Supplementary Information Gassing in Li4Ti5O12-based batteries and its remedy Yan-Bing He1,2, Baohua Li1, Ming Liu1, Chen Zhang3, Wei Lv1,3, Cheng Yang1, Jia Li1, Hongda Du1, Biao Zhang2, Quan-Hong Yang1,3*, Jang-Kyo Kim2 & Feiyu Kang1* 1
Key Laboratory of Thermal Management Engineering and Materials, Graduate School at Shenzhen,
Tsinghua University, Shenzhen 518055, China. 2 Department of Mechanical Engineering, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong. 3 School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China. Correspondence and requests for materials should be addressed to Q.-H.Y. (email:
[email protected],
[email protected]) and F.Y.K. (email:
[email protected]).
-S 1 -
Supplementary Figures and Table
a
b
500nm
30
40
50
(333)
(400) (331)
(311) (220)
60
2(degrees)
(533) (622) (444) (551)
(531)
(440)
(333)
(400) (331)
(222)
20
(220)
10
2
(311)
(111)
Intensity (a.u.)
(111)
Rutile TiO
(222)
c
70
80
90
Supplementary Figure S1. Morphology and structure of the as-prepared LTO. (a) SEM image. (b) TEM image. (c) XRD patterns. Microstructure and morphology of the samples were examined using field emission scanning electron microscopy (FE-SEM, HITACH S4800, HITACH Co., Japan) and transmission electron microscopy (TEM, JOEL JEM-2100F, Japan).
-S 2 -
10
20
50
(002) (310) (221) (301) (112) (311)
(220)
(111) (201)
40
60
70
(202) (212) (321) (400)
(211)
30
( 200 )
( 102 )
(110)
Intenisity(a.u.)
Rutile TO2
80
(degree)
Supplementary Figure S2. XRD patterns of the as-prepared rutile TiO2.
-S 3 -
90
Supplementary Table S1. Gases generated when soaking the Li4Ti5O12 and rutile TiO2 in various solvents and electrolyte solution (under Conditions A and B). Electrolytes and solvents
Material
EC
Li4Ti5O12
DEC
Temperature /o C
CO2 wt%
C2H4 wt%
C2H6 wt%
C3H6 wt%
H2 wt%
CH4 wt%
CO wt%
50 oC
100.0
/
/
/
/
/
/
Li4Ti5O12
50 oC
100.0
/
/
/
/
/
/
DEC
Li4Ti5O12
25 oC
100.0
/
/
/
/
/
/
1M/LiPF6+EC
Li4Ti5O12
50 oC
100.0
/
/
/
/
/
/
1M/LiPF6+DEC
Li4Ti5O12
50 oC
100.0
/
/
/
/
/
/
1M/LiPF6+EMC+ DMC+EC
Li4Ti5O12
50 oC
100.0
/
/
/
/
/
/
DEC
Rutile TiO2
50 oC
100.0
/
/
/
/
/
/
DEC
Rutile TiO2
25 oC
100.0
/
/
/
/
/
/
-S 4 -
(333)
(331)
(311) (400) (222)
30
40
50
60
e 40
60
2(degrees)
(533) (622) (444) (551)
(531)
(333)
(440)
20
(331)
(222)
(220)
(111)
(400)
(311)
20
2
anatase TiO2
(220)
(111)
Intensity (a.u.)
Rutile TiO
a
80
c
b
100nm 100nm
d
e 100nm
Supplementary Figure S3. Structure and morphology of the as-prepared LTO/C. (a) XRD patterns. (b) SEM image. (c-e) TEM images.
-S 5 -
a G
D
1000
1200 1400 1600 1800 -1 Raman Shift / cm
2000
b 102 100 ~1.0 wt%
99 Weight / %
Weight loss / %
100
98
98
H2O + gas adsorbed
~3.0 wt% Carbon
96
97 94
96 92 0 100 100 200200 300 400 500 600 700 800 300 400 500 o Temperature / C o
600
700
Temperature / C
Supplementary Figure S4. State and content of carbon in the as-prepared LTO/C. (a) Raman spectra. (b) TG curve. Thermogravimetric analysis (TGA) of LTO/C was conducted in air at a heating rate of 5 oC min−1 from room temperature to 800oC using Netzsch STA449F3 system (Germany) to roughly estimate the carbon content of LTO/C. Raman spectroscopy of LTO/C was performed using a Raman Spectrometer (Renishaw Invia Reflex, Britain) with a 514 nm Ar-ion laser.
-S 6 -
800
Ti 2p
e
Li4Ti5O12
Li4Ti5O12
2p3/2
2p1/2
O 1s
j
C-O (ROCOOLi)
C-OLi Li4Ti5O12 C-O-C C=O
o
TiO2
d
i
c
h
C 1s
l
a
f
k
464
462
460
458
456 538
2
Cg sp
m
g
Binding energy (eV)
c-o
n
b
466
C-F(PVDF) RCO3Li C=O O-C=O
TiO2
TiO2
468
C-OLi C-H(PVDF) 3 c-o-C Cd sp
536
534
532
530
Binding energy (eV)
528 294
292
290
288
286
284
282
Binding energy (eV)
Supplementary Figure S5. Ti 2p, O 1s and C 1s XPS spectra of LTO under different conditions. (a, f, k) As-prepared LTO. (b, g, l) LTO soaked under Conditions A (DEC at 50 oC). (c, h, m) LTO soaked under Condition B (1 M LiPF6/EC+DMC+EMC at 50 oC). (d, i, n) LTO in fully charged LTO/NCM battery stored under Condition D. (e, j, o) LTO in LTO/NCM battery cycled under Condition E. Note that the LTO batteries tested under Conditions D and E were fully discharged before XPS examination.
X-ray photoelectron spectroscopy (XPS) analyses of LTO were conducted with a Physical Electronics PHI5802 instrument using X-rays magnesium anode (monochromatic Kα X-rays at 1253.6 eV) as the source. The C 1s peak for the graphitic carbon, which was set at 284.8 eV, was used as a reference for the calibration of XPS peaks. The Ti 2p spectrum of the as-prepared LTO consists of a peak of Ti 2p3/2 at 458.6 eV and a peak of Ti 2p1/2 at 464.4 eV (Supplementary Fig. S5a), which are in good agreement with the Ti4+ ions of Li4Ti5O121. Whereas, a new couple Ti 2p peaks at 458.2 (Ti 2p3/2) and 463.7 eV (Ti 2p1/2) appeared (Supplementary Fig. S5b), after the LTO was soaked by DEC at 50oC. These two peaks can be assigned
-S 7 -
to TiO22,3. The peak at 529.6 eV in the O 1s XPS spectra also proves the formation of TiO2 (Supplementary Fig. S5g)2. The Ti 2p peaks shift to high binding energy after the LTO was soaked under Condition B (Supplementary Fig. S5c). The Ti 2p spectra consists of a couple main peaks of Ti 2p3/2 at 458.9 eV and Ti 2p1/2 at 464.6eV and shoulder peaks of Ti 2p3/2 at 459.7 eV and Ti 2p1/2 at 465.4 eV. The shoulder peaks could be attributed to the Li2TiF6 species. Ti 2p XPS spectra of LTO after storage under Condition D presents one couple of peaks at 459.9 eV assigned to Ti 2p3/2 component and at 465.6 eV of Ti 2p1/2 component (Supplementary Fig. S5d). Note that Ti 2p XPS peaks shift to much higher binding energy than that of the as-prepared LTO, which may be attributed to the inelastic scattering of the products of the interfacial reaction between LTO and electrolyte. XPS profiles after the LTO cycled under Condition E present similar results to that of the LTO after storage under Condition D (Supplementary Fig. S5e, S5j and S5o). The Ti 2p XPS spectra of LTO after cyclic tests consist of a peak of Ti 2p3/2 at 459.6 eV and a peak of Ti 2p1/2 at 465.3 eV. It is found that the Ti 2p peak shift is smaller than that of LTO after storage. XPS peak intensity and TEM image all indicate that the surface layer on LTO after cyclic test under Condition E is thicker than that LTO stored under Condition D (Fig. 3e-f).
-S 8 -
(PVDF) C-F (ROCO Li) C-O
Li2CO3 CH x
(C-O-C)
g
(ROLi) C-O
i h
LTO
Absorbance / arb. units
Absorbance / arb. units
υC=O
LTO
2
h
i
g
2000
1800
1600
1400
1200
1000
Wavenumber / cm
800
900
600
800
700
-1
600
Wavenumber / cm
-1
LTO
(PVDF) C-F
b
C=O CHx
(C-O-C)
c
(ROLi) C-O
f e d c
LTO
Absorbance / arb. units
Absorbance / arb. units
Li2CO3
e f d a
b a
2000
1800
1600
1400
1200
1000
Wavenumber / cm
800
600
900
800
700
600 -1
Wavenumber / cm
-1
Supplementary Figure S6. FTIR spectra of LTO and LTO/C under different conditions. (a) PVDF. (b) As prepared LTO. (c) LTO soaked under Condition A. (d) LTO soaked under Condition B. (e) LTO in fully charged NCM/LTO battery stored under Condition D. (f) LTO in NCM/LTO battery cycled under Condition E. (g) As prepared LTO/C. (h) LTO/C in fully charged NCM/(LTO/C) battery stored under Condition D. (i) LTO in NCM/(LTO/C) battery cycled under Condition E. Note that the LTO and LTO/C batteries tested under Conditions D and E were fully discharged before FTIR examination. Fourier transform infrared spectroscopy (FT-IR) spectrometer (Bruker VERTEX 70) was applied to test the FTIR spectra of LTO and LTO/C under different conditions.
-S 9 -
a
[Li1/3Ti5/3]
Li
c
b
e
O
f
d
g
Supplementary Figure S7. Structural models of the unit cell and (222), (400), (111) planes of spinel L4Ti5O12. (a) A unit cell of spinel LTO (space group Fd3m), in which part of lithium ions, located at (8a) sites, oxygen ions, located at (32e) sites and hybrid [Li1/3Ti5/3], located at (16d) sites, are denoted as balls with different colors. Note that the diameters of color balls do not represent actual sizes of different components. (b) (222) plane is composed of [Li1/3Ti5/3] layers. (400) plane is composed of by lithium ions layers (c) and oxygen ions and [Li1/3Ti5/3] hybrid layers (d). (111) plane is composed of lithium ions layers (e), oxygen ions layers (f) and [Li1/3Ti5/3] layers (g).
-S 10 -
(533) (622) (444) (551)
(440) (531)
(333)
(331)
(311) (222)
(220)
(111)
Intenisity(a.u.)
e
(400)
f
Phase change
d c b a 10
20
30
40
50
60
70
80
90
(degree)
Supplementary Figure S8. XRD patterns and TEM image of LTO under different conditions. XRD patterns of the as-prepared LTO (a), LTOs soaked under Conditions A (b) and Condition B (c) at 50 oC, LTO in fully charged NCM/LTO batteries stored under Condition D (d) and cycled under Condition E (e). (f) HRTEM images of LTO soaked under Condition B. Note that the LTO batteries tested under Conditions D and E were fully discharged before the XRD and TEM examinations.
-S 11 -
(440)
(533) (622) (444) (551)
(531)
(511)
(331)
(400)
(311) (222)
(220)
(111)
Intenisity(a.u.)
c b a 10
20
30
40
50
60
(degree)
70
80
90
Supplementary Figure S9. XRD patterns of LTO/C. (a) As-prepared LTO/C. (b) and (c) LTO/C in fully charged NCM/(LTO/C) batteries stored under Condition D and cycled under Condition E, respectively. Note that the LTO/C batteries tested under Conditions D and E were fully discharged before XRD examinations.
-S 12 -
Ti 2p
O 1s
2p1/2
d
2p3/2
C-OLi CH(PVDF) 3 c-o-CCd sp
C 1s
C-O-C C-OC-OLiC=O
(ROCOOLi)
c-o
C-F(PVDF)
h
C=O O-C=O
l
2
Cg sp
C
Li4Ti5O12
Li4Ti5O12
Li4Ti5O12
c
g
b
f
k
a 468
ROCOOLi
j
e 466
464
462
460
458
456 538
Binding energy (eV)
i 536
534
532
Binding energy (eV)
530
528 294
292
290
288
286
284
282
Binding energy (eV)
Supplementary Figure S10. Ti 2p, O 1s and C 1s XPS spectra of LTO and LTO/C. (a, e, i) As-prepared LTO. (b, f, j) As-prepared LTO/C. (c, g, k) LTO/C in fully charged NCM/(LTO/C) battery stored under Condition D. (d, h, i) LTO/C in NCM/(LTO/C) battery cycled under Condition E. Note that the LTO/C batteries tested under Conditions D and E were fully discharged before XPS examinations. Supplementary Fig. S10a-l show the Ti 2p, O 1s and C 1s XPS spectra of the LTO/C before and after storage and cyclic tests. The Ti 2p XPS profile of the as-prepared LTO/C consists of a peak of Ti 2p3/2 at 459.2 and a peak of Ti 2p1/2 at 464.8, respectively. It is seen that the peaks shift to higher binding energy. The O 1s peaks also shift to higher binding energy (Supplementary Fig. S10f). An obvious O 1s XPS peak at 532.2eV and C 1s peak at 290.5 eV assigned to the CO32- are observed, which may be ascribed to the CO2 and H2O absorbed on the surface of the coated carbon of LTO/C. Here note that the LTO/C materials were roasted at 80 oC for 24h before the battery assembly to drive away the absorbed CO2 and H2O. The C 1s spectra also present that C-O species and carbon exist on the surface of LTO/C (Supplementary Fig. S10j). After the LTO/C batteries were stored and cycled, the Ti 2p XPS spectra consist of a peak of Ti 2p3/2 at 459.7eV and a peak of Ti 2p1/2 at 465.4 eV (Supplementary Fig. S10c-d), which is similar with that of the uncoated LTO after cyclic tests.
-S 13 -
References (1)Dedryvere, R.; Foix, D.; Franger, S.; Patoux, S.; Daniel, L.; Gonbeau, D. J Phys Chem C 2010, 114, 10999. (2)HURAVLEV, J. F.; KUZNETSOV, M. V.; GUBANOV, V. A. J. Electron. Spectrosc. Relat. Phenom. 1992 38, 169. (3)CARDINAUD, C.; LEMPERIERE, G.; PEIGNON, M. C.; JOUAN, P. Y. Appl. Surf. Sci. 1993, 68, 595.
-S 14 -
