【作者】 范奇；

【导师】 唐月锋； 陈延峰；

【作者基本信息】 南京大学 ， 材料物理与化学， 2012， 博士

【摘要】 作为新型能源储能系统的锂离子二次电池由于优越的性能而备受关注,然而,现代的电池工业仍远未能达到获得同时具有高能量密度和高功率密度的“超级电池”的终极目标,所以新型电池材料的研究就显得极为重要。LiFePO4是一种新型的锂离子二次电池正极材料,它具有无毒、高热稳定性、循环性能优越的优点,因而被视为用于新一代电动交通工具、电子设备的最佳候选正极材料之一。但是,纯LiFePO4的电导率和离子迁移率均不理想,因而倍率性能较差。这一缺陷严重地影响了这一材料的实际应用。针对上述问题,本论文主要完成了如下工作：(1)固相反应法合成Li(Fe1-2xTix)PO4/C基于固相反应法发展了两种不同掺杂方法制备Li(Fe1-2xTix)PO4/C(x=0.02,0.04,0.06)。在此基础上,对Ti掺杂样品的电化学性能进行了系统的研究。结果表明,两种掺杂方法都能明显提高材料的电化学性能,但它们的作用并不完全相同。(2)碳热还原法制备Li(Fe1-2xZrx)PO4/C采用碳热还原法制备Li(Fe1-2xZrx)PO4/C (x=0.01,0.02,0.03,0.04,0.06).通过上述工艺,明显抑制了掺杂样品中的Li3PO4的杂相,材料的电化学性能得到明显提高,其中,在所研究的样品中,Li(Fe0.92Zr0.04)PO4/C具有最好的电化学性能和循环稳定性。(3)新型LiFePO4核壳结构的制备和形成机理研究制备了两种新型LiFePO4核壳结构：非化学计量比C@LiFePO4核壳和Ag@LiFePO4/C核壳结构,并对这两种结构的形成机理进行了探讨。本文采用一种优化的固相反应法制备了不同组分的非化学计量比C@LiFePO4核壳结构。材料显示出优越的库仑效率、优良的循环性能和较高的振实密度,能较好地满足高功率动力设备的需求。采用超声电沉积法制备了Ag@LiFePO4/C核壳结构。由于Ag具有较高的电导率并在材料中构成了三维导电网络,材料表现出优异的倍率性能和循环稳定性,可以作为一种潜在的新型正极复合材料。(4)新型LiFePO4-石墨烯材料的制备首次制备了两种新型LiFePO4-石墨烯复合材料：多孔LiFePO4-石墨烯材料和片层状LiFePO4-石墨烯材料。两种材料均体现出了多方面的优越性能,可以很好地满足高功率动力设备的需求。本文将此归因于材料内部具有的由石墨烯构成的三维导电网络和材料自身具有的特殊结构。更多还原

【Abstract】 Lithium ion battery has a bright future as one of new power source technologies for its superior performance. But the global lithium-ion battery industry is far from developing an electric energy storage component suitable in both energy and power that will satisfy the demands of high power application, especially battery electric and hybrid vehicles. LiFePO4is widely regarded as one of the best candidate cathode materials for battery-using of electric or hybrid vehicles because of its advantages of non-toxicity, high thermal stability, low cost, good cycling performance.However, the pure LiFePO4material has very poor rate performance because of its both low electronic and ionic conductivity which limits its practical application as high power density and long-life batteries. In this dissertation, following works are carried out:(1.) To synthesis Li(Fe1-2XTix)PO4/C by solid-state reaction methodTi as the alien element was brought into the LiFePO4with two different methods to improve the performance of LiFePO4. Various Ti-doping LiFePO4of Li(Fe1-2XTix)PO4(x=0.02,0.04,0.06) were prepared by the two methods separately and the effect of Ti-doping to the electrochemical performances of the samples was systematically studied. The results indicate that although both methods can improve the electrochemical properties of the LiFePO4cathode material, the effects of them are obviously diverse.(2.) To synthesis Li(Fe1-2XZrx)PO4/C by carbon thermal reduction methodA series of Li(Fe1-2xZrx)PO4/C (x=0.01,0.02,0.03,0.04,0.06) were prepared by carbon thermal reduction method. With this strategy, the impurity Li3PO4phase can be obviously reduced in the Zr-doped samples which result in the obvious improvement of their electrochemical performance comparing with the un-doped one. The best electrochemical performances were observed in Li(Feo.92Zro.o4)PO4/C as well as good cycle stability.(3.) Novel core-shell structure of LiFePO4shows good electrochemical properties Two novel core-shell structures of LiFePO4as nonstoichiometric C@LiFePO4core-shell and Ag@LiFePO4/C core-shell composites were fabricated with two different methods:Some kinds of nonstoichiometric C@LiFePO4core-shell composites are synthesized by a novel solid-state reaction method. All samples by this method show outstanding coulombic efficiency and good battery cycleability, along with high tap density, Which might meet the needs of high power applications.Ag@LiFePO4/C core-shell particles were prepared by a facile and one-step ultrasonic electrodeposition method for the first time. Due to the high electronic conductivity of the networks composited of Ag nanoparticles, high charge/discharge rates and cyclability of the LiFePO4/C electrodes were observed. As a result, the Ag@LiFePO4/C core-shell cathode material displays excellent electrochemical performances, indicating the potential application in high power situation of this core-shell composite cathode material.(4.) LiFePO4-graphene composites show excellent electrochemical propertiesTwo hierarchical superstructure graphene-sheets based LiFePO4composites of porous LiFePO4/graphene and nanosheet LiFePO4/graphene were prepared for the first time. Due to the high-conductivity3D network formed by the evenly distributed graphene-sheets and special microstructures, these two novel composites show high-performance which might meet the demands of high-power and high-energy battery applications.更多还原