In order to understand the mechanics and chemistry of silicon electrodes and to prevent undesirable effects such as cracking in and dendrites formation of the anode, research have been performed using nanoscale approaches to a full nanobattery. We studied the graphite as a control calculation first and then the silicon nanocrystal anodes, performing ab initio calculations and classical molecular dynamics atomistic simulations. In this effort in progress, we are focusing on the mechanical properties, such as swelling, alloying mechanism, amorphization, cracking, and dendriting of the anode material during the charging cycle and also the electrical properties such as polarization as well as ionic and electronic conductance. The nanobattery includes LiCoO2 cathode; the electrolyte solution contains ethylene carbonate, as well as hexafluorophosphate and Li-ions. An external electric field is applied to emulate the charging process causing the migration of the Li-ions from the cathode, diffusing through the electrolyte to finally get into the anode. We immediately observe during charging (i.e., when an external electric field is applied) of the nanobattery, the Si anode changes gradually into a LiSi alloy at temperatures below 360 K. We obtained the drift velocity of the Li-ions during the amorphization of the silicon nanocrystal as the original volume of the anode increases. For the graphite anode, the full lithiated state is achieve when the initial structure C changes into LiC6, storing the Li-ion between the layers of the graphite, thus we were able to compare energy, temperature, and electrical properties such as current, resistance, current density, conductivity and resistivity. Our model can be used to study the mechanisms taking place in the electrolyte, cathode, and anode; especially, for new materials such as solid electrolytes.

Analysis, design and simulation of nanobatteries: Silicon anodes and beyond

254th National Meeting (2017)

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