本文選題：FeS微米片陣列 + 微米球��； 參考：《浙江大學(xué)》2015年碩士論文

【摘要】：本文采用溶液法在鐵基底上原位生長出四方硫鐵礦型FeS微米片陣列和FeS微米球薄膜,并研究其電化學(xué)性能。利用單一變量法改變實(shí)驗(yàn)參數(shù),研究Fe3+離子濃度、硫源和溶劑對FeS形貌結(jié)構(gòu)的影響機(jī)制。通過對不同反應(yīng)時間下合成產(chǎn)物的形貌和結(jié)構(gòu)表征,探索FeS微米片陣列和FeS微米球的生長機(jī)制,并為其他金屬硫化物的合成提供參考。分別將FeS微米片陣列和FeS微米球組裝成鋰離子半電池,并測其電化學(xué)性能,分析不同結(jié)構(gòu)形貌對電極材料電化學(xué)性能的影響。另外,本文采用原位透射電子顯微鏡觀察分析方法,研究FeS在充放電過程中的形變和相變機(jī)理,進(jìn)一步分析形貌結(jié)構(gòu)對電極材料可逆性優(yōu)劣的影響。對于生長機(jī)理的研究中發(fā)現(xiàn),溶液中Fe3+濃度大小對FeS的形貌沒有影響,但是與片的密集程度有直接關(guān)系,Fe3+濃度越大,產(chǎn)物越密集；硫源種類對生長規(guī)則形貌和單一相產(chǎn)物具有關(guān)鍵作用,不同硫源釋放S2-的速率不同,從而影響晶體生長速度,S2-釋放速率越快,反應(yīng)越不可控,越容易產(chǎn)生雜質(zhì)相且形貌越不規(guī)則；乙二胺分子具有很強(qiáng)的協(xié)調(diào)能力和金屬螯合力,生成FeS·mEDA后可作為模板控制晶體的定向生長,阻止片狀自組裝,使最終形成FeS片狀陣列。故乙二胺是形成FeS片狀陣列的關(guān)鍵。FeS生長過程為在反應(yīng)初期,溶液中的Fe3+與鐵基底反應(yīng),在鐵基底表面形成Fe2+,然后與溶液中的S2-離子生成FeS在基底表面形核,晶核垂直基底生長成片狀FeS晶體。最終,在不同的實(shí)驗(yàn)條件下得到不同形貌的FeS薄膜。將FeS納米結(jié)構(gòu)薄膜作為鋰離子電池電極材料,并測其電化學(xué)性能。實(shí)驗(yàn)發(fā)現(xiàn)FeS微米片陣列電極表現(xiàn)出很好的儲鋰性能(首次放電容量為772 mAh g-1,循環(huán)20次后放電容量為697 mAh g-1),遠(yuǎn)遠(yuǎn)優(yōu)于FeS微米球電極的儲鋰性能,研究表明電極材料的儲鋰性能與其結(jié)構(gòu)形貌有關(guān)。FeS微米片陣列電極具有很好的電化學(xué)性能,原因有以下幾點(diǎn)：微米片結(jié)構(gòu)可以縮短Li+和電子的擴(kuò)散長度并且具有較大的比表面；FeS微米片陣列是片相互交叉形成的網(wǎng)狀結(jié)構(gòu),這種結(jié)構(gòu)存在大量的空間,可以有效緩沖Li+脫嵌過程中帶來的體積變化,抑制薄膜開裂和粉化；與傳統(tǒng)的鋰離子電池電極材料相比,在集流體上原位生長片狀陣列的電極材料的方法,可以為電極材料和集流體提供很好的電接觸和很強(qiáng)的結(jié)合力,這有利于電子和離子的傳輸,并大大簡化了電池組裝工藝。本文采用原位TEM分析方法,進(jìn)一步研究FeS在充放電過程中的形變和相變機(jī)理。結(jié)果顯示FeS納米片電極在電化學(xué)循環(huán)過程中能保持很好的結(jié)構(gòu)穩(wěn)定性。在首次鋰化過程中,體積僅為鋰化前的129%,形變很小。經(jīng)過三次循環(huán)后,納米片體積為初始體積的112.6%,說明納米片在電化學(xué)循環(huán)過程中形變量很小,且沒有發(fā)生開裂和粉化現(xiàn)象,這主要是由于納米片具有大的比表面和短的擴(kuò)散長度,使反應(yīng)均勻快速的進(jìn)行,并且很好的解釋了其循環(huán)穩(wěn)定性能好的原因。其次,FeS納米片電極在首次鋰化過程中的相變是不可逆的,首次完全鋰化后形成Li2S和Fe納米晶,Fe納米晶尺寸為2-3 nm,分散在Li2S中。首次完全退鋰化形成Li1.13FeS2單一相,之后的循環(huán)則為Li2S/Fe的混合相與Li1.13FeS2單一相之間的相互轉(zhuǎn)變。
[Abstract]:In this paper, a four square pyrite type FeS microchip array and a FeS microsphere film were grown on the iron base by solution method, and the electrochemical properties were studied. The influence mechanism of the Fe3+ ion concentration, the sulfur source and the solvent on the morphology of the FeS was studied by the single variable method. In appearance and structural characterization, the growth mechanism of FeS micron array and FeS microsphere is explored, and the reference for the synthesis of other metal sulfides is provided. The FeS micron array and FeS microspheres are assembled into lithium ion semi batteries, respectively, and their electrochemical properties are measured, and the effects of different structure morphology on the electrochemical properties of the electrode materials are analyzed. The deformation and phase transition mechanism of FeS during charge discharge were investigated by in-situ transmission electron microscopy, and the effect of morphology and structure on the reversibility of the electrode material was further analyzed. In the study of the growth mechanism, it was found that the concentration of Fe3+ in the solution had no effect on the morphology of FeS, but it was direct to the density of the film. The larger the concentration of Fe3+, the more dense the product is. The species of the sulfur source plays a key role in the growth rule and the single phase product. The rate of the release of S2- is different from the sulfur source, which affects the growth speed of the crystal. The faster the S2- release rate is, the more uncontrollable the reaction is, the more easily the hetero phase is produced and the more irregular the morphology is. The ethylenediamine molecule is very strong. Coordination ability and metal chelation force, after producing FeS. MEDA, can be used as a template to control the directional growth of crystal, prevent flaky self assembly, and eventually form a FeS sheet array. Therefore, ethylenediamine is the key.FeS growth process of forming a FeS flake array in the initial reaction, the reaction of Fe3+ in the solution with the iron substrate, and the formation of Fe2+ on the surface of the iron base, and then the.FeS The S2- ion in the solution generates FeS on the surface of the substrate, and the crystal nucleus grows into a slice like FeS crystal. Finally, the FeS thin films with different morphologies are obtained under different experimental conditions. The FeS nano structure film is used as the lithium ion battery electrode material and its electrochemical performance is measured. The experimental results show that the FeS micron array electrode has shown good performance. The lithium storage performance (the first discharge capacity is 772 mAh g-1, the discharge capacity is 697 mAh g-1 after 20 cycles), which is far superior to the FeS microsphere electrode's lithium storage performance. The study shows that the lithium storage properties of the electrode materials and their structure morphology related to the.FeS micron slice array electrode have good electrical properties. The reasons are the following several points: microchip structure can be used. It can shorten the diffusion length of Li+ and electrons and have a larger specific surface; FeS micron array is a network structure formed by intersecting pieces. This structure has a lot of space, which can effectively buffer the volume change brought by the process of Li+ deinterlay and inhibit the film cracking and pulverization. Compared with the traditional lithium ion battery electrode materials, The method of in situ growth of electrode materials in a flaky array can provide good electrical contact and strong binding force for the electrode material and the collection of fluids. This is beneficial to the transmission of electrons and ions and greatly simplifies the battery assembly process. In this paper, in situ TEM analysis method is used to further study the deformation and phase of FeS during the charge discharge process. The results show that the FeS nanoscale electrode can maintain a good structural stability during the electrochemical cycle. In the first lithium process, the volume is only 129% before lithium, and the deformation is very small. After three cycles, the volume of the nanoscale is 112.6% of the volume of the initial volume, indicating that the shape variables of the nanoscale are very small in the electrochemical cycle. The phenomenon of cracking and pulverization is mainly due to the large specific surface and short diffusion length of the nanoscale, which makes the reaction uniform and rapid, and explains well the reason for its good cycling stability. Secondly, the phase transition of the FeS nanoscale electrode in the first lithium process is irreversible, and the first complete lithium is Li2S and Fe after the first complete lithium-ion. Nanocrystalline, Fe nanocrystalline size is 2-3 nm, dispersed in Li2S. The first complete lithialization to form a single phase of Li1.13FeS2, and the subsequent cycle is the transformation between the Li2S/Fe mixture and the Li1.13FeS2 single phase.
【學(xué)位授予單位】：浙江大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TB383.2;TM912

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