發(fā)布時(shí)間：2018-03-12 12:26

  本文選題：儲(chǔ)能　切入點(diǎn)：鋰離子電池　出處：《大連理工大學(xué)》2017年博士論文　論文類型：學(xué)位論文

【摘要】：隨著新能源產(chǎn)業(yè)的不斷發(fā)展,發(fā)展具有長循環(huán)穩(wěn)定性、高可逆容量、良好的安全性能和快速充放電能力的儲(chǔ)能材料,是世界能源發(fā)展趨勢,符合我國能源戰(zhàn)略需求,成為研究者關(guān)注的熱點(diǎn)。金屬基納米材料在儲(chǔ)能領(lǐng)域扮演重要角色,特別是在鋰離子電池負(fù)極材料應(yīng)用方面,其微觀結(jié)構(gòu)決定了其儲(chǔ)鋰性能。面臨的共性問題是循環(huán)過程中體積變化大,容量衰減嚴(yán)重,特別是過渡金屬氧化物材料存在電子導(dǎo)電率低的問題。炭材料具有高的電子導(dǎo)電性,結(jié)構(gòu)形貌可控,表面化學(xué)性質(zhì)可調(diào)且環(huán)境友好,將炭材料與金屬基納米材料進(jìn)行復(fù)合能有效改善鋰離子電池負(fù)極材料的性能。本論文以高容量負(fù)極材料的結(jié)構(gòu)設(shè)計(jì)合成為目標(biāo),旨在提高炭材料與活性組分的緊密接觸,并結(jié)合氮摻雜和創(chuàng)造多孔結(jié)構(gòu),發(fā)展了三種炭包覆負(fù)極材料的有效新方法,構(gòu)筑了一系列具有新穎結(jié)構(gòu)的炭包覆納米復(fù)合材料,并將其應(yīng)用于鋰離子電池,顯示出高的可逆容量、循環(huán)穩(wěn)定性和倍率性能。在此基礎(chǔ)上,系統(tǒng)研究了炭包覆納米復(fù)合材料的結(jié)構(gòu)特點(diǎn)對其電化學(xué)性能的影響。具體包括如下幾個(gè)方面:(1)以納米二元金屬氧化物(ZnSnO_3)和2-甲基咪唑?yàn)榍膀?qū)體靶向生長金屬有機(jī)骨架ZIF-8制備了三維連續(xù)的氮摻雜炭包覆高含量(82.3 wt%)納米錫材料。根據(jù)軟硬酸堿理論,2-甲基咪唑作為交界堿優(yōu)先與交界酸Zn~(2+)結(jié)合生成ZIF-8包覆層,將高分散錫的氧化物引入ZIF-8網(wǎng)絡(luò)中。后續(xù)的熱解使ZIF-8轉(zhuǎn)變?yōu)楹胸S富氮元素(5.3wt%)的高導(dǎo)電連通的炭包覆網(wǎng)絡(luò),同時(shí),錫的氧化物炭熱還原為Sn納米粒子,被還原的低沸點(diǎn)的Zn在后續(xù)的熱解過程中揮發(fā)并產(chǎn)生豐富且開放的孔道結(jié)構(gòu),實(shí)現(xiàn)離子和電子的快速高效傳輸。鋰離子電池測試結(jié)果表明,Sn/C復(fù)合材料在0.2 A g~(-1)電流密度下首次放電容量為1321mAhg~(-1),庫倫效率高達(dá)80.1%。在0.2和1Ag~(-1)下分別循環(huán)150次后可逆容量可保持為901和690 mA hg~(-1)。此外,這種方法還可以擴(kuò)展到氮摻雜炭包覆氧化錳復(fù)合材料的合成,同樣展現(xiàn)出優(yōu)異的電化學(xué)性能。(2)從生物質(zhì)出發(fā),利用真菌木耳自身特有的可溶脹特性和多細(xì)胞網(wǎng)格結(jié)構(gòu)吸附Mn~(2+)溶液構(gòu)筑了三維高度交聯(lián)的MnO@C納米片網(wǎng)絡(luò)結(jié)構(gòu)。木耳細(xì)胞壁主要成分幾丁質(zhì)中富含羥基官能團(tuán),利用其與金屬離子的絡(luò)合作用將MnO納米粒子原位生成并固載于連通的炭納米片中,有效防止顆粒聚集長大。此外木耳細(xì)胞壁中的幾丁質(zhì)在通過后續(xù)干燥收縮和高溫?zé)峤?可以轉(zhuǎn)變?yōu)檫B續(xù)的氮摻雜炭導(dǎo)電包覆層,提高復(fù)合材料的導(dǎo)電性和結(jié)構(gòu)穩(wěn)定性。這種納米片網(wǎng)絡(luò)結(jié)構(gòu)不僅可以減小離子擴(kuò)散路徑,還能有效緩沖MnO在充放電過程中的體積變化。電化學(xué)測試結(jié)果表明,采用此方法合成的MnO@C復(fù)合材料在0.2 A g~(-1)電流密度下循環(huán)300次可逆容量為868 mAh g~(-1),在1 A g~(-1)下循環(huán)500次可逆容量為668 mAh g~(-1),證明其具有高的可逆容量和優(yōu)異的循環(huán)穩(wěn)定性。此外,這種可持續(xù)綠色的合成方法易于規(guī)�；覟楦咝阅芗{米片網(wǎng)絡(luò)結(jié)構(gòu)的設(shè)計(jì)合成提供了新的思路。(3)采用聚多巴胺包覆的過渡金屬碳酸鹽晶體在自身生成的弱氧化氣氛中限域熱解的方法構(gòu)筑炭包覆過渡金屬氧化物介孔微納結(jié)構(gòu)。以聚多巴胺包覆的MnCO_3晶體為例,熱解使外部的包覆層轉(zhuǎn)變?yōu)閷?dǎo)電炭保護(hù)殼,同時(shí)MnCO_3晶體在自身生成的CO_2氣體壓力推動(dòng)下爆裂為超小的納米MnO。原位生成的CO_2不僅作為造孔劑分別在材料內(nèi)部產(chǎn)生由內(nèi)而外貫通的介孔和在炭包覆層形成豐富的微孔,其還可以為過渡金屬氧化物的形成提供一個(gè)弱的氧化性氣氛,有效中和聚多巴胺熱解過程中產(chǎn)生的還原性氣氛,防止金屬相生成。采用這種方法分別制備了具有介孔微納結(jié)構(gòu)的炭包覆氧化錳、氧化鈷和氧化鐵材料。MnO@C復(fù)合材料在0.2和2 A g~(-1)電流密度下分別循環(huán)200和300次可逆容量高達(dá)886和770 mA h g~(-1),炭包覆氧化鈷和氧化鐵材料在0.2 A g~(-1)電流密度下可逆容量分別可達(dá)1058和770mAhg~(-1),同時(shí)具有良好的循環(huán)穩(wěn)定性。這種合成方法可以同時(shí)實(shí)現(xiàn)炭包覆核殼結(jié)構(gòu)、貫通的介孔結(jié)構(gòu)和微納結(jié)構(gòu)的多級(jí)結(jié)構(gòu)優(yōu)勢,有效緩沖過渡金屬氧化物在充放電過程中的體積膨脹,從而提高循環(huán)穩(wěn)定性。
[Abstract]:With the continuous development of new energy industry development, has long cycle stability, high reversible capacity, good safety performance and fast charging and discharging capacity of the energy storage material is the development trend of world energy demand, in line with China's national energy strategy, become the focus of attention of researchers. Kinami metal materials in the field of energy storage plays an important role, especially in the application of lithium ion battery anode material, the microstructure determines its lithium storage performance. Facing common problems is the volume cycle changes, the capacity of serious decay, especially transition metal oxide materials have low electronic conductivity. Carbon materials with high electronic conductivity structure, controllable morphology, surface the chemical properties of adjustable and environmentally friendly, carbon materials and metal based nano composite materials can effectively improve the performance of anode materials for lithium ion batteries. In this paper, high capacity anode The structure of the material design and synthesis as the goal, to improve the close contact of carbon materials and active components, combined with nitrogen doped porous structure and the creation of new and effective methods, development of three kinds of carbon coated anode materials, construct a series of novel structured carbon coated nano composite material and its application in lithium ion the battery shows high reversible capacity, cycle stability and rate performance. On this basis, influence the structural characteristics of the system of carbon coated nano composite material on its electrochemical performance. Specifically including the following aspects: (1) to two yuan of nano metal oxide (ZnSnO_3) and 2- methyl imidazole as the precursor target to the growth of metal organic frameworks ZIF-8 prepared N-doped carbon coated three-dimensional continuous high content (82.3 wt%) nano tin material. According to the HSAB theory, 2- methyl imidazole as base junction priority and border acid (2+) combined with Zn~ Generation of ZIF-8 coating, the highly dispersed tin oxide is introduced into the ZIF-8 network. The subsequent pyrolysis ZIF-8 change rich nitrogen (5.3wt%) high conductive carbon coated connected network, at the same time, reduction of carbon oxides for Sn Hot Tin nanoparticles, the reduction of the low boiling point Zn volatilization in subsequent pyrolysis process the pore structure and generate rich and open, efficient transport of ions and electrons. Lithium ion battery test results show that the Sn/C composite materials in 0.2 A g~ (-1) current density discharge capacity of 1321mAhg~ (-1), Kulun's efficiency is as high as 80.1%. in 0.2 and 1Ag~ (-1) respectively under 150 cycles after the reversible capacity can maintain for 901 and 690 mA hg~ (-1). In addition, this method can also be extended to the synthesis of nitrogen doped carbon coated manganese oxide composite material, also exhibited excellent electrochemical performance. (2) starting from the raw material, the use of wood fungi The unique ear swelling characteristics and multicellular grid structure for adsorption of Mn~ (2+) solution to build a three-dimensional net structure of nano MnO@C highly cross-linked. Rich in hydroxyl groups of main components of fungus cell wall chitin, the complexation of metal ions and MnO nanoparticles in situ and immobilized on carbon nano sheet connected in, effectively prevent the nanoparticles from agglomeration. In addition of chitin in the cell wall of the fungus in the subsequent drying shrinkage and pyrolysis can be transformed into continuous nitrogen doped carbon conductive coating layer, improve the conductivity and stability of composite structure. The nano network structure can not only reduce the ion diffusion path, can effectively buffer the volume change in MnO the charge and discharge process. The electrochemical test results show that the MnO@C composite material of this synthesis method in 0.2 A g~ (-1) at a current density of 300 cycles can be The inverse capacity of 868 mAh g~ (-1), 1 A g~ (-1) 500 cycles the reversible capacity of 668 mAh g~ (-1), has proved its high reversible capacity and excellent cycle stability. In addition, the sustainable green synthesis method is easy to scale and high performance nano network node design the synthesis structure provides a new way of thinking. (3) by using the method of domain limit weak oxidizing atmosphere pyrolysis of transition metal carbonate crystal polydopamine coated in self generated structure in carbon coated mesoporous transition metal oxides micro nano structure. Polydopamine coated with MnCO_3 crystal as an example, the pyrolysis coating layer for an external change conductive carbon shell, and MnCO_3 crystal nano MnO. burst in-situ ultra small CO_2 gas pressure in its generation under the impetus of CO_2 not only as a pore forming agent in mesoporous material to produce from the inside through the cladding and carbon in shape A rich micropores, a weak oxidizing atmosphere which can also transition metal oxides, reducing atmosphere and effective poly dopamine producing in the process of pyrolysis, prevent metal phase formation. Were prepared with mesoporous nano structured carbon coated manganese oxide by using this method, cobalt oxide and iron oxide.MnO@C composite at 0.2 and 2 A g~ (-1) current density respectively 200 and 300 times circulation reversible capacity as high as 886 and 770 mA h g~ (-1), carbon coated cobalt oxide and iron oxide materials in 0.2 A g~ (-1) current density under the reversible capacity is respectively 1058 and 770mAhg~ (-1). At the same time has a good cycle stability. This method can also achieve the carbon coated core-shell structure, mesoporous structure and micro nano structure through a multi-level structure of advantage, effectively buffer the transition metal oxide in the process of charging and discharging volume expansion, thereby improving High cycle stability.

【學(xué)位授予單位】：大連理工大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2017
【分類號(hào)】：TM912;TB383.1

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本文編號(hào)：1601555