Battle Born makes deep cycle lithium batteries. Expensive, but they come very highly recommended from every RV-er who has used them—at least as far as I can tell. They're pushing $1000 for a 100AH battery, compared to $150-ish for standard lead-acid and $250-ish for AGM. But they can be drawn down 100%, so you get the full 100AH, vs lead acid and AGM which cannot be discharged below 50% without damage, so you really only get 50AH.
My wife and I want to boon-dock, so we are looking for good batteries and solar panels that require as little maintenance as possible.