Photovoltaic Lithium-ion Battery with Layer-Structured Li₂Mn^III_0.2Mn^IV_0.8O_2.9 Thin Film Chemically Fabricated for Cathodic Active Material

• Main Authors: Yutaka Suwazono, Hiroki Nagai, Mitsunobu Sato
• Format: Article
• Language: English
• Published: MDPI AG 2020-03-01
• Series: Energies
• Subjects: li₂mno₃ thin film; photovoltaic device; lithium-ion battery; molecular precursor method
• Online Access: https://www.mdpi.com/1996-1073/13/6/1486

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 Mn³⁺/Mn⁴⁺ is 1/4, and the chemical formula can be expressed as Li₂MnO_2.9. A device was assembled with O-deficient LMO and TiO₂ thin films as each active material, along with an electrolytic solution involving LiPF₆. 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.