發(fā)布時間：2018-03-19 21:27

  本文選題：鋰離子電池　切入點：負極材料　出處：《華中科技大學》2014年博士論文　論文類型：學位論文

【摘要】：隨著電子科技的飛速發(fā)展,移動設備如手機、筆記本電腦、電子閱讀器等便攜設備隨著功能的豐富耗電量逐漸增加,其對于鋰離子電池在比容量,使用壽命和充電速度方面的要求越來越嚴苛。隨著傳統(tǒng)化石燃料的日益衰竭,對于新型能源如風能,太陽能的儲存顯得尤為重要,鋰離子電池被視為理想候選者之一。而目前傳統(tǒng)的材料鈷酸鋰和石墨已不能滿足現(xiàn)在的需求。因而開發(fā)高容量、高倍率、長循環(huán)壽命,廉價環(huán)保的新型電極材料迫在眉睫。 本文以鋅基金屬氧化物為研究對象,采用納米化和碳材料雜化等手段合成了一系列具有納米結構的復合材料,并對其電化學性能進行了研究。具體內容包括以下幾個方面： 采用醋酸鋅和氧化鍺為反應物,在水和叔丁胺的混合溶劑中進行水熱反應合成鍺酸鋅,通過調控反應物濃度和溶劑中水和叔丁胺的比例,合成了具有海膽狀形貌的鍺酸鋅納米材料,構成分級結構的納米棒直徑約為20nm,長度約為500nm,這種一維結構有利于電荷的傳輸,提高傳輸效率。且納米棒之間的空隙可在一定程度上緩解儲鋰過程中的體積膨脹,提高結構穩(wěn)定性。電化學表征結果表明其具有較高的比容量和較好的倍率性能。與此同時,還對材料的生長機理進行了研究,研究結果對于合成類似結構的氧化物具有一定的參考價值。 采用微波輔助水熱法,利用鍺酸鋅-乙二胺雜化物納米帶作為前驅體,將其均勻分散在氧化石墨烯(GO)懸浮液中,通過微波加熱手段在短時間內(15分鐘)合成鍺酸鋅/氮摻雜石墨烯復合物。在反應過程中,微波引發(fā)的分子間高頻率的振動可以極大地加速化學反應的進行,使得鍺酸鋅—乙二胺雜化物中的乙二胺分子迅速脫離出本體,與氧化石墨烯進行反應,在將其還原為石墨烯的同時進行氮原子摻雜。在最終產(chǎn)物中,鍺酸鋅納米棒被氮摻雜石墨烯緊緊包裹,電化學測試結果表明,相比在同樣反應條件下合成的無石墨烯包覆的鍺酸鋅納米棒,其性能得到了顯著的提升。Zn2GeO4/氮摻雜石墨烯復合材料在100mAg-1的電流密度下進行放—充電循環(huán)100次仍可保持1044mAhg-1的可逆比容量。即使在電流密度高達3.2Ag-1的條件下,其比容量也遠高于傳統(tǒng)石墨材料,達到531mAh g-1。 開發(fā)了一種廉價環(huán)保的方法,在室溫下利用離子交換反應成功制備了具有三明治結構的鍺酸鋅/氧化石墨烯復合材料。合成的復合材料中,鍺酸鋅納米棒均勻地嵌入在氧化石墨烯層間,其在儲鋰過程中產(chǎn)生的體積膨脹可以得到很好的緩沖。得益于結構的保持,復合物在首次放電過程中產(chǎn)生的Li20可以在隨后的充電過程中部分可逆轉化為鋰離子和金屬氧化物,通過計算,Li20的可逆程度可達64%,比容量得到極大提升。得到的復合材料無論在容量、循環(huán)壽命還是倍率性能方面都表現(xiàn)出優(yōu)異的性能。此外,鍺酸鋅納米棒的嵌入避免了氧化石墨烯層間的堆疊,提高了氧化石墨烯的利用率,有效降低了復合物中的碳含量,從而提升了材料的體積能量密度,為將來大規(guī)模應用提供可能。 利用空心八面體結構的金屬有機框架材料作為前驅體,在氮氣氣氛下進行熱處理得到了介孔結構的氧化鋅/鐵酸鋅/碳的空心八面體。歸功于金屬有機框架的特殊結構,其在熱處理過程中,有機配體碳化后可均勻的包覆在由金屬元素形成的氧化物納米顆粒表面。金屬氧化物顆粒由于受到碳層的限制,顆粒尺寸僅為5nm左右,形成的八面體結構壁厚僅為10nm左右,孔徑大小為7.5nm。將其作為鋰離子電池負極材料表現(xiàn)出極為優(yōu)異的性能,在500mA g-1的電流密度下,首次循環(huán)過程中可逆比容量高達1047mAh g-1,庫侖效率達到75.6%,較其他類似氧化物有所提升,且100次循環(huán)之后比容量增至1390mAh g-1,即使在電流密度增加至1OAg-1的情況下,可逆比容量仍高達762mAh g-1。如此出色的性能要歸功于其特殊的結構,小尺寸的氧化物納米顆粒加上均勻的碳包覆層可以有效緩解充放電過程中的體積膨脹,多孔空心結構有利于電解液的浸潤,增加電解液與顆粒之間的接觸面,提高電化學反應動力學,極薄的壁厚可以有效縮短鋰離子的傳輸路徑,提高材料的倍率性能。
[Abstract]:With the rapid development of electronic technology, mobile devices such as mobile phone, notebook computer, electronic reader and other portable devices increases gradually with rich power consumption function, the specific capacity for lithium ion batteries in terms of life, and the speed of the charging requirements more stringent. With the traditional fossil fuel depletion, for new energy such as wind energy the solar energy storage, it is particularly important, the lithium ion battery is regarded as one of the ideal candidates. At present, the traditional material LiCoO2 and graphite has been unable to meet the demand. So the development of high capacity, high rate, long cycle life, imminent new electrode materials for environmental protection. Cheap
Based on zinc based metal oxides, a series of nanostructured composites were synthesized by means of Nanocrystallization and carbon material hybridization, and their electrochemical properties were studied.
Using zinc acetate and germanium oxide as reactants, synthesis of germanium hydrothermal reaction of acid zinc in the mixed solvent of water and tert butylamine, by regulating the concentration of reactant and solvent water and tert butylamine proportion of zinc germanate nanometer material with sea urchin like morphology were synthesized, a hierarchical structure of the nanorod diameter is about 20nm. The length is about 500nm, the one-dimensional structure is conducive to the transmission of charge, improve the transmission efficiency. The gap between the nanorods and storage during lithium expansion to ease to a certain extent, improve the stability of structure. Electrochemical characterization results show that it has high specific capacity and good rate performance. At the same time, also on the growth mechanism of materials the research results have certain reference value for the synthesis of the similar structure of the oxide.
By microwave assisted hydrothermal method using zinc germanate ethylenediamine hybrid nanoribbons as precursor, which are evenly dispersed on graphene oxide (GO) suspension, by means of microwave heating in a short period of time (15 minutes) the synthesis of zinc germanate / nitrogen doped graphene complex in the reaction process. In the inter molecular microwave high frequency vibration can greatly accelerate the chemical reaction, the ethylenediamine germanate zinc - ethylenediamine hybrid in rapidly out of body, react with graphene oxide, in the reduction of graphene doping of nitrogen atoms. At the same time. In the final product. Germanate ZnO nanorods by nitrogen doped graphene wrapped tightly, the electrochemical test results show that compared with the same reaction conditions without the graphene coated zinc germanate nanorods synthesized, its performance has been significantly improved.Zn2GeO4/ nitrogen doped graphene composite Under the current density of 100mAg-1, the charging cycle of 1044mAhg-1 can maintain the reversible specific capacity of 3.2Ag-1 for 100 times. Even at the current density of 3.2Ag-1, its specific capacity is much higher than that of traditional graphite material, reaching 531mAh g-1..
The development of a low-cost method of environmental protection, the use of acid / Zinc Germanium ion with sandwich structure of graphene oxide composite materials were prepared successfully in the exchange reaction at room temperature. The synthesis of composite materials, zinc germanate nanorods were uniformly embedded in the graphene oxide layer, the lithium storage in the process of volume expansion can get good buffer. Due to the structure, compound produced in the first discharge process of Li20 in the process of charging into partially reversible lithium ion and metal oxide, through calculation, up to 64% degree of reversibility of Li20, greatly enhance the specific capacity. The resulting composite materials both in capacity the life cycle, or rate performance has shown excellent performance. In addition, zinc germanate nanorods embedded avoid stacked graphene oxide layers, improve the utilization rate of graphene oxide, effectively reduced The carbon content in the compound is lower and the volume energy density of the material is enhanced, which provides the possibility for large-scale applications in the future.
Metal organic framework materials with hollow structure eight as precursor, heat treatment in nitrogen atmosphere were obtained mesoporous structure Zinc Oxide / zinc ferrite / carbon hollow eight face. Due to the special structure of metal organic frameworks, in the process of heat treatment, the organic ligands after carbonization can be uniformly in the coating formed by the metal elements in the surface oxide nano particles. The metal oxide particles due to the carbon layer, the particle size is only about 5nm, eight structure formed wall thickness is only about 10nm, the pore size of 7.5nm. anode materials for lithium ion batteries are shown as extremely excellent performance in current the density of 500mA g-1, the first cycle reversible capacity up to 1047mAh g-1, the coulombic efficiency reached 75.6%, compared with other similar oxide has improved, and after 100 cycles the specific capacity of 1390mAh to g-1, even in The current density is increased to 1OAg-1, the reversible capacity is still as high as 762mAh g-1. so excellent performance due to its special structure, the small size of the oxide nanoparticles with uniform carbon coating can effectively alleviate the charge and discharge process of the volume expansion, porous hollow structure is conducive to the increase of electrolyte infiltration. The contact surface between the electrolyte and the particles, improve the electrochemical reaction kinetics, transmission path of thin wall thickness can effectively shorten the lithium ion, improve the rate performance of the material.

【學位授予單位】：華中科技大學
【學位級別】：博士
【學位授予年份】：2014
【分類號】：TQ127.11;TM912

【共引文獻】

相關期刊論文 前10條

1 陳美娟;;鋰離子電池正極材料Li_3V_2(PO_4)_3存在的問題及改性研究進展[J];材料導報;2013年S1期

2 劉芯言;彭媒，

本文編號：1636075