本文選題：過渡金屬硫化物 + 過渡金屬氧化物�。� 參考：《東北師范大學(xué)》2017年碩士論文

【摘要】：作為新型儲能設(shè)備,鋰離子電池的研制備受關(guān)注,成為各國研究者的研究熱點。為了滿足社會發(fā)展的需要,鋰離子電池應(yīng)具有高的容量,長的循環(huán)壽命,良好的倍率性能。然而,在商業(yè)化負極材料中占主要地位的石墨,比容量低(372mAh g-1),遠遠不能滿足社會需求。因此,開發(fā)容量高,循環(huán)穩(wěn)定好,倍率性能優(yōu)異的負極材料迫在眉睫。迄今為止,研究者們已開發(fā)出各種各樣的負極材料,如合金類材料,碳材料,過渡金屬氧化物,過渡金屬硫化物等。其中過渡金屬氧化物和過渡金屬硫化物因其高的理論比容量備受研究者的青睞。MoS2作為典型的過渡金屬硫化物,具有類石墨烯的二維結(jié)構(gòu),其獨特的結(jié)構(gòu)使其具有優(yōu)異的電化學(xué)性能。但是MoS2導(dǎo)電性能差,在實際應(yīng)用過程中容易團聚。這些不足之處都限制著它的應(yīng)用。此外,過渡金屬氧化物(Co3O4)具有超高的理論比容量,幾乎是石墨的三倍,但是體積膨脹大,在充放電過程中,引起電極材料粉碎,導(dǎo)致容量迅速衰減是它的致命缺點。另外,Co3O4的導(dǎo)電性能差也是導(dǎo)致其性能不佳的主要因素。針對上述問題,有效的解決方案主要包括制備各種形貌的納米材料以及合成復(fù)合材料,從而提高材料的電化學(xué)性能。本文主要設(shè)計合成結(jié)構(gòu)新穎的MoS2和Co3O4,并成功使用碳材料對其進行修飾,通過兩者之間的協(xié)同作用,來提高材料的電化學(xué)性能。主要研究包括:(1)采用一步水熱高溫處理的方法合成微納結(jié)構(gòu)的MoS2/N-C復(fù)合材料。MoS2納米晶鑲嵌在多孔的氮摻雜的體相碳材料中,形成微納結(jié)構(gòu);使用生物材料蛋黃作為碳源,環(huán)境友好,成本低廉,合成過程簡單,可實現(xiàn)大規(guī)模生產(chǎn)。合成的復(fù)合物這種特殊的結(jié)構(gòu)抑制了MoS2在充放電過程中的團聚,納米化的MoS2暴露出更多的活性位點,碳材料的引入提高了材料的導(dǎo)電性。研究結(jié)果表明MoS2/N-C復(fù)合材料的倍率性能以及循環(huán)穩(wěn)定性遠高于純MoS2。當電流密度為100 mA g-1時,MoS2/N-C復(fù)合材料循環(huán)100圈之后其容量仍有805 mAh g-1,而純MoS2則不到100 mAg-1。在電流密度為500 mA g-1的高電流密度下循環(huán)500圈之后容量可高達630 mA h g-1,展現(xiàn)出優(yōu)異的循環(huán)性能。(2)采用一步水解鈷鹽高溫處理的方法合成Co3O4/rGO的復(fù)合材料。該材料的制備過程簡單,安全性能高。所得的Co3O4納米顆粒沉積在還原石墨烯片上,材料的比表面積大,活性材料尺寸小,與電解質(zhì)接觸的活性位點增多,與石墨烯形成復(fù)合材料,石墨烯具有特殊性質(zhì)可以緩解材料在循環(huán)過程中產(chǎn)生的體積膨脹,提高材料導(dǎo)電性,從而改善材料的電化學(xué)性能。研究結(jié)果表明Co3O4/rGO的復(fù)合材料相較于純Co3O4其循環(huán)穩(wěn)定性,倍率性能以及容量都得到了大幅度提高。電流密度為100 mA g-1時,Co3O4/rGO復(fù)合材料的首圈放電容量1217.3 mAh g-1,充電容量為805.6 mAh g-1,庫倫效率為66.2%,循環(huán)130圈之后容量維持在1095.1mAh g-1,性能遠遠優(yōu)于純Co3O4。
[Abstract]:As a new type of energy storage equipment, the development of lithium ion battery has attracted much attention. In order to meet the needs of social development, lithium ion batteries should have high capacity, long cycle life and good rate performance. However, graphite, which dominates the commercial anode materials, has a low specific capacity of 372mAh g-1, which is far from satisfying the social needs. Therefore, it is urgent to develop negative electrode materials with high capacity, good cycle stability and excellent rate performance. So far, researchers have developed a variety of negative electrode materials, such as alloy materials, carbon materials, transition metal oxides, transition metal sulfides and so on. Among them, transition metal oxides and transition metal sulphides are favored by researchers because of their high theoretical specific capacity. As typical transition metal sulphides, the transition metal oxides and transition metal sulphides have the two-dimensional structure of graphene. Its unique structure makes it have excellent electrochemical performance. But MoS2 has poor conductivity and is easy to agglomerate in practical application. These shortcomings limit its application. In addition, the transition metal oxide (Co _ 3O _ 4) has a high theoretical specific capacity, almost three times of that of graphite, but it has a fatal disadvantage of large volume expansion, which causes the electrode material to crush and lead to rapid capacity decay during charging and discharging. In addition, the poor conductivity of Co 3 O 4 is also the main factor leading to its poor performance. To solve the above problems, the effective solutions include the preparation of nano-materials with various morphologies and the synthesis of composite materials, so as to improve the electrochemical properties of the materials. In this paper, MoS2 and Co _ 3O _ 4 with novel structures were designed and synthesized, and the carbon materials were successfully modified to improve the electrochemical properties of the materials by synergistic action between them. The main research contents include: (1) Synthesis of MoS _ 2 / N _ C composite with micro-nano structure by one-step hydrothermal high-temperature treatment. MoS _ 2 nanocrystalline is embedded in porous nitrogen-doped bulk carbon material to form micro-nano structure; egg yolk is used as carbon source. Environmental friendly, low cost, simple synthesis process, can achieve mass production. The special structure of the synthesized complex inhibits the aggregation of MoS2 during charge and discharge. The nano-MoS2 exposes more active sites and the introduction of carbon materials improves the conductivity of the materials. The results show that the ratio properties and cyclic stability of MoS _ 2 / N-C composites are much higher than those of pure MoS _ 2 / N-C composites. When the current density is 100mAg ~ (-1), the capacity of MoS _ 2 / N-C composite is still 805 mAh g ~ (-1) and less than 100mAg-1 for pure MoS _ 2 / N-C composite material. At a high current density of 500mAg ~ (-1), the capacity of Co _ 3O _ 4 / rGO composites can be as high as 630mA 路h ~ (-1) after 500 cycles, showing excellent cycling performance.) Co _ 3O _ 4 / rGO composites were synthesized by one-step hydrolysis of cobalt salt at high temperature. The preparation process of the material is simple and the safety performance is high. The resulting Co _ 3O _ 4 nanoparticles were deposited on the reduced graphene sheet with large specific surface area, small active material size, increased active sites in contact with electrolyte, and formed a composite material with graphene. Graphene has special properties which can alleviate the volume expansion and improve the electrical conductivity of the materials during the cycle, thus improving the electrochemical properties of the materials. The results show that the cyclic stability of Co _ 3O _ 4 / rGO composite is much higher than that of pure Co _ 3O _ 4. When the current density is 100mAg ~ (-1), the first-loop discharge capacity is 1217.3 mAh g ~ (-1), the charge capacity is 805.6 mAh g ~ (-1), and the Coulomb efficiency is 66.2 when the current density is 100mAg ~ (-1). The capacity of the composite is maintained at 1095.1mAh g ~ (-1) after 130th cycle, which is much better than that of pure Co _ 3O _ 4.
【學(xué)位授予單位】：東北師范大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TB33;TM912

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本文編號：1999972