(352j) Atomistic modeling of metallic anodes in beyond Li-ion batteries

The lithium-ion (Li-ion) battery has revolutionized the consumer electronics industry in the past two decades, achieving moderate battery lifetimes and higher energy storage densities. However, we have begun to reach the limits to improvements in Li-ion batteries. Further, in order to reach the energy demands posed by the transportation industry, batteries that possess energy densities much larger than current state-of-the-art Li-ion technologies are highly desirable. This research investigates two ‘beyond Li-ion’ battery technologies that boast theoretical energy densities more than five times larger than Li-ion batteries: batteries employing (i) metallic Mg anodes and (ii) metallic Li anodes. We used density functional theory to probe atomistic interactions on each of these metallic surfaces. For the metallic Mg anode, we identified likely reactions between the anode surface and the battery solvent. The composition of the model Mg anode surface was modified to mimic realistic electrode surfaces. We found that solvent decomposition products and reaction energies were highly dependent on the model anode surface composition, with the pristine Mg anode displaying a greater tendency for solvent decomposition. For the metallic Li anode, we have modeled the interface between Li metal and its native oxide using a crystalline Li/Li₂O slab model and an oxidized slab model in which the native oxide layer was dynamically grown on the Li metal slab. We show the effect of this native oxide layer on the transport properties in each model. Taken together, these studies provide a more complete picture of the atomic-scale factors governing the successful implementation of metallic anodes for beyond Li-ion batteries.