| With the rapid development of current economy, novel energy-saving technology should be inevitably developed for solving the present energy crisis and environmental pollution in society and for further achieving a low-carbon economy. Recently, great research effort is devoted to develop high-performance lithium secondary batteries, especially for the third generation high-performance lithium batteries and new lithium air batteries with organic electrolyte. With regard to the third generation high-performance lithium batteries, it is of vital importance for developing the high-performance anodic materials. Especially, to improve the electronic conductance and ionic conductivity for obtaining the lithium batteries with good low-temperature performance is.desired. On the other hand, to optimize and select high-performance bifunctional catalysts and then to fabricate cathodes with effective microstmcture is critical issue for the development of lithium air batteries using organic electrolyte. Based on the above, this doctoral dissertation studies around about four parts:(a) The nano-carbon materials were used to improve the conductivity for anodic composites and to control their expansion in the charge-discharge process, thus enhancing the performance of lithium batteries; (b) The carbon fiber based anodic materials with enhanced conductivity were prepared and used to study their lithium battery performance especially at the low temperature; (c) Several carbon based bifunctional catalysts with high-dispersion and high-catalytic activity were fabricated to obtain the high-performance lithium air batteries; (d) To fabricate cathodes with effective microstructure for overcoming by having effective micro structure of cathode construction, to overcome the low conductance and poor spatial distribution in typical coating electrodes, and thus to achieve the high-performance lithium air batteries.(a) The nano-carbon anodic materials for lithium batteries. On the one hand, Anode of-4nm SnO2/SWNT material with high electrochemical performance has been fabricated via a facile ultra-sonic method. The SnO?/SWNT composite delivered a high reversible capacity of 910 mAh g-1 cycled at 100 mA g-1 after 70 cycles and exhibited superior rate capability. On the other hand, coaxial MWNTs@MnO2 confined in conducting polypyrrole (PPy) has been synthesized through an in situ oxidation-polymerization of pyrrole monomers in the presence of prepared MWNTs@MnO2. As an anode in lithium batteries (LIBs), the obtained MWNTs@MnO2@P.Py shows a high reversible capacity of 530 mAh g-1 tested at 1000 mA g-1 even after 300 cycles and an excellent rate performance.(b) The carbon fiber based anodic materials for lithium batteries especially at the low temperature. Self-standing paper of N-doped carbon nanofibers loaded with SnCu/SnOx materials has been integratively prepared by electrospinning and directly used as anode for lithium ion batteries. This anode possessed good morphology modulation, alloyable treatment, disperse tin-based materials and self-standing electrode architecture, can affords excellent electrochemical performance with a reversible capacity of 470 mAh g-1 tested at 200 mAg-1 after 100 cycles. On the other hand, the novel composites of Fe-added Fe3C carbon nanofibers (Fe/Fe3C-CNFs) were synthesized via facile electrospinning method and used as anode materials for LIBs. The Fe nanoparticles can provide an improved low-temperature conductance. And the Fe3C can prompt an additional reversible capacity for the SEI via an catalytic reaction. Thus, the superior low-temperature electrochemical performance of the Fe/Fe3C-CNF anodes can be obtained.(c) Several carbon based bifunctional catalysts with high-dispersion and high-catalytic activity for the high-performance lithium air batteries. Firstly, a novel composite of β-FeOOH nanospindles coated on multi-walled carbon nanotubes (β-FeOOH/MWNTs) has been synthesized via a wet chemical method and used as electrocatalysts for the cathodes of Li-O2 Batteries (LOBs). The β-FeOOH/MWNT cathodes can afford the good LOB performance. It should be attributed to he synergistic effect of the fast kinetics of electron transport through the MWNT support and the high electro-catalytic activity provided by the (3-FeOOH nanospindles. Secondly, ternary spinel MFe2O4 (M= Co, Ni) nanoparticles coated on multi-walled carbon nanotubes (MFe2O4/CNTs) were prepared via a simple hydrothermal method. Owing to their favorable structures and desirable bi-functional oxygen reduction and evolution activities, the resulting MF3O4/CNT composites as electrocatalysts for the cathodes deliver good electrochemical performance during the discharge and charge processes. Thirdly, the novel composites of Fe/Fe3C carbon nanofibers (Fe/Fe3C-CNFs) were synthesized via facile electrospinning method and used as cathode catalysts for Li-O2 batteries. Owing to their favorable structures and desirable bifunctional catalytic activities, the resulting cathodes with Fe/Fe3C-CNF catalyst exhibited superior electrochemical performance with high specific capacity, good rate capability and cycle stability. The Fe/Fe3C-CNF electrode delivered specific capacities of 6250 mAh g-1 at 200 mA g-1, superior cycle stability up to 20 and 40 cycles with curtailed capacities of 1200 and 600 mAh g-1, respectively.(d) The in-situ fabrication for carbon based electrodes for high-performance lithium air batteries. It is presented that a nickel-foam supported composite of Pt nanoparticles (NPs) coated on self-standing carbon nanotubes (CNTs) as a binder-free cathode for LOBs were prepared by a typical chemical vapor deposition combined with DC magnetic sputtering method. The obtained electrodes can provide the excellent catalytic activity of highly dispersed Pt NPs, facile electron transport via loose CNTs connected to the nickel-foam current collector, and fast O2 diffusion through the porous Pt/CNTs networks. Thus, the assembled LOBs can afford excellent electrochemical performance with a reversible capacity of 4050 mAh g-1 tested at 20 mA/g and superior cyclability for 80 cycles with a limited capacity of 1500 mAh g-1 achieved at a high current density of 400 mA/g The capacity is corresponding to a high energy density of～3000 Wh kg-1... |
