Geometric and electronic studies of Li15Si4 for silicon anode

“…Since cracking takes place when the silicon anode is almost or totally lithiated, a previously lithiated silicon anode with a Li : Si ratio of 21 : 5 is used. At this ratio, the lithiated Si already shows metallic properties, 39 and we simulate the ow of lithium ions on this surface under the effects of an electric eld. Thus, this work focuses on elucidating the conditions for dendrite growth, conditions before the growth are assumed, and conditions that do not lead to growth are ignored.…”

Section: -38mentioning

confidence: 99%

Dendrite formation in silicon anodes of lithium-ion batteries

Selis

Seminario

2018

RSC Adv.

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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.

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“…Among them, Si was paid considerable attention because of its higher theoretical specific capacity (~3579 mA h g -1 for Li 15 Si 4 at room temperature), low cost and abundant resources. However, there is an apparent shortcoming, i.e., Si is easily pulverized upon charging and discharging due to the large volume expansion and shrinkage 3,4,9,10 .…”

Section: Introductionmentioning

confidence: 99%

“…It is widely accepted that during the first lithiation cycle, crystalline Si undergoes a phase transition to form an amorphous Li x Si, but the amorphous Li x Si alloys can transform into crystalline Li 15 Si 4 when the Li content is x=3.75 9,21,22 . The mechanism of the amorphization process was investigated by Wang et al 23 using both theoretical analysis and in-situ transition electron microscopy observation.…”

Section: Introductionmentioning

confidence: 99%

Atomistic Study of Lithium Ion Dynamics in Li12Si7

Shi

Wang

2015

Electrochimica Acta

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Geometric and electronic studies of Li15Si4 for silicon anode

Cited by 59 publications

References 26 publications

First principles study of Li–Si crystalline phases: Charge transfer, electronic structure, and lattice vibrations

First principles study of Li–Si crystalline phases: Charge transfer, electronic structure, and lattice vibrations

Dendrite formation in silicon anodes of lithium-ion batteries

Atomistic Study of Lithium Ion Dynamics in Li12Si7

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