Atomic and Electronic Structures of Li0.44MnO2 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 Na0.44MnO2 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 Li0.44MnO2 nanowires and its byproduct formed after the conversion of Na0.44MnO2 nanowires into Li0.44MnO2 nanowires, as the first half of the process in the conversion of Na0.44MnO2 nanowires into LiMn2O4 nanowires. Results show that Li0.44MnO2 nanowires have a well-defined single-crystalline nature. The byproduct is identified as nanoparticles of Li2MnO3 (space group P3112) different from conventional Li2MnO3 (space group C2/m), formed on the surfaces of Li0.44MnO2 nanowires with the specific crystallographic relationship. The formation mechanism of Li2MnO3 nanoparticles and their role in the conversion of Li0.44MnO2 nanowires into LiMn2O4 nanowires are discussed.