【作者】 陈湘平；

【导师】 周震涛；

【作者基本信息】 华南理工大学 ， 材料物理与化学， 2010， 博士

【摘要】 二氧化锡具有嵌锂电位低、容量密度高、安全性能好、资源丰富、价格便宜以及对环境无污染等突出优点，被认为是锂离子电池碳负极材料最有希望的替代物之一。但是，它同时也存在所成电池的循环可逆性能差、大倍率充放电性能不佳以及能量密度较低等缺点，无法满足锂离子动力电池的性能要求，从而阻碍了它作为锂离子电池负极材料的实用化进程。针对这些问题，本论文分别通过在平面铜箔上电沉积制备SnO2纳米薄膜电极、电沉积制备负载铜纳米棒铜箔集流体，再在铜纳米棒之间电沉积SnO2制备得到了铜纳米棒集流体纳米SnO2电极，并对所得纳米SnO2电极的结构和性能进行了较系统深入的研究，取得了如下的主要结果和结论：1）以阳极氧化铝(AAO)为模板，在铜箔上通过阴极电沉积法制备了铜纳米棒集流体。对铜箔的前处理、沉积条件(电压、铜箔单位面积重量增量、电解液体系)等因素对铜纳米棒团聚、长短一致性的影响进行了考察。研究结果表明，对铜箔进行机械抛光，能有效降低铜箔表面的粗糙度，改善铜纳米棒的长短一致性。本文还研究比较了三种电沉积电解液体系：A)高铜低酸硫酸体系；B)低铜高酸硫酸体系；C)碱性络合体系。通过监控铜箔单位面积重量增量来防止铜纳米棒发生坍塌及团聚。不同电解液体系对铜纳米棒的长短一致性影响较大。当铜箔单位面积重量增量相同时，亦即电沉积得到的铜纳米棒的平均长度相同时，碱性络合体系C中得到的铜纳米棒的长短一致性要明显优于高铜低酸体系A和低铜高酸体系B，而B体系所得到的铜纳米棒的长短一致性最差。碱性络合体系C是制备纳米棒铜集流体的最佳体系。2）在平面铜箔SnO2纳米薄膜电极的研究中，采用恒电压阴极电沉积法，直接在平面铜箔集流体上电沉积制备纳米二氧化锡薄膜电极，并对所得电极上活性材料的成分、表观形貌及电性能等进行了研究。结果表明，要使电沉积产物为纯的SnO2，就应保证反应体系中的NO3-与Sn4+的浓度之比不得低于4：1，并使用新鲜配制的电解液。另外，65℃是电沉积制备纯SnO2的临界温度。电沉积电压宜控制在0.4V及以下，以避免电极上的SnO2薄膜由细腻致密而变得粗糙，甚至从电极上自行脱落。对平面铜箔SnO2纳米薄膜电极进行热处理，其电性能没有明显的变化。3）为了制备铜纳米棒集流体纳米SnO2电极，采用恒电压阴极电沉积方法在负载了铜纳米棒的铜集流体上电沉积纳米二氧化锡粒子。研究结果表明，电沉积温度、电沉积电压分别为85℃，0.4V时制备得到的铜纳米棒集流体SnO2电极的电化学性能最佳，电极的表观形貌与其它电沉积条件下所得电极的表观形貌有较大的差别。另外，应控制SnO2在铜纳米棒集流体上单位面积的载量有合适的范围，以避免铜纳米棒之间的空隙被沉积过多的SnO2所填满，甚至在电极的表面发生大量团聚和堆积，使得电极丧失铜纳米棒这一纳米结构所带来的优点，造成电池的电化学性能下降。4）对铜纳米棒集流体纳米SnO2电极、平面铜箔集流体电沉积SnO2纳米薄膜电极、以及平面铜箔集流体商购SnO2纳米粉末电极等三种不同结构形式的纳米电极的电性能进行了对比研究的结果表明，铜纳米棒集流体纳米SnO2电极与其它两种电极相比，其放电比容量要大得多，大倍率下的比容量优势更加明显。铜纳米棒集流体纳米SnO2电极经多次大倍率充放电循环后的表观形貌变化不大，没有出现裂痕或原有裂痕扩大的现象，显示出良好的结构稳定性以及优良的循环可逆性能。更多还原

【Abstract】 Due to the outstanding advantages such as low Li+intercalation voltage, high capacityintensity, excellent safety, rich resource and low cost, SnO2is considered to be an attractivesubstitute of carbon negative materials for Li-ion batteries. However, the main obstacles forthe industrialization of SnO2as negative material are its drawbacks: relatively low cyclingreversibility, poor rate capability and low power density, which makes it can’t fulfill therequirement of Li-ion batteries for electric vehicles. To overcome those drawbacks of SnO2, Itried two ways:1) electrodeposited SnO2on planar Cu foils to fabricate SnO2nano-filmnegative electrodes,2) electrodeposited Cu nanorods on planar Cu foils to obtain, thenelectrodeposited SnO2nano particles around Cu nanorods to fabricate nano-structured SnO2negative electrodes based on Cu nanorods current collectors. A systematic and detailed studyon the fabricated nano SnO2negative electrodes has been carried out. Main research resultsare listed as below:1) Arrays of Cu nanorod were fabricated by cathodic electrodeposition inside thenanopores of anodized alumina oxide (AAO) templates. Three electrolyte systemswere tested and compared. Two of them were acid copper sulfate based solutions,including conventional solution A and high-throw solution B. The third one wasalkaline solution. The influence of electrodeposition conditions, such aspredeposition polishing, deposition voltage, and deposition duration, on theaggregation and Cu nanorod arrays were investigated in detail. It was found thatcareful mechanical polishing effectively reduced the surface roughness of Cucathodes and avoided the formation of continuous Cu layer. Properties of electrolytesand form of copper ions in the electrolytes greatly affected the uniformity ofdeposited Cu nanorods. Nanorods electrodeposited in electrolyte B with the highestH2SO4concentration demonstrated the worst uniformity, while the most uniformnanorods were fabricated in alkaline electrolyte C. Using the weight gain per unitarea of cathode as a direct measure of average length of deposited Cu nanorods andby controlling the weight gain to be in the range of1.2～1.4mg/cm2, free-standingCu nanorod arrays have been successfully obtained by electrodeposition inelectrolyte A and C.2) Pure SnO2films were successfully fabricated on Cu substrates by one-step cathodicelectrodeposition without the pretreatment of electrolytes. Electrodepositionparameters, such as the concentration of HNO3, aging of the electrolyte, thedeposition voltage, and temperature, were demonstrated to be critical to eliminate theco-deposition of Sn. It was found that the ratio of the concentration of HNO3to SnCl4, aging of the electrolytes, the electrodeposition temperature, and the depositionvoltage were important parameters impacting both the morphology and the phase ofthe deposits. By carefully controlling these processing conditions, dense SnO2filmswith good adherence to the Cu substrate were successfully obtained. The electrodesloaded with SnO2films were annealed, then fabricated into coin cells. The cellstesting results showed that their electrochemical properties were not improvedcompared to the electrode without annealing.3) To fabricate nano-structured SnO2electrodes based on Cu nanorods currentcollectors, we prepared Cu current collectors loaded with Cu nanorod arrays, thenload SnO2active materials on the Cu nanorod arrays by catholic potentiostaticdeposition technique. It was found that electrodes prepared under85℃electrodeposition temperature and0.4V electrodeposition voltage had the bestelectrochemical properties, and their morphology were rather different from that ofelectrodes prepared under other electrodeposition conditions. Besides, the weightgain of SnO2on per unit area of Cu nanorods current collectors should be carefullycontrolled to avoid that the space between Cu nanorods are fully occupied by SnO2particles, thus lose the advantages brought by nano structure and worsen theelectrochemical properties of fabricated cells.4) Electrochemical properties of three types of nano electrodes were tested andcompared: SnO2electrodes based on Cu nanorods current collectors, SnO2electrodesbased on planar Cu current collectors and nano-powder SnO2electrodes based onplanar Cu current collectors. The results showed that the discharging specificcapacity of SnO2electrodes based on Cu nanorods current collectors was muchhigher than that of other two types of electrodes, especially under high dischargingrate. The morphology of SnO2electrodes based on Cu nanorods current collectorshad minor changes after many cycles, and no crackles were found. This kind ofnano-structured electrodes showed excellent structure stability and cyclingperformance.更多还原