Atomic and Electronic Structures of Li_0.44MnO₂ Nanowires and Li₂MnO₃ Byproducts in the Formation Process of LiMn₂O₄ Nanowires

Abstract

High-quality single crystalline LiMn₂O₄ nanowires, which can be synthesized by the conversion of Na_0.44MnO₂ nanowires, are promising electrode materials for high-power lithium ion batteries. Understanding the conversion mechanism is crucial for further improvement of the quality of LiMn₂O₄ nanowires. In this paper, using advanced techniques of transmission electron microscopy and electron energy-loss spectroscopy, we investigate the atomic and electronic structures of both Li_0.44MnO₂ nanowires and its byproduct formed after the conversion of Na_0.44MnO₂ nanowires into Li_0.44MnO₂ nanowires, as the first half of the process in the conversion of Na_0.44MnO₂ nanowires into LiMn₂O₄ nanowires. Results show that Li_0.44MnO₂ nanowires have a well-defined single-crystalline nature. The byproduct is identified as nanoparticles of Li₂MnO₃ (space group <i>P</i>3₁12) different from conventional Li₂MnO₃ (space group <i>C</i>2/<i>m</i>), formed on the surfaces of Li_0.44MnO₂ nanowires with the specific crystallographic relationship. The formation mechanism of Li₂MnO₃ nanoparticles and their role in the conversion of Li_0.44MnO₂ nanowires into LiMn₂O₄ nanowires are discussed.