How to keep dogs from attacking Chickens?

We've got large dogs, and a few chickens. We keep them apart but occasionally accidents happen. How do you suggest we end this permanently? Recently I've been reading on certain smells dog don't like because I want to put Citronella on my walls because I have a massive spider-phobia and it keeps them away. But apparently almost ALL animals hate that smell and I wouldn't wanna put anything harmful/ a smell that would make the chickens miserable, however I do want a way that will keep the dog the hell away from the chickens when they break out of their coop/the dogs tunnel their way in.