錳系尖晶石金屬氧化物的水熱制備與電化學性能研究
發(fā)布時間：2018-08-02 18:49
【摘要】：鋰離子電池作為綠色二次電池已經廣泛的應用到了人們的日常生活中。目前已商業(yè)化生產的石墨負極由于其理論比容量(372 mAh/g)較低,已不能滿足其在儲能領域中的應用。具有高理論比容量(600-1000 m Ah/g)的過渡金屬氧化物尤其是錳系尖晶石金屬氧化物,其結構穩(wěn)定、來源廣泛、成本低廉、且對環(huán)境友好而成為鋰離子電池負極材料的研究熱點。但其在充放電過程中容易發(fā)生體積變化導致電極材料結構的崩塌且導電性較差,限制了其應用。本文通過將錳系尖晶石型過渡金屬氧化物負載在石墨烯片層上緩解金屬氧化物體積變化應力的同時提高其導電性。本文的主要研究內容如下:采用改進的Hummers法制備氧化石墨烯。以CoCl2·6H2O和MnCl2·4H2O為金屬源,水為溶劑,氨水為沉淀劑,采用成本低廉的原材料以及簡單溫和的一步水熱法合成尖晶石(Co,Mn)(Co,Mn)2O4/RGO納米復合材料。與單純的金屬氧化物相比,此納米復合材料具有更均勻的顆粒形貌以及更優(yōu)異的電化學性能。通過控制水熱反應時間來研究其對納米復合材料的形貌結構以及電化學性能的影響。水熱反應時間為8 h的尖晶石(Co,Mn)(Co,Mn)2O4/RGO納米復合物具有最合適的粒徑以及最優(yōu)異的電化學性能。顆粒粒徑在50 nm左右,首次放電容量為1486.9 mAh/g,首次庫倫效率為73.7%,50次充放電循環(huán)后容量為743 mAh/g。以Zn(Ac)2·4H2O和Mn(Ac)2·4H2O為金屬源,采用簡單的一步水熱法合成尖晶石ZnMn2O4/RGO納米復合材料。與單純的ZnMn2O4納米顆粒相比,ZnMn2O4/RGO納米復合材料具有更均勻的顆粒形貌以及更優(yōu)異的電化學性能。通過控制水熱反應時間來研究其對納米復合材料的形貌結構以及電化學性能的影響。水熱反應時間為10 h的得到的ZnMn2O4/RGO納米復合材料綜合性能最佳。其中金屬氧化物顆粒尺寸均勻,顆粒粒徑約為30 nm,在100 mA/g的電流密度下,首次放電容量為1279.7 mAh/g,循環(huán)50圈后比容量為796.9 mAh/g,相比于第二次放電比容量,容量保持率高達96.07%。本文通過簡單的一步水熱法,不需要高溫燒結就能實現(xiàn)高結晶度的尖晶石納米金屬氧化物附著在還原的氧化石墨烯片層上。通過控制金屬元素的種類可以控制顆粒的尺寸、充放電平臺,為獲得成本低、制備工藝簡單且高比容量的鋰離子電池負極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.
【學位授予單位】：哈爾濱工業(yè)大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：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.
【學位授予單位】：哈爾濱工業(yè)大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TB383.1;TM912
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