Brine to batteries: lithium extraction technology that’s sustainable and efficient

Amanda Doyle speaks to Teague Egan and Amit Patwardhan of clean technology company EnergyX about the company's membrane technology that extracts lithium from brine pools.

THE energy transition is going to require more batteries for energy storage and electric vehicles, but this in turn requires more lithium. Currently lithium is either mined – which has severe environmental consequences – or produced from brine evaporation pools, which requires a lot of water and doesn’t have a high recovery rate. Clean technology company EnergyX has developed new membrane technology that can extract lithium from brine pools without using fresh water, has up to 90% lithium recovery, and a continuous process takes days rather than months. I spoke to EnergyX Founder and CEO Teague Egan and Executive Vice President of Technology Amit Patwardhan about the company’s move to pilot operations, and its plans for the future.

The membrane technology was originally developed as a metal-organic framework (MOF) system at the University of Texas, and the technology licence was acquired by EnergyX in 2019 in order to commercialise it. Since then, the technology has moved on from MOFs to other types of membranes.

“We really had some breakthroughs in our membranes and membrane development and performances over the last year or so,” said Patwardhan. “Before that, we were dealing with a lot of MOFs and mixed matrix membranes. We have moved away from that – not because they do not work – we actually got them working, but it's really a question of trade off.”

He explained that while MOFs are extremely selective, the throughput is much lower, and the high selectivity is more than what is needed in the field. The non-MOF membranes give a selectivity that is sufficient while having a throughput that is two orders of magnitude higher than MOF membranes.

Moving on from MOFs

Rechargeable lithium batteries either use lithium carbonate or lithium hydroxide depending on the type of battery. The lithium chloride which has been extracted from brine pools can be converted into lithium carbonate and then lithium hydroxide.

The first step in EnergyX’s process uses its Lithium-Ion Transport and Separation (LiTAS) electrodialysis technology. LiTAS uses a proprietary ion-exchange membrane to separate out the dissolved lithium ions from the brine solution, which results in lithium being separated from undesired species such as magnesium in the solution.

The second step then involves bipolar electrodialysis which splits a salt into its acid and base components. In the case of lithium chloride, it splits into lithium hydroxide and hydrochloric acid.

“The regular electrodialysis enhances the recovery and purity of this brine, while the bipolar electrodialysis is our next generation approach,” said Patwardhan. “After we do the separation and cleaning of lithium chloride, we can directly take that to produce the lithium hydroxide by splitting the lithium chloride salt.” The process can be run continuously with a clean lithium chloride brine stream going into the bipolar electrodialysis unit.

He explained that the traditional method for producing lithium hydroxide has multiple steps and is costly. “It requires raw material inputs and you take the lithium chloride then work back to lithium carbonate. Then you redissolve that lithium carbonate and convert that to lithium hydroxide and then clean that lithium hydroxide and crystallise the lithium hydroxide.

“So our second step of bipolar electrodialysis allows us to drastically reduce the costs of production of lithium hydroxide by eliminating all the intervening steps.”

First pilot plant deployed

The first pilot plant using the LiTAS technology has already been deployed at the Salar de Uyuni salt flats in Bolivia, which contains permanent brine pools at the surface and subsurface. Typically, this brine is pumped into evaporation ponds where the impurities naturally precipitate and the lithium becomes concentrated. However, it gets to a point where the lithium also starts to precipitate, which results in a loss of lithium. In the case of the brines in Bolivia, the recovery rate of lithium is around 20%.

EnergyX is applying its technology alongside the existing evaporation ponds at the site in Bolivia. The LiTAS unit is applied just before lithium precipitation starts in the brine pools.

“By introducing our separation system just before that happens you can prevent in its entirety the loss of lithium that they would otherwise encounter,” said Patwardhan. “And by doing so you could double, triple – and in the case of Salar de Uyuni quadruple – the recovery of lithium that is now available from the same amount of brine that was pumped and the same evaporation ponds that already exist.”

The pilot has a production capacity of 3 t/y of lithium carbonate, and doesn’t include the bipolar electrodialysis step. Two other pilot plants are also currently being built in EnergyX’s facility in Austin, which will go to customers in Chile and Argentina.

Scaling up

The pilot plant consists of one container which has two stacks with 30 membranes each, along with all the pumps, piping, instrumentation, and controls. The next step will be a demonstration plant which uses two full-scale stacks, each of which will have 400–600 membranes. Each full-scale stack is capable of producing around 300 t/y of lithium carbonate equivalent. Engineering and procurement has already started for the demonstration phase. “To go to commercial from demonstration scale, there's basically zero risk because it’s just multiplication of these stacks,” said Egan. “You just fill a whole container with stacks, and then you have one container with pumps and pipes that services multiple containers.”

At commercial scale, each stack will still process 300 t/y, and if a customer wanted to process 30,000 t/y, they would just need to increase the number of stacks to 100.

Next generation technology

EnergyX is also exploring the idea of combining its membranes with other lithium extraction methods to maximise on lithium recovery. “We found that different methods are better suited at different points in the brine evaporation system, or depending on the concentration of the brine,” said Egan. “We’re pairing our membranes with solvent extraction to make a more efficient cohesive process. We're basically adding this new technological approach to complement our membrane to make it even better.”

Patwardhan explained that the product from solvent extraction is run through the membranes, so that cleaning and concentrating the brine is done in a single step. “There are other technology providers who are trying to do the same thing and it runs through a gamut of unit operations, such as nanofiltration, and mechanical and thermal evaporation to get to the purity and concentration that is required. We can do all of that in a single step with membranes that are attached to the back end of solvent extraction, ion exchange, or ion adsorption. So that is our next generation technology that we're working on.”

The technology won’t just be restricted to brine pools but can be used on any source of lithium chloride.

In addition to solvents, EnergyX is also at early stages of developing next generation batteries such as new liquid and solid state electrolytes and improving solid state batteries. It is also developing a process to directly produce lithium metal from solvent extraction straight from the brine, which could be used for lithium metal anodes, truly enabling the company to go from brine to battery.