Jason ZhangPacific Northwest National Laboratory

Richland, WA

Presentation in METS 2012Taipei, Taiwan

Nov. 11-14, 20121

HIGH ENERGY BATTERIES FOR ELECTRIC VEHICLE APPLICATIONS

1. Nano-structured Materials for Li-ion batteries 1.1 High capacity anode1.2 High voltage cathode

2. Energy Storage beyond Li-ions2.1 Highly Stable Li-S batteries2.2 High Capacity Li-air batteries2.3 Li-Metal Batteries

3. Summary

2

Outline

Tarascon & Armand, Nature 2001 414, 359-367

3

1. Nano-structured Electrodes for Li-Ion Batteries

TiO2

Si

LiNi0.5Mn1.5O4

LiMnPO4

4

1.1 High Capacity Anodes Self Assembly of Nano-transition Metal

Oxide/Graphene Composite

• The self-assembled structure composed of ordered “super-lattice” nanocomposite with alternating layers of graphene nanosheets and metal oxides

• Direct manufacturing of electrodes and batteries without binders and other additives.

Nanosynthesis: TiO2, SnO2, and other cathode materials

Self-assembly with graphene

5

High Performance Nano-TiO2/Graphene Composite

C/5 1C

• Best rate capability reported on anatase TiO2 with only 2.5wt% graphene.

• Excellent cycling stability: ~ 170 mAh/g at 1C (PHEV constant output).

Conductive Rigid Skeleton Supported Silicon as High-Performance Li-ion Battery Anodes

• Use conductive B4C as nano-/micro- millers to synthesize nano Si (< 10 nm ).• Use rigid skeleton to support in-situ generated nano-Si.• Use conductive carbon to coat the rigid skeleton supported silicon to form

Si/Core/graphite (SCG) which can improve the structural integrity and conductivity of silicon anode.

a)

Si

+ Graphite

GraphiteSi

B4C

b) c)

6

High energy ball milling

Planetary ball milling

B4C

• The ratio of Si, Core material and graphite are important to the electrochemical performance. Si:Core:graphite = 4:3:3 is the optimized ratio.

• Ball milling time is also important to the electrochemical performance. 8 hr milling is good for HEBM and PBM.

Effects of Composition and Synthesis Condition on the Electrochemical Performances of Si Anodes

0 25 50 750

200

400

600

800

1000

1200

Dis

char

ge c

apac

ity (m

Ah•

g-1)

Cycle index

SBG415 SBG433 SBG451

Both HEBM and PBM time fixed at 8 hours

a)

0 10 20 300

200

400

600

800

1000

1200

Dis

char

ge c

apac

ity (m

Ah•

g-1)

Cycle Index

HEBM time 4 hours 8 hours 12 hours

PBM time fixed at 8 hours

b)

·

0 10 20 300

200

400

600

800

1000

1200

Dis

char

ge c

apac

ity (m

Ah•

g-1)

Cycle Index

PBM time 4 hours 8 hours 12 hours

HEBM time fixed at 8 hours

c)

0 10 20 300

200

400

600

800

1000

1200

Dis

char

ge c

apac

ity (m

Ah•

g-1)

Cycle Index

HEBM time 4 hours 8 hours 12 hours

PBM time fixed at 8 hours

b)

0 10 20 300

200

400

600

800

1000

1200

Dis

char

ge c

apac

ity (m

Ah•

g-1)

Cycle Index

PBM time 4 hours 8 hours 12 hours

HEBM time fixed at 8 hours

c)

7

0 25 50 750

200

400

600

800

1000

1200

Dis

char

ge c

apac

ity (m

Ah•

g-1)

Cycle index

SCG415 SCG433 SCG451

Both HEBM and PBM time fixed at 8 hours

a)

8

1.2 High Voltage CathodesLiMnPO4 Synthesized in Molten Hydrocarbon Has

Preferred Growth Orientation

• Pure phase of LiMnPO4 was obtained after 550ºC calcination.

• As-prepared LiMnPO4 nanoplates are well dispersed without stacking.

• LiMnPO4 nanoplates consists of a porous structure formed by self-assembled nanorods aligned in a

preferred orientation with high specific surface area of 37.3m2/g.

Oleic acid was used as a surfactant and paraffin acts as a non-polar solvent that facilitate thermodynamically preferred crystal growth without agglomeration.

9

High Performance LiMnPO4 Synthesized in Molten Hydrocarbon

• Specific capacity of 168mAh/g was achieved which is close to the theoretical capacity of LiMnPO4.

• Flat voltage plateau at ~ 4.1 V indicates the phase transition between LiMnPO4 and MnPO4. • At 1C and 2C rate (PHEV constant output) capacity retention is 120 mAh/g and 100 mAh/g, respectively.• Ragone plot indicates that the discharge power density is close in LiMnPO4 and LiFePO4 when fully charged at C/25; At low power (< 30 W/kg), energy density of LiMnPO4 becomes comparable or higher than LiFePO4.

constant charge rate at C/25constant charge rate at C/25

101

102

103

104

8 200 400 600

LiFePO4

LiMnPO4

(Charge C/25)

Power

Den

sity

(W/K

g)

Energy Density (Wh/Kg)

10

a b c

d e f

g h i

Ann

eale

dLi

Ni 0.

5Mn 1

.5

O4

Ann

eale

d Li

Ni 0.

45M

n 1.5C

r 0.0

5

O4

LiN

i 0.5M

n 1.5

O4

• The relative content between ordered and disordered phase can be tuned by changing synthesis condition.

Doping significantly improve the performance of high voltage spinel

1.2 High Voltage Cathode: LiNi0.45Cr0.05Mn1.5O4

Cr-substituted spinel

Cr-substituted spinel

• Cr-substituted spinel LiNi0.45Cr0.05Mn1.5O4 exhibit stable cycling and excellent rate performance.

11

Conventional Electrolytes are Stable up to 5.2 V

0

20

40

60

80

100

120

140

160

0 100 200 300 400 500

Cycle number

Dis

char

ge c

apac

ity (m

Ah/g

)

4.9 V5.0 V5.1 V5.2 V5.3 V (a) EC-DMC

0

20

40

60

80

100

120

140

160

0 100 200 300 400 500

Cycle numberDi

scha

rge

capa

city

(mAh

/g)

4.9 V5.0 V5.1 V5.2 V5.3 V

(b) EC-EMC

0

20

40

60

80

100

120

140

160

0 100 200 300 400 500

Cycle number

Disc

harg

e ca

paci

ty (m

Ah/g

)

4.9 V5.0 V5.1 V5.2 V5.3 V

(c) EC-DEC

0

20

40

60

80

100

120

140

160

180

0 10 20 30 40 50 60 70

Cycle number

Dis

char

ge c

apac

ity (m

Ah/g

)

EC-DMCEC-EMCEC-DEC4.9 V

C/10

C/2

1C

2C

5C

10C

1C

0

20

40

60

80

100

120

140

160

180

0 10 20 30 40 50 60 70

Cycle number

Dis

char

ge c

apac

ity (m

Ah/

g)

EC-DMCEC-EMCEC-DEC

C/10

C/2

1C

2C

5C

10C

1C

5.1 V

0

20

40

60

80

100

120

140

160

180

0 10 20 30 40 50 60 70

Cycle number

Dis

char

ge c

apac

ity (m

Ah/g

)

EC-DMCEC-EMCEC-DEC5.3 V

C/10

C/2

1C

2C

5C

10C

1C

• Cutoff voltage ≤ 5.2 V: Very similar long cycling performance for the three carbonate mixtures.• Cutoff voltage = 5.3 V: EC-DMC is still stable but EC-DEC degrades fast.• Rate capability: EC-DMC and EC-EMC is similarly but EC-DEC is poorer.

Lead

-acid

Ni-cad

mium

Ni-zinc

NiH2

NiMH

Zebra

Silver z

inc NaS

LiCoO2 /g

raph

ite

LiCoO

2/Li

Li-S

Li-O2,

Best e

stimate

Li-O2, a

queo

us

Li-O2,

non-a

queou

s0

500

1000

1500

2000

2500

3000

3500

4000

Practical specific energy based on state of the art cells

Theoreticall specific energy based on active components

Spe

cific

Ene

rgy

(Wh/

kg)

Li-Metal Batteries

12

2. Energy Storage beyond Li-ionsComparison of Specific Energy of Various Batteries

13

2.1 Highly Stable Li-S BatteriesPotential: 3-4x improvement over Li-ionBarrier: Li2S deposition on Li metal

14

Optimization of mesoporous carbon structures

(a) MC. (b) MC with pores completely filled

with sulfur. (c)MC with pores partially filled

with sulfur.

15

Self-breathing Conductive Polymer to Encapsulate Sulfur

(c)

Discharge

ChargeIn-situ

vulcanization Polymer + SulfurPolymer Polymer + Li Sulfide

H

S S

N

S S

N

S SS S

S S

S SS S

N

SS

N

S S

N

S S

NS SS S

S S

S S

S S

N

S S

N

H

H

H

H

y 1-y

H

H

H

polymer hollow nanowire S/polymer composite Composite discharged to 1V Composite recharged to 3V

At C/10, initial discharge capacity is 755 mAh/g with an activation process in the following cycles.

Even after 500 cycles at 1C the capacity retention reaches 76%.

0 200 400 600 8001.0

1.5

2.0

2.5

3.0(b)

1st

Capacity / mAh g-1

Volta

ge /

V vs

. Li/L

i+

0 20 40 60 80 1000

200

400

600

800

1000(c)

0.1 C 0.5 C 1 CC

apac

ity /

mA

h g-1

Cycle number / n

2.2. High Capacity Li-Air Batteries

2Li++ 2e− + O2 ↔ Li2O2 (2.96 V) Alkaline: O2 + 2H2O + 4e−↔ 4OH− (3.43 V) Acid: O2+ 4e− + 4H+ ↔ 2H2O (4.26 V)

Aqueous Li-air Batteries Non-Aqueous Li-air Batteries

16 16

17

0

0.4

0.8

1.2

1.6

2

2.4

2.8

3.2

3.6

0 0.2 0.4 0.6 0.8 1 1.2 1.4

Volta

ge (V

)

Cell capacity (Ah)

Operated in ambient air (~20% RH) for 33 daysTotal weight of the complete battery: 8.387 gSpecific energy: 362 Wh/kg

2340 mAh/g carbon

0.8 mil polymer membrane

Metal mesh

0.7 mm KB carbon electrode

0.5 mm Li foil1 mil separator with binding layer

Cu mesh

+-

Footprint: 4.6 cm x 4.6 cm; thickness = 3.8 mm

Zhang et al, J. Power Sources 195:4332–4337 (2010).

High Capacity Primary Li-air Batteries

18

Hierarchically Porous Graphene as a Lithium-Air Battery Electrode

a and b, SEM images of as-prepared graphene-based air electrodes

c and d, Discharged air electrode using FGS with C/O = 14 and C/O = 100, respectively.

e, TEM image of discharged air electrode.

f, Selected area electron diffraction pattern (SAED) of the particles: Li2O2.

Xiao et al. Nano Lett., 2011, 11 (11), pp 5071–5078.

19

Graphene as a Lithium-Air Battery Electrode Record Capacity of 15,000 mAh/g

20

• Rechargeable Li-metal batteries are considered the “holy grail” of energy storage systems due to the high energy density.

• However, Li dendrite growth in these batteries has prevented their practical applications inspect of intensive works in this field during the last 40 years.

Dendrite-free Li metal deposition is needed for rechargeable Li-metal batteries, Li-S batteries, Li-air batteries.

Classical Li dendrite growth(Chianelli, Exxon, 1976)

GM estimate on HE NMC/Li metal system: 540 Wh/kg, 1050 Wh/L in cell level (2012)

2.3 Li-Metal Batteries

21

20 µm

a

20 µm

b

20 µm

c

20 µm

d

20 µm

e

Effect of CsPF6 Additive on The Morphology of Li Deposition

• Control electrolyte: 1 M LiPF6 in PC. • CsPF6 concentration in the electrolyte: (a) 0 M, (b) 0.001 M, (c) 0.005 M,

(d) 0.01 M, and (e) 0.05 M. Cs+ additive can effectively suppress Li dendrite growth.

22

Effect of Current Density on Li Deposition

20 µm

b

20 µm

a

20 µm

d

20 µm

c

• Electrolyte: 1 M LiPF6 in PC with 0.05 M CsPF6 as additive. • Current density (mA cm-2): (a) 0.1, (b) 0.2, (c) 0.5, and (d) 1.0.

SHES mechanism is effective at different current densities.

23

Morphology Changes During Long Term Cycling of Li Electrode in Li/LTO Cells

20 µm

b

20 µm

a

Surface morphologies of Li electrodes after 100 cycles in coin cells of Li|Li4Ti5O12 system containing electrolytes without (a) and with (b) Cs+-additive.

SHES mechanism is effective during long term cycling.

24

Columbic efficiency: 99.97% Cycling stability: Only 3.3% capacity fade in 660 cycles

Excellent Long Term Stability of Li-Metal BatteriesUsing Cs+ Additive

0 100 200 300 400 500 600 7000

50

100

150

200

250

300

Dis

char

ge C

apac

ity (m

Ah/

g)

Cycle index

60

70

80

90

100

Cou

lom

bic

Effic

ienc

y (%

)

Cell: Li/Li4Ti5O12

1 M LiPF6 in PC with 0.05 M CsPF6

25

Summary1. Si electrode prepared by a cost effective method (ball

milling) 822 mAh/g and a capacity retention of ~ 94% in 100 cycles.

2. High voltage, highly stable cathode Retain more than 80% capacity after 500 cycles.

3. Highly stable Li-S batteries 650-800 mAh/g after 400 cycles.

4. High capacity Li-air batteries Li-air batteries operate in ambient air for 33 days with a specific energy of ~362 Wh/kg for the complete battery. Graphene based air electrode (~ 15,000 mAh/g).

5. Dendrite-Free Li-Metal Batteries Novel additives (Cs, Rb, etc.) based on the SHES mechanism can effectively

suppress Li dendrite growth on Li metal batteries. ~99.97% Coulombic efficiency and ~4.2% capacity fade in 610 cycles

for Li-metal batteries.

AcknowledgmentsTechnical Team:

Wu Xu, Jie Xiao, Xiaolin Li, Yuyan Shao, V. Viswanathan, Jianzhi Hu, Vijayakumar Murugesan, Silas A. Towne, Phillip Koech, Donghai Mei, Fei Ding, Zimin Nie, Yuliang Cao, Yufan Xiao, Eduard Nasybulin, Jian Zhang, Dehong Hu, Gordon L. Graff, and Jun Liu

Financial support: • DOE/EERE/Office of Vehicle Technology• Laboratory Directed R&D Program of PNNL