活性石墨烯材料的制备及其电化学性能研究

发布时间：2018-06-15 11:27

本文选题：活性石墨烯 + 负极材料　；参考：《华中师范大学》2015年硕士论文

【摘要】：超级电容器和锂离子电池是理想的储能设备。电极材料是储能系统的关键,成为研究热点之一。石墨烯具有比表面积(SSA)大、导电性强和循环性能好等特点,在电极材料中具有明显优势。在本文中,我们用微波剥落氧化石墨(GO)的方法制备了石墨烯,这种石墨烯的SSA远低于理论值(2630m2/g)。然后用KOH活化,制得了不同SSA的活性石墨烯材料,并进行了电化学性能研究。主要内容如下:(1)以改进的Hummers法合成GO,然后用微波辐射GO制备出微波剥落GO(MEGO)。高温热还原质量比分别为5、6、7、8的KOH/MEGO混合物,制备了四种SSA依次增大的活性石墨烯材料(a-MEGO-x,x=1、2、3、4)。另外,在没有KOH存在条件下,制备出热还原MEGO材料(T-MEGO)。通过BET、XRD、FE-SEM、FT-IR测试对材料进行表征。结果表明,活性石墨烯的表面被不同程度地蚀刻成纳米小孔,对于SSA最大的活性石墨烯a-MEGO-4,比表面积高达3119.193 m2/g。(2)活性石墨烯作为超级电容器电极材料的研究表明:在扫速5 mV/s时,a-MEGO-1、2、3和4的比容量分别为131.3、159.6、204.5和217.3 F/g;扫速增大到200 mV/s时,比容量分别为111.3、137.5、170.5和184.2 F/g,容量保持率分别为84.8%、86.1%、83.4%和84.8%。对比试验中,MEGO在扫速为5 mV/s时比容量有199.0 F/g,但随着扫速的增大比容量迅速降低,在扫速为200 mV/s时比容量仅为97.7 F/g,容量保持率为49%。T-MEGO的比容量远小于MEGO。可见,活性石墨烯可以作为高性能超级电容器的电极材料。(3)活性石墨烯作为锂离子电池负极材料的研究表明:活性石墨烯的首次放电和充电比容量都随着SSA增大依次升高,而库伦效率随着SSA增大依次降低。对a-MEGO-4,其首次放电和充电比容量分别为4282.7和1603.4 mAh/g,首次库仑效率为37.4%。作为对比,MEGO的首次放电和充电比容量分别为2439.7和1235.7 mAh/g,库仑效率为50.6%。循环性能表明,a-MEGO的可逆比容量降低迅速。30次之后,a-MEGO-1、2、3和4的可逆比容量分别为485.5、590.5、580.7和709.6 mAh/g,容量保持率分别为44.7%、43.2%、40.2%和44.3%。相反,MEGO在循环30次后可逆比容量仍有916.8 mAh/g,容量保持率为74.2%。因此,活性石墨烯作为锂离子电池负极虽有较高的首次放电和充电比容量,但首次库仑效率及循环性能欠佳。
[Abstract]:Supercapacitors and lithium ion batteries are ideal energy storage equipment. Electrode material is the key of energy storage system and has become one of the research hotspots. Graphene has the advantages of large specific surface area (SSAs), strong conductivity and good cycling performance, and has obvious advantages in electrode materials. In this paper, graphene has been prepared by microwave stripping graphite oxide. The SSA of this graphene is much lower than the theoretical value of 2630m2 / g. Then the active graphene materials with different SSA were prepared by Koh activation and the electrochemical properties were studied. The main contents are as follows: (1) the improved Hummers method is used to synthesize goo, and then microwave spalling GOG MEGOA is prepared by microwave radiation go. Four kinds of active graphene materials with SSA increasing in turn were prepared by Koh / MEGO mixture with a mass ratio of 5 ~ 6 ~ 7 ~ 8 at high temperature respectively. In addition, in the absence of Koh, the thermal reduction MEGO material was prepared. The materials were characterized by BETX-XRDX-FE-SEM- FT-IR. The results show that the surface of active graphene is etched into nano-pores to varying degrees. For SSA's largest active graphene a-MEGO-4, with a specific surface area of 3119.193 m2 / g 路m2) as electrode material for supercapacitor, the specific capacities of a-MEGO-1 / 2GO-3 and 4 are 131.3159.6204.5 and 217.3 Fr / g at 5mV / s, respectively, when the sweep speed increases to 200mV / s, the specific capacity of a-MEGO-2GO-3 and 4 are 131.3159.6204.5 and 217.3 Fr / g, respectively, when the sweep speed increases to 200mV / s. The specific capacity was 111.3137.5170.5 and 184.2 F / g, and the capacity retention rate was 84.8% and 86.4%, 84.8% and 84.8%, respectively. In the contrast experiment, the specific capacity of MEGO is 199.0 F / g when the scanning speed is 5 MV / s, but the specific capacity decreases rapidly with the increase of scanning speed, and the specific capacity is only 97.7 F / g at the speed of 200mV / s, and the specific capacity of T-MEGO is much smaller than that of MEGO. It can be seen that active graphene can be used as electrode material for high performance supercapacitors.) active graphene can be used as anode material for lithium ion batteries. The results show that the initial discharge and charge specific capacity of active graphene increase with the increase of SSA. The Coulomb efficiency decreased with the increase of SSA. For a-MEGO-4, the first discharge and charge specific capacities are 4282.7 and 1603.4 mg 路h / g, respectively, and the first Coulomb efficiency is 37.4%. The first discharge and charge specific capacities of MEGO were 2439.7 and 1235.7 mg 路h / g, respectively, and the Coulomb efficiency was 50.6. The cycle performance showed that the reversible specific capacity of a-MEGO decreased rapidly. 30 times later, the reversible specific capacities of a-MEGO-1 and 4 were 485.5590.5580.7 and 709.6 mAh/ g, respectively, and the capacity retention rates were 44.7% 43.2% and 44.3%, respectively. On the contrary, the reversible specific capacity of MEGO was still 916.8 mg / g after 30 cycles, and the volume retention rate was 74.2%. Therefore, the first Coulomb efficiency and cycle performance of activated graphene as anode of Li-ion battery is poor, although it has high initial discharge and charge specific capacity.
【学位授予单位】：华中师范大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ127.11;TM53;TM912

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