本文選題：氧化鉬　切入點：MoO_2/RGO　出處：《新疆大學》2017年碩士論文　論文類型：學位論文

【摘要】：鋰離子電池(Li-ion Battery,LIB)因具有較長的循環(huán)壽命、較高的能量密度、對環(huán)境比較友好而受到廣泛應用,小到便攜式電子產(chǎn)品(手機、手表)大到電動汽車等生活的各個方面。石墨的成本不高,工作電勢比較低,最重要的是它的導電性很好,所以石墨是目前使用最普遍、也是最早商業(yè)化的鋰電負極材料。然而石墨本身的結構特征使它在脫嵌鋰的過程中(富鋰狀態(tài))下容易生成LiC_6這種計量比的石墨層間化合物,而局限了多個碳原子中只能插入一個鋰,從而導致的結果就是可逆容量比較低,只有三百多毫安時每克,在一定程度上不能滿足目前的商業(yè)要求。所以,當今社會,人們對鋰離子電池有了電容量更高這樣的要求,這就促使科研人員正在研究比現(xiàn)有技術更先進、性能更好的新型材料。要取得這樣的成果,必須要選擇容量更高、穩(wěn)定性更好的電極材料,以期在保證安全的前提下,最大限度的提高電池容量、循環(huán)壽命和充放電速率。鉬系氧化物和硫化物納米材料儲量比較豐富,而且將其用作LIB負極材料時,表現(xiàn)出了優(yōu)異的電化學性能,到目前為止已成為電化學方面的研究熱點。本文通過溶劑熱法合成了不同形貌的氧化鉬納米材料和MoO_2/還原氧化石墨烯復合納米材料;利用熔融鹽焙燒法合成了MoS_2/C復合納米材料,并對合成的這些樣品在鋰電方面的應用性進行了研究。首先我們用二水合鉬酸鈉為鉬源,通過兩相溶劑熱法調控得到了不同形貌和物相的氧化鉬納米材料,再將電化學性能比較好的樣品Mo-200(即單斜晶系的MoO_2)與還原氧化石墨烯進行復合,探討還原氧化石墨烯的加入對該材料在電化學性能上的提高;最后以新疆特色資源腐植酸鉀為碳源,利用熔融鹽焙燒法成功制備了MoS_2/C復合納米材料,之后將合成的材料用作LIB負極材料,并且還與商品MoS2在電化學方面的性能進行了對比研究。具體研究內容如下:(1)兩相溶劑熱法合成不同形貌的氧化鉬納米材料及其電化學性能研究:利用兩相溶劑熱法,通過改變溶劑熱的溫度,對產(chǎn)物的物相和形貌進行了調控,并對其進行了電化學性能測試。電化學研究表明:200 o~C水熱下得到的樣品(Mo-200)即單斜相的MoO_2表現(xiàn)出了最佳的循環(huán)穩(wěn)定性和倍率性能,它在電流密度為100 mA g~-1的條件下循環(huán)50圈之后,電化學容量還是能夠保持在485.3mAh g~-1,比其他溶劑熱溫度下(120,150和180 o~C)得到樣品的放電比容量要高。(2)兩相溶劑熱法合成MoO_2/還原氧化石墨烯(MoO_2/RGO)納米復合材料及其電化學性能研究:將Mo-200與氧化石墨烯(GO)進行復合,在這個過程中,GO被高溫水熱還原得到還原氧化石墨烯(RGO),最終我們得到MoO_2/RGO復合納米材料。電化學研究表明,加入一定量的RGO后,MoO_2/RGO復合納米材料的導電性提高,阻抗變小,表現(xiàn)出了更加優(yōu)異的電化學性能,在電流密度為100 mA g~-1的條件下循環(huán)50圈之后,電化學容量依然能夠保持在765.1mAh g~-1,比單一MoO_2的放電比容量高279.8 mAh g~-1。(3)以腐植酸鉀為炭源制備MoS_2/C復合納米材料及其電化學性能研究:利用價格低廉的新疆特色資源腐植酸鉀為炭源,直接焙燒得到MoS_2/C復合納米材料,通過改變焙燒溫度,對產(chǎn)物的形貌進行了調控,并對其進行了電化學性能測試。電化學研究表明:700 o~C焙燒得到的MoS_2/C表現(xiàn)出了最佳的循環(huán)穩(wěn)定性和倍率性能,它在電流密度為100 mA g~-1的條件下循環(huán)50圈之后,電化學容量依然能夠保持在554.9 mAh g~-1。
[Abstract]:Lithium ion battery (Li-ion, Battery, LIB) because the cycle life is longer, higher energy density, more friendly to the environment and has been widely applied to small, portable electronic products (mobile phone, watch) to electric cars and other aspects of life. The graphite cost is not high, the working potential is relatively low, the most important is it a good conductivity, so the graphite is currently the most commonly used, but also the first commercial lithium ion battery anode material. However, due to its structural characteristics of graphite in the process of Li + intercalation (lithium rich state) easy to generate LiC_6 the measurement of graphite layer ratio compounds, and a number of limitations you can only insert a carbon atom in lithium, which is the result of the reversible capacity is relatively low, only more than 300 Ma per gram, can not meet the requirements of the business to a certain extent. So, in today's society, people of a lithium ion battery Higher capacitance of such requirements, which prompted researchers are working on more advanced than the existing technology, new materials with better properties. To achieve such results, we must choose the higher capacity, better stability of electrode materials, in order to ensure the safety of the premise, improve the capacity of the battery to the greatest extent, circulation life and charge discharge rate. Rich molybdenum oxide and reserves, and be used as anode material LIB, showed excellent electrochemical performance, so far has become a research hot point of electrochemistry. This paper through the solvothermal synthesis of different morphologies of molybdenum oxide nano materials and MoO_2/ graphite oxide graphene nanocomposites reduction; MoS_2/C nanocomposites were prepared by molten salt roasting method, and the application of the synthesis of these samples in the aspects of lithium was studied. First, we With two hydrated sodium molybdate as molybdenum source by solvent thermal method regulation with different morphologies were obtained and molybdenum oxide nano material phase, then the samples Mo-200 better electrochemical properties (i.e. monoclinic MoO_2) and reduction of graphene oxide compound, investigation of redox graphene added to improve the material in the electrochemical performance; taking Xinjiang characteristic resources of potassium humate as carbon source, MoS_2/C nanocomposites were prepared by molten salt roasting method was successful. After the synthetic material is used as anode material LIB, and also with the goods in the electric chemical properties of MoS2 was studied. The main research contents are as follows: (1) study of molybdenum oxide nanomaterials with different morphologies and electrochemical properties of synthetic two-phase solvothermal method using two-phase solvothermal method, by changing the solvent thermal temperature, phase and morphology of the products were regulation, And has carried on the electrochemical performance test. Electrochemical studies indicate that 200 o~C hydrothermal samples (Mo-200) namely monoclinic phase MoO_2 showed the best cycle stability and rate capability, after it at a current density of 100 mA g~-1 under the condition of 50 cycles, the electrochemical capacity can still keep in 485.3mAh g~-1, other than the solvothermal temperature (120150 and 180 o~C) to get the discharge specific capacity of the sample is higher. (2) the synthesis of MoO_2/ two-phase solvothermal reduction of graphene oxide (MoO_2/RGO) nano composite material and its electrochemical properties: Mo-200 and graphene oxide (GO) compound, in this process, GO by the reduction of graphene oxide high temperature hydrothermal reduction (RGO), we obtained MoO_2/RGO nanocomposites. The electrochemical studies show that adding a certain amount of RGO, the conductivity of MoO_2/RGO nanocomposites increased, impedance becomes small , showed more excellent electrochemical performance, after the current density is 100 mA g~-1 under the condition of 50 cycles, the electrochemical capacity is still able to maintain in the 765.1mAh g~-1 than single MoO_2 discharge of high specific capacity of 279.8 mAh g~-1. (3) to study the electrochemical properties of MoS_2/C composite nano material and its preparation process of potassium humate as carbon source using cheap Xinjiang characteristic resources of potassium humate as carbon source, directly calcined to obtain MoS_2/C nanocomposites, by changing the calcination temperature on the morphology of the products was regulated, and its electrochemical performance test. Electrochemical studies indicate that 700 o~C roasting MoS_2/C showed optimal cycling stability and rate capability after that, the current density is 100 mA at g~-1 under the condition of 50 cycles, the electrochemical capacity can still maintain at 554.9 mAh g~-1.

【學位授予單位】：新疆大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TB383.1;TM912

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本文編號：1645807