本文選題：石墨烯　切入點：硫化鎳　出處：《浙江大學(xué)》2014年碩士論文

【摘要】：石墨烯是一種碳原子以sp2雜化軌道呈蜂巢晶格排列構(gòu)成的單層二維材料,具有優(yōu)異的電學(xué)、力學(xué)以及熱學(xué)性能,是與電化學(xué)活性物質(zhì)復(fù)合的理想基體,在鋰(鈉)離子電池電極材料上具有良好的應(yīng)用前景。本文通過水(溶劑)熱法,制備石墨烯基負(fù)極、正極復(fù)合材料,詳細(xì)研究了石墨烯的引入對材料微觀結(jié)構(gòu)的影響,復(fù)合材料微觀結(jié)構(gòu)與電化學(xué)性能之間的關(guān)系,并探索了石墨烯在改善正、負(fù)極材料儲鋰(鈉)性能上的作用機(jī)理。 電極材料的微觀結(jié)構(gòu)對其性能有很大影響,利用石墨烯(G)可以獲得具有特殊微觀形貌的電極材料。本文采用一步水熱法制備了超薄NiS/G二維復(fù)合材料,并詳細(xì)分析了其生長機(jī)理。相對于單純NiS展現(xiàn)出的由納米棒團(tuán)聚而成的納米花形結(jié)構(gòu),NiS/G復(fù)合材料展現(xiàn)出獨特的片-片復(fù)合二維層狀結(jié)構(gòu),NiS片層厚度小于5nm,石墨烯層數(shù)小于8層。研究發(fā)現(xiàn),在水熱反應(yīng)過程中,石墨烯表面的含氧殘基與NiS納米棒表面的含硫殘基形成新的共價鍵,將NiS納米棒逐步剝離成納米片,形成新型超薄二維復(fù)合材料。 本文研究了NiS/G復(fù)合物作為負(fù)極材料在鋰離子及鈉離子電池上的應(yīng)用。研究表明,在儲鋰方面,NiS/G復(fù)合物在50mA/g充放電流密度下,經(jīng)過100次循環(huán)依然保持481mAh/g的可逆容量,高達(dá)其理論容量(約500mAh/g)的96.2%；而單純NiS在10次循環(huán)后容量迅速衰減為140mAh/g。在儲鈉方面,NiS/G復(fù)合物在400mA/g的充電流密度下經(jīng)過10次循環(huán)后,容量保持在150mAh/g以上,而單純NiS則不到80mAh/g。在負(fù)極復(fù)合材料中,石墨烯不僅可以緩沖充放電過程中的體積效應(yīng),還能形成導(dǎo)電網(wǎng)絡(luò)提升導(dǎo)電性,并且在長時間循環(huán)過程中保持材料良好的分散性,從而顯著提高材料的循環(huán)穩(wěn)定性及倍率性能。 本文采用溶劑熱法合成了LiFePO4/G復(fù)合材料。研究發(fā)現(xiàn),LiFePO4顆粒均勻地鑲嵌在石墨烯片層上,尺寸在100nm以下。在5C電流密度下,LiFePO/G復(fù)合材料的可逆容量高達(dá)105mAh/g,而單純LiFePO4僅有65mAh/g的容量。在正極復(fù)合材料中,石墨烯形成的柔性三維連續(xù)導(dǎo)電網(wǎng)絡(luò)不僅彌補(bǔ)了LiFePO4導(dǎo)電性較差的不足,并且改善了電極材料與電解液的浸潤性,使得復(fù)合材料表現(xiàn)出良好的大電流倍率性能。
[Abstract]:Graphene is a carbon atom with SP2 hybrid orbital honeycomb lattice of two-dimensional monolayer material formed, with excellent electrical, mechanical and thermal properties, is an ideal substrate composite and electrochemical active material, lithium (sodium) has a good application prospect of electrode material ion battery. The heat water (solvent) method for preparing graphene based anode, cathode material, a detailed study of the introduction of graphene on the microstructure of the materials, the relationship between the microstructure and electrochemical properties of composite materials, and explored the graphene in improving, anode materials for lithium storage (NA) mechanism performance.
The microstructure of the electrode material has great influence on its performance, the use of graphene (G) can obtain the electrode materials with special morphology. The two-dimensional ultrathin NiS/G composites were prepared by one-step hydrothermal method, and a detailed analysis of the growth mechanism. Compared with the pure NiS nano show by nanorods and agglomeration the flower shaped structure, NiS/G composite materials show a unique piece of film composite two-dimensional layered structure, NiS layer thickness is less than 5nm, less than 8 layers of graphene. The study found that during the hydrothermal process, the graphene surface oxygen containing residues and NiS nanorod surface sulfur residues forming a new covalent bond the NiS nanorods gradually stripped into nanosheets, forming new ultra-thin two-dimensional composite materials.
This paper studies the NiS/G compounds were used as anode materials in lithium ion and sodium ion batteries. Research shows that in the lithium storage, NiS/G complex on current density at 50mA/g, after 100 cycles still maintain a reversible capacity of 481mAh/g, up to its theoretical capacity (about 500mAh/g) and only 96.2%; at NiS after 10 cycles the rapid decay of the capacity for 140mAh/g. in sodium storage, NiS/G complexes in the 400mA/g charging current density after 10 cycles, the capacity retention was more than 150mAh/g, but the NiS is less than 80mAh/g. in the anode composite material, graphene can not only buffer the volume effect of the charge and discharge process. Can enhance the conductivity of conductive network formation, and maintain a good dispersion of materials in long time cycle, so as to improve the performance of the cycle stability and rate of the material.
In this paper, LiFePO4/G composite materials were prepared by solvothermal method. The study found that LiFePO4 particles embedded in the graphene layers, size below 100nm. In the current density of 5C, the reversible capacity of LiFePO/G composites reached 105mAh/g, while the capacity of pure LiFePO4 65mAh/g. Only in anode composite materials, graphene the formation of flexible three-dimensional continuous conductive network not only overcomes the shortcoming of LiFePO4 poor conductivity, and improve the wettability of the electrode and the electrolyte, the composites exhibit a high current ratio of good performance.

【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】：2014
【分類號】：TM912

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本文編號：1701843