Yes, CATHODES is a Scrabble word!

Letter values in Scrabble US: C 3, A 1, T 1, H 4, O 1, D 2, E 1, S 1.

Is it a valid word?

CATHODES is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

a negatively charged electrode that is the source of electrons entering an electrical device
the positively charged terminal of a voltaic cell or storage battery that supplies current