All-Solid Li-S Batteries - Chemical Sciences and ...€¦ · 10 Managed by UT-Battelle...
Transcript of 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
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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
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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
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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
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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
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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
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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
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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
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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!
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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
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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
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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