The Efficiency and Mechanism of 3D-Ordered Macroporous La0.6Sr0.4Co0.2Fe0.8O3 as an Electrocatalyst for Aprotic Li-O2 Batteries

Lithium-oxygen (Li-O₂) batteries with high energy density have thought to be the most attractive alternatives to nowadays Li-ion batteries. However, some challenges are still to be resolved, among which is the high charge overpotential that could compromise the cycle stability and capacity performance. ^{[1, 2]} The high overpotential is ascribed to the insolated discharge products Li₂O₂, which could not decompose completely during the charge processes. With the increasing cycles of battery tests, the Li₂O₂ will crystallize and block the porous cathode materials. ^{[3, 4]}

However, recent studies have demonstrated that the structure and morphology could influence the conductivity and thus affect the overpotential. It is crucial to find an electrocatalyst that could accelerate the decomposition of Li₂O₂ and influence the crystallization of Li₂O₂ to get small size or amorphous Li₂O₂ products. ^{[5, 6]} Perovskite oxides La_0.6Sr_0.4Co_0.2Fe_0.8O₃ (LSCF) have been proved efficient to lower overpotential in aqueous Li-air batteries ^[7] but not have been applied in Li-O₂ batteries.

Herein the 3D-ordered macroporous LSCF (3D-LSCF) with very high BET surface area have been prepared and employed as electrocatalyst in Li-O₂ batteries with DMSO based electrolyte. The Li-O₂ batteries with this catalyst show lower overpotential, better cycle stability and capacity performance. As shown in Figure 1, the charge plateau of Li-O₂ batteries with 3D-LSCF catalyst are flat and the charge potential is below 3.8V after nine cycles. The primary reason of the lower overpotential may be ascribe to the high oxygen pathways in 3D-LSCF structure which could accelerate the decomposition of Li₂O₂ products. ^[8] In order to conform the better ability of oxygen transmit of 3D-LSCF, the batteries have been tested in different levels of oxygen environments. With the increase of oxygen content, the performance of batteries without catalyst has increased more obviously than with 3D-LSCF catalyst, which indicates that the 3D-LSCF catalyst could transmit relatively sufficient oxygen. The morphologies of pure KB electrode and KB/3D-LSCF electrode at different states have been observed and the 3D-ordered macroporous structure of LSCF is beneficial to form small size of Li₂O₂ with large contact area to the KB that could assist in the decomposition at lower charge potential. The details of results and specific analysis will be exhibited in the presentation.

Fig. 1 The cycle performance of Li-O₂ batteries with 3D-LSCF catalyst at the current densities of 100mAg^-1.

Acknowledgements: This program was supported by Innovative Research Team in University (PCSIRT No. IRT1014).

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