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STABILIZED SPINEL AND POLYANION CATHODES ARUMUGAM MANTHIRAM Electrochemical Energy Laboratory (ECEL) Materials Science and Engineering Program The University of Texas at Austin May 10, 2011 Project ID #: ES051 This presentation does not contain any proprietary, confidential, or otherwise restricted information

STABILIZED SPINEL AND POLYANION CATHODESRELEVANCE • To develop high-performance spinel and polyanion cathodes for lithium-ion batteries and a fundamental understanding of their structure-composition-performance

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Page 1: STABILIZED SPINEL AND POLYANION CATHODESRELEVANCE • To develop high-performance spinel and polyanion cathodes for lithium-ion batteries and a fundamental understanding of their structure-composition-performance

STABILIZED SPINEL AND POLYANION CATHODES

ARUMUGAM MANTHIRAMElectrochemical Energy Laboratory (ECEL)Materials Science and Engineering Program

The University of Texas at Austin

May 10, 2011

Project ID #: ES051This presentation does not contain any proprietary, confidential, or otherwise restricted information

Page 2: STABILIZED SPINEL AND POLYANION CATHODESRELEVANCE • To develop high-performance spinel and polyanion cathodes for lithium-ion batteries and a fundamental understanding of their structure-composition-performance

OVERVIEW

Timeline

• Project start date: June 2010• Project end date: May 2012• 75 % complete

Budget

• Total project funding- DOE: $520K

• Funding for FY10- $260K

• Funding for FY11- $260K

Barriers

• Barriers - Cost- Cycle life- Energy and power densities

• Targets- Long cycle life for 4 V and 5 V spinel cathodes

- Low manufacturing cost for polyanion cathodes

- Increased energy and power with spinel and polyanion cathodes

Page 3: STABILIZED SPINEL AND POLYANION CATHODESRELEVANCE • To develop high-performance spinel and polyanion cathodes for lithium-ion batteries and a fundamental understanding of their structure-composition-performance

RELEVANCE

• To develop high-performance spinel and polyanion cathodes for lithium-ion batteries and a fundamental understanding of their structure-composition-performance relationships

- To develop 5 V spinel oxide compositions with controlled morphology and optimum cationic substitutions that can maximize the tap density and electrochemical performance

- To develop a fundamental understanding of the factors that control the electrochemical performance and safety of cation- and anion-substituted stabilized 4 V spinel manganese oxide compositions

- To develop novel low-cost synthesis processes for phosphate and silicate cathodes

Page 4: STABILIZED SPINEL AND POLYANION CATHODESRELEVANCE • To develop high-performance spinel and polyanion cathodes for lithium-ion batteries and a fundamental understanding of their structure-composition-performance

MILESTONES

Month/Year Milestone

September 2010 Polyanion-containing cathodes with controlled nanomorphologies

March 2011 Understanding the self-surface segregation of cations in high-voltage spinel cathodes

September 2011 Development of novel synthesis approaches for high-capacity nanostructured silicate and phosphate cathodes

Page 5: STABILIZED SPINEL AND POLYANION CATHODESRELEVANCE • To develop high-performance spinel and polyanion cathodes for lithium-ion batteries and a fundamental understanding of their structure-composition-performance

APPROACH / STRATEGY

• Develop a firm understanding of the factors controlling the electrochemical performances of cathode materials and utilize the understanding to develop high-performance cathodes for vehicle batteries

- Cationic and anionic substitutions to obtain stabilized 4 V spinel cathodes- Effect of cationic and anionic substitution on thermal stability of 4 V spinel cathodes- Cationic substitutions in 5 V spinels to stabilize the disordered spinel structure- Novel synthesis approaches for polyanion-containing cathodes including nano-olivines that can lower manufacturing cost with improved performance

- Solid-state, high-energy ball milling, and solution-based synthesis approaches- Advanced chemical and structural characterizations- In-depth electrochemical evaluation including impedance analysis- Understanding of the structure-property-performance relationships

Page 6: STABILIZED SPINEL AND POLYANION CATHODESRELEVANCE • To develop high-performance spinel and polyanion cathodes for lithium-ion batteries and a fundamental understanding of their structure-composition-performance

• The influence of cationic substitutions on the bulk and surface structures and electrochemical performances of 5 V spinel cathodes has been identified

- cationic substitutions stabilize the disordered spinel structure, facilitate segregation of certain cations to the surface, and thereby improve significantly the electrochemical performances (cycle life and rate capability)

• Precursors with unique morphologies have been synthesized by novel synthesis approaches to maximize the tap density and performance of 5 V spinels

• The factors that influence the cycle life and safety of 4 V spinels have been identified; oxyfluorides offer better safety than the oxide counterparts

• Substitution of small amounts of Fe significantly improves the electrochemical performances of both LiMnPO4 and LiCoPO4 due to surface segregation

• The substitution of VO for Fe in LiFe1-x(VO)xPO4 has been found to create vacancies in the Fe sites; the LiFe1-x(VO)xPO4 phases formed by the microwave-assisted process are metastable and disproportionate at high temperatures

TECHNICAL ACCOMPLISHMENTS AND PROGRESS

Page 7: STABILIZED SPINEL AND POLYANION CATHODESRELEVANCE • To develop high-performance spinel and polyanion cathodes for lithium-ion batteries and a fundamental understanding of their structure-composition-performance

INFLUENCE OF CATIONIC SUBSTITUTIONS IN 5 V SPINEL

0 10 20 30 40 50 60 70 80 90 100

40

60

80

100

120

140

Ca

paci

ty (m

Ah/g

)

Cycle number

LiMn1.5Ni0.5O4

LiMn1.5Ni0.42Cr0.08O4

LiMn1.5Ni0.42Fe0.08O4

LiMn1.5Ni0.42Ga0.08O4

25 oC

0 10 20 30 40 50 60 70 80 90 10020

40

60

80

100

LiMn1.5Ni0.5O4

LiMn1.5Ni0.42Cr0.08O4

LiMn1.5Ni0.42Fe0.08O4

LiMn1.5Ni0.42Ga0.08O4

Coul

ombi

c ef

ficie

ncy

(%)

Cycle number

25 oC

0 2 4 6 8 100

20

40

60

80

100

LiMn1.5Ni0.5O4

LiMn1.5Ni0.42Cr0.08O4

LiMn1.5Ni0.42Fe0.08O4

LiMn1.5Ni0.42Ga0.08O4

Norm

aliz

ed d

isch

arge

cap

acity

(%)

C rate

0 10 20 30 40 50 60 70 80 90 100

40

60

80

100

120

140 55 oC

Capa

city

(mAh

/g)

Cycle number

LiMn1.5Ni0.5O4

LiMn1.5Ni0.42Fe0.08O4

LiMn1.5Ni0.42Ga0.08O4

Page 8: STABILIZED SPINEL AND POLYANION CATHODESRELEVANCE • To develop high-performance spinel and polyanion cathodes for lithium-ion batteries and a fundamental understanding of their structure-composition-performance

• Fe segregates to the surface during the synthesis and cooling process, which is consistent with our earlier XPS data

• Self-surface segregation is an attractive strategy to develop a robust electrode-electrolyte interface with the high-voltage cathodes

SELF-SURFACE SEGREGATION IN 5 V SPINELS

0 10 20 30 40 500

100

200

1000

10000

54Fe+

Ni+

Mn+

LiMn1.5Ni0.5O4

Inte

nsity

(cou

nts)

Sputtering time (s)0 10 20 30 40 50

0

100

200

1000

10000

LiMn1.5Ni0.42Fe0.08O4

Inte

nsity

(cou

nts)

Sputtering time (s)

Mn+

Ni+

54Fe+

Time-of-flight – secondary ion mass spectroscopy (TOF-SIMS)

Page 9: STABILIZED SPINEL AND POLYANION CATHODESRELEVANCE • To develop high-performance spinel and polyanion cathodes for lithium-ion batteries and a fundamental understanding of their structure-composition-performance

MORPHOLOGY CONTROL OF 5 V SPINEL CATHODES

• Morphology could be controlled with different precipitating agents and additives such as AOT, CTAB, or (NH4)2SO4

oxalate, AOT, polyhedral

carbonate, CTABcubic

carbonate, (NH4)2SO4spherical

•Microcubic precursor is preheated at 450 °C, followed by mixing with LiOH and firing at 900 °C for 12 h•Precursor morphology is retained in the final spinel sample•High tap density: 2.0 g/cm3

LiMn1.5Ni0.5O4 spinel

5 μm 10μm

10μm

200 μm 10 μm

Page 10: STABILIZED SPINEL AND POLYANION CATHODESRELEVANCE • To develop high-performance spinel and polyanion cathodes for lithium-ion batteries and a fundamental understanding of their structure-composition-performance

5 V SPINEL WITH MICRO-CUBIC MORPHOLOGY

•The 5 V spinel was obtained from the single-phase micro-cubic carbonate precursor•The 5 V spinel exhibits excellent cyclability without any capacity fade compared to a commercial 5 V spinel sample

0 5 10 15 20 25 30 3520

40

60

80

100

120

140

Disch

arge C

apac

ity (m

Ah/g)

Cycle Numbers

LiMn1.5Ni0.5O4: MicrocubicLiMn1.5Ni0.5O4: Commerical

0 20 40 60 80 100 120 140

3.5

4.0

4.5

5.0

Volta

ge (V

)

Capacity (mAh/g)

First Charge First Discharge

10 20 30 40 50 60 70 80

carbonate precursor

heated at 450 oC

Inte

nsity

(a.u

.)

2θ (Degree)

LiMn1.5Ni0.5O4

Page 11: STABILIZED SPINEL AND POLYANION CATHODESRELEVANCE • To develop high-performance spinel and polyanion cathodes for lithium-ion batteries and a fundamental understanding of their structure-composition-performance

5µm

10µm

5µm

5µm

20µm

5µm

EFFECTS OF REACTION TIME AND CATIONIC SUBSTITUTIONS

Mn0.75Ni0.25CO3 LiMn1.5Ni0.5O4

3 hour reaction time

6 hour reaction time

12 hour reaction time

Mn0.75Ni0.25-zFezCO312 hours, pH 7.9 +/- 0.05

Mn0.75Ni0.25CO3

Mn0.75Ni0.225Fe0.025CO3

Mn0.75Ni0.2Fe0.05CO3

•Morphology changes with reaction time; 12 h gives spherical morphology•Fe(OH)2 formed due to hydrolysis

with Fe substitution, which becomes FeOOH at 120 oC

5µm

10µm

10µm

20 30 40 50Cu Kα 2θ(degree)

Inte

nsity

(arb

itrar

y un

it)

FeO(OH)Mn0.75Ni0.2Fe0.05CO3

LixNi1-xOLiMn1.5Ni0.5O4

Page 12: STABILIZED SPINEL AND POLYANION CATHODESRELEVANCE • To develop high-performance spinel and polyanion cathodes for lithium-ion batteries and a fundamental understanding of their structure-composition-performance

0.0 0.1 0.2 0.30

5

10

15

20

Capa

city

fade

in 5

0 cy

cles

(%)

x in Li1.1Mn1.8Al0.1O4-xFx

3.65 3.60 3.55 3.50Mn valence

0.0 0.1 0.2 0.3 0.40

5

10

15

20

Capa

city

fade

in 5

0 cy

cles

(%)

x in Li1.1Mn1.8Fe0.1O4-xFx

3.65 3.60 3.55 3.50 3.45Mn valence

0.0 0.1 0.2 0.30

5

10

15

20

Capa

city

fade

in 5

0 cy

cles

(%)

x in Li1.1Mn1.8Cr0.1O4-xFx

3.65 3.60 3.55 3.50Mn valence

•Capacity fade increases drastically above a fluorine content of 0.2 or below a Mn valence of ~ 3.55+

•This is due to an increasing amount of Mn3+

and the consequent Mn dissolution and dynamic Jahn-Teller distortion

•The initial Mn valence should be maintained above ~ 3.6+ to realize acceptable performance

CYCLABILITY OF CATION-SUBSTITUTED 4 V OXYFLUORIDE SPINELS

Page 13: STABILIZED SPINEL AND POLYANION CATHODESRELEVANCE • To develop high-performance spinel and polyanion cathodes for lithium-ion batteries and a fundamental understanding of their structure-composition-performance

• The capacity fade in 4 V oxyfluoride spinels- increases with decreasing Mn valence

below ~ 3.6+- decreases with increasing electronegativity

of the substituted cations M from Ti to Ni- decreases with decreasing M-O bond

dissociation energy

3.5 3.6 3.7 3.8 3.9 4.0 4.10

5

10

15

20

Li1.1Mn1.8Al0.1O4-xFx

Li1.1Mn1.8Cr0.1O4-xFx

Li1.1Mn1.8Fe0.1O4-xFx

Li1.1Mn1.8Ni0.1O4-xFx

Li1.1Mn1.8Ti0.1O4-xFx

LiMn2-x-yLixCoyO4-zFz

Capa

city

fade

in 5

0 cy

cles

(%)

Mn valence

0

4

8

12

1.5

1.6

1.7

1.8

1.9

Ti Al Cr Fe Co Ni300

400

500

600

700

Ave

rage

ca

paci

ty fa

de (%

)

Elec

tron

egat

ivity

Bon

d di

ssoc

iatio

n en

ergy

(kJ/

mol

)

UNDERSTANDING THE CAPACITY FADE IN 4 V OXYFLUORIDE SPINELS

Page 14: STABILIZED SPINEL AND POLYANION CATHODESRELEVANCE • To develop high-performance spinel and polyanion cathodes for lithium-ion batteries and a fundamental understanding of their structure-composition-performance

THERMAL STABILITY OF 4 V SPINEL CATHODESDSC Plots of Ni-substituted cathodes in the

charged state, wetted with electrolyte

• Samples with lower lithium content in the charged state show better thermal stability

• Metal-oxygen bond strength affects the thermal stability significantly

• Similar results were obtained for Al- and Li-doped samples

Page 15: STABILIZED SPINEL AND POLYANION CATHODESRELEVANCE • To develop high-performance spinel and polyanion cathodes for lithium-ion batteries and a fundamental understanding of their structure-composition-performance

OLIVINE SOLID SOLUTIONS

LiMn1-yFeyPO4

• Substitution of Fe for Mn or Co improves the electrochemical activity

LiCo1-yFeyPO4

Page 16: STABILIZED SPINEL AND POLYANION CATHODESRELEVANCE • To develop high-performance spinel and polyanion cathodes for lithium-ion batteries and a fundamental understanding of their structure-composition-performance

MICROWAVE-SOLVOTHERMAL (MW-ST) SYNTHESIS OF LiFe1-x(VO)xPO4

Compound V (Å3) Li/P V/P Fe/P

LiFePO4 289.85 1.00 ----- 0.99

LiFe0.95(VO)0.05PO4 287.82 0.99 0.05 0.96

LiFe0.90(VO)0.10PO4 287.29 0.97 0.10 0.86

LiFe0.85(VO)0.15PO4 286.40 1.02 0.16 0.77

LiFe0.75(VO)0.25PO4 285.21 0.99 0.24 0.70

• Substitution of a larger (VO)2+ for a smaller Fe2+ should increase the unit cell volume, but exactly the opposite is found due to the formation of Fe vacancies as indicated by a lower Fe/P ratio in the sample in the ICP analysis and Fe3O4 impurity that could be removed with a magnetic bar

• Fe vacancies are formed to accommodate the larger (VO)2+ ions

• Formation of Fe vacancies and the corresponding oxidation of Fe2+ to Fe3+

decrease the unit cell volume

Page 17: STABILIZED SPINEL AND POLYANION CATHODESRELEVANCE • To develop high-performance spinel and polyanion cathodes for lithium-ion batteries and a fundamental understanding of their structure-composition-performance

THERMAL STABILITY OF LiFe1-x(VO)xPO4

• The MW-ST LiFe1-x(VO)xPO4 samples are metastable and cannot not be made by conventional high-temperature methods- With increasing heating temperature in 5 %

H2 – 95 % Ar, the vanadium activity changes from that of (VO)2+/3+ in LiVOPO4 to that of V3+/4+/5+ in Li3V2(PO4)3

- LiFe0.85(VO)0.15PO4 synthesized by conventional heating shows only V3+/4+/5+

activity without any (VO)2+/3+ activity, indicating the instability of LiFe0.85(VO)0.15PO4

Page 18: STABILIZED SPINEL AND POLYANION CATHODESRELEVANCE • To develop high-performance spinel and polyanion cathodes for lithium-ion batteries and a fundamental understanding of their structure-composition-performance

COLLABORATION AND COORDINATION WITH OTHER INSTITUTIONS

• National Renewable Energy Laboratory – Dr. Anne Dillon- ALD coating of Al2O3 on 5 V spinel cathodes

• University of Rhode Island – Professor Brett Lucht - Investigation of SEI layer formation with stabilized 5 V spinel cathodes

• Pacific Northwest National Laboratory – Dr. Jiguang (Jason) Zhang- Discussion and coordination of results on 5 V spinel cathodes

• Lawrence Berkeley National Laboratory – Dr. Jordi Cabana Jiménez- Discussion and coordination of results on 5 V spinel cathodes

Page 19: STABILIZED SPINEL AND POLYANION CATHODESRELEVANCE • To develop high-performance spinel and polyanion cathodes for lithium-ion batteries and a fundamental understanding of their structure-composition-performance

PROPOSED FUTURE WORK

• Continue to identify the factors that influence the electrochemical performances of the 5 V spinel cathodes, e.g., role of ordered vs. disordered spinel structure, segregation of cations to the surface, synthesis temperature, and morphology

• Extend the morphological-control synthesis approach pursued for LiMn1.5Ni0.5O4

spinel to other cation-substituted LiMn1.5Ni0.5-yMyO4 (M = Cr, Fe, and Ga)

• Recognizing that the substitution of a small amount of Fe improves the performances of LiMnPO4 and LiCoPO4, explore whether surface segregation of Fe plays a role in improving the performance of LiM1-xFexPO4 (M = Mn and Co)

• Following our earlier work, explore the microwave-assisted solvothermal synthesis approaches to obtain Li2Fe1-xMxSiO4 (M = Mn, Co, and Ni) silicate that have the potential to reversibly insert/extract two lithium per transition metal ion

• Explore the microwave-assisted solvothermal synthesis approach to obtain nanostructured NASICON-related Li3V2(PO4)3 and Li9V3(P2O7)3(PO4)2 cathodes that has the potential to extract more than one lithium per transition metal ion

Page 20: STABILIZED SPINEL AND POLYANION CATHODESRELEVANCE • To develop high-performance spinel and polyanion cathodes for lithium-ion batteries and a fundamental understanding of their structure-composition-performance

5 V Spinel LiMn1.5Ni0.5O4

• Cationic substitutions stabilize the disordered spinel structure, eliminate the Ni1-xLixO impurity, and improve significantly the electrochemical performance

• Certain cations like Fe3+ segregate to the surface during the synthesis process of LiMn1.5Ni0.5-xFexO4 and provide a robust interface with the electrolyte

• Controlled synthesis with unique morphologies offer high tap density

4 V Spinel LiMn2-yMyO4-zFz

• The Mn valence has to be above ~ 3.6 + to offer acceptable cycle life

• Electronegativity of M and M-O bond energies play a role in the capacity fade

• The oxyfluoride spinels offer better safety than the oxide counterparts

Polyanion cathodes

• Substitution of Fe improves the performances of LiMnPO4 and LiCoPO4

• The substitution of VO for Fe in LiFe1-x(VO)xPO4 is accompanied by the formation Fe vacancies and oxidation of Fe2+ to Fe3+

• The LiFe1-x(VO)xPO4 phases are metastable and decompose at high temps.

SUMMARY