本文選題：鋰離子電池 + 負極材料��； 參考：《湖南大學》2016年碩士論文

【摘要】：硅因為具有高的理論比容量(4200mAh/g)和豐富的資源而被作為鋰離子電池最有前景的負極材料之一。但是硅負極材料低的導電率和嚴重的體積效應限制了其商業(yè)化應用。而碳材料,包括無定形碳和石墨烯等都具備導電導鋰性能,在充放電過程中體積變化很小,而且具備優(yōu)良的延展性,可以有效地緩沖硅在充放電過程中的體積變化,因此制備硅與碳材料的復合材料有望得到高性能的新型鋰離子電池負極材料。本文分別采用微乳液法、噴霧熱解法和噴霧干燥法制備無定型碳或石墨烯與硅的復合微球做為鋰離子電池負極材料,并對制備的復合材料進行表征及電化學性能測試分析。通過微乳液法加鎂熱還原的兩步法制備了Graphene/Si復合材料,對復合材料采用掃描電鏡、X射線衍射等進行表征,并將其作為鋰離子電池負極材料進行電化學性能測試,研究了不同石墨烯含量以及碳包覆對其電化學性能的影響。研究表明,Graphene/Si復合材料在石墨烯與Si02的比例為1:1時的電化學性能是最好的,100個循環(huán)后穩(wěn)定在600mAh/g;對石墨烯與Si02的比例為1:2的樣品進行碳包覆處理,碳包覆前的樣品90個循環(huán)后容量不足400mAh/g,碳包覆之后90個循環(huán)后容量仍有700mAh/g。通過簡單的超聲噴霧熱解和部分鎂熱還原的兩步法成功制備了多孔的SiO2/Si/graphene/C微球。這種3-D結構的微球中,碳包覆的Si/SiO2納米顆粒(5-10納米)鑲嵌于石墨烯的三維網(wǎng)絡結構中,石墨烯不但可以提高微球的導電性,而且可以增強微球的結構強度。復合微球中的孔結構既可以容納硅在嵌鋰和脫鋰時的體積膨脹和收縮,又可以為電解液提供存儲的空間。將多孔微球做為鋰離子電池負極材料,其表現(xiàn)出優(yōu)異的循環(huán)穩(wěn)定性,在0.1 mA/cm2的電流密度下,第二個循環(huán)的放電容量達到1104.9mAh/g,200個循環(huán)之后仍有1141.6mAh/g,容量保留率超過100%,使得復合微球成為很有前景的鋰離子電池負極材料。通過噴霧干燥法成功制備了SiO2/graphene/C空心多孔微球,使用XRD、掃描電鏡等手段對其進行了表征,并研究了不同比例的石墨烯含量對負極材料電化學性能的影響。將其作為鋰離子電池負極材料測試其電化學性能,研究表明,隨著微球中石墨烯含量的上升,負極材料的電化學性能越好,當Si02、蔗糖和氧化石墨烯的質量比為2:1:0.8時多孔微球的循環(huán)性能最好,100個循環(huán)后容量達到270mAh/g,而不含石墨烯的樣品100個循環(huán)后容量只有80mAh/g。
[Abstract]:Silicon is regarded as one of the most promising anode materials for lithium ion batteries because of its high theoretical specific capacity (4200mAh/g) and abundant resources. However, the low conductivity and severe volume effect of silicon anode materials restrict their commercial application. However, carbon materials, including amorphous carbon and graphene, have the properties of conducting lithium, little change in volume during charge and discharge, and excellent ductility, which can effectively buffer the volume change of silicon during charge and discharge. Therefore, the composite materials of silicon and carbon are expected to obtain high performance cathode materials for lithium ion batteries. In this paper, amorphous carbon or graphene / silicon composite microspheres were prepared by microemulsion method, spray pyrolysis method and spray drying method, respectively. The composite materials were characterized and their electrochemical properties were analyzed. The Graphene / Si composite was prepared by two step method of microemulsion and magnesium thermal reduction. The composite was characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The composite was used as anode material of lithium ion battery for electrochemical performance test. The effects of different graphene content and carbon coating on electrochemical properties were studied. The results show that the electrochemical performance of Graphene / Si composite is the best when the ratio of graphene to SiO2 is 1:1, and the 100 cycles are stabilized at 600mAh/ g, and the samples with the ratio of graphene to SiO2 are treated with carbon coating at 1:2. Before carbon coating, 90 samples have less than 400mAh/ g capacity after cycling, and 90 samples after carbon coating still have a capacity of 700mAh/ g. Porous Sio _ 2 / Si _ (2 / R) -C microspheres were prepared by simple ultrasonic spray pyrolysis and partial magnesium thermal reduction. In the 3-D microspheres, the carbon-coated Si / Sio _ 2 nanoparticles (5-10 nm) are embedded in the three-dimensional network structure of graphene. Graphene can not only improve the electrical conductivity of the microspheres, but also enhance the structural strength of the microspheres. The pore structure in the composite microspheres can not only accommodate the volume expansion and contraction of silicon in lithium intercalation and delithium removal, but also provide storage space for electrolyte. When the porous microspheres are used as anode materials for lithium ion batteries, they exhibit excellent cycling stability at the current density of 0. 1 mA/cm2. The discharge capacity of the second cycle is 1104.9mAh/ g, and after 200 cycles there are still 1141.6mAh/ g, and the capacity retention is more than 100, which makes the composite microspheres a promising cathode material for lithium ion batteries. SiO2 / graphene / C hollow porous microspheres were prepared by spray drying method and characterized by XRD and SEM. The effects of graphene content in different proportion on electrochemical properties of anode materials were studied. The electrochemical properties of the anode materials for lithium ion batteries were tested. The results showed that the better the electrochemical performance of the anode materials was with the increase of graphene content in the microspheres. When the mass ratio of sucrose to graphene oxide is 2: 1: 0.8, the porous microspheres have the best cycling performance, with the capacity of 270 mg / g after 100 cycles, while the capacity of 100 samples without graphene is only 80 mg / g.
【學位授予單位】：湖南大學
【學位級別】：碩士
【學位授予年份】：2016
【分類號】：TB332;TM912
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本文編號：2064256