Synthesis of Porous δ‐MnO₂ Submicron Tubes as Highly Efficient Electrocatalyst for Rechargeable Li–O₂ Batteries

Abstract

Lithium–oxygen (Li–O₂) batteries are receiving intense interest because of their high energy density. A new tubular δ‐MnO₂ material prepared by a simple hydrothermal synthesis is an efficient electrocatalyst for Li–O₂ batteries. The synthesized δ‐MnO₂ exhibits a unique tubular structure, in which the porous walls are composed of highly dispersed ultrathin δ‐MnO₂ nanosheets. Such a unique structure and its intrinsic catalytic activity provide the right electrocatalyst characteristics for high‐performance Li–O₂ batteries. As a consequence, suppressed overpotentials—especially the oxygen evolution reaction overpotential—superior rate capability, and desirable cycle life are achieved with these submicron δ‐MnO₂ tubes as the electrocatalyst. Remarkably, the discharge product Li₂O₂ of the Li–O₂ battery exhibits a uniform nanosheet‐like morphology, which indicates the critical role of the δ‐MnO₂ in the electrochemical process, and a mechanism is proposed to analyze the catalysis of δ‐MnO₂.