equmec catalog
TRANSCRIPT
eQUMEC Beta version
Software for Li-ion battery technology and beyond
CONTENTS
What is eQUMEC?
Simulation Features
eQUMEC Benefits
Closing Remarks
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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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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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 potential is an additional term 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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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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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
Volta
ge (V
)
Capacity (mAh/g)
a
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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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