Supporting Information
Dendrite- and Oxygen-Proof Protective Layer for Lithium Metal in Lithium-Oxygen Batteries
Won-Jin Kwak,a Jiwon Park,b Trung Thien Nguyen,a Hun Kim,a Hye Ryung Byon,b Minchul Jangc and Yang-Kook Sun*a
a.Department of Energy Engineering, Hanyang University, Seoul 04763, Republic of Korea.
b.Department of Chemistry, Korea Advanced Institute of Science and Technology (KAIST), and KAIST Institute for
NanoCentury, Daejeon 34141, Republic of Korea
c.Batteries R&D, LG Chem Ltd., Daejeon 34122, Republic of Korea
*Correspondence author: [email protected]
Electronic Supplementary Material (ESI) for Journal of Materials Chemistry A.This journal is © The Royal Society of Chemistry 2019
Supplementary Figures
Fig. S1 Scanning electron microscopy (SEM) images of (A) Li metal, (B–D) NCL-coated Li metal,
and (E, F) Nafion-coated Li metal without Al2O3. Inset photographs in Fig. S1 (A, B, and D) are
representative of Li metal, NCL-coated Li metal, and Nafion-coated Li metal, respectively.
200 μm
20 μm
200 μm
2 μm
A B
C D
200 μm 20 μm
E F
Fig. S2 SEM image of a composite protective layer (CPL, Al2O3-PVdF mixture)-coated Li metal.
There are no morphological differences between NCL and CPL.
20 μm
Fig. S3 Gas evolution profiles during charge of Li-O2 cells with (A, C) CPL and (B, D) NCL for Li-
metal protection with 1 M LiTFSI in TEGDME. A TEMPO (0.3 M) redox mediator was
additionally included in (C) and (D). Before charging process, discharge was performed at a
fixed capacity of 1000 mAh g–1. The blue and red dotted lines, and grey dashed lines denote
the O2, CO2, and H2 evolution profiles, respectively. The horizontal dashed line refers to an e–
/O2 gas evolution with the rate of 2.
0 200 400 600 800 10000.0
0.1
0.2
0.3
0.4
0.5
0.6
Specific capacity (mAh g-1)
e-/O
2 = 2.00
NCL coated Li metal + TEMPO
O2
CO2
H2
Gas e
vo
luti
on
(mm
ol A
-1 m
in-1)
0 200 400 600 800 10000.0
0.1
0.2
0.3
0.4
0.5
0.6
Specific capacity (mAh g-1)
e-/O
2 = 2.00
CPL coated Li metal
O2
CO2
H2
Gas e
vo
luti
on
(mm
ol A
-1 m
in-1)
A B
0 200 400 600 800 10000.0
0.1
0.2
0.3
0.4
0.5
0.6
Specific capacity (mAh g-1)
e-/O
2 = 2.00
CPL coated Li metal + TEMPO
O2
CO2
H2
Gas e
vo
luti
on
(mm
ol A
-1 m
in-1)
C D
0 200 400 600 800 10000.0
0.1
0.2
0.3
0.4
0.5
0.6
Specific capacity (mAh g-1)
e-/O
2 = 2.00
NCL coated Li metal
O2
CO2
H2
(mm
ol A
-1 m
in-1)
Gas e
vo
luti
on
Fig. S4 The OEMS gas analysis of Li–O2 cell where a naked Li metal was used during discharge
with a fixed capacity of 1000 mAh g–1. This Li anode was replaced with a CPL-coated Li metal
in an Ar-filled glove box after discharge, and charge process was continuously carried out. (A)
Cumulative evolution of O2 gas and (B) gas evolution profiles during charge. The blue, red and
grey dotted lines in (B) denote the O2, CO2, and H2 evolution profiles, respectively. The dashed
line in (A) indicates the ideal amount of O2 gas. The horizontal dashed line in (B) refers to an
e–/O2 gas evolution with the rate of 2.
0 200 400 600 800 10000.0
0.1
0.2
0.3
0.4
0.5
0.6
Specific capacity (mAh g-1)
e-/O
2 = 2.00
Pre-discharge with Li metal and
recharge with CPL coated Li metal
O2
CO2
H2
Gas
ev
olu
tio
n
(mm
ol
A-1 m
in-1)
0 200 400 600 800 10000.0
5.0
10.0
15.0
20.0
O2 (5.29 μmol)
Specific capacity (mAh g-1)
Ideal line
CPL coated Li metal (for recharge)
after pre-discharge using Li metal
n
(μ
mo
l O
2)
A B
Fig. S5 UV-Vis spectra of discharged electrodes (0.1 mA – 20 h) immersed in a Ti4+ solution for
titration of Li2O2. The electrodes were made of Li metal, NCL-coated Li metal, or CPL (PVdF-
based)-coated Li metal.
380 420 460 500 540 580 620 660 700
0.0
0.2
0.4
0.6
Cathode before discharge (absence of Li2O
2)
Amount of Li2O
2 on discharged cathode
Li metal
NCL coated Li metal
CPL (PVdF base) coated Li metal
Ab
so
rba
nc
e (
a.u
.)
Wavelength (nm)
Fig. S6 ATR-FTIR spectra of the protective layers in Li-O2 batteries before and after cycle tests
to check the stability of (A) PVdF-based CPL-coated Li metal, and (B) NCL-coated Li metal in
Li-O2 batteries. All the data were used without fitting to exhibit changes in the peaks clearly.
1600 1400 1200 1000 800
PVdF (in CPL) on Li metal
before test
after 1st cycle
Inte
ns
ity (
a.u
.)
Wavenumbers (cm-1)
A
*** ** * * *
*
* PVDF
1600 1400 1200 1000 800
Nafion (in NCL) on Li metal
before test
after 1st cycle
Inte
ns
ity (
a.u
.)
Wavenumbers (cm-1)
B* Nafion
*
* *
**
*
Fig. S7 (A) SEM analysis of PEO-based CPL (Al2O3-PEO mixture)-coated Li metal. This layer has
the same morphology as NCL and PVdF-based CPL. (B) UV-Vis spectra of discharged electrodes
(0.1 mA – 20 h) immersed in a Ti4+ solution for titration of Li2O2. The electrodes were made of
Li metal, NCL-coated Li metal, or CPL (PEO-based)-coated Li metal.
(C) C 1s XPS spectra and (D) ATR-FTIR spectra of the protective layers in Li-O2 batteries before
and after cycle tests to check the stability of PEO-based CPL-coated Li metal in Li-O2 batteries.
All the data were used without fitting to exhibit changes in the peaks clearly.
20 μm
1600 1400 1200 1000 800
PEO (in CPL) on Li metal
before test
after 1st cycleIn
ten
sit
y (
a.u
.)
Wavenumbers (cm-1)
D
*
* PEO
**** * *
***
296 294 292 290 288 286 284 282
PEO (in CPL) on Li metal
before test
after 1st cycle
Inte
ns
ity (
a.u
.)
Binding Energy (eV)
C 1sC
C-O / C-C
380 420 460 500 540 580 620 660 700
0.0
0.2
0.4
0.6
Ab
so
rba
nc
e (
a.u
.)
Wavelength (nm)
Amount of Li2O
2 on discharged cathode
Li metal
NCL coated Li metal
CPL (PEO base) coated Li metal
Cathode before discharge (absence of Li2O
2)
BA
Fig. S8 Voltage profiles during galvanostatic cycling test of a Li-O2 pouch cell using (A) Li metal
and (B) Nafion-coated Li metal as anodes at the same conditions as the pouch cell in Fig. 4b.
Poorer cycling performance of Li-O2 pouch cell using Nafion-coated Li metal (Fig. S8B) than
that of Li metal without coating material (Fig. S8A) results from mechanically unstable
protective layer (NL without Al2O3) which causes deterioration of the cell due to abnormal
accumulation of decomposed byproduct on the metal surface.
0 400 800 1200 1600 20001.0
2.0
3.0
4.0
5.0
1st cyc 2nd cyc 3rd cyc
5th cyc 7th cyc 8th cyc
Vo
lta
ge
(V
)
Specific capacity (mAh g-1)
Nafion coated Li metal
0 400 800 1200 1600 20001.0
2.0
3.0
4.0
5.0
1st cyc 2nd cyc 3rd cyc
5th cyc 7th cyc 10th cyc
15th cyc 17th cyc
Vo
lta
ge
(V
)
Specific capacity (mAh g-1)
Li metal without protective layerA B
Fig. S9 SEM images of (A) Nafion-coated Li metal without Al2O3 and (B) CPL (PVdF-based)-
coated Li metal after the cycling test of Li-O2 cells.
A B
400 μm 400 μm