Conjugated cobalt polyphthalocyanine with defective π-π extended structure for enhanced rechargeable li-oxygen batteries

Abstract

The urgent demand for high-energy and high-power energy storage devices initiates considerable interest for Li-O2 batteries. Considering the catalytic reaction that happened on the cathode, the electrocatalyst plays a key role in deciding the performance of Li-O2 batteries. Herein, a cobalt polyphthalocyanine with defective polymeric layered structure (D-CoPPc) is prepared by an annealing treatment. The macromolecular structure of D-CoPPc overcomes the dissolution of cobalt phthalocyanine (CoPc) therefore guarantying structural stability. Such a distinctive structure provides imperative features for Li-O2 batteries involving the intrinsic high catalytic activity of CoPc unit, high conductivity given by π-π extended conjugated skeleton. Moreover, the introduced irregular structural defects are expected to promote the diffusion of oxygen. As a result, Li-O2 battery with D-CoPPc as a catalyst achieves a high specific capacity of 4.0 mA h cm−2 at a current density of 50 μA cm−2, a remarkable rate capability with the discharge voltage reached at 2.55 V at a current density of 500 μA cm−2, and a superior cycling stability of more than 1000 h at 20 μA cm−2. As such, the presented framework tailoring and defect engineering strategy open new avenues to regulate the catalytic activity for high-performance metal–oxygen batteries.