Scientists turned to artificial intelligence to find materials to replace the flammable ones that cause batteries in phones and laptops to catch fire. So far they’ve identified 21 solid electrolytes.
“Electrolytes shuttle lithium ions back and forth between the battery’s positive and negative electrodes,” says lead author of the study Austin Sendek, a doctoral candidate in applied physics at Stanford University and first author of the paper. “Liquid electrolytes are cheap and conduct ions really well, but they can catch fire if the battery overheats or is short-circuited by puncturing.”
Battery fires led to the recent recall of nearly 2 million Samsung Galaxy Note7 smartphones, the latest in a series of highly publicized lithium-ion battery failures.
“The main advantage of solid electrolytes is stability,” Sendek says. “Solids are far less likely to blow up or vaporize than organic solvents. They’re also much more rigid and would make the battery structurally stronger.”
Let the algorithm find them
Despite years of laboratory trial and error, researchers have yet to find an inexpensive solid material that performs as well as liquid electrolytes at room temperature.
Instead of randomly testing individual compounds, the team turned to AI and machine learning to build predictive models from experimental data.
They trained a computer algorithm to learn how to identify good and bad compounds based on existing data, much like a facial-recognition algorithm learns to identify faces after seeing several examples.
“The number of known lithium-containing compounds is in the tens of thousands, the vast majority of which are untested,” Sendek says. “Some of them may be excellent conductors. We developed a computational model that learns from the limited data we already have, and then allows us to screen potential candidates from a massive database of materials about a million times faster than current screening methods.”
To build the model, Sendek spent more than two years gathering all known scientific data about solid compounds containing lithium.
“Austin collected all of humanity’s wisdom about these materials, and many of the measurements and experimental data going back decades,” says Evan Reed, an assistant professor of materials science and engineering and a senior author of the paper. “He used that knowledge to create a model that can predict whether a material will be a good electrolyte. This approach enables screening of the full spectrum of candidate materials to identify the most promising materials for further study.”
More than 12,000 compounds
The model used several criteria to screen promising materials, including stability, cost, abundance, and their ability to conduct lithium ions and re-route electrons through the battery’s circuit.
Candidates came from the Materials Project, a database that allows scientists to explore the physical and chemical properties of thousands of materials. The findings appear in the journal Energy & Environmental Science.
“We screened more than 12,000 lithium-containing compounds and ended up with 21 promising solid electrolytes,” Sendek says. “It only took a few minutes to do the screening. The vast majority of my time was actually spent gathering and curating all the data, and developing metrics to define the confidence of model predictions.”
The researchers eventually plan to test the 21 materials in the laboratory to determine which are best suited for real-world conditions.
“Our approach has the potential to address many kinds of materials problems and increase the effectiveness of research investments in these areas,” Reed says. “As the amount of data in the world increases and as computers improve, our ability to innovate is going to increase exponentially. Whether it’s batteries, fuel cells, or anything else, it’s a really exciting time to be in this field.”
An Office of Technology Licensing Stanford Graduate Fellowship and a seed grant from the TomKat Center for Sustainable Energy at Stanford funded the work.
Source: Stanford University