Advanced Electrolyte Salts with Inherent Overcharge Protection for

208th ECS Meeting, Abstract #223, copyright ECS
Advanced Electrolyte Salts with Inherent Overcharge
Protection for Lithium Ion Batteries
K. Amine, J. Liu, A.N. Jansen, Z. Chen
Argonne National Laboratory
9700 South Cass Ave.
Argonne, IL 60439, USA
1
Normalized capacity
G. Dantsin, K. Jambunathan, S.V. Ivanov, W.J. Casteel
Air Products and Chemicals, Inc.
7201 Hamilton Blvd.,
Allentown, PA 18195, USA
1.2
0.8
0.6
0.4
0.2
0
0
50
100
Cycle number
In addition to their function as lithium
electrolytes, these salts are able to function as tunable
redox shuttles.
The electrolyte’s unique oxidation
chemistry also provides inherent protection against
overcharge, an important safety issue for lithium batteries.
This overcharge protection is shown as a reversible redox
peak with a tunable oxidation onset potential around 4.5
V vs. Li/Li+ (Figure 2). The redox potential is tunable by
controlling the degree of fluorination in the
fluorododecaborate anion, i.e. lower fluorination provides
a lower overcharge voltage. The 1C overcharge cycling
behavior for a GDR negative and LiNi0.8Co0.15Al0.05O2
positive electrode with the partially fluorinated
Li2B12F9H3 and LiPF6 in 3:7 EC:DEC is shown in Figure
3. The cell exhibits stable voltage plateaus at around 4.5
V for almost 100 hours under overcharge and negligible
discharge capacity fade. Extended overcharge protection
at 1C to 2C-rates has been observed, and significantly
higher rates appear obtainable over shorter periods of
time. The electrolyte also provides overcharge protection
for other cathodes including spinel and olivine based
materials.
Oxidation : B12FxH12-x 2- Æ B12FxH12-x1- + eTunable
Oxidation Onset
potential
Cell Operating Range
LiPF6
Reduction : B12FxH12-x1- + e- Æ B12FxH12-x2-
Figure 2. CV of Li2B12FxH12-x in 3:7 EC:DEC (Pt
working) showing the overcharge redox shuttle in
comparison to LiPF6.
0.0065
5
0.0055
0.0045
4
0.0035
3
0.0025
0.0015
2
Voltage(V)
At Air Products and Chemicals, Inc., (APCI) we
are developing weakly coordinating perfluoroborane
cluster
salts,
i.e.
lithium
fluorododecaborates
(Li2B12FxH12-x), to make stable lithium battery electrolyte
formulations for advanced, high power batteries.
Evaluation of these salts has shown exciting potential for
both portable and hybrid electric vehicle (HEV)
applications. Their extraordinary thermal and hydrolytic
stability could allow the use of safer, lower cost electrode
materials in large lithium-ion batteries. For example, we
have observed that their use in full cells with LiMn2O4
results in much lower capacity fade over 55oC cycling
than LiPF6-based electrolytes (Figure 1).
Figure 1. Cycle life capacity of 0.4M APCI salt +
Additive A in 3:7 EC:EMC in a MCMB//Spinel cell at 55
o
C.
Current(A)
Lithium-ion batteries, by virtue of their
extremely high energy and power densities, are the
dominant technology for rechargeable power in portable
electronics. Larger versions appear to be ideally suited for
hybrid and electric vehicle applications. Currently,
lithium-ion technology use in large-scale systems is
limited due to the reactivity of the battery components,
which present significant safety and cycle-life issues.
Development of more stable lithium-ion battery materials
is a key focus of ongoing R&D efforts.
0.0005
-0.0005
1
-0.0015
-0.0025
0
50000
100000
150000
200000
250000
300000
350000
400000
450000
0
500000
Test_Time(s)
Figure 3. Overcharge testing to 5V at 1C rate of
Li2B12F9H3 with LiPF6 in 3:7 EC:DEC in
GDR//LiNi0.8Co0.15Al0.05O2 cell. Top plot shows the
overcharge voltage stabilized at ~4.5 V for about 100
hours.
Acknowledgment: The authors acknowledge Lithium
Technology Corporation for providing large format cell
testing.
We will also discuss our efforts to lower capacity
fade with the addition of suitable additives.
Downloaded on 2018-02-20 to IP 88.99.70.242 address. Redistribution subject to ECS terms of use (see ecsdl.org/site/terms_use) unless CC License in place (see abstract).