Carbonized Metal Organic Framework Derived Co3O4/Carbon Nanofiber As the Cathode Material in the Non-Aqueous Li-Air Battery

With increasing demand of high energy storage capability, many researchers have developed various types of battery systems with optimized structure and materials. In particular, metal-air batteries are considered to be a strong candidate of next generation energy storage systems due to their potential advantages such as light weight and high energy storage capability. Among metal-air batteries, Li-air batteries offer the highest theoretical energy density (11140 W h kg^-1) which is around higher than that of the conventional Li-ion battery. However, there still exist a lot of technical barriers to be overcome, and the challenges include low rate capability, a poor cycle life, and instability of electrochemical performances. The practical discharge capacity is far lower than the theoretical values because the reaction products (Li₂O or Li₂O₂) are difficult to be dissolved in the non-aqueous electrolyte and they can block the oxygen path for oxygen diffusion. Due to these reasons, the performance of the Li-air battery strongly depends on the characteristics of carbon-based cathodes. In addition, high efficient catalytic materials for the oxygen reduction reaction (ORR) during discharge and the oxygen evolution reaction (OER) during charge are essential to achieve reduced overpotential and improved rate performance.

Recently, there have been some attempts to produce carbon materials by simple carbonization of metal organic frameworks (MOFs) for energy storage systems. The sacrificial MOFs precursors were directly carbonized under inert atmosphere. The carbonized MOFs as cathode materials are known to have various advantages. Their structures can be designed and tunable in accordance with desired properties by selecting type of metal organic frameworks. Previous studies on metal oxide-carbon composites (Co₃O₄, RuO₂, NiCo₂O₄, etc.) have demonstrated that they are good candidates as cathodes for Li-air battery with good electrochemical performances.

In this work, we demonstrate the application of the carbonized metal organic framework/Carbon nanofiber composites as the cathode material in non-aqueous Li-air battery. Various techniques including scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM) were employed to characterize the morphology and crystalline structure of the framework system. The Brunauer-Emmett-Teller (BET) was utilized for the analysis of the surface area and porosity of the sample. The electrochemical properties of the carbonized metal organic framework/Carbon nanofiber composites as the cathode electrode in Li-air battery were studied using the galvanostatic charge-discharge characterization method. The synthesized carbonized metal organic frameworks/Carbon nanofiber composites show large specific surface area and narrow pore size distribution. It was shown that the open channel architecture of the metal organic framework enhances the oxygen gas supply to the interface between the electrolyte and the cathode surface. 

Acknowledgement

This research was supported by the MSIP(Ministry of Science, ICT and Future Planning), Korea, under the “IT Consilience Creative Program” (NIPA-2014-H0201-14-1002) supervised by the NIPA(National IT Industry Promotion Agency)