【作者】 陆君；

【导师】 李亚栋；

【作者基本信息】 清华大学 ， 化学， 2013， 博士

【摘要】 随着世界性环境和能源问题日益严峻，锂离子电池以高效、清洁、高能量密度等优点备受瞩目。研究高能量密度、高功率、高安全性、长寿命和低成本的锂离子电池正负极材料，是锂离子电池发展和应用的关键问题。多种新型正负极纳米材料，如钛酸锂、氧化铁、锡基化合物、三元材料以及锰酸锂，具有高倍率、安全稳定、低成本等特点，有望发展为下一代锂离子电池电极材料。本论文以上述正负极材料为研究对象，以优化其电化学性能为目的，探索了多种纳米材料制备方法，实现了材料电化学性能的提升。发展了钛酸锂纳米晶的低温固相合成方法。选择介稳的立方相钛酸锂的纳米晶为前驱体，研究了其Li+-H+交换过程、热稳定性以及转化温度，实现了钛酸锂纳米晶的低温固相合成。因其大比表面和小尺寸，钛酸锂纳米晶显示出优异的倍率性能，5C下容量达162mAh/g。研究了氧化铁纳米片的溶剂热合成方法。通过调控反应条件，使材料沿ab平面生长最终生成纳米片，且生长过程符合Ostwald熟化机制。因其小尺寸，氧化铁纳米片具有优异的电化学活性，循环稳定性和倍率特性，600mA/g循环150圈容量保持540mAh/g，2400mA/g容量280mAh/g。发展了硫化亚锡纳米带的水热合成方法。通过调控反应条件，使SnS按Ostwald熟化机制沿[020]方向生长成纳米带。SnS纳米带具有良好的柔韧性和电化学活性。尤其值得关注的是，在电池循环之后，SnS纳米带因其一维结构对应力和体积变化的良好承受能力，很好地保持了一维纳米结构。构建了表面富Li₂TiO₃的三元材料纳米带制备方法。调控合成多元金属草酸盐纳米带，利用其受热失水性质设计包覆方法，并通过高温固相反应，获得表面富Li₂TiO₃的三元材料纳米带。因钛酸锂在a-b平面和c轴方向上有锂离子通道，减小了表面锂离子迁移的阻抗，且性质稳定，故包覆纳米带体现出非常优异的常高温倍率和循环性质。发展了包覆-掺杂改性的锰酸锂纳米棒材料的合成方法。以MnOOH纳米棒为前驱体，利用其受热失水性质设计包覆方法，获得了Li₂SiO₃包覆，和Li-Ti-Mn-O包覆且Ti4+掺杂的锰酸锂纳米棒。因包覆层抑制副反应促进界面电荷转移，Ti4+掺杂提高结构稳定性，改性的锰酸锂纳米棒具有优异的常高温倍率和循环性能。更多还原

【Abstract】 Lithium ion batteries have attracted intensive attention for their merits includingclean, high efficiency and energy density, with the increasing urgency of the globalenvironmental and energy crisis. The research and development of electrode materialswith high energy density, high power capability, good safety, long durability and lowcost are the key challenges towards the development and application of lithium ionbatteries. Several electrode nanomaterials including Li4Ti5O12, Fe2O3, Sn-based alloys,LiMO2and LiMn2O4have been regarded as candidates for the electrode materials ofnext-generation lithium ion batteries, for their advantages of high rate, high safety andlow cost. In this dissertation, several synthetic methods have been established forabove-mentioned nanomaterials to improve the comprehensive performances.A low-temperature solid state method has been developed forLi4Ti5O12nanocrystals. A metastable nanocrystals cubic Li₂TiO₃has been chosen as theprecursor. By investigating the Li+-H+exchange reaction, stability to heat as well asconversion temperature of cubic Li₂TiO₃, Li4Ti5O12nanocrystals has been prepared bysolid state reaction under relative low temperature. Li4Ti5O12nanocrystal has showninspiring high rate capability with162mAh/g under5C, due to its large surface areaandsmall size.A solvothermal method for Fe2O3nanodiscs has been investigated. By tuningsynthetic conditions, the growth direction of Fe2O3has been confined in a-b plane andeventually grown to nanodiscs, following Ostwald ripening mechanism. NanosizedFe2O3nanodiscs exhibit high electrochemical reactivity as well as outstandingcyclingand rate capabilities, delivering540mAh/g after150cycles under600mA/g and280mAh/g under2400mA/g.A hydrothermal method has been proposed for SnS nanobelts. SnS nanobelts haveformed via growing along [020] direction under well controlled condition, observingOstwald ripening mechanism. SnS nanobelts have shown sound flexibility andelectrochemical properties, and the one-dimensional structure has been well preservedafter cycles of volumetric expansion due to Li+insertion due to the flexibility ofnanobels for strains.Approach for surface-Li₂TiO₃-rich LiMO2nanobelts has been established. A series of mixed metal oxalate nanobelts has been prepared as precursor, and coating methodhas been designed based on the thermal decomposition property of the precursor; viasolid state reaction surface treated LiMO2nanobelts have been obtained.Surface-Li₂TiO₃-rich LiMO2nanobelts have exhibited excellent rate and cyclingcapabilities, because the coating materials Li₂TiO₃is stable with electrolyte and has athree-dimensional Li+diffusion path which help to reduce the surface charge transferand reduce the surface side reaction.Approach for constructing LiMn2O4nanorods combined with coating and dopingtreatment has been proposed. Li₂SiO₃coated nanorods and Li-Ti-Mn-O coated nanorodswith Ti4+doping have been prepared applying MnOOH as the precursor. The coatingmethod is also based on the thermal decomposition reaction of MnOOH. ModifiedLiMn2O4nanorods have inspiring electrochemical performance, due to the reducedsurface charge-transfer resistance by Li₂SiO₃and Li-Ti-Mn-O, and increased structuralstability by Ti4+doping.更多还原