Does the word splitted exist in the English language or slang?

No. Split is an irregular verb. The past simple and past participle of split is split.

e.g.

(1) My friend split up with her boyfriend last week.

(2) Scientists were very pleased when they first split the atom.

(3) The estate was split between the three surviving children.

If 'splitted' has been used, it is based an an incorrect usage of the Word, and assumes that 'split' is a regular verb like jump, lift, bang. 'Split' is irregular, like cut, hit, and throw.

* For more details and list of verbs with similar conjugation, see Related links below this box