Designing the best molecular building blocks for battery
components is like trying to create a recipe for a new kind of cake, when you have billions of potential ingredients. The challenge involves determining which ingredients work best together — or, more simply, produce an edible (or, in the case of batteries
, a safe) product. But even with state-of-the-art supercomputers, scientists cannot precisely model the chemical characteristics of every molecule that could prove to be the basis of a next-generation battery material. For more information see the IDTechEx report on Li-ion Batteries 2018-2028
As described in two new papers, Argonne researchers first created a highly accurate database of roughly 133,000 small organic
molecules that could form the basis of battery electrolytes. To do so, they used a computationally intensive model called G4MP2. This collection of molecules, however, represented only a small subset of 166 billion larger molecules that scientists wanted to probe for electrolyte candidates.
"If we are going to use a molecule for energy storage applications, we need to know properties like its stability, and we can use this machine learning to predict properties of bigger molecules more accurately." said Argonne chemist Rajeev Assary.
Because using G4MP2 to resolve each of the 166 billion molecules would have required an impossible amount of computing time and power, the research team used a machine learning algorithm
to relate the precisely known structures from the smaller data set to much more coarsely modeled structures from the larger data set.
"When it comes to determining how these molecules work, there are big tradeoffs between accuracy and the time it takes to compute a result," said Ian Foster, Argonne Data Science and Learning division director and author of one of the papers. "We believe that machine learning represents a way to get a molecular picture that is nearly as precise at a fraction of the computational cost."
To provide a basis for the machine learning model, Foster and his colleagues used a less computationally taxing modeling framework based on density functional theory, a quantum mechanical modeling framework used to calculate electronic structure in large systems. Density functional theory provides a good approximation of molecular properties, but is less accurate than G4MP2.
Refining the algorithm to better ascertain information about the broader class of organic molecules involved comparing the atomic positions of the molecules computed with the highly accurate G4MP2 versus those analyzed using only density functional theory. By using G4MP2 as a gold standard, the researchers could train the density functional theory model to incorporate a correction factor, improving its accuracy while keeping computational costs down.
"The machine learning algorithm gives us a way to look at the relationship between the atoms in a large molecule and their neighbors, to see how they bond and interact, and look for similarities between those molecules and others we know quite well," said Argonne computational scientist Logan Ward, an author of one of the studies. "This will help us to make predictions about the energies of these larger molecules or the differences between the low- and high-accuracy calculations."
"This whole project is designed to give us the biggest picture possible of battery electrolyte candidates," added Argonne chemist Rajeev Assary, an author of both studies. "If we are going to use a molecule for energy storage applications, we need to know properties like its stability, and we can use this machine learning to predict properties of bigger molecules more accurately."
Source: Argonne National Laboratory
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