"Innovation: How Long Before Sodium Batteries Are Worth Their Salt?"

There are at minimum a half-dozen different chemistries being investigated right now, on top of the recipe tweaks being implemented to get more ooph out of lithium or use less cobalt or re-jigger the anode or the cathode but the ongoing reality of battery research is the difficulty getting from lab-bench demonstrations to scaled up production. That said there are technologies that look to take on Mr. Musk's Australian Powerwall concept:

Energy Storage: "It’s Big and Long-Lived, and It Won’t Catch Fire: The Vanadium Redox-⁠Flow Battery"
So much of battery tech and investing has been hailed as breakthrough but then couldn't be made to physically scale. That is definitely not the case with this approach....

Here's another of the contender's, from IEEE Spectrum:

Today, lithium is the active ingredient in batteries that power smart phones, laptops, and cars. But because of the price of lithium, researchers have been looking for another, more abundant element that could replace it. Several start-ups and established companies have tackled the idea of developing rechargeable batteries in which the active ingredient is sodium, lithium’s neighbor on the periodic table.

Besides its availability, sodium has several other important properties—not the least of which is its resistance to catching on fire. What’s more, “It was a good candidate because it could store a similar amount of energy as compared to lithium,” remembers Minah Lee, who does research on sodium batteries at Stanford University.

Today a number of companies are working on developing sodium batteries with the ultimate aim of replacing lithium as the key ingredient. The CNRS, The National Center for Scientific Research in France, recently announced the creation of Tiamat, a start-up company based in Amiens, France, that will develop and bring to the market a sodium rechargeable battery by 2020. CNRS says the battery will be designed in the widespread industrial 18650 format.

In the United States, Aquion, a startup whose focus is the production of high-capacity saltwater batteries for energy storage, escaped bankruptcy by a hair’s breadth. Initially funded with $190 million mainly by Bill Gates and Kleiner Perkins, Aquion was acquired in July by Juline Titans LCC for $9.16 million.

Also, researchers at several universities are now focusing on swapping sodium for lithium in batteries. The advantage these scientists have is that they can use large instruments, such as accelerators, to investigate the anode materials and how they function. “We can get great insight into where the sodium actually goes—both at a detailed atomic level (how it bonds with other atoms) and at much larger scales—as well as how the electrode particles change when they take up sodium,” says Michael Toney,  a researcher at the SLAC National Accelerator Laboratory, operated by Stanford University.

However, reception for sodium batteries by power utilities and by manufacturers of electrical power systems for cars has remained cool. For the moment, they’d prefer to stick with lithium. “The cost of today’s lithium-ion battery technology is very competitive across a variety of markets,” says David Snydacker, a battery expert at Dosima Research. “So for these new sodium batteries to succeed, they not only have to compete against conventional technologies,  but have to compete against lithium batteries—currently a tall order.”...MUCH MORE

We have a few hundred posts on batteries, it is the Holy Grail of electricity investing, use the search blog box, upper left, if interested.
Here is the current membership list of the Salt Institute if sodium ends up being the way to go.