發(fā)布時間：2018-05-17 06:04

  本文選題：鋰硫電池 + 炭氣凝膠��； 參考：《合肥工業(yè)大學》2017年碩士論文

【摘要】：單質(zhì)硫作為鋰硫電池的電極材料具有很高的理論容量(1675 mAh·g-1)和能量密度(2600 Wh·kg-1),并且資源豐富、價廉、無毒等優(yōu)勢,鋰硫電池成了廣泛關(guān)注的熱點。但硫單質(zhì)本質(zhì)屬性也給鋰硫電池的發(fā)展帶來一些挑戰(zhàn)。比如單質(zhì)硫的絕緣性,多硫離子中間產(chǎn)物的溶解性導致的穿梭效應等問題。為了解決相關(guān)問題,從碳材料的制備入手,形成特定的同軸電纜結(jié)構(gòu)的炭氣凝膠(CNCA),采用鉬氧化物和鉬硫化物的原位摻雜進行材料改性。在此基礎上采用與硫單質(zhì)復合形成鋰硫電池的正極。論文工作中采用X射線衍分析,X射線電子能譜分析,場發(fā)射掃描電鏡分析,場發(fā)射透射電鏡分析,氮氣吸脫附分析等多種現(xiàn)代結(jié)構(gòu)分析方法,對材料的組成、形貌、元素價態(tài)、孔結(jié)構(gòu)、吸附能力等進行測試和表征,獲得材料結(jié)構(gòu)特征和豐富信息。同時采用恒流充放電、循環(huán)伏安和交流阻抗等電化學方法進行測試,獲得的碳硫及其摻雜材料電化學性能。結(jié)合對材料結(jié)構(gòu)表征和電化學測試,對碳硫復合材料的結(jié)構(gòu)與電化學性能間的關(guān)系進行了深入的研究�；谔技{米管(CNT)引導所制備的炭氣凝膠,具有互連特征,呈現(xiàn)出同軸電纜3維網(wǎng)狀結(jié)構(gòu)。金屬鉬化物摻雜的炭氣凝膠具有優(yōu)良的導電性、較高的比表面積和孔容,同時呈現(xiàn)出對硫和多硫化物的有效的固定和吸附作用,可以抑制多硫化物溶解于電解液,有效提高電極材料的循環(huán)壽命。結(jié)果研究表明,所制得的同軸電纜結(jié)構(gòu)的炭氣凝膠作為鋰硫電池的正極,具有良好的電化學性能,不僅具有較高的初始容量,而且具有優(yōu)異的循環(huán)性能和優(yōu)良的倍率性能,同時呈現(xiàn)低的阻抗值。MoS2修飾的同軸電纜3維網(wǎng)狀結(jié)構(gòu)炭氣凝膠(MoS2-n/CNCA)對多硫化物具有良好的錨牽作用,再加上較高的比表面積、孔容量和導電性能,作為電極材料具有良好的循環(huán)穩(wěn)定性、較高的放電容量、優(yōu)異的高倍率性能。其中MoS2-8/CNCA/S的在0.2C條件下初始放電容量為1384mAh·g-1,200圈后的容量保持率為83%;在5C條件下的放電容量也高達723 mAh·g-1。以MoO2納米顆粒均勻的鑲嵌在具有同軸電纜3維網(wǎng)狀結(jié)構(gòu)碳材料的管殼上制得的MOO2-n/CNCA,具有良好的導電性能和對多硫化物的牽引作用,使MOO2-n/CNCA/S電極材料具有良好的電化學性能,其中M0O2-6/CNCA/S在0.2C條件下初始放電容量為1308 mAh·g-1,200圈后的容量保持率為80%;在5C條件下的放電容量也高達為686 mAh·g-1;以此表現(xiàn)出優(yōu)異的電化學性能。
[Abstract]:As the electrode material of lithium sulfur battery with high theoretical capacity (1675 mAh g-1) and energy density of 2600 Wh 路kg -1, simple sulfur has many advantages, such as abundant resources, low price and non-toxicity, so the lithium sulfur battery has become the focus of attention. However, the essential properties of sulfur also bring some challenges to the development of lithium-sulfur batteries. Such as the insulation of elemental sulfur, the solubility of polysulfide intermediate products caused by the shuttle effect and so on. In order to solve the related problems, the carbon aerogel CNCA (carbon aerogel) with specific coaxial cable structure was formed from the preparation of carbon materials and modified by in-situ doping of molybdenum oxides and molybdenum sulfides. On this basis, the lithium-sulfur battery cathode was formed by combining with sulfur. In this paper, X-ray diffraction analysis, field emission scanning electron microscopy, field emission transmission electron microscopy, nitrogen absorption and desorption analysis were used to analyze the composition, morphology and valence of elements. The pore structure and adsorption capacity were measured and characterized to obtain the material structure characteristics and abundant information. At the same time, constant current charge and discharge, cyclic voltammetry and AC impedance were used to test the electrochemical properties of carbon and sulfur and their doped materials. The relationship between the structure and electrochemical properties of carbon and sulfur composites was studied by means of structural characterization and electrochemical test. Carbon aerogels based on carbon nanotube (CNT) guidance have interconnect characteristics and present a three dimensional network structure of coaxial cable. Carbon aerogels doped with molybdenum metal have excellent conductivity, high specific surface area and pore volume, and exhibit effective fixation and adsorption to sulfur and polysulfide, which can inhibit the dissolution of polysulfide in electrolyte. Effectively improve the cycle life of electrode materials. The results show that the carbon aerogel with coaxial cable structure has good electrochemical performance, not only has high initial capacity, but also has excellent cycling performance and excellent rate performance as the cathode of lithium-sulfur battery. At the same time, MoS2 modified coaxial cable with low impedance value. MoS2 modified carbon aerogel MoS2-n / CNCA has good anchoring effect on polysulfide, plus high specific surface area, pore capacity and conductivity. As an electrode material, it has good cycling stability, high discharge capacity and excellent performance of high rate. The initial discharge capacity of MoS2-8/CNCA/S is 83 after 1384mAh g-1200 cycles at 0.2C, and the discharge capacity at 5C is as high as 723 mAh g-1. MOO2-n / CNCA, which is made of MoO2 nanoparticles uniformly embedded on the tube and shell of carbon material with three dimensional network structure of coaxial cable, has good electrical conductivity and traction to polysulfide, which makes the MOO2-n/CNCA/S electrode material have good electrochemical performance. The initial discharge capacity of M0O2-6/CNCA/S at 0.2C was 1308 mAh g-1200 cycles and the discharge capacity at 5C was as high as 686 mAh g-1, which showed excellent electrochemical performance.
【學位授予單位】：合肥工業(yè)大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TQ427.26;TM912

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本文編號：1900212