Preparation And Investigation Of Cathode For Li-O₂ And Li-CO₂ Batteries

In order to minimize the consumption of fossil fuels and thus reduce the impact of carbon dioxide emissions on global warming,a road transport electrification strategy is being implemented.The main technical obstacle to comprehensive electrification is to explore advanced energy storage system.Rechargeable Li-O₂ and Li-CO₂ batteries are considered to be the most promising energy storage and conversion equipment due to their high energy density.However,Li-O₂ and Li-CO₂ batteries still face many problems,among which the key is the lack of efficient electrocatalyst,which seriously hinder the commercialization of this technology.In view of the above problems,this paper aims to design and prepare advanced electrode structure and study high activity catalyst system so as to improve the electrical properties of Li-O₂ and Li-CO₂ batteries.The research content includes the following three aspects:?1?The hollow carbon ball composites coated with NiO/Ni sheets were prepared by two-step hydrothermal reaction.The results of electrocatalytic performance test show that the NiO/Ni laminated hollow carbon ball composites have good catalytic activity of oxygen reduction reaction?ORR?and oxygen analysis reaction?OER?and good stability in alkaline solution.As a cathode catalyst for non-aqueous Li-O₂batteries,the specific capacity reached 6115.9 mAh g^-1 when the cut-off voltage of discharging attained about2.0 V and at a current density of 100 mA g^-1.In addition,the batteries show good stability over 30 cycles at a current density of 100 mA g^-1 with the capacity cut off of 1000 mAh g^-1.?2?The N and S co-doped 3D graphene supported NiO composites were prepared by simple hydrothermal and physical adsorption methods.The electrocatalytic properties of the materials were tested in alkaline solution,the results show that N,S-3DG@NiO exhibited excellent ORR and OER performance,especially OER catalytic activity,and better stability than commercial Pt/C catalyst.When the current density was 100mA g^-1 and the cut-off voltage of 2.0 V,the materials as a cathode for non-aqueous Li-O₂ batteries delivered capacity of 17300 mAh g^-1,and the discharge specific capacity in Li-CO₂ batteries reached 13400mAh g^-1.In addition,under the condition of current density of 100 mA g^-1 and limited capacity of 500 mAh g^-1,the materials exhibited excellent cycle stability as a cathode electrode for Li-O₂ battery and Li-CO₂battery,respectively.We also used XPS and SEM test results to further confirm that N,S-3DG@NiO,as the cathode electrode catalyst of Li-CO₂ batteries can promote the decomposition of discharge product Li₂CO₃.?3?Cu-MOF was synthesized by hydrothermal method and a carbon-coated Cu nanoparticle composite was prepared by heat treatment.The oxygen reduction reaction and oxygen evolution reaction were tested in alkaline solution,respectively.The results showed that the catalytic performance of the material after 2 h heat treatment of Cu-MOF was the best,and its stability was also better than that of commercial Pt/C catalyst.As a cathode catalyst for Li-CO₂ batteries showed good stability over 50 cycles at a current density of 50 mA g^-1 with the capacity cut off of 1000 mAh g^-1.In addition,the cyclic stability of the material was tested under different charge and discharge current densities,and the results showed that the change of current density had little influence on the overpotential of the batteries,and that the current density could be stabilized for 40 cycles or even 60 cycles.