Research On Lanthanum Cobalt Nickel Perovskite With Special Morphology For Aprotic Li-O₂ Battery

In recent years,electric vehicles（EVs）have become a hot spot in the field of automotive research and development.Even the fully developed Li-ion batteries may not meet the EVs application demand due to the lower theoretical energy densities.Thus,the exploitation of efficient energy storage devices for EVs is still a great challenge.Li-O₂ batteries are regarded as the future energy storage technologies due to their high theoretical energy density(11680Wh kg^-1),which is comparable to gasoline engines(13000 Wh kg^-1).However,Li-O₂ batteries are still in the early stages of laboratory research at this stage.Low energy efficiency and poor cycle life caused by the degradation of electrolyte and the instability of air electrodes are the main challenges hindering the development of this technology.To address these issues and improve Li-O₂ batteries performance,the design of the new air electrode is indispensable.Among the electrode catalysts,lanthanum-cobalt-based perovskite has been studied and some outstanding improvements have been achieved in Li-O₂ batteries due to its high electrical conductivity and catalytic performance.However,the capacity performance and cycle stability of the corresponding Li-O₂ batteries still need to improved.In this paper,LCNO perovskite is slected as a cathode catalyst,aiming to accelerate ORR/OER and induce the formation of thin sheet-like Li₂O₂,finally improving the capacity performance and cycle stability.The conclusions of this research are summarized as follows:（1）Effect of La_0.9Co_0.8Ni_0.2O_3-x morphology on Li-O₂ battery performancePorous nanocubes La_0.9Co_0.8Ni_0.2O_3-x perovskite（PN-LCN）are synthesized by a facile hydrothermal method with the special hierarchical porous morphology.Compared with dense particles La_0.9Co_0.8Ni_0.2O_3-x perovskite（DP-LCN）prepared by sol-gel,PN-LCN with higher surface area and combination of mesoporous and macroporous structure are favourable for electrolyte impregnation,O₂ transport and Li₂O₂ accumulation.At the same time,the surface of PN-LCN provide higher oxygen vacancies,which increases the active sites of the electrochemical reaction and enhances the ORR activity.Hence,Li-O₂ with PN-LCN can deliver a specific discharge capacity of 14360 m Ah g^-1 and a specific charge capacity of 12630m Ah g^-1 at a current density of 300 m A g^-1 and a cycle stability of over 100 cycles.（2）Study on Co₃O₄@La Co_0.6Ni_0.4O₃ nanofibers bifunctional catalystIn order to improve the OER catalytic activity of La Co_0.6Ni_0.4O₃,we induce Co₃O₄nanocrystals with about 5～10 nm onto the surface of La Co_0.6Ni_0.4O₃ nanofibers（LCN NFs）.Co₃O₄@LCN NFs show high catalytic activity for both ORR and OER processes due to numerous oxygen vacancies by the introduction of Co₃O₄ and the synergistic effect of the two catalysts.The surface of Co₃O₄@LCN NFs with strong O₂ adsorption abality induce the formation of sheet-like Li₂O₂.This kind of Li₂O₂ with more closely and evenly contacting on the Co₃O₄@LCN NFs can greatly reduce the interface electron transport resistance and achieve the complete decomposition at low voltage.Compared with LCN NFs,Li-O₂ batteries with Co₃O₄@LCN NFs deliver a specific capacity of 14506 m Ah g^-1 with a coulomb efficiency of 89%at 400 m A g^-1.A long-term stability about 230 cycles can be reached without obvious deterioration at 1000 m A g^-1 with the capacity limitation of 500 m Ah g^-1.