【作者】 李加新；

【导师】 黄志高；

【作者基本信息】 福建师范大学 ， 凝聚态物理， 2015， 博士

【摘要】 随着现代经济的高速发展,发展节能技术是解决当今社会发展中能源危机和环境污染等重大问题及实现低碳经济的必然选择。当下,研发高端锂二次电池势在必行,特别是高性能第三代锉离子电池和新型有机系锂空气电池受到广泛关注。针对第三代锂离子电池技术,发展高性能的负极材料是最重要的内容之一,尤其是要通过提升负极材料电子电导和离子电导来确保电池在低温下仍具高性能。针对有机系锂空气电池,制备出高效的“双功能”催化剂及实现有效微结构正极的构筑是研制的关键。基于上述,本文研究围绕以下四个部分展开：(一)利用纳米碳管材料提升电导和有效控制活性材料在充放电中的膨胀,进而增强锂离子电池负极性能的研究(二)碳纤维基锂离子电池负极及其电导增强锂电池低温性能的研究；(三)通过几种碳基“双效”催化剂的制备,实现增强材料电导、提升催化剂高分散及高活性,进而获取高性能的锂空气电池的研究；(四)通过具有有效微结构正极的构筑,克服传统涂抹电极中微空间分布欠缺、电极电导差、催化剂分散度低等难点,最终实现高性能锂空气电池的制备。一、纳米碳管材料增强锂离子电池负极性能的研究。一方面,将合成的～4 nm的SnO2颗粒均匀地与单壁碳纳米管(SWNTs)进行液相超声混合获得SnO2/SWNT复合材料,并直接用作锂离子电池负极的研究。结果表明,所合成的复合材料表现出优异的电化学性能,在100mA g-1的电流密度下经过70次循环后,比容量稳定在930 mAh g-1。另一方面,采用化学氧化聚合法,在MWNTs/MnO2的表面引入聚吡咯涂层,形成均匀的有机-无机杂化材料,同轴MWNTs@MnO2@PPy复合电极材料进而提高锂电池的电化学性能。纬果表明,MWNTs@MnO2@PPy表现出明显优异的电化学性能,包括可逆容量、循环性能和倍率性能,在1000mA g-1电流密度下300次循环后存有530 mAh g-1的高容量。二、碳纤维基锂离子电池负极及其电导增强低温性能的研究。一方面,通过青电纺丝制备SnCu/SnOx的氮掺杂碳纳米纤维,并直接利用碳纤维纸片电极进行裁用作为锂电池负极加以研究。这种电极集合金化处理、结构调控、纳米化分散处理及复合碳载体的自支撑结构等优点,能出现优异的电池性能,在200mA g-1测试10次循环后,几乎没有容量损失并保持470 mAhg-1的高可逆容量。另一方面,通过一个简单的静电纺丝法引进廉价可靠的铁金属来原位形成均匀的Fe/Fe3C内米碳纤维复合负极材料。其中,Fe纳米粒子可增强材料的低温电导,Fe3C可催化电极反应时的固态电解质膜有效提供可逆容量,这样获得的负极材料能提供高的电池容量,并在低温下表现出优异的性能。三、几种纳米结构碳基“双效”催化剂的制备及其锂空气电池性能研究。首先,通过湿化学方法制备了多壁碳纳米管负载纳米梭型的β-FeOOH的复合材料(β-FeOOH/MWNTs),并用此材料研究其锂空气电池的性能；所组装的锂空气电池具有高的可逆容量,良好的倍率性能和循环稳定；电池性能优于纯P-FeOOH,归因于MWNTs能为复合材料带来良性的协同作用。其次,用简单的水热方法在多壁碳纳米管负载三元尖晶石MFe2O4(M= Co,Ni)纳米粒子,形成催化剂复合物MFe2O4 (M=Co,Ni)/CNTs,并详细研究复合物MFe2O4CNTs的锂空电池的电化学性能。最后,采用电纺丝方法合成一种新型的Fe/Fe3C-CNFs复合材料,并用于锂空气电池正极催化剂的性能研究。该Fe/Fe3C-CNFs催化剂在锂空气电池中应用时能表现出优良的性能：在200mA/g测试报有容量6250 mAh/g,并在定容量为1200 mAh/g时循环稳定20个周期,定容量为600 mAh/g时循环稳定40次四、锂空气电池用碳基电极的原位构筑及性能研究。通过化学气相沉积法结合磁控溅射路径,设计并制备出无粘结剂的泡沫镍负载Pt/碳纳米管的复合自支撑电极(Pt/CNTs-NF),并直接用于锂空气电极的研究。结果表明,所制备的电极具有更合适三位微空间结构,具备如下的电极优势——高比表面积、良好的导电性和催化剂的高分散型及电催化活性,所组装的锂空气电池可以提供优异的电化学性能。测试结果表明,Pt/CNTs-NF电极在160mA g-1且定容量为800 mAh g-1的充放电循环达到20次,电极放电平台电位和充电平台电位约为2.7和4.0V,说明较好的循环能量效率；特别是,在400mA g-1且定容量为1500 mAh g-1的充放电循环可达80次,相对应地,电极材料的能量密度约为3000 Wh kg-1显示了优异的循环稳定性更多还原

【Abstract】 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更多还原