3. eQUMEC is a software to design a Li-ion battery in
details and implement a perfect simulation of Li-ion
battery response during charging and discharging. This
software is under development in QUMEC company
which is a high technology research based company
founded in 2013. A Li-ion battery has four main
components, that is to say,
anode, cathode, electrolyte
and separator. During
charging, Li ions diffuse
through cathode and
electrolyte to intercalate
into anode and vice versa in
case of discharging.
There are many variables
with effects on Li ions
diffusion through battery
component. These
variables could change
overall performance of
battery i.e. particle shape
and packing of cathodes
and anodes, used electrolyte, size of Li-ion cell,
generated temperature, intercalation stress evolution
and many more. To finding how such mentioned
variables would affect overall performance of a Li-ion
battery, a multiscale simulation methods which is
covering any details at meso and macro scales even at
atomic scales would be very helpful. eQUMEC package
is developed to cover these mentioned variable with
related well-defined multiscale algorithm.
It is not correct to claim that eQUMEC is perfect but its
multiscale algorithms were tested for several thousand
hours. These implemented
algorithms are followed by a
graphical user interface to
simulate in 3 dimensional
graphic in eQUMEC.
Any simulation in eQUMEC is
started by designing Li-ion cell
size and thickness of main
components. Then, active
materials particle shape and
density could be assigned.
Choosing electrolyte and
applying conductive/adhesive
materials would be the next
step in eQUMEC. At this time,
eQUMEC designed cell is ready to charge and
discharge. Charging and discharging is very simple in
eQUMEC and it could be performed under constant
voltage and constant current. eQUMEC has post
processing toolbox for reporting and illustrating
calculated data or exporting them to related software.
An illustration of anode, cathode, electrolyte and
separator of a Li-ion battery which is showing how Li ions
diffuse and intercalate.
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4. eQUMEC is also very useful for designing of Li-ion
micro-cell and nano-cell as well as large scale one.
Graphical interface of eQUMEC is well designed to
perform all mentioned topics simply and analyze
calculated data with ability to report them for
industrial purposes.
General interface of
eQUMEC. eQUMEC
has several toolboxes
for applying cell
shape, active
materials, electrolyte
and modules for
estimating generated
temperature, stress
evolution and
charging/discharging.
In addition, there is a
toolbox for post
processing of
calculated results.
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5. Main algorithm in eQUMEC actually has three joint
physical sections namely ion diffusion in a particle of
active material (anode and cathode), ion diffusion in
electrolyte and decision on how lithium ions cross
across the interface between active material and
electrolyte. The diffusion of lithium ions within the bulk
of active materials was simply modeled by applying
Fickian approach. But to calculate the flux of lithium
ions in electrolyte in the presence of external electrical
potential (Nernst-Planck Equation), the electrical
potential in electrolyte must be calculated by Poisson's
equation.This calculated potentialis an additionalterm
to the conventional Fickian formula to find out the flux
of lithium in electrolyte. In addition, a stochastic
boundary condition and Butler-Volmer Equation were
used to connect the two mentioned kinetic formulas in
active material and electrolyte.
Applying external potential introduces charges at the
surface of active material. According to the sign of the
charge, ions may attract to or repel from the surface of
active material in electrolyte. In general, the layer of
charged surface and counter ions is called “electric
double layer”. In the simplest model of an electric
double layer, the counter ions bind directly to the
surface and neutralize the surface charges much like in
Overall algorithm of eQUMEC for estimating current
versus time of charging and discharging
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6. a plate capacitor. During charging (discharging) in
eQUMEC, the charge surface of active materials is
positive (negative) due to the extraction of electrons by
applying external potential and the counter ions would
be like ClO4
- or FP6
-. Consequently, every lithium ions
exclude to reside as near as several nanometers at the
surface of active material and this was applied to the
lithium ions in electrolyte near to the surface of
cathode. This used concept in eQUMEC is a simple one
to handle the physics of atoms at the surface of active
material and electrolyte but efficient.
Potential in active material was assumed/considered
constant which is identical to the applied external
voltage during charging/discharging. To take into
account the potential around the surface of active
material in the electrolyte, a diffuse layer was assumed
according the Gouy-Chapman technique. Then the
Poisson's equation was solved numerically by finite
difference method (FDM). This equation and its
discretized form are as follow (Equation 1 and 2):
+ + = (1)
, , − 2 , , + , ,
∆
+
, , − 2 , , + , ,
∆
+
, , − 2 , , + , ,
∆
= (2)
Due to the dependence of ρ on , this equation was
solved iteratively by first guess on .
Diffusion of lithium ions in electrolyte was calculated
according to the Fickian approach with consideration to
account the presence of potential in electrolyte which
is introduced by external applied voltage during
charging/discharging. This mentioned modified Fickian
formula is as follow (Equation 3):
= − − ∇ ; = −∇. →
= . + ∇ (3)
Conventional Fickian approach (Equation 4) was used
and solved numerically by FDM for estimating ion
diffusion in active materials.
= − ∇ ; = −∇. → = . ( ∇ ) (4)
In addition, eQUMEC has two module for calculating
generated heat and intercalation stress during charging
according to standard computational method.
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7. eQUMEC software has been developed to design Li-ion
battery. eQUMEC has well-developed GUI for virtual
assembly of Li-ion battery components. Computational
algorithm of eQUMEC is multiscale and multi-physics
which could cover even atomic scale. Highlighted
features in this software are:
· Module for defining various shapes for active
materials powders/particles
· Applying desire coat on active materials
· Set desire shape of Li-ion cell
· Module for estimating evolution of stress and
temperature during ionic intercalation
· Applying various charging and discharging
procedures
· Database for active materials and electrolyte
materials
· Calculating capacity, current and voltage during
charging and discharging
· Module for designing cooling system
· Module to process and 3D graphic to illustrate
calculated results
· And many more
eQUMEC would be useful for battery technology and
electrical cars/motorcycle technology. eQUMEC could
be useful for academic research groups and
researchers and engineers in industry
b c d
Graphic and illustrated results in eQUMEC. (a) designed cell and its calculated voltage and capacity, (b) illustrated Li ion
concentration profile, (c) illustrated intercalation stress profile and (d) illustrated electric potential profile.
0.0
0.5
1.0
1.5
0 2 4 6 8 10 12 14 16 18
Voltage(V)
Capacity (mAh/g)
a
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8. Research to develop and improve eQUMEC is in
progress. Along improving computational algorithms
and methods in eQUMEC, this software is developing
for other and new technologies beyond Li-ion batteries
i.e. Na-ion batteries, Li-S batteries, Li-air batteries and
super capacitors.
QUMEC Company is also plan to equip eQUMEC
software with quantum mechanics first principle
method for designing and testing new active materials.
This module is almost ready. This version of eQUMEC
software would be available just for 64 bit version of
operating system and need more available continuous
random access memory which is limited this version for
professional researches.
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