The Preparation And Lithium Storage Performance Of Carbon Materials Derived From Porous Organic Frameworks

In the last decades,the environmental friendliness and sustainability of electrical energy storage has gained increasing attention.Currently,lithium ion batteries?LIBs?,an important energy storage system,have attracted much attention.The electrode material is regarded as the key for the performance of LIBs.Hence,exploring suitable electrode materials for lithium ion storage is urgent.Recently,porous organic frameworks?POFs?,an emerging class of crystalline polymer networks composed of nonmetal elements?H,C,N,O and so on?,are considered as promising materials with wide applications in gas storage/separation,light emitters,semiconductors,proton conduction,catalysis and energy storage,owing to their uniform porosity,favorable thermal stability,ordered framework and tunable composition.Converting porous organic frameworks to structured carbon by direct thermolysis,especially in-situ heteroatom doped carbon,has caught extensive attention due to its laudable advantages,including facile synthesis strategies,tailored structures and properties by selecting diverse functional groups during the synthesis process and much improved electrical conductivity.In this thesis,we synthesized a series of POFs with different elements as precursors to obtain heteroatom doped carbon materials.And the as-prepared samples were utilized as anode electrodes for LIBs to investigate their electrochemical performances.The major contents of the thesis are summarized as follows:1.N doped carbon materials?NCs?were synthesized through a facile carbonization treatment of a special POFs and applied as anode materials for LIBs.The experimental results show that NCs exhibit excellent performance of lithium ion storage with a reversible capacity of 387.1 mAh g^-1 at 0.1 A g^-1 after 100 cycles and224.4 mAh g^-1 at 1.0 A g^-1 after 1000 cycles.2.Spherical POFs were utilized as an ideal precursor for N,B co-doped carbon spheres?NBCs?with porous hierarchical spherical architecture.When applied as LIBs anodes,NBCs exhibit excellent reversible specific capacity and outstanding long-life cycling stability at high current density(205.5 mAh g^-1 at 5.0 A g^-1 and 171.4 mAh g^-1at 10.0 A g^-1 after 5000 cycles)owing to their hierarchical porosity,unique structure and in-situ N,B co-doping.3.S-doped POFs were prepared through a conventional solution phase reaction method and used as the precursor for in-situ preparing S-doped porous carbons?SCs?.When used as anode for LIBs,SCs exhibit a high reversible capacity of 760.5 mAh g^-1 at a current density of 0.1 A g^-1 after 100 cycles,superior rate capability and excellent cycling stability(682.3 mAh g^-1 after 1000 cycles at 1.0 A g^-1)...