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ECEN5017 Guest Lecture

Overview of NREL Battery Lifetime Overview of NREL Battery Lifetime Models & Health Management R&D for Models & Health Management R&D for ggElectric Drive VehiclesElectric Drive Vehicles

Kandler [email protected]

Ahmad A PesaranAhmad A. [email protected]

Center for Transportation Technologies and Systems National Renewable Energy Laboratory

NREL is a national laboratory of the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, operated by the Alliance for Sustainable Energy, LLC.

National Renewable Energy Laboratory

September 2012

NREL EDV Energy Storage ProjectsSupporting DOE and industry achieve energy storage targets for electrified vehicles pp g y gy g g

Battery Material Research and Development Battery Material Research and Development

Component Testing and Characterization (Including Safety)Component Testing and Characterization (Including Safety)

NRELNRELNRELNREL

( g y)( g y)

Multi‐physics Battery Modeling(including Safety)Multi‐physics Battery Modeling(including Safety)Energy Storage TaskEnergy Storage TaskEnergy Storage TaskEnergy Storage Task (including Safety)(including Safety)

Battery Life Prediction and Trade‐offBattery Life Prediction and Trade‐offBattery Life Prediction and Trade offBattery Life Prediction and Trade off

Batter S stem E al ationBatter S stem E al ation

NATIONAL RENEWABLE ENERGY LABORATORY 2

Battery System EvaluationBattery System Evaluation

Physics of LiPhysics of LiIon Battery Systems in Different Length ScalesIon Battery Systems in Different Length Scales

Charge balance and transportElectrical network in composite electrodes

Electronic potential &current distributionHeat generation and

Electrode Scale Cell Scale

Li diffusion in solid phaseInterface physicsParticle deformation & fatigueStructural stability

pLi transport in electrolyte phase

gtransferElectrolyte wettingPressure distribution

Particle Scale Module ScaleThermal/electricalintercell configurationThermal managementSafety control

Atomic Scale System ScaleSystem operating conditionsEnvironmental conditionsControl strategy

Thermodynamic propertiesLattice stabilityMateriallevel kinetic barrierTransport properties

DOE/NREL C t Aid d E i i f B tt i

NATIONAL RENEWABLE ENERGY LABORATORY

DOE/NREL Computer-Aided Engineering of Batteries (CAEBAT) Program Integrating Battery R&D Models

Typical Structure of Li-ion BatteriesD i i Th d i

V

Designing ThermodynamicsDesigning Kinetics

V

Li+


Why Lithium Ion?


Figures: Cyril Truchot, MS Thesis

What determines working voltage?Thermodynamic potential = Cathode potential – Anode potential

Anode:G hit Li C6

y p p p

Graphite, LixC6Lithium metalSiliconSilicon

Cathode:Choice of transition metalsChoice of crystalChoice of crystal structures

Figures: Cyril Truchot


Cyril Truchot, MS Thesis

Cathode selection

Source:


Source: Cyril Truchot, MS Thesis

Battery Aging / Performance Fade

System-level observations– Capacity loss

I d i / f d– Impedance rise/power fade– Potential change

Calendar life goal: 10 to 15 years Effects during storage– Self discharge, impedance rise

Cycle life goal: 3,000 to 5,000 deep cycles Effects during use– Mechanical degradation, Li metal plating

Where do changes occur?1. Electrode/electrolyte interface, affecting both electrode & electrolyte2. Active materials3. Composite electrode


Anode Aging

1. Solid/Electrolyte Interphase (SEI) Layer

Passive protective layer, product of organic electrolyte decompositionSEI formation = f(as, formation conditions)

Mostly formed during first cycle of battery but continues to grow at slow rateMostly formed during first cycle of battery, but continues to grow at slow rateMay penetrate into electrode & separator pores, inhibiting Li transport in the electrolyteHigh temperature effectsHigh temperature effects

– Exothermic side reactions cause self heating– Film breaks down and dissolves, later precipitates

More stable inorganic SEI formed blocking Li insertion– More-stable inorganic SEI formed, blocking Li insertionLow temperature effects (during charging)

– Slow diffusion causes Li saturation at LixC6 surface– Slow kinetics causes increased overpotential


– Slow kinetics causes increased overpotential

Anode Aging

2. Changes of Active Material

Volume changes during insertion/de-insertion (~10%)Solvent intercalation, electrolyte reduction, gas evolution , y , ginside LixC6

Stress Cracks

3. Changes of Composite Electrode

SEI & volume changes cause: – contact loss between LixC6, conductive binder, and current

collector– reduced electrode porosity


Anode Aging


Image: Vetter et al., “Ageing mechanisms in lithium‐ion batteries,” J. Power Sources, 147 (2005) 269‐281

Cathode Aging

Li(Ni,Co,Al)O2 MaterialsLiC O th d t i lLiCoO2 common cathode materialLiNiO2 structure unstable unless

doped with Co or AlLi(Ni,Co,Al)O2 volume changes ( , , ) 2 g

are small good cycle lifeDischarged state stable at high

temperaturesLiCoO2 charged beyond 4 2 voltsLiCoO2 charged beyond 4.2 volts,

Co dissolves and migrates to anode

Surface effectsSEI film formation accelerated when charged > 4 2 V high temperatures

Image: Vetter et al., “Ageing mechanisms in lithium‐ion batteries,” J. Power Sources, 147 (2005) 269‐281

– SEI film formation accelerated when charged > 4.2 V, high temperatures– Electrolyte oxidation and LiPF6 decomposition– Li(Ni,Co,Al)O2 source O2 rock-salt structure with low electronic conductivity & Li

diffusion– Gas evolution


Gas evolution

Cathode Aging

Source: Vetter et al., “Ageing mechanisms in lithium‐ion batteries,” J. Power Sources 147 (2005) 269‐281Power Sources, 147 (2005) 269 281

Source: Wohlfahrt‐Mehrens et al., “Aging mechanisms of lithium cathode materials,” J. Power Sources, 127 (2004) 58‐64


Summary of AgingA i i fl d bAging influenced by:Both high and low SOCHigh temperaturesHigh temperaturesLow temperatures during chargingSurface chemistry (anode and cathode)Su ace c e st y (a ode a d cat ode)Phase transitions/structural changes (cathode)

Both calendar life (years) and cycle life (driving and charging patterns) are important


How Can We Predict Battery Life?

Accelerated storage testsRelatively well understoodMechanism: SEI growth, Li lossModel:

1.25

1.3

1.35

stan

ce

304047.555

Calendar Life Study at Various T (°C)

Model:– t½ time dependency– Arrhenius T dependency

Accelerated cycling testsP l d t d 1 05

1.1

1.15

1.2

Rel

ativ

e R

esis

Poorly understoodMechanism: Mechanical stress & fracture

(may be coupled with SEI fracture + regrowth)Model:

0 0.2 0.4 0.61

1.05

Time (years)

R

Source: V. Battaglia (LBNL), 2008

Cycle Life Study at Various Cycles/Day & ΔDoD

– Typical t or N dependency– Often correlated log(# cycles) with ΔDOD

ycles)

y y y / y

Real‐world cycling & storage

♦ Poorly understood

d l d k b blLife (#

cy


♦ NREL model extends previous work by enabling extrapolation beyond tested conditions

15

ΔDoDSource: J.C. Hall (Boeing), 2006

NREL’s Battery Life-Prognostic ModelBatter aging datasets fit ith empirical et ph sicall j stifiable form las

Calendar fade• SEI growth (partially

Cycling fade• active material structure

Battery aging datasets fit with empirical, yet physically justifiable formulas

g (p ysuppressed by cycling)

• Loss of cyclable lithium • a1, d1 = f(∆DOD,C‐rate,T,V)

degradation and mechanical fracture

• a2, e1 = f(∆DOD,C‐rate,T,V)

RelativeResistance R = a1 t1/2 + a2 N

RelativeCapacity Q = min ( QLi , Qactive )

Qactive = e0 + e1 NQactive = e0 + e1 NQLi = d0 + d1 t1/2QLi = d0 + d1 t1/2


Enables life predictions for untested real-world scenarios

Fitting of NCA/Graphite Baseline Life Model to Lab Data

1. Resistance growth during storage♦ Broussely (Saft), 2007:

• T = 20°C 40°C 60°C • 30 different tests• T = 20 C, 40 C, 60 C• SOC = 50%, 100%

2. Resistance growth during cycling♦ Hall (Boeing) 2005-2006:

• >$1M in test equipment

• 1‐4 years duration♦ Hall (Boeing), 2005-2006:• DoD = 20%, 40%, 60%, 80%• End-of-charge voltage = 3.9, 4.0, 4.1 V• Cycles/day = 1, 4

1 4 years duration

Expensive!!y y

3. Capacity fade during storage♦ Smart (NASA-JPL), 2009

• T = 0°C, 10°C, 23°C, 40°C, 55°C, , , ,♦ Broussely (Saft), 2001

• V = 3.6V, 4.1V

4. Capacity fade during cycling


p y g y g♦ Hall/Boeing, 2005-2006: (same as # 2 above)

Acceleration Factors

Arrhenius Eqn. • Describe a1, a2, b1, c1as f(T,Voc,ΔDoD)

• Combined effects

ref

aT TtTR

E 1)(

1exp

Tafel Eqn. assumed multiplicative

refoc VtVF )(

Wöhler Eqn.

ref

focV TtTR )(

)(exp

Wöhler Eqn.

ref

DoD DoDDoD


Acceleration FactorsResistance growth during storage

Arrhenius Eqn.

Data: Broussely, 2007

ref

aT TtTR

E 1)(

1exp

Tafel Eqn.

refoc VtVF )(

Wöhler Eqn.

ref

focV TtTR )(

)(exp

Wöhler Eqn.

ref

DoD DoDDoD


Acceleration FactorsResistance growth during cycling

Arrhenius Eqn.

Data: Hall, 2006

ref

aT TtTR

E 1)(

1exp

Tafel Eqn.

refoc VtVF )(

Wöhler Eqn.

ref

focV TtTR )(

)(exp

Wöhler Eqn.

ref

DoD DoDDoD


Acceleration FactorsCapacity fade during cycling

Arrhenius Eqn.

Data: Hall, 2006

ref

aT TtTR

E 1)(

1exp

Tafel Eqn.

refoc VtVF )(

Wöhler Eqn.

ref

focV TtTR )(

)(exp

Wöhler Eqn.

ref

DoD DoDDoD


Model Comparison with Laboratory Data

PHEV

HEVHEV

NATIONAL RENEWABLE ENERGY LABORATORYASTR 2010 Oct 6 – 8, Denver. C l d

Factors in Vehicle Battery Aging

Cell Design Environment Duty Cycle

• Chemical

• Electrochemical

• Electrical

• Thermal

o geography

o thermal management

• System design

o vehicle

o excess power &

• Manuf. uniformity

o defects

gsystem ($)

o heat generation

• Humidity

penergy @ BOL ($)

o system controls

• DriverHumidity

• Vibration

Driver

o annual mileage

o trips/day

io aggressiveness

o charging behavior– charges/day


– fast charge

Factors in Vehicle Battery Aging

Cell Design Environment Duty Cycle

• Chemical

• Electrochemical

• Electrical

• Thermal

o geography

o thermal management

• System design

o vehicle

o excess power &

• Manuf. uniformity

o defects

gsystem ($)

o heat generation

• Humidity

penergy @ BOL ($)

o system controls

• DriverHumidity

• Vibration

Driver

o annual mileage

o trips/day

io aggressiveness

o charging behavior– charges/day


– fast charge

(Not considered)

Benefit of Life-Predictive ModelingModelingSource: Mark Isaacson, Lockheed Martin (satellite application)


Simulation ApproachV hi l d i lVehicle drive cycles782 speed vs. time tracesCharging assumptions

Battery power profile

Vehicle Model

y p p• SOC(t), Heat gen(t), etc.

e.g., Cyc_4378_1Model


PHEV10 Opp. Chg

li

Simulation ApproachV hi l d i l Climate

• U.S. national distribution

Vehicle drive cycles782 speed vs. time tracesCharging assumptions


Vehicle Model B tt t t ti ti

y p p• SOC(t), Heat gen(t), etc.• Thermal management assumptions

Battery Thermal

Model Battery stress statistics• T(t), Voc(t), ∆DODi, Ni, …

Model


Simulation ApproachliV hi l d i l Climate

• U.S. national distribution

Vehicle drive cycles782 speed vs. time tracesCharging assumptions


Vehicle Model B tt t t ti ti

y p p• SOC(t), Heat gen(t), etc.• Thermal management assumptions

Battery Thermal

Model Battery stress statistics• T(t), Voc(t), ∆DODi, Ni, …

Battery LifeModel

Model Life

Model

Minneapolis

pacity

NCA/Graphite


15 C

20 C

25 C30 C

10 CHouston

Phoenix

Years

Cap

Vehicle & Battery Assumptions

PHEV10 PHEV40All-electric range, km 16.7 67Total vehicle mass, kg 1714 1830Electric motor power kW 40 43Vehicle PHEV10:Electric motor power, kW 40 43IC engine power, kW 77 80

Useable power, kW 44 48U bl kWh 2 67 11 48

PHEV10: 50% ∆DOD at BOL

80% SOCmax

Useable energy, kWh 2.67 11.48Maximum SOC 80% 90%Minimum SOC at BOL 30% 30%Minimum SOC at EOL 13% 10%E t BOL 100% 67%

Battery Electrical1

PHEV40: 60% ∆DOD at BOL

90% SOCmaxExcess energy at BOL 100% 67%Excess power at BOL, 10% SOC 43% 43%

Heat transfer area - cells-to-coolant, m2 1 32

Battery Heat transfer area - pack-to-ambient, m2 1.2 2.9Heat transfer coeff. - pack-to-ambient, W/m2K 2 2

1. EOL condition = 75% remaining capacity

Thermal2,3


O co d o 5% e a g capac y2. Heat generation rate at 2/3 of EOL resistance growth

Real-World Life Variability with Duty Cycle

Matrix of analytic scenarios

Duty Cycles• 782 Real-World drive

cycles from Texas Dept

Vehicles• PHEV10 sedan cycles from Texas Dept.

of Transportation• PHEV40 sedan

Thermal Management• Fixed 28oC battery temperature*• Limited cooling (forced ambient air)

Charging Profiles**

• Nightly charge (baseline)• Opportunity chargeLimited cooling (forced ambient air)

• Aggressive cooling (20oC chilled liquid)• Opportunity charge


** Level I charging rates.* Worst‐case hot climate, Phoenix Arizona ~28oC

Expected Life for various drive-cycle aging scenarios at constant temperature – PHEV10p

Life expectancy across 782 driving cycles in a hot climate is 7 8 to

Nightly ChargePhoenix ClimateConstant 28oC

hot climate is 7.8 to 13.2 years

Reminder of key yassumptions:

– NCA chemistry– End-of-life condition:End of life condition:

75% remaining capacity

– 80% SOCmaxmax– 30% SOCmin @ BOL

Opportunities for


Opportunities for V2G, 2nd use?

Expected Life – PHEV10 vs. PHEV40Nightly ChargeNightly ChargePhoenix ClimateConstant 28oC

86% f d i i86% of driving cycles > 10 mi/day

34% f d i i


34% of driving cycles > 40 mi/day

Impact of Opportunity Charging (Level 1)Phoenix Climate

PHEV10 PHEV40

Phoenix ClimateAggressive Cooling

0

PHEV10: Frequent charging can •PHEV40: Frequent charging can


PHEV10: Frequent charging can reduce average life by 1 year

•PHEV40: Frequent charging can extend average life by ½ year

Impact of Battery Thermal Environment

Geographic Impact on LifeGeographic Impact on Life Thermal Management Impact on LifeThermal Management Impact on Life

Illustration by Josh Bauer, NREL

Minneapolis Air cooling

Liquid cooling, chilled fluid

15° C

10° C

p

Houston

Phoenix

Li i hit / i k l t lif

No cooling

Air cooling

Air cooling, low resistance cell

20° C25°

C30° C

Li-ion graphite/nickelate life:PHEV20, 1 cycle/day 54% ∆DoD

Phoenix, AZ ambient conditions33 miles/day driving, 2 trips/day


Battery R&D

•Energy storage is already ubiquitous in electronics; many more vehicle and grid applications are in the pipeline

• Cost life and safety all need improvement for greater marketCost, life, and safety all need improvement for greater market acceptance

•Multi-disciplinary, multi-physics nature of batteries:• Slow development process• Slow development process• Moore’s Law does not apply• Easier to find a thesis topic!

•Student opportunities at NREL• Part-time test engineer; send resumes to [email protected]• Organize a thesis topic together with NREL

•More info: http://www.nrel.gov/vehiclesandfuels/energystorage/publications.html


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