Combined electrochemical and thermal modelling with COMSOL ...

Combination of electrochemical-calorimetric studies on cylindrical lithium ion cells and thermal modelling by COMSOL Multiphysics software C. Ziebert1, A. Ossipova2, M. Rohde1, H.J. Seifert1 1Karlsruhe Institute of Technology (KIT), IAM-AWP 2Ruprecht-Karls University Heidelberg, faculty of physics and astronomy

Institute for Applied Materials – Applied Materials Physics (IAM-AWP)

KIT – University of the State of Baden-Wuerttemberg and National Research Center of the Helmholtz Association

www.kit.edu

Outline

Motivation Introduction Isoperibolic studies Determination of heat dissipation rate and total generated heat Adiabatic studies Combined electrochemical and thermal modelling with COMSOL multiphysics Comparison of experimental and simulation results Summary and outlook

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Dr. C. Ziebert – 225th ECS Meeting 11.-15.05.2014, Orlando

KIT, IAM-AWP

Motivation: Accidents with lithium ion batteries (courtesy Reuters)

(courtesy www.cbsnews.com)

Rechargeable laptop battery – overheating or internal short circuit

(courtesy Auto Bild)

Boeing Dreamliner: – reasons unclear

Chevy Volt: – mechanical impact

Cell Thermodynamics and Safety Studies

- Thermodynamics and phase diagrams strongly influence battery performance - Structural stabilities of active materials need to be taken into account - Battery safety is essential (thermal runaway, abuse, accident) - Thermal management of batteries is important and needs improvement by combination of experimental studies and simulation 3


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Introduction IKEBA Project Integrated Components and Integrated Design of Energy Efficient Battery Systems

Battery Monitoring Automotive uC

Battery Monitoring

5 cooperating partners 4


Battery Management Software

Start time: May 2013 Planned duration: 3 years Budget: 7 Million Euro KIT, IAM-AWP

Short institute presentation

Karlsruhe Institute of Technology (KIT) 2006 - Excellence Initiative of the Federal Republic of Germany and the Federal States 1/10/2009 - Foundation of KIT Merger of University of Karlsruhe (TH) and the Forschungszentrum Karlsruhe GmbH Data 2012 Employees: Students: Professors: Budget: Patents: Spin-offs: Campus South

9.254 23.905 359 785 Mio Euro 72 18 Campus North

Research – Teaching – Innovation 5


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Combined electrochemical and thermal characterization at IAM-AWP Enthalpies, heat capacities, heat generation and heat dissipation - Accelerating Rate Calorimeters (ARC, THT / C3 Analysentechnik) - Isothermal Battery Calorimeter (IBC, THT / C3 Analysentechnik) - Differential Scanning Calorimeters (DSC, NETZSCH) - High Temperature Calvet Drop Solution Calorimeter (Alexsys 1000, Setaram) AlexSys 1000

Accelerating Rate (ARC) Battery Calorimeters 6


Isothermal Battery Calorimeter (IBC)

Digatron MCT Cell Tester (50 A, 6 V, 24 channels KIT, IAM-AWP

Accelerating Rate Calorimeter (ARC) ARC provides both isoperibolic and adiabatic environments Under isoperibolic conditions the environmental temperature is held constant. Under adiabatic conditions the cell can be studied under conditions of negligible heat loss.

Cell Specifications Cell type:

18650

Cathode material: LiMn2O4 (LMO) Nominal capacity: 1400 mAh

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Nominal voltage:

3.7 V

Voltage window:

4.2 V to 2.5 V

Core cell weight:

41 g


KIT, IAM-AWP

Battery Calorimeter

ES-ARC: Ø: 10 cm h: 10 cm

EV-ARC: Ø: 25 cm h: 50 cm

+

EV+ ARC: Ø: 40 cm h: 44 cm

ARC combined with internal or external cycler = Battery Calorimeter

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Isoperibolic studies: cycling parameters

Isoperibolic cycling at 30 °C and 1C charge/discharge rate

Current in A Voltage in V

Discharge parameter: - method: constant current (CC) - Umin = 2.5 V - I = 1.4 A → 1C-rate

2

Temperature in °C

Charge parameter: - method: constant current, constant voltage (CCCV) - Umax = 4.2 V - I = 1.4 A → 1C-rate - Imin = 0.14 A

1 0 -1 -2 4.2 4.0 3.8 3.6 3.4 3.2 3.0 2.8 2.6 2.4 34 32 30 0

200

400

600

800 1000 1200

Time in min 9


KIT, IAM-AWP

Determination of heat dissipation rate and total generated heat Key data for thermal management and safety Conversion of thermal data (temperature, temperature rate) to heat (Joule) and power (Watt) with the aim of understanding of heat release to determine heat removal requirements for thermal management. Energy balance for a cell inside a calorimeter 𝑞𝑞̇ 𝑇𝑇 = 𝑚𝑚 𝑐𝑐𝑝𝑝 Total heat generation rate 𝑞𝑞̇ 𝑇𝑇 Total heat generation

𝑑𝑑𝑑𝑑 − αARC (𝑇𝑇 − 𝑇𝑇𝑒𝑒𝑒𝑒𝑒𝑒 ) 𝑑𝑑𝑑𝑑

Enthalpy accumulation rate 𝑞𝑞̇ 𝑎𝑎𝑐𝑐𝑐𝑐

Heat dissipation rate 𝑞𝑞̇ 𝑑𝑑

𝑡𝑡

𝑞𝑞𝑇𝑇 = 𝑞𝑞𝑑𝑑 +𝑞𝑞𝑎𝑎𝑎𝑎𝑎𝑎 = −αARC ∫0 (𝑇𝑇 − 𝑇𝑇𝑒𝑒𝑒𝑒𝑒𝑒 ) 𝑑𝑑𝑑𝑑 + 𝑚𝑚 𝑐𝑐𝑝𝑝 (𝑇𝑇 𝑡𝑡 − 𝑇𝑇 0 )

S. Hallaj, H. Maleki, J.S. Hong, J.R. Selman, Journal of Power Sources 83, 1-8 (1999)

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Effective specific heat capacity U = 3,3V

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𝑐𝑐𝑝𝑝 = 1.03468 – 0.00718372 ∙ 𝑇𝑇 + 0.00013056 ∙ 𝑇𝑇 2 e.g. at 30 °C cp = 0.94 J/g K Dr. C. Ziebert – 225th ECS Meeting 11.-15.05.2014, Orlando

𝑐𝑐𝑝𝑝 =

𝑞𝑞 𝑚𝑚∆𝑇𝑇

𝑞𝑞̇ 𝑎𝑎𝑎𝑎𝑎𝑎

𝑞𝑞 = � 𝑈𝑈 ∙ 𝐼𝐼𝐼𝐼𝐼𝐼

𝑑𝑑𝑑𝑑 = 𝑚𝑚 ∙ 𝒄𝒄𝒑𝒑 𝑑𝑑𝑑𝑑

KIT, IAM-AWP

Measurement of calorimeter constant Energy balance for lumped heat transfer system under natural convective heating conditions and 𝐵𝐵𝑖𝑖 ≪ 0.1

60

Solution:

50

2

40

1 Dummy Cell: cylinder of AlMgSi0.5 EN AW-6060 F22 with same dimensions as 18650 cell

30 20

0

100 200 300 400 500 600 Time in min

cp = 0.9 J/g K

m = 46.02 g

at t = 0

ln(𝑇𝑇 − 𝑇𝑇 𝑒𝑒𝑒𝑒𝑒𝑒 )=

3

ln(Tenv-T)

Temperature in °C

Initial condition: 𝑇𝑇 = 𝑇𝑇 𝑒𝑒𝑒𝑒𝑒𝑒

Tenv T

70

𝑑𝑑𝑑𝑑

m 𝑐𝑐𝑝𝑝 𝑑𝑑𝑑𝑑 = αARC(𝑇𝑇 − 𝑇𝑇𝑒𝑒𝑒𝑒𝑒𝑒 )

αARC

𝑚𝑚 𝑐𝑐𝑝𝑝

𝑡𝑡

0 -1 -2 -3

0

A = 3.674 ⋅10 -3 m2

1000

2000 Time in s

3000

4000

Calorimeter constant αARC = (0.04 ± 0.001) W/K

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KIT, IAM-AWP

Heat dissipation and total generated heat

Heat dissipation rate in mW

Tenv = 30°C, 1 C charge/1 C discharge 200 150 100 50 0

0

200

Results of integration over one discharge cycle:

cp = 0.94 J/g K

𝑚𝑚 = 43 g

𝑇𝑇(t) = 39.3 °C

𝑇𝑇(0) = 30.13 °C

Total heat generated during 1C discharge at 30 °C: 13


400 600 800 1000 1200 Time in min

𝑞𝑞𝑑𝑑 = -322.3 J

𝑞𝑞𝑎𝑎𝑐𝑐𝑐𝑐 = 370.7 J 𝑞𝑞𝑇𝑇 = 48.4 J

KIT, IAM-AWP

C-rate dependence of heat dissipation rate

4.2 0.7A (0.5C) 1.4A (1C) 2.8A (2C) 4.2A (3C)

50 °C

4.0 3.6 3.4 3.2 3.0 2.6

0.4

0.6

0.8

1.0

1.2

1.4

Discharge in Ah

C-Rate dependence of capacity vs. voltage curve during isoperibolic cycling at 50 °C

150

0.25C

100 50 0

0

200

0.5C

{

0.2

1C

200

{

2.4 0.0

250

{

2.8

Heat dissipation rate in mW

Voltage in V

3.8

400 600 Time in min

800

1000

C-rate dependence of heat dissipation rate during isoperibolic cycling at 30 °C

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KIT, IAM-AWP

Adiabatic studies: working principle

Why ADI ABATI C? With conditions of NO HEAT LOSS or gain …data showing heat release ie exotherm reaction.... is given as ‘WORST CASE’ DATA Therefore the ARC gives a SIMULATION of what may happen WORST CASE data may then be extrapolated to any LARGER scale As there is no heat loss, the data can be treated to simulate what will happen for any heat loss scenario

Sample Calorimeter

Source: Thermal Hazard Technology (THT)

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Adiabatic studies: cycling parameters

Adiabatic cycling at 30 °C and 1C charge/discharge rate

Current in A Voltage in V

Discharge parameter: - method: constant current (CC) - Umin = 2.5 V - I = 1.4 A → 1C-rate

2

Temperature in °C

Charge parameter: - method: constant current, constant voltage (CCCV) - Umax = 4.2 V - I = 1.4 A → 1C-rate - Imin = 0.14 A

1 0 -1 -2 4.2 4.0 3.8 3.6 3.4 3.2 3.0 2.8 2.6 2.4 80 70 60 50 40 30 0

200

400

600

Time in min

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KIT, IAM-AWP

Combined electrochemical and thermal modelling with COMSOL multiphysics 1d – electrochemical

Diffusion of Li-ions in the electrodes

2d – thermal (axial-symmetric)

U(t), I(t), SOC

Diffusion of Li-ions in the electrolyte Ohmic Losses

Thermal conductivity Heat capacity

T(t), Q(t)

Heat transport – Temperature distribution

L. Cai and R. E. White, Journal of Power Sources 196 (2011) 5985–5989 17


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Governing equations 1d – electrochemical model Material balance for Li-ions in the electrodes

2d – thermal model Thermal conductivity (radial)

(Fick‘s second law)

Material balance for Li-ions in the electrolyte

Ohm‘s law for Li-ions

Heat capacity

Energy balance

r radius, c concentration, t + transfer coefficient, ε porosity, a area, J current density, D diffusion constant, φ potential, F Faraday-constant, σ electric conductivity, Li thickness of ithlayer of spirally wounded cell, λ thermal conductivity 0

L. Cai and R. E. White, Journal of Power Sources 196 (2011) 5985–5989 18


KIT, IAM-AWP

Comparison of experimental and simulation results Tenv = 40 °C, 1 C Charge/1 C Discharge Current density in A/m2

1 0 -1 4.2 4.0 3.8 3.6 3.4 3.2 3.0 2.8 2.6 2.4

Isoperibolic

Voltage in V

Voltage in V

Current in A

Experiment

∆T in K

∆T in K

2

20 10 0 -10 -20 4.2 4.0 3.8 3.6 3.4 3.2 3.0

2 0

0

200

400

600

800

1000

Time in min 19

Simulation

4

4

0

(1 C ~ 20 A/m2 )


0

200

400

600

800

1000

Time in min KIT, IAM-AWP

Comparison of experimental and simulation results Tst = 25 °C, 1 C Charge/1 C Discharge Experiment

Simulation 20 Current in A

1 0 -1

40

Voltage in V

Adiabatic

30 20

0 -10

4.2 4.0 3.8 3.6 3.4 3.2 3.0 50 40 30 20 10

10 0

100 200 300 400 500 600 700 Time in min

20

10

-20

-2 4.2 4.0 3.8 3.6 3.4 3.2 3.0 2.8 2.6 2.4 50

∆T in K

∆T in K

Voltage in V

Current in A

2

0

(1 C ~ 20 A/m2 )


0

0

100 200 300 400 500 600 700 Time in min KIT, IAM-AWP

C-rate dependence of maximum temperature increase during discharge isoperibolic

∆T in K

Heat dissipation qd [mW]

Simulation

Experiment 550 500 450 400 350 300 250 200 150 100 50 0

3C 2C

1C 0.5C

0

200

400

∆Tmax in K

Time in s 45 40 35 30 25 20 15 10 5 0

Experiment Simulation

0 21

600 800 1000 1200 Time [min]

1

2

3 C-Rate


4

5 KIT, IAM-AWP

Summary and Outlook Combination of electrochemical-calorimetric studies on cylindrical lithium ion cells and thermal modelling by COMSOL Multiphysics software

Results:  Significant temperature rise even for low charge/discharge rates  Analysis of heat generation and dissipation during electrochemical cycling  Good agreement between experimental and simulation results Outlook:  Comparison of different cell chemistries  Assignment of heat effects to electrochemical processes and components

Improvement of Thermal Management and Safety 22


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Acknowledgement

Thank you for your attention! This R&D project is partially funded by the Federal Ministry for Education and Research (BMBF) within the framework „IKT 2020 Research for Innovations“ under the grant 16N12515 and is supervised by the Project Management Agency VDI│VDE│IT. supervised by

We gratefully acknowledge the financial support by the Helmholtz program STN and the funding in the Helmholtz Portfolio Project “Electrochemical Storage in the System”

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