Document 6516286

EC Power
200 Innovation Blvd.
State College, PA, 16803, USA
[email protected]
Phone: +1-814-861-6233
What is Different about AutoLionTM Compared to Other Li-Ion
Battery Softwares?
temperature and Li concentration are taken from
in-built database. AutoLion’s materials database
consists of validated properties for common Liion battery electrolyte, cathode materials (NCM,
LFP, LMO, and LCO), and anode materials
(graphite and LTO).
Ambient temperature is -20oC with constant
current discharge operating condition at C/3, 1C
and 3C rates.
Three cases are simulated. The only difference in
the three cases are heat transfer boundary
conditions 1) cell with natural convection (heat
transfer coefficient, h, to ambient is 20 W/m2K)
to ambient, mimicking experiment in an
environmental chamber with no active cooling; 2)
Adiabatic thermal boundary condition for cell;
and 3) Isothermal simulation.
Starting SOC is 100%
Depth of Discharge is defined as used capacity
discharged normalized by room temperature cell
capacity at very low C-rate room temperature
Introduction
We commonly get these questions while interacting
with engineers and researchers: “What is different
about AutoLionTM over other Li-ion battery
softwares?” and “If there is any difference between
AutoLionTM and Classic Newman model?”. There are
many differences in the modeling approach of
AutoLion™ over other software offerings. These
differences largely stem from the coupled treatment
of heat and electrochemistry in AutoLionTM that is
largely absent (in isothermal Newman model) or is
over-simplified (derivatives of Newman model with
simplified thermal treatment) in other softwares. This
has a very little effect on room temperature
performance simulation, but under extreme
temperature (very common for automotive
applications)- especially for large format cells with
large surface area to volume ratio- it becomes a major
distinguishing feature for AutoLion™. This case
study is aimed at highlighting this very important
issue.




Results
Technology Used
Voltage (0.33C)
Voltage (1C)
Voltage (3C)
Temperature (0.33C)
Temperature (1C)
Temperature (3C)
4.5
25
4
15
3.5
3
5
2.5
2
-5
1.5
1
Temperature (oC)
Constant current discharge at -20oC is simulated with
AutoLionTM that has tight coupling of heat and
electrochemistry. Simulations are also executed using
the isothermal option in AutoLion™. Isothermal
model option in AutoLionTM makes the predicted
behavior is similar to common competing isothermal
models.
Voltage (V)
Problem Statement
-15
0.5
AutoLion-STM
0
-25
0
0.2
0.4
0.6
0.8
1
Depth of Discharge
Setup
 A 2.2 Ah NCM-Gr 18650 cell with material
loading of 3.9 mAh/cm2 and 4.5 mAh/cm2 in
cathode and anode, respectively.
 Cell NP ratio is 1.15 with single side electrode
thickness of 77 µm and 81 µm for cathode and
anode, respectively.
 All the material properties for NMC and graphite
material as well as for electrolyte as a function of
Figure 1 AutoLion™ non-isothermal simulated
cell voltage and temperature as a function of cell
depth of discharge with heat transfer coeff, h, to
ambient as 20 W/m2K that represent natural
convection. Ambient temperature is -20oC.
© 2014 EC Power, LLC. All Rights Reserved.
EC Power
200 Innovation Blvd.
State College, PA, 16803, USA
[email protected]
Phone: +1-814-861-6233
anode
cathode
separator
0.33C
1C
3C
Figure 2 Simulated cell voltage as a function of
cell depth of discharge using isothermal model.
Ambient temperature is -20oC.
h = 0W/m2K
h = 20W/m2K
Isothermal
Figure 3 Simulated voltage and temperature for
1C constant current discharge operation at -20oC
ambient. Simulation results are for three different
values of heat transfer coeff to ambient.
anode
cathode
separator
Figure 4 Simulated electrolyte concentration
distribution along cell thickness for DOD of 0.2.
Simulation results corresponds to 1C discharge
with ambient temperature of -20oC
Figure 5 Simulated Li stoichiometry at active
material particle surface along cell thickness for
DoD of 0.2. Simulation results corresponds to 1C
discharge with ambient temperature of -20oC
Benefits and Conclusions
 Li-ion battery performance, especially under
extreme temperature conditions, strongly depends
on temperature. To correctly simulate cell
performance/life under such extreme conditions,
tight coupling between heat transport and cell
electrochemical reaction is absolutely important.
 AutoLion™ captures this important physics that
common isothermal models or models with
simplified heat transport treatment, commonly
used in other software, cannot.
 As shown in Figs. 4 and 5, under isothermal
conditions, electrolyte depletion in cathode and Li
stoichiometry depletion in anode particles clearly
limits the cell operation at DoD ~ 0.2 (for 1C
discharge). However, under more practicallyrelevant thermal conditions, the cell can continue
to discharge at least 4x as long (DoD ~ 0.8 under
natural convection conditions). As captured by
AutoLionTM, this 4x+ increase in discharge length
is due to cell internal-heating, which cannot be
properly captured with isothermal and simplified
models, and therefore cannot accurately guide
users in optimizing cell design under automotive
conditions.
 AutoLion™ has capabilities of not only
simulating performance over wide range of
operating conditions but has demonstrated very
good agreement with experimental data. Users are
encouraged to refer to other case studies for more
details.
 One example of how an academic client has used
AutoLion™ to investigate the low-temperature
performance of Li-ion batteries can be found in
© 2014 EC Power, LLC. All Rights Reserved.
EC Power
200 Innovation Blvd.
State College, PA, 16803, USA
[email protected]
Phone: +1-814-861-6233
reference [1]. Other papers where authors have
used
AutoLion™
to
investigate
the
electrochemical-thermal coupled performance of
Li-ion batteries can be found at the publications
link on our website.
References
[1] Ji, Y., Zhang, Y., and Wang, C.Y. (2013). “Li-Ion
operation at low temperatures,” Journal of the
Electrochemical Society, 160(4), A636-A649.
© 2014 EC Power, LLC. All Rights Reserved.