithium Ion batteries have become very clever in their design of protective circuits that are necessary but easy to include extras that prevent repairs, thus ensuring you have to buy a replacement from them at their price - which will be high!
Makita for example on their 14.4V and 18V, 3Ah range the circuit locks up after 750 charges, it will no longer charge on a Makita charger again, regardless if the battery is still good. Or if it detects a fault on the cells, after 3 attempts to re-charge, locks up and will never charge again on a Makita charger, even if the cells have been replaced. There is no way round this and Makita will not even answer queries about it. There are also 3 different types of Li-Ion cells used by various manufactures which are all difficult to obtain in the UK.