Al与Al基金属间化合物作为锂离子二次电池负极材料的研究

【作者】 谢维；

【导师】 苏玉长；

【作者基本信息】 中南大学 ， 材料物理与化学， 2005， 硕士

【摘要】 为了寻求更好的新型非碳材料作为锂离子二次电池负极材料,本论文采用Al极片和高温真空熔炼制备的Al基金属间化合物（Al—Y,Al—Cu）作为负极材料,利用X射线衍射法、扫描电镜、微电极循环伏安法、恒电流充放电测试及交流阻抗测试等,研究了材料的结构、脱嵌锂机理和电化学性能,主要结论如下: 1.采用Al极片作为锂离子二次电池的负极材料在循环中表现出较好的综合性能,容量可到达400mAh/g,高于石墨理论容量。在充放电循环过程中,Al与Li的反应基本上生成的是AlLi合金,随着反应的深入,生成少量Al₄Li₉。在控制电化学测试条件上,对于Al极片先采用小电流充电使其活化,再改用大电流充放电可得到较大的比容量性能。 2.实验制得的Al-Y试样在0.5V电压左右出现尖锐的氧化峰,而还原峰电位为0.3V左右,氧化/还原峰电位差为0.2V左右,表明其极化较小。Al-Y试样的容量可达到500mAh/g,超过石墨的理论容量,但容量首次循环后衰减很大,合金物质在充放电循环中体积变化依然很大程度导致负极中材料颗粒破碎、脱落,从而引起参加电化学反应的有效活性物质的质量的减少,导致可逆容量下降。其循环性能仍有待于进一步提高。 3.制备的Al-Cu试样氧化峰电位为0.5V左右,还原峰电位为0.1V左右。循环伏安曲线重合度较好,显示具有一定的电化学性能。Al-Cu在恒电流循环测试中,显示容量可达到500mAh/g。十次循环后,其循环效率较高,显示其作为替代石墨负极材料的巨大潜力。 4.通过交流阻抗测试,初步估算了Al极片在充放电过程中的Li扩散系数的数量级为10^-10～10^-13cm²/s之间。更多还原

【Abstract】 In search of new non-carbonaceous anode material for lithium ion secondary batteries, Aluminum and Al-based intermetallic compound （Al-Y, Al-Cu） prepared by hot vacuum casting were tested as negative materials. Their crystal structures , mechanism of Lithium intercalation and electrochemical performances were studied by XRD, SEM, micro-electrode cyclic voltammetry, galvanostatic charge/discharge test and measurement, AC impedance measurement and so on. The conclusions were showed as following:1. Aluminum electrode showed relatively good property in the cycles as negative material of lithium-ion secondary batteries . Its capacity reached 400mAh/g ,which is higher than the theoretical capacity of carbon. During charge-discharge progress, Al reacted with Li to form AlLi where somewhat Al₄Li₉ was formed afterwards. Small current charge could activate aluminum and following larger current could show its relatively large capacity.2. The oxidation peak of Al-Y samples was observed at about 0.5V and reductive peak at 0.3V. Their potential difference was about 0.2V, which meant their polarization was small. The capacity of Al-Y reached 500mAh/g, but capacity faded significantly after the first cycle due to the great volume change of alloy in cycles resulting the break-down of the grains of negative materials ,which led to the decrease of amount of effective and active materials. The cyclic performance should be improved.3. The oxidation peak of Al-Cu samples was observed at about 0.5V and reductive peak at 0.1V. cyclic voltammetry curves overlapped well ,which indicated certain electrochemical property. Al-Cu sample reached 500mAh/g whose cyclic efficiency was relatively high ,which suggested its potential to replace carbon..4. The order of magnitude of lithium diffusion coefficient in aluminum was estimated at 10^-1010^-13cm/s by AC impedance measurement.更多还原