Synthesis and electrochemical characterization of orthorhombic LiMnO2 material

Well-defined orthorhombic LiMnO₂ was synthesized using LiOH and γ-MnOOH starting materials at 1000 °C in an argon flow by quenching process. X-ray diffraction (XRD) revealed that the compound showed an orthorhombic phase of a space group with Pmnm (a=2.806 Å, b=5.750 Å, and c=4.593 Å). The prepared compound was composed of particles of about 5-15 μm diameter with a bar-shape and small spherical one of about 1-2 μm. It showed very small initial discharge capacity of about 34 mA h g⁻¹ in the (3+4) V region at room temperature. However, after 12 h grinding, the LiMnO₂ delivered 201 mA h g⁻¹ in the first cycle and still delivered 200 mA h g⁻¹ after 50 cycles at room temperature. We found that the initial discharge capacity of LiMnO₂ agreed well with its specific surface area by Brunauer, Emmett and Teller (BET) analysis. Especially, the grinding treatment played an important role to activate the lithium insertion-extraction into the LiMnO₂ layer in the 3 V region.