LiMn_2O_4 has a phase transition at room temperautre, which is caused by Jahn-Teller distortion. DC resistivity of LiMo_2O_4 shows an anomaly at the transition temperature, while no such anomaly is observed in samples with excess lithium. X-ray diffraction patterns of LiMn_2O_4 reveal 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.
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