scholarly journals Stability of Calcium Ion Battery Electrolytes: Predictions from Ab Initio Molecular Dynamics Simulations

2021 ◽  
Author(s):  
Sharma Yamijala ◽  
Hyuna Kwon ◽  
Juchen Guo ◽  
Bryan Wong
Keyword(s):  
Molecular Dynamics ◽  
Calcium Ion ◽  
Lithium Ion ◽  
Zinc Ion ◽  
Time Dependent ◽  
Ab Initio Molecular Dynamics ◽  
Elastic Band ◽  
Energy Storage Devices ◽  
The Stability ◽  
Dynamics Simulations

<p>Multivalent batteries, such as magnesium-ion, calcium-ion, and zinc-ion batteries, have attracted significant attention as next-generation electrochemical energy storage devices to complement conventional lithium-ion batteries (LIBs). Among them, calcium-ion batteries (CIBs) are the least explored due to the difficult reversible Ca deposition-dissolution. In this work, we examined the stability of four different Ca salts with weakly coordinating anions and three different solvents commonly employed in existing battery technologies to identify suitable candidates for CIBs. By employing Born-Oppenheimer molecular dynamics (BOMD) simulations on salt-Ca and solvent-Ca interfaces, we find that the tetraglyme solvent and carborane salt are promising candidates for CIBs. Due to the strong reducing nature of the calcium surface, the other salts and solvents readily decompose. We explain the microscopic mechanisms of salt/solvent decomposition on the Ca surface using time-dependent projected density of states, time-dependent charge-transfer plots, and climbing-image nudged elastic band calculations. Collectively, this work presents the first mechanistic assessment of the dynamical stability of candidate salts and solvents on a Ca surface using BOMD simulations, and provides a predictive path toward designing stable electrolytes for CIBs. </p> <p> </p>

scholarly journals Stability of Calcium Ion Battery Electrolytes: Predictions from Ab Initio Molecular Dynamics Simulations

2021 ◽  
Author(s):  
Sharma Yamijala ◽  
Hyuna Kwon ◽  
Juchen Guo ◽  
Bryan Wong
Keyword(s):  
Molecular Dynamics ◽  
Calcium Ion ◽  
Lithium Ion ◽  
Zinc Ion ◽  
Time Dependent ◽  
Ab Initio Molecular Dynamics ◽  
Elastic Band ◽  
Energy Storage Devices ◽  
The Stability ◽  
Dynamics Simulations

<p>Multivalent batteries, such as magnesium-ion, calcium-ion, and zinc-ion batteries, have attracted significant attention as next-generation electrochemical energy storage devices to complement conventional lithium-ion batteries (LIBs). Among them, calcium-ion batteries (CIBs) are the least explored due to the difficult reversible Ca deposition-dissolution. In this work, we examined the stability of four different Ca salts with weakly coordinating anions and three different solvents commonly employed in existing battery technologies to identify suitable candidates for CIBs. By employing Born-Oppenheimer molecular dynamics (BOMD) simulations on salt-Ca and solvent-Ca interfaces, we find that the tetraglyme solvent and carborane salt are promising candidates for CIBs. Due to the strong reducing nature of the calcium surface, the other salts and solvents readily decompose. We explain the microscopic mechanisms of salt/solvent decomposition on the Ca surface using time-dependent projected density of states, time-dependent charge-transfer plots, and climbing-image nudged elastic band calculations. Collectively, this work presents the first mechanistic assessment of the dynamical stability of candidate salts and solvents on a Ca surface using BOMD simulations, and provides a predictive path toward designing stable electrolytes for CIBs. </p> <p> </p>

Spontaneous Formation and Stability of GaP Cage Structures: A Theoretical Prediction of a New Fullerene

2001 ◽  
Vol 675 ◽  
Author(s):  
Francesco Buda ◽  
Valentina Tozzini ◽  
Annalisa Fasolino
Keyword(s):  
Molecular Dynamics ◽  
Theoretical Prediction ◽  
Ab Initio Molecular Dynamics ◽  
Fullerene Cage ◽  
Spontaneous Formation ◽  
Energy Gaps ◽  
Bulk Structure ◽  
The Stability ◽  
Dynamics Simulations ◽  
Geometric And Electronic Properties

ABSTRACTWe report the spontaneous formation of a GaP fullerene cage in ab-initio Molecular Dynamics simulations starting from a bulk fragment. A systematic study of the geometric and electronic properties of neutral and ionized III-V (GaP, GaAs, AlAs, AIP) clusters suggests the stability of hetero-fullerenes formed by compounds with zincblend bulk structure. Our prediction is supported by several indicators: these clusters show closed electronic shells and relatively large energy gaps; the ratio between the cohesive energy per atom in the cluster and in the bulk is very close to the value found for carbon fullerenes of the same size; the clusters are thermally stable up to a temperature range of 1500–2000 K and they do not dissociate when ionized.

STRUCTURE AND STABILITY OF ENDOHEDRAL Cn@C60

2010 ◽  
Vol 24 (12) ◽  
pp. 1255-1266 ◽  
Author(s):  
REENA DEVI ◽  
RANJAN KUMAR
Keyword(s):  
Molecular Dynamics ◽  
Charge Transfer ◽  
Free Space ◽  
Chemical Reactivity ◽  
Bond Formation ◽  
Carbon Cluster ◽  
Ab Initio Molecular Dynamics ◽  
Carbon Clusters ◽  
The Stability ◽  
Dynamics Simulations

We report ab initio molecular dynamics simulations of carbon clusters in free space and inside C 60 using SIESTA. We have studied the stability and geometries of small carbon clusters consisting of 2–12 carbon atoms inside the C 60 molecule and in free space by optimizing the atomic geometries. We have found that the C – C bond length is in agreement with the 1.40 and 1.45 values reported earlier. We find that the clusters inside the C 60 are more stable than clusters in free space. Binding energy per carbon atom initially increases with number of carbon atoms in the cluster and then decreases after maximizing for the 9-atom cluster. For more than 9 carbon atoms in the cluster inside C 60, C atoms of the cluster start forming bond with the C 60 cage and the C 60 structure gets distorted. We have done calculations for charge transfer and chemical reactivity. The calculations of ionization potential and electron affinity show that clusters in free space are less reactive compared with C n@ C 60. Charge transfer calculations show that the bond formation of C atoms with the C 60 cage is accompanied with a transfer of charge from carbon cluster to C 60.

Alloying of Alkali Metals with Tellurene

2020 ◽  
Author(s):  
Rishabh Jain ◽  
Yifei Yuan ◽  
Yashpal Singh ◽  
Swastik Basu ◽  
Dawei Wang ◽  
...  
Keyword(s):  
Density Functional ◽  
Alkali Metals ◽  
Lithium Ion ◽  
Poor Performance ◽  
Ab Initio Molecular Dynamics ◽  
Elastic Band ◽  
Volumetric Capacity ◽  
Transmission Electron ◽  
Practical Capacity ◽  
Dynamics Simulations

Abstract Graphite is ubiquitous as the anode material in lithium-ion batteries, but offers relatively low volumetric capacity (330 to 430 mAh cm-3). By contrast, Tellurene (Te) is expected to alloy with alkali metals with high volumetric capacity (~2620 mAh cm-3), but to date there is no detailed study on its alloying behavior. In this work, we have investigated the alloying response of a range of alkali metals (A = Li, Na or K) with few-layer Te. In-situ transmission electron microscopy and density functional theory both indicate that Te alloys with alkali metals forming A2Te. However, the crystalline order of alloyed products varied significantly from single-crystal (for Li2Te) to polycrystalline (for Na2Te and K2Te). It is well established that typical alloying materials (e.g., silicon, tin, black phosphorous) lose their crystallinity when reacted with Li. The ability of Te to retain its crystallinity is therefore surprising. Nudged elastic band calculations and ab-initio molecular dynamics simulations reveal that compared to Na or K, the migration of Li is highly “isotropic” in Te, enabling its crystallinity to be preserved. Such isotropic Li transport is made possible by Te’s peculiar structure comprised of chiral chains bound by van der Waals forces. To evaluate the electrochemical performance of Te, we tested Te electrodes in half-cells vs Li/Na/K metal. While alloying with Na and K showed poor performance, with Li, the Te electrode exhibited a volumetric capacity of ~700 mAh cm-3, which is about two-times the practical capacity of commercial graphite. Such Te based batteries could play an important role in applications where high volumetric energy and power density are of paramount importance.

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