高容量电极材料的制备及其电化学性能研究
发布时间：2018-09-03 06:09
【摘要】：锂离子电池和超级电容器是储能的两个重要方向,它们的电化学性能和能量密度决定着它们今后的道路。然而,目前的储能电极材料一方面在具有高容量的同时,它的电化学循环和倍率容量性能却很差,需要进行改性处理；另一方面电极材料的电化学性能和储能容量和它的形貌有着密切的关系,实现电极材料的形貌最优化制备对提升电极材料电化学性能和能量密度有着重要意义。 1.金属氧化物的理论储锂容量比较高,是石墨的2-3倍,但是它的循环性能却很差,需要进行改性处理。可充电锂离子二次电池的电化学性能主要和脱嵌锂电极中Li的固相扩散动力问题以及材料表面特性相关。我们以油酸为碳源,发明了一种新颖的制备氧化镍／碳复合纳米片的技术,这种以油酸为碳源,氧化镍纳米片为前驱体制备的NiO@C复合材料在50次循环后仍然展现出883mAh g-1的可逆容量,大大改善了NiO在充放电过程中的循环衰减问题和倍率问题,制备了一种高能量密度且循环性能优异的锂电负极材料,并在实验中比较了两种不同碳包覆效果对材料的影响,对碳包覆表面改性处理方式的差异提供了重要依据。 2.我们研究了羟磷铁锂结构LiFe(PO4)(OH)xF1-x分层微球的形貌-变量的电化学性能,包括壳结构和中空结构的创建。实验结果表明材料的电化学性能会随着其形貌的改变而明显变化。与其它颗粒相比,由纳米棒和多孔微球组成的羟磷铁锂微球表现出优异的电化学性能,这可以归因于锂离子扩散途径被缩短,材料比表面积增大。据我们所知,这是第一次就形貌对可很好定义结构的羟磷铁锂电极材料的电化学活性的影响进行系统的研究。这种易于实现的合成不同形貌羟磷铁锂材料的方法能为进一步研究羟磷铁锂结构LiFe(PO4)(OH)xF1-x形状-变量材料的电化学性能研究提供一个有趣的平台。 3.硅是自然界储锂容量最高的,但同时它的循环性能很差。我们从材料结构设计入手,合成了一种柔性外壳包裹弹性内核的核壳结构的石墨烯包裹单颗粒硅纳米结构。通过对纳米硅进行化学修饰,实现纳米硅与氧化石墨烯的自组装,然后采用环保的维生素C(抗坏血酸)在微波辅助下还原氧化石墨烯,形成石墨烯包裹单颗粒纳米硅复合材料。利用石墨烯的高比表面积、良好导电性和多孔结构来抑制硅在脱嵌锂过程中的体积膨胀,提高其电化学性能。通过对它的电化学性能研究和与纯硅性能的对比验证了石墨烯的包覆能有效改善硅的循环性能和倍率性能,为制备高能量密度硅基材料提供了思路。 4.为了进一步验证材料的颗粒大小和形貌对储能材料电化学性能的影响,我们利用简单的静电纺丝后空气退火的方法制备出一维(1D)多孔ZnCo2O4纳米管(PNTs)并首次应用于超级电容器(SCs),并与ZnCo2O4纳米颗粒的超电容性能做了系统的对比研究,实验证明这种一维多孔ZnCo2O4纳米管的比容量、循环性能以及倍率性能等明显优于ZnCo2O4纳米颗粒。我们的一系列实验证明通过改变材料的形貌确实可以实现优化电化学性能的目的。
[Abstract]:Lithium-ion batteries and supercapacitors are two important directions of energy storage, and their electrochemical properties and energy density determine their future. However, the current energy storage electrode materials have poor electrochemical cycling and rate capacity performance while they have high capacity, so they need to be modified. The electrochemical properties and energy storage capacity of electrode materials are closely related to their morphologies. It is important to optimize the morphology of electrode materials for improving the electrochemical properties and energy density of electrode materials.
1. The theoretical lithium storage capacity of metal oxides is 2-3 times higher than that of graphite, but its cycling performance is very poor and needs modification. The electrochemical performance of rechargeable lithium-ion secondary batteries is mainly related to the solid-phase diffusion dynamics of Li in the de-intercalated lithium electrode and the surface characteristics of materials. A novel technique for preparing nickel oxide/carbon composite nanosheets was developed. The NiO@C composite prepared with oleic acid as carbon source and nickel oxide nanosheet as precursor still exhibited 883 mAh g-1 reversible capacity after 50 cycles. The cyclic attenuation and rate of NiO during charge-discharge process were greatly improved and a high energy NiO@C composite was prepared. The lithium anode materials with high density and excellent cycling performance were compared in the experiment. The influence of two different carbon coating effects on the materials was also compared.
2. The morphology-variable electrochemical properties of LiFe (PO4) (OH) xF1-x layered microspheres were investigated, including the creation of shell and hollow structures. The experimental results show that the electrochemical properties of the microspheres vary significantly with the morphology of the microspheres. Compared with other particles, lithium hydroxyphosphate consisting of nanorods and porous microspheres is slight. The excellent electrochemical properties of the spheres can be attributed to the shortening of the lithium ion diffusion pathway and the increase of the specific surface area of the materials. The method of lithium materials can provide an interesting platform for further study of the electrochemical properties of LiFe(PO4)(OH)xF1-x shape-variable materials.
3. Silicon has the highest lithium storage capacity in nature, but its cycling performance is very poor. Starting from the material structure design, we synthesized a graphene-encapsulated single-particle silicon nanostructure with flexible shell and elastic core. The self-assembly of nano-silicon and graphene oxide was realized by chemical modification of nano-silicon. Graphene-coated single-particle silicon nanocomposites were prepared by microwave-assisted reduction of graphene oxide with environmentally friendly vitamin C (ascorbic acid). High specific surface area, good conductivity and porous structure of graphene were used to restrain the volume expansion of silicon in the process of lithium deintercalation and improve its electrochemical properties. The comparison between graphene and pure silicon shows that graphene coating can effectively improve the cycling performance and ratio performance of silicon, which provides a new idea for preparing high energy density silicon-based materials.
4. In order to further verify the effect of particle size and morphology on the electrochemical properties of energy storage materials, we fabricated one-dimensional (1D) porous ZnCo2O4 nanotubes (PNTs) by simple electrospinning and air annealing method and applied them to supercapacitors (SCs) for the first time. The supercapacitor properties of the materials were systematically compared with those of ZnCo2O4 nanoparticles. The experimental results show that the specific capacity, cycling performance and rate performance of the one-dimensional porous ZnCo2O4 nanotubes are superior to those of ZnCo2O4 nanoparticles.
【学位授予单位】：湖南大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TM912
本文编号：2219094
[Abstract]:Lithium-ion batteries and supercapacitors are two important directions of energy storage, and their electrochemical properties and energy density determine their future. However, the current energy storage electrode materials have poor electrochemical cycling and rate capacity performance while they have high capacity, so they need to be modified. The electrochemical properties and energy storage capacity of electrode materials are closely related to their morphologies. It is important to optimize the morphology of electrode materials for improving the electrochemical properties and energy density of electrode materials.
1. The theoretical lithium storage capacity of metal oxides is 2-3 times higher than that of graphite, but its cycling performance is very poor and needs modification. The electrochemical performance of rechargeable lithium-ion secondary batteries is mainly related to the solid-phase diffusion dynamics of Li in the de-intercalated lithium electrode and the surface characteristics of materials. A novel technique for preparing nickel oxide/carbon composite nanosheets was developed. The NiO@C composite prepared with oleic acid as carbon source and nickel oxide nanosheet as precursor still exhibited 883 mAh g-1 reversible capacity after 50 cycles. The cyclic attenuation and rate of NiO during charge-discharge process were greatly improved and a high energy NiO@C composite was prepared. The lithium anode materials with high density and excellent cycling performance were compared in the experiment. The influence of two different carbon coating effects on the materials was also compared.
2. The morphology-variable electrochemical properties of LiFe (PO4) (OH) xF1-x layered microspheres were investigated, including the creation of shell and hollow structures. The experimental results show that the electrochemical properties of the microspheres vary significantly with the morphology of the microspheres. Compared with other particles, lithium hydroxyphosphate consisting of nanorods and porous microspheres is slight. The excellent electrochemical properties of the spheres can be attributed to the shortening of the lithium ion diffusion pathway and the increase of the specific surface area of the materials. The method of lithium materials can provide an interesting platform for further study of the electrochemical properties of LiFe(PO4)(OH)xF1-x shape-variable materials.
3. Silicon has the highest lithium storage capacity in nature, but its cycling performance is very poor. Starting from the material structure design, we synthesized a graphene-encapsulated single-particle silicon nanostructure with flexible shell and elastic core. The self-assembly of nano-silicon and graphene oxide was realized by chemical modification of nano-silicon. Graphene-coated single-particle silicon nanocomposites were prepared by microwave-assisted reduction of graphene oxide with environmentally friendly vitamin C (ascorbic acid). High specific surface area, good conductivity and porous structure of graphene were used to restrain the volume expansion of silicon in the process of lithium deintercalation and improve its electrochemical properties. The comparison between graphene and pure silicon shows that graphene coating can effectively improve the cycling performance and ratio performance of silicon, which provides a new idea for preparing high energy density silicon-based materials.
4. In order to further verify the effect of particle size and morphology on the electrochemical properties of energy storage materials, we fabricated one-dimensional (1D) porous ZnCo2O4 nanotubes (PNTs) by simple electrospinning and air annealing method and applied them to supercapacitors (SCs) for the first time. The supercapacitor properties of the materials were systematically compared with those of ZnCo2O4 nanoparticles. The experimental results show that the specific capacity, cycling performance and rate performance of the one-dimensional porous ZnCo2O4 nanotubes are superior to those of ZnCo2O4 nanoparticles.
【学位授予单位】：湖南大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TM912
【参考文献】
相关期刊论文 前3条
1 徐仲榆,郑洪河;锂离子蓄电池碳负极/电解液的相容性研究进展Ⅱ电解液组成与碳负极/电解液的相容性[J];电源技术;2000年05期
2 赖琼钰,卢集政,邹宏如;摇椅锂离子二次电池及其嵌入式电极材料[J];化学研究与应用;1998年01期
3 杜霞;薛卫东;赵睿;陈野川;;石墨烯/硅负极材料的制备及其电化学性能的研究[J];化工科技;2013年05期
，本文编号：2219094
本文链接：https://www.wllwen.com/kejilunwen/dianlilw/2219094.html
