The tricky part to finding the formula for a good calcium battery (as it was with lithium batteries) is getting the interface reaction to work. It's a complicated reaction that is hard to understand or predict. Brute forcing different combinations will take a long time because the search space is large. There is some work going on to make better simulations to speed up the brute force search. I'm not a battery expert; this is all second-hand from a friend who is working on calcium battery simulation.