本文關鍵詞：炭包覆納米硅復合負極材料的制備及其性能研究　出處：《中國林業(yè)科學研究院》2017年碩士論文　論文類型：學位論文

  更多相關文章： 鋰離子電池 復合負極材料 氮摻雜 比容量 穩(wěn)定性

【摘要】：鋰離子電池的能量密度高,無記憶效應,循環(huán)穩(wěn)定性好,對環(huán)境無污染,且安全系數較高,故在眾多的儲能裝置中出類拔萃,得到廣泛關注。但隨著科學技術的進步,各類電子設備、電動儀器、軍事裝備等對電極材料的要求越來越苛刻,只有開發(fā)出高容量、高穩(wěn)定性的大功率鋰離子電池才能滿足社會發(fā)展的需要。負極材料至關重要,硅作為能量密度高的新型負極材料,成為研究者關注的焦點。但硅在電池循環(huán)過程中體積會發(fā)生嚴重的膨脹,導致電池容量銳減,阻礙了硅負極的商業(yè)化,但炭材料的存在可以彌補這一缺陷,炭材料嵌鋰電位較低,在電池充放電循環(huán)過程中容量不會驟減,穩(wěn)定性好,且體積變化不明顯,若將硅與炭材料復合,則可以最大限度的發(fā)揮兩者的優(yōu)勢,有望制備出比較理想的負極材料。本研究以乙基纖維素為碳源,經水熱碳化及高溫炭化、HF刻蝕SiO2后制備了炭包覆納米硅復合負極材料,并將其組裝成扣式電池。考察了反應條件對微球制備的影響,探討了高溫炭化溫度、硅含量對負極材料電化學性能的影響。并利用SEM、XPS、FT-IR、XRD、激光粒度分析等對材料的形貌、粒徑分布、官能團分布、晶體結構等進行表征,SEM及激光粒度分析顯示微球的球型較好,平均粒徑為7.2μm;FT-IR及XPS結果顯示,在水熱碳化過程中產生了芳環(huán)及羧基結構;此外,XRD譜圖上可以明顯看到硅及無定形碳的吸收峰;恒電流充放電及倍率性能測試顯示,在首次充放電循環(huán)中,材料的放電比容量為930.3 mAh/g,相應的庫倫效率為69.1%,當循環(huán)至第40次時,電池的容量保持率為64.7%。以丙烯酰胺為單體經反相懸浮聚合得到聚丙烯酰胺,并以其為氮源、碳源,經高溫炭化及HF刻蝕SiO2后制備了氮摻雜炭包覆納米硅負極材料,并將其組裝成扣式電池。研究了原料用量及剪切速度等對微球制備的影響。SEM及激光粒度分析表明微球順滑圓整,平均粒徑為10.1μm;FT-IR顯示丙烯酰胺很容易聚合為聚丙烯酰胺,XRD顯示氮摻雜炭材料包覆納米硅未改變其晶體結構。電化學性能測試表明在第一圈充放電循環(huán)中,復合材料的放電比容量為1 055.5mAh/g,相對應的庫倫效率為71.8%,倍率性能測試結果表明由于氮元素的摻雜負極材料在大電流密度下的容量衰減減緩,穩(wěn)定性提高。
[Abstract]:Li-ion battery has high energy density, no memory effect, good cycle stability, no pollution to the environment, and high safety factor, so it is outstanding in many energy storage devices. But with the progress of science and technology, all kinds of electronic equipment, electric instruments, military equipment and other electrode materials are increasingly demanding, only to develop high capacity. High-stability high-power lithium ion batteries can meet the needs of social development. Negative electrode material is very important. Silicon is a new type of negative electrode material with high energy density. However, the volume of silicon in the battery cycle will be seriously expanded, resulting in a sharp reduction in the capacity of the battery, which hinders the commercialization of silicon negative electrode, but the presence of carbon materials can make up for this defect. The lithium intercalation potential of carbon material is low, the capacity will not be reduced, the stability is good, and the volume change is not obvious during the battery charge and discharge cycle, if the silicon and carbon materials are combined, the advantages of the two materials can be maximized. In this study, carbon coated nano-silicon composite anode material was prepared by hydrothermal carbonization and high temperature carbonization HF etching SiO2 with ethylcellulose as carbon source. The effect of reaction conditions on the preparation of microspheres was investigated. The effects of high temperature carbonization temperature and silicon content on the electrochemical properties of negative electrode materials were investigated. The morphology, particle size distribution, functional group distribution and crystal structure of the materials were characterized by FT-IRN XRD and laser particle size analysis. The results of SEM and laser particle size analysis showed that the spherical shape of the microspheres was better. The average particle size was 7.2 渭 m; The results of FT-IR and XPS showed that aryl rings and carboxyl groups were formed during hydrothermal carbonization. In addition, the absorption peaks of silicon and amorphous carbon can be clearly seen on the XRD spectra. The constant current charge-discharge and rate performance tests show that the discharge specific capacity of the material is 930.3 mg / g and the corresponding Coulomb efficiency is 69.1% in the first charge-discharge cycle. At the 40th cycle, the capacity retention rate of the battery was 64.7. Polyacrylamide was synthesized by reverse suspension polymerization with acrylamide as monomer, and it was used as nitrogen source and carbon source. After high temperature carbonization and HF etching of SiO2, nitrogen-doped carbon coated nanocrystalline silicon anode materials were prepared. The effects of the amount of raw materials and shear rate on the preparation of microspheres were studied. SEM and laser particle size analysis showed that the microspheres were smooth and round with an average diameter of 10.1 渭 m. FT-IR showed that acrylamide was easily polymerized into polyacrylamide. The results showed that nitrogen-doped carbon coated with nano-silicon did not change its crystal structure. The electrochemical performance test showed that in the first cycle of charge and discharge. The specific discharge capacity of the composite is 1 055.5 mg / g, and the corresponding Coulomb efficiency is 71.8%. The results of the rate performance test show that the capacity attenuation of nitrogen-doped anode materials at high current density is reduced and the stability is improved.
【學位授予單位】：中國林業(yè)科學研究院
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TM912

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