本文選題：鋰電池　切入點(diǎn)：二氧化鉬　出處：《上海交通大學(xué)》2014年博士論文　論文類型：學(xué)位論文

【摘要】：二氧化鉬（MoO2）具有導(dǎo)電性好、穩(wěn)定性高和理論容量高等優(yōu)點(diǎn)，是目前鋰離子電池負(fù)極材料研究的熱點(diǎn)材料之一。但是，二氧化鉬的實(shí)際充放電比容量很低。這是由于在充放電過程中，二氧化鉬初步鋰化形成的低導(dǎo)電性的Li0.98MoO2阻止了二氧化鉬的進(jìn)一步鋰化。同時(shí)，由于充放電過程中二氧化鉬有很大的體積膨脹，使得二氧化鉬的循環(huán)性能也很差。更重要的是，不同于一般的金屬氧化物，二氧化鉬的充放電比容量在前30個(gè)循環(huán)會(huì)有一個(gè)增加的過程。這個(gè)不尋常的現(xiàn)象在目前文獻(xiàn)中還沒有得到很好的解釋，，一般被簡單的認(rèn)為是電極材料活化的過程。因此，本文主要的工作包括以下幾方面： (1)通過引入多級(jí)孔結(jié)構(gòu)來提高二氧化鉬充放電過程中鋰離子和電子的傳輸速率和二氧化鉬材料結(jié)構(gòu)的穩(wěn)定性，從而提高二氧化鉬的充放電容量和改善其循環(huán)性能。本文中以介孔碳CMK-3為模板劑和還原劑，用一步碳熱還原法合成了二氧化鉬納米管。在深入研究了不同三氧化鉬和CMK-3的質(zhì)量比，煅燒的溫度和時(shí)間對(duì)于二氧化鉬結(jié)構(gòu)和形貌影響的基礎(chǔ)上，研究了這些因素對(duì)二氧化鉬電化學(xué)性能的影響。研究表明：當(dāng)三氧化鉬和CMK-3的質(zhì)量比為10:1、煅燒溫度為820°C、反應(yīng)時(shí)間為90分鐘時(shí)合成出的二氧化鉬納米管具有最好的循環(huán)性能和倍率性能。在電流密度為100mA g-1下充放電70圈之后，二氧化鉬的放電比容量仍有720mAh g-1。 (2)在含有多級(jí)孔結(jié)構(gòu)二氧化鉬納米管的基礎(chǔ)上，通過引入具有高導(dǎo)電性的碳化鉬（Mo2C）進(jìn)一步提高二氧化鉬的充放電比容量和改善其循環(huán)性能。仍然采用一步碳熱還原法，通過控制前驅(qū)物三氧化鉬和CMK-3的比例成功合成了具有多級(jí)孔結(jié)構(gòu)的MoO2/Mo2C納米管。研究了不同二氧化鉬和碳化鉬的質(zhì)量比對(duì)二氧化鉬和碳化鉬復(fù)合材料的循環(huán)性能和倍率性能的影響。研究表明，在碳化鉬含量為30%時(shí)，二氧化鉬和碳化鉬復(fù)合材料具有最高的充放電比容量和最好的循環(huán)性能和倍率性能。在電流密度為200mAg-1下充放電100圈之后，二氧化鉬和碳化鉬復(fù)合材料的放電比容量仍有790mAh g-1。 (3)通過原位碳包覆的方法來提高二氧化鉬的導(dǎo)電性，從而提高二氧化鉬的充放電比容量和循環(huán)性能。采用新穎的模板輔助法來達(dá)到原位碳包覆的目的。本文中以甲醛和間苯二酚為軟模板劑，在水熱條件下與四水合七鉬酸銨（AHM）作用首先得到三氧化鉬（MoO3）/酚醛樹脂的球型復(fù)合物。再將此三氧化鉬酚醛樹脂復(fù)合物在氮?dú)獗Ｗo(hù)下的管式爐中煅燒后獲得刺狀球型二氧化鉬/碳復(fù)合物。研究了不同酚醛樹脂與AHM質(zhì)量比和煅燒溫度對(duì)于二氧化鉬/碳復(fù)合物的形貌和電化學(xué)性能的影響。研究表明，在加入的間苯二酚質(zhì)量為3.20g、AHM質(zhì)量為3.09g、甲醛溶液為7mL、煅燒溫度為600°C時(shí)所合成的二氧化鉬/碳復(fù)合物具有最好的循環(huán)性能和倍率性能。在電流密度為1.0A/g下循環(huán)400圈后，二氧化鉬/碳復(fù)合物的充放電比容量仍有520mAh g-1。 (4)二氧化鉬材料在進(jìn)行前30圈充放電時(shí)，充放電比容量會(huì)逐漸上升。這個(gè)不同于一般金屬氧化物材料的現(xiàn)象，一般被解釋成二氧化鉬電極材料逐漸活化的過程。本文中利用原位XRD技術(shù)，觀察了在充放電過程中電極材料的物相變化。通過研究所得的XRD譜圖和二氧化鉬結(jié)構(gòu)的特點(diǎn)，發(fā)現(xiàn)二氧化鉬前30圈充放電比容量上升是由于二氧化鉬鋰化機(jī)制的轉(zhuǎn)化所引起的。二氧化鉬通過脫嵌機(jī)制首先形成Li0.98MoO2，這個(gè)過程高度可逆。在充放電循環(huán)過程中，少量的Li0.98MoO2通過轉(zhuǎn)化機(jī)制轉(zhuǎn)化為Mo和Li2O。經(jīng)過30圈循環(huán)后，二氧化鉬通過轉(zhuǎn)化機(jī)制與Mo和Li2O進(jìn)行高度可逆的充放電過程。
[Abstract]:Two molybdenum oxide (MoO2) has good conductivity, high stability and high theoretical capacity, is one of the hot material of anode materials for lithium ion batteries at present. However, the actual charge and discharge two molybdenum oxide low specific capacity. This is because in the process of charge and discharge, low conductive molybdenum oxide is formed at the beginning of two step Li0.98MoO2 lithium prevents further lithiation of two molybdenum oxide. At the same time, because the two molybdenum oxide charge discharge process a large volume expansion cycle performance of the two molybdenum oxide is also very poor. More importantly, different from the general metal oxide, molybdenum oxide two charge discharge capacity than before 30 cycles there will be an increase in the process. This is an unusual phenomenon in the literature has not been well explained, generally known simply as the process of electrode material activation. Therefore, the main work of this paper includes the following aspects:
(1) to improve the stability of the transmission rate of lithium ions and electrons of two molybdenum oxide charge discharge process and two molybdenum oxide material structure by introducing hierarchical pore structure, so as to enhance the two molybdenum oxide charge discharge capacity and improve the performance of the cycle. The template agent and reducing agent with mesoporous carbon CMK-3 in this paper, two molybdenum oxide nanotubes were synthesized by one-step carbothermal reduction method. The quality of in-depth study of different MoO3 and CMK-3 ratio, calcination temperature and time effect for two molybdenum oxide structure and morphology, studied the effects of these factors on the electrochemical performance of two molybdenum oxide. The results show that: when the MoO3 and CMK-3 the mass ratio of 10:1, calcining temperature is 820 C, the reaction time is two to 90 minutes when the molybdenum oxide nanotubes synthesized with the cycle performance and rate performance is the best. When the current density is 100mA g-1 after 70 charge discharge cycles, two oxygen The discharge specific capacity of Mo is still 720mAh g-1.
(2) based on hierarchical pore structure containing two molybdenum oxide nanotubes, we introduce a molybdenum carbide high conductivity (Mo2C) to further improve the charge discharge specific capacity of two molybdenum oxide and improve the performance of the cycle. Still by one-step carbothermal reduction method by controlling the precursor of three oxygen molybdenum and CMK-3 the proportion of successful synthesis of hierarchical pore structure of MoO2/Mo2C nanotubes was studied. The cycle performance and rate performance of mass ratio of two different molybdenum oxide and molybdenum carbide two molybdenum oxide and molybdenum carbide composites. The results show that the molybdenum carbide content of 30%, two molybdenum oxide and molybdenum carbide composite with the cycle performance and the charge discharge rate performance of the highest specific capacity and the best. When the current density is 200mAg-1 after 100 charge discharge cycles, discharge two molybdenum oxide and molybdenum carbide composite material specific capacity is still 790mAh g-1.
(3) to improve the conductivity of two molybdenum oxide by means of in-situ carbon coating, thereby improving two molybdenum oxide charge discharge specific capacity and cycle performance. To achieve the purpose of in-situ carbon coating using template assisted method. The novel formaldehyde and resorcinol as soft template in this paper, and seven in four hydrated ammonium molybdate under hydrothermal conditions (AHM) function is firstly obtained MoO3 (MoO3) / ball type composite phenolic resin. Then after calcination furnace the MoO3 phenolic resin composites under the protection of nitrogen in the spiny ball type two molybdenum oxide / carbon composites. Effects of different phenolic resin and AHM mass ratio the effect of the calcination temperature and the morphology and electrochemical performance of carbon composite molybdenum oxide / two. The results show that in the presence of resorcinol mass 3.20g, AHM quality 3.09g, Formaldehyde Solution 7mL, two oxygen molybdenum synthesis calcination temperature is 600 ~ C / The carbon composite has the best cycle performance and rate performance. When the current density is 1.0A/g, the charge and discharge capacity of two moo / C composite is 520mAh g-1. after 400 cycles.
(4) two molybdenum oxide material in the first 30 charge / discharge cycles, the charge discharge capacity will gradually increase. This is different from the metal oxide material phenomenon, is generally interpreted as the process of two molybdenum oxide electrode materials gradually activated by in situ XRD technology. In this paper, the observation of electrode materials in charge and discharge in the process of phase change. Through the study of the XRD spectrum and the structure of two molybdenum oxide, molybdenum oxide was found in two before the 30 ring discharge capacity is increased due to the transformation of two molybdenum oxide lithium mechanism caused by two. Molybdenum oxide intercalation mechanism first form Li0.98MoO2, this process is highly reversible. The charge discharge cycle process, a small amount of Li0.98MoO2 by the transformation mechanism into Mo and Li2O. after 30 cycles, the charge and discharge process of two molybdenum oxide were highly reversible by the transformation mechanism with Mo and Li2O.

【學(xué)位授予單位】：上海交通大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2014
【分類號(hào)】：TQ136.12;TM912

【參考文獻(xiàn)】

相關(guān)期刊論文 前1條

1 張豪杰;王開學(xué);陳接勝;;新型球狀磷酸鐵鋰的合成及電化學(xué)性能[J];高等學(xué)校化學(xué)學(xué)報(bào);2011年03期

本文編號(hào)：1570192