3
In situ X R D of C -L iFe1/4M n1/4C o1/4N i1/4P O 4 durin g first charg e
C om parison w ith pure C -LiFePO 4
C -LiFePO 4
Phase1 C -L iM n 1/4F e1/4C o 1/4N i1/4P O 4
3. Soft X-ray absorption spectroscopy study of charged cathode m aterials
(bulk inform ation)
Fluorescent d etecto r(su rface in fo rm atio n )
Electron yield
1. Tim e-resolved XRD study of charged cathode m aterials
S am pHleesaitnin g capillary
Sam ples in capillary
Average structural inform ation (long range order) during heating
+
V o lt a g e ( vVs . L i/ L i)
N o rm a liz e d in te n s ity (a . u .)
in situ XAS
5 .0
(III)
4 .5
(II)
4 .0
(I)
6 0 m A h g -1
3 .5
2 6 m A h g -1
0 20 40 60 80 100 120 140 160 180
Using Synchrotron Based in situ X-ray Techniques and Transmission Electron Microscopy to Study Electrode Materials for Lithium Batteries
X. Q. Yang, K. W. Nam, X.J. Wang, Y.N. Zhou, H. S. Lee, O. Haas, L. Wu, and Y. Zhu Brookhaven National Lab. Upton, NY11973, USA
Oxygen release
Oxygen release
W hen x= 0.5 (50% of SOC) in LixMO2
Li0.5M (3.5+)O 2 (layered, R-3m ) Li0.5M (3.5+)1.0O 2 (disordered spinel, Fd3m ) ; no oxygen loss Li0.5M (3.5+)1.0O 2 (disordered spinel, Fd3m ) Li0.5M (2.5+)1.0O 1.5 (rock salt, Fm 3m ) + 0.25 O 2 ; oxygen release!!
C apacity ( m A h g-1 )
Cut-off voltage: ~ 5.0 V, C/7 rate
Edge shift toward higher energy position
increase in oxidation state
2 .0
Fe K-edge
2.0
M n K-edge
Al current collector
A c tiv e m a te ria l
Cu current collector
Li foil
2
Synchrotron based X-ray diffraction and absorption spectroscopy during heating
Studies on therm al decom position (therm al abuse tolerance) of cathode m aterials
(500~1000eV)
H e a tin g
Ultra high vacuum
Com bination of these techniques will clearly provide valuable inform ation about therm al stability of various types of cathodes m aterials and help designing cathode m aterials with superior therm al abuse tolerance !!
K . W . N am , X. Q . Yang et al, Electrochem istry C om m unication, in press (2009).
6
Thermal stability study of layered cathode materials (safety related issue)
9 3 m A h g -1
126 m A hg-1
0.5
142 m A hg-1
151 m A hg-1
171 m A h g-1
180 m A h g-1
6560
0 .0 7710
7720
7730
0.0 8320
8330
8340
8350
8360
Energy ( eV )
Three voltage plateaus at ~ 3.6, 4.2 and 4.7 V Redox reactions of Fe2+/Fe3+, M n2+/M n3+ and Co2+/Co3+. Voltage plateau over ~ 4.9V M ostly electrolyte decom position. Electronic structural changes follow ing the lithium extraction q uite w ell to balance the electrical neutrality.
Temperature induced structural changes of charged layered cathode materials
Transition metal layer
Layered LiMO2
Spinel-type LiM2O4
Rocksalt MO
lithium layer
Phase 2 Phase 3
H (311) H (121)
Two phase re a c tio n
No significant solid solution
re g io n
Existence of solid solution
re g io n s
Appearance of Interm ediate
W hen x= 0.33 (67% of SOC) in LixMO2 Li0.33M (3.67+)O 2 (layered, R-3m ) Li0.33M (3.21+)1.0O 1.77 (disordered spinel, Fd3m ) + 0.115 O 2 ; oxygen release!! Li0.33M(3.21+)1.0O1.77 (disordered spinel, Fd3m ) Li0.33M(2.33+)1.0O1.33 (rock salt, Fm3m ) + 0.22 O2 ; oxygen release!!
To be presented at the 4th Southern China Li-ion Battery Top Forum –CLTF2009 Shenzhen, China, May 25th, 2009
Combining in situ synchrotron XAS and XRD techniques to do diagnostic studies of battery materials and components at or near operating conditions
More charged state, more thermally unstable. Released oxygen causes safety problems (e.g., thermal runaway) by reacting with flammable electrolytes.
1 .5
Before charge
8 m A h g -1
1 7 m A h g -1
2 6 m A h g -1
1 .0
3 5 m A h g -1
5 3 m A h g -1
7 0 m A h g -1
0 .5
8 8 m A h g -1 1 6 8 m A h g -1
1.5
Before charge
In situ cell
Position sensitive detector (PSD)
XRD setup
In situ cell
Mylar sheet Bolt holes
Gasket
Separator
X-ray w in d o w
Diffraction pattern
Incident X-rays In situ cell
X19A & X18B (XAS) and X14A & X18A (XRD) at National Synchrotron Light Source (NSLS)
Ionization Detectors