基于锂硅合金负极锂离子—氧气电池的制备和性能

发布时间：2018-06-25 11:01

  本文选题：二次电池 + 锂-氧气电池　； 参考：《南京大学》2017年硕士论文

【摘要】：环境污染和能源短缺制约人类的可持续发展。为此,大力发展清洁可再生能源,已经成为人类社会的共识。清洁能源的存储和利用要求性能良好的能量存储转化设备。锂-离子电池自上世纪末问世以来,在移动便携设备领域取得了极大的成功。但是,由于其活性物质固有化学性质的限制,锂-离子电池有限的能量密度难以满足长距离续航里程电动汽车的要求。锂-氧气电池利用大气中的氧气和金属锂参与反应,具有可与以汽油为燃料的内燃机相媲美的理论能量密度。然而,金属锂负极受制于锂枝晶生长和低库伦效率的问题,目前还难以在获得实际应用。针对这一问题,研究者提出使用合金负极材料以取代金属锂负极,从而构建锂离子-氧气电池的设想。硅基材料由于其较高的理论比容量和较低的工作电位,被认为是锂离子-氧气电池的一个合适选择。本文基于硅基合金负极材料,对锂离子-氧气电池进行了设计和组装,并通过XRD、SEM、TGA、XPS以及充放电测试等分析方法,探究了非锂负极锂离子-氧气电池的电化学性能及充放电反应过程。我们首先合成了两种基于多壁碳纳米管的复合催化剂材料,用于锂离子-氧气电池的正极。在铂修饰多壁碳纳米管材料中,少量金属铂纳米颗粒均匀生长在多壁碳纳米管管壁上;在核壳结构二氧化钌多壁碳纳米管材料中,大量二氧化钌晶体包覆在多壁碳纳米管外,形成了核壳结构。铂修饰多壁碳纳米管复合材料作正极的锂-氧气电池在定容量充放电条件下能够稳定循环100圈。核壳结构二氧化钌多壁碳纳米管复合材料作正极的锂-氧气电池可以有效降低充电过电位。并且可以在较大电流密度下实现了稳定全充放循环。通过对铂修饰多壁碳纳米管的充放电产物进行表征,证明电池的放电充电过程基于Li2O2晶体的可逆生长和分解。由于硅基材料不含锂,不能直接作为锂离子-氧气电池的负极材料,我们通过高能球磨法制备了锂硅合金负极材料。锂硅合金主要成分为Li21Si5,且颗粒尺寸分布在1 μm到5 μm。电化学性能测试表明锂硅合金首圈脱锂比容量为1118 mAh·g-1。锂硅合金在大电流条件下50圈充放电循环后依然保持了 571 mAh·g-1的可逆容量,同时,库伦效率稳定在98.5%左右。使用锂硅合金负极和铂修饰多壁碳纳米管正极组装锂离子-氧气电池,在500 mA·g-1的电流密度下可以稳定循环80圈。同时我们还对不同正负极质量配比的锂离子-氧气电池的循环稳定性进行了研究。通过对比循环前后的锂硅合金电极,我们发现锂硅合金在循环过程中逐渐转化为无定形态。同时,循环过程中生成了 LiOH以及少量醚类物质等副产物。我们认为这造成了锂硅合金材料在循环过程中的不稳定。我们还设计并组装了一种新型铝塑膜软包装锂离子-氧气电池,通过预装金属锂源对硅电极进行电化学锂化。使用基于海藻酸钠粘结剂涂膜的纳米硅电极作为锂离子-氧气电池负极,其首圈放电比容量为3087.8 mAh·g-1。在0.25 C的电流密度下稳定循环200圈,可逆比容量达到1500.2 mAh·g-1,容量保持率高达75.4%。组装软包电池后,通过反复的放电与静置操作,对硅电极进行电化学锂化,该体系下生成的锂硅合金成分主要为Li21Si8。以此为基础进行锂离子-氧气电池的测试,电池放电比容量为343.1 mAh·g-1,且库伦效率达到100%。该方法在既可以实现电化学方法锂化硅电极,同时又避免了电池反复拆解组装带来的问题。通过上述几个方面,我们对不同结构的基于锂硅合金负极的锂离子-氧气电池进行了初步的研究。这将为未来锂离子-氧气电池的结构设计和性能优化提供新的思路。
[Abstract]:Environmental pollution and energy shortage restrict the sustainable development of human beings. To this end, the development of clean and renewable energy has become a common understanding of human society. The storage and utilization of clean energy requires good performance of energy storage conversion equipment. Lithium ion batteries have come from the end of last century and have made a great deal in the field of mobile portable equipment. However, due to the inherent chemical properties of its active substance, the limited energy density of lithium ion batteries is difficult to meet the requirements of a long range mileage electric vehicle. The lithium oxygen battery takes part in the reaction with the oxygen and metal lithium in the atmosphere, and has a theoretical energy density comparable to that of gasoline as a combustion engine. The metal lithium anode is subject to the problem of lithium dendrite growth and low Kulun efficiency, and it is still difficult to get practical application at present. In view of this problem, the researchers have proposed the use of alloy negative electrode to replace the metal lithium anode to construct the lithium ion oxygen battery. The silicon base material is from its higher theoretical specific capacity and lower working power. It is considered to be a suitable choice for lithium ion oxygen batteries. Based on the silicon based alloy negative electrode, the lithium ion oxygen battery was designed and assembled. The electrochemical performance and charge discharge reaction process of the non lithium negative lithium ion oxygen battery were investigated by means of XRD, SEM, TGA, XPS and charge discharge test. We first synthesized two kinds of composite catalysts based on multi walled carbon nanotubes for the cathode of the lithium ion oxygen battery. In the platinum modified multi walled carbon nanotubes, a small amount of platinum nanoparticles grow evenly on the wall of the multi wall carbon nanotube. In the nuclear shell structure two ruthenium oxide multi wall carbon nanotube materials, a large number of ruthenium oxide crystals are found. The body is coated with multi wall carbon nanotubes, forming a nuclear shell structure. The lithium oxygen battery with platinum modified multi wall carbon nanotube composite material can stabilize 100 cycles under the constant capacity charge and discharge condition. The lithium oxygen gas battery of the nuclear shell structure two ruthenium oxide multi wall carbon nanotube composite material can effectively reduce the charge overpotential. The charge discharge product of the platinum modified multi wall carbon nanotubes is characterized by the characterization of the charge and discharge products of the platinum modified multi wall carbon nanotubes. It is proved that the discharge charging process of the battery is based on the reversible growth and decomposition of the Li2O2 crystal. Lithium silicon alloy negative electrode is prepared by ball milling. The main component of lithium silicon alloy is Li21Si5, and the particle size distribution from 1 to 5 m. shows that the lithium silicon alloy first coil stripping ratio is 1118 mAh. G-1. lithium silicon alloy still maintains the reversible capacity of 571 mAh. G-1 after 50 ring charge discharge cycle under large current condition. At the same time, the efficiency of Kulun is stable at about 98.5%. Lithium ion oxygen battery is assembled with lithium silicon alloy negative electrode and platinum modified multi wall carbon nanotube cathode. The cycle of 80 cycles can be stabilized under the current density of 500 mA. G-1. The cycle stability of lithium ion oxygen batteries with different positive and negative mass ratio is also studied. Compared with the lithium silicon alloy electrode before and after the cycle, we found that the lithium silicon alloy was gradually transformed into an amorphous form during the cycle process. At the same time, LiOH and a small amount of other products were produced during the cycle process. We think this resulted in the instability of the lithium silicon alloy during the cycle process. The plastic film soft packaging lithium ion oxygen battery is electrochemical lithium ion by preloading the metal lithium source. The nano silicon electrode based on sodium alginate adhesive coating is used as the anode of the lithium ion oxygen battery. The discharge ratio of the first coil is 200 cycles at the current density of 3087.8 mAh. G-1. at 0.25 C, and the reversible specific capacity reaches 1. After 500.2 mAh. G-1, the capacity retention rate is up to 75.4%. package battery, the silicon electrode is electrochemical lithium by repeated discharge and static operation. The composition of the lithium silicon alloy under this system is mainly Li21Si8. on the basis of the lithium ion oxygen battery test. The battery discharge specific capacity is 343.1 mAh. G-1 and Kulun efficiency. To achieve 100%., this method can not only realize the electrochemical method of lithium silicon electrode, but also avoid the problems caused by repeated disassembly and assembly of the battery. Through the above several aspects, we have studied the lithium ion oxygen battery based on the lithium silicon alloy anode of different structures. This will be the structure of the lithium ion oxygen battery in the future. New ideas are provided for planning and performance optimization.
【学位授予单位】：南京大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM911.41
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本文编号：2065684