V. Focused Fundamental Research - EERE - U.S. Department of ...

Liang – ORNL
V.B.12 Developing Materials for Lithium-Sulfur Batteries (ORNL)
Electrolyte additives have the potential to accelerate
the electrochemical cycling of the sluggish Li 2 S. The
compatibility of additives with cell components is the
major issue of using additives. Organic additives could
have problems with lithium anode that have not been
previously recognized. Phosphorous sulfide is an excellent
additive for Li-S batteries. The exact mechanism is
unknown. Further investigation in this direction is needed.
Figure V - 66: (a) Voltage profiles of Li-S cell with phosphorous sulfide additive. (b) cycling performance at 0.1 C in 1m LiTFSI.
Voltage (V vs Li/Li + )
-1
Capacity (mAh g )
3.2
3.0
2.8
2.6
2.4
2.2
2.0
1.8
1.6
A
Ch arg e
Disch arg e
0 200 400 600 800 1000 1200 1400
C ap ac ity (m A h g -1 )
0.22
0.20
0.18
0.16
0.14
0.12
0.10
0.08
0.06
0.04
0.02
0.00
1600
100
1400
B
1200
80
1000
60
800
600 40
400
Ch a rg e
20
200
Dis c h a rg e
0 0
0 5 10 15 20 25 30 35 40 45 50
C y cle Num ber
Figure V - 67: (a) Voltage profile of first charge/ discharge cycle of Li-S cell with a pre-formed SEI on Li anode. (b) coulombic efficiency and cycling
performance of the cell after the blockage of polysulfide shuttle.
Protecting the lithium anode by sulfide-based solid
electrolytes can efficiently block the polysulfide shuttle but
the sluggish electrochemical cycling of Li 2 S is still a
problem for capacity retention. Diagnosis of lithium anode
after cycling is necessary. A transfer stage for air-sensitive
materials has been developed for the diagnosis of Li-S
cells under SEM.
Future research will focus on the phosphorous sulfidebased
electrolyte additives. The immediate next step will
be the investigation of the long-term stability of the
phosphorous sulfide additives. The mechanism of the
additive effect will be studied in detail for the purpose of
guiding the search of additives. The protection of the
lithium anode will be studied intensively. Ultimately, the
Current Density (mA cm -2 )
Coulombic Efficiency (%)
success of lithium anode protection will not only benefit
the Li-S battery but also all other batteries which use
lithium metal as the anode. Because of the dissolution of
the sulfur species in the electrolyte, the cathode in Li-S
batteries is considered a “liquid” electrode. Novel cell
configurations will be explored to investigate the
feasibility of Li-S in large format batteries for EV and
PHEV applications.
FY 2011 Publications/Presentations
1. Zengcai Liu, Wujun Fu, Chengdu Liang (2011)
“Lithium Sulfur Batteries”. In “Handbook of Battery
Materials” John Wiley & Sons, Ltd.
FY 2011 Annual Progress Report 527 Energy Storage R&D