Quantum mechanically guided design of amorphous Si–Al–M (M = 3d metals) anodes for Li ion batteries

Abstract

Molecular dynamics simulations based on density functional theory have been systematically performed to study amorphous Si37.5Al51.7M10.8 anodes (M=3d metals) for Li ion batteries. All anode materials studied possess a factor of ~10 larger volumetric capacities than graphite. Furthermore, they exhibit an order of magnitude reduced volume expansion upon Li incorporation (in the order of 1%) compared to graphite (12%). The V-containing anode is found to show the highest Li mobility. The high Li mobility may be explained by a fivefold weaker interaction between Li and the matrix elements compared to graphite. Si35.4Al55.9V8.7 and Si35.2Al55.5Co9.3 amorphous thin film anodes were synthesized by magnetron sputtering and their volumetric capacities were measured. In spite of a large capacity drop after the first cycle, their initial discharge volumetric capacities are superior to graphite and comparable to those of pure Si with equivalent thickness.