traction batteries: automotive requirements, current...

Traction batteries: automotive Traction batteries: automotive requirements, current status, and requirements, current status, and challenges aheadchallenges ahead4th Symposium on Energy Storage: Beyond Lithium Ion4th Symposium on Energy Storage: Beyond Lithium IonPacific Northwest National Laboratory, Richland, WashingtonPacific Northwest National Laboratory, Richland, Washington

Mark Verbrugge, Director, Chemical Sciences and Materials Systems LabGeneral Motors Research & Development

Outline

Automotive drivers• Societal drivers• Automotive challenges• GM electrification strategy

Beyond lithium ion…a couple thoughtsProgress and challenges for lithium ion• How do lithium ion cells degrade?• Some potential approaches to solving degradation

challengesSummary

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19801980 19901990 20002000 20102010 20202020 20302030

Bill

ion

Bill

ion

Bill

ion

Bill

ion

World PopulationWorld PopulationVehicle ParcVehicle Parc

Sustainability Sustainability ChallengesChallenges

¶¶EnergyEnergy

¶¶EmissionsEmissions

¶¶SafetySafety

¶¶MegacityMegacity–– CongestionCongestion

–– ParkingParking

¶¶AffordabilityAffordability

PERSONAL MOBILITY MUST BE PERSONAL MOBILITY MUST BE REINVENTED FOR THE 21REINVENTED FOR THE 21stst CENTURYCENTURY

Data from U.S. Census Bureau and GM Global Market & Industry AnalysisData from U.S. Census Bureau and GM Global Market & Industry Analysis

++

+ +

NANA

NANA

EMERGING VS. MATURE MARKETS EMERGING VS. MATURE MARKETS ––GLOBAL COMPARISON: 2010GLOBAL COMPARISON: 2010

Source: GM Economics & Trade; IMF; U.S. Census Bureau/Source: GM Economics & Trade; IMF; U.S. Census Bureau/HaverHaver AnalysticsAnalystics

00

55

1010

1515

2020

ChinaChina EUEU U.S.U.S. JapanJapan BrazilBrazil IndiaIndia RussiaRussia CanadaCanada S. KoreaS. Korea AustraliaAustralia

Vehi

cle

Sale

s (M

)Ve

hicl

e Sa

les

(M)

20102010 20092009 20052005 20002000

TOP 10 MARKETS BY TOP 10 MARKETS BY NEW VEHICLE SALES IN 2010NEW VEHICLE SALES IN 2010

China Growth China Growth (%)(%)vs. 2009vs. 2009 vs. vs. 20052005 vs. 2000vs. 2000

33%33% 218%218% 735%735%

2010 Sales (M)2010 Sales (M)Emerging MarketsEmerging Markets 37.337.3

Mature MarketsMature Markets 36.336.3

World TotalWorld Total 73.673.6

¶ Liquid fuels– Future price & availability of oil?

– Efficacy of bio-derived fuels?

¶ Importance of zero on-vehicle “regulated emissions” vs. CO2emissions & energy security?– Fuel cells offer

1. Range2. Short re-charge times3. Zero emissions4. Technical efficacy now

– What else can do this?

¶ FCEVs vs. BEVs with fast charge vs. EREVs with bio-derived fuels?

Really BIG questionsReally BIG questions

1

2

3

4

5

6

50 75 100 125 150 175 200

Cost

of g

asol

ine

to p

erso

nal-

tran

spor

tati

on c

usto

mer

s, $

US/

gal

Cost of (crude) oil, $US/barrel

SwitchgrassWoody CropsAgricultural ResidueForest ResidueCorn

Etha

nol P

rodu

ctio

n, B

illio

n G

allo

ns

100

80

60

40

20

02010 2014 2018 2022 2026 2030

2030 Land Use44 M acrescropland aspasture andidle cropland

44 M acresnon-grazedforest land

No land usechange forresidues

Equals 2006 cornethanol acreage

SANDIA/GM STUDY:SANDIA/GM STUDY:BIOMASS FOR 90B GALLONS OF ETHANOLBIOMASS FOR 90B GALLONS OF ETHANOL

~1/3 US fuel supply

BATTERY TECHNOLOGY IMPROVEMENTS (HEV)BATTERY TECHNOLOGY IMPROVEMENTS (HEV)

GM FUEL CELL STACK PROGRESSGM FUEL CELL STACK PROGRESS

SupercapacitorSupercapacitorLead AcidLead Acid

1,2001,2001,0001,0008008006006004004002002000000

2525

5050

7575

100100

Specific Power (Watt/kg)Specific Power (Watt/kg)

Spec

ific

Ene

rgy

(Wat

tSp

ecif

ic E

nerg

y (W

att--

hr/k

g)hr

/kg)

Volumetric Power Density (kW/I)Volumetric Power Density (kW/I)

Gravimetric Power Density (kW/kg)Gravimetric Power Density (kW/kg)

Automotive TargetAutomotive Target33

22

11

00ST3ST3

19971997ST4ST4

19981998Stack 2000Stack 2000

20002000S2.1S2.120032003

S4S420042004

S5S520082008

In the interview (Technology Review 2009), Chu said that there are four "miracles" that need to happen before hydrogen fuel cells can be practical. Basically, he says, we need better ways to produce, distribute, and store hydrogen, and we need better, cheaper fuel cells. "If you need four miracles, that's unlikely: saints only need three miracles," he said.Underscores the importance of the scientific method…make things work first at the cell level.

1. Conventional lithium ion+ Specific power and energy

+ Life (cycle and calendar)– Abuse tolerance

• Martin Winter, Jürgen O. Besenhard, Michael E. Spahr, and Petr Novák, Adv. Mater. 1998.

• M. Stanley Whittingham, Chem. Rev. 2004.

Li+

EC+DEC

2. Solid state lithium ion+ Abuse tolerance

+ Specific energy– Specific power (particularly at low

temperatures)– Vibration resistance

Li+

Ceramicelectrolyteor Li0

• Boone B. Owens, J. Power Sources, 2000.

• Danilov, Niessen, and Notten, J. Electrochem. Soc., 2011

3. Li-air batteries+ Specific energy (note gain in cell

mass with discharge)– Life

– Specific power– Complexity

Li+

• Ceramic electrolyte over Li

• Organic solvent or membrane over cathode

• Kowalczk, Read, and Salomon, J. Pure Appl. Chem., 2007.

• 1Danilov, Niessen, and Notten, J. Electrochem. Soc., 2011

• Na|Air cell: Peled, Golodnitsky, Mazora, Goora, Avshalomova. J. Power Sources, 2010.

Fuel cell air

cathodeLi0

Characteristics at EOL (End of Life) High Power/Energy

High Energy/Power

Reference Equivalent Electric Range miles 10 40Peak Pulse Discharge Power (10 sec) kW 45 38Peak Regen Pulse Power (10 sec) kW 30 25Available Energy for CD (Charge Depleting) Mode, 10 kW Rate kWh 3.4 11.6Available Energy for CS (Charge Sustaining) Mode kWh 0.5 0.3Minimum Round-trip Energy Efficiency (USABC HEV Cycle) % 90 90Cold cranking power at -30°C, 2 sec - 3 Pulses kW 7 7CD Life / Discharge Throughput Cycles/MWh 5,000 / 17 5,000 / 58CS HEV Cycle Life, 50 Wh Profile Cycles 300,000 300,000Calendar Life, 40°C year 15 15Maximum System Weight kg 60 120Maximum System Volume Liter 40 80Maximum Operating Voltage Vdc 400 400Minimum Operating Voltage Vdc >0.55 x Vmax >0.55 x VmaxMaximum Self-discharge Wh/day 50 50System Recharge Rate at 30°C kW 1.4 (120V/15A) 1.4 (120V/15A)Unassisted Operating & Charging Temperature Range °C -30 to +52 -30 to +52Survival Temperature Range °C -46 to +66 -46 to +66Maximum System Production Price @ 100k units/yr $ $1,700 $3,400

USABC Requirements of End of Life Energy Storage Systems for PHEVs

P/E, 1/hr 13 3.3

P/E, 1/hr, EFlex/Volt: ~8

More battery requirements:www.uscar.org

= 0.5 and i0 = 300 mA/cm2 at 75oC

Conclusion: Li metal anodes in conventional aprotic solvents are initially impressive but are not stable.

Microdisk electrodes- Very high current densities- High sensitivity to interfacial phenomena

Surrounding electrode:• More nonuniform current

distribution• But lower average (nodule) current

Metal electrodes are problematic

Secondary current distribution with linear charge-transfer kinetics

Examine active and passive surrounding anode…which is preferred?

Lithiumelectrode

Metal oxide electrode

Ability of lamellar compounds of carbon to insert various species was well known by the later half of the 1800s (Schauffaütl, 1841…Sony, 1992)Aprotic solvents with high dielectric constants: W.S. Harris, Ph.D. Thesis, University of CA, Berkeley, 1958.Single fiber electrode: phenomena associated with the fabrication of a porous electrode do not obfuscate the subsequent characterization…use the Scientific Method to isolate critical characteristicsExtremely stable lithiated carbon anode and Li reference (there is still confusion around the stability of carbon lithiation!)

ImproveImproveVehicleVehicle

Fuel EconomyFuel Economyand and

EmissionsEmissions

DisplaceDisplacePetroleumPetroleum

Hydrogen Fuel Cell-Electric

Vehicles

Battery-ElectricVehicles (including

E-REV)Hybrid-ElectricVehicles (including

Plug-in HEV)IC Engine

and TransmissionImprovements

Petroleum (Conventional and Alternative Sources)

Alternative Fuels (Ethanol, Biodiesel, CNG, LPG)

Electricity (Conv. and Alternative Sources)

Hydrogen

TimeTime

ADVANCED PROPULSION ADVANCED PROPULSION TECHNOLOGY STRATEGYTECHNOLOGY STRATEGY

EnergyEnergyDiversityDiversity

GM VEHICLE ELECTRIFICATION STRATEGYGM VEHICLE ELECTRIFICATION STRATEGY

Petroleum and Biofuels (Conventional and Alternative Sources)

Electrification

GM Hybrid 2-Mode 2-Mode

PHEV Voltec

Electricity – ZEV Fuel

BatteryElectric Fuel Cell

Portfolio of solutions for full range of vehicles that provide customer choicePortfolio of solutions for full range of vehicles that provide customer choice

ConventionalConventionalPowertrainPowertrain

Electric PowerElectric Power

Equinox Fuel Equinox Fuel CellCell

GM’S PATH TO ELECTRIFICATIONGM’S PATH TO ELECTRIFICATION

FUN

CTIO

NA

LITY

Baseline 15-20% 30% RWD50% FWD

FWD: ~100% for (20) Miles,

50% After

40 MilesPure EV

30 MilesPure EV

Mid Hybrid

Full Hybrid

Plug-in Hybrid

Extended Range Electric Vehicle

Battery Electric Vehicle &Fuel Cell

All All ElectricElectric with Mechanical

Assist

Mechanical with Electric Mechanical with Electric Assist

DRI

VE

SYST

EM

Mechanical

Conventional Powertrain

INCREASING LEVELS OF ELECTRIFICATION AND EFFICIENCYINCREASING LEVELS OF ELECTRIFICATION AND EFFICIENCY

PROJECT DRIVEWAYPROJECT DRIVEWAY

2525--45 MILES45 MILESGASGAS--FREEFREE

1,850,0001,850,000MILES LOGGEDMILES LOGGED

INVENTION 1900sINVENTION 1900s REINVENTION TODAYREINVENTION TODAY

REINVENTING PERSONAL URBAN MOBILITY: REINVENTING PERSONAL URBAN MOBILITY: ENEN--V (V (ELECTRICELECTRIC, , NETWORKEDNETWORKED VEHICLE)VEHICLE)

Battery Technology Improvementsand the EVre Challenge

Range

Acceleration

Energy(Watt-hr / kg)

Power (Watt / kg)

Maximum stored energy per unit of battery mass

Maximum power per unit of battery mass

EVre(Volt: 8-year, 100k mile)PHEV

EV

EVre: High specific power (kW/kg) and energy (kWh/kg)

Lithium ion challenges

Cost• Can we size pack closer to end-of-life requirements?• Can we reduce materials & processes costs?

Life• How do electrodes fail?• Can we develop an accelerated life test?

Temperature tolerance• Can we improve low temperature power?• Why is battery life shorter at higher temperatures?

Chemical degradation• Critical role of SEI (solid electrolyte interface) to impede deleterious

degradation reactions within lithium ion cells• Calendar life determined by chemical degradation

Mechanical degradation• Cyclic expansion and contraction of insertion or alloy materials leads to

fatigue, cracking, and structural changes

• Cyclic life issues are affected by mechanical degradation and chemical degradation

Durability…terminologies, bathtub curves

Number of Failures

Time in service

Early (infant mortality) failures

Wear out failures

Useful life(durability)

2 Li + 2 (CH2OCO2Li)2 + H2C=CH2 + 2

• Solvent reduction at ~0.8V vs Lion first cycle

• Then ~100% Coulombic efficiency • Next slide for more detail

On the importance of Coulombic efficiency I

Cycle Capacity1 (Ah0) I2 [(Ah0) I ] I3 [(Ah0) I I ] I

N (Ah0)( I)N

For N = 5000 cycles and a 12/16 or 75% capacity retention,the current efficiency per cycle must be such that

[Ah0( I)N ]/Ah0 > 0.75, or I > (0.75)(1/5000) , hence I > 0.99994.

• This is why very low rates of lithium-consuming reactions can lead to premature cell failure. The rates can be so low that they are not measureable in terms of seeing current maxima associated with solvent reduction.

• Note: high capacity negatives (Si, Sn based)…large challenge!

21

21

Li+ + e- + LiCH2CH2OCO2Li

1

Iron phosphate vs. Li- Little voltage variation

Graphite vs. Li- Voltage variations

Graphite|iron-phosphate cell…excellent power density, life, and potential for low cost. Challenged on energy density.

2

2.25

2.5

2.75

3

3.25

3.5

3.75

4

0 0.25 0.5 0.75 1 1.25 1.5 1.75 2 2.25 2.5

Cel

l pot

entia

l, V

Cell capacity, Ah

P0

P5

Graphite|FePO4 cell45oC, C/2, 90% DOD

Cell capacity loss

963 cyclesNew

Charged, FePO4 & Li~0.8C6 Discharged, LiFePO4 & C6

• Same as previous plot with the exception that origin now is at the fully discharged state…clear that distance between graphite peaks is nearly constant

• Conclusion: lithium consumption (at the negative electrode surface) is leading to capacity decline

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

0 0.25 0.5 0.75 1 1.25 1.5 1.75 2 2.25 2.5

d(C

ell p

oten

tial,

V)/d

(Cap

acity

, Ah)

Cell capacity, Ah

P0

P5

Graphite|FePO4 cell45oC, C/2, 90% DOD

Cell capacity loss

963 cycles

New

Discharged Charged

Utility of dV/dQ vs Q, uniform shifting of peaks for graphite/FePO4 cells

2

• Current efficiency must be 0.9999 to reach 1000 cycles with 80% of initial capacity.

• A current efficiency of 0.99 yields 23 cycles!

Chemical-mechanical degradation at the negative electrode

Expansion & contraction

upon charge & discharge,

respectively.

2232 CHCHCOLi S2 S]-2[Li...gassesSEIO-H-RS]-[Li

Increased disorder and cracking• Consistent with loss of active lithium

Electrode isolation and loss of active material when cracks join• Consistent with additional

loss of negative capacity

Cracks via cycling

SEI forms on newly exposed surfaces (cracks)

THIS IS A LARGE CHALLENGE FOR HIGH CAPACITY ELECTRODE MATERIALS

M. W. Verbrugge and Y-T. Cheng, “Stress and Strain-Energy Distributions within Diffusion-Controlled Insertion-Electrode Particles Subjected to Periodic Potential Excitations,” J. Electrochem. Soc., 156(2009)A927.

3

Current and next generation negative electrodes

LiC6372 mAh/g (theoretical)

Si: clear “theoretical winner”

Dominique Larcher, Shane Beattie, Mathieu Morcrette, Kristina Edström, Jean-Claude Jumas and Jean-Marie Tarascon, “Recent findings and prospects in the field of pure metals as negative electrodes for Li-ion batteries,” J. Mater. Chem., 2007, 17, 3759 – 3772

X. Xiao, P. Liu, J. S. Wang, M. W. Verbrugge, and M. P. Balogh, “Vertically Aligned Graphene Electrode for Lithium Ion Battery with High Rate Capability,” Electrochemistry Communications, 13 (2011) 209–212.

Nano-stabilization: thin films, small particles…surface forces for stabilizationNanometer thick aligned graphenefilms show excellent stabilityShould be helpful for characterization of the graphite-electrolyte interfacePerhaps useful for very high specific power applications• (Low energy due to

thin film approach as presented)

Li

Li

Li

Li

Li

Li

Li

Li

Li0

Li

Li+ + e Li0(Intercalation reaction)

Conventional graphite anode.M. W. Verbrugge and B. J. Koch, “Electrochemical Analysis of LithiatedGraphite Anodes,” J. Electrochem. Soc., 150(2003)A374.

• Graphite, ~80 to 90% by mass• Binder, ~5 to 10% • Electronically conductive diluents,

~0 to 10%

e

Li+/Li0

Aligned Graphene Electrode No binder or conductive diluentsElectron transport along graphene planes; Li transport between planes.

Si Patterns

The crack spacing is around 5 to 10 microns, comparable to the pattern with 2000 mesh size.

Pattern size 7 x 7 µm2

Gap: 7 µm

Pattern size 40 x 40 µm2

Gap: 15 µmPattern size 17 x 17 µm2

Gap: 10 µm

• Can the gaps provide necessary stress relaxation?

• How large of a pad size can be accommodated?

Related Si island works

X. Xiao, P. Liu, M. W. Verbrugge, H. Haftbaradaran, and H. Gao, Journal of Power Sources , 196 (2011) 1409–1416

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In-situ Stress Measurement with MOSS system(Multibeam Optical Stress Sensors)

f in-plane film stressh f film thicknessMs substrate biaxial modulusHs substrate thicknessR substrate radius of curvature

RHMh

Lddd

R

ssff2

0

0

61EquationStoney

2cos1

curvatureWafer

See Janssen et al., “Celebrating the 100th anniversary of the Stoney equation for film stress: Developments from polycrystalline steel strips to single crystal silicon wafers,” Thin Solid Films 517 (2009) 1858–1867.

36

Si islands

Quartz substrate

Quartz substrate

Cu or Ti current collector Through-masksputtering

Si Si Si Si Si SiSi Si

41 x 41 µm2, 10 µm gap 17 x 17 µm2, 7 µm gap 7 x 7 µm2, 6 µm gap

SEM images of through-mask, sputtered, patterned Si film

Preparation of Si patches

See also Sumit K. Soni, Brian W. Sheldon, Xingcheng Xiao and Anton Tokranov, “Thickness effects on the lithiation of amorphous silicon thin films,” Scripta Materialia 64 (2011) 307–310.

Comparison of 50 nm thick Si samples: continuous film vs. 7x7 µm2 pattern

Voltage (V) vsLi/Li+

Continuous Film Patterned Sample2nd & 3rd Cycle

onset of flow

No evidence of flow

Stress recovered

Note stress ordinate scales differ

Solid mechanics

h = 0.1 m

We seek the minimum crack spacing Lcr that does not allow an extra crack to be formed in between the existing cracks.

Below this minimum crack spacing, the stress in the lithiated Si film can not reach its plastic yield stress and therefore no strain localization in the film can take place to form an additional crack.

!!

a

b

c

d

Discharge

Charge (lithiation)

Related works• Wen, C.J. and Huggins, R.A.,

“Electrochemical Investigation of the Lithium-Gallium System,” J. Electrochem. Soc., 128 (8): 1636-1641 (1981).

• Saint, J., Morcrette, M., Larcher, D., and Tarascon, J.M., “Exploring the Li-GaRoom Temperature Phase Diagram and the Electrochemical Performances of the LixGay Alloys vs. Li,” Solid State Ion., 176 (1-2): 189-197 (2005).

M. W. Verbrugge,1 R. D. Deshpande,2 J. Li,2 and Y-T. Cheng,2 “The search for high cycle life, high capacity, self healing negative electrodes for lithium ion batteries and a potential solution based on lithiated gallium,” 2011 MRS Spring Meeting Symposium M Paper Number 1029460.

1Chemical Sciences and Materials Systems Laboratory, General Motors Research andDevelopment Center, Warren, MI 48090, USA2Department of Chemical and Materials Engineering, University of Kentucky, Lexington,Kentucky 40506, USA

Microscopy of self-healing electrode

a. Liquefied Gab. Fully lithiated,

solid Li2Gac. Cracks from on

de-lithiation(tension over the solid surface)

d. Cracks vanish; de-lithiated, liquefied Ga

a b

c d

a

b

c

d

Discharge

Charge (lithiation)

XRD

a. Liquefied Gab. Fully lithiated, solid

Li2Gad. Crack vanish; de-

lithiated, liquefied Ga

a

b

c

d

Discharge

Charge (lithiation)

(d)

(b)

(a)

Liquefied Ga

Mechanistic summaryLi2xGa system (0 < x < 1) at 40oC

Cracks are self-healed by the solid-to-liquid phase transformation upon discharge of the negative Li2xGa electrode

LM: Liquid Metal

a

b

c

d

Discharge

Charge (lithiation)

traction batteries: automotive requirements, current...

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