Redflow is an Australian startup that I have shares in. They make zinc-bromine 'flow' batteries - basically a plastic tank full of liquid electrolyte with electrodes sitting in it and all the other electronics attached.

The batteries are currently targeted at commercial scale off-grid, fixed storage applications where a rugged, reliable solution is needed. They are electrically robust - unlike most other battery technologies, you do not harm them if you completely discharge them. They are also a lot safer and will not burst into flames. But they do not have the energy density for mobile applications.

They are a penny stock at the moment. They have been surviving on government funding and capital raising for a while, but now have a plant up and running and are starting to make significant sales. They have a huge potential if they become competitive for off grid storage, and look like they can also compete with grid-connected storage.

https://redflow.com/solutions