Andy Leach ran the sodium ion cost comparison at the back end of last year and came out with about $40 per kilowatt hour. That was the potential benefit of putting sodium in place of lithium, measured against an LFP baseline of something like $130 or $140 per kilowatt hour, with the sodium ion cell landing at around $100.
He is careful about how much weight the number can take. The analysis was crude, by his own description. It accounted for the switch in raw material price and the associated energy density losses on the other side of that equation, and for nothing else.
It was also done at an awkward moment for the comparison. Lithium was near a peak, and the price has dropped a long way since, so the benefit will have diminished. He did not have the latest number to hand.
What survives is the direction of travel. Sodium is still going to be cheaper.
Leach spent the days either side of that conversation working the same territory from a stage, having opened the keynote and taken panels on sustainability, process optimisation and battery production in Europe. Sodium ion was the subject the show kept returning to, and it is the one where the analysis is hardest to pin down.
The open question is whether density cancels the saving
Price is the benefit Leach will defend. Energy density is the drawback, and the commercial case for the whole chemistry comes down to whether one balances out the other.
Some sodium ion companies make a second claim, that the technology is also safer. Leach mentions it and moves on. Price is the main benefit.
He is more sceptical about the density claims. Some companies say they can reach LFP energy densities in the near future, and others in the industry have suggested that is unrealistic. Even setting that argument aside, getting to those densities while also delivering a long cycle life and hitting every other parameter is a different problem from getting to them at all, and he expects it to be a challenge.
The scale the model assumes does not exist yet
The $40 figure rests on an assumption that is worth pulling out, because it is doing more work than the chemistry is. The analysis was based on gigawatt hour production.
Almost all of that sits in China. HiNa, a company set up specifically for sodium ion, announced gigawatt hour scale production at the end of last year from a one gigawatt hour factory, and Leach thinks the announcement took a few people by surprise. CATL and Gotion have made announcements too, without saying what capacity they are running at.
A handful of companies in Europe and North America are working at startup scale, building their technology up from a smaller base. He expects that to take a bit longer.
The consequence is that the cost advantage he modelled only appears at the high end of volume, and the market is not there. Building the value chains that would get it there is its own problem. The lithium ion industry is already seeing supply crunches, and Leach expects the same on the sodium side.
The JAC announcement moved the application question
His original view was that sodium ion would be aimed at energy storage systems, with two and three wheeled vehicles as the entry point if it reached transport at all. HiNa's announcement with JAC earlier this year turned that on its head. He now thinks the chemistry probably will get into passenger cars sometime in the near future, and he deliberately declines to attach a year to that.
The first cells in Europe go into drills
Leach began his own research career on sodium ion, which gives his goal for the following year's show a certain edge: he would like there to be a sodium ion cell somewhere on the floor. Not a slide about one, an actual cell that an exhibitor has brought with them.
He has not found one this year, but he has found the next best thing. At Tiamat's talk the day before, the chief executive of the French company said that power tools powered by its sodium ion batteries would be on sale in France in October. Leach's reaction afterwards was that it is good to see a new technology come into market, albeit in one of the niche segments, and that this is often where these technologies start. On the question of whether a cell turns up next year, his position is that if the man does not bring one himself, he would be amazed.
What he wants after the drills is evidence. Announcements can be one thing, he says, and long term behaviour in the field is another: cycle life, real usage data, cells doing work rather than cells being described.
That is what will show which segments sodium ion actually takes.
This piece draws on the full conversation, which is available with a complete transcript on the episode page.