Bimetallic Electrocatalysts in Li-O2 Battery: How the Componential Proportion Influences the Battery Performance

Sunday, 28 May 2017: 14:20
Grand Salon D - Section 21 (Hilton New Orleans Riverside)
X. Luo, L. Ge, L. Ma, J. Kropf, J. Wen, X. Zuo (Argonne National Laboratory), Y. Ren (Advanced Photon Source, Argonne National Laboratory), D. Miller, T. Wu, J. Lu, and K. Amine (Argonne National Laboratory)
In comparison with conventional Li-ion batteries, the superior theoretical energy density makes the lithium-air battery one of the most promising technologies for next-generation energy storage. However, its commercialization is still hindered by several challenges, such as poor cycleability and large overpotential. Particularly, the high charge overpotential not only induces a low Coulombic efficiency and low round-trip efficiency, but also aggravates the whole battery system by increasing the possibility of electrolyte decomposition and byproducts. It is well known that, due to the multiple electron transfer nature, the sluggish kinetics of the OER usually leads to charge overpotential. Hence, various electrocatalysts have been explored to lower the overpotential and to improve the battery performance. However, most of the charge potentials are still too high for practical use of the rechargeable Li-O2 battery.

Over the last few decades, nanostructured bimetallic catalysts have shown extraordinary electronic and chemical catalytic properties for many applications, such as fuel cells, nitrogen production, and biomass-fuel conversion. The greatly enhanced catalytic performance can be ascribed to the formation of the heteroatom bonds on the metal surface and the variation of the local bonding geometry. The former modifies the electronic environment of the surface atoms and their reactivity, while the latter affects the electronic structure of the metal. Therefore, it is possible to tailor the composition and structure of nanostructured bimetallic catalysts to meet requirement for certain applications.

Here, by choosing a right component proportion in Pt-Cu bimetallic electrocatalysts which optimize the electrocatalytic activity on the electrochemical reactions, especially on oxygen evolution reactions, we demonstrated a superior electrochemical behavior with the low charge overpotential of 0.2 V and the cycleability of 50 discharge/charge cycles before the capacity fading. Synchrotron high-energy X-ray diffraction (HE-XRD), X-ray absorption spectroscopy (XAS), and electron microscopy (EM) were employed to study the morphology and component of the electrochemical reaction products. The results of this study have shown that the optimized Pt-Cu bimetallic electrocatalysts significantly reduce the charge overpotential, and furthermore enhance the efficiency, stability, and cycleability of an aprotic Li-O2 battery. It would also serve as a general guide for nanostructured bimetallic catalysts design and optimization.