發(fā)布時(shí)間：2018-06-04 03:00

  本文選題：溶劑熱法 + 四氧化三鐵��； 參考：《蘭州大學(xué)》2014年碩士論文

【摘要】：近年來(lái),隨著科學(xué)技術(shù)的不斷進(jìn)步,人們對(duì)能源的需求也越來(lái)越大。鋰離子電池作為一種常用的便攜式儲(chǔ)能設(shè)備,受到越來(lái)越多的關(guān)注。如何提高鋰離子電池的循環(huán)穩(wěn)定性、電容量和效率,是當(dāng)前研究面臨的主要問(wèn)題。四氧化三鐵由于具有較高的理論電容量、低成本和環(huán)境友好等特點(diǎn),已經(jīng)開始被應(yīng)用于鋰離子電池負(fù)極材料。石墨烯以及基于石墨烯的復(fù)合材料,被認(rèn)為是作為鋰離子電池的電極的不二選擇。因?yàn)檫@類材料具有很好的導(dǎo)電性,大的比表面積,耐腐蝕性,高透明度和較寬的電化學(xué)窗口等優(yōu)點(diǎn)。 本論文主要采用溶劑熱法制備了實(shí)心和空心四氧化三鐵微球,并對(duì)分別對(duì)其結(jié)構(gòu)、形貌和磁性能進(jìn)行了研究。同時(shí)還討論了反應(yīng)時(shí)間以及尿素含量對(duì)其結(jié)構(gòu)和磁性能的影響。在此基礎(chǔ)上,采用了三種不同的方法,將四氧化三鐵與石墨烯進(jìn)行了復(fù)合,并對(duì)其鋰電性能進(jìn)行了研究。 主要的研究?jī)?nèi)容和成果如下：(1)在不需要任何模板的前提下,通過(guò)溶劑熱法,可以制備出具有空心結(jié)構(gòu)的四氧化三鐵微球。實(shí)驗(yàn)表明,顆粒的粒徑在400nm左右,內(nèi)徑尺寸約為230nm,具有很好的分散性和表面形貌。VSM測(cè)試表明,所制備的空心微球具有室溫亞鐵磁性,其飽和磁化強(qiáng)度接近于塊體材料。(2)不同的反應(yīng)時(shí)間對(duì)四氧化三鐵空心結(jié)構(gòu)的形成有著重要的影響。隨著反應(yīng)時(shí)間的增長(zhǎng),顆粒逐漸形成空心結(jié)構(gòu)。當(dāng)反應(yīng)時(shí)間為8小時(shí)時(shí),四氧化三鐵為實(shí)心微球；當(dāng)反應(yīng)時(shí)間增加到20小時(shí)時(shí),便形成了空心結(jié)構(gòu)。(3)尿素含量會(huì)影響四氧化三鐵微球的形貌。尿素含量為1.0g時(shí),顆粒尺寸約為800nm；隨著含量的增加,顆粒尺寸開始減小,但是,其形貌的不規(guī)則也愈發(fā)嚴(yán)重。當(dāng)尿素含量為2.0g時(shí),具有最佳形貌。由此我們總結(jié)出制備空心四氧化三鐵微球的最佳條件是反應(yīng)時(shí)間20小時(shí),尿素含量2.0g。(4)通過(guò)對(duì)實(shí)心四氧化三鐵微球和空心四氧化三鐵微球的微波吸收能力的研究發(fā)現(xiàn),空心結(jié)構(gòu)的確可以提高對(duì)微波的吸收能力。空心Fe304微球的最小反射吸收在5.7GHz處可達(dá)-42.6dB,遠(yuǎn)高于實(shí)心Fe304微球的-29.1dB (3.2GHz處)。同時(shí),其反射損耗小于-18dB的吸波寬度為6.6GHz,也大于實(shí)心微球的4.8GHz。 (5)我們采用石墨烯直接包覆制備好的四氧化三鐵顆粒(實(shí)心和空心)的方法制備了Fe304/石墨烯的復(fù)合材料。實(shí)驗(yàn)表明：采用這種辦法,四氧化三鐵顆�？梢院芎玫谋３制湓行蚊�,同時(shí)石墨烯有更好的還原效果,其鋰電性能也得到了提高。 (6)同時(shí)還發(fā)現(xiàn),用KH550對(duì)四氧化三鐵表面進(jìn)行修飾,然后用石墨烯對(duì)修飾后的四氧化三鐵顆粒進(jìn)行二次包覆,顆粒的分散性得到了改善,此外還可以增強(qiáng)顆粒與石墨烯的結(jié)合,進(jìn)而增加對(duì)四氧化三鐵顆粒的保護(hù)能力,提高電容量和穩(wěn)定性。修飾后的空心微球與未經(jīng)修飾的相比,其50次循環(huán)后的放電電容量提高了15%,更為重要的是其穩(wěn)定性也有了大幅提高。
[Abstract]:In recent years, with the continuous progress of science and technology, the demand for energy is also increasing. As a portable energy storage device, lithium ion battery has attracted more and more attention. How to improve the cycle stability, capacitance and efficiency of lithium-ion battery is the main problem. Due to its high theoretical capacity, low cost and environmental friendliness, iron trioxide has been used as anode material for lithium ion batteries. Graphene and graphene-based composites are considered to be the best electrode for lithium-ion batteries. Because of its good conductivity, large specific surface area, corrosion resistance, high transparency and wide electrochemical window. In this paper, solid and hollow iron trioxide microspheres were prepared by solvothermal method, and their structure, morphology and magnetic properties were studied. The effects of reaction time and urea content on the structure and magnetic properties were also discussed. On this basis, three different methods were used to compound iron trioxide with graphene, and the lithium electrical properties were studied. The main research contents and results are as follows: (1) without any template, iron trioxide microspheres with hollow structure can be prepared by solvothermal method. The results show that the particle size is about 400nm and the inner diameter is about 230 nm. The hollow microspheres prepared have ferromagnetic properties at room temperature due to their good dispersion and surface morphology. The saturation magnetization is close to that of bulk material. The different reaction time has an important effect on the formation of iron trioxide hollow structure. With the increase of reaction time, the particles gradually formed hollow structure. When the reaction time was 8 hours, Fe _ 2O _ 3 was a solid microsphere, and when the reaction time was increased to 20 hours, the hollow structure was formed. The urea content would affect the morphology of Fe _ 2O _ 3 microspheres. When the urea content is 1.0 g, the particle size is about 800 nm, and with the increase of urea content, the particle size begins to decrease, but the irregular morphology becomes more and more serious. When urea content is 2.0 g, the optimum morphology is obtained. The optimum conditions for the preparation of hollow iron trioxide microspheres were as follows: reaction time 20 hours, urea content 2.0 g 路L ~ (4). The microwave absorption capacity of solid iron trioxide microspheres and hollow iron trioxide microspheres was studied. The hollow structure can improve the absorption ability of microwave. The minimum reflectance absorption of hollow Fe304 microspheres can reach -42.6 dB at 5.7GHz, which is much higher than that at -29.1dB / 3.2GHz for solid Fe304 microspheres. At the same time, the absorption width with reflection loss less than -18dB is 6.6 GHz, which is also larger than that of solid microsphere (4.8 GHz). 5) Fe304/ graphene composites were prepared by direct coating of graphene with iron trioxide particles (solid and hollow). The experimental results show that the Fe _ 2O _ 4 particles can maintain their original morphology, and graphene has a better reduction effect, and its lithium electrical properties are also improved. At the same time, it was found that the surface of Fe _ 2O _ 3 was modified by KH550, and then the modified Fe _ 2O _ 3 particles were twice coated with graphene, the dispersion of the particles was improved, and the combination of the particles with graphene was also enhanced. Furthermore, the capacity and stability of Fe _ 2O _ 3 particles were improved. Compared with the unmodified hollow microspheres, the discharge capacity of the modified hollow microspheres increased by 15% after 50 cycles, and more importantly, the stability of the modified hollow microspheres was greatly improved.
【學(xué)位授予單位】：蘭州大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2014
【分類號(hào)】：TM912

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相關(guān)期刊論文 前2條

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本文編號(hào)：1975554