S 1

Glyme-based electrolytes for lithium metal batteries using insertion

electrodes: An electrochemical study

Shuangying Weia, Zhenguang Lib, Kento Kimurab, Shoichi Inoueb, Loris Pandinia, Daniele Di

Leccea, Yoichi Tominagab,c,** and Jusef Hassouna,c,d,*

a University of Ferrara, Department of Chemical and Pharmaceutical Sciences, Via Fossato

di Mortara 17, 44121, Ferrara, Italy.

b Tokyo University of Agriculture and Technology, Graduate School of Bio-Applications and

Systems Engineering (BASE), 2-24-16, Naka-cho, Koganei-shi, Tokyo 184-8588, Japan.

c Institute of Global Innovation Research (GIR), Tokyo University of Agriculture and

Technology (TUAT), Tokyo, Japan

d National Interuniversity Consortium of Materials Science and Technology (INSTM)

University of Ferrara Research Unit, University of Ferrara, Via Fossato di Mortara, 17,

44121, Ferrara, Italy.

Corresponding Authors: jusef.hassoun@unife.it，ytominag@cc.tuat.ac.jp

Supporting Information

S 2

Figures S1 and S2 show the chronoamperometry profiles and Nyquist plots (insets) at 25°C

and 50°C, respectively, of EIS measurements before and after polarization on Li/Li

symmetrical cells using DEGDME-LiTFSI (panel a), TREGDME-LiTFSI (panel b),

DEGDME-LiFSI (panel c), TREGDME-LiFSI (panel d), DEGDME-LiBETI (panel e), and

TREGDME-LiBETI (panel f). The data have been analyzed by NLLS method and the lithium

transference number (t+) has been evaluated by the method proposed by Evans et al. [1]. The

lithium transference number values are reported and discussed in the manuscript (Figure 2,

Results and discussion section). Table 1 in the Experimental section of the manuscript reports

the sample acronyms. Table S1 and S2 report the data used for the determination of the lithium

transference number using equation (1) in the manuscript at 25°C and 50°C, respectively. The

values of R0 and Rss (interphase resistances at middle-high frequencies of the initial state and

the steady state, respectively, reported in Figure S1 and Figure S2) were determined by NLLS

fit of the corresponding Nyquist plots using the equivalent circuit Re(RiQi)Q or (RiQi)(RQ)

with a chi-square (χ2) ranging from 9×10-5 to 6×10-6, thus ensuring acceptable accuracy. In the

equivalent circuits used for the study, Re is the electrolyte resistance, Ri is the

electrode/electrolyte interphase resistance, Qi is the pseudo-capacitance related to

electrode/electrolyte interphase, and Q or (RQ) is a low-frequency element accounting for Li+

diffusion phenomena [2]. The data reveal a general decrease of the lithium transference number

by the increase of the temperature as likely due to an increase of anion and solvent molecules

motion into the electrolyte and to enhanced solvation which hinder the transport of the lithium

ions as observed in previous paper [3].

S 3

0 20 40 60 80 100120

150

180

210

240

0 100 2000

100

200T(Li+) = 0.51±0.05

(a)C

urr

en

t /

mA

Time / minute

I0= 172 mA

ISS= 158 mA-Z

Im /

W

ZR / W

T = 0

T = 90 min

Ri

Qi

Re

0 20 40 60 80 10030

40

50

60

70

Cu

rren

t /

mA

Time / minute

I0= 51 mA

ISS= 42 mA

T(Li+) = 0.62±0.06

(b)

0 400 8000

400

800

Qi

Ri

-Zim

/ W

ZR / W

Re

T = 0

T = 90 min

0 20 40 60 80 1000

50

100

150

200

250

0 150 3000

150

300

(c)

Cu

rren

t /

mA

Time / minute

T(Li+) = 0.54±0.05

I0= 105 mA

ISS= 93 mA

Qi

Re

-ZIm

/ W

ZR / W

Ri

T = 0

T = 90 min

0 20 40 60 80 10050

100

150

200

250

300

350

0 100 2000

100

200

(d)

Curr

ent

/ m

A

Time / minute

T(Li+) = 0.67±0.07

I0= 193 mA

ISS= 151 mA

-ZIm

/ W

ZR / W

T = 0

T = 90 min

Ri

Qi

Re

0 20 40 60 80 1000

30

60

90

120

0 300 6000

300

600T(Li+) = 0.82±0.08

Curr

ent

/ m

A

Time / minute

I0= 66 mA

ISS= 40 mA

(e)

ZR / W

T = 0

T = 90 min

-ZIm

/ W Ri

Re

Qi

0 20 40 60 80 10025

50

75

100

125

150

0 200 4000

200

400T(Li+) = 0.79±0.08

Curr

ent

/ m

A

Time / minute

I0= 89 mA

ISS= 68 mA

(f)

-ZIm

/ W

ZR / W

T = 0

T = 90 min

Re

Qi

Ri

Figure S1. Chronoamperometry profiles and Nyquist plots (insets) of EIS measurements before and

after polarization related to the calculation of the lithium transference number (t+) [1]. Measurements

performed on Li/Li symmetrical cells using (a) DEGDME-LiTFSI, (b) TREGDME-LiTFSI, (c)

DEGDME-LiFSI, (d) TREGDME-LiFSI, (e) DEGDME-LiBETI, and (f) TREGDME-LiBETI (see

Table 1 in the Experimental section of the manuscript for sample acronyms). Chronoamperometry

carried out by applying a voltage of 30 mV; EIS performed by applying an alternate voltage signal with

amplitude of 10 mV within the frequency range from 500 kHz to 100 mHz. Temperature: 25°C

S 4

0 20 40 60 80 1000

800

1600

2400

3200

4000

4800

5600

0 10 200

10

20T(Li+) = 0.32±0.03

(a)C

urr

ent

/ m

A

Time / minute

I0= 2620 mA

ISS= 1930 mA-Z

Im /

W

ZR / W

T = 0

T = 90 min

Ri

Qi

Re

0 20 40 60 80 1000

800

1600

2400

3200

0 10 200

10

20T(Li+) = 0.36±0.04

(b)

Cu

rren

t /

mA

Time / minute

I0= 2080 mA

ISS= 1270 mA

-ZIm

/ W

ZR / W

T = 0

T = 90 min

Ri

Qi

Re

0 20 40 60 80 1000

400

800

1200

1600

0 10 20 30 40 50 600

10

20

30

40

50

60T(Li+) = 0.38±0.04

(c)

Curr

ent

/ m

A

Time / minute

I0= 810 mA

ISS

= 498 mA

-ZIm

/ W

ZR / W

T = 0

T = 90 min

Ri

Qi

Re

0 20 40 60 80 1000

600

1200

1800

2400

3000

3600

0 10 200

10

20T(Li+) = 0.46±0.05

(d)

Curr

ent

/ m

A

Time / minute

I0= 2160 mA

ISS= 1310 mA

-ZIm

/ W

ZR / W

T = 0

T = 90 min

Ri

Qi

Re

0 20 40 60 80 1000

800

1600

2400

3200

4000

4800

0 10 200

10

20T(Li+) = 0.43±0.04

(e)

Curr

ent

/ m

A

Time / minute

I0= 2140 mA

ISS

= 1680 mA

-ZIm

/ W

ZR / W

T = 0

T = 90 min

Ri

Qi

Re

0 20 40 60 80 1000

800

1600

2400

3200

0 10 200

10

20T(Li+) = 0.39±0.04

(f)

Cu

rren

t /

mA

Time / minute

I0= 1950 mA

ISS= 1160 mA

-ZIm

/ W

ZR / W

T = 0

T = 90 min

Ri

Qi

Re

Figure S2. Chronoamperometry profiles and Nyquist plots (insets) of EIS measurements before and

after polarization related to the calculation of the lithium transference number (t+) [1]. Measurements

performed on Li/Li symmetrical cells using (a) DEGDME-LiTFSI, (b) TREGDME-LiTFSI, (c)

DEGDME-LiFSI, (d) TREGDME-LiFSI, (e) DEGDME-LiBETI, and (f) TREGDME-LiBETI (see

Table 1 in the Experimental section of the manuscript for sample acronyms). Chronoamperometry

carried out by applying a voltage of 30 mV; EIS performed by applying an alternate voltage signal with

amplitude of 10 mV within the frequency range from 500 kHz to 100 mHz. Temperature: 50°C

S 5

Figure S3 shows the Nyquist plots related to EIS measurements upon aging of Li/Li

symmetrical cells using DEGDME-LiTFSI (panel a), TREGDME-LiTFSI (panel b),

DEGDME-LiFSI (panel c), TREGDME-LiFSI (panel d), DEGDME-LiBETI (panel e), and

TREGDME-LiBETI (panel f). The interface resistance related to the lithium/electrolyte

interface has been evaluated by nonlinear least square (NLLS) fit using the Boukamp software

[4,5] and reported in Figure 4 of the manuscript. The above mentioned Re(RiQi)Q or

Re(RiQi)(RQ) equivalent circuit was used for the analysis, leading to chi-square (χ2) values

below 10−4 which confirmed the accuracy of the method. The figure reveals an impedance

response depending on the electrolyte formulation.

Figure S4 shows lithium stripping/deposition voltammetry tests on Li/Cu cells using (a)

DEGDME-LiTFSI, (b) TREGDME-LiTFSI, (c) DEGDME-LiFSI, (d) TREGDME-LiFSI, (e)

DEGDME-LiBETI, and (f) TREGDME-LiBETI (see Table 1 in the Experimental section of

the manuscript for sample acronyms). CV clearly reveals a polarization and a

stripping/deposition magnitude (current) strongly depending on the adopted salt/solvent

combination. Furthermore, the graphs generally indicate a low polarization value ranging from

about 0.05 V to 0.15 V, thus suggesting the suitability of the studied electrolyte for battery

application.

S 6

Figure S3. Nyquist plots related to EIS measurements performed during storage of Li/Li symmetrical

cells using (a) DEGDME-LiTFSI, (b) TREGDME-LiTFSI, (c) DEGDME-LiFSI, (d) TREGDME-

LiFSI, (e) DEGDME-LiBETI, and (f) TREGDME-LiBETI (see Table 1 in the Experimental section of

the manuscript for sample acronyms). EIS performed by applying an alternate voltage signal with

amplitude of 10 mV within the frequency range from 500 kHz to 1 Hz.

0 100 200 3000

100

200

300(a) 3 h 6 h 9 h

12 h 15 h 18 h

21 h 24 h 3 d

6 d 8 d 10 d

13 d 15 d 17 d

20 d 23 d 27 d

29 d

-ZIm

/ W

ZRe / W

0 100 200 300 4000

100

200

300

400(b) 3 h 6 h 9 h

12 h 15 h 18 h

21 h 1 d 3 d

5 d 7 d 9 d

10 d 12 d 14 d

16 d 19 d 21 d

23 d 26 d 28 d

30 d

-ZIm

/ W

ZRe / W

0 150 300 450 6000

150

300

450

600

(c)

-ZIm

/ W

ZRe / W

3 h 6 h 9 h

12 h 15 h 18 h

21 h 1 d 4 d

6 d 8 d 11 d

13 d 15 d 18 d

20 d 22 d 25 d

27 d 29 d

0 100 200 300 4000

100

200

300

400(d)

-ZIm

/ W

ZRe / W

3 h 6 h 9 h

12 h 15 h 18 h

21 h 1 d 3 d

5 d 8 d 10 d

12 d 14 d 16 d

18 d 21 d 23 d

25 d 28 d 30 d

0 300 600 9000

300

600

900(e)

-ZIm

/ W

ZRe / W

3 h 6 h 9 h

12 h 15 h 18 h

21 h 1 d 4 d

6 d 8 d 11 d

12 d 14 d 15 d

18 d 20 d 22

24 d 25 d 27 d

0 200 400 6000

200

400

600 3 h 6 h 9 h

12 h 15 h 18 h

21 h 24 h 1 d

3 d 4 d 7 d

9 d 11 d 14 d

16 d 18 d 21 d

23 d 25 d 28 d

30 d

-ZIm

/ W

ZRe / W

(f)

S 7

-0.4 -0.3 -0.2 -0.1 0.0 0.1 0.2 0.3 0.4-6

-3

0

3

6

-0.4 -0.2 0.0 0.2 0.4 0.6-18

-12

-6

0

6

Curr

en

t /

mA

Potential vs. Li+/Li / V

(a)

Cu

rrent / m

A

Potential vs. Li+/Li / V

1st

cycle

-0.4 -0.3 -0.2 -0.1 0.0 0.1 0.2 0.3 0.4-2

-1

0

1

2

-0.4 -0.2 0.0 0.2 0.4

-20

-15

-10

-5

0

5(b)

Curr

en

t /

mA

Potential vs. Li+/Li / V

1st

cycle

Cu

rrent / m

A

Potential vs. Li+/Li / V

-0.4 -0.3 -0.2 -0.1 0.0 0.1 0.2 0.3 0.4

-300

-200

-100

0

100

200

-0.4 -0.2 0.0 0.2 0.4-300

-200

-100

0

100(c)

Curr

en

t /

mA

Potential vs. Li+/Li / V

1st

cycle

Cu

rrent / m

A

Potential vs. Li+/Li / V

-0.4 -0.3 -0.2 -0.1 0.0 0.1 0.2 0.3 0.4-200

-150

-100

-50

0

50

100

150

-0.4 -0.2 0.0 0.2 0.4-200

-100

0

100(d)

Curr

en

t /

mA

Potential vs. Li+/Li / V

1st

cycle

Cu

rrent / m

A

Potential vs. Li+/Li / V

-0.4 -0.3 -0.2 -0.1 0.0 0.1 0.2 0.3 0.4-0.4

-0.2

0.0

0.2

0.4

-0.4 -0.2 0.0 0.2 0.4

-10

-8

-6

-4

-2

0(e)

Curr

en

t /

mA

Potential vs. Li+/Li / V

1st

cycle

Cu

rrent / m

A

Potential vs. Li+/Li / V

-0.4 -0.3 -0.2 -0.1 0.0 0.1 0.2 0.3 0.4-4

-2

0

2

4

-0.4 -0.2 0.0 0.2 0.4-15

-10

-5

0

(f)

Curr

en

t /

mA

Potential vs. Li+/Li / V

1st

cycle

Cu

rrent / m

A

Potential vs. Li+/Li / V

Figure S4. Lithium stripping/deposition voltammetry tests of Li/Cu cells using (a) DEGDME-LiTFSI,

(b) TREGDME-LiTFSI, (c) DEGDME-LiFSI, (d) TREGDME-LiFSI, (e) DEGDME-LiBETI, and (f)

TREGDME-LiBETI (see Table 1 in the Experimental section of the manuscript for sample acronyms).

CVs performed within -0.3 and 0.3 V using a scan rate of 0.1 mV s-1.

S 8

Electrolyte R0 (Ω) χ2 I0 (A) Rss (Ω) χ2 Iss (A) t+

DEGDME-LiTFSI 133±2 7×10−5 1.72×10−4 109±1 8×10−5 1.58×10−4 0.51±0.05

TREGDME-LiTFSI 450±5 8×10−5 5.13×10−5 497±5 6×10−5 4.20×10−5 0.62±0.06

DEGDME-LiFSI 211±2 9×10−5 1.05×10−4 182±2 9×10−5 9.28×10−5 0.54±0.05

TREGDME-LiFSI 76.7±0.4 2×10−5 1.93×10−4 82.0±0.8 4×10−5 1.51×10−4 0.67±0.07

DEGDME-LiBETI 300±1 8×10−5 6.60×10−5 561±2 8×10−5 4.01×10−5 0.82±0.08

TREGDME-LiBETI 157±1 2×10−5 8.90×10−5 214±1 3×10−5 6.79×10−5 0.79±0.08

Table S1. Data used for the determination of the lithium transference number using equation

(1) at 25 °C (see discussion of Figure 2 in the manuscript). R0, I0, Rss and Iss are the interphase

resistances (at middle-high frequencies) and the current of the initial state and the steady state

reported in Figure S1, respectively, while χ2 is the chi-square value obtained for the

determination of the resistances by NLLS fit of the corresponding Nyquist plots. The error on

the final t+ number was estimated as 10% based on the error on resistances and possible

instrumental uncertainty.

S 9

Electrolyte R0 (Ω) χ2 I0 (A) Rss (Ω) χ2 Iss (A) t+

DEGDME-LiTFSI 7.3±0.1 6×10−5 2.62×10−3 2.5±0.2 4×10−5 1.93×10−3 0.32±0.03

TREGDME-LiTFSI 6.8±0.1 7×10−6 2.08×10−3 2.3±0.2 6×10−5 1.27×10−3 0.36±0.04

DEGDME-LiFSI 21±1.1 9×10−5 8.10×10−4 17.7±0.4 2×10−5 4.98×10−4 0.38±0.04

TREGDME-LiFSI 4.4±0.1 6×10−6 2.16×10−3 2.3±0.1 6×10−5 1.31×10−3 0.46±0.05

DEGDME-LiBETI 7.3±0.1 7×10−6 2.14×10−3 2.3±0.2 3×10−5 1.68×10−3 0.43±0.04

TREGDME-LiBETI 6.3±0.1 1×10−5 1.95×10−3 2.5±0.1 4×10−5 1.16×10−3 0.39±0.04

Table S2. Data used for the determination of the lithium transference number using equation

(1) at 50 °C (see discussion of Figure 2 in the manuscript). R0, I0, Rss and Iss are the interphase

resistances (at middle-high frequencies) and the current of the initial state and the steady state

reported in Figure S2, respectively, while χ2 is the chi-square value obtained for the

determination of the resistances by NLLS fit of the corresponding Nyquist plots. The error on

the final t+ number was estimated as 10% based on the error on resistances and possible

instrumental uncertainty.

S 10

References

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numbers in polymer electrolytes, Polymer. 28 (1987) 2324–2328. doi:10.1016/0032-

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[2] L. Carbone, D. Di Lecce, M. Gobet, S. Munoz, M. Devany, S. Greenbaum, J. Hassoun,

Relevant Features of a Triethylene Glycol Dimethyl Ether-Based Electrolyte for Application

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[5] B. Boukamp, A package for impedance/admittance data analysis, Solid State Ionics. 18–

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