Development of Cell/Pack Level Models for Automotive Li-Ion Batteries with Experimental

Validation Christian Shaffer

EC Power

http://www.ecpowergroup.com

5/15/12 Project ID # ES120

This presentation does not contain any proprietary, confidential, or otherwise restricted information

Overview

2

• Start date: 5/1/2011 • End date: 4/30/2014 • 33% complete

• Barriers addressed – LiB Performance and Lifetime – LiB Efficiency – LiB Safety – Computer tools for design exploration

• Total project funding: $3.0M – $1.5M (DOE) – $1.5M (cost share)

• Funding received in FY11 • $193.6K

Timeline

Budget

Barriers

• Ford • Johnson Controls • Penn State • NREL • ORNL

Partners

Funding provided by Dave Howell of the DOE Vehicle Technologies Program . The activity is managed by Brian Cunningham of Vehicle Technologies. Subcontracted by NREL, Shriram Santhanagopalan Technical Monitor

• Develop an electrochemical/thermal (ECT) coupled model for large-format automotive Li-ion batteries (cells and packs)

• Create a fast & robust tool for realistic geometries (wound or stacked electrode designs)

• Develop a comprehensive materials database • Integrate ECT3D software with CAEBAT Open Arch. Software • Aide OEMs and cell/pack developers in accelerating the adoption

of large-format Li-ion technology required for EV & PHEV • Develop a virtual environment to reduce the time required for

design, build and test of Li-ion batteries – Performance – Safety – Life – Efficiency

• Support DOE CAEBAT activity

Project Objectives - Relevance

3

Project Milestones & Activities

4

2011/2012 Milestones Completed M1: Report on initial materials database

M2: Report/manual for baseline ECT3D software delivered to NREL

M3: Baseline ECT3D code delivered to NREL

M4: Updated data for materials database

M5: Report for updated materials database information

M6: Report for updated materials database information

Meetings with ORNL & other CAEBAT members to give input for the Open Architecture Standard

Battery Safety 2011 – Las Vegas (11/2011)

Presentation to USDrive (12/13/11)

2012 Milestones in Progress M7: Initial model validation

M8: Report of safety modeling

M9: Updated version of ECT3D to NREL w/pack simulation capabilities

M10: Report for updated materials database information

M11: ECT3D user interfaces complete

M12: Report of detailed model validation for ECT3D

Approach – Supporting CAEBAT Activity

5

Task 1: Materials Characterization

(PSU)

EC Power software: ECT3D

Task 2: Physico-chemical Models

(ECP)

Task 3: Advanced Algorithms

(ECP)

Task 4: Experimental Validation

(PSU, ECP)

Performance Cycle Life Safety

2.422.222.021.831.631.431.231.030.840.640.44

He

ig

ht

(cm

)

0

2

4

6

8

10

Length (cm)0 50 100 150 200 250 300 350 400 450

Discharge Capacity (Ah)

Cel

lVol

tage

(V)

0 0.2 0.4 0.6 0.8 1 1.2 1.43

3.2

3.4

3.6

3.8

4

4.2

4.4

01000200030005000

Data, Cycled Number

1C discharge

Solid Line: Model Simulation

Ford, JCI Feedback Feedback

Approach – Materials Database

6

Electrolyte Distribution in a Li-ion Cell Under Discharge

1.2M

4 M

0.1M 0

Negative Electrode

Positive Electrode

Ele

ctro

lyte

Con

cent

ratio

n

1M

Nominal conditions for material and battery developers

of interest for battery modeling and hence this study

Separator

4M Cell 1M Cell 0.1M Cell

…… ……

Modeling parameters needed at low-T, high-T, wide range of chemical compositions and similar conditions of interest for automotive Li-ion batteries and packs.

Approach – ECT Model Development

7

Electrochemical Processes - electrochemical reactions - solid state diffusion - ion transport through electrolyte - charge transfer

Thermal Processes

- conservation of thermal energy

Heat generation rate

Temperature-dependent physico-chemical properties

−Φ=Φ Φ

TTRE

ref

actref

11exp ,

Model predictions - potential and current curves - temperature history/distribution - active material utilization - current distribution

( )qT

tTcp +∇⋅∇=

∂∂

λρ

( )

[ ]∑

∑><⋅∇><−

Π+=

k

kkk

jjjnjsjiaq

φ

η

i

• Understanding thermal phenomena & thermal control

has huge impact on – Battery safety – Cycle life – Battery management system – Cost

• Electrochemical-thermal (ECT) coupling required for

– Internal short circuits – Thermal runaway – High power, low-T operation – Heating from subzero environment

Approach – Computational Challenges

8

• Develop numerical algorithms to handle: 1) large electrode size (0.1-1 m2) 2) multi-layer wound and stacked geometry 3) ECT couplings, while still maintaining near real-time calculations

coin cells 18650 large format batteries

nonuniform current distribution

~100x more

challenging

This Proposal

ECEC 1999

ECEC 2002

NREL 2009

coin cells 18650 large format batteries

nonuniform current distributionnonuniform current distribution

~100x more

challenging

This Proposal

ECEC 1999

ECEC 2002

NREL 2009ECEC 1999

ECEC 2002

NREL 2009

==Area SurfaceOuter Battery

Area ElectrodeActual (CF) Factor sCompactnes1 for coin cells and flat cells 22.5 or 32.5 for 18650 or 26650 cells 60-100 for pouch cells

• Development of extensive materials database • Efficient, electrochemical-thermal coupled large-format

cell simulation – Performance evaluation and analysis – Analysis of active materials utilization – Virtual design tool: lower cell cost

• Preliminary validation • Preliminary safety simulations

– Full (fast) nail penetration – Partial (slow) nail penetration – Shorting by metal particle

Technical Accomplishments

9

Capacity (mAh)

Volta

ge(V

)

Tem

pera

ture

Incr

ease

(°C

)

0 500 1000 1500 2000 25002

2.5

3

3.5

4

0

20

40

60

80

0.2C(0.44A)1C(2.2A)

3C(6.6A)

4.6C(10A)

Discharge at 25°CModelExperimental data

• Material, thermodynamic and kinetic properties for common Li-ion battery materials have been compiled over a wide range of temperature, chemical compositions and SOC. – Anode AM: graphite, MCMB, LTO – Cathode AM: MNC, LMO, LFP, NCA, LCO – Electrolytes: LiPF6 in various solvents

Accomplishments – Material Database

10

SOC / %

0102030405060708090100

Li d

iffus

ion

coef

ficie

nt /

cm2 s-1

10-12

10-11

10-10

10-9

10-8

CathodeAnode

• Initial validation efforts at low-T and high C-rate conditions

• Detailed validation efforts currently ongoing

Accomplishments - Validation

11

Capacity (mAh)

Volta

ge(V

)

Tem

pera

ture

Incr

ease

(°C

)

0 500 1000 1500 2000 25002

2.5

3

3.5

4

0

20

40

601C (2.2A) discharge

ModelExperimental data

45°C

25°C0°C

-10°C

-20°C

Capacity (mAh)

Volta

ge(V

)

Tem

pera

ture

Incr

ease

(°C

)

0 500 1000 1500 2000 25002

2.5

3

3.5

4

0

20

40

60

80

100Discharge at -10°C

ModelExperimental data

0.2C(0.44A)

1C(2.2A)2C(4.4A)

3C(6.6A)

Accomplishments - Performance

12

Height(m

)

0

0.02

0.04

0.06

0.08

0.1

Length (m)0 0.2 0.4 0.6 0.8 1

0.85000.84710.84430.84140.83860.83570.83290.8300

Height(m

)

0

0.02

0.04

0.06

0.08

0.1

Length (m)0 0.2 0.4 0.6 0.8 1

0.71000.70290.69570.68860.68140.67430.66710.6600

SOC in Unrolled Electrode (a) 100s

(b) 200s

3Ah prismatic rolled electrode design – 6C discharge Temperature (K)

(a) 100s

(b) 200s H

eight(m)

0

0.02

0.04

0.06

0.08

0.1

Length (m)0 0.2 0.4 0.6 0.8 1

111.0000109.4000107.8000106.2000104.6000103.0000101.4000

99.800098.200096.600095.0000

Height(m

)

0

0.02

0.04

0.06

0.08

0.1

Length (m)0 0.2 0.4 0.6 0.8 1

111.0000109.4000107.8000106.2000104.6000103.0000101.4000

99.800098.200096.600095.0000

Current Density in Unrolled Electrode (A/m2) (a) 100s

(b) 200s

Tab Tab

Performance evaluation and local analysis of active materials utilization over time

Accomplishments - Performance

13

5-Jelly Roll Cell Design (15 Ah)

t=100s t=800s

@ t = 100s Current density profile determined by material and geometric effects @ t = 3500s Current density profile determined by material and geometric effects, local SOC non-uniformity, and thermal effects

Outside of each rollInside of each rollElectrode length (cm)

Cur

rent

dens

ity(m

A/c

m2 )

100 200 300 4001.2

1.4

1.6

1.8

2

3500 s

cell #1

100 s

cell #5cell #2 cell #3 cell #4

Tab Tab Tab Tab Tab Tab Tab Tab Tab Tab

Current density along the electrode length

Convective Top & Sides

Adiabatic Bottom

Cell #1Cell #2Cell #3Cell #4Cell #5

Tamb = 300K 1C Discharge

Design optimization for active materials utilization

Accomplishments - Safety

14

Partial nail penetration (Slow)

Only 3-D electrochemical-thermal coupled (ECT) model can completely describe the problem

Full nail penetration (Fast)

26 unit layers stacked

Case Study (10Ah prismatic cell)

Accomplishments - Safety

15

0.5s 10s 100s

Diameter = 0.5 mm

Tmax=180oC Tavg= 34oC Tmax-Tavg=146oC

Tmax=58oC Tavg= 53oC Tmax-Tavg=5oC

Tmax=116oC Tavg= 113oC Tmax-Tavg=3oC

Diameter = 8 mm

0.5s 10s 100s

Tmax=36oC Tavg= 34oC Tmax-Tavg=2oC

Tmax=52.8oC Tavg= 52.3oC Tmax-Tavg=0.5oC

Tmax=114oC Tavg= 112oC Tmax-Tavg=2oC

Full Penetration

Rapid temperature rise caused by electrochemical effects (e.g. nail penetration) can only be predicted with electrochemical thermal (ECT) coupling

Accomplishments - Safety

16

Full Penetration

0 1 2 3 4 5 6 7 8 960

80

100

120

140

160

180

200

220

Max

imum

tem

pera

ture

in 1

50s

(o C)

Nail diameter (mm)

Separator shutdowneffective

Separator shutdownineffective

Global heatingLocal heating

100

0 100 200 300 400 5001E-3

0.01

0.1

16

Separator shutdown

Voltage

Volta

ge (V

)

Time (sec)

D = 2mm

Anode Separator Cathode

D = 2mm

Li+ depletion

Anode Cathode

Simultaneous thermal and electrochemical results during safety-related events

Accomplishments - Safety

17

0.1s 0.5 s 1.0 s 5.0 s

Temperature (oC) for PD = 0.2

Partial Penetration

. . .

Cu foil

Al foil Penetrated layers

Penetrated layers

Unpenetrated layers

Unpenetrated layers

. . .

Solid Potential for PD = 0.2

0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0100

150

200

250

300

350

400

450

Max

imum

tem

pera

ture

(o C)

Nail penetration depth (normalized by cell thickness)

(PD)

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0 20 40 60 80 1000.0

0.5

1.0

1.5

2.0

2.5

3.0

Volta

ge (V

)

Time (sec)0 20 40 60 80 100

-2000

200400600800

10001200140016001800

Tem

pera

ture

(o C)Time (sec)

Average Temp Maximum Temp

0 20 40 60 80 1000

2

4

6

8

10

12

14

Curr

ent (

C-ra

te)

Time (sec)

Tab heating is the key mechanism

Accomplishments – Safety Shorting by Metal Particle

• 10 Ah, 26 layer stacked cell • Rshort = 10mΩ • Short in center of layer • Short in center layer of stack

C-rate in shorted layer

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0.1s

0.1s

5s

5s

40s

40s

80s

80s

Surface Temperature

Temperature in stack center

Accomplishments – Safety Shorting by Metal Particle

Heating greatest in tabs and in metal particle

Collaboration w/Other Institutions

20

Project Lead – Software development and sales, project administration.

Funding Agency

CAEBAT Program Administrator

Industrial Partner – testing, validation, and feedback

Industrial Partner – testing, validation, and feedback

Academic Partner – materials testing and

detailed model validation

Open Architecture Software

• More safety simulation of interest to Ford & JCI • Pack modeling with electrochemical-thermal coupling • Further and extensive cell and pack validation • Refined user interfaces • Life/degradation modeling; optimization of battery usage • Additional content for materials database • Blended electrode models (anode & cathode) • Quarterly review meetings with all team members

Future Work

21 Capacity (mAh)

Volta

ge(V

)

0 500 1000 1500 20000

0.5

1

1.5

2

2.5

3

3.5

4

OCV

1C

3C5C

Graphite-LTO : NCM-LMO-LFP

Thickness(µm): A(75)-S(20)-C(79)Porosity: A(0.27)-S(0.46)-C(0.27)

(1:1) (1:1:1)

Anode AM Cathode AM

Input and design properties GUI

• Good progress in 2011 – Cell level software development – Performance modeling on cell level – Preliminary safety modeling of cells – Materials database

• Commercial partners (Ford, JCI) – Began testing ECT3D in December, 2011 – Will give expanded feedback during 2012 – ECT3D is a tool to help

• Reduce cost, “… by accelerating design processes and system optimization using virtual test bench (software).”

• Improve safety, “… by understanding the benefits and tradeoffs of various safety technologies.”

• Improved thermal performances, “… leading to either cost savings or better life.”

• Meeting CAEBAT/DOE goals – Helping to accelerate the adoption of automotive Li-ion battery

cells & packs – Enabling technology for EV, PHEV

Summary

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