锰系尖晶石金属氧化物的水热制备与电化学性能研究
发布时间：2018-08-02 18:49
【摘要】：锂离子电池作为绿色二次电池已经广泛的应用到了人们的日常生活中。目前已商业化生产的石墨负极由于其理论比容量(372 mAh/g)较低,已不能满足其在储能领域中的应用。具有高理论比容量(600-1000 m Ah/g)的过渡金属氧化物尤其是锰系尖晶石金属氧化物,其结构稳定、来源广泛、成本低廉、且对环境友好而成为锂离子电池负极材料的研究热点。但其在充放电过程中容易发生体积变化导致电极材料结构的崩塌且导电性较差,限制了其应用。本文通过将锰系尖晶石型过渡金属氧化物负载在石墨烯片层上缓解金属氧化物体积变化应力的同时提高其导电性。本文的主要研究内容如下:采用改进的Hummers法制备氧化石墨烯。以CoCl2·6H2O和MnCl2·4H2O为金属源,水为溶剂,氨水为沉淀剂,采用成本低廉的原材料以及简单温和的一步水热法合成尖晶石(Co,Mn)(Co,Mn)2O4/RGO纳米复合材料。与单纯的金属氧化物相比,此纳米复合材料具有更均匀的颗粒形貌以及更优异的电化学性能。通过控制水热反应时间来研究其对纳米复合材料的形貌结构以及电化学性能的影响。水热反应时间为8 h的尖晶石(Co,Mn)(Co,Mn)2O4/RGO纳米复合物具有最合适的粒径以及最优异的电化学性能。颗粒粒径在50 nm左右,首次放电容量为1486.9 mAh/g,首次库伦效率为73.7%,50次充放电循环后容量为743 mAh/g。以Zn(Ac)2·4H2O和Mn(Ac)2·4H2O为金属源,采用简单的一步水热法合成尖晶石ZnMn2O4/RGO纳米复合材料。与单纯的ZnMn2O4纳米颗粒相比,ZnMn2O4/RGO纳米复合材料具有更均匀的颗粒形貌以及更优异的电化学性能。通过控制水热反应时间来研究其对纳米复合材料的形貌结构以及电化学性能的影响。水热反应时间为10 h的得到的ZnMn2O4/RGO纳米复合材料综合性能最佳。其中金属氧化物颗粒尺寸均匀,颗粒粒径约为30 nm,在100 mA/g的电流密度下,首次放电容量为1279.7 mAh/g,循环50圈后比容量为796.9 mAh/g,相比于第二次放电比容量,容量保持率高达96.07%。本文通过简单的一步水热法,不需要高温烧结就能实现高结晶度的尖晶石纳米金属氧化物附着在还原的氧化石墨烯片层上。通过控制金属元素的种类可以控制颗粒的尺寸、充放电平台,为获得成本低、制备工艺简单且高比容量的锂离子电池负极材料提供了新的思路。
[Abstract]:As a green secondary battery, lithium ion battery has been widely used in people's daily life. Because of its low theoretical specific capacity (372 mAh/g), the graphite anode produced commercially can not satisfy its application in the field of energy storage. Transition metal oxides with high theoretical specific capacity (600-1000m Ah/g), especially manganese spinel metal oxides, are of stable structure, wide source, low cost and friendly to the environment. However, it is easy to change the volume during charge and discharge, which leads to the collapse of electrode structure and poor electrical conductivity, which limits its application. In this paper, manganese spinel type transition metal oxides were loaded on graphene lamellae to relieve the stress of metal oxide volume change and to improve its electrical conductivity. The main contents of this paper are as follows: the improved Hummers method is used to prepare graphene oxide. Using CoCl2 6H2O and MnCl2 4H2O as metal source, water as solvent and ammonia as precipitant, spinel (Coomn) 2O4/RGO nanocomposites were synthesized by simple and mild one step hydrothermal method with low cost raw materials. Compared with the pure metal oxides, the nanocomposites have more uniform particle morphology and better electrochemical properties. The effects of hydrothermal reaction time on the morphology and electrochemical properties of nanocomposites were studied. The 2O4/RGO nanocomposites with hydrothermal reaction time of 8 h have the most suitable particle size and excellent electrochemical performance. The particle size is about 50 nm, the first discharge capacity is 1486.9 mAh/ g, the first Coulomb efficiency is 73.7% and the capacity is 743 mAh/ g after 50 charge-discharge cycles. Spinel ZnMn2O4/RGO nanocomposites were synthesized by a simple hydrothermal method using Zn (Ac) 2 4H2O and Mn (Ac) 2 4H2O as metal sources. Compared with the pure ZnMn2O4 nanoparticles, the ZnMn2O4 / RGO nanocomposites have more uniform particle morphology and better electrochemical properties. The effects of hydrothermal reaction time on the morphology and electrochemical properties of nanocomposites were studied. The ZnMn2O4/RGO nanocomposites with hydrothermal reaction time of 10 h have the best comprehensive properties. The particle size of metal oxide is about 30 nm, the initial discharge capacity is 1279.7 mg / g at current density of 100 mA/g, and the specific capacity is 796.9 mg / g after 50 cycles. Compared with the second discharge specific capacity, the capacity retention rate is up to 96.07. In this paper, a simple one step hydrothermal method is used to achieve high crystallinity spinel nanometallic oxides attached to the reduced graphene oxide lamellae without the need of high temperature sintering. By controlling the kinds of metal elements, the particle size and charge / discharge platform can be controlled, which provides a new idea for the preparation of lithium ion battery anode materials with low cost, simple process and high specific capacity.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB383.1;TM912
[Abstract]:As a green secondary battery, lithium ion battery has been widely used in people's daily life. Because of its low theoretical specific capacity (372 mAh/g), the graphite anode produced commercially can not satisfy its application in the field of energy storage. Transition metal oxides with high theoretical specific capacity (600-1000m Ah/g), especially manganese spinel metal oxides, are of stable structure, wide source, low cost and friendly to the environment. However, it is easy to change the volume during charge and discharge, which leads to the collapse of electrode structure and poor electrical conductivity, which limits its application. In this paper, manganese spinel type transition metal oxides were loaded on graphene lamellae to relieve the stress of metal oxide volume change and to improve its electrical conductivity. The main contents of this paper are as follows: the improved Hummers method is used to prepare graphene oxide. Using CoCl2 6H2O and MnCl2 4H2O as metal source, water as solvent and ammonia as precipitant, spinel (Coomn) 2O4/RGO nanocomposites were synthesized by simple and mild one step hydrothermal method with low cost raw materials. Compared with the pure metal oxides, the nanocomposites have more uniform particle morphology and better electrochemical properties. The effects of hydrothermal reaction time on the morphology and electrochemical properties of nanocomposites were studied. The 2O4/RGO nanocomposites with hydrothermal reaction time of 8 h have the most suitable particle size and excellent electrochemical performance. The particle size is about 50 nm, the first discharge capacity is 1486.9 mAh/ g, the first Coulomb efficiency is 73.7% and the capacity is 743 mAh/ g after 50 charge-discharge cycles. Spinel ZnMn2O4/RGO nanocomposites were synthesized by a simple hydrothermal method using Zn (Ac) 2 4H2O and Mn (Ac) 2 4H2O as metal sources. Compared with the pure ZnMn2O4 nanoparticles, the ZnMn2O4 / RGO nanocomposites have more uniform particle morphology and better electrochemical properties. The effects of hydrothermal reaction time on the morphology and electrochemical properties of nanocomposites were studied. The ZnMn2O4/RGO nanocomposites with hydrothermal reaction time of 10 h have the best comprehensive properties. The particle size of metal oxide is about 30 nm, the initial discharge capacity is 1279.7 mg / g at current density of 100 mA/g, and the specific capacity is 796.9 mg / g after 50 cycles. Compared with the second discharge specific capacity, the capacity retention rate is up to 96.07. In this paper, a simple one step hydrothermal method is used to achieve high crystallinity spinel nanometallic oxides attached to the reduced graphene oxide lamellae without the need of high temperature sintering. By controlling the kinds of metal elements, the particle size and charge / discharge platform can be controlled, which provides a new idea for the preparation of lithium ion battery anode materials with low cost, simple process and high specific capacity.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB383.1;TM912
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