Supporting Information

Synthesis of an Imidazolium Functionalized Imide Based Electrolyte

Salt and its Electrochemical Performance Enhancement with

Additives in Li-Ion Batteries

Faiz Ahmed a, Md. Mahbubur Rahman a, Sabuj Chandra Sutradhar a, Nasrin Siraj Lopa a,

Taewook Ryu a, Sujin Yoon a, Inhwan Choi a, Jaewoong Kim a, Yongcheng Jin b, *, Whangi Kim a, *

a Department of Energy and Materials, Konkuk University, Chungju 27478, South Korea

b Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences,

Xinyuan Rd, Laoshan Qu, Qingdao Shi, Shandong Sheng, 266000, China

*Authors to whom correspondence should be addressed: E-Mail: jinyc@qibebt.ac.cn (Y. Jin),

wgkim@kku.ac.kr (W. Kim).

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Synthesis of sulfurisocyanatidic fluoride (FSO2NCO)

For the synthesis of sulfurisocyanatidic fluoride (FSO2NCO), a mixture of sulfurisocyanatidic

chloride (1 mol) and antimony trifluoride (0.33 mol) was stirred for 48 h at 70 C. Then, the

reaction mixture was distilled at 80 C to obtain a pure, colorless, and acidic liquid of FSO2NCO.

Fig. S1 shows the 19F NMR spectra of FSO2NCO and the corresponding analytical data are

presented as follows:

FSO2NCO. Yield = 86%, 19F-NMR (CDCl3; 298 K): = 62 (s, 1F) ppm.

Fig. S1. 19F NMR spectra of FSO2NCO.

Synthesis of sulfamoyl fluoride (FSO2NH2)

Sulfamoyl fluoride (FSO2NH2) was synthesized according to a reported procedure [S1]. Briefly,

400 mmol of dried formic acid was added dropwise into the as-synthesized FSO2NCO (270

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mmol) at 0 C. (Safety note: formic acid formed a violent reaction with FSO2NCO with the

evolution of CO2, CO, and HF). Then, the reaction mixture was stirred for 24 h at 25 C. After

completing the reaction, FSO2NH2 was obtained by distillation at 70 C using a vacuum pump

and liquid nitrogen, which was purified by repeated trap-to-trap distillation method at reduced

pressure. Fig. S2 displays the 1H NMR, 19F NMR, and FTIR spectra of FSO2NCO. The

corresponding analytical data are summarized as follows:

FSO2NH2. Yield = 60%, 1H-NMR (DMSO-d6; 298 K): = 8.12 (s, 2H) ppm, 19F-NMR (DMSO-

d6; 298 K): = 59 (s, 1F) ppm. FTIR (KBr disc): = 3585 (NH2 asym. stretch), 3565 (NH2

asym. stretch), 1761 (NH2 def.), 1387 (SO2 sym. stretch), 1201 (O=S=O sym. stretch), 900 (SN

stretch), 776 (SF stretch) cm-1.

Fig. S2. (a) 1H NMR, (b) 19F NMR, and (c) FTIR spectra of FSO2NH2.

Synthesis of 3-(3-(chlorosulfonyl)propyl)-1-methyl-1H-imidazol-3-ium chloride (CSPMIC)

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CSPMIC was synthesized by the chlorination reaction of MSIC with thionyl chloride (SOCl2).

In details, SOCl2 (130.0 mmol) was added dropwise into MSIC (12.5 mmol) at 0 ºC under

nitrogen atmosphere. Then, the reaction mixture was refluxed for 12 hours. Subsequently, the

unreacted SOCl2 was sequentially removed by evaporation and washed several times with

toluene. Fig. S3 depicts the 1H NMR of CSPMIC, and the corresponding analytical data are

presented as follows:

CSPMIC. 1H-NMR (DMSO; 298 K): = 9.2 (s, H), 7.8 (s, H), 7.7 (s, H), 4.25-4.35 (t, 2H), 3.85

(s, 3H), 2.4-2.6 (t, 2H), 2.0-2.2 (m, 2H) ppm.

Fig. S3. (a) 1H NMR of CSPMIC.

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2 3 4 5 6 7-10

-5

0

5

10

15

Curr

ent (

mA)

Potential, V (vs. Li/Li+)

LiFSI (1 M) LiTFSI (1 M)

Fig. S4. LSV plot of LiFSI and LiTFSI electrolytes (1 M each) at a scan rate of 25 mV/s.

Preparation of asymmetric dummy cells and coin cells

Fig. S 5a shows the schematic structure of the dummy cell. For the preparation of dummy cells, a

LiFePO4 and a carbon black coated FTO electrodes were sandwiched using a surlyn polymer

film (thickness 60 m) as a spacer and sealant. The LiFePO4 film was deposited onto the FTO

electrode (active area: 0.15 cm2; thickness: ca. 10 m) by doctor blade method using a

homemade paste of LiFePO4, and dried at 90 C in vacuum. In the paste, LiFePO4, carbon black,

and PVDF was 86, 5, and 9 wt%, respectively. Similarly, graphite film was deposited onto FTO

electrodes (active area: 0.15 cm2; thickness: ca. 12 m) using a homemade paste with the

graphitic carbon and PVDF of 90 and 10 wt%, respectively. Prior to the sandwich, both

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electrodes were dipped into the electrolyte solutions for 15 min. After assembling the dummy

cells, the electrolyte solution was injected through the pre-drilled hole on one FTO side and

sealed with scotch tape as temporary sealing.

Fig. S 5b displays the schematic structure of the coin cell. For the preparation of coin cell, a

graphite coated Cu foil, a LiFePO4 coated Al foil, and celgard film was used as anode, cathode,

and separator respectively. Prior assembling the cell, both the anode and cathode were soaked

into 0.3 mL electrolyte solutions for 15 min. The cells were assembled under the inert

atmospheric conditions in a glove box.

Fig. S5. Schematic illustration of the asymmetric (a) dummy and (b) coin cell.

Measurement of ionic conductivity

The Li+ ion conductivity () of electrolytes was measured according to the following equation

[S2].

σ= lR s a

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where, l is the distance between two asymmetric electrodes, Rs is bulk resistance, and a is the

area of the electrode.

Measurement of transference number (tLi+)

The tLi+ of electrolytes was measured using dummy cells. A positive polarization of 10 mV was

applied between the electrodes of the dummy cells and measured the steady-state current (Iss) and

initial current (Io) by chronoamperometry. The EIS spectra of the dummy cells were also

measured before and after polarization to obtain the initial resistance (Ro) and steady-state

resistance (Rss). Finally, the tLi+ of electrolytes was calculated according to the following equation

[S3].

tLi+¿=

I ss(∆ V− I0 R 0)I 0(∆V −I ss R ss)

¿

Details of EIS spectra

The EIS spectra of LiFSMIPTFSI, LiFSMIPTFSI+LiFSI, and LiFSMIPTFSI+LiTFSI

electrolytes based dummy cells with variable temperature are shown in Fig. S6. All the EIS

spectra exhibited a depressed semicircle at the high-frequency region corresponding to the

resistance for Li+ movement through the electrodes materials (RSEI). The second semicircle at the

mid-frequency region indicates the charge transfer resistance (RCT) during the electrochemical

reactions and the third semicircle at the low-frequency region corresponds to the Warburg

diffusion resistance (Zw) at the electrode. Rs is the bulk resistance induced by the movement of

Li+ ions through the electrolyte [S4].

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Fig. S6. EIS spectra of (a) LiFSMIPTFSI, (b) LiFSMIPTFSI+LiFSI, and (c)

LiFSMIPTFSI+LiTFSI electrolyte based dummy cells with varying temperature. All the EIS

spectra were measured under open circuit condition in the frequency range of 0.1 Hz to 0.1 MHz

with an AC amplitude of 5 mV.

Fig. S7. Equivalent circuit model to fit the EIS spectra of dummy cells.

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Fig. S8. Negative charge delocalization in FSMIPTFSI anion.

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Fig. S9. Successive EIS spectra of (a) LiFSMIPTFSI, (b) LiFSMIPTFSI+LiFSI, and (c)

LiFSMIPTFSI+LiTFSI electrolyte based dummy cells at 30 C. The sequence of EIS

measurements were as follows: 10 × CV scans (potential range between 0 to +6 V, scan rate 25

mV/s); relaxation at 0 V (1 min). This sequence of electrochemical stability testing was repeated

10 times.

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Fig. S10. CD plots of LIB coin cells with different electrolytes at 1 C and 30 C.

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Fig. S11: FE-SEM image of bare graphite anode.

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Fig. S12: (a) Selected area of graphite anode of LiFSMIPTFSI electrolyte based LIB (inset

shows the wt% of elemental C, N, O, F, and S), and (b-f) EDS elemental mapping of C, O, F, S,

and N, respectively. The graphite anode was recovered after 500 CD cycles.

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Fig. S13: (A) Selected area of graphite anode of LiFSMIPTFSI+LiFSI electrolyte based LIB

(inset shows the wt% of elemental C, N, O, F, and S), and (B-F) EDS elemental mapping of C,

O, F, S, and N, respectively. The graphite anode was recovered after 500 CD cycles.

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Fig. S14: (A) Selected area of graphite anode of LiFSMIPTFSI+LiTFSI electrolyte based LIB

(inset shows the wt% of elemental C, N, O, F, and S), and (B-F) EDS elemental mapping of C,

O, F, S, and N, respectively. The graphite anode was recovered after 500 CD cycles.

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Table S1. The specific capacity of some recently reported electrolytes along with the developed electrolytes in this research for LIBs.

Cathode Anode Electrolyte Additive C rateSpecific Capacity(mAhg-1)

Ref.

LiFePO4 graphite 1.1 M LiPF6 (EC+EMC) LiFSI+LiBOB 1 116 [S5]

LiFePO4 graphite

1 M LiPF6 (EC+DMC) VC 1 128

[S6] 1 M LiPF6 (EC+DMC) LiTFSI 1 132

1 M LiPF6 (EC+DMC) LiFSI 1 134

1 M LiPF6 (EC+DMC) LiFTFSI 1 131

LiFePO4

Li0.25FePO

4

1 M LiFSI (EC/DMC) - 0.1 139

[S7] 1 M LiFTSI (EC/DMC) - 0.1 143

1 M LiFPFSI (EC/DMC) - 0.1 145

1 M LiFNFSI (EC/DMC) - 0.1 142LiFePO4 Li4Ti5O12 1 M LiPF6 (EC+DMC) - 0.1 155 [S8]

LiNi0.5Mn1.5O4 graphite 1 M LiFSI (EC/DMC) - 0.2 130 [S9]

LiCoO2 graphite 1 M LiTFSI (EC+ADN) LiBOB 0.08 108 [S10]

LiCoO2 graphite 1 M LiFSI (EC/DEC) - 0.1 130 [S11] 1 M LiFSI (EC/DEC) DFOB 0.1 132

LiNi1/3Co1/3Mn1/3O2 graphite 1 M LiPF6 (EC/EMC) VC 0.2 135 [S12]

1 M LiPF6 (EC/EMC) VC+PS 0.2 132

LiCoO2 MCMB

1.1 M LiPF6 (EC+EMC) - 0.2 128

[S13] 1 M LiPF6 (EC+DEC) TPP 0.2 126

1 M LiPF6 (EC+DEC) TPP+VEC 0.2 130

1 M LiPF6 (EC+DEC) TPP+BP 0.2 134

1 M LiFSMIPTFSI - 0.1/0.2/0.3/1 141/130/121/95

This workLiFePO4 graphite

1 M LiFSMIPTFSI LiFSI 0.1/0.2/0.3/1 160/150/138/115

1 M LiFSMIPTFSI LiTFSI 0.1/0.2/0.3/1 150/141/129/105EC = ethylene carbonate, EMC = ethyl methyl carbonate, LiBOB= Lithium bis-oxalatoborate, DMC = dimethyl

carbonate, VC = vinylene carbonate, LiFTFSI = lithium (fluorosulfonyl) (trifluoromethanesulfonyl)imide, LiFPFSI

= lithium(fluorosulfonyl)(pentafluoroethanesulfonyl)imide LiFNFSI = lithium (fluorosulfonyl)

(nonafluorobutanesulfonyl)imide, ADN = adiponitrile, DEC = diethylene carbonate, DFOB =

difluoro(oxalato)borate, PS = 1,3- propane sultone, MCMB = mesocarbon microbeads, TPP = triphenyl phosphate,

VEC = vinyl ethylene carbonates, BP = biphenyl.

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