高性能钠离子电池负极材料研究

发布时间：2018-03-26 01:57

本文选题：钠离子电池　切入点：负极　出处：《华中科技大学》2015年硕士论文

【摘要】：随着全球人口增长,社会整体生活水平的提高,移动互联时代的到来,我们能源消耗量不断增加,对于二次电池的需求量也越来越大。Tesla纯电动汽车的推出引爆了电动汽车产业,电动汽车产业成了各大厂商竞相驰骋的一片绿地。同时,越来越恶劣的环境也催促我们尽快调整我们的能源结构。因其高电压、高能量密度以及好的循环稳定性等特点,锂离子电池被视为是电动汽车的动力电源。然而,锂资源在地壳中的丰度很低,这成为锂离子电池应用的一个瓶颈。钠资源丰富,而且钠的化学性质和锂相似。钠离子电池的研究获得广泛关注,开发性能优异的钠离子电池正负极材料极为关键。本论文旨在探索和研究性能优异的储钠负极材料。锑(Sb)被认为是极有潜力的钠离子负极材料,其理论比容量较高(660m Ah g-1)。然而,锑在脱嵌钠过程中有较大的体积效应,完全嵌钠后体积是没有嵌钠时的390%。在反复脱嵌钠过程中,Sb颗粒会逐渐粉化,储钠容量逐渐损失。通过将锑颗粒纳米化及对其进行碳包覆可有效克服这一缺点。本论文采用水溶性的高分子——壳聚糖——作为碳源,简便地合成了碳包覆的纳米锑复合材料。得益于高分子链段上较多的有机基团(-OH、-C=O、-N-H等),壳聚糖有极强的吸附重金属离子的能力,在合成过程中能吸附在形成的锑氧化物颗粒表面,控制颗粒大小,从而为得到碳包覆的纳米锑复合材料创造了良好的条件。合成得到的碳包覆纳米锑(Sb/C)材料表现出较高的容量,极好的循环性能和倍率性能。在500mA g-1的电流下充放电,可逆比容量为402m Ah g-1;在相同电流充放电下,100圈循环后容量保持率为94%。即使在32A g-1的大电流充放电下,其可逆容量还有138m Ah g-1,表明其极好的倍率性能。有研究发现虽然红磷有极高的储钠容量,但是红磷的电导率极低且体积效应巨大,因此难以直接将其用作钠离子电池负极。然而磷在底壳中的储量丰富,且过渡金属磷化物物质丰富,如果能找到合适的磷化物作为钠离子电池负极而不是直接使用磷,一种低成本的钠离子电池负极有可能被应用。通过文献调研以及实验探究,本论文成功合成碳包覆的纳米二磷化铜材料,并首次将其作为钠离子电池负极材料。合成的碳包覆纳米二磷化铜(CuP2/C)材料拥有极好的储钠性能。在150mA g-1电流充放电循环下,10圈循环后,可逆储钠容量稳定在600.2mAh g-1,是一种极有潜力的低成本钠离子电池负极。
[Abstract]:With the growth of the global population, the improvement of the overall living standards of the society, the arrival of the era of mobile interconnection, our energy consumption is increasing, and the demand for secondary batteries is also increasing. Tesla's introduction of pure electric vehicles has detonated the electric vehicle industry. The electric vehicle industry has become a piece of green space for all the major manufacturers. At the same time, the increasingly bad environment is also urging us to adjust our energy structure as soon as possible, because of its high voltage, high energy density and good cycle stability. Lithium-ion batteries are regarded as power sources for electric vehicles. However, the low abundance of lithium in the earth's crust has become a bottleneck in the use of lithium-ion batteries. And the chemical properties of sodium are similar to those of lithium. It is very important to develop cathode material of sodium ion battery with excellent performance. This paper aims to explore and study sodium negative electrode material with excellent performance. Antimony (SB) is considered to be a potential sodium ion anode material with a high theoretical specific capacity of 660mAh g ~ (-1). Antimony has a larger volume effect in the process of sodium removal, and the volume after complete sodium embedding is 390% when sodium is not embedded. In the process of repeated desorption, the SB particles will gradually become powdered. The capacity of sodium storage is gradually losing. This shortcoming can be effectively overcome by nanocrystalline and carbon coating of antimony particles. In this paper, a water-soluble polymer, chitosan, is used as a carbon source. Carbon coated antimony nanocomposites were synthesized easily. Due to the large number of organic groups in the polymer chain, such as the organic groups such as -OH- Con-N-H and so on, chitosan has a strong ability to adsorb heavy metal ions and can be adsorbed on the surface of the formed antimony oxide particles during the synthesis process. Controlling the particle size creates good conditions for the preparation of carbon coated antimony nanocomposites. The synthesized carbon coated antimony nanocrystalline SB / C composites exhibit high capacity. Excellent cycle performance and rate performance. The reversible specific capacity is 402m Ah g-1 at the current of 500mA g-1, and the capacity retention is 94 after 100 cycles at the same current charge and discharge. Even at the high current of 32A g -1, the capacity retention is 94%. Its reversible capacity is 138mAh g-1, which indicates its excellent rate performance. Although red phosphorus has extremely high sodium storage capacity, the conductivity of red phosphorus is extremely low and the volume effect is huge. It is therefore difficult to use it directly as a negative electrode for sodium ion batteries. However, phosphorus is abundant in the bottom shell and transition metal phosphates are abundant. If suitable phosphates can be found as negative electrodes for sodium ion batteries rather than for direct use of phosphorus, A low cost negative electrode for sodium ion battery is likely to be used. Through literature research and experimental investigation, the carbon coated nano-copper diphosphate material has been successfully synthesized in this paper. It was used as anode material for sodium ion batteries for the first time. The synthesized carbon coated nanophosphate Cu _ 2P _ 2 / C _ 2 / C material has excellent sodium storage performance. After 10 cycles of 150mA g ~ (-1) current charge / discharge cycle, The reversible sodium storage capacity is stable at 600.2mAh g-1, which is a potential negative electrode for low cost sodium ion batteries.
【学位授予单位】：华中科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TM912

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