A hierarchical porous carbon supported Pd@Pd4S heterostructure as an efficient catalytic material positive electrode for Li–O2 batteries

Abstract

Li-oxygen batteries (LOBs) are considered as one of the most promising energy storage devices due to their superior energy density. However, the questions of large overpotential and poor cycling stability caused by sluggish oxygen reaction kinetics are remain. Here, we propose that constructing heterostructured nanomaterials with high conductivity is an effective way to enhance the eletrocatalytic activity in LOBs. The core-shell Pd@Pd4S heterostructures decorated on the porous carbon matrix are successfully fabricated by adopting hypo (Na2S2O3·5H2O) as a sulfidation reactant in a simple method, which is used as an oxygen cathode for LOBs for the first time. The hierarchical regular pore structure in Pd@Pd4S–C with a high surface area offers sufficient Li2O2 accommodations, which can facilitate a higher capacity and achieving a longer cycle life. The introduction of the Pd4S shell greatly boosts decomposition of Li2O2, which effectively decreases the overpotentials, and contributes to the outstanding cycling stability of Pd@Pd4S–C electrode (176 cycles at a current density of 500 mA g−1). This novel heterostructure fabrication method highlights the importance of efficient O2-electrode designs and provides a facile way to optimize the cathode materials for LOBs.