Controllable Construction Of BNC-based Composites Catalysts And Its Application In Lithium-Air Batteries

The excellent theoretical performance and development prospects of lithium-air batteries make it expected to become the next generation of energy storage devices,which are used in portable electronic devices and vehicles.However,due to its slow oxygen reduction and oxygen evolution(ORR/OER)performance,there are still many obstacles to its commercialization.Many researchers are committed to developing highly efficient dual-function catalysts applied to air cathodes to optimize battery performance and extend cycle life.Relatively speaking,designing composite materials,comprehensive performance advantages,and complementing each other is the first choice for the development of new high-activity catalysts.At present,many studies have analyzed and tested heteroatom-doped carbon materials,which prove that they have good catalytic activity for oxygen reduction.This paper focuses on the study of heteroatomic boron and nitrogen co-doped carbon nanosheets(BNC)as the catalyst carrier,and selects the excellent precious metals and transition metals to compound with the BNC carrier,respectively,for use in lithium-air battery cathode catalysts.Analyze its morphology and element information through various characterization tests,and then use rotating disk electrode(RDE)and Neware battery test system to test its catalytic performance and battery performance,analyze its catalytic mechanism,and develop high activity Li-air battery cathode catalyst provides design ideas.The third chapter of the thesis uses the low-temperature immersion reduction method to evenly disperse the precious metal Pd nanoparticles on the surface of the BNC nanosheets.Through TEM,BET,XPS and other tests to obtain morphology and element analysis,it can be known that two-dimensional BNC nanosheets take advantage of their high active specific surface area and electronic properties.It can be used as a good carrier to support and disperse precious metal Pd nanoparticles with excellent oxygen reduction properties.The electrochemical catalytic performance test conducted with the rotating disk electrode shows that the Pd NPs/BNC nanocomposite catalyst has a catalytic activity comparable to that of Pt/C.The composite material is used as a positive electrode catalyst to be tested after assembling into a battery.The voltage of the battery drops significantly(?0.44V),and it has a higher first discharge capacity(?15675 m A h g^-1),which improves the cycle stability of the battery(?106cycles).In order to balance performance and cost,the fourth chapter chooses the bimetallic cobalt-based spinel in the transition metal oxide,and uses the solvothermal method to grow porous spinel Fe Co₂O₄nanoparticles composite BNC nano-sheet materials in situ.It combines the good oxygen reduction activity of BNC materials and the excellent OER catalytic performance of porous Fe Co₂O₄nanoparticles.The FCO@BNC composite with the best ORR/OER performance was selected through the RDE test,and its load mass ratio was 40%.As a cathode catalyst material for organic lithium-air batteries,FCO@BNC composite material has higher initial discharge capacity,lower overvoltage and longer service life than pure BNC or Fe Co₂O₄catalysts in lithium-air battery tests.