發(fā)布時(shí)間：2018-05-27 07:25

  本文選題：鋰離子電池 + 3D結(jié)構(gòu)石墨烯　； 參考：《東華大學(xué)》2014年碩士論文

【摘要】：鋰離子電池由于具有比能量大、工作電壓高、安全性好、環(huán)境污染小等優(yōu)點(diǎn),在各種便攜式電子設(shè)備、電動(dòng)汽車(chē)等方面有著廣泛的應(yīng)用前景。最近幾年,隨著對(duì)高能電源需求的增長(zhǎng),圍繞如何開(kāi)發(fā)高能密度、快速大功率充放電的鋰離子電池展開(kāi)了大量研究。一般來(lái)說(shuō),鋰離子電池的總比容量是由組成電池的各元件共同決定的,而負(fù)極材料作為儲(chǔ)鋰的主體,是提高鋰離子電池總比容量、循環(huán)壽命、充放電性能等相關(guān)參數(shù)的關(guān)鍵。 硅具有非常高的理論比容量和較低的嵌/脫鋰電位,被認(rèn)為是最具有潛力實(shí)現(xiàn)下一代高能量密度鋰離子電池的新型負(fù)極材料之一。但在充放電過(guò)程中,體積過(guò)度膨脹粉化導(dǎo)致容量衰減快,成為其作為商業(yè)負(fù)極材料的最大障礙。而碳材料作為負(fù)極材料雖然比容量小,但不僅具有一定的電化學(xué)活性,結(jié)構(gòu)也較穩(wěn)定,可以作為硅電極的“緩沖基體”。因此,結(jié)合兩者的性能有可能制備出具有高容量和優(yōu)良循環(huán)性能的硅-碳復(fù)合負(fù)極材料。 本論文是與法國(guó)圣戈班集團(tuán)上海研發(fā)中心合作,擬開(kāi)發(fā)出一種具有高容量和優(yōu)良循環(huán)性能的鋰離子電池硅碳復(fù)合負(fù)極材料。主要研究?jī)?nèi)容有,通過(guò)SiO發(fā)生歧化反應(yīng),在不同的熱處理?xiàng)l件下制備多種Si-SiOx復(fù)合物,并將其與用真空抽濾法制備的三維網(wǎng)絡(luò)結(jié)構(gòu)石墨烯進(jìn)行自組裝,得到不同種類的Si-SiOx-C復(fù)合負(fù)極材料。用X射線衍射儀(XRD)、掃描電子顯微鏡(SEM)、透射電子顯微鏡(TEM)和藍(lán)電電池測(cè)試系統(tǒng)分別對(duì)Si-SiOx復(fù)合物、石墨烯及Si-SiOx-C復(fù)合材料的形貌、結(jié)構(gòu)和電化學(xué)性能進(jìn)行了表征。 實(shí)驗(yàn)結(jié)果表明,真空抽濾法可以成功制備空間網(wǎng)絡(luò)結(jié)構(gòu)十分明顯的3D結(jié)構(gòu)石墨烯。其電化學(xué)測(cè)試結(jié)果顯示,石墨烯首次循環(huán)充電比容量為311.2mAh/g,與純炭材料的理論比容量372mAh/g相差較少,且?guī)靷愋矢哌_(dá)84.9%；經(jīng)過(guò)100次循環(huán)后充電比容量為134.1mAh/g,雖然相比首次充電比容量有所減少,但是比容量仍然較高,且整個(gè)充放電過(guò)程的穩(wěn)定性也較好,第100次循環(huán)的庫(kù)倫效率也高達(dá)97%,充分說(shuō)明3D結(jié)構(gòu)石墨烯用作鋰離子電池負(fù)極材料時(shí)具有較好的電化學(xué)性能。 通過(guò)SiO的歧化反應(yīng)成功制備了Si-SiOx復(fù)合物。制備過(guò)程中由于熱處理?xiàng)l件不同得到的Si-SiOx復(fù)合物的性能也不同。其電化學(xué)測(cè)試結(jié)果顯示,隨著反應(yīng)過(guò)程中的熱處理溫度的升高,Si的結(jié)晶度也隨之升高,相應(yīng)的Si-SiOx復(fù)合物的首次循環(huán)充放電比容量卻越來(lái)越低,這是因?yàn)闊崽幚頊囟仍礁?Si的結(jié)晶度越大,Si的顆粒尺寸越大,尺寸較大的Si顆粒不利于鋰離子嵌入和脫出,從而導(dǎo)致比容量下降。而在Si-SiOx復(fù)合物的多次循環(huán)性能測(cè)試中,復(fù)合物的比容量急劇下降,這是由于歧化反應(yīng)過(guò)程中生成了大量的單質(zhì)硅,雖然硅具有非常高的理論比容量和較低的嵌/脫鋰電位,但其體積過(guò)度膨脹粉化導(dǎo)致容量衰減快,因而循環(huán)數(shù)次之后其容量大大衰減。說(shuō)明較低的熱處理溫度有利于制備出比容量更高的Si-SiOx復(fù)合物電極材料。 當(dāng)Si-SiOx復(fù)合物與石墨烯自組裝之后,得到的Si-SiOx-C復(fù)合材料的首次循環(huán)充放電比容量大大提高,充電比容量由152.24mAh/g上升到811.3mAh/g,不可逆容量也大大減少,且電池的庫(kù)倫效率由14%增加到52%。在循環(huán)100次之后,其充放電比容量也大大提高,穩(wěn)定性很好,從第5次循環(huán)開(kāi)始,充放電比容量都維持在一個(gè)穩(wěn)定的水平,約為150mAh/g左右,基本不再衰減；不可逆容量也大大減少,而庫(kù)倫效率也大大提高,基本達(dá)到100%。這表明石墨烯與Si-SiOx復(fù)合物組裝之后能夠大大提高比容量、循環(huán)穩(wěn)定性和庫(kù)倫效率,說(shuō)明石墨烯能夠有效限制Si顆粒的體積膨脹效應(yīng),提高Si-SiOx復(fù)合物的電化學(xué)性能。
[Abstract]:Because of the advantages of high energy, high working voltage, good safety and small environmental pollution, lithium ion batteries have a wide application prospect in all kinds of portable electronic equipment and electric vehicles. In recent years, with the increase in the demand for high energy power supply, lithium ion batteries with high energy density and high power charge and discharge are around. In general, the total specific capacity of the lithium ion battery is determined by the components of the battery. As the main body of the lithium storage, the negative electrode is the key to improve the total specific capacity, the cycle life, the charge discharge performance and other related parameters of the lithium ion battery.
Silicon has a very high theoretical specific capacity and low embed / delithium potential. It is considered to be one of the most potential new anode materials for the next generation of high energy density lithium ion batteries. However, during the charge and discharge process, the volume of excessive expansion of the powder leads to the capacity attenuation and the biggest obstacle to be used as a commercial anode material. As a negative material, although its specific capacity is small, it not only has a certain electrochemical activity, but also has a stable structure, which can be used as a "buffer matrix" for silicon electrode. Therefore, it is possible to prepare a silicon carbon composite negative material with high capacity and excellent cycling performance by combining the performance of the two.
In this paper, in cooperation with the Shanghai R & D center of Saint Gobain group, France, a kind of silicon carbon composite anode material with high capacity and excellent cycling performance is developed. The main research contents include the preparation of multiple Si-SiOx complexes under different heat treatment conditions through SiO disproportionation and the vacuum extraction method. The prepared three-dimensional network structure graphene is self-assembled, and different kinds of Si-SiOx-C composite negative materials are obtained. The morphology, structure and electrochemical properties of Si-SiOx complex, the morphology, structure and electrochemical properties of the composites of Si-SiOx, stone and Si-SiOx-C are respectively used by the X ray diffractometer (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM) and the blue electric battery test system. It was characterized.
The experimental results show that the vacuum pumping method can successfully prepare the 3D structure graphene with very obvious spatial network structure. Its electrochemical test results show that the first cycle charge specific capacity of graphene is 311.2mAh/g, and the theoretical specific capacity of carbon materials is less than that of 372mAh/g, and the efficiency of Kulun is up to 84.9%; after 100 cycles, the charge ratio is compared. The capacity is 134.1mAh/g, although the specific capacity of the first charge is reduced, but the specific capacity is still higher, and the stability of the whole charging and discharging process is better. The efficiency of the 100th cycle of Kulun is also up to 97%. It fully shows that the 3D structure graphene has good electrochemical performance when it is used as anode material for lithium ion battery.
The Si-SiOx complex was successfully prepared by the disproportionation reaction of SiO. The properties of the Si-SiOx complex obtained from different heat treatment conditions were different during the preparation process. The electrochemical test results showed that the crystallinity of Si increased with the increase of heat treatment temperature during the reaction process, and the corresponding Si-SiOx complex was recharged for the first time. The electrical specific capacity is getting lower and lower, because the higher the heat treatment temperature, the greater the crystallinity of Si, the larger the size of Si particles, the larger size Si particles are not conducive to the insertion and removal of lithium ion, which leads to the decrease of the specific capacity. And the specific capacity of the composite decreases sharply in the multiple cycle performance testing of the Si-SiOx complex, which is due to disproportionation. A large number of mono silicon is generated during the reaction, although silicon has very high theoretical specific capacity and low potential for inlaying / removing lithium, but its volume overexpansion pulverization leads to rapid capacity attenuation, so its capacity greatly attenuates after several cycles. It shows that the lower heat treatment temperature is advantageous to the preparation of Si-SiOx complex electricity with higher specific capacity. Polar materials.
When the Si-SiOx complex and graphene are self assembled, the initial cyclic charge discharge capacity of the Si-SiOx-C composite is greatly increased, the charge specific capacity is increased from 152.24mAh/g to 811.3mAh/g, and the irreversible capacity is greatly reduced, and the Kulun efficiency of the battery is increased from 14% to 52%. after 100 cycles, and its charge discharge ratio is also great. To improve, the stability is very good, from the fifth cycle, the charge discharge specific capacity is maintained at a stable level, about 150mAh/g, basically no longer attenuating, the irreversible capacity is greatly reduced, and the efficiency of Kulun is greatly improved, basically reaching the 100%.. Ring stability and Kulun efficiency indicate that graphene can effectively limit the volume expansion effect of Si particles and enhance the electrochemical performance of Si-SiOx composites.
【學(xué)位授予單位】：東華大學(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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