It's a lead acid system. That's how they they work. This system is nothing new. Just the same old batteries people have been using for years. They are just smart enough to constantly refer to Tesla and how they are "cheaper" in their press releases. The key figure they never release is the number of cycles that battery is rated for.
Lead acids and gels can be very dangerous at home. Require maintenance to ensure they don't explode and leak deadly gasses.