| The development of high-energy and rechargeable batteries—especially lithium-ion batteries(LIBs)is of great importance to reduce the excessive consumption of fossil fuels and promote the rapid growth of electric vehicles(EVs).The limited lithium reserves and uneven distribution in the earth’s crust has been increasing the high production cost for LIBs,which hinders its future way of large-scale application,and stimulate researchers to explore rich and low-cost materials for secondary batteries to replace the cost-incresing lithium-ion batteries(LIBs).Recently,sodium-ion batteries(SIBs)have attracted much attention,especially for large-scale energy storage applications,due to the potential low-cost advantages of sodium and greater natural abundance,and the similar electrical storage mechanism to LIBs.Among those anode materials,transition metal sulfides(TMSs)have been attractive for lithium/sodium ion batteries due to their high theoretical capacity,good electrical conductivity,and the wide range of sources.However,TMSs still suffer from poor cycle stability and low rate performance.Effective improvement stratergies typically involve the introduction of carbonaceous materials,as well as ranationl design of mophorlogy and structures.In this thesis,two types of heteroatom-doped carbon-loaded TMSs microsheres((Ni0.5Co0.5)S2@NPC and Co9S8-NC@C)were successfully prepared by using simple hydrothermal synthesis,intercalation method,and low temperature heat treatment.The characterization,structure and composition of these materials were characterized by various characterization instruments.Furthermore,these materials were used as anodes for the lithium-/sodium-ion battery,and electrochemical performance tests were performed.The main contents of this thesis are presented as follows.(1)(Ni0.5Co0.5)S2@NPC microsphere anode materials.Nitrogen-phosphorus co-doped biomass carbon-supported(Ni0.5Co0.5)S2 nanoparticles((Ni0.5Co0.5)S2@NPC)composite microsphere was successfully prepared by hydrothermal synthesis and low-temperature heat treatment,using yeast cells as spherical structure templates and carbon sources with rich heteroatoms.When(Ni0.5Co0.5)S2@NPC was used as the anode materials for LIB,it can dilvered a reversible specific capacity of 600 mAh g-1(500 mA g-1,after 450 cycles),and in particular,a reversible specific capacity of 480 mAh g-1(1 A g-1,after 200 cycles).Both specific capacities are much better than those of the counterparts of single-metal CoS2@NPCS and pure carbon sphere NPCS.When(Ni0.5Co0.5)S2@NPC electrode material was used as the anode material of sodium ion battery,the electrode exhibited the electrochemical performance superior to those of CoS2@NPCS and NPCS electrode.The posibilities of these enhancements can be attributed to the following advantages:the uniform distribution(Ni0.5Co0.5)S2 nanoparticles;the dual protection and the boosted electronic conductitivty of the amorphous carbon and the graphitized carbon double layer.(2)Co9S8-NC@C microsphere anode materials.The microsphere of double-carbon coated Co9S8 nanoparticle(Co9S8-NC@C)composite was successfully prepared by low temperature heat treatment of ZIF particle-grown on the metanlic-interclated Co(OH)2.When used as an anode material for lithium ion batteries,the Co9S8-NC@C electrode dilivered a high initial charge capacity(1063 mAh g-1)and a Coulombic efficiency of about 73.4%.In particular,the reversible charge capacity of 880 mAh g-1 is still available(100 mA g-1,after 77 cycles),which is much larger than that of the Co9S8-NC counterpart(606 mAh g-1).When used as an anode material for sodium ion battery,the Co9S8-NC@C electrode exhibited a good cycle stability(up to 382 mAh g-1 after 100 cycles),which significantly outperforms that of the Co9S8-NC counterpart.The posibilities of these enhancements can be attributed to the following advantages:Co9S8 nanoparticles are uniformly coated with a 3D amorphous carbon skeleton and a ZIF-derived carbon. |
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