Film-shaped sol-gel Li Ti O electrode for Lithium

Film-shaped sol-gel Li Ti O electrode for Lithium

Film-shaped sol-gel Li4Ti5O12 electrode for
Lithium-ion microbatteries
Jadra Mosa, John F. Vélez, Miguel Gómez, Israel Lorite, Noemi
Arconada, M. Aparicio
Instituto de Cerámica y Vidrio (ICV)
Consejo Superior de Investigaciones Científicas (CSIC)
Campus de Cantoblanco (Madrid, Spain)
Film-shaped sol-gel Li4Ti5O12 electrode for
Lithium-ion microbatteries
Strategic Japanese-Spanish Cooperative Program
Osaka Prefecture University // Instituto de Cerámica y Vidrio (CSIC)
Spanish Science and Innovation Ministry. Reference: PLE2009-0074 (ACI-PLAN E)
Objectives
All-solid-state Li-ion microbatteries (~ 10 µm)
• Development of all battery components by both teams
• Preparation of two-layer and three-layer structures with electrolytes and
electrodes developed during the project.
• Evaluation of charge-discharge properties.
Anode
Current Collector
Cathode
Cathode
Current Collector
Electrolyte
Anode
Substrate
Li4Ti5O12 electrodes
Introduction
Li4Ti5O12 electrodes
Li4Ti5O12 + 3Li+ + 3e-
Anode
Current Collector
Discharge
Charge
Anode
Li7Ti5O12 E = 1.55 V
Substrate
Face-centered cubic spinel structure
Advantages
• Zero-strain Li insertion anode
• Excellent reversibility
• Long cycle life
• Rapid charge and discharge
Disadvantages
• Low specific capacity (175 mA h / g)
• High voltage (1.55 V)
M. Vijayakumar et al. J. Power Sources 196 (2011) 2211–2220
Introduction
Li4Ti5O12 electrodes
Anode
Current Collector
Conventional preparation procedure
Anode
Substrate
Solid-state reaction
• Lithium and titanium salts
• Thermal treatments: high temperatures and long times
• Problems with the preparation of thin coatings
Our alternative
Sol-Gel process
• Excellent composition control
• Lower thermal treatment temperature
• Shorter treatment times
• Lower particles growth
• Easy for preparing thin coatings
Experimental
Li4Ti5O12 electrodes
Sol-gel synthesis
Compositions
Li/Ti = 4/5, 5/5 and 6/5
EtOH
LiAc
HAc
Ti(C3H7O)4
H2O (HCl)
Sol
pH ~ 6.0
Viscosity ~ 2.5 cP
J.A. Mergos et al. Mater. Charact. 60 (2009) 848-653
Experimental
Li4Ti5O12 electrodes
Coating preparation (multilayer system)
Gold sputtering (60 nm) on Quartz
Dipping
(5 – 45 cm min-1)
Glass or Quartz
Silicon
Thermal treatment
500 – 800 °C
Au/Quartz
Results
Li4Ti5O12 electrodes
Spectral Ellipsometric measurements
(WVASE32, M-2000UTM, J.A. Co., Woollam)
Four-layer coatings on Au/Quartz (700°C, 4 hours)
Gold layer: 50 – 60 nm
Li/Ti = 4/5 coating
Li/Ti = 5/5 coating
Li/Ti = 6/5 coating
Thickness (e) (nm): 450 nm
Thickness (e) (nm): 560 nm
Thickness (e) (nm): 385 nm
• Final thickness depends on different sol synthesis and coatings preparation parameters
Results
Li4Ti5O12 electrodes
FE-SEM / EDX (Hitachi S-4700)
Four-layer Li/Ti = 6/5 coatings on Au/Quartz (700°C, 4 hours)
• Homogeneous and well-bonded layer
• Thickness between 350 and 400 nm, in agreement with ellipsometry results
Results
Li4Ti5O12 electrodes
Grazing-angle X-ray diffraction (Siemens D-5000)
One-layer coatings (700°C, 4 hours)
Li4Ti5O12
TiO2 (Rutile)
Intensity (a.u.)
Li/Ti = 6/5
Li/Ti = 5/5
Li/Ti = 4/5
10
20
30
40
50
60
2 Theta (degree)
• Rutile (TiO2) in Li/Ti = 4/5 and 5/5 compositions
• Li/Ti = 6/5 composition: traces of TiO2
70
80
Results
Li4Ti5O12 electrodes
Confocal Micro-Raman Microscopy
(Witec alpha-300R)
Four-layer coatings on Au/Quartz
(700°C, 4 hours)
• Li/Ti =4/5 composition: higher content of Rutile
Intensity (a.u.)
• Three compositions show Li4Ti5O12 peaks
Li/Ti= 4/5
Li/Ti= 5/5
Li/Ti= 6/5
• Depth profile (steps of 50 nm): composition
preserved along the four layers
Rutile
150
300
450
600
-1
Wavenumber (cm )
750
Results
Li4Ti5O12 electrodes
Grazing-angle X-ray diffraction (Siemens D-5000)
One-layer Li/Ti = 6/5 coatings (different temperatures and times)
Li4Ti5O12
TiO2 (Rutile)
Intensity (a.u.)
700ºC 4h
700ºC 1h
600ºC 4h
600ºC 1h
500ºC 4h
500ºC 1h
10
20
30
40
50
2 Theta (degree)
• Low crystallization at 500 °C
• Li4Ti5O12 between 500 – 700 °C
• TiO2 (Rutile) at 700 °C
60
70
80
Results
Li4Ti5O12 electrodes
X-Ray Photoelectron Spectroscopy (XPS)
% at. elements
100
80
Coating 600ºC, 1h
60
O
Si
40
Ti
20
Li
0
0
200
400
600
800
1000
1200
etch time / s.
• Higher lithium and lower titanium concentration at the surface
• High coating homogeneity in general (lithium excess)
Results
Li4Ti5O12 electrodes
Galvanostatic cycling
(Multichannel Potentiostat VMP3, Biologic)
1M LiPF6 in 1:1 (w:w) ethylene
carbonate (EC) and dimethyl carbonate
(DMC)
Ar atmosphere
Li foils (RE and CE)
Coated sample (WE)
Results
Li4Ti5O12 electrodes
Galvanostatic cycling (Potentiostat VMP3, Biologic)
Four-layer coatings on Au/Quartz (700°C, 4 hours)
2.0
1.9
Second discharge-charge profiles
(17 µA cm-2)
1.8
• Li/Ti = 6/5 composition: flatter
plateau around 1.55 V
Voltage (V)
1.7
1.6
• Discharge capacities similar to
theoretical value (610 mA h cm-3)
1.5
1.4
Li/Ti = 4/5
Li/Ti = 5/5
Li/Ti = 6/5
1.3
1.2
1.1
0
100
200
300
400
500
Capacity (mA h cm-3)
600
700
800
Results
Li4Ti5O12 electrodes
Galvanostatic cycling (Potentiostat VMP3, Biologic)
Four-layer coatings on Au/Quartz (700°C, 4 hours)
800
700
• Li/Ti = 6/5 composition: almost
no capacity decay after 40 cycles
Capacity (mA h cm-3)
600
Capacity performance (17 µA cm-2)
500
• Crystalline structure is crucial
for a good behaviour
400
300
Li/Ti = 4/5
Li/Ti = 5/5
200
Li/Ti = 6/5
100
0
0
5
10
15
20
25
30
35
40
Cycle Number
J. Mosa, J.F. Vélez, I. Lorite, N. Arconada, M. Aparicio. Journal of Power Sources, 205 (2012) 491-494.
Conclusions
Anode
Current Collector
Anode
Substrate
• Film-shaped Li4Ti5O12 anodes with thickness up to 1.2 µm
have been prepared on Au/SiO2 substrates
• Almost pure Li4Ti5O12 phase has been synthesized using an
excess of lithium precursor
• Preliminary electrochemical characterization
excellent behavior in charge-discharge tests.
shows
an
All-solid-state Li-ion microbatteries (~ 10 µm)
Thank you for your attention
Conclusions
All-solid-state Li-ion microbatteries (~ 10 µm)