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Tadiran Confidential and Proprietary
Major Improvement
of the TMV
for
Li/SOCl2 System
H.Yamin ,A. Ulus and J. Heller
Tadiran Confidential and Proprietary
Outline
• Introduction
- TMV & the voltage delay phenomena
- TMV Improvement –historical perspective
• Experimental
- The electrochemical cells
- Test equipment
• Results & Discussion
- Pulse and discharge tests
- EIS & SEM study
Summary & Conclusions
2
Tadiran Confidential and Proprietary
Introduction
Tadiran Confidential and Proprietary
TMV & Voltage Delay Phenomena
Volt
age
Time
OCV
TMV
0
Tadiran Confidential and Proprietary 5
Transition Minimum Voltage (TMV)
• The major drawback of Li/SOCl2 system is the voltage delay phenomenon
• Formation of LiCl film on the Li surface increases cell impedance with storage/operation time
• The ionic conductivity of the LiCl film is relatively low and its thickness is very difficult to be controlled
• Our idea is to coat the Li by a proprietary, unique and stable film
The TMV drawback
Tadiran Confidential and Proprietary
Improvement of voltage delay- historical perspective
Gabano claims dissolving Li2O or Li2S in electrolyte
Carl Schlaikjer GTE Labs : Li2B10Cl10
Chua & Merz 5% SO2 in electrolyte
A.N. Dey Duracell SO2 caused film to acquire more orderly appearance
J.W. Boyd addition of PVC in electrolyte coat the lithium surface
Fleischer & Thomas Ray O Vac coat the lithium foil by cyanoacrylate
Yamin & Eichinger patented polymer and Acid in solution
Tadiran Confidential and Proprietary
The Two Layers Model
7
Li
SEI 10-1000Å
Secondary
Layer
Tadiran Confidential and Proprietary
Experimental
The Electrochemical cell
• Standard size AA/2 , AA ,D
• Surface area : 5 Cm2 , 14 Cm2 ,45 Cm2
• Bobbin type construction
• Electrolyte
- Reference cells LiAlCl4 ,standard electrolyte
- Test cells : standard electrolyte + additive
Tadiran Confidential and Proprietary
Experimental
• Pulse test – Fast response Arbin data collecting system
• Electrochemical Impedance Spectroscopy - Solartron Sl 1260 impedance analyzer - typical 10mHz to 1MHz
• SEM study
- Specimens were prepared at dry room
- -40ºC due point
Tadiran Confidential and Proprietary
Voltage Transient after 427 Days
R&D Cell
Reference XOL Cell
D size cells @ 100mA Pulse @ RT
Tadiran Confidential and Proprietary
Voltage Transient after 180 Days
40mA pulse XOL electrolyte AA size cell
Tadiran Confidential and Proprietary
Treated Lithium AA size XOL
40mA pulse 154 days old
Tadiran Confidential and Proprietary
The Role of the new film
The new film separates between lithium and
SOCl2:
It prevents the vigorous reaction of SOCl2 with lithium metal :
- More ordered film is formed
- More dense and more compact SEI
- Less structural defects are formed by the slow reaction
2.0
2.2
2.4
2.6
2.8
3.0
3.2
3.4
3.6
0 10 20 30 40 50 60 70 80 90 100 110 120 130
V (
@1
ms)
t (Days from connecting the load)
OCV 360kΩ 180kΩ
Voltage after 1 mSec
Pulse test with background currents
20mA pulse for AA/2 Cell
Tadiran Confidential and Proprietary
Additives decrease capacity variations
TL 7903 AA size XOL electrolyte @ 330 Ω
15% more capacity with the TMV improved cell
Tadiran Confidential and Proprietary
Additives decrease capacity variations
TL 7903 AA size XOL electrolyte @ 680Ω
15% more capacity with the TMV improved cell
Tadiran Confidential and Proprietary
Additives to Xtra Version cells
TL 8903 discharged @ 330 ohm Xtra
10 % more capacity than iXtra cell
Tadiran Confidential and Proprietary
Additives to Xtra version AA cells
TL 8903 discharged @ 680 ohm
15% more capacity than iXtra cell
Tadiran Confidential and Proprietary
Cell Types in Production
Tadiran Rapid Response Series TRR*
TRR 79XX – TMV improved XOL Type cells
AA size TRR 7903
D size TRR 7930
TRR 89XX – TMV improved Xtra type cells
AA size TRR 8903
D size TRR 8930
* Series Name Creator - Lou Adams
Tadiran Confidential and Proprietary
Electrochemical Impedance Spectroscopy
Reference cells Test cells
Tadiran Confidential and Proprietary
SEM Photograph 1M Old Cell
Reference cell
Tadiran Confidential and Proprietary
SEM Photograph 1M Old Cell
Test Cells
Tadiran Confidential and Proprietary
SEM Photograph 1 Y old Cell
Reference cell
Tadiran Confidential and Proprietary
SEM photograph 1 Y old cell
Test Cell
Tadiran Confidential and Proprietary
Summary & Conclusions
• Lithium anode was coated in situ by lithium ion conducting solid electrolyte interphase.
• The film morphology and cell impedance exhibit a small variation with storage time.
• This leads to a significant improvement of the voltage delay behavior of the Li/SOCl2 cells.
Tadiran Confidential and Proprietary
Thank You