Preparation Of Carbon-based Anode Materials And Their Application In Alkaline Metal Batteries

Metal-organic frameworks(MOFs)is an organic-inorganic hybrid material with a series of advantages.MOFs-derived materials are made by MOFs as precursors,which has stable structure and excellent conductivity.Carbon materials derived from MOFs have become the preferred anode material for alkaline metal batteries due to their lower cost and higher stability.Transition metal oxides have also attracted widespread attention due to their higher specific capacity.The contents of this thesis mainly include:1.Optimal interlayer spacing of K⁺intercalation in the carbon-containing material was determined by DFT calculation.According to the theoretical results,we further designed and manufactured N/O co-doped carbon nanofibers(NOCNs)with adjustable interlayer spacing as an anode material of PIBs.According to research results,NOCNs-700 with interlayer spacing of 0.38 nm exhibits excellent reversible capacity of 626 mAh g^-1after repeated cycles of 200 times at a current density of 100 mAg^-1,excellent rate performance(123 mAh g^-1at 20Ag^-1)and cycle stability(262 mAh g^-1at 5 Ag^-1).Compared with the existing PIBs carbon anode materials with different increased interlayer spacing,we systematically explored the effect of interlayer spacing on potassium storage performance,and confirmed that the interlayer spacing of 0.38 nm is the best interlayer spacing for K⁺storage.2.Through a"one-to-two"strategy,the obtained precursor is first carbonized in nitrogen,and the formed NaCl nanocrystals are used as the surface stabilizing template of the hollow structure,and the oleate adsorbed on the surface of the NaCl nanocrystals is used as the carbon precursors.Then defect-rich porous carbon nanosheets(CNs)are produced to provide more active sites on the edge of nitrogen atoms.Nitriding in ammonia gas was used to synthesize high-edge nitrogen-doped porous carbon nanosheets(ENCNs)with an edge nitrogen content as high as 88.36%,which provides abundant active sites for K⁺,and the introduction of nitrogen atoms expands(002)lattice spacing,the increased layer spacing promotes the rapid diffusion of K⁺and enhances the K⁺embedding capacity.The resulting ENCNs-600 was tested at a current density of 100 mAg^-1,and its reversible capacity was 443mAh g^-1.Density functional theory calculations further confirm that edge nitrogen doping is beneficial to the adsorption of K⁺,and the increased interlayer distance helps K⁺diffusion,resulting in higher potassium storage capacity.3.MOF-derived strategy was used to synthesize a hybrid structure of NiO crystals embedded in a nitrogen-doped porous carbon matrix(NiO@N-C).The obtained ultrafine NiO nanocrystals are uniformly distributed in the nitrogen-doped carbon matrix,and the nitrogen-doped porous carbon matrix effectively improves the conductivity and reduces the volume expansion of NiO during the cycle.It was used as an anode material for lithium-ion batteries,and its capacity was tested.The reversible capacity of NiO@N-C electrode at a current density of 100 mAg^-1was still 1373 mAh g^-1after 200 cycles.4.Both NiO and Co₃O₄have higher capacities when used as electrode materials,but binary transition metal oxides have higher specific capacity and stable structure than single metal oxides,and the two metal oxides can produce synergistic effects.Thus,the electrochemical reactivity can be improved.We successfully synthesized porous hollow NiCo₂O₄nanowires by calcining Ni-Co-MOF directly in air.During the carbonization process,the decomposition of the precursor may be beneficial to the formation of small metal oxide nanocrystals.Therefore,NiCo₂O₄nanowires are composed of many NiCo₂O₄nanoparticles.With the release of gas molecules and uniform heat treatment,the prepared NiCo₂O₄nanowires have a one-dimensional hollow structure,which shortens the diffusion distance between the electrolyte and Li⁺,and therefore has good dynamic performance and capacity(1310 mAh g^-1at 100 mAg^-1and 720 mAh g^-1at 1000 mAg^-1).This work may provide a convenient strategy for the synthesis of one-dimensional porous hollow nanowires.