新型锂-氧气电池双功能催化剂研究

发布时间：2018-01-05 00:31

本文关键词：新型锂-氧气电池双功能催化剂研究　出处：《中国科学院大学(中国科学院物理研究所)》2017年博士论文　论文类型：学位论文

【摘要】：与锂离子电池相比,锂-氧气电池具有更高的能量密度,因此近年来受到研究人员的广泛关注。在锂-氧气电池放电过程中,氧分子在正极表面被还原之后同Li~+生成LiOx化合物;而充电过程中,催化剂催化分解LiOx,析出氧气。正极材料需要同时对氧还原反应(ORR)和析氧反应(OER)有催化性能,因此如何从材料设计角度提高锂-氧气电池充放电效率、降低电池极化是目前锂-氧气电池研究的前沿方向。贵金属作为锂-氧气电池正极材料具有良好的性能,但成本较高,并且由于难于将其均匀地分散在碳材料等载体上等因素限制了其商业化进程。相比较而言,采用含有Co、Fe元素的催化剂作为锂-氧气电池正极材料,成本低廉易制备,比完全采用贵金属催化剂具有较大优势。本论文主要研究了含有Co、Fe元素的尖晶石和钙钛矿催化剂作为锂-氧气电池正极材料的性能。通过控制溶剂、温度以及时间等条件,利用水热的方法分别制备了呈现出{100}和{111}晶面的Co_3O_4立方块和八面体,通过测试锂-氧气电池性能,对比充放电极化电压、电池比容量以及循环稳定性,发现Co_3O_4八面体对锂-氧气电池性能提高比立方块更优。利用层状蒙脱石作为模板,在晶体结构层间浸入含有C、N元素的苯胺,在氮气气氛下碳化之后洗去蒙脱石,得到N掺杂的石墨烯。利用水热的方法制备了反尖晶石结构的Co[Co,Fe]O_4,该结构中Co、Fe元素同时占据尖晶石八面体位置。常温下采用物理方法将Co[Co,Fe]O_4负载到N掺杂的石墨烯上,得到Co[Co,Fe]O_4/N-G复合材料。将该种材料作为锂-氧气电池正极材料,测试电池首周比容量可达13312 mA h g-1,相比于Super P和商业Pt/C催化剂作为正极材料的锂-氧气电池,充电极化明显降低,经过110次以上循环之后性能无明显衰减。认为是一种优良的锂-氧气电池正极材料。利用静电纺丝的方法,制备出钙钛矿La_(0.6)Sr_(0.4)Co_(0.2）Fe_(0.8)O_3纳米纤维,并通过化学方法在其表面负载了7.4%(wt%)的RuO_2纳米颗粒。通过测试锂-氧气电池性能,发现RuO_2@LSCF-NFs作为正极催化剂的电池放电电压提高约120 mV,在2000 mA h g-1下的充电电压降低283 mV。在电流密度为100 mA g-1、截止容量为1000 mA h g-1下对两种材料组装的电池进行循环稳定性测试发现,70次循环之后,采用LSCF-NFs作为正极材料的锂-氧气电池性能出现明显下降,在充电比容量为500 mA h g-1下,极化电压增大了306 mV,而同样充电比容量下RuO_2@LSCF-NFs极化电压增大98 mV,表现出良好的充电性能。82次循环之后采用LSCF-NFs作为正极材料的锂-氧气电池放电电压低于2.0V,认为电池已经失效;而当RuO_2@LSCF-NFs作为电池正极材料时,锂-氧气电池循环120圈性能仍可保持相对稳定,表现出良好的循环稳定性。通过固相法合成制备了A位非化学计量比的钙钛矿氧化物Ba_(0.9)Co_(0.7)Fe_(0.2)Nb_(0.1)_O_3-δ。钙钛矿材料中A、B位置原子比低于1:1时会导致元素变价、氧空位浓度增大等变化。B_(0.9)CFN作为正极材料的锂-氧气电池放电比容量为12970 mA h g-1,放电电压平台在2.66 V左右;但充电电压较高。通过ALD的方法在Ba_(0.9)Co_(0.7)Fe_(0.2)Nb_(0.1)_O_3-δ颗粒表面负载IrO2纳米颗粒,改善了电池的性能。在6000 mA h g-1下电池的充电电压降低560 m V,表明IrO2对降低电池整体极化有明显的效果。对B_(0.9)CFN进行变温中子衍射分析,发现随着温度升高,材料呈现出收缩-扩张的“呼吸”特性,对提高高温下的ORR性能有较大的促进作用。通过测试350 h的EIS,显示B_(0.9)CFN经过长时间运行之后阻抗增加0.04Ωcm~2,是一种良好的高温ORR材料。
[Abstract]:Compared with the lithium ion battery, lithium oxygen battery has a higher energy density, so it received extensive attention in recent years. Researchers in lithium oxygen batteries during discharge, oxygen molecules to generate LiOx compounds after the cathode surface is reduced with Li~+; and the charging process, catalyst and catalytic decomposition of LiOx, oxygen precipitation. At the same time to cathode materials for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) catalytic performance, so how to improve the lithium oxygen battery efficiency from the angle of material design, reduce the cell polarization is a frontier research direction for lithium oxygen batteries. Precious metals as a cathode material lithium oxygen batteries with good performance, but the cost is higher, and due to be uniformly dispersed in carbon materials and other factors such as carrier has limited its commercialization process. In comparison, the catalyst containing Co, Fe elements as lithium electric oxygen Chi Zhengji material, low cost and easy preparation, has more advantages than the full use of precious metal catalysts. This paper mainly studies the containing Co, Fe elements of spinel and perovskite catalyst as a cathode material for lithium battery performance. By controlling the oxygen conditions of solvent, temperature and time, respectively showing {100} and {111} surface Co_3O_4 cube and eight surface were prepared by hydrothermal method, the performance test for lithium oxygen batteries, battery charging and discharging polarization voltage comparison, specific capacity and cycling stability, Co_3O_4 eight surface of lithium battery box to improve the performance of oxygen than better. Using layered montmorillonite as template, containing C in crystal structure the interlayer in aniline N element, after carbonization under nitrogen atmosphere from montmorillonite, graphene doped N. Anti spinel Co[Co prepared by hydrothermal method for the Fe]O_4. In the structure of Co, Fe elements simultaneously occupy eight positions. The spinel at room temperature by physical methods Co[Co, Fe]O_4 load to graphene doped N, Co[Co, Fe]O_4/N-G. This kind of composite material as cathode materials for lithium oxygen batteries, testing battery capacity of up to 13312 mA than the first week of H g-1, compared to Super P and commercial Pt/C catalyst as a cathode material for lithium oxygen batteries, charging polarization decreased significantly after 110 cycles without obvious performance degradation. That is an excellent oxygen lithium battery cathode material. Using electrospinning method, preparation of perovskite La_ (0.6) Sr_ (0.4) Co_ (0.2) Fe_ (0.8) O_3 nanofibers, and by chemical methods on the surface load of 7.4% (wt%) RuO_2 nano particles. By the test for lithium oxygen battery, discovered that RuO_2@LSCF-NFs acts as a battery discharge voltage anode catalyst is improved by about 120 mV, The charging voltage at 2000 mA h under g-1 reduction of 283 mV. at a current density of 100 mA g-1, by the capacity of the two materials assembled 1000 mA h under the g-1 cell cycle stability tests showed that, after 70 cycles, using LSCF-NFs as cathode material for lithium oxygen battery performance is decreased, in charge specific capacity of 500 mA h g-1, polarization voltage is increased by 306 mV, while the same charge ratio RuO_2@LSCF-NFs polarization voltage capacity increased by 98 mV, showing good charging performance after.82 cycles using LSCF-NFs as cathode material for lithium oxygen batteries discharge voltage is lower than 2.0V, that the battery has been failure; and when the battery RuO_2@LSCF-NFs cathode material, lithium battery oxygen 120 cycles performance still remain relatively stable, showing good cycling stability. Through the synthesis of solid phase method preparation of perovskite A non stoichiometric ratio The oxide Ba_ (0.9) Co_ (0.7) Fe_ (0.2) Nb_ (0.1) _O_3- 8. In perovskite A, B atomic ratio less than 1:1 will cause the element valence oxygen vacancy concentration increases, changes in.B_ (0.9) CFN as cathode material for lithium oxygen batteries discharge capacity of 12970 mA h g-1, discharge voltage is about 2.66 V; but the charging voltage is higher. By the method of ALD in Ba_ (0.9) Co_ (0.7) Fe_ (0.2) Nb_ (0.1) _O_3- delta particle surface loaded IrO2 nanoparticles, to improve the performance of the battery. A reduction of 560 m V 6000 mA h g-1 in the charging voltage of batteries, show that IrO2 has obvious effect on reducing overall cell polarization. The B_ (0.9) CFN neutron diffraction analysis of temperature, with increasing temperature, the material showing a contraction expansion "breathing" characteristics, to improve the performance of ORR high temperature have a greater role in promoting. Through the test of 350 H EIS, B_ (0.9) CFN after a long time. After the line, the impedance increased by 0.04 Omega cm~2, which is a good high temperature ORR material.

【学位授予单位】：中国科学院大学(中国科学院物理研究所)
【学位级别】：博士
【学位授予年份】：2017
【分类号】：O643.36;TM911.41

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