Ag doped urchin-like α-MnO2 toward efficient and bifunctional electrocatalysts for Li-O2 batteries

Rechargeable Li-O 2 batteries (LOBs) have been receiving intensive attention because of their ultra-high theoretical energy density close to the gasoline. Herein, Ag modified urchin-like α-MnO 2 (Ag-MnO 2 ) material with hierarchical porous structure is obtained by a facile one-step hydrothermal method. Ag-MnO 2 possesses thick nanowires and presents hierarchical porous structure of mesopores and macropores. The unique structure can expose more active sites, and provide continuous pathways for O 2 and discharge products as well. The doping of Ag leads to the change of electronic distribution in a-MnO 2 (i.e., more oxygen vacancies), which play important roles in improving their intrinsic catalytic activity and conductivity. As a result, LOBs with Ag-MnO 2 catalysts exhibit lower overpotential, higher discharge specific capacity and much better cycle stability compared to pure α-MnO 2 . LOBs with Ag-MnO 2 catalysts exhibit a superior discharge specific capacity of 13,131 mAhg −1 at a current density of 200 mAg −1 , a good cycle stability of 500 cycles at the capacity of 500 mAhg −1 . When current density is increased to 400 mAg −1 , LOBs still retain a long lifespan of 170 cycles at a limited capacity of 1,000 mAhg −1 .