Development of Li-Air BatteriesDevelopment of Li Air Batteries

Jason Zhang

December 2010

OutlineOutline

1. Advantages and Challenges of Li-air Batteries

2. Development of Primary Li-air Batteries

3 Rechargeable Mechanism in Li-air Batteries3. Rechargeable Mechanism in Li-air Batteries

4. Summary

2

Challenges for Extremely High Energy Batteries: Li-ion batteries are currently among the most attractive technologies for

microelectronic, transportation and defense, but Li-S, and Li-air batteries have the potential to increase the specific energy density by orders of magnitudespotential to increase the specific energy density by orders of magnitudes

Technologies beyond Li-ion require significant improvement in electrode and electrolyte materials, cell design and fundamental understanding to solve the

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poor reversibility and reliability, low power and high cost problems.

1. Advantages and Challenges of Li-air Batteries

Nonaqueous Electrolyte Aqueous Electrolyte Based Li-air Batteries Based Li-air Batteries

Reaction 2Li + O2 → Li2O2 4Li + O2 +2H2O → 4Li(OH)or 4Li + O2 → 2Li2O

S t P l / l fib LISICON lSeparator Polymer/glass fiber LISICON glassTheoretical specific energy if only Li included (Wh/kg)* 11,238/11,972 ~12,000

Theoretical specific energy p gyif Li/carbon/electrolyte are included (Wh/kg)**

3031 1436

Practical specific energy for complete Li-air batteries ? ? p*Abraham, KM and Z Jiang.1996. Journal of the Electrochemical Society 143-1, 1 (1996)** Zheng et al. Journal of the Electrochemical Society 155 (6), A432 (2008)

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Reaction Processes in Metal-Air Batteries

Anode Air electrode

Alkaline

Separator Air electrodeSeparatorAnode

n/4 O2Mn+ne-

Mn/2 H2O

Final

Alkalineelectrolyte

2Li+

2Li

Non-aqueous electrolyte

O2-2

On OH-1

ne-

Separator

M(OH)n

Final product stays in anode

2e- O2

2e-

Li2O2Final product stays in air

l t dLoad

M+ n/4 O2 +n/2 H2O → M(OH)n

Loadelectrode

2Li + O2 → Li2O2

(a) Aqueous based electrolyte, where M represents metals (Zn, Al, Mg, Fe, Ca etc.). The reaction products (M(OH) ) are

(b) Lithium-air battery based on nonaqueous electrolyte. The reaction products (M(OH)n) are accumulated in the anode

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products (M(OH)n) are accumulated in the anode.

accumulated in the anode.

Challenges in Li-air Batteries

Primary:1. Improve the specific energy of air electrode 2. Improve the specific energy of full cell.3. Increase the ambient operation time.4 Increase the power rate4. Increase the power rate.

Rechargeable: 1 Find stable systems (aqueous or non aqueous) which are stable in1. Find stable systems (aqueous or non-aqueous) which are stable in

oxygen environment.2. Understand reversible mechanism of Li-O2 reaction.3. Develop an oxygen selective membrane.4. Prevent Li dendrite growth.

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2. Development of Primary Li-air Batteries

2.1 Air Electrode Simulation 2.2 Air Electrode Optimization2.3 Electrolyte Selection 2 4 Li-air Batteries with O Diffusion Membranes2.4 Li-air Batteries with O2 Diffusion Membranes

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2. Development of Primary Li-air Batteries

AirPNNL Approaches: Basic Structure:

Carbon-based Air Electrode

Cathode Current Collector+

Gas Diffusion Membrane

Air Stable Electrolyte

O2 Diffusion Membrane/moisture & electrolyte barrier

Separator

Li Metal

PackageNanostructured Carbon with High Mesoporous Volume

Anode Current Collector-

Initial cell configuration:Anode Cap

Lithium Metal

Initial cell configuration:Type 2325 coin cells

Test in dry box (RH ~ 1%)

Insulation Gasket

Nickel Mesh(Spot welded to can) 

Air Electrode

Separator

Ai A H l

8

CanAir Access Hole 

Gas Diffusion Barrier

Performance of Li-air Pouch Cell in Ambient Environment

3 0

3.5Carbon loading: 4 mg/cm2

2.0

2.5

3.0ge

(V)

0 5

1.0

1.5

Vol

tag

0.05 mA/cm20.1 mA/cm2

0.0

0.5

0 1000 2000 3000 4000 5000 6000 7000Specific Capacity (mAh/g)Specific Capacity (mAh/g)

C-PNL based pouch cell is operated in ambient environment. Specific capacity is doubled for C-PNL compared with KB. Rate performance is also improved

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Rate performance is also improved.

Optimized Area-Specific Capacities

12

14

1400

1600

2)

8

10

12

1000

1200

city

(mA

h/cm

2

Ah/

g C

arbo

n)

4

6

400

600

800

peci

fic C

apac

Cap

acity

(mA

0

2

0

200

0 5 10 15 20 25 30

Are

a S

p

Spe

cific

0 5 10 15 20 25 30

Carbon Loading (mg/cm2)

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Hybrid Li-air Battery for High-Rate Operation

Air

G di t ib ti b

Gas diffusion barrierAir stable electrolyte

Carbon-based air electrode

Cathode t ll t +

Gas distribution membrane

Carbon

BinderLi+ insertion compound

Li

Li +e

-

i

Li metal

Anode

current collector +

-

Separator

(no Li + insertion)

Li

Li +e

-

i

current collector

Package

High rate Li+ insertion compound (< 2.8V) can provide high-rate capability. CF l d l t d bl ki CFx also reduce electrode blocking.

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Comparison of Hybrid Air Electrodes 

3.5

4.0

(a) 0.1 mA/cm2

2.5

3.0(V

)

1.5

2.0

Volta

ge

55%KB+30%MnO2+15%Teflon

55%KB+30%V2O5+15%Teflon

0.5

1.055%KB+30%V2O5+15%Teflon

55%KB+30%CFx+15%Teflon

85%KB+15%Teflon0.0

0 100 200 300 400 500 600 700 800 900 1000Specific Capacity (mAh/g)

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Jie Xiao, Wu Xu, Deyu Wang, and Ji-Guang Zhang, J. Electrochem. Soc. 157, A294 (2010).

Additive Leads to 30% Increase in Capacity

12-crown-4 in 1.0M LiTFSI in PC/EC (1:1 wt)

240

160

200ca

rbon

)

80

120

city

(m

Ah/g

c 30% increasein capacity

0

40

80

Cap

ac

Solvability limit

00% 4% 8% 12% 16% 20%

12-Crown-4 content in electrolyte

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W. Xu, J. Xiao, D. Wang, J. Zhang, and J.-G. Zhang, Electrochemical and Solid-State Letters, 13 (4) A48-A51(2010).

Proto-Type Li-air Batteries with O2 Diffusion Membranes

Cell Designs:

a. G1 cell design. 2325 coin cell. Diameter = 2.3 cm

b. G2 cell design. Single side pouch cell with diffusion holes (4cmx4cm).

c. G3 cell design. Double side pouch cell with low permeability polymer

d. G4 cell design. Double side pouch cell with low permeability polymer

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cell with low permeability polymer window (4cmx4cm)

cell with low permeability polymer Window. (4.6cmx4.6cm).

Cell Design with Polymer Diffusion Barrier

0.8 mil polymer membrane

Metal mesh 0 7 mm KB carbon electrode0.7 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

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Discharge Profile of a Li-air Battery with an O2 Diffusion Membrane

3.2

3.6

2.4

2.8

)

1.2

1.6

2

Volta

ge (V

)

Operated in ambient air (~20% RH) for 33 daysTotal weight of the complete battery: 8 387 g

0

0.4

0.8Total weight of the complete battery: 8.387 gSpecific energy: 362 Wh/kg

00 0.2 0.4 0.6 0.8 1 1.2 1.4

Cell capacity (Ah)

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The Best Primary Li-air Batteries

2.8

3.2

3.6

2300 mAh/g carbon

1.6

2

2.4

Volta

ge (V

)

Operated in ambient air (~20% RH) for 33 days

0

0.4

0.8

1.2( ) y

Total weight of the complete battery: 8.387 gSpecific energy: 362 Wh/kg Li-air cell with new carbon

Operated in O2

00 0.2 0.4 0.6 0.8 1 1.2 1.4

Cell capacity (Ah)

Best specific energy for complete Li-air battery operated in ambient

New carbon increases capacity to 8000 mAh/g

New carbon and new electrolyte further increase the capacity to15,000 mAh/g

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4. Summary

1. Developed an unique package membrane which can also serve as an O2diffusion membrane, water barrier, and electrolyte barriers. It enables Li-air b tt i t k i bi t i f 33 dbatteries to work in ambient air for 33 days.

2. Developed Li-air batteries with a specific energy of ~362 Wh/kg for the complete battery. p y

3. Hybrid air electrode with KB/CFn can significantly increase the power rate of Li-air batteries.

4. Electrolyte weight dominates battery weight structure. Reducing the electrolyte amount will be the key to further increase the specific energy of Li-air batteries.

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2.2 Investigation on the Reaction Products of Li-Air Batteries

- +

Teflon container

In situ analysis

O2 in Mass Spec---CO2?

GC---CO2?

Coin cells holder

Compressed

Li/air coin cells filled with 1M LITFSI in PC/EC (low vapor pressure electrolyte )

holder

ex situ analysis

Compressed O2, 2 atm X-ray

FTIRNMR

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Prove of Chargeability for Li-air Batteries

0.5 5

0.3

0.4si

tion

(%)

4

ge (V

)

Voltage

O2

0.2

Gas

Com

pos

3 Cel

l Vol

tag

N2/CO

H2O

0

0.1

G

2

CO2

Ar

85% of Li O has been decomposed

0 5 10 15 20Time (hours)

85% of Li2O2 has been decomposed

Table 1. Electrochemical parameters of metal-oxygen couples

Metal/O2 Couple

Specific Charge

Capacity Based on

Metal(Ah/g)

Theoretical Voltage

(V)

Practical Voltage

(V)

Specific Energy

Based on Metal

(Wh/kg)

Specific Energy Based on Metal

andH2O (aqueous

only)(Wh/kg)

Specific Energy

Based on ReactionProducts(Wh/kg)

In Nonaqueous ElectrolytesLi + ¼ O2 → ½ Li2O 3.862 2.91 2.80 10,813 10,813 5,023Li + ½ O2 → ½ Li2O2 3.862 3.10 3.00 11,586 11,586 3,505In Aqueous ElectrolytesLi + ¼ O2 + ½ H2O → LiOH(a) 3.862 3.45 3.00 11,586 5,044 3,359Zn + ½ O2 → ZnO 0.820 1.65 1.10 902 902 725Zn ½ O2 ZnO 0.820 1.65 1.10 902 902 725Al + ¾ O2 + 1½ H2O→ Al(OH)3 2.980 2.71 1.30 3,874 1,936 1,340Mg+ ½ O2 +H2O → Mg(OH)2 2.205 2.93 1.30 2,867 1,647 1,195Fe+ ½ O2 +H2O → Fe(OH)2 0.960 1.30 1.00 960 726 597Ca + ½ O2 +H2O → Ca(OH)2 1.337 3.12 2.00 2,675 1,846 1,447(a) In a basic electrolyte with a protected lithium electrode (Visco et al. [5]).

2. Development Li-Air BatteriesLi-Air

>3000Wh/kg

Li-S> 400Wh/kg

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