α-MnO2 nanoneedle-based hollow microspheres coated with Pd nanoparticles as a novel catalyst for rechargeable lithium-air batteries
(1. School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China;
2. National Key Laboratory of Science and Technology on Power Sources,
Tianjin Institute of Power Sources, Tianjin 300384, China;
3. Key Laboratory of Advanced Energy Materials Chemistry, Ministry of Education,
Nankai University, Tianjin 300071, China)
2. National Key Laboratory of Science and Technology on Power Sources,
Tianjin Institute of Power Sources, Tianjin 300384, China;
3. Key Laboratory of Advanced Energy Materials Chemistry, Ministry of Education,
Nankai University, Tianjin 300071, China)
Abstract: The hollow α-MnO2 nanoneedle-based microspheres coated with Pd nanoparticles were reported as a novel catalyst for rechargeable lithium-air batteries. The hollow microspheres are composed of α-MnO2 nanoneedles. Pd nanoparticles are deposited on the hollow microspheres through an aqueous-solution reduction of PdCl2 with NaBH4 at room temperature. The results of TEM, XRD, and EDS show that the Pd nanoparticles are coated on the surface of α-MnO2 nanoneedles uniformly and the mass fraction of Pd in the Pd-coated α-MnO2 catalyst is about 8.88%. Compared with the counterpart of the hollow α-MnO2 catalyst, the hollow Pd-coated α-MnO2 catalyst improves the energy conversion efficiency and the charge-discharge cycling performance of the air electrode. The initial specific discharge capacity of an air electrode composed of Super P carbon and the as-prepared Pd-coated α-MnO2 catalyst is 1220 mA·h/g (based on the total electrode mass) at a current density of 0.1 mA/cm2, and the capacity retention rate is about 47.3% after 13 charge-discharge cycles. The results of charge-discharge cycling tests demonstrate that this novel Pd-coated α-MnO2 catalyst with a hierarchical core-shell structure is a promising catalyst for the lithium-air battery.
Key words: lithium-air battery; composite catalyst; nanoneedle-based hollow microsphere; core-shell structure