Dendrite formation in silicon anodes of lithium-ion batteries

Abstract

Rechargeable lithium-ion batteries require a vigorous improvement if we want to use them massively for high energy applications. Silicon and metal lithium anodes are excellent alternatives because of their large theoretical capacity when compared to graphite used in practically all rechargeable Li-ion batteries.However, several problems need to be addressed satisfactorily before a major fabrication effort can be launched; for instance, the growth of lithium dendrites is one of the most important to take care due to safety issues. In this work we attempt to predict the mechanism of dendrite growth by simulating possible behaviors of charge distributions in the anode of an already cracked solid electrolyte interphase of a nanobattery, which is under the application of an external field representing the charging of the battery; thus, elucidating the conditions for dendrite growth. The extremely slow drift velocity of the Li-ions of $1 mm per hour in a typical commercial Li-ion battery, makes the growth of a dendrite take a few hours; however, once a Li-ion arrives at an active site of the anode, it takes an extremely short time of $1 ps to react. This large difference in time-scales allows us to perform the molecular dynamics simulation of the ions at much larger drift velocities, so we can have valuable results in reasonable computational times. The conditions before the growth are assumed and conditions that do not lead to the growth are ignored. We performed molecular dynamics simulations of a pre-lithiated silicon anode with a Li : Si ratio of 21 : 5, corresponding to a fully charged battery. We simulate the dendrite growth by testing a few charge distributions in a nanosized square representing a crack of the solid electrolyte interphase, which is where the electrolyte solution comes into direct contact with the LiSi alloy anode.Depending on the selected charge distributions for such an anode surface, the dendrites grow during the simulation when an external field is applied. We found that dendrites grow when strong deviations of charge distributions take place on the surface of the crack. Results from this work are important in finding ways to constrain lithium dendrite growth using tailored coatings or pre-coatings covering the LiSi alloy anode.

Dendrite formation in Li-metal anodes: an atomistic molecular dynamics study

“…Therefore, we use the same MEAM force eld parameters of Li-Li interactions for the interaction between both Limetal and Li + at distances smaller than 2.5 A. E c is the energy per atom, z is the number of nearest neighbors in the reference structure and r c is the cut off distance. The equilibrium distance in a lithium diatomic molecule using a MEAM force eld is 2.419 A, 40 which is close to the experimental distance of 2.672 A. 41 The interactions among the SEI (LiF) atoms are modeled with the Born-Mayer potential, 42…”

“…The interactions between Li-metal atoms and Li-metal atoms with Li + ions are modeled by a second nearest-neighbor (2NN) embedded MEAM force eld, 38,39 as it was used in a previous work. 40 The MEAM interaction is given by the equation:…”

Thermally driven mesoscale chemomechanical interplay in Li0.5Ni0.6Mn0.2Co0.2O2 cathode materials

“…Commonly observed local chemical events include but are not limited to local overcharge/overdischarge, 14,15 oxygen release, 16 local structural transformation, 8,17 domain deactivation, 18 transition metal dissolution/precipitation, 6,8,19,20 and dendrite/whisker/protrusion growth. 21,22 The local regions that undergo these undesired chemical reactions may not account for much of the total mass or volume of the battery materials, but they can significantly impact the deliverable energy through impedance growth as well as undermine the safety characteristics of the battery cells through thermal runaway. 23,24 Oxygen release from charged nickel-rich LiNi1-x-yMnxCoyO2 (NMC) layered oxides, either through gas evolution or participating in electrolyte oxidation, has been reported under thermal abuse conditions 25,26 and aggressively charging to high voltages.…”

Boosting the Optimization of Lithium Metal Batteries by Molecular Dynamics Simulations: A Perspective

“…Finally, molecular simulation can be used to explain the factors affecting the formation of lithium dendrites which contains Reproduced with permission. [83] Copyright 2018, Royal Society of Chemistry. current density, temperature, electrolyte components and electrode morphology in microcosmic.…”