碳材料结构与官能化调控及其应用于锂硫电地和超级电容器的研究
发布时间：2018-07-25 21:23
【摘要】：随着全世界化石资源日渐减少,环境污染问题日益加重,如今,开发可持续清洁能源以及先进的能量储存技术是人类面临的巨大挑战。目前,锂硫电池成为高能量密度电化学储能体系的研究热点,而超级电容器成为高功率密度电化学储能体系的研究热点。锂硫电池和超级电容器中都用到碳材料,碳材料作为锂硫电池单质硫的导电基底材料和超级电容器电极材料,由于其具有导电性高、机械性能优良、可调孔结构、较大比表面积、价格低廉等优点,是迄今为止最理想和应用最广泛的储能材料之一。在超级电容器和锂硫电池中使用的碳材料包括介孔碳、碳纳米管、碳纤维、石墨烯等。本文从实用角度出发,利用简单易于重复的制备方法,合成了一种无序介孔碳,一种掺硼无序介孔碳和一种具有微孔和介孔的无序碳材料,将其作为锂硫电池正极活性硫的负载基底材料,制备碳/硫复合正极材料,进行了电化学性能测试和表征。另外,以商品掺氮石墨烯为原料,通过进一步高温还原处理得到热稳定的掺氮石墨烯材料,将其作为超级电容器电极材料,进行了电化学性能测试。在两方面工作中探讨了碳材料的官能团对材料电化学性能的影响。主要研究内容如下:1、以酚醛树脂预聚体为碳源,以正硅酸乙酯为扩孔剂,制备了具有双孔径、结构稳定、易于重复的无序介孔碳DMC,并将此无序介孔碳用于锂硫电池正极材料中,利用熔融法,制备了不同含硫量的碳/硫复合材料,考察了碳/硫复合材料的结构和电化学性能,探讨了无序介孔中载硫量的大小对其电化学性能的影响。实验结果表明:以无序介孔碳DMC为载硫基底材料,通过简单的热熔法,当单质硫负载量少(66.7wt%)时,硫能以较小的纳米尺寸进入到介孔碳的孔道内高度分散,当单质硫负载量大(75wt%)时,有少量硫附着在碳材料表面;碳/硫复合材料中介孔碳内部存在的微量O原子对单质硫具有一定的化学吸附作用;在碳/硫复合材料中随着硫含量的增加,硫电极的放电比容量与活性物质利用率下降;对于含硫量为66.7 wt%的复合材料,在1C倍率下容量保持率较高,库仑效率接近100%,表明该复合材料中碳负载基底结构稳定,机械强度大,对电流密度的变化具有良好的应变能力,该材料用于实际锂硫电池将具有非常重要的意义。2、以硼酸为硼源,以正硅酸乙酯为扩孔剂,制备了掺硼无序介孔碳BDMC,并将此介孔碳与单质硫按一定质量比经热融法制备掺硼介孔碳/硫复合材料。考察了掺硼介孔碳/硫复合材料的结构和电化学性能,比较了掺硼介孔碳/硫复合材料与没掺硼介孔碳/硫复合材料的电化学性能的优劣。实验通过XPS,RS测试手段确定了BDMC材料中存在少量的B原子;掺硼BDMC材料与未掺硼DMC材料相比,孔结构、比表面积、孔容没有太大差别;XPS测试表明,掺硼复合材料中的B原子产生了轻微的正极化现象,从而使掺硼复合材料在碳硫界面上对硫具有更大的吸附作用力,在充放电过程中能够对多硫化物阴离子产生化学吸附作用,抑制其溶解于电解液,因此掺硼碳/硫复合材料在不同放电倍率下的电化学性能优于未掺硼碳/硫复合材料。3、以酚醛树脂预聚体为碳源,以KOH和Zn Cl2为联合扩孔剂,制备了具有更大比表面积和孔容,且具有微孔/介孔的无序碳MC,将此无序微孔/介孔碳材料用于锂硫电池正极材料中,利用熔融法制备碳/硫(MC:S=1:2)复合材料,电化学测试表明:MC:S=1:2复合材料的比容量和循环性能明显高与DMC:S=1:2复合材料,分析其中的原因是由于MC碳材料具有微孔/介孔结构和更大的比表面积和孔容,其中的微孔能有效抑制多硫化物的溶解,较大的孔容与比表面积能对活性物质硫和充放电过程中产生的多硫化物产生更强的吸附作用,同时能缓解硫正极在充放电过程中体积膨胀的问题。另外,在此MC:S=1:2复合材料表面包覆一层导电PANI后,能进一步提高电池的比容量和活性物质硫的利用率。4、以购买的商品还原石墨烯C-r GO为原料,使用氮氢混合气为还原剂,在不同温度下进一步还原处理C-r GO,得到了不同温度热处理后的热稳定还原石墨烯TS-r GO,并将此类热稳定石墨烯材料作为超级电容器电极材料,通过电化学测试对比了原料石墨烯和不同温度制备的热稳定石墨烯材料的电化学性能的优劣,分析并探讨了其中存在的原因。实验结果表明:不同热处理温度对氮掺杂的商品石墨烯C-r GO材料的微观形貌,晶格结构影响不大,TS-r GO材料仍然是含氮的石墨烯材料;随热处理温度的升高,石墨烯材料中的N,O官能团分解,造成石墨层间距的减小,温度超过800℃,部分石墨烯片的尺寸有所增大;尽管随热处理温度的升高,得到的TS-r GO材料的比电容,比能量和比功率随着温度的升高而下降,但其在高倍率下循环性能表现良好;商品C-r GO作为超极电容器电极材料循环性能较差,在前1000次循环过程中容量保持率下降严重(下降了10.1%),而不同温度热处理得到的TS-r GO材料表现出较好的高倍率循环稳定性,尤其是TS-r GO(700)材料的容量保持率,在前1000次循环中只下降了0.3%,在10000次循环后容量保持率仍有97.2%。实验发现TS-r GO材料中被优化的氮原子的官能团,有助于改善其循环寿命,降低泄漏电流密度,材料高倍率电容性能的增加可以归因于其电导率的增加。
[Abstract]:With the decrease of fossil resources in the world and the increasing pollution of the environment, the development of sustainable clean energy and advanced energy storage technology is a great challenge for mankind. Currently, lithium sulfur batteries have become a hot spot in high energy density electrochemical energy storage system, and supercapacitors become high power density electrochemical storage. Carbon materials are used in both lithium sulfur batteries and supercapacitors. Carbon materials are used as conductive base materials and supercapacitor electrode materials for the single sulfur of lithium sulfur batteries. Because of their high conductivity, good mechanical properties, adjustable pore structure, large surface product and low price, it is the most ideal and should be done so far. Carbon materials used in supercapacitors and lithium sulfur batteries include mesoporous carbon, carbon nanotubes, carbon fibers and graphene, which are one of the most widely used energy storage materials. From a practical point of view, a disordered mesoporous carbon, a boron doped mesoporous carbon, and a porous mesoporous and mesoporous material are synthesized from a practical point of view. The carbon / sulfur composite positive material was prepared by the disordered carbon material, which was used as the base material of the active sulfur of the lithium sulfur battery. The electrochemical performance was tested and characterized. In addition, the thermally stable nitrogen doped graphene material was obtained by further high temperature reduction by the further high temperature reduction of graphene, and it was used as the electrode material of the supercapacitor. The effects of the functional groups of carbon materials on the electrochemical properties of the materials are discussed in two aspects. The main contents are as follows: 1, with the phenol formaldehyde resin prepolymer as the carbon source and the ethyl orthosilicate as the reaming agent, the disordered mesoporous carbon DMC with a double hole diameter, stable structure and easy repetition is prepared, and this disorder will be disordered. Carbon / sulfur composite materials with different sulfur content were prepared by melting method in the cathode materials of lithium sulfur battery. The structure and electrochemical properties of carbon / sulfur composites were investigated. The effects of sulfur loading on the electrochemical properties of the disordered mesoporous materials were investigated. The experimental results showed that the disordered mesoporous carbon DMC was used as the base material for the sulfur carrier. By a simple heat melting method, when the load of elemental sulfur is less (66.7wt%), sulfur can be highly dispersed into the pore of mesoporous carbon in a small nanometer size. When the amount of sulfur is large (75wt%), a small amount of sulfur is attached to the surface of the carbon material. The trace O atoms of the carbon / sulfur composite material have a certain chemistry on the elemental sulfur. With the increase of sulfur content in carbon / sulfur composites, the discharge ratio of the sulfur electrode and the utilization ratio of the active substance decrease. For the composite with 66.7 wt% sulfur content, the capacity of the composite material is high and the coulomb efficiency is close to 100% at the rate of 1C, indicating that the carbon loaded substrate in the composite is stable, the mechanical strength is large, and the current is high. The density change has good strain ability. The material used in the actual lithium sulfur battery will have a very important significance.2. Using boric acid as the boron source and the ethyl orthosilicate as the reamer, the boron doped disordered mesoporous carbon BDMC is prepared, and the boron doped mesoporous carbon / sulfur composites are prepared by the heat thawing method of the mesoporous carbon and the elemental sulfur by the heat thawing method. The structure and electrochemical properties of boron doped mesoporous carbon / sulfur composites are compared. The electrochemical properties of boron doped mesoporous carbon / sulfur composites and boron doped mesoporous carbon / sulfur composites are compared. A small amount of B atoms exist in the BDMC material by XPS and RS testing. The pore structure of boron doped BDMC material is compared with the non boron doped DMC material. The surface area, Kong Rong is not very different. The XPS test shows that the B atom in the boron doped composite produces a slight positive polarization, which makes the boron doped composite have a greater adsorption force on the sulfur at the carbon and sulfur interface, and can produce a chemical adsorption on the polysulfide anion in the charge discharge process, and inhibit its dissolution in electrolysis. Therefore, the electrochemical performance of boron doped carbon / sulfur composites at different discharge rates is better than that of.3 without boron doped carbon / sulfur composite material, with phenolic resin prepolymer as carbon source and KOH and Zn Cl2 as joint reamers, a disordered carbon MC with larger specific surface area and Kong Rong and microporous / mesoporous carbon is prepared, and the disordered microporous / mesoporous carbon material is used. Carbon / sulfur (MC:S=1:2) composites were prepared by melting method in the cathode materials of lithium sulphur battery. The electrochemical test showed that the specific capacity and cyclic properties of MC:S=1:2 composites were significantly higher than that of DMC:S=1:2 composites. The reason for the analysis was that the MC carbon material had microporous / mesoporous structure and larger specific surface area and Kong Rong, in which the microstructure of the composites was micro. The pore capacity can effectively inhibit the dissolution of polysulfide. The larger pore volume and specific surface area can have a stronger adsorption effect on the sulfur and the polysulfide produced during the charge discharge process. At the same time, it can alleviate the volume expansion of the sulfur positive pole during the charge discharge process. In addition, after coating the surface of the MC:S=1:2 composite surface with a conductive PANI, it can be entered. In one step, the specific capacity of the battery and the utilization ratio of the active substance sulfur are improved.4, and the purchased commodity reduction graphene C-r GO is used as the raw material, and the hydrogen mixture of nitrogen and hydrogen is used as the reducing agent to further reduce the C-r GO at different temperatures. The thermal stabilized reductive stonene TS-r GO after the heat treatment at different temperatures is obtained, and this kind of thermally stabilized graphene is used as the material. For supercapacitor electrode materials, the electrochemical properties of graphene and thermally stabilized graphene materials prepared at different temperatures are compared by electrochemical tests. The reasons are analyzed and discussed. The experimental results show that the microstructure of the C-r GO materials with different heat treatment temperatures on the nitrogen doped graphene is the lattice junction. The structure of the TS-r GO material is still a nitrogen containing graphene material. With the increase of heat treatment temperature, the N and O functional groups in the graphene materials are decomposed, resulting in the decrease of the spacing of the graphite layer, the temperature is over 800 degrees C, and the size of some graphene sheets increases. Although the heat treatment temperature increases, the specific capacitance and the specific energy of the obtained TS-r GO material are more than the energy. And the specific power decreases with the increase of temperature, but its performance is good at high rate, and the circulation performance of C-r GO as the electrode material of supercapacitor is poor, and the capacity retention rate in the first 1000 cycles decreases seriously (10.1%), and the TS-r GO material obtained by different temperature heat treatment shows a better high ratio. The cyclic stability, especially the capacity retention of TS-r GO (700) material, only decreased by 0.3% in the first 1000 cycles. After the 10000 cycle, the capacity retention rate still has the 97.2%. experiment to find the optimized nitrogen atom group in the TS-r GO material, which helps to improve its cycle life, reduce the leakage current density, and increase the high rate capacitance of the material. Addition can be attributed to an increase in its electrical conductivity.
【学位授予单位】：东北师范大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TQ127.11;O646
[Abstract]:With the decrease of fossil resources in the world and the increasing pollution of the environment, the development of sustainable clean energy and advanced energy storage technology is a great challenge for mankind. Currently, lithium sulfur batteries have become a hot spot in high energy density electrochemical energy storage system, and supercapacitors become high power density electrochemical storage. Carbon materials are used in both lithium sulfur batteries and supercapacitors. Carbon materials are used as conductive base materials and supercapacitor electrode materials for the single sulfur of lithium sulfur batteries. Because of their high conductivity, good mechanical properties, adjustable pore structure, large surface product and low price, it is the most ideal and should be done so far. Carbon materials used in supercapacitors and lithium sulfur batteries include mesoporous carbon, carbon nanotubes, carbon fibers and graphene, which are one of the most widely used energy storage materials. From a practical point of view, a disordered mesoporous carbon, a boron doped mesoporous carbon, and a porous mesoporous and mesoporous material are synthesized from a practical point of view. The carbon / sulfur composite positive material was prepared by the disordered carbon material, which was used as the base material of the active sulfur of the lithium sulfur battery. The electrochemical performance was tested and characterized. In addition, the thermally stable nitrogen doped graphene material was obtained by further high temperature reduction by the further high temperature reduction of graphene, and it was used as the electrode material of the supercapacitor. The effects of the functional groups of carbon materials on the electrochemical properties of the materials are discussed in two aspects. The main contents are as follows: 1, with the phenol formaldehyde resin prepolymer as the carbon source and the ethyl orthosilicate as the reaming agent, the disordered mesoporous carbon DMC with a double hole diameter, stable structure and easy repetition is prepared, and this disorder will be disordered. Carbon / sulfur composite materials with different sulfur content were prepared by melting method in the cathode materials of lithium sulfur battery. The structure and electrochemical properties of carbon / sulfur composites were investigated. The effects of sulfur loading on the electrochemical properties of the disordered mesoporous materials were investigated. The experimental results showed that the disordered mesoporous carbon DMC was used as the base material for the sulfur carrier. By a simple heat melting method, when the load of elemental sulfur is less (66.7wt%), sulfur can be highly dispersed into the pore of mesoporous carbon in a small nanometer size. When the amount of sulfur is large (75wt%), a small amount of sulfur is attached to the surface of the carbon material. The trace O atoms of the carbon / sulfur composite material have a certain chemistry on the elemental sulfur. With the increase of sulfur content in carbon / sulfur composites, the discharge ratio of the sulfur electrode and the utilization ratio of the active substance decrease. For the composite with 66.7 wt% sulfur content, the capacity of the composite material is high and the coulomb efficiency is close to 100% at the rate of 1C, indicating that the carbon loaded substrate in the composite is stable, the mechanical strength is large, and the current is high. The density change has good strain ability. The material used in the actual lithium sulfur battery will have a very important significance.2. Using boric acid as the boron source and the ethyl orthosilicate as the reamer, the boron doped disordered mesoporous carbon BDMC is prepared, and the boron doped mesoporous carbon / sulfur composites are prepared by the heat thawing method of the mesoporous carbon and the elemental sulfur by the heat thawing method. The structure and electrochemical properties of boron doped mesoporous carbon / sulfur composites are compared. The electrochemical properties of boron doped mesoporous carbon / sulfur composites and boron doped mesoporous carbon / sulfur composites are compared. A small amount of B atoms exist in the BDMC material by XPS and RS testing. The pore structure of boron doped BDMC material is compared with the non boron doped DMC material. The surface area, Kong Rong is not very different. The XPS test shows that the B atom in the boron doped composite produces a slight positive polarization, which makes the boron doped composite have a greater adsorption force on the sulfur at the carbon and sulfur interface, and can produce a chemical adsorption on the polysulfide anion in the charge discharge process, and inhibit its dissolution in electrolysis. Therefore, the electrochemical performance of boron doped carbon / sulfur composites at different discharge rates is better than that of.3 without boron doped carbon / sulfur composite material, with phenolic resin prepolymer as carbon source and KOH and Zn Cl2 as joint reamers, a disordered carbon MC with larger specific surface area and Kong Rong and microporous / mesoporous carbon is prepared, and the disordered microporous / mesoporous carbon material is used. Carbon / sulfur (MC:S=1:2) composites were prepared by melting method in the cathode materials of lithium sulphur battery. The electrochemical test showed that the specific capacity and cyclic properties of MC:S=1:2 composites were significantly higher than that of DMC:S=1:2 composites. The reason for the analysis was that the MC carbon material had microporous / mesoporous structure and larger specific surface area and Kong Rong, in which the microstructure of the composites was micro. The pore capacity can effectively inhibit the dissolution of polysulfide. The larger pore volume and specific surface area can have a stronger adsorption effect on the sulfur and the polysulfide produced during the charge discharge process. At the same time, it can alleviate the volume expansion of the sulfur positive pole during the charge discharge process. In addition, after coating the surface of the MC:S=1:2 composite surface with a conductive PANI, it can be entered. In one step, the specific capacity of the battery and the utilization ratio of the active substance sulfur are improved.4, and the purchased commodity reduction graphene C-r GO is used as the raw material, and the hydrogen mixture of nitrogen and hydrogen is used as the reducing agent to further reduce the C-r GO at different temperatures. The thermal stabilized reductive stonene TS-r GO after the heat treatment at different temperatures is obtained, and this kind of thermally stabilized graphene is used as the material. For supercapacitor electrode materials, the electrochemical properties of graphene and thermally stabilized graphene materials prepared at different temperatures are compared by electrochemical tests. The reasons are analyzed and discussed. The experimental results show that the microstructure of the C-r GO materials with different heat treatment temperatures on the nitrogen doped graphene is the lattice junction. The structure of the TS-r GO material is still a nitrogen containing graphene material. With the increase of heat treatment temperature, the N and O functional groups in the graphene materials are decomposed, resulting in the decrease of the spacing of the graphite layer, the temperature is over 800 degrees C, and the size of some graphene sheets increases. Although the heat treatment temperature increases, the specific capacitance and the specific energy of the obtained TS-r GO material are more than the energy. And the specific power decreases with the increase of temperature, but its performance is good at high rate, and the circulation performance of C-r GO as the electrode material of supercapacitor is poor, and the capacity retention rate in the first 1000 cycles decreases seriously (10.1%), and the TS-r GO material obtained by different temperature heat treatment shows a better high ratio. The cyclic stability, especially the capacity retention of TS-r GO (700) material, only decreased by 0.3% in the first 1000 cycles. After the 10000 cycle, the capacity retention rate still has the 97.2%. experiment to find the optimized nitrogen atom group in the TS-r GO material, which helps to improve its cycle life, reduce the leakage current density, and increase the high rate capacitance of the material. Addition can be attributed to an increase in its electrical conductivity.
【学位授予单位】：东北师范大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TQ127.11;O646
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