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