| Summary: | Dilithium manganese oxide (LMO) thin film was newly fabricated as an active material on a fluorinated-tin-oxide pre-coated glass electrode by a wet process. A stable LMO precursor solution was developed through the reaction of lithium and manganese acetates with butylamine in ethanol. A spin-coated precursor film was heat-treated at 500 °C in air for 0.5 h. The X-ray diffraction pattern indicates that the resultant film consists of layer-structured LMO crystals. The X-ray photoelectron spectra of LMO thin film suggests that the ratio of Mn<sup>3+</sup>/Mn<sup>4+</sup> is 1/4, and the chemical formula can be expressed as Li<sub>2</sub>MnO<sub>2.9</sub>. A device was assembled with O-deficient LMO and TiO<sub>2</sub> thin films as each active material, along with an electrolytic solution involving LiPF<sub>6</sub>. The charging voltages (2.67 and 1.45 V) of this device were recorded by applying a constant current of 0.2 mA and using 1-sun irradiation with no external power supply, respectively. The voltages delivered by this cobalt-free device were 0.63 and 0.13 V higher, respectively, than the corresponding device assembled with lithium cobalt oxide as a cathodic active material.
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