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Redox shuttle additives towards safer
lithium-ion batteries
Lu Zhang03-21-2017
International Battery Seminar & Exhibit
Fort Lauderdale, FL
May contain trade secrets or commercial or financial information that is privileged or confidential and exempt from public disclosure.
9/20/2014
Lithium ion batteries
3/3/2017
May contain trade secrets or commercial or financial information that is privileged or confidential and exempt from public disclosure.
2
E anode E cathode
Charging process
High energy density
Long working life
No memory effect
Li metal oxidegraphite
Safety
Cost
Overcharge Abuse and Preventions
Protections:
Electronic devices with specific chargers
Additives: redox shuttles etc.
Redox Shuttle: Mechanism and Examples• Redox shuttles:
reversibly oxidized and reduced at specific potential slightly higher the end-of-
charge potential of positive electrode
electrolyte
e
S
S+
e
S+
S
e
A
diffusion
Standards and Examples for Redox Shuttle Additives
O
O
DDB: 3.92 V
O
CF3
O
CF3
DBDFB: 4.25 V
F
F
F
F
O
O
B
F F
F
FF
PFPTFBDB: 4.43 V
C. Buhrmester; L. Moshurchak; R. C. L. Wang and J. R. Dahn, Journal of the Electrochemical Society, 2006, 153 (2): A288-A294.
C. Buhrmester, L. M. Moshurchak, R. L. Wang, and J. R. Dahn, J. Electrochem. Soc., 2006, 153, A1800-A1804.C. Buhrmester, J. Chen, J. Jiang, R.L. Wang, J.R. Dahn, J. Electrochem. Soc. 152 (2005) A2390.
L. M. Moshurchak, and J. R. Dahn etc. Journal Electrochem. Soc., 156 (4) A309-A312 (2009)
Z. Chen, K. Amine, Electrochem. Commun. 9 (2007) 703.
S
N
N
O
MPT: 3.47 V
TEMPO: 3.45 V
Electrochemical reversible at suitable potentials;
Long overcharge protection time or stability;
Compatibility;
2,5-ditertbutyl-1,4-dimethoxybenzene (DDB) and Its Limits
O
O
DDB: 3.92 V
C. Buhrmester, J. Chen, J. Jiang, R.L. Wang, J.R. Dahn, J. Electrochem. Soc. 152 (2005) A2390.
Advantage of DDB:
Suitable potential; Excellent stability;
Drawback of DDB:
Low solubility in conventional electrolyte
and the concentration is dependant on
lithium salt concentration (< 0. 08 M in
Gen 2 electrolyte), requirement of specific
formulated electrolyte (0.5 M LiBOB in
PC:EC:DEC:DMC= 1:1:2:2 by volume),
adding cost and complexity;
New designs:
Improve the compatibility of redox shuttles
without weakening their stabilities and
lowering potentials.
OMe
OMe
ANL-1: ? V
One possible solution is to break down
the chemical structural symmetricity.
Synthesis and chemical characterization of Catechol-like Version of DDB --- ANL-1
ANL-1, yield 71 %
OH
OH
NaH /CH3IOMe
OMeTHF
Electrochemical evaluation of ANL-1
When a 3mAh 18650 cell is on overcharge, 0.22 M ANL-1 will be needed to shunt the 1C
overcharge current. And ANL-1 can dissolve almost 1.0 M in gen 2 electrolyte.
Cyclic voltammograms of ANL-1 (10 mM) in 1.2 M
LiPF6 in EC/EMC (3:7 by weight) 100mV/s.
Eredox= 4.2 V vs Li/Li+
Voltage and capacity retention profiles of Li/LiFePO4 and MCMB/LiFePO4
cells containing 0.1 M ANL-1 in 1.2M LiPF6 in EC/EMC (3:7 by weight)
during the course of 0-2300 h. Charging rate is C/10 and overcharge rate is
100%. More soluble but less stable than DDB.
Possible decomposition path ways of ANL-1 and new strategy
ANL-1 DDB
OMe
OMe
O
OMe
CH3++
OMe
OMe
For DDB, the methoxy bond is stronger than
the one in ANL-1
Decomposition path ways for radical cation:
polymerization on the benzene ring or the
cleavage of the alkoxy bonds
Breaking down the symmetry of the
chemical structure increased the solubility
but decreased the electrochemical stability.
Polyether groups have been proposed to be
introduced into the novel redox shuttles to
improve the solubility;
Advantages: keep the symmetric structure
and thus keep the electrochemical
properties
OH
NaH /THFHO
OO
Cl
OO
O
O
O
O
Single crystal and CV test of DBDMEMB
3.0 3.5 4.0 4.5
-5
0
5
Curr
ent
(1e-
5A
)
Petential, V vs Li/Li+
1st Scan
2nd Scan
3rd Scan
2,5-Di-tert-butylhydroquinone
Cyclic voltammograms of DBDMEMB (10 mM) in 1.2 M
LiPF6 in EC/EMC (3:7 by weight) 100mV/s
OHHOO O
O
O
O
O
redoxOHHO
O O
O
O
O
O
redox
The O-C-O linkage is not electrochemically stable
Improve the electrochemical stability of the linkage: ANL-2 (1,4-Bis(2-methoxyethoxy)-2,5-di-tert-butyl-benzene)
ANL-2, yield 70 %
OH
OH
+O
ClNaH / THF
O
O
O
O
Cyclic voltammetry of ANL-2
2.8 3.0 3.2 3.4 3.6 3.8 4.0 4.2 4.4 4.6-12
-9
-6
-3
0
3
6
9
12
15
Cu
rren
t (1
e-5
A)
Voltage (V)
500 mV/s
200 mV/s
100 mV/s
50 mV/s
20 mV/s
Cyclic voltammograms of ANL-2 (10 mM) in 1.2 M
LiPF6 in EC/EMC (3:7 by weight) 100mV/s.
Increase the carbon number
between the two oxygen
atoms significantly improve
the electrochemical stability,
as a result ANL-2 exhibits
perfectly reversible redox
peaks at 3.9 V vs Li/Li+
Cycling tests of ANL-2 --- MCMB/LiFePO4
Voltage and capacity retention profiles of
MCMB/LiFePO4 cell containing 0.1 M ANL-2 in
1.2M LiPF6 in EC/EMC (3:7 by weight) during the
course of 0-2300 h. Charging rate is C/10 and
overcharge rate is 100%.
0 20 40 60 80 1000
1
2
3
Ca
pa
city
(m
Ah
)
Cycle Number
Charge
Discharge
Fast cycling tests of ANL-2 --- MCMB/LiFePO4 (C/2)
0 20 40 60 80 100 120 140 160 1800
1
2
3
4
Ca
pa
city
(m
Ah
)
Cycle Number
Charge
Discharge
Voltage and capacity retention profiles of
MCMB/LiFePO4 cell containing 0.4 M ANL-2 in
1.2M LiPF6 in EC/EMC (3:7 by weight) during the
course of 0-1000 h. Charging rate is C/2 and
overcharge rate is 100%.
Improved solubility and comparable stability
compared to DDB
Normal cyclability and HPPC comparison with and without ANL-2
Capacity retention and HPPC profiles of SMG/LiFePO4 cells
containing none or 0.35 M ANL-2 in 1.2M LiPF6 in EC/EMC
(3:7 by weight). Charging rate is C/3 and cut off voltage is 2.3
~3.6 V. Pulse: 3C and regen :2C.
0.0 0.5 1.0 1.5 2.0 2.5
0
20
40
60
80
100
nliu387/394
AS
I, o
hm
-cm
2
Capacity, mAh
SMG/LFP cell
1.2M LiPF6 EC/EMC (3/7)
HPPC
pulse: 3C
regen: 2Cw/ RS2
w/o RS2
0 50 100 150
0.0
0.5
1.0
1.5
2.0
Dis
char
ge
capac
ity
(m
Ah
)
Cycle number
Gen 2 electrolyte
0.35 M ANL-2 in Gen 2 electrolyte
0.35 M ANL-2 in Gen 2 electrolyte
Ways to increase the potentials
• ANL-2 is stable enough and suitable cathode material below 4V.
• High potential redox shuttles are in great need, and strategy to increase the
potentials:
• Low HOMO orbital, small conjugated ring>> benzene
• Electron withdrawing groups, such as –F, -Br, and –Cl.
• Some examples:
O
CF3
O
CF3
DBDFB: 4.25 V
F
F
F
F
O
O
B
F F
F
FF
PFPTFBDB: 4.43 V
Design and synthesis of ANL-3tetraethyl-2,5-di-tert-butyl-1,4-phenylene diphosphate (TEDBPDP)
17
O
O
P
P
O
OO
O
OO
HO
OH
+ 2O
PO
ClDIPEA
tert-Butyl hydroperoxide
ANL-3 redox shuttle
Cyclic voltammograms of ANL-3 (10 mM) in 1.2 M
LiPF6 in EC/EMC (3:7 by weight) 100mV/s.
ANL-3 is probably one of the
redox shuttles with highest
oxidation potential, which is
~4.8 V
Solubility is ok.
Reversibility or stability needs
improvements.
4.0 4.5 5.0
-10
0
10
20
Curr
ent (µ
A)
E (Volts)
20 mV/s
50 mV/s
100 mV/s
200 mV/s
Coin Cell Tests of ANL-4 --- Li/spinel LiMn2O4
2 4 6 8 10 120
1
2
3
Cap
aci
ty (
mA
h)
Cycle number
Charge capacity
discharge capacity
Voltage and capacity retention profiles of MCMB/spinel LiMn2O4 cell
containing 5 wt.% ANL-4 in 1.2M LiPF6 in EC/EMC (3:7 by weight) during
the course of 0-350 h.
0 5 10 15 20 25 30
3.5
4.0
4.5
5.0
Volt
ag
e (V
)
Time (h)
Other design-BPDP and DBDFDP
20
1,4-bis[bis(1-methylethyl)phosphinyl]-2,5-dimethoxylbenzene
(BPDB)
1,4-bis[bis(1-methylethyl)phosphinyl]-2,5-difluoro-3,6-
dimethoxylbenzene (BPDFDB)
ANL-4ANL-3
Cyclic voltammetry
21
3.6 4.0 4.4 4.8
2
0
-2
Cu
rren
t (1
e-5
A)
Potential, vs. Li/Li+
10 mV/s
20 mV/s
50 mV/s
100 mV/s
200 mV/s
500 mV/s
3.5 4.0 4.5 5.0 5.5
1
0
-1
-2
-3
-4
-5
-6
Cu
rren
tc(1
e-5
A)
Potential, vs. Li/Li+
100 mV/s
200 mV/s
500 mV/s
Cyclic voltammograms of 0.01 M BPDB (left) and BPDFDB (right)
in Gen 2 electrolyte at various scan rates using a Pt/Li/Li three-
electrode system.
Overcharge tests of ANL-4
22
Voltage (a) and capacity retention (b) profiles of overcharge abuse
test using MCMB/LMO coin cell containing 5 wt% BPDB in Gen 2.
The charging rate is C/10 and the overcharge is 100%.
Differential capacity profiles analysis
23
Differential capacity profiles of the formation cycles of cells using
LMO and MCMB as electrodes and containing 5wt % BPDB in
Gen 2; a) without LiBOB; b) with 2 wt% LiBOB.
1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5
-4
-2
0
2
4
Diff.
Ca
pa
city/[
mA
h/V
]
Voltage/V
With BPDBWith no BPDB
Impact of supporting SEI additive
24
0 1 2 3 4
-4
-2
0
2
4
Diff.
Ca
pacity/[m
Ah
/V]
Voltage/V
With BPDB + LiBOB With only LiBOB
Differential capacity profiles of the formation cycles of cells using LMO
and MCMB as electrodes and containing 5wt % BPDB in Gen 2; a)
without LiBOB; b) with 2 wt% LiBOB.
Overcharge protection performance
25
0 25 50 75 100
0.0
0.5
1.0
1.5
2.0
Charge capacity
Discharge capacity
Cap
acit
y (
mA
h)
Cycle number
2 4 6 8
Voltage and capacity retention profiles of overcharge abuse test using
MCMB/LMO coin cell containing 5 wt% BPDB and 2 wt% LiBOB in Gen 2.
The charging rate is C/10 and the overcharge is 100%.
0 20 40 60 80 100
3.0
3.5
4.0
4.5
5.0
Volt
age
(V)
Time (h)
summary
• By using different strategy a series of new redox shuttles have been developed
targeting improved compatibility to the state-of-art lithium-ion battery technology
and excellent electrochemical properties in terms of potentials and stabilities.
• The insights of the connection of chemical structure and cell performance were
obtained to further explore the new candidates of redox shuttles.
Acknowledgement
27
�Jingjing Zhang, Bin Hu, Zhengcheng Zhang
�Lei Change, Rajeev S. Assary, Larry A. Curtiss
�Ilya Shkrob
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