Phase Transition of LiMn₂O₄Spinel and its Application for Lithium Ion Secondary Battery

Abstract

LiMn2O4 has a phase transition at room temperature, which is caused by Jahn-Teller distortion. DC resistivity of LiMn2O4 shows an anomaly at the transition temperature, while no such anomaly is observed in samples with excess lithium. X-ray diffraction patterns of LiMn2O4reveal that the crystal structure changes from cubic at higher temperature to orthorombic, as a first approximation, at lower temperature. However, no differences in initial charge-discharge curve are observed, which means that the Jahn-Teller distortion has no effect on electrochemical characteristics. The authors have succeeded in mass-producing lithium ion secondary batteries with a manganese spinel cathode.

X-ray Study of the Spinel LiMn2O4 at Low Temperatures

“…To confirm this tendency, we performed similar measurements on a conventional X-ray diffractometer (λ = 1.5418 Å) at temperatures varying from 300 to 13 K. Figure presents the evolution of the cell parameters determined by cell-constrained profile refinement. The data show an anisotropic variation of the three parameters versus temperature as the cell parameters a and b become closer on cooling . However, our samples never become tetragonal when cooled below 60 K, contrary to other reports. , At 70 K, the apparent two peaks can be easily decomposed into three peaks in the same way as those in Figure (data recorded at 100 K) if we take into account the resolution of the instrument.…”

Reassessment of the Electronic‐Conduction Behavior above the Verwey‐Like Transition of Ni2+‐ and Al3+‐Doped LiMn2O4

“…Below the transition temperature, a mixture of cubic and tetragonal phases was suggested. However, it was later proved that LiMn 2 O 4 transforms from cubic to a single orthorhombic phase upon cooling through the transition temperature 2–4 . The similar feature referring to the Verwey transition was also observed in the inverse spinel Fe 3 O 4 5 .…”

Long-range ordering during delithiation of LiMn2O4 cathode material

“…2,3 If the average Mn oxidation state goes above 13.5, the lattice parameter decreases due to the smaller ionic radius of manganese in higher oxidation states. 4 Below room temperature, cubic LiMn 2 O 4 transforms to a distorted orthorhombic phase at 290 K. 5,6 At 230 K, the structure acquires an orthorhombic 3 6 3 6 1 superstructure with five independent Mn sites: two are occupied by well-defined Mn 41 ions and the other three are mixed-valence Mn 31 /Mn 41 sites. 7 The voltage vs. Li/Li 1 for a vLi|liq.…”