all-solid li-s batteries - chemical sciences and ...€¦ · 10 managed by ut-battelle...

All-Solid Li-S Batteries

Chengdu Liang, Nancy Dudney, Zhan Lin, and Zengcai Liu

6th US-China EV and Battery Technology Workshop

Aug 23, 2012

2 Managed by UT-Battelle for the U.S. Department of Energy Presentation_name

Li-S batteries meet both the cost and energy targets for EV

• High energy density – Theoretic: 2550 Wh/kg, 2862 Wh/l

• Low cost – Sulfur is free – Cell cost is low

courtesy of Alberta Sulfur Research Ltd

Megaton storage block of S

Estimated cost at cell level: $100/kWh

DOE, AEV, 2020 target: $100-150/kWh

courtesy of Nohms


Liquid electrolytes lead to short cycle life of Li-S batteries

• Dissolution of sulfur cathode – Loss of active material – Self discharge – Low energy efficiency (polysulfide

shuttle)

• Problematic cycling of Li anode – Dendritic growth of lithium – SEI formation – Safety

Li film

SEI SEI

dendrites

Using a solid electrolyte can solve all these problems!

Li2S Li2S4 Li2S6 Li2S8 S8


Challenges for all-solid Li-S batteries

Li

SE

S Lithium anode:

Chemical and electrochemical compatibility

Solid Electrolyte: High ionic conductivity

Sulfur cathode: • Ionic

conductivity • Electronic

conductivity


Nanostructured Li3PS4 has a high ionic conductivity

1.8 2.0 2.2 2.4 2.6 2.8 3.0 3.2 3.4-7

-6

-5

-4

-3

-2Nanoscale phase

γ-Li3PS4

β-Li3PS4

log

σ / S

cm-1

T-1 / 1000 (K-1)

Bulk phase

300250 200 150 100 50

T (°C)

Mercier et al., Solid State Ionics (1984), Kanno et al., Solid State Ionics (2011) *Liang et al., patent pending

X1000

Liu and Liang, Nature Materials (under review)

0.0 0.2 0.4 0.6 0.8 1.0

0

20

40

60

80

100

120

1 10 100

0.0

0.5

1.0

1.5

2.0

2.5

dV/d

D / 1

0-3cm

3 g-1nm

-1

Pore Diameter / nm

Volu

me

adso

rbed

/ cm

3 g-1 S

TP

Relative pressure / P/P0

Li3PS4•3THF Li3PS4


Excellent compatibility of Li3PS4 with lithium metal anode

0 1 2 3 4 5-80-60-40-20

0204060

i / µ

Acm

-2

E / V vs Li/Li+0 1000 2000 3000 4000 5000

-0.10-0.08-0.06-0.04-0.020.000.020.040.060.080.10

Appl

ied

cell

volta

ge /

VTime / min

80oC 25oC

Cyclic voltammogram

Good electrochemical stability: • Li deposition at 0V • No redox peak up to 5V

Excellent cyclability: • No obvious interfacial reaction • Reversible Li plating

Li|SE|Li symmetric cell test


Li+

Li+Li+

P

S-

-S

S-

S + (x+y+z) SWet-Chemistry

Li+

Li+

Li+

P

S

S

S

S

Charge/DischargeLi

a

b

+ 2(x+y+z) (x+y+z)

Li+

P

S-

-S

S-

S + Li+Li+

S2-

Li+

Li+

Sx-

-Sy

Sz-

Li+

Li+

Li+

P

S

S

S

S

Sx-

-Sy

Sz-

Overcome the poor ionic conductivity of S cathode through chemical reactions Key problem for S cathode: Poor ionic conductivities of S and its discharge products

Lin and Liang patent pending


Raman spectra and XRD confirm the reaction of S with Li3PS4

100 200 300 400 500 600

Li3PS4

Li3PS4+3

Li3PS4+5

Li3PS4+6Inte

nsity

(a.u

.)

S

Wavelength (cm-1)

Peaks related to S-S bond

125 130 135 140 145 150 155 160 165 170 175

Li3PS4+3

Li3PS4+5

SLi3PS4+6

Inte

nsity

(a.u

.)

Wavelength (cm-1)

460 465 470 475 480 485 490

S

Li3PS4+3

Li3PS4+5

Li3PS4+6

Inte

nsity

(a.u

.)

Wavelength (cm-1)

10 20 30 40 50 60 70 80

Inte

nsity

(a.u

.)

2θ (degree)

S

Li3PS4

Li3PS4+5


Ionic conductivity of the cathode is a function of S to Li3PS4 ratio

2 3 4 5 6 7 8-5.4

-5.1

-4.8

-4.5

-4.2

-3.9

-3.6

Li3PS4+n

n

Log

σ (S

cm-1)

2.8 2.9 3.0 3.1 3.2 3.3 3.4 3.5-5.0

-4.8

-4.6

-4.4

-4.2

-4.0

-3.8

-3.6

log

σ (S

cm-1)

1000/T (K-1)

Ea = 0.37 eV

Li3PS4+5

90 80 70 60 50 40 30 20t / oC

Room temperature conductivity as a function of sulfur in SE

Arrhenius plot

Room temperature conductivity of Li3PS4+5 is 100,000 times higher than that of Li2S!

Logσ= −3.5 − 0.22𝑛

𝜎 = 𝐴0𝑒−𝐸𝑎𝑅𝑅


All-solid Li-S batteries have excellent cyclability and rate performance

0 50 100 150 200 250 300

0

200

400

600

800

1000

1200

1400

1600

Discharge Charge Discharge Charge

Cycle number

RT

60 oC

0

100

200

300

400

500

600

700

Cap

acity

(mA

h g-1

, nor

mal

ized

to S

)

C

apacity (mA

h g-1, norm

alized to Li3 PS

4+n )

0 10 20 30 40 50 600

200

400

600

800

1000

1200

1400

1600

Discharge Charge

Cap

acity (mA

h g

-1, no

rmalized

to L

i3 PS

4+n )

Cap

acit

y (m

Ah

g-1, n

orm

aliz

ed t

o S

)

2CC

C/5

C/2.5

C/10C/10

Cycle number

0

100

200

300

400

500

600

700100% coulombic efficiency!


All-solid Li-S batteries have a different electrochemical reaction path

0 300 600 900 1200 15000.0

0.5

1.0

1.5

2.0

2.5

3.0

Volta

ge (V

)

Capacity (mAh/g)

RT discharge RT charge 60C discharge 60C charge

60 °C

RT

0 200 400 600 800 100012000.00.51.01.52.02.53.0

Volta

ge (v

s. L

i/Li+ )

Capacity (mAh g-1)

Discharge

Charge

Solid electrolyte Liquid electrolyte

No polysulfide plateau presents in the all-solid cell


Cathode structure preserved after intensive cycling

SEM and elemental maps before cycling

SEM and elemental maps after 300 cycles at 60 °C

C

C

P

P S

S


Conclusions • Nanostructured Li3PS4 has superior electrochemical properties

– High ionic conductivity ~10-3 Scm-1 at room temperature – Wide electrochemical window up to 5V – Compatible with lithium metal anode

• Cathode with a lithium-conducting sulfur compound – 5 orders of magnitude of improvement in ionic conductivity versus

Li2S – Good rate performance – Excellent cyclability

• All-solid battery overcomes the problems of conventional Li-S batteries – No PS shuttle, high coulombic efficiency, no self-discharge – Enabling metallic Li anode


Acknowledgements

Funding support

BES

VT program

User Facility

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