We investigated tin perovskites (ASnX3) for lithium-ion batteries by analyzing their intercalation energy, formation energy, octahedral distortion factor, etc. We hope to utilize these data to establish a machine learning model to help us fast predict the intercalation energy of other tin-based perovskites.

1. Jiankun Pu[1],[2], Omar Allam[1],[2], Jihoon Kim[1],[2], Prof. Seung Soon Jang[1],*
1. Computational NanoBio Technology Lab., School of Materials Science and Engineering, Georgia Institute of Technology
2. The George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology
Exploring prospective materials for efficient energy
production and storage has become a crucial challenge
in this century. Among the emerging materials, hybrid
organic-inorganic perovskites (HIOPs) have attracted
intensive attention especially in optoelectronic
application in the past few years, but the use of
perovskite in Li-ion batteries (LIBs) has only been
recently examined. Specifically, the use of lead based
HOIPs as the anode materials of LIBs has been the main
focus of most recent studies. The electrochemical
performance of CH3NH3PbBr3 at a current density of 200
mA g-1 shows a promising discharge capacity of 331.8
mA h g-1 [1]. However, due to the toxicity of lead a
number of possible environmental concerns
overshadowed the advantages of lead-based perovskite
materials. To address this toxicity issue, intensive recent
research effort has been devoted to developing low-
toxic metal halide perovskites.
Computational Methods
Motivation
In this study, three parameters
are taken to evaluate
the performance matrix.
 First, the formation energy: the
energy to form a 2x2x2 cubic
form perovskite is calculated
(since cubic Perovskites are
considered stable[1]). The goal
is to compare the stability of
the proposed perovskites
materials.
 Second, the volume
change: the volume of the
alternative perovskites after
inserting different
concentrations of lithium ions
are studied. Lower volume
change compared to pristine
perovskite indicates lower
stresses during the insertion.
 Third, intercalation energy of
different concentrations of
lithium ion insertion is
calculated to reflect the the
stability and the capacity of the
materials after charging.
Methylammonium Lead X (X=Bromide, Chloride and
Iodide) (MAPbX3) with 𝐴𝐴𝐵𝐵𝑋𝑋3 cubic Perovskite structure
has shown promise for use as the anode material in
energy storage device, but the use of lead in the
material possesses toxicity to the environment. In
addressing the toxicity of lead-based perovskite
materials and exploring the electrochemical properties
of other perovskite materials, this work investigate
organic-inorganic perovskites that have the same
structure as MAPbX3, but composed of different "A"
materials such as Cs and HC(NH2)2
+ (FA+) and different
"B" material such as Sn. These composites may have
similar electrochemical properties but greatly reduce
the impact of the environment compared to MAPbX3.
Furthermore, the results of this study can provide
insights on the use of non-toxic perovskites in LIBs.
MASnBr3, MASnCl3, MASnI3
CsSnBr3, CsSnCl3, CsSnI3
FASnBr3, FASnCl3, FASnI3
Possible new battery anode
materials that are less toxic
than lead-based perovskites
but possess better
electrochemical properties
Perovskite Structure Determination
Periodic boundary conditions using a = b = c
were tested for the Perovskites phases.
a , b, and c, as well as atomic positions,
were obtained from crystallographic data.
90° was used for each angle.
Lithium-Ion Concentration
1 lithium-ion, 4 lithium-ions and 8 lithium-
ions per 2x2x2 super cell were tested (LiyABX3
y = 0.125, 0.5 and 1).
Different concentrations are chosen to
evaluate the change of electrochemical
properties while charging/discharging.
Lithium-Ion Intercalation Sites
Intercalation locations at octahedral sites and
tetrahedral sites are chosen to investigate the
most possible intercalation location.[1]
Among two intercalation sites, different
variation of octahedral and tetrahedral
intercalation sites are considered due to
Methylammonium’s asymmetrical geometry
Lithium Insertion Locations
Computational Methods
Modeling Software: Materials Studio
Calculation:
 Density Functional Theory (DFT) using
DMoL3/CASTEP.
 PBE GGA functional.
 Core Electron Interactions between ionic
cores/electrons described by: Norm-
conserving
 k-point set: 2x2x2
 Energy Cutoff: 700eV
 Geometry Optimization Algorithm:
Broaden-Fletcher-Goldfard-Shanno
Analysis Methods:
 Geometric Optimization using periodic
boundary conditions
 Energy Calculation
⁕ Formation Energy and Intercalation
Energy[1].
𝑬𝑬𝒇𝒇𝒇𝒇𝒇𝒇𝒇𝒇𝒇𝒇𝒇𝒇𝒇𝒇𝒇𝒇 𝒇𝒇 =
𝟏𝟏
𝑵𝑵
𝑬𝑬𝑨𝑨𝑨𝑨𝑿𝑿𝟑𝟑
− 𝑬𝑬𝑨𝑨 + 𝑬𝑬𝑩𝑩 + 𝟑𝟑𝑬𝑬𝑿𝑿
N is the number of unit cells, EABX3
is the
energy of the pristine perovskites,EA is the
energy of an “A” material, EB is the energy of a
“B” element and EX is the energy of a “X”
element.
𝑬𝑬𝒊𝒊𝒊𝒊𝒊𝒊𝒊𝒊𝒊𝒊𝒊𝒊𝒊𝒊𝒊𝒊𝒊𝒊𝒊𝒊𝒊𝒊𝒊𝒊𝒊𝒊 =
𝟏𝟏
𝒏𝒏
𝑬𝑬𝑳𝑳𝒊𝒊𝒚𝒚 𝑨𝑨𝑨𝑨𝑿𝑿𝟑𝟑
− 𝑬𝑬𝑨𝑨𝑨𝑨𝑿𝑿𝟑𝟑
+ 𝒏𝒏𝑬𝑬𝑳𝑳𝒊𝒊+
𝑛𝑛 is the number of Li+ inserted, 𝐸𝐸𝐿𝐿𝑖𝑖𝑦𝑦 𝐴𝐴𝐴𝐴𝑋𝑋3
is the
energy of the y concentration Li intercalated
perovskites, 𝐸𝐸𝐴𝐴𝐴𝐴𝑋𝑋3
is the energy of the pristine
perovskites, 𝐸𝐸𝐿𝐿𝑖𝑖+ is the energy of a 𝐿𝐿𝑖𝑖+
Jihoon Kim
B.S. Mechanical Engineering
Georgia Institute of Technology
E-mail: jkim3187@gatech.edu
Using the method developed, the rest of the
proposed Perovskites compound (FA+) and
different Li + intercalation concentration (y=0.125,
0.5) will be examined.
The mechanism of volume contraction will be
examined by tracing the interaction between
atoms when studied different intercalation
concentration.
Molecular dynamics simulations can be conducted
to offer highly useful insight regarding lithium
mobility in the perovskite framework and how this
is affected by composition of the perovskite.
Band structures can be investigated and added as
another parameters in the property matrix for
battery application.
Schematic of the
Simulation Process
Tetrahedral Sites Octahedral Sites
Close to Carbon
(T1)
Close to Nitrogen
(T2)
Back to Back
(O1)
Parallel
(O2)
*Note: Atoms’ radius are adjusted for better visualization purposes
Formation Energy Analysis of Pristine Perovskites Structure
Materials:
The discrepancy of formation energy indicates a more stable
compounds of the tin-based material then the lead-based
perovskite.
The formation energy of MASnX3 is significantly higher than that
of CsSnX3, although the energy of Cs is higher than that of
CH3NH3.
 The difference might be due to the radius of CH3NH3 is larger
than Cs.
Perovskites (CsSnX3, MASnX3) with novel
electrochemical properties were identified.
MASnX3, CsSnX3 are more stable compounds.
MASnX3 and CsSnX3 show much more subtle
geometric distortions.
The intercalation energy of MAPbX3 and CsSnX3 are
similar, thereby showing possible similar after-
charging stabilities and comparable discharge
capacities.
The volume change of CsSnX3 is the lowest among
all tested compounds. The lowest volume change
may indicate a better life-cycle as the anode material
compared to MAPbX3. However, the overall volume
contraction for all tested Perovskites may lead to a
poorer ionic conductivity after insertion.
CsSnCl3 may be the most favorable material for
energy storage because it shows similar
intercalation energy compared to MAPbCl3, the
lowest volume change and lowest geometric
distortion, which indicates that it will experience the
lowest amount of stress during charge/discharge
process.
Geometric Optimization
Geometric Optimization was performed on the proposed Perovskite
compounds (CsSnBr3, CsSnCl3, CsSnI3, MASnBr3, MASnCl3, MASnI3).
It was also performed on the lead-based Perovskite compounds
(MAPbBr3, MAPbCl3,MAPbI3) for comparison.
Geometric Distortion Analysis of
Perovskites after Li+ insertion:
The geometric distortion for
MASnX3 is less rigorous than
that of MAPbX3
 The less distortion possibly
indicating a less rigorous
conversion reaction or even
an absence of such reaction
because the geometric
changes are subtle[1].
 The less distortion also
indicates a possible less stress
imposed on the compounds.
MAPbBr3 MAPbCl3 MAPbI3
MASnBr3 MASnCl3 MASnI3
Volume Change Analysis of the Perovskites Structure Materials:
A volume reduction occurs to every tested Perovskites after
insertion.
Intercalation Energy Analysis of Pristine Perovskites Structure
Materials:
Changing the lead-based Perovskites to the tin-based perovskites
shows decreases in intercalation energy.
MAPbX3 and CsSnX3 show similar intercalation energy.
Overall, intercalation energy is lower for Octahedral Li+ insertion,
which shows that Li + is most possible to located at the octahedral
location in the Perovskites after charging.
[1] Dawson, J., Naylor, A., Eames, C., Roberts, M., Zhang,
W., Snaith, H., Bruce, P. and Islam, M. (2017).
Mechanisms of Lithium Intercalation and Conversion
Processes in Organic–Inorganic Halide Perovskites. ACS
Energy Letters, 2(8), pp.1818-1824.
Background
Motivation
Objectives
Method Results and Discussions Conclusion
Future Work
Contact Information
Jiankun Pu
B.S. Mechanical Engineering
Georgia Institute of Technology
E-mail: jpu31@gatech.edu
Omar Adel Allam
Ph.D. Candidate
Mechanical Engineering
Georgia Institute of Technology
E-mail: oallam3@gatech.edu
Prof. Seung Soon Jang
Associate Professor,
School of Material Science Engineering
Georgia Institute of Technology
E-mail: seungsoon.jang@mse.gatech.edu
Acknowledgement
Special thanks to Dr. Seung Soon Jang for his
supervisions and guidance
Reference
CsSnBr3 CsSnCl3 CsSnI3