Future battery chemistries –the rôle of sodiumA. Robert ArmstrongA. Robert Armstrong

EaStCHEM, School of Chemistry, University of St Andrews, St. Andrews, UK

•Why sodium?•Comparison of sodium ion vs lithium ion

•Similarities and differences•Negative electrodes

•Oxides•Alloys•Organics

•Positive electrodes•Polyoxyanions•Layered materials

More important today than at any time in historyOutils portatifsOutils portatifs

Power tools

Energy storageEnergy storage

Medical applicationsImplantable batteryImplantable battery

Artificial heartArtificial heart

Portable electronics

Sola

rW

ave

Win

d

Electricity generation Renewables

IntermittentIntermittent

Nuclear

ContinuousContinuous

Electrificationof transport

Electric Plug-inPlug-inHybridHybrid

Sodium-ion BatteriesSodium-ion Batteries

Much interest due to •low cost •potential for grid scale application

From Li-ion to Na-ion BatteriesFrom Li-ion to Na-ion BatteriesVast market for Lithium-Ion Batteries

Lithium resources unevenly distributedMost in Andes (Chile, Bolivia)

NEED TO FIND ALTERNATIVES

• Li and Na: alkali metals

• Abundance on Earth:- Li: 25th r(Li+) = 67 pm- Na: 4th r(Na+) = 97 pm

Similar propertiesNa is low-cost but heavier molecular weight NIBs for static energy storage systems

Na and Li similar but different!Na and Li similar but different!Positive electrodes

Sodium compounds have stronger tendency to adopt layered structures (larger ionic radius)Lithium mostly octahedral coordination (tetrahedral in spinel)Sodium trigonal prismatic coordination (some octahedral)

Leads to different stacking sequences

O3 P2

Na(Cr/Fe)O2Li(Cr/Fe)O2

Na and Li similar but different!Na and Li similar but different!

Na compounds electrochemically active unlike their Li equivalents

S. Komaba et al., Electrochem. Comm. 12, 2010, 355

Positive electrodes

Na and Li similar but different!Na and Li similar but different!

Negative electrodes

Cannot use graphite as negative electrode – negligible sodium intercalation (below 0V)

Can insert/extract Na in amorphous hard carbonCheap (e.g. from pyrolysis of sugar)

Negative electrodes for Na-ionNegative electrodes for Na-ion• Unlike lithium Na does not form alloys with aluminium • No need for heavy, more expensive copper current collector

Hard carbon favoured at present but no clear favourite

Na2Ti3O7 – remarkably low voltage but poor capacity retention

Negative electrodes for Na-ionNegative electrodes for Na-ion

AlloysTin works well despite v. large volume change

Komaba et al. Electrochemistry Communications 21 (2012) 65–68

J. W. Wang, X. H. Liu, S. X. Mao and J. Y. Huang, Nano Lett., 2012, 12, 5897–5902

Negative electrodes for Na-ionNegative electrodes for Na-ion

Organics

Conjugated dicarboxylates e.g. terephthalateAvailable from biomass/recycling

Park et al. Adv. Mater. 2012, 24, 3562–3567

0 20 40 60 80 100 120 140 160 180 2000

50

100

150

200

250

Dis

char

ge c

apac

ity /

mA

hg-1

Cycle number

100 mA/g 400 mA/g

promising activity Capacity around 200 mAhg-1 at ~ 0.5 V vs. Na+/Na

Sodium 2,6 naphthalene dicarboxylate Sodium 2,6 naphthalene dicarboxylate

Positive electrodes for Na-ionPositive electrodes for Na-ion

Vanadium phosphates offer high voltage/good rate capability

Gover, R. K. B.; Bryan, A.; Burns, P.; Barker, J. Solid State Ionics 2006, 177, 1495

Ponrouch et al. Energy Environ. Sci., 2013,6, 2361-2369 DOI: 10.1039/C3EE41379A

Strong similarities with Li-ionSodium transition metal oxides and polyanionic systems

Polyanions

Positive electrodes for Na-ionPositive electrodes for Na-ionAs with Li-ion materials sulphates give high voltages

Prabeer Barpanda, Gosuke Oyama, Shin-ichi Nishimura, Sai-Cheong Chung & Atsuo YamadaNature Communications 5, Article number: 4358 doi:10.1038/ncomms5358

Na2Fe2(SO4)3

Positive electrodes for Na-ionPositive electrodes for Na-ionLayered compoundsHave access to Fe3+/Fe4+ couple not possible for LiNax[Fe1/2Mn1/2]O2 with P2 structure benchmark material

N. Yabuuchi, M. Kajiyama, J. Iwatate, H. Nishikawa, S. Hitomi, R.Okuyama, R. Usui, Y. Yamada and S. Komaba, Nat. Mater., 2012, 11, 512–517

Pros: Fe and Mn cheap and safe, high capacityCons: wide voltage range, significant fade, made with x = 0.67

Layered compoundsCan show MANY phase transitions

Jahn-Teller distortion and charge ordering

-120 -100 -80 -60 -40 -20 0 20 40

2.0

2.2

2.4

2.6

2.8

3.0

3.2

3.4

3.6

3.8

Pote

ntia

l / V

dQ / mAhg-1

-140 -120 -100 -80 -60 -40 -20 0 20

2.0

2.5

3.0

3.5

4.0

4.5

Na2/3(Mn,Ni)O22-4.3 V 10 mA/g 1M NaPF6 in PC 5% FEC

cycle 1 cycle 2 cycle 3 cycle 4 cycle 5 cycle 10 cycle 20

Pot

entia

l (V

)

dQ (mAh/g)

P2-O2 transition at high potentialShearing of layers

Use substitutions to remove transitions

-50050100

1.5

2.0

2.5

3.0

3.5

4.0

4.5

Volta

ge (V

)

Na0.67Mn0.95Mg0.05O2

Capacity (mAh/g)

P2 Nax(Mn,Ni,Li)O2 P2 Nax(Mn,Ni)O2

Advanced Energy Materials1, 333-336, 2011 DOI: 10.1002/aenm.201000061

P2 NaxMnO2 P2 NaxMn1-yMgyO2

0 10 20 300

20

40

60

80

100

120

140

160

180

Disc

harg

e Cap

acity

/ m

Ahg-1

Cycle number

5% Mg undoped

Improved stability compared with undoped material

0 5 10 15 20 250

50

100

150

200

250

Discharge Capacity Charge Capacity

Cycle Number

Capa

city

(mAh

/g)

20% Mg (slow cooled) very stable at low rate

-100 -50 0 50 100 1501.5

2.0

2.5

3.0

3.5

4.0

Volta

ge (V

vs.

Na+ /N

a)

Capacity (mAh/g)

x = 0x = 0.05x = 0.1x = 0.2

Structural Characterisation

20 40 60 80

2 / FeK1

x=0

x=0.05

x=0.1

OP4

P2

P2-OP4 transition disappears with increasing amount of Mg

0 70 140

3.0

3.6

4.2

Volta

ge (V

vs.

Na+ /N

a)

Capacity (mAh/g)

x = 0x = 0.05x = 0.1x = 0.2

0 10 20 30 40 50 60 70 80 90 1000

20

40

60

80

100

120

140

160

180 Na0.67

Mn0.95

Mg0.05

O2 quenched

Dis

char

ge c

apac

ity /

mA

h/g

Cycle number

50 mA/g 500 mA/g

Constant currentConstant current

0 10 20 30 40 50 60 70 80 900

20

40

60

80

100

120

140

160

180 Na0.67

Mn0.95

Mg0.05

O2 quenched

Dis

char

ge c

apac

ity /

mA

h/g

Cycle number

100 mA/g 1000 mA/g

Slow charge – fast dischargeSlow charge – fast discharge

Positive electrodes for Na-ionPositive electrodes for Na-ion

-NaMnO2

0 20 40 600

50

100

150

200

C/2 C/20

C/20

10C4C

2C

C

C/4

Spec

ific

Dis

char

ge C

apac

ity (m

Ah/

g)

Cycle Number

SummarySummary

• Sodium-ion chemistry has many similarities with lithium-ion

• Some unique features giving rise to attractive properties e.g.

Fe3+/Fe4+

• No need for copper current collector

• Low cost

• Performance can even rival Li-ion

AcknowledgmentsAcknowledgments