Gregory Cooper pours black silicon slurry on a copper current collector in a laboratory

AquaLith’s chief executive Gregory Cooper says that the company is hoping to produce samples of its anode material for testing this year.Credit: Aqualith Advanced Materials

AquaLith Advanced Materials in College Park, Maryland, spun off from the University of Maryland in College Park in 2020.

With the growth of electric vehicles and renewable energy, the demand for better rechargeable batteries keeps rising. But nothing has yet managed to displace standard lithium-ion technology. AquaLith Advanced Materials in College Park, Maryland, which has been longlisted for The Spinoff Prize 2023, is developing materials that can be used to build batteries that are safer, cheaper and pack in more energy for their weight than existing devices.

Rechargeable batteries consist of three major components — the negative anode, the positive cathode and the electrolyte between the two, through which electrons flow back and forth. Chunsheng Wang, a chemist and biochemical engineer at the University of Maryland in College Park and a co-founder of the company, says that the materials he has developed in collaboration with Kang Xu, a chemist at the US DEVCOM Army Research Laboratory in Adelphi, Maryland, improve on all three.

Anodes in electric-vehicle batteries are typically made of graphite. Many researchers have explored replacing the graphite with silicon. Like graphite, silicon can house numerous lithium atoms when the battery is charged, giving it a high energy density. But the silicon swells and shrinks during charging and discharging, soon cracking and becoming useless. One way around this problem is to use silicon nanoparticles, but they’re expensive to produce and don’t last very long. AquaLith Advanced Materials splits the difference, building its anode out of larger, micro-sized silicon particles, which are more stable than conventional silicon anodes and last longer than nanoparticles. Switching to these best-of-both-worlds anodes would reduce the weight of the battery by 15–20%, says AquaLith’s chief executive Gregory Cooper, and could also shave a little under 10% off the total cost of a 100-kilowatt-hour battery.

Just add salt

The company’s electrolyte is also intended as something of a happy compromise. Most electrolytes are based on lithium salts, which can catch fire if they overheat. Water-based electrolytes are safer, but they can’t handle a high enough voltage to operate efficiently. Wang’s solution is to add salt to a water-based electrolyte. This forms a film around the electrodes that increases their voltage capacity by about 150%.

The final element — the cathode — is typically made from a mix of lithium, nickel, manganese and cobalt oxides (known as NMC), or from lithium iron phosphate (known as LFP). The metals in NMC cathodes have a high energy density but are expensive, whereas LFP is cheaper but holds less energy. The cathodes made by AquaLith Advanced Materials are instead made of a hybrid material of lithium bromide, lithium chloride and graphite. The bromide and chloride capture and release lithium by undergoing a chemical reaction. Such conversion provides a high energy density, but normally lasts only for 50–100 charge–discharge cycles, well below what is needed for a practical electric vehicle. Adding graphite compensates for that, allowing up to ten times as many charging cycles.

The anode is the company’s most-developed element, but using it in a product is at least three years away, says Cooper, who trained as a physicist and calls himself a “serial entrepreneur”. The company plans to produce samples of the anode material for testing later this year. A battery that replaces only the cathode and electrolyte is running about a year behind an anode-only version. Combining all three technologies into one battery will probably take an additional two or three years, Cooper says. (AquaLith has no plans to manufacture batteries itself, and intends to focus on making the materials.) Although companies touting new batteries have come and gone, Cooper and Wang are optimistic. Other approaches have been based on changing how batteries are manufactured, Cooper says, but AquaLith’s approach “enables us to use the existing infrastructure for making lithium-ion batteries, which is very important”.

That is promising, agrees Sue Sundstrom, a start-up coach based in Clevedon, UK, and one of the judges for The Spinoff Prize 2023. “It’s nice to see them not trying to reinvent the battery,” she says. Another judge, Emily Mackay in Cambridge, UK, a machine-learning specialist at Siemens Energy, says AquaLith Advanced Materials is focusing on an important area: the need for energy-dense, safe batteries that can be made cheaply with widely available materials. The company’s approach, she says, “shows promise as a business, rather than being just good research”.