本文選題：鋰硫電池 + 隔膜改性��； 參考：《江蘇大學(xué)》2017年碩士論文

【摘要】：從1990年開始,鋰電池就成為了主流電子產(chǎn)品的電源。但是隨著市場對電子產(chǎn)品續(xù)航能力要求的提高以及環(huán)境問題導(dǎo)致的電動(dòng)汽車研究熱潮,眾多學(xué)者開始研究更高能量密度的電池體系。因此以硫?yàn)檎龢O,鋰為負(fù)極的高能量密度的鋰硫電池(2600 Wh kg-1)開始成為研究熱點(diǎn)。但是鋰硫電池(Li-S電池)體系自身的缺陷使其商業(yè)化進(jìn)程受到了極大的限制。其中包括硫和硫的放電終產(chǎn)物的低離子/電子電導(dǎo),充放電過程中活性物質(zhì)嚴(yán)重的體積膨脹/收縮,以及反應(yīng)中產(chǎn)物聚硫化鋰(LiPS)溶解于有機(jī)電解液并擴(kuò)散到負(fù)極形成的穿梭效應(yīng)。本文針對Li-S電池體系中由于LiPS的穿梭效應(yīng)引起的正極活性物質(zhì)利用率低,電池極化嚴(yán)重,循環(huán)穩(wěn)定性差的問題,研究隔膜改性對于鋰硫電池性能的提升。論文研究的主要內(nèi)容和研究成果包括:1)科琴黑改性鋰硫電池隔膜的研究。實(shí)驗(yàn)通過對比KB改性隔膜與商用隔膜的電池電化學(xué)性能,研究了KB涂層對電池電化學(xué)反應(yīng)過程的影響并探索其作用機(jī)理。研究發(fā)現(xiàn):KB涂層是一個(gè)由納米顆粒均勻堆疊而成一個(gè)疏松多孔的碳層;KB涂層疏松多孔的結(jié)構(gòu)能夠有效吸附多硫化物,抑制穿梭效應(yīng);KB涂層優(yōu)異的導(dǎo)電性能使得浸入涂層的“失活”硫化物能被“活化”再次參與反應(yīng);KB涂層作為一個(gè)二次集流體,促進(jìn)反應(yīng)中離子、電子的遷移。因此,KB改性隔膜的電池表現(xiàn)出較好的循環(huán)性能與倍率性能。此改性電池在0.1 C下能夠達(dá)到1318 mAh g-1的比容量。即便是在1 C下循環(huán)100圈以后,放電比容量也只是從946 mAh g-1降低到815 mAh g-1。此改性電池在2 C的倍率下放電比容量依然能夠保持在934 mAh g-1。而當(dāng)電流強(qiáng)度降到0.1 C時(shí),KB改性隔膜的電池與傳統(tǒng)隔膜的電池的可逆容量分別為1173 mAh g-1與605 mAh g-1。2)二氧化鈰改性鋰硫電池隔膜的研究。實(shí)驗(yàn)利用噴霧造粒法制備出中空的氧化鈰,并進(jìn)行隔膜的涂布改性。通過對比二氧化鈰改性隔膜與商用隔膜、Super-P改性隔膜的電池的電化學(xué)性能,研究了稀土金屬氧化物的摻雜對鋰硫電池電化學(xué)反應(yīng)過程的影響并探索其作用機(jī)理。研究發(fā)現(xiàn):CeO_2涂層不僅對LiPS起到了物理阻隔的作用,還有一定的化學(xué)吸附的作用;CeO_2涂層能夠催化浸入其中的多硫化物的還原反應(yīng),提升反應(yīng)動(dòng)力學(xué),降低電池極化;CeO_2涂層還能因?yàn)槠涮厥獾暮送怆娮优挪寄軌蛟贑e~(3+)與Ce~(4+)價(jià)之間自由轉(zhuǎn)化并且穩(wěn)定存在,增加浸入涂層的活性物質(zhì)的導(dǎo)電性。因此,二氧化鈰改性隔膜的電池具有更優(yōu)異的循環(huán)穩(wěn)定性。CeO_2改性隔膜的電池在1 C下的首次放電比容量達(dá)到1004 mAh g-1。即便循環(huán)500圈,放電比容量還能保持在625 mAh g-1。該電池在2 C的大倍率下充放電時(shí),比容量也能達(dá)到760 mAh g-1。而當(dāng)充放電倍率再次調(diào)整至0.5C時(shí),電池的可逆放電比容量能達(dá)到960 mAh g-1,與首次在0.5 C下充放電的970 mAh g-1幾乎一致。
[Abstract]:Lithium batteries have been the mainstay of electronics since 1990. However, with the increasing demand of the market for the ability of electronic products to live and the upsurge of research on electric vehicles caused by environmental problems, many scholars have begun to study battery systems with higher energy density. Therefore, the high energy density lithium-sulfur battery with sulfur as positive electrode and lithium as negative electrode has become a hot research topic. However, the commercial process of Li-S battery system has been greatly restricted due to its own defects. These include the low ion / electron conductance of the discharge end product of sulfur and sulfur, and the serious volume expansion / contraction of the active substance during the charge-discharge process. And the shuttle effect of poly-lithium-sulphide LiPSs dissolved in the organic electrolyte and diffused to the negative electrode. In order to solve the problems of low utilization of positive active substances, serious polarization and poor cycle stability caused by the shuttle effect of LiPS in Li-S battery system, the improvement of lithium-sulfur battery performance by membrane modification was studied in this paper. The main contents and results of this paper include: 1) study on the membrane of black modified lithium-sulfur battery. The effect of KB coating on the electrochemical reaction process of the battery was studied by comparing the electrochemical performance of the KB-modified membrane with the commercial membrane and the mechanism of its action was explored. It is found that the porous structure of a porous carbon layer formed by a homogeneous stacking of nano-particles can effectively adsorb polysulfides. The excellent conductivity of KB coating makes the "inactivated" sulfides immersed in the coating can be "activated" again to participate in the reaction of KB coating as a secondary collecting fluid, which can promote the ion and electron migration in the reaction. Therefore, the battery with modified membrane of KB showed better cycling performance and rate performance. The specific capacity of the modified battery can reach 1318 mAh g-1 at 0. 1 C. Even after 100 cycles at 1 C, the specific discharge capacity was reduced from 946 mAh g ~ (-1) to 815 mAh g ~ (-1). The specific discharge capacity of the modified battery can still be kept at 934 mAh g-1 at the rate of 2 C. However, when the current intensity is reduced to 0.1C, the reversible capacity of the modified membrane is 1173 mAh g-1 and 605 mAh g-1.2 respectively) the membrane of the lithium-sulfur cell modified by cerium oxide is 1173 mAh / g ~ (-1) and the reversible capacity of the conventional membrane is 1173 mAh / g ~ (-2) respectively. The hollow cerium oxide was prepared by spray granulation and modified by coating. The effects of rare earth metal oxide doping on the electrochemical reaction of lithium-sulfur batteries were studied by comparing the electrochemical performance of cerium oxide modified membrane and commercial super-P modified membrane. It is found that the CEO _ 2 coating not only acts as a physical barrier to LiPS, but also has a certain chemisorption effect. CeO _ 2 coating can catalyze the reduction reaction of polysulfide immersed in it and enhance the reaction kinetics. The reduction of the polarization of CEO _ 2 coating can also increase the conductivity of the active substances immersed in the coating because of the free conversion and stable existence of its special extranuclear electron arrangement between Ce~(3) and Ce~(4. Therefore, the battery with cerium oxide modified diaphragm has better cycle stability. The initial discharge specific capacity of the battery with CeO-2 modified diaphragm reaches 1004 mAh g-1 at 1 C. The specific discharge capacity can be kept at 625 mAh g-1 even if the cycle is 500 cycles. The specific capacity of the battery can also reach 760 mAh g-1 when charged and discharged at a large rate of 2 C. When the charge / discharge ratio is adjusted to 0.5 C again, the reversible discharge specific capacity of the battery can reach 960 mAh g-1, which is almost the same as that of 970 mAh g ~ (-1) charged and discharged at 0.5C for the first time.
【學(xué)位授予單位】：江蘇大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TM912;TB383.2

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