Preparation and electrochemical properties of Ag/MnO2 composite electrode materials

Transition metal oxide MnO2 has great potential in battery storage because of its simple preparation process, abundant reserves, environmental protection and high theoretical specific capacity. In this paper, MnO2 nanosheets were prepared by exfoliating the hydrothermally synthesized δ-MnO2 by the swelling method. The Ag/MnO2 composites were obtained by loading Ag nanoparticles on the surface of MnO2 nanosheets under UV irradiation and NaBH4 reduction. The structure and morphology of Ag/MnO2 composites were characterized and their electrochemical properties were tested. The results show that the electrochemical performance of Ag/MnO2 as anode material for lithium ion batteries is obviously better than that of the pure phase δ-MnO2. The first reversible specific capacity of Ag/MnO2 at the current density of 100 mA/g reaches 1001.1 mA·h/g, and the coulombic efficiency is 79.9%. At the current density of 0.1, 0.2, 0.5, 1.0 and 2.0 A/g, the average reversible specific capacity is 936.3, 607.5, 429.5, 351.1 and 278 mA·h/g, respectively. When the current density returns to 0.1 A/g, the average reversible specific capacity can still reach 658.7 mA·h/g. The improvement of the electrochemical performance of Ag/MnO2 is attributed to the fact that the uniformly loaded conductive Ag particles significantly enhance the electrical conductivity of the electrode material, which is conducive to the transport of charged particles. In addition, the nano-structure of Ag/MnO2 composites shortens the transport path of lithium ions in the solid phase, thus increasing the diffusion rate of lithium ions. Copyright ©2022 Acta Materiae Compositae Sinica. All rights reserved.