Yes used coffee grounds do repel the ants.
If you have an ant problem you can place some used coffee grounds onto a small plate where the ants are and the ants will smell the coffee grounds and leave those areas alone.
You can also place used coffee grounds in plants soil or even around plants and the used coffee grounds will keep ants away.
You can also pour some hot boiling water on ant piles to kill ants or use some bakers yeast and pour the bakers yeast into the ant pile and the ants will eat the bakers yeast and die because their insides will swell up.
But used coffee grounds to repel ants as I've tried it myself.
You can also place ant traps and those glue traps around places to catch ants.