Silver decorated beta-manganese oxide nanorods as an effective cathode electrocatalyst for rechargeable lithium-oxygen battery

In this paper, Ag nanoparticles decorated β-MnO₂ nanorods are studied as cathode catalyst for rechargeable lithium-oxygen battery (LOB). β-MnO₂ nanorods are prepared using a simple hydrothermal method based on MnO₄^- and the decoration of Ag nanoparticles is performed by in-situ composite technique in the presence of polymeric additives. The as-prepared materials are characterized by XRD, TEM, XPS, BET and Raman spectrum. Electrochemical charging and discharging capacity of β-MnO₂ and Ag/β-MnO₂ electrodes are investigated at the current density of 0.02 mA cm^-2 in the voltage window of 2.0-4.0 V. LOB with Ag/β-MnO₂ electrode shows an initial discharge capacity of 873 mA hg^-1_(electrode), with reversible charge capacity of 811 mA hg^-1_(electrode) while battery with only β-MnO₂ has discharge capacity of 541 mA hg^-1_(electrode) and charge capacity of 445 mA hg^-1_(electrode). Ag/β-MnO₂ nanocomposite electrode shows good rate capability and cycle stability. After 10 cycles, the capacity of 742 mA hg^-1_(electrode) is still retained at the current density of 0.02 mA cm^-2 while only 219 mA hg^-1_(electrode) is retained at 0.5 mA cm^-2. The capacity retention rate is 84.9% and 70.2% at 0.02 and 0.5 mA cm^-2, respectively. During discharging, Li₂O is the main discharge product and no Li₂CO₃ is formed. The results show that the electrochemical performance of β-MnO₂ is greatly enhanced when Ag nanoparticles are introduced. And it is highly effective for decreasing the charging potential close to the theoretical value. Ag nanoparticles can enhance the electronic conductivity of the network. The study confirms that Ag/β-MnO₂ catalyst is a promising effective catalyst for LOB.