In 2017 ARMA researchers began work on modeling the performance of lithium ion batteries for low temperature applications.
The modeling effort is part of an SBIR Phase II project funded by ARDEC and directed by Lithium Battery Engineering (LBE). An early product involved the creation of a deductive model utilizing both the Mean Spherical Approximation (derived from atomic radii, charge and viscosity) and the Anderko Model predicting the limiting conductivity of solutions containing multiple salts and solvents.
The research scope was further expanded to create a supporting corollary inductive model, produced utilizing an extensive set of data on various combinations of salts and solvents. Values of concentrations, temperatures and corresponding conductivities were properly organized and became accessible for modeling purposes through a developed visual basic utility. Computational methods were applied to produce regression equations for multiple salt/multiple solvent electrolytes at a wide range of temperatures and concentrations.
Current modeling effort involves coupling the above findings with the use of a molecular dynamics software to allow ARMA to produce tabulated data for conductivity of mixed electrolytes. This will be used to determine the diffusional conductivity that also considers separators with known values of porosity and tortuosity. Among the important achievements of the modeling effort will be the ability to predict the life of cells at low temperatures for various densities of electric current and ranges of cell voltage.