Engineering And Performance Studies Of Lithium-Oxygen Batteries Using Gel Polymer Electrolyte And Nanoarray Cathode

Lithium-oxygen batteries?LOBs?are research hotspots due to their ultra-high energy densities.However,the open system of LOB has some safety issues such as electrolyte leakage,volatilization,flammability,and so on.To address these issues,polymer electrolytes were used to replace organic electrolytes and to prepare solid-state LOBs.However,the resistances of oxygen electrode/solid electrolyte interfaces are generally high with a sandwich cell structure of lithium sheet/polymer electrolyte/oxygen electrode,which further increases the charge-discharge polarization of LOBs with intrinsically sluggish kinetics.To this end,this thesis prepared a series of high-performance nanoarray electrodes and highly stable gel polymer electrolyte?GPE?,and proposes a novel strategy for fabricating the integrated architecture of nanoarray electrode and GPE.The integrated architecture constructs three-dimensionally distributed electrode/electrolyte interfaces,provides abundant catalytic active sites,enhances the utilization of catalysts,and thus achieves the higher capacities and lower polarizations of as-prepared solid-state LOBs.The main research contents and conclusions are as follows:?1?Co₃O₄/CC,MnO₂/CC and MnO₂-Co₃O₄/CC nanosheet array electrodes were prepared on carbon clothes?CC?by electrodeposition and subsequent heat treatment.The morphologies and chemical compositions of the nanosheet array electrodes were studied by XRD,SEM,TEM and XPS.The results show that,as the air electrode of LOB,Co₃O₄/CC has a high catalytic activity for oxygen evolution reaction?OER?.MnO₂/CC has high activity for oxygen reduction reaction?ORR?.The hybrid MnO₂-Co₃O₄/CC combining the features of their two components shows bifunctional catalytic activities for both ORR and OER.The porous architecture of nanoarray electrodes provides not only a channel for the oxygen diffusion,but also an ideal architecture to fabricate bifunctional catalysts via integrating the catalytic capability of two components.?2?A three-dimensional porous carbon electrode?C/CC?was prepared using Co₃O₄/CC nanoarray as the template and polydopamine as the carbon source.The morphology and chemical composition of the electrode were studied by XRD,SEM,and XPS.After the loading of Ru catalyst,C@Ru/CC electrode exhibits high discharge capacity of 3⁴ mAh?cm^-2 and excellent cycle performance(63 cycles with a cutoff capacity of 0.25 mAh?cm^-2).?3?The integrated architecture of nanoarray electrode-GPE was prepared by UV-initiated polymerization via introducing the polymer precursors into nanoarray electrodes?Co₃O₄/CC,MnO₂-Co₃O₄/CC,C@Ru/CC?in advance.Compared with the sandwich structure of"lithium sheet/polymer electrolyte/oxygen electrode",the polymer LOBs with the integrated structure exhibits higher discharge capacity,better cycle performance and higher rate performance.Optical and SEM images show that the integrated structure constructs a large number of three-dimensionally distributed electrode/electrolyte interfaces,provides abundant active sites,and consequently reduces the interfacial resistance.This work is of great significance to the kinetic study of solid electrolyte/catalytic electrode and the structure design of all-solid-state LOBs.