本文選題：鋰硫電池 + 硫-氧化石墨烯復(fù)合材料�。� 參考：《浙江大學(xué)》2015年碩士論文

【摘要】：鋰硫電池被認(rèn)為極有可能替代傳統(tǒng)鋰離子電池成為下一代被廣泛應(yīng)用的電池體系。為了解決鋰硫電池存在的問題,研究者們提出了許多改進(jìn)的方案,包括對(duì)正極材料的結(jié)構(gòu)設(shè)計(jì)與性能優(yōu)化等。其中,yolk-shell型復(fù)合材料制備作為一種很好的解決方案受到研究者們的關(guān)注,一些研究者合成了yolk-shell型TiO2-S或yolk-shell型聚合物-S等復(fù)合材料,用作鋰硫電池正極材料。yolk-shell型結(jié)構(gòu)由于殼層及空隙的存在,能夠使內(nèi)部的材料得到很好的保護(hù)作用。yolk-shell型鋰硫電池復(fù)合正極材料通常的制備方法是,包覆硫之后通過將內(nèi)部的硫部分溶出或者加熱促使殼層內(nèi)部產(chǎn)生空隙。這類方法需要將硫部分溶解或反應(yīng),容易破壞材料完整性,不利于對(duì)硫單質(zhì)的保護(hù),并且過程復(fù)雜,不易控制。本課題擬采用具有凹陷結(jié)構(gòu)的硫顆粒,包裹氧化石墨烯后直接獲得具有內(nèi)部空隙的yolk-shell型S-GO復(fù)合材料。本文采用濕化學(xué)方法合成單質(zhì)硫顆粒,研究了硫單質(zhì)制備過程中工藝條件對(duì)所制得的硫顆粒的形貌產(chǎn)生的影響,實(shí)現(xiàn)了對(duì)硫顆粒形貌的調(diào)控,并最終獲得了具有明顯凹陷結(jié)構(gòu)的均勻亞微米硫球。選取氧化石墨烯(GO)作為包覆材料,通過控制溶液的離子強(qiáng)度,在室溫下完成了GO對(duì)硫單質(zhì)的包覆,復(fù)合材料具有良好的電化學(xué)性能。具體研究?jī)?nèi)容及結(jié)果如下：(1)通過改變表面活性劑PVP的添加量,可以得到不同形貌的硫顆粒。PVP可以使合成的硫顆粒尺寸趨于均勻,隨著PVP的增多,硫顆粒的表面會(huì)出現(xiàn)凹陷的結(jié)構(gòu),在一定范圍內(nèi)凹陷程度隨PVP的增多而增大。反應(yīng)成功制備出粒徑500nm左右具有凹陷結(jié)構(gòu)的均勻硫球。(2)反應(yīng)物濃度、PVP的分子量、反應(yīng)溫度、鹽酸的用量和酸的種類等條件的改變都會(huì)影響到硫顆粒的形貌。獲得具有凹陷結(jié)構(gòu)的硫球的具體實(shí)驗(yàn)條件為：在30℃以下,向100ml的0.04M的Na2S2O3溶液中,加入0.2g表面活性劑PVP,磁力攪拌下滴加0.67ml濃鹽酸反應(yīng)2小時(shí),抽濾并洗滌。(3)GO包覆具有凹陷結(jié)構(gòu)的硫球后直接形成yolk-shell型復(fù)合材料,材料在0.2A/g的電流密度下的首次放電比容量為575.98mAh/g,含有較多氧化石墨烯的樣品在1A/g的大電流下循環(huán)100次后容量保留了61.9%,總體表現(xiàn)出了較好的倍率性能和循環(huán)穩(wěn)定性。
[Abstract]:Lithium-sulfur battery is considered to be a promising alternative to the traditional lithium ion battery as the next generation of widely used battery systems. In order to solve the problems of lithium-sulfur batteries, researchers have proposed many improved schemes, including the structure design and performance optimization of cathode materials. Among them, the fabrication of yolk-shell composites as a good solution has attracted the attention of researchers. Some researchers have synthesized yolk-shell type TiO2-S or yolk-shell type polymer-S composites. The yolk-shell structure used as cathode material for lithium-sulfur batteries can be used to protect the inner materials well due to the existence of shells and voids. The usual preparation methods of the composite cathode materials for lithium-sulfur batteries are: After covering the sulfur, the inner sulfur part is dissolved or heated to cause the void in the shell. This kind of method needs to dissolve or react part of sulfur, it is easy to destroy the integrity of the material, is not conducive to the protection of sulfur, and the process is complex and difficult to control. In this paper, yolk-shell type S-GO composites with internal voids are obtained by using sulfur particles with hollow structure and encapsulating graphene oxide. In this paper, simple sulfur particles were synthesized by wet chemical method. The influence of technological conditions on the morphology of sulfur particles was studied, and the morphology of sulfur particles was regulated. Finally, a uniform submicron sulfur ball with obvious concave structure was obtained. By controlling the ionic strength of the solution, go was used as the coating material to coat the sulfur elements at room temperature. The composite has good electrochemical properties. The specific research contents and results are as follows: (1) by changing the amount of surfactant PVP, we can obtain different morphologies of sulfur particles. PVP can make the size of synthesized sulfur particles more uniform, and with the increase of PVP, The concave structure of sulfur particles will appear on the surface, and the degree of depression increases with the increase of PVP in a certain range. The molecular weight, reaction temperature, the amount of hydrochloric acid and the type of acid can affect the morphology of sulfur particles. The experimental conditions are as follows: below 30 鈩，

本文編號(hào)：1972327