Mark Verbrugge, General Motors R&D Center
Needs and Challenges Associated with High Energy Batteries with an Emphasis on Thermodynamic Underpinnings
Written by Aashutosh Mistry
Lithium-ion batteries (LIBs) represent one of the most successful cell chemistry. Their spread in the commercial market is in part due to lucrative energy/power-to-size scaling, close to 100% reversibility and a reasonable cycle life. Storage of electrochemical energy in electrode materials takes place via intercalation, which in itself is considerably different and far more complex than traditional solution phase electrochemistry. This makes the fundamental understanding of LIB materials challenging as well as interesting.
Toward this end, Mark Verbrugge at General Motors research center has been working on a “thermodynamically consistent” description of intercalation electrodes. Such a formalism ties together experimental material behavior with a minimal set of functional relations, and its usefulness goes much beyond estimation of battery state of charge from mere voltage measurement.
The bulk of the electrode rather contains multiple lithium intercalated phases with well-defined stoichiometries for many of the materials. During lithiation addition/removal (i.e., charging/discharging of batteries) to such electrodes, mutual interaction of such phases governs the material and subsequently cell response. For electric (and hybrid) vehicle applications, batteries are expected to meet sudden changes in current being drawn (which coincides with acceleration, braking, changes in road condition, and variations in cooling load for example). Verbrugge’s work is extremely helpful in understanding this complex dynamics of the electrode and subsequently in improving the electrode design as well as the design of the battery management system (BMS), which all combined together pushes the limits of automobile performance and cost.