Screening of Electrode Materials & Cell Chemistries and ... Technologies Program Screen Electrode...

Vehicle Technologies Program

Screen Electrode Materials & Cell Chemistriesand

Streamlining Optimization of Electrode

Wenquan Lu

Electrochemical Energy StorageChemical Sciences and Engineering DivisionArgonne National Laboratory

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

Vehicle Technologies Annual Merit Review and Peer EvaluationWashington, D.C.May 9th – 13th , 2011

Project ID: ES028

Vehicle Technologies ProgramVehicle Technologies Program 2

Overview

Start – Oct. 2008 Finish – Sep. 2014 ~45% Complete

An overwhelming number of materials are being marketed by vendors for Lithium-ion batteries.

No commercially available high energy material to meet the 40 mile PHEV application established by the FreedomCAR and Fuels Partnership.

The impact of formulation and fabrication on performance of electrode materials with a broad variation of chemical and physical properties.

Timeline

Budget

Barriers

Total project funding in FY2010

–Screening: $350K

–Streamlining: $300K

Partners and Collaborators Andrew Jansen (Argonne National Laboratory)

Sun-Ho Kang (Argonne National Laboratory)

Dennis Dees (Argonne National Laboratory)

Jai Prakash and Aadil Benmayza (Illinois Institute of Technology)


Project I: Objectives of Material Screening

To identify and evaluate low-cost cell chemistries that can simultaneously meet the life, performance, abuse tolerance, and cost goals for Plug-in HEV application.

To enhance the understandingof advanced cell components on the electrochemical performance and safety of lithium-ion batteries.

Identification of high energy density electrode materials is the key for this project.

100 Wh/kg145 Wh/L

145 Wh/kg207 Wh/L

70%

PHEV

Battery System Level

Material Requirements

150 160 170 180 190 200 210 220 230300

350

400

450

500BOL 40 mile PHEV

130kg

Assumption:Fix material density (Gen2)

Norminal Voltage, V 3.6ASI, ohm-cm2 50Range(CD:70%), mile 40Battery power, kW 50.0Capacity at C/3, Ah 60.0Number of modules 7Cells per module 12Cells per battery 84

Cathode Capacity, mAh/g

Anod

e C

apac

ity, m

Ah/g

95.00

100.0

105.0

110.0

115.0

120.0

125.0

130.0

135.0Tota

l Bat

tery

Wei

ght,

kg

120kg

100kg

Calculated using ANL’sBattery Design ModelCalculated using ANL’sBattery Design Model


Approach: Test Protocol Development

Test protocol has been defined in “Battery Test Manual for Plug-in Hybrid Electric Vehicles” by INL 2010.

Accordingly, test procedure and method have been translated to fit the material screening purpose.

Characteristics at EOL (End of Life)

High Power/Energy Ratio

High Energy/Power Ratio

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 0.3Maximum System Weight kg 60 120Maximum System Volume Liter 40 80

USABC Requirements of Energy Storage Systems for PHEV

Material Identification

Material Characterization

(XRD, SEM, BET, Particle size, etc.)

ElectrochemicalEvaluation

Specific Capacity (energy)

IrreversibleCapacity

Loss

HybridPulsePower

Characterization

RateCapability

Thermal Investigation

CapacityRetention


Technical Accomplishments Several high energy electrode couples, surface treated natural graphite and composite

cathode materials, have been identified and studied. – Test results have been reported to suppliers.– Information is also delivered to cell fabrication team under ABR program (A. Jansen)

Other cell components, such as electrolyte, redox shuttle, conductive additive, binders, etc., are also investigated.

Fluorinated electrolyte (Daikin)

Conductiveadditive

Composite cathode

High voltage spinel

Surface coated graphite (ConocoPhillips)

Surface modified graphite(Hitachi Chemical)

Redox shuttle (ANL)

Carbon black (Cabot)

Copper (Somer Thin Strip)

Carbon coated Aluminum (Showa Denko)


Highlight 1: Composite Cathode Materials

0 50 100 150 200 250 300

2.0

2.5

3.0

3.5

4.0

4.5

5.0

Volta

ge, V

Capacity, mAh

charg-1 charg-2 charg-3 disch-1 disch-2 disch-3

327

Li/NCM cell4.6V~2.0V0.343mA1st charg: 300mAh/g1st disch: 249mAh/gICL: 17%

Toda Kogyo0.5Li2MnO3 • 0.5LiNi0.37Co0.24Mn0.39O2

C/10 C/3Average voltage V 3.64 3.58Specific capacity mAh/g 246 222ICL % 17Energy density mWh/g

full cycle 4.6~2.0 897 790Capacity retention % (50 cyc) 90

(1-x)Li2MnO3 xLiMO2 cathode materials, where M is a collection of transition metals and the average oxidation state of M is trivalent, have been used to increase the energy density for advanced batteries.

The boost in energy density is due to the electrochemical activation of Li2MnO3domains in the composite material.


Rate Performance of Composite Cathode Material

Excellent rate performance up to 1C with 194 mAh/g.

Small impedance during HPPC between 10% and 70% DOD.

0 1 2 3 4

2

3

4

5

Li/NCM Cell4.6V~2.0V

Volta

ge, V

Capacity, mAh

C/5 C/3 C/2 1C

327

230220210194

3.2 3.4 3.6 3.8 4.0 4.2 4.40

20

40

60

80

100

120

140

pulse regen

ASI,

ohm

-cm

2

Voltage, V

nl327

Li/Toda cellHPPC3C/2C


Voltage Depression of Composite Cathode Material

2.0 2.5 3.0 3.5 4.0 4.5 5.0-6

-4

-2

0

2

4

6 Li/composite Cell4.6V~2.0Vformation: 20mAh/gcycling: 67mAh/g

dQ/d

V, m

Ah/V

Voltage, V

7 17 27 37

nl330

0 1 2 3 4 5

2

3

4

5

Li/NCM Cell4.6V~2.0Vcycling: 67mAh/g

Volta

ge, V

Capacity, mAh

7 17 27 37

nl330

voltage depression

Composite cathode material shows very good capacity retention during cycling.

However, voltage depression during cycling was observed, which may affect the energy density.

0 10 20 30 400

1

2

3

4

5

6

Ca

pacit

y, m

Ah

Cycle number

Li/composite Cell4.6V~2.0Vformation: 20mAh/gcycling: 67mAh/g

91%

nl330


Thermal Property of Composite Cathode

DSC results indicates that the on-set temperature of exothermic reaction of the fully charge composite is 215oC, same as LiNi0.8Co0.15Al0.05O2 at 4.2V.

The total heat generation of fully charged composite is about 1184J/g, which is less than LiNi0.8Co0.15Al0.05O2 at 4.2V.

50 100 150 200 250 300 350-5

0

5

10

15

20

25

30

35

40

Heat

, µJ/

sec

Temperature, oC

NCA composite

4.2V4.6V

1184J/g

1878J/g

Scan rate: 10oC/min


Highlight 2: Fluorinated Electrolyte from Daikin

Electrolyte=Solvent + Salt

LiNi0.8Co0.15Al0.05O2•High Current Overcharge•High Temperature

Fluorinated electrolyte may address safety concerns caused byheat and pressure build-up within the cell and the flammable electrolyte, since it has:

Higher operational voltage window Lower reactivity to anode and cathode Thermally stable

10Illinois Institute of Technology


-10

-8

-6

-4

-2

0

250 100 150 200 250 300 350 400

Nor

mal

ized

Hea

t Flo

w (W

/g)

Temperature (oC)

FE1Gen2

Pros and Cons of Fluorinated Electrolyte

-300

-250

-200

-150

-100

-50

0

503 3.5 4 4.5 5 5.5 6

Voltage, V vs Li/Li+

Cur

rent

Den

sity

(µA

/cm

2)

GenII

FE

FE1

WE: Glassy Carbon

RE: Li

CE: Li

Scan Rate: 0.5 mv/s

-300

-250

-200

-150

-100

-50

0

503 3.5 4 4.5 5 5.5 6

Voltage, V vs Li/Li+

Cur

rent

Den

sity

(µA

/cm

2)

GenII

FE

FE1

WE: Glassy Carbon

RE: Li

CE: Li

Scan Rate: 0.5 mv/s

Electrolyte composition:Gen II: 1.2 M LiPF6 EC/EMC (3/7)FE1: 1.2M LiPF6 FEC/EMC (3/7)

Electrolyte conductivity

[Fluorinated Materials for Energy ConversionT Nakajima and H. Groult, 2005]

C-H : Binding energy: 417kJ/molC-F : Binding energy: 486kJ/molElectron negativity: H /2.1; F/4.0

Fluorinated Solvent

Safer Electrolyte Conductivity (mS/cm)

GenII 1.2M LiPF6 in EC/EMC (3:7) 8.2

FE 1.2M LiPF6 FEC/EMC/D2 (2:4:4) 7.2

Electrolyte Conductivity (mS/cm)

GenII 1.2M LiPF6 in EC/EMC (3:7) 8.2

FE 1.2M LiPF6 FEC/EMC/D2 (2:4:4) 7.2

FE1 1.2M LiPF6 FEC/EMC(3:7) 4.8

FE1 1.2M LiPF6 FEC/EMC(3:7) 4.8


Comparable performance at lower rates.

At high rates especially at 1C and 2C the cathode with Gen2 electrolyte shows better performance than FE1.

100

110

120

130

140

150

160

170

180

0 4 8 12 16 20

Spec

ific

Dis

char

ge C

apac

ity (m

Ah/

g)

Cycle_Index

Gen2 FE1

C/10 C/5 C/3 C/2 1C 2C

Rate Performance of Fluorinated Electrolytes


Onset Temperature (˚C) ΔH(J/g)

State of charge (%) Gen2 FE1 Gen2 FE1

100 206 220 1183 1009

80 209 232 1100 788

40 238 273 624 243

20 252 280 394 240

DSC Results of Fluorinated Electrolyte

-14

-12

-10

-8

-6

-4

-2

0

250 100 150 200 250 300 350 400

Nor

mal

ized

Hea

t Flo

w (W

/g)

Temperature (oC)

Gen2_20%SOCGen2_40%SOCGen2_80%SOCGen2_100%SOC

-14

-12

-10

-8

-6

-4

-2

0

250 100 150 200 250 300 350 400

Nor

mal

ized

Hea

t Flo

w (W

/g)

Temperature (oC)

FE1_20%SOCFE1_40%SOCFE1_80%SOCFE1_100%SOC

Gen2

FE1 Higher on-set temperature

and less total heat generation were observed to FE1 electrolyte at various state of charge compared to Gen2 electrolyte.


Summary Composite cathode materials

0.5Li2MnO3 0.5LiNi0.37Co0.24Mn0.29O2– Deliver 897Wh/kg, more than 70% of

conventional LiCoO2. – Good rate performance: 210mAh/g @ C/2.– Area specific impedance is about 40 ohm-cm2

at 50% DOD.– 91% capacity retention within 40 cycles.– Less heat generation at fully charged state

compared to NCA.

Daikin’s Fluorinated ethylene carbonate (FEC)

– Less capacity is delivered @ 1C due to low conductivity of FEC.

– DSC results indicate better thermal stability at various state of charge.

Surface modified graphites from various vendors have been investigated. They all show high capacity, good rate capability and thermal stability and will be used for cell build at ANL.

Other cell components, such as redox shuttle, binder, separator, carbon additive, current collector have been studied.

To continue to search and evaluate the high energy density electrode couples to meet the performance and cost goal for PHEV applications.

– (1-x)Li2MnO3 xLiMO2 – Surface modified graphite– Silicon and its composite– Hard carbon (Kureha)

Other available cell chemistries for lithium battery

– Electrolyte, additives, redox shuttles– Separators – Current collector– Binder– Conductive additives

Support electrode and cell build project under ABR program

– Electrode thickness Support material scale up

program at ANL

Future Plans


Project II: Objectives and Approach of Streamlining the Optimization of Electrode

To establish the scientific basis needed to streamline the lithium-ion electrode optimization process.

– To identify and characterize the physical properties relevant to the electrode performance at the particle level.

– To quantify the impact of fundamental phenomena associated with electrode formulation and fabrication (process) on lithium ion electrode performance.

Particlesize

Pore structure

Surface area

Particle morphology

material

Power

Energy

outputConductive

additive

Porosity

laminate

Binder

Thickness

Currentcollector

Separator

cell

Tab

General approachNew approach


Technical Accomplishments

Single particle conductivity was found to be higher than powder conductivity in general. The contact resistance between particles should be addressed for electrode optimization.

Composite electrode made of 0%, 1% and 3% carbon coated Li1+xNi1/3Co1/3Mn1/3O2 (NCM) was intensively investigated. Interfacial resistance was found to be dominant for the composite electrode using aluminum substrate.

Nano electrical imaging was carried out on composite electrode to better understand the conductive network. It was found that the full utilization of conductive carbon additives is necessary to reduce the content of carbon and improve conductivity.


Impact of Electrode Electronic Conductivity– Impedance Simulation of Gen 3 (NCM) Positive Electrode 5C HPPC

>0.01 (ohm cm)-1: electronic conductivity is much greater than the ionic conductivity and does not impact electrode impedance

0.001-0.01 (ohm cm)-1: electronic conductivity is comparable to the ionic conductivity

<0.001 (ohm cm)-1: electronic conductivity is much less than the ionic conductivity and significantly impacts electrode impedance

18

20

22

24

26

28

30

0.0001 0.001 0.01 0.1 1

Electrode Electronic Conductivity, (ohm cm)-1

Posi

tive

Elec

trod

e A

SI10

s, oh

m c

m2 low

conductivity

medium conductivity

high conductivity

Together with the electrolyte conductivity, the composition of the conductive additive should be tailored to meet the power and energy requirements of lithium ion batteries.

From Dennis Dees’ model (Argonne)


Electronic Conductivity Investigation

Single particle and powder conductivity measurements demonstrate that contact resistance is the key for conductivity of composite electrode.

In order to address the interfacial resistance between the particle, and current collector, carbon coated Li1+xNi1/3Co1/3Mn1/3O2 has been studied.

Pressure

Pow

der c

ondu

ctiv

itycurrent

resistance

Schematic diagram of powder conductivity measurement

apparatus

Cu

HDPE

PVDF film

PVDF

Single particle conductivity Powder conductivity Binder conductivity

NCAPart5-13

1

4 32

Single particle conductivity by Nano-probe SEM

pristine

> >


Effects of Carbon Coating on Morphology of Li1+xNi1/3Co1/3Mn1/3O2 (NCM)

0 200 400 600 800

97.0

97.5

98.0

98.5

99.0

99.5

100.0

Wei

ght l

oss,

%

Temperature, oC

NCM NCM2-1 NCM2-2 NCM1-1 NCM1-2

Carbon coated NCM10oC/min250 ml/min air

y = 0.7264x + 0.5514

0

0.5

1

1.5

2

2.5

3

0 1 2 3Carbon, %

BE

T, m

2/g

Series1

Linear (Series1)

y = 1E-05e2.0855x

R2 = 0.997

0.00001

0.0001

0.001

0.01

0.1

0 1 2 3 4

Carbon, wt.%

Con

duct

ivity

, S/c

m

TGA

pristine

3wt% carbon

Conductivity

BETpristine

3% carbon

1% carbon

The powders are subjected to a centrifugal force and are securely pressed against the inner wall of rotating casing.

The powders are further subjected to various mechanical forces, such as compression and shear forces, as they pass through a narrow gap between the casing wall and the press head.

As a result, smaller guest particles are dispersed and bonded onto the surface of larger host particles without using binder of any kind.

SEM

NCM

NCM1

NCM3

Hosokawa


Cross Section of NCM Electrode

Continuous carbon pathway was observed for NCM0 with 4% carbon additive.

But, little or longer pathway for NCM3 electrode with only 1wt% additional carbon additives.

NCM0-24 NCM3-04Al Al

surface surface

Cross section Cross section

NCM/CB/PVDF84/ 4 /4

NCM3(w/3%cb)/CB/PVDF87/ 1 /4


Electrode Conductivity by 4 Probe Method

Electrode composition*:– Active: 84%, – SFG-6: 4% – Carbon: 4% (*including coated

carbon); – PVDF: 8%

Aluminum

0

0.02

0.04

0.06

0.08

Before 40% 30%

R, o

hm

NCMNCM 3%

Polyester

0

100

200

300

400

500

600

Before 40% 30%

R, o

hm

NCM PENCM 3% PE

The resistance of the NCM3 electrode with 1wt% additional carbon on aluminum foil shows less resistance before calendering. Resistances of both electrodes NCM0 and NCM3 on aluminum decreases after calendering.

For the electrode on polyester substrate, the sheet resistance of the NCM3 electrode is higher. The electrode sheet resistance increases after calendering for both NCM0 and NCM3.

Therefore, interfacial resistance is dominant for the composite electrode using aluminum substrate. The contact resistance between the particles and substrate was small for carbon coated sample.

substrateinterfacesample

iV


4 Probe Modeling of Composite Electrode

The conductivity calculated from modeling is consistent to the 4 probe measurement.

The validated model will be used to determine the interfacial resistance between the composite layer and substrate.

0.0

0.1

0.2

0.3

65 70 75 80 85Thickness, µm

Con

duct

ivity

, S/c

m

4probemodel

i1

V1

V2 i2

Errlim = 0.00001Rcontact = 0.5 ohm-cm2Rinterface = 10000 ohm-cm2conductivity = 0.221 S/cm


Nano-Electrical Imaging of Electrode using AFM

3% carbon coated NCM + 4% carbon + 7% PVDF

Higher current indicates higher conductivity.

There are two distinct regions in the image: isolated blue rocky-like (NCM) and continuous patches (CB + PVDF).

The conductivity various with CB/PVDF region, which should be further studied.

Current: purple/pink < green < yellow < red

AFM by Bruker (Veeco)


Future Plans

The electronic conductivity of composite electrode made of carbon coated NCM was intensively investigated.

– The composite electrode with carbon coated particles has better interfacial conductivity between composite layer and substrate, but higher sheet resistance compared with uncoated particles.

– The electrode with uncoated particles has lower interfacial conductivity but higher conductivity within the composite sheet.

– The 4 probe model was validated and the interfacial resistance will be studied.

Nano electrical image indicates that the carbon additive is not fully utilized to form the conductive matrix.

Carbon coating impact on the cathode performance will be continued.

– The amount of coating, additional carbon additive, and binder effect will be investigated.

– This 4 probe modeling will be utilized to study the interfacial resistance.

Electrode optimization on electronic conductivity will be address through

– Percolation theory

– Optimization of composite electrode conductivity

Summary


Contributors and Acknowledgments

Argonne National Laboratory Nathan Liu Huiming Wu Bryant Polzin Jack Vaughey Daniel Abraham Khalil Amine Kevin Gallagher Gary Henriksen Electron Microscopy Center (EMC) Center for Nanoscale Materials (CNM)

ConocoPhillips Toda Kogyo Hitachi Chemicals, Japan Solvay Daikin Inc., Japan Hirose Paper North America, GA Somer Thin Strip, CT Pred Materials International, Inc., NY Hosokawa Micron Corporation, NJ Leica Microsystems Bruker (Veeco)

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

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