ELECTROCHEMICAL INSERTION OF LITHIUM INTO PYRITE FROM NONAQUEOUS ELECTROLYTES AT ROOM-TEMPERATURE - AN IN-SITU FE K-EDGE X-RAY-ABSORPTION FINE-STRUCTURE STUDY
Da. Tryk et al., ELECTROCHEMICAL INSERTION OF LITHIUM INTO PYRITE FROM NONAQUEOUS ELECTROLYTES AT ROOM-TEMPERATURE - AN IN-SITU FE K-EDGE X-RAY-ABSORPTION FINE-STRUCTURE STUDY, Journal of physical chemistry, 99(11), 1995, pp. 3732-3735
The effects of lithium ion insertion on the structural and electronic
properties of FeS2 (pyrite) have been examined in situ by Fe K-edge X-
ray absorption fine structure (XAFS) using electrodes and electrolytes
similar to those found in conventional, ambient-temperature, primary
Li/FeS2 batteries. A substantial reduction in the amplitudes of the Fe
-S and Fe-Fe backscattering was observed as the amount of intercalated
lithium in the FeS2 lattice was increased from 0 to 2 Li+ equivalents
, (Li+)(eq). After the insertion of 2 (Li+)(eq) the second-shell Fe-S
interaction and the distant Fe-Fe interactions were no longer discerna
ble in the Fourier transform (FT) data, Curve-fitting analysis of the
k(chi)(3)(k) extended X-ray absorption fine structure for this latter
material yielded an average Fe-S distance, d(Fe-S) = 2.31 +/- 0.02 Ang
strom A, which is about 0.05 Angstrom A longer than d(Fe-S) in crystal
line pyrite. In addition, the X-ray absorption near-edge structure rev
ealed a rounding of the otherwise highly structured edge of FeS2 as th
e amount of inserted lithium was increased, This behavior is consisten
t with the formation of Fe1-xS and thus supports the assignment made o
n the basis of in situ Fe-57 Mossbauer effect spectroscopy of the same
system.