本文關(guān)鍵詞：鋰離子電池用納米碳纖維—硅復(fù)合負(fù)極材料　出處：《東華大學(xué)》2014年碩士論文　論文類型：學(xué)位論文

  更多相關(guān)文章： 鋰離子電池 負(fù)極材料 熱解細(xì)菌纖維素 碳納米管 硅

【摘要】：鋰離子電池(LIB)的無記憶效應(yīng)、能量密度高以及自放電率低等優(yōu)點(diǎn)使其在工業(yè)領(lǐng)域迅猛發(fā)展。隨著其在便攜式設(shè)備和動(dòng)力汽車中的應(yīng)用,人們對(duì)于鋰離子電池的負(fù)極材料提出了更高的要求。目前石墨作為商用鋰離子電池的負(fù)極材料,在充放電過程中鋰的嵌入量較低,理論容量只有372mAh/g。同時(shí)由于過充或其他原因引起的鋰枝晶影響電池的安全性。 Sn、Si、A1、 Pb等金屬與鋰形成金屬間化合物,表現(xiàn)出較好的電化學(xué)性能。這些高容量的負(fù)極材料還沒有商業(yè)化的原因是其在嵌鋰時(shí)發(fā)生較大的體積膨脹,超過100%。這會(huì)造成材料結(jié)構(gòu)發(fā)生嚴(yán)重的破壞甚至粉化,使材料失去電接觸,導(dǎo)致容量的迅速衰減。因此消除因金屬材料在充放電過程中的體積變化而造成的電池失效成為負(fù)極材料研究重點(diǎn)。 目前的研究表明,三維網(wǎng)絡(luò)電極結(jié)構(gòu)能有效緩沖硅在嵌鋰時(shí)產(chǎn)生的體積變化,同時(shí)這種結(jié)構(gòu)為鋰離子提供了傳輸通道,提高電極的倍率充放電性。熱解細(xì)菌纖維素(Pyrolyzed Bacterial cellulose, PBC)保留了細(xì)菌纖維素(BC)的三維多孔結(jié)構(gòu),將上述金屬材料擔(dān)載到PBC的三維網(wǎng)絡(luò)中,形成金屬／納米碳纖維復(fù)合三維電極是提高LIB負(fù)極材料電化學(xué)綜合性能的有效途徑。因此,將PBC與硅材料復(fù)合制備新型鋰離子電池負(fù)極材料,對(duì)于將硅負(fù)極材料商用化具有重要意義。 本論文以BC為前驅(qū)體,通過高溫?zé)Y(jié)制備了具有三維網(wǎng)絡(luò)結(jié)構(gòu)的納米碳纖維(PBC)。在此基礎(chǔ)上通過打漿法和溶膠凝膠法分別制備了PBC/碳納米管(CNTs、PBC/Si和PBC/SiO2復(fù)合負(fù)極材料,利用FESEM、TG、XRD以及循環(huán)測(cè)試等方法詳細(xì)研究了其結(jié)構(gòu)和性能的關(guān)系。主要研究?jī)?nèi)容和結(jié)論如下： 1.PBC及PBC/CNTs的結(jié)構(gòu)與性能。PBC具有三維多孔網(wǎng)狀結(jié)構(gòu),存在石墨化碳。電性能測(cè)試顯示PBC的電池容量略低于石墨,但加入羧基化碳納米管可以提高PBC的導(dǎo)電性以及電池的容量。PBC/CNTs復(fù)合材料的首次充電容量達(dá)到1280.6mAh/g,庫倫效率為45.7%。循環(huán)20次后可逆容量達(dá)到433mAh/g,不僅優(yōu)于PBC,同時(shí)超過了石墨的理論容量。 2.打漿法制備的PBC/Si復(fù)合材料的結(jié)構(gòu)與性能。PBC/Si的電化學(xué)性能較好,首次充電容量達(dá)到3375mAh/g,經(jīng)過65次循環(huán)后后可逆容量為1369mAh/g。只要適當(dāng)?shù)目刂乒璧暮考捌浞稚?PBC的特殊三維結(jié)構(gòu)可以作為充放電過程中硅體積膨脹的緩沖區(qū)。 3.溶膠凝膠法制備PBC/SiO2復(fù)合材料的結(jié)構(gòu)與性能。PBC/SiO2復(fù)合材料的導(dǎo)電性差、容量低,存在嚴(yán)重的粉化現(xiàn)象。僅僅用二氧化硅作為碳-硅復(fù)合負(fù)極材料的硅源不是十分有效。
[Abstract]:Li-ion battery (Lib) has many advantages, such as memoryless effect, high energy density and low self-discharge rate, which makes it develop rapidly in industrial field, with its applications in portable devices and power vehicles. At present, graphite is the negative electrode material of commercial lithium ion battery, and the intercalation of lithium in the process of charge and discharge is low. The theoretical capacity is only 372mAh / g, and lithium dendrites due to overcharge or other causes affect the safety of the battery. The metals such as Sn-SiOA1, Pb and so on form intermetallic compounds with lithium. These high capacity anode materials have not been commercialized because of their larger volume expansion in lithium intercalation. More than 100. This can cause serious damage to the structure of the material or even powdered, resulting in the loss of electrical contact with the material. Therefore, eliminating the battery failure caused by the volume change of metal materials during charge and discharge has become the research focus of negative electrode materials. Current studies have shown that the three-dimensional network electrode structure can effectively buffer the volume change of silicon in lithium intercalation, and this structure provides a transport channel for lithium ion. The pyrolytic bacterial cellulose was Pyrolyzed Bacterial cellulose. PBCs retained the three-dimensional porous structure of bacterial cellulose (BC) and loaded the above metal materials into the three-dimensional network of PBC. The formation of metal / carbon nanocomposite three-dimensional electrode is an effective way to improve the electrochemical properties of LIB anode materials. Therefore, a new type of cathode materials for lithium ion batteries is prepared by combining PBC with silicon materials. It is of great significance to commercialize silicon anode materials. In this thesis, BC was used as the precursor. PBC / CNTs with three-dimensional network structure were prepared by high temperature sintering, and PBC / CNTs were prepared by beating and sol-gel methods respectively. PBC/Si and PBC/SiO2 composite negative electrode materials, using Fesemer TG. The relationship between structure and performance is studied in detail by XRD and loop testing. The main contents and conclusions are as follows: 1. The structure and performance of PBC and PBC/CNTs. PBC has a three-dimensional porous network structure, and there is graphitized carbon. The electrical performance test shows that the battery capacity of PBC is slightly lower than that of graphite. However, the addition of carboxylated carbon nanotubes can improve the conductivity of PBC and the initial charging capacity of the composite. The Coulomb efficiency is 45.7 and the reversible capacity is 433mAh / g after 20 cycles, which is not only superior to PBC, but also exceeds the theoretical capacity of graphite. 2. The structure and properties of PBC/Si composites prepared by beating pulping method. The electrochemical properties of PBC / Si are better, and the initial charging capacity is 3375mAh/ g. After 65 cycles, the reversible capacity is 1369 mg 路h / g. The content of silicon and its dispersion should be controlled properly. The special three-dimensional structure of PBC can be used as a buffer for volume expansion of silicon during charging and discharging. 3. The structure and properties of PBC/SiO2 composites prepared by sol-gel method. The conductivity and capacity of PBC / SiO2 composites are poor. There is a serious pulverization phenomenon. It is not very effective to use silicon dioxide as the silicon source of carbon-silicon composite negative electrode material.
【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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