Ke. Thomas et al., Measurement of the entropy of reaction as a function of state of charge indoped and undoped lithium manganese oxide, J ELCHEM SO, 148(6), 2001, pp. A570-A575
Potentiometric measurements of the entropy and enthalpy of reaction at 298
K as a function of state of charge for LiMn2O4 and LiAl0.2Mn1.8O4-deltaF0.2
are presented. Lithium resides on nearest neighbor or next-nearest neighbo
r sublattices in lithium manganese oxide. The entropy of reaction is positi
ve when a sublattice is nearly empty and negative when a sublattice is near
ly full, and ranges from 0.25 to -0.35 mV/K in the undoped spinel and from
0.1 to -0.4 mV/K in the doped spinel. The potentiometric method includes a
correction for self-discharge. Potentiometric measurements of entropy are c
ompared to calorimetric measurements. The potentiometric method is most acc
urate for thermally thin cells, while calorimetric methods require large ce
lls to improve the signal-to-noise ratio. (C) 2001 The Electrochemical Soci
ety.