具有多重緩沖機(jī)制的鋰離子電池硅基負(fù)極
發(fā)布時間：2018-08-22 13:18
【摘要】：開發(fā)高比能、長壽命、低成本的二次電池是構(gòu)建新能源社會的核心工作。硅(Si)因具有十倍于現(xiàn)有商業(yè)化石墨負(fù)極的理論比容量,被認(rèn)為是新一代鋰離子電池的理想負(fù)極。但其鋰化/去鋰化過程中巨大的體積變化容易引起活性顆粒粉化、電極結(jié)構(gòu)破壞以及表面SEI膜的重復(fù)生長。這些問題嚴(yán)重制約了 Si負(fù)極的商業(yè)化應(yīng)用和高比能鋰離子電池的發(fā)展。本論文工作以開發(fā)高循環(huán)穩(wěn)定性Si基負(fù)極材料為目的,以構(gòu)建多重緩沖機(jī)制為手段,設(shè)計(jì)并制備了兩種新型Si基復(fù)合負(fù)極材料,FeSi/C復(fù)合納米纖維和Si@SiOx@C復(fù)合物。主要研究內(nèi)容及結(jié)果如下:1.FeSi/C復(fù)合納米纖維的制備與表征。以納米FeSi合金和聚丙烯腈(PAN)為原料,通過靜電紡絲及后續(xù)高溫?zé)峤?制備出FeSi/C納米復(fù)合纖維,并優(yōu)化了其制備條件。實(shí)驗(yàn)結(jié)果表明,將FeSi與PAN以1:0.5的質(zhì)量比混紡,然后在熱解產(chǎn)物FeSi/C纖維表面再化學(xué)氣相沉積(CVD)一層碳,得到的FeSi/C/C復(fù)合纖維產(chǎn)物具有最優(yōu)的電化學(xué)性能。電化學(xué)測試結(jié)果表明,FeSi/C/C復(fù)合纖維電極的初始比容量為953 mAh g-1循環(huán)200周后仍有60%的容量保持率,且循環(huán)過程中庫倫效率保持在99.5%左右;在1000mAg-1的大電流密度下,材料仍有700 mAh g-1以上的比容量。FeSi/C/C復(fù)合纖維材料優(yōu)異的電化學(xué)性能主要得益于它的多重緩沖結(jié)構(gòu),包括FeSi合金中惰性FeSi2相、主體PAN熱解碳纖維和CVD沉積碳,有效緩沖了活性Si的體積膨脹,保持了纖維結(jié)構(gòu)及表面SEI膜的穩(wěn)定性。2.Si@SiOx@C復(fù)合材料的制備與表征。利用聚丙烯酸(PAA)與Si表面羥基的氫鍵作用,通過高溫?zé)峤釹i@PAA復(fù)合物,一步法直接制備出具有雙層包覆結(jié)構(gòu)的Si@SiOx@C復(fù)合材料。由于雙包覆層在充放電過程中有效緩沖了活性Si內(nèi)核的體積膨脹,維持了電極/電解液界面和表面SEI膜的穩(wěn)定性,使得復(fù)合材料展現(xiàn)出良好的循環(huán)性能。充放電測試結(jié)果表明,材料的首周比容量為1110 mAh g-1;循環(huán)150周后仍有664mAhg-1的比容量,對應(yīng)的容量衰減率僅為0.27%/周。
[Abstract]:Developing high specific energy, long-life, low-cost secondary batteries is the core work of building a new energy society. Silicon (Si) is considered to be the ideal anode for a new generation of lithium ion batteries because of its theoretical specific capacity of 10 times that of commercial graphite anode. However, the huge volume change in the process of lithiation / delithiation can easily cause the active particles to be powdered, the electrode structure destroyed and the surface SEI film to grow repeatedly. These problems seriously restrict the commercial application of Si anode and the development of high specific energy lithium ion battery. In order to develop high cycle stable Si-based negative electrode materials and to construct multiple buffer mechanism, two new Si-based composite negative electrode materials, FeSi- / C nanofibers and Si@SiOx@C composites, have been designed and fabricated in this paper. The main contents and results are as follows: 1. Preparation and characterization of FeSi- / C nanofibers. FeSi/C nanocomposite fibers were prepared by electrospinning and pyrolysis of polyacrylonitrile (PAN) and FeSi alloy. The preparation conditions were optimized. The experimental results show that FeSi and PAN are blended at 1: 0.5 mass ratio and then redeposited on the surface of pyrolytic FeSi/C fiber by chemical vapor deposition of a layer of (CVD) carbon. The obtained FeSi/C/C composite fiber has the best electrochemical performance. The results of electrochemical measurement show that the initial specific capacity of FeSi-C / C composite fiber electrode is 953 mAh / g ~ (-1), and the capacity retention rate is still 60%, and the Coulomb efficiency is about 99.5% during the cycle, and at the high current density of 1000mAg-1, the initial specific capacity of FeSi-C / C composite fiber electrode is 953 mAh / g ~ (-1). The excellent electrochemical properties of Fesi / C / C composite fiber with a specific capacity of more than 700 mAh g ~ (-1) are mainly due to its multilayer buffer structure, including inert FeSi2 phase in FeSi alloy, PAN pyrolytic carbon fiber and carbon deposited by CVD. The volume expansion of active Si was effectively cushioned, and the stability of fiber structure and surface SEI film was maintained. The Si@SiOx@C composites with double-layer coating structure were directly prepared by pyrolysis of Si@PAA composites at high temperature by hydrogen bonding between polyacrylic acid (PAA) and hydroxyl groups on Si surface. Because the double cladding layer effectively buffers the volume expansion of the active Si core during charge and discharge, the stability of the electrode / electrolyte interface and the surface SEI film is maintained, which makes the composite exhibit good cycling performance. The results of charge-discharge test show that the specific capacity of the material is 1110 mAh g ~ (-1) in the first cycle, and the specific capacity of 664mAhg-1 is still in existence after 150 weeks of cycle, the corresponding capacity attenuation rate is only 0.27 / week.
【學(xué)位授予單位】：武漢大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TM912
本文編號：2197213
[Abstract]:Developing high specific energy, long-life, low-cost secondary batteries is the core work of building a new energy society. Silicon (Si) is considered to be the ideal anode for a new generation of lithium ion batteries because of its theoretical specific capacity of 10 times that of commercial graphite anode. However, the huge volume change in the process of lithiation / delithiation can easily cause the active particles to be powdered, the electrode structure destroyed and the surface SEI film to grow repeatedly. These problems seriously restrict the commercial application of Si anode and the development of high specific energy lithium ion battery. In order to develop high cycle stable Si-based negative electrode materials and to construct multiple buffer mechanism, two new Si-based composite negative electrode materials, FeSi- / C nanofibers and Si@SiOx@C composites, have been designed and fabricated in this paper. The main contents and results are as follows: 1. Preparation and characterization of FeSi- / C nanofibers. FeSi/C nanocomposite fibers were prepared by electrospinning and pyrolysis of polyacrylonitrile (PAN) and FeSi alloy. The preparation conditions were optimized. The experimental results show that FeSi and PAN are blended at 1: 0.5 mass ratio and then redeposited on the surface of pyrolytic FeSi/C fiber by chemical vapor deposition of a layer of (CVD) carbon. The obtained FeSi/C/C composite fiber has the best electrochemical performance. The results of electrochemical measurement show that the initial specific capacity of FeSi-C / C composite fiber electrode is 953 mAh / g ~ (-1), and the capacity retention rate is still 60%, and the Coulomb efficiency is about 99.5% during the cycle, and at the high current density of 1000mAg-1, the initial specific capacity of FeSi-C / C composite fiber electrode is 953 mAh / g ~ (-1). The excellent electrochemical properties of Fesi / C / C composite fiber with a specific capacity of more than 700 mAh g ~ (-1) are mainly due to its multilayer buffer structure, including inert FeSi2 phase in FeSi alloy, PAN pyrolytic carbon fiber and carbon deposited by CVD. The volume expansion of active Si was effectively cushioned, and the stability of fiber structure and surface SEI film was maintained. The Si@SiOx@C composites with double-layer coating structure were directly prepared by pyrolysis of Si@PAA composites at high temperature by hydrogen bonding between polyacrylic acid (PAA) and hydroxyl groups on Si surface. Because the double cladding layer effectively buffers the volume expansion of the active Si core during charge and discharge, the stability of the electrode / electrolyte interface and the surface SEI film is maintained, which makes the composite exhibit good cycling performance. The results of charge-discharge test show that the specific capacity of the material is 1110 mAh g ~ (-1) in the first cycle, and the specific capacity of 664mAhg-1 is still in existence after 150 weeks of cycle, the corresponding capacity attenuation rate is only 0.27 / week.
【學(xué)位授予單位】：武漢大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TM912
【參考文獻(xiàn)】
相關(guān)期刊論文 前3條
1 張雙虎;遲彩霞;張盛武;;鋰離子電池預(yù)鋰化技術(shù)的最新研究進(jìn)展[J];電源技術(shù);2015年07期
2 Delong Ma;Zhanyi Cao;Anming Hu;;Si-Based Anode Materials for Li-Ion Batteries:A Mini Review[J];Nano-Micro Letters;2014年04期
3 艾新平;楊漢西;;淺析動力電池的技術(shù)發(fā)展[J];中國科學(xué):化學(xué);2014年07期
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