low temperature performance characterization · low temperature performance characterization...

Low TemperaturePerformance Characterization Presented by Andy JansenChemical Sciences and Engineering Division

Tuesday, February 26th, 2008

DOE Vehicle Technologies Program Annual Merit Review, FY2008 Hybrid Electric Systems Energy Storage / Applied Battery Research Bethesda, Maryland

This presentation does not contain any proprietary or confidential information.

Vehicle Technologies Program

Outline Purpose of Work Address Previous Review Comments Barriers Approach Performance Measures and Accomplishments

– Power pulse level – Surface area – Non-carbonate solvents – Surface modifications

Technology Transfer Publications/Patents

Plans for Next Fiscal Year Summary


Purpose of Work

Understand the extent of the poor low temperature performance of lithium-ion batteries by characterizing the behavior of a wide range of non-traditional solvents, salts, active materials, and surface morphologies.


Reviewer Comments from Aug.’06 Merit Review

“Low temperature work should determine the root cause of the problem.” – The ATD program continues to develop in-situ diagnostics techniques to

determine the root cause(s) of low temperature performance degradation. Recent work proved performance is kinetic limited.

“Investigate additives for low T, formation.” – Additives are continuously evaluated and screened in ATD. Additives will

also be screened for improved low temperature performance.

“Vary electrode surface area to assess affect of interfacial impedance.” – Studied graphites from ConocoPhillips that are ideal for this particular

investigation.


Barrier: Li-ion Cells Lose Power when ColdH

PPC

10-

sec

ASI

, Ohm

-cm

2 Comparison of Gen2 and Gen3 Electrodes in Various Electrolytes

1000

100

10

32 cm2 Area Evaluated at 3.8 V

-30 °C

30 °C

0 °C

0.0032 0.0034 0.0036 0.0038 0.004 0.0042 Inverse Temperature, 1/K

Gen2 Electrodes and 1.2M LiPF6 in EC:EMC (3:7 w/w) (BID 1935), 4.1V, 3 Sep.Gen2 Electrodes and 1.2M LiPF6 in EC:EMC (3:7 w/w) (ANJ005), 4.0V, 1 Sep.Gen3-F Electrodes and 1.2M LiPF6 in EC:EMC (3:7 w/w) (BID 2067), 4.1V, 3-Sep.Gen3-F Electrodes and 1.2M LiPF6 in EC:PC:DMC (1:1:3: w/w) (BID 2003), 4.1V, 3-Sep.Gen3-D Electrodes and 1.2M LiPF6 in EC:EMC (3:7 w/w) (BID 2127), 4.0V, 1 Sep.

JPL Gen3-D Electrodes and 1M LiPF6 in EC:DEC:DMC:EMC (1:1:1:3 v/v) (BID 2126), 4.0V, 1 Sep. K.Gering Gen3-D Electrodes and 1.1M LiPF6 in EC:GBL:EP (1:1:3 v/v) (BID 2128), 4.0V, 1 Sep.

Gen3-D Electrodes and 1.1M LiPF6 in EC:GBL:DMC:EP (4:3:2:11 v/v) (BID 2129), 4.0V, 1 Sep. K.Gering

All cells have similar low

temperature behavior (same

activation energy).


SS 316 Spacer

Li

SS 316 Top Plate (Positive)

SS 316 Base (Negative)

Approach

Identify and systematically investigate physical and electrochemical properties that could influence low temperature performance using tailored test apparatus – Active Material ⌧

– Conductivity ⌧

– Lithium Salt ⌧

– Charge or Discharge ⌧

– Salt Molarity ⌧

– Electrolyte Viscosity ⌧

– Binder ⌧

Li Reference

(Outside Cell Area) LiySnReference

(Between Electrodes)

LiySn Wave Spring

PE Gasket

O-ring

Pos. Electrode 3 Separators Neg. Electrode

Li Reference

(Outside Cell Area)LiySnReference

(Between Electrodes)

SS 316 Spacer

LiLiySn

SS 316 Top Plate (Positive)

SS 316 Base (Negative)

– Kinetic or Diffusion Limited – Surface Area – Carbonate Solvents – Supporting Electrolytes – Inherent Lithium Redox Reaction Kinetics


Impedance Depends Strongly on Current at LowTemperature

HPPC 10-s Discharge ASI near 3.8 V for Gen2 System (ANJ005) A decreasing resistance with increasing current may seem counter-intuitive, but this phenomena is fully explained by Butler-Volmer kinetics.

0

100

200

300

400

500

600

700

800

0 5 10 15 20 Current Density, mA/cm²

AS

I, O

hm-c

m²

ASI at 30°C ASI at 0°C ASI at -10°C ASI at -20°C ASI at -30°C HPPC 10-s Discharge ASI near 3.8 V for Gen2 System (ANJ005)

10

100

1000

AS

I, O

hm-c

m²

ASI at 30°C ASI at 0°C ASI at -10°C ASI at -20°C ASI at -30°C

0 5 10 15 20Current Density, mA/cm²


-15

0

5

10

15

HPPC Data Obey Classic Butler-Volmer Kinetics

Current Density vs. Overpotential During 10-s HPPC Pulses for Current Density vs. Overpotential During 10-s HPPC Pulses for Gen2 System (ANJ005) 3

Gen2 System (ANJ005)

30°C 0°C -10°C -20°C -30°C

Discharge

Charge

-1

-5 -2

-10 -3

Cur

rent

Den

sity

, mA

/cm

²

-300 -200 -100 0 100 200 300 Overpotential, mV

30°C 0°C -10°C -20°C -30°C

Discharge

Charge 2

1

Cur

rent

Den

sity

, mA

/cm

²

0

Exchange current (i0) increases-20

-800 -600 -400 -200 0 200 400 600 with temperature Overpotential, mV Nearly symmetric current

overpotential response, i.e., charge and discharge resistance are nearly identical


Butler-Volmer Kinetics Refresher Butler-Volmer Current-Overpotential Relationship

i = i0 ⎡⎢⎣ e αnFη

RT −(1−α )nFη

RT ⎤8 − e ⎥⎦6

4

η = (V −Veq )2

0

1 di nFi0 ⎡ αnFη RT

−(1−α )nFη RT ⎤-2

R =

dη=

RT ⎢⎣αe + (1−α )e ⎥⎦-4

-6

-8 In real life, current does not go off to-200 -100 0 100 200 infinity with increasing overpotential – at

Overpotential, mV some point mass transfer (diffusion) limitssee “Electrochemical Methods” by Bard and Faulkner the current.

Linear Region Tafel Region Limiting currents were not observed for

1 nFi0 1 αnF these studies within the operating voltage η ≈ 0 = = i used (2.9 to 4.3 V).

R RT R RT

Cur

rent

Den

sity

, mA

/cm

²

Total Current, mA/cm² Anodic Current, mA/cm² Cathodic, mA/cm²

io

io

Oxidation

Reduction


Activation Energy Clearly Increases Below 0 °CA

SI,

Ohm

-cm

²

ASI at 0 and 2.5 mA/cm² for Gen2 System (ANJ005) 1000

100

10

R (0 mA/cm²) (ANJ005) R (2.5 mA/cm²) (ANJ005)

30 °C

-30 °C

0 °C

Ea = 50 kJ/mole

Ea = 22 kJ/mole

Ea ≈ 34 kJ/mole

The low temperature activation energy will decrease as the current (or overpotential) increases.

It is generally bounded between 34 and 50 kJ/moles for normal operating voltages.

0.0032 0.0034 0.0036 0.0038 0.004 0.0042 Inverse Temperature, 1/K


Explore Surface Area Effects with ConocoPhillips’Graphite

0.7-1.013-17CGP-G15 2.011.8MCMB-10

1.5-27-9CGP-G8

2.0-3.04-6CGP-G5

Surface Area BET, m2/g

Particle Size D50, µm

Material

The graphites from ConocoPhillips are well suited for surface area studies because of their similar processing that results in nearly identical morphology.


Higher Surface Area Improves Power at allTemperatures, But Not Enough

Comparison of ConocoPhillips' Graphites ConocoPhillips’ graphites 1000

CGP-G5 (JV1281) CGP-G8 (JV1282)

CGP-G15 (JV1283) MCMB10 -Gen3D (BID 2127)

Constant Voltage Charge Area = 32 cm2

Evaluated at 3.8 V 1.2 M LiPF6 in EC:EMC (3:7 wt)

Gen3-D Positive 30°C

-30°C

0°C

have an impedance response very similar to the ATD’s Gen3 graphite.

Higher surface area will

10-s

HP

PC

Dis

ch. A

SI,

Ohm

-cm

²

100 not by itself solve the low temperature problem.

HPPC 10-s ASI at 3.8 V and -30 °C 900

850

0 1 2 3 BET Area, m²/g

AS

I, O

hm-c

m²

10 800

0.0032 0.0034 0.0036 0.0038 0.004 0.0042Inverse Temperature, 1/K

750

700

650

600


Non-Carbonate Based Electrolytes Also Sufferfrom Low Temperature Power Loss

HP

PC

10-

s A

SI,

Ohm

-cm

²

Comparison of Solvents with Li4Ti5O12 (Kyorix) vs. Gen3-D Positive

10000

1000

100

10

1.2 M LiPF6 in EC:EMC (3:7w) (ANJ009) 1 M LiPF6 in GBL (ANJ012) 1 M LiPF6 in DEC (ANJ013) 1 M LiPF6 in ACN (ANJ014) 0.8 M LiBOB in MEK (ANJ026)

Constant Voltage Charge Area = 32 cm2

Evaluated at 2.2 V

30 °C

-30 °C

0 °C

Other solvents suffer too: – Diethyl Carbonate – γ-Butyrolactone – Acetonitrile – Methyl Ethyl Ketone – Many others!

• Substituted furans • Oxazolines • Esters • Sulfolanes • Thiazolines

No solvent (or additive)0.0032 0.0034 0.0036 0.0038 0.004 0.0042 Inverse Temperature, 1/K system has been found yet

that has a significantly lower activation energy.


0 °C

1

Surface Modifications Do Not Have a SignificantEffect on Low Temperature Performance

Hitachi Chemical’s natural graphite (SMG) and soft carbon (SC) Constant Voltage Charge 1000

31.6 3.0 to 4.0

cm² electrV

ode area 0.950.63

mA/cm² a mA/cm²

t 30 °C at 0 °C

0.32 mA/cm² at -30 °C

SMSM

SCSC

G-Blank-20 Graphite (ANJ015) G-NAL1-20C Graphite (ANJ016)

-Blank-10 Soft Carbon (ANJ017) -CAL1-10B Soft Carbon (ANJ018)

SMG-Blank-20 Graphite (ANJ015)

SMG-NAL1-20C Graphite (ANJ016)

SC-Blank-10 Soft Carbon (ANJ017) SC-CAL1-10B Soft Carbon (ANJ018)

30 °C

-30 °C

Evaluated at 3.8 V 31.6 cm² electrode area

1.2 M LiPF6 in EC:EMC, Gen 3d (+) 4.7 mA/cm² pulse at 30 °C 3.2 mA/cm² pulse at 0 °C

0.8 mA/cm² pulse at -30 °C

0.9

0.8

0.7

0.6

0.5

0.4

0.3

0.2

0.1

Dis

char

ge C

apac

ity, m

Ah/

cm²

HP

PC

AS

I, O

hm-c

m²

100

100 0.0032 0.0034 0.0036 0.0038 0.004 0.0042

-40 -30 -20 -10 0 10 20 30 40 Inverse Temperature, 1/K Temperature, °C

Soft carbon’s better performance in this study is most likely due to its smaller jagged particles (exposed surface area and morphology).


Technology Transfer

Intellectual property generated under this project is available for licensing through Argonne’s Office of Technology Transfer

Results are made available to the DOE, USABC, and battery developers and suppliers at regular review meetings

Results are made available to the general public via – Technical reports and journal articles – Presentations at technical meetings – HEV website (coming soon from Ira Bloom)


Publications/Patents “Low-Temperature Study of Lithium-Ion Cells using a LiySn Micro-Reference Electrode”, A.N. Jansen, D.W. Dees, D.P. Abraham, K. Amine, G.L. Henriksen, J. Power Sources, 174 (2007) 373.

“Investigating the Low-Temperature Impedance Increase of Lithium-Ion Cells”, D.P. Abraham, J.R. Heaton, S.-H. Kang, D.W. Dees, A.N. Jansen, J. Electrochem. Soc., 155 (2008) A41.

“Temperature Dependence of Capacity and Impedance Data from High-Power Lithium-ion Cells”, D.P. Abraham, E.M. Reynolds, P.L. Schultz, A.N. Jansen, D.W. Dees, J. Electrochem. Soc., 153 (2006) A1610-1616.

“Theoretical Examination of Reference Electrodes for Lithium-Ion Cells”, D.W. Dees, A.N. Jansen, D.P. Abraham, J. Power Sources, 174 (2007) 1001.

“Electrolytes for Lithium Ion Batteries”, John Vaughey, Andrew Jansen, and Dennis Dees (inventors), Filing Provisional Patent Application.


Future Plans Modify Double Layer with

– Fluorinated carbonate electrolytes (FEC:EC:EMC) – Supporting electrolytes (modify double layer)

• (Bu)4NPF6, (Bu)4PPF6, (Et)4NPF6, (CH3)4NPF6, NH4PF6, etc. • Cs2CO3 (cesium doesn’t intercalate into graphite)

Investigate use of low temperature ionic liquids

Explore Li-ion aqueous cell to shed insight on lithium kinetics at low temperature

Consider cell system that uses sodium (or magnesium) as the active species also to shed insight on kinetics

Continue NMR studies

Assess feasibility of using ketone-based solvents – Size of organic groups (R-CO-R’) – Non-HF forming salts or addition of Lewis Acid inhibitors


Summary Impedance response at low temperature is clearly dominated by Butler-Volmer kinetics and not diffusion

Carbonate-based solvents are not likely responsible for the poor low temperature performance

– Other solvents (ACN, GBL, ketones, sulfolanes, esters, etc.) had similar problems

High surface area particles do improve the low temperature performance but are only part of the solution, and they may cause abuse tolerance concerns at higher temperatures

Surface modification of graphite and soft carbon does not affect the low temperature performance (as expected)


Contributors and Acknowledgments

Jack Vaughey (Argonne) Gary Henriksen (Argonne) Dennis Dees (Argonne) John Muntean (Argonne) Kevin Gering (INL) Chris Johnson (Argonne) Jun Liu (Argonne) Sun-Ho Kang (Argonne) Holly LaDuca (Argonne) Khalil Amine (Argonne) Chris Joyce (Argonne) Nick Veselka (Argonne) ConocoPhillips Co. Daniel Abraham (Argonne) Hitachi Chemical Co., Ltd.

Support from Tien Duong and David Howell of the U.S. Department of Energy’s Office of Vehicle Technologies Program is gratefully acknowledged.


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