Reversible multi-electron redox chemistry of...... Jinhu Yang,5 Man-Fai Ng,3 Yong-Sheng Hu,4 Yong Yang,2* Michel Armand,4 and Kian Ping Loh,1* 1 Department of Chemistry, Centre for

In the format provided by the authors and unedited.

© 2017 Macmillan Publishers Limited, part of Springer Nature. All rights reserved.

Page 1 of 32

Supplementary Materials

Reversible Multielectron Redox Chemistry of π-Conjugated N-containing

Heteroaromatic Molecule-based Organic Cathodes

Chengxin Peng,1† Guo-Hong Ning,1† Jie Su,1† Guiming Zhong,2 Wei Tang,1

Bingbing Tian,1 Chenliang Su,1 Dingyi Yu,1 Lianhai Zu5, Jinhu Yang,5 Man-Fai Ng,3

Yong-Sheng Hu,4 Yong Yang,2* Michel Armand,4 and Kian Ping Loh,1*

1 Department of Chemistry, Centre for Advanced 2D Materials and Graphene Research Centre, National

University of Singapore, 3 Science Drive 3, Singapore 117543

2 State Key Laboratory of Physical Chemistry of Solid Surfaces, Department of Chemistry, College of Chemistry

and Chemical Engineering, Collaborative Innovation Center of Chemistry for Energy Materials (iChEM),

Xiamen University, Xiamen 361005, China

3 Institute of High Performance Computing, Agency for Science, Technology and Research, 1 Fusionopolis Way,

#16-16 Connexis, Singapore 138632

4 Key Laboratory for Renewable Energy, Beijing Key Laboratory for New Energy Materials and Devices, Beijing

National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, School of

Physical Sciences, University of Chinese Academy of Sciences, Beijing 100190, China

5 Department of Chemistry, Tongji University, Siping Road 1239, Shanghai 200092, P. R. China

*Corresponding authors: Yong Yang (Y. Yang); Kian Ping Loh (K. Loh)

Email addresses: [email protected]; [email protected]

Reversible multi-electron redox chemistry of π-conjugated N-containing heteroaromatic

molecule-based organic cathodes

SUPPLEMENTARY INFORMATIONVOLUME: 2 | ARTICLE NUMBER: 17074

NATURE ENERGY | DOI: 10.1038/nenergy.2017.74 | www.nature.com/natureenergy 1

http://dx.doi.org/10.1038/nenergy.2017.74


http://www.nature.com/natureenergy


Page 2 of 32

Supplementary Figures

Supplementary Fig. 1 Cyclic voltammograms of 2Q- (left) and 3Q- based (right) organic electrodes in

1M LiTFSI-DOL/DME (1:1 in vol.) at a scan rate of 0.1 mV∙s-1.


SUPPLEMENTARY INFORMATION




Page 3 of 32

Supplementary Fig. 2 Cycling performance of 2Q- and 3Q-based organic electrodes at loading

currents of 400 mA g-1(1C) and 800 mA g-1(2C). a, Cycling performance of 2Q-based electrode at

loading current of 400 and 800 mA g-1.The reversible capacity of 2Q-based electrode run change from

372 mA g-1 and keep at and stay constant at about 359 mA h g-1 after 200 cycles under a current of 400

mA g-1, resulting in a stable cycling and well good capacity retention of 96%. As the loading current is

increased to 800 mA g-1 (2C), the specific capacities can reach to 300 mAh g-1 which is only reduced

to 290 mAh g-1 after 200 cycles with negligible capacity loss per cycle. b, Cycling performance of 3Q-

based electrode at loading current of 400 and 800mA g-1. The lithium storage capacity of the 3Q-based

electrode changes from 395 mAh g-1 at the first cycle under a current of 400 mAg-1 (1C) to 324 mAh g-1

after 200 cycles, resulting in a high capacity retention of 82.1%. When the loading current is increased

to 800 mA g-1 (2C), the reversible capacity reaches 318 mAh g-1 initially and after 200 cycles, decreases

to 263 mAh g-1, with a capacity of 82.5% and a coulombic efficiency of 100%.






Page 4 of 32

0 5 10 15 200

100

200

300

Ener

gy d

ensi

ty (W

h K

g-1)

Current (C)

3Q 2Q

Supplementary Fig. 3 Energy density of organic battery based on 2Q and 3Q at different current

loading (1C, 2C, 4C, 6C, 8C, 10C, 20C; 1C=400mA g-1).

10001

10

100

1000

Ener

gy d

ensi

ty (W

h K

g-1)

Power density (W Kg-1)

3Q 2Q

Supplementary Fig. 4 Energy density VS. Power density of the organic battery based on 2Q and 3Q.






Page 5 of 32

Supplementary Fig. 5 Galvanostatic charge–discharge curve of 3Q-based organic cathode with

different loading of active materials at a current of 400 mA g-1.

Supplementary Fig. 6 The capacity of 3Q-based organic cathode with different loading of active

materials at a current of 400 mA g-1.

0 80 160 240 320 4000.8

1.6

2.4

3.2

4.0 30 wt% 3Q in composites 45 wt% 3Q in composites 60 wt% 3Q in composites

V

olta

ge /

(V v

s. Li

/Li+ )

Specific capacity / mAh g-1

Discharge curve

0

100

200

300

400

500

90%75%60%45%30%Spec

ific

capa

city

/ m

Ah

g-1

X content of 3Q in composites15%






Page 6 of 32

0 10 20 30 40 500

100

200

300

400

500

Discharge Charge

Spe

cific

cap

acity

/ m

Ah

g-1

Cycle number / N

Current: 400 mA g-1

0

20

40

60

80

100

Coulombic efficiency

Coulom

bic efficiency (%)

Supplementary Fig. 7 Cycling performance of 3Q-based organic cathode with 45 wt% loading of active


0 10 20 30 40 500

100

200

300

400

Spe

cific

cap

acity

/ m

Ah

g-1

Cycle number / N

Discharge Charge

0

20

40

60

80

100

Coulombic efficiency

Current: 400 mA g-1

Coulom

bic efficiency (%)

Supplementary Fig. 8 Cycling performance of 3Q-based organic cathode with 60 wt% loading of active







Page 7 of 32

Supplementary Fig. 9 The photograph of the pellets made of 2Q (left) and 3Q (right).

Supplementary Fig. 10 The SEM images (side view) of the pellets made of 2Q (left) and 3Q (right).

Supplementary Fig. 11 The instrument set-up for the electrical conductivity measurement.






Page 8 of 32

-40.0 -20.0 0.0 20.0 40.0

-1.0x10-10

-5.0x10-11

0.0

5.0x10-11

1.0x10-10

Cur

rent

/ A

Voltage / V

y = a + b*xslope b = 1.83826*10-12

R-square: 0.98789

Supplementary Fig. 12 I-V characterization curve of 2Q.

-40 -20 0 20 40-1.0x10-9

-8.0x10-10

-6.0x10-10

-4.0x10-10

-2.0x10-10

0.02.0x10-10

4.0x10-10

6.0x10-10

8.0x10-10

1.0x10-9

Cur

rent

/ A

Voltage / V

y = a + b*xslope b = 1.44647*10-11

R-square: 0.99882

Supplementary Fig. 13 I-V characterization curve of 3Q.






Page 9 of 32

Supplementary Fig. 14 Ex situ 15N solid-state NMR spectra of electrode materials and the

corresponding lithiated species after cycling to various states of discharge. N1, N2, N3, N4 and N5

(marked in different colors) denote five kinds of N chemical shifts of in the 3Q during lithiation, which

indicated the corresponding lithiated structures of 3Q during the discharge processes.






Page 10 of 32

Supplementary Fig. 15 EPR spectra of the lithiated 3Q/Li cell when discharging to various states

of charge To obtain the EPR signal, electrodes cycled at various lithiated stages (different cut-off

voltage) are disassembled in an Ar-filled glovebox, then rinsed with dimethyl carbonate (DMC) and

dried in vacuum; the samples for the EPR measurements are obtained by scratching the powder from the

electrode and filling the powder in the EPR quartz tubes and sealed to test. EPR spectra are recorded on

a JEOL FA200 with X-band EPR spectrometer operating at 9.206 GHz. Microwave power was set to

1.00 mW. Sweeps were performed with 50 mT width and a center field of 329 mT. The field modulation

frequency was set to 100 kHz, and the modulation amplitude was 25.






Page 11 of 32

Supplementary Fig. 16 Schematic overview of the structural evolutions of 3Q-based battery

during the charge processes. The lithiated structures of 3Q-6Li evolve during the delithiation

processes. When the voltage reaches 2.5 V, the N2 and N3 resonance peaks grow as the N5 resonance

peak decreases, showing the recovery of 3Q-2Li and 3Q-3Li. At the end of the charging stage, the N1

signal returns to the original position at δ = −56 ppm, demonstrating the structural recovery of 3Q.

The reversible structures of 3Q-6Li during the charge process indicates the reversible nature of the

lithiation reactions of 3Q.






Page 12 of 32

Supplementary Fig. 17 Schematic of the structural evolution in a 3Q-based battery during

charging/discharge processes Based on the solid-state 15N NMR results, six lithiated structures evolve

from 3Q to 3Q-xLi (x=0, 1, 2, 3, 4, 5, 6) during the cell is discharged to 1.2 V. Among them, 3Q-Li, 3Q-

3Li and 3Q-5Li are in doublet state (i.e. having one unpaired electron). The radical is distributed equally

on the co-shared one-Li-bonded pyridinic nitrogen in the extended π-conjugated ring plane of 3Q-Li and

3Q-5Li, while 3Q-3Li exhibits 3-fold symmetry (i.e. 3 equivalent structures), and the radical will be

distributed on all pyridinic N within the extended π-conjugated system, resulting in the same 15N

resource.






Page 13 of 32

Supplementary Fig. 18 Schematic of the optimized structures for lithiated 3Q-xLi compounds at

different stages of lithiation. Side views are shown for the 3Q with out-of-plane Li.






Page 14 of 32

Supplementary Fig. 19 Comparison of alternative lithiated structures for 3Q-xLi, where x=2, 3, 4.

3Q-2Li, 3Q-3Li and 3Q-4Li are the most stable structures while the alternative 3Q-2Li’, 3Q-3Li’ and

3Q-4Li’ are less stable structures with energy higher by 0.89, 0.87 and 0.82 eV, respectively. Side views

are shown for the 3Q with out-of-plane Li. We note that for 3Q-xLi (x=2, 3, 4), there exist alternate

configurations 3Q-xLi' (x=2, 3, 4). Nevertheless, these alternate structures are less stable and have a

higher energy by about 0.8~0.9 eV than their counterparts, indicating that the structural evolution of 3Q

upon lithiation takes place by adopting the lowest energy structures of 3Q-xLi (x=0, 1, 2, 3, 4, 5, 6).






Page 15 of 32

Supplementary Fig. 20 Structural evolution of 3Q during lithiation as calculated from DFT

simulation. There are two alternative structures for 3Q-xLi (x=2, 3, 4), while the structures of 3Q-xLi

(x= 0, 1, 2, 3, 4, 5, 6) with blue arrows shows the lower energy level, which indicate the most possible

reaction pathway of 3Q upon lithiation.






Page 16 of 32

Supplementary Fig. 21 Calculated Mulliken atomic spin densities for the nitrogen atoms in 3Q-Li,

3Q-3Li and 3Q-5Li. They are in doublet state (1 unpaired electron). The atoms having the majority spin

densities are shown in red. On the right, the spin density isosurface (blue color) plots are shown.

Isovalue is set at 0.005. The spin densities spread around the π-conjugated molecules. The larger the

sphere, the higher the spin densities. The optimized 3Q-3Li is not exactly 3-folded symmetric. The 3

equivalent structures with spin densities are shown. The majority spin densities are found in the space

around the one-Li-bonded pyrazine N atoms.






Page 17 of 32

Supplementary Fig. 22 1H NMR (500 MHz, CF3COOD, 300 K) spectra of 3Q.

Supplementary Fig. 23 13C NMR (125 MHz, CF3COOD, 300 K) spectra of 3Q.






Page 18 of 32

4000 3500 3000 2500 2000 1500 1000 500

768 cm-1

3446 cm-1

1493 cm-1

1339 cm-1

1365 cm-1

1077 cm-1

757 cm-1

Tran

smita

nce

(a.u

.)

Wavenumber / cm-1

608cm-1

3Q

4000 3500 3000 2500 2000 1500 1000 500

3458 cm-1

1738 cm-1

1545 cm-1

1501 cm-1

1358 cm-1

1072 cm-1

785 cm-1

Tran

smita

nce

(a. u

.)

Wavenumber / cm-1

762 cm-1

2Q

Supplementary Fig. 24 FT-IR spectra of triquinoxalinylene (3Q) and diquinoxalinylene (2Q).






Page 19 of 32

Supplementary Fig. 25 The crystal structure for single-crystalline 3Q.

Supplementary Fig. 26 1H NMR (500 MHz, CDCl3, 300 K) spectra of 2Q.






Page 20 of 32

Supplementary Fig. 27 13C NMR (125 MHz, CDCl3, 300 K) spectra of 2Q.

Charge/discharge curve

Supplementary Fig. 28 Electrochemical properties of the graphene at a current of 400 mA g-1 The

cut-off voltage is set to above 1.2 V and thus the delivered capacity of graphene is estimated to be 49

mAh g-1 (current: 400 mA g-1).






Page 21 of 32

Supplementary Fig. 29 Schematic showing the structure of a prototype organic-based cathode/Li

pouch cell. The pouch cell are fabricated with a metal Li foil (typical size 55×110mm, thickness 0.58

mm) on both sides as the counter electrode, a glass microfiber membrane (Ø = 150mm, Whatman GF/D,

Aldrich) as the separator, and 1.0 mol∙L-1 LiTFSI-DOL/DME solution (Solvionic, France) as the

electrolytes. The working electrode is composed of organic molecules/graphene composites casting on

one side of aluminum foil. Nickel and aluminum cell terminals were welded on anode and cathode

electrodes by ultrasound, respectively. The pouch cell is assembled by warping both sides of lithium foil

anode with the working electrode and sandwich by a separator. All the cell components are assembled in

a laminated aluminum bag filled with 1.0 mol∙L-1 LiTFSI-DOL/DME electrolyte in an Ar-filled

glovebox.






Page 22 of 32

Supplementary Fig. 30 Characterization of the solid electrolyte interphase film formed on organic

electrode materials after cycling in ether-based electrolytes. (a-d), High resolution TEM images of

cycled organic electrode materials during delithiation (a) 10 cycles, (b) 500 cycles, (c) 2000 cycles and

(d) 5000 cycles; (e-j), High resolution synchrotron radiation photoemission spectroscopy (SRPES)

analysis of the organic electrode material along with (e) nitrogen, (f) fluoride, (g) lithium, (h) sulfur, (i)

carbon, and (j) oxygen using synchrotron radiation X-ray source (800 eV); k, Schematic of the solid

interface film formed in ether-based electrolytes along with the principal reaction products.






Page 23 of 32

Supplementary Fig. 31 Morphology of the as-prepared 3Q organic material.

Supplementary Fig. 32 HRTEM images of the fiber-like organic electrode material before (a) and after

the sample rotating by 30 degree (c).

Supplementary Fig. 33 HRTEM images of the organic electrode material after cycling in conventional

electrolyte for 10 cycles (a) and 500 cycles (b).






Page 24 of 32

0 20 40 60 80 1000

100

200

300

400

500

Spec

ific

capa

city

(mA

h g-1

)

Cycle number / N

0

20

40

60

80

100

Coulom

bic efficiency (%)

Supplementary Fig. 34 Cycling performance of the 3Q organic electrode in conventional

electrolytes. The organic electrode based on 3Q shows poor cycling performance due the dissolution of

the active material in the conventional electrolyte LiPF6-EC/DMC.






Page 25 of 32

Supplementary Fig. 35 High-resolution synchrotron radiation photoemission spectroscopy (SRPES)

analysis of the organic electrode material before cycling (a) nitrogen, (b) fluoride, (c) carbon, (d)

oxygen.

Supplementary Fig. 36 Deconvoluted C1s high-resolution synchrotron radiation photoemission

(SRPES) spectra of the organic electrode material using the synchrotron radiation X-ray source (400.0

eV).






Page 26 of 32

Supplementary Tables

Supplementary Table 1. Crystal data and structure refinement of compound 3Q

Compound 3Q

Crystal system Monoclinic Space group P21/c

a (Å) 19.3752(13) b (Å) 5.3895(4) c (Å) 20.8601(12) α (o) 90 β (o) 104.157(3) γ (o) 90

V (Å3) 2112.1(2) Z 4

Dcalcd (g cm-3) 1.584 μ (mm-1) 0.463 F(000) 1024

Parameters 307 Rint 0.0653

R1a [I > 2σ(I)] 0.0567

Rwb [I > 2σ(I)] 0.1092

GOFc 1.015

aR = ∑||Fo| − |Fc||/∑|Fo|. bRw = [∑[w(Fo2 – Fc

2)2]/∑w(Fo2)2]1/2. cGOF = {∑[w(Fo

2 – Fc2)2]/(n − p)}1/2

where Fc and Fc is the observed and calculated structure factor, respectively, n is the number of reflections, and p is total number of parameter refined.

Supplementary Table 2. The cycling performances of 2Q and 3Q-based batteries after 200 cycles at a

current of 400 mA g-1 (1C) and 800 mA g-1 (2C)

Current Initial capacity (mAh g-1)

Capacity after 200 cycles (mAh g-1)

Retention (%)

2Q 400 mA g-1 (1C) 372 359 96.4

800 mA g-1 (2C) 300 290 96.7

3Q 400 mA g-1 (1C) 395 324 82.1

800 mA g-1 (2C) 318 263 82.5






Page 27 of 32

Supplementary Table 3. The cycling performance of 2Q and 3Q-based batteries after 1,000 cycles at a

current of 1.6 mA g-1 (4C) and 3.2 mA g-1 (8C)

Current Initial capacity (mAh g-1)

Capacity after 1,000 cycles (mAh g-1)

Retention (%)

2Q 1.6 mA g-1 (4C) 271 260 95.9

3.2 mA g-1 (8C) 240 202 84.2

3Q 1.6 mA g-1 (4C) 291 289 99.3

3.2 mA g-1 (8C) 252 246 97.6

Supplementary Table 4. Rate capability values of 2Q- and 3Q-based batteries

Current Capacity for 2Q (mAh g-1) Capacity for 3Q(mAh g-1)

400 mA g-1(1C) 373 394

800 mA g-1(2C) 313 334

1.6 mA g-1(4C) 272 290

2.4 mA g-1(6C) 254 268

3.2 mA g-1(8C) 241 255

4.0 mA g-1(10C) 236 242

8.0 mA g-1(20C) 222 218






Page 28 of 32

Supplementary Table 5. Sum of electronic and zero-point energies and the binding energies (∆E)

in hartree (eV) calculated at the B3LYP/6-31+G (d, p) level in DME solvent. Spin states of s and d

stand for singlet and doublet, respectively.

Supplementary Table 6. Sum of electronic and thermal Gibb free energies in hartree (eV) of

optimized structures and the redox potentials (V) calculated at the B3LYP/6-31+G (d, p) level in

DME solvent. Spin states of s and d stand for singlet and doublet, respectively.






Page 29 of 32

Supplementary Notes

Supplementary Note 1. Energy density and power density of 2Q and 3Q

In the experiment, the maximum delivery capacity C maximum capacity and the average voltage V average can

be obtained

The energy density of the electrode can be simplified as,

Eelectrode = C maximum capacity × V average

If the auxiliary components of the battery, i.e. current collectors, electrolytes, separators and packing are

taken into consideration, the mass of the electrode is normally calculated to one-third of the totally mass

of battery components. Accordingly, the energy density of the batteries can be estimated as,

Ecell= Eelectrode/ 3

The energy density of the batteries VS. current is shown in Supplementary Fig. 3.

When the discharge time (t) is obtained, the power density of battery is estimated as, P cell = Ecell / t The Ragone plot is shown in Supplementary Fig. 4.

Supplementary Note 2. Electrical conductivity measurement for 2Q and 3Q

(i) Preparation of pellets made of 2Q and 3Q

To measure the electrical conductivity of organic cathodes 2Q and 3Q, the powders of the two

compounds are pressed into a pellet using a compressed module. The two pellets are made under the

same conditions: the weight of 2Q and 3Q are 30 mg, the pressure is ~ 15 MPa (Hydraulic Pellet Press,

Sepcac), and the press time is 5 min. As shown in Supplementary Fig. 9, the diameter of two pellets is

13 mm; From the SEM image in Supplementary Fig. 10, the thickness of the pellets made of 2Q and 3Q

are about 154 and 163 μm, respectively.

(ii) Electrical conductivity measurement






Page 30 of 32

The electrical conductivity of two organic materials was determined by measuring electron transport

through the pressed pellet of the material. The pellets are sandwiched by two stainless steel chips

connected to a Keithley 2400 instrument. The pellets between two stainless steel chips are pressed

tightly to ensure proper electrical contact (Supplementary Fig. 11). The transient current through the

pellets are measured as a function of voltage, from which the resistivity and conductivity of the organic

cathodes based on 2Q and 3Q can be obtained. As shown in Supplementary Fig. 12 and 13 , the slopes

of the I-V curve for 2Q and 3Q are calculated to be about 1.83826 × 10 -12 and 1.44647 × 10 -11 A ∙V-1,

respectively.

The electrical conductivity is calculated using the following formula:

Where

V: the magnitude of the applied voltage;

I: the magnitude of the current density;

S: the area of the pellet (two organic materials 2Q and 3Q), = 3.14× (0.013/2)2 = 0. 000132665

m2;

L: the thickness of the pellet (two organic materials 2Q and 3Q), L (2Q) = 0.000154 m, L (3Q) =

0.000163 m;

ρ: the resistivity of the pellet (two organic materials 2Q and 3Q);

σ: the electrical conductivity of the pellet (two organic materials 2Q and 3Q)

The electrical conductivity is calculated as follows:

σ (2Q) = 2. 13×10-12 S/m;

σ (3Q) = 1.78 ×10-11 S/m.






Page 31 of 32

Supplementary Note 3. Crystal Structure for 3Q

A yellow rod like single crystal of C24H12ClN12 (CCDC No. 1511841), approximate dimensions (0.088 x

0.136 x 0.355) mm3, was used for the X-ray crystallographic analysis. The X-ray intensity data were

measured at low temperature (T = 100 K ), using a four circles goniometer Kappa geometry, Bruker

AXS D8 Venture, equipped with a Photon 100 CMOS active pixel sensor detector. A Molybdenum

monochromatized ( = 0.71073 Å) X-Ray radiation was selected for the measurement. Frames were

integrated with the Bruker SAINT software [1] using a narrow-frame algorithm. Integration of the data

using a monoclinic unit cell yielded a total of 8847 reflections to a maximum θ angle of 25.72° (0.82 Å

resolution), of which 4031 were independent (average redundancy 2.195, completeness = 99.8%, Rint =

6.53%, Rsig = 9.58%) and 2619 (64.97%) were greater than 2σ (F2). The final cell constants of a =

19.3752(13) Å, b = 5.3895(4) Å, c = 20.8601(12) Å, β = 104.157(3) °, volume = 2112.1(2) Å3, are based

upon the refinement of the XYZ-centroids of 595 reflections above 20 σ (I) with 4.157° < 2θ < 47.77°.

Data were corrected for absorption effects using the multi-scan method implemented in the program

(SADABS) [2]. The calculated minimum and maximum transmission coefficients (based on crystal size)

are 0.9240 and 0.9800. The model was solved in the centrosymmetric space group P2(1)/c with the aid

of the software SHELXT [3], using a Dual Space method to solve the phase problem expanded in a

triclinic unit cell P1. Refinement of the structure was carried out by least squares procedures on

weighted F2 values using the SHELXL-version 2014/6 [4] included in the WinGx programs for Windows

[5]. Hydrogen atoms were localized on difference Fourier maps but then introduced in the refinement as

fixed contributors in idealized geometry with an isotropic thermal parameters fixed at 20 % higher than

those carbons atoms they were connected.






Page 32 of 32

Supplementary References

1. Saint Program included in the package software: APEX3 5, 2(2015).

2. Krause, L., Herbs-Irmer, R., Sheldrick, G. M. Stalke, D. SADABS. Ver. J. Appl. Crystallogr.

48(2015).

3. SHELXT Sheldrick, G. M. Integrated space-group and crystal-structure determination. Acta

Crystallogr., Sect. A A71, 3-8(2015).

4. SHELXTL Sheldrick, G. M. Ver. Acta Crystallographica. Sect C Structural Chemistry 71, 3-

8(2014).

5. WinGX Farrugia, L. J. J. Appl. Cryst. 32, 837-838(1999).





Documents

Reversible multi-electron redox chemistry of...... Jinhu Yang,5 Man-Fai Ng,3 Yong-Sheng Hu,4 Yong Yang,2* Michel Armand,4 and Kian Ping Loh,1* 1 Department of Chemistry, Centre for