本文選題：AZO@C + 木棉纖維　； 參考：《浙江工業(yè)大學(xué)》2017年碩士論文

【摘要】：鋰硫電池因?yàn)榫哂斜热萘扛摺⒛芰棵芏却蟆①Y源豐富和成本低廉等優(yōu)點(diǎn),而受到了研究者們的廣泛關(guān)注。但是,硫正極也面臨著許多問題,比如硫的導(dǎo)電性較差,“穿梭效應(yīng)”,多硫化鋰的沉積不可控,硫的體積效應(yīng)較為嚴(yán)重等。這些問題導(dǎo)致了鋰硫電池在實(shí)際使用中容量衰減明顯,庫倫效率低下。為了解決這些問題,本文從材料的微觀結(jié)構(gòu)入手,結(jié)合表面修飾和元素?fù)诫s等手段,分別以木棉纖維和雞蛋清為碳源和模板,合成了鋁摻雜氧化鋅/碳復(fù)合材料(AZO@C)和摻氮生物多孔碳兩種改性碳材料,并對其進(jìn)行了相組成、形貌和微觀結(jié)構(gòu)表征,以及電化學(xué)性能測試。主要研究結(jié)果如下:(1)在第三章中,以木棉纖維為模板和碳源,合成了AZO@C復(fù)合材料,并用XRD、XPS、SEM和TEM等手段對其進(jìn)行了結(jié)構(gòu)和形貌表征。結(jié)果顯示,煅燒研磨后的木棉基底為微米片狀結(jié)構(gòu),其表面上修飾有15nm到30nm的AZO納米顆粒,并且具有良好的結(jié)晶性。(2)在第四章中,將AZO@C等復(fù)合材料與單質(zhì)硫混合制備了硫正極。電化學(xué)測試結(jié)果表明,AZO@C/S電極展現(xiàn)出了優(yōu)于Zn O@C/S和Al2O3@C/S電極的電化學(xué)性能。當(dāng)電流密度為0.1C時(shí),AZO@C/S電極在100次循環(huán)之后依然保持著927 m Ah g-1的可逆(3)容量;當(dāng)電流密度增至0.5C時(shí),300次循環(huán)后其放電容量依然可以保持在544 m Ah g-1,換算成每圈循環(huán)的容量損失率為0.039%。即使在硫載量達(dá)到6.69 mg cm-2時(shí),電池在0.5C循環(huán)100次后仍有466 m Ah g-1的容量。如此優(yōu)異的電化學(xué)性能主要?dú)w因于極性的AZO顆粒具有較高的導(dǎo)電性,它能有效地抑制“穿梭效應(yīng)”并為多硫化鋰的轉(zhuǎn)變提供反應(yīng)動力。(4)在第五章中,以雞蛋清同時(shí)作為碳源和氮源,制備了氮摻雜的多孔碳材料。SEM、BET等結(jié)果表明該碳材料具有良好的多孔結(jié)構(gòu)。與硫復(fù)合制成硫電極后,復(fù)合材料展現(xiàn)出了良好的電化學(xué)性能:以硫脲為外加氮源制備的N-C/S電極在0.1C電流密度下循環(huán)200次后依然有近700 m Ah g-1的可逆容量,容量保持率為84%,遠(yuǎn)超過普通的活性炭材料。電池性能的提升主要是因?yàn)榈膿诫s使得碳材料中產(chǎn)生了帶正電的活性位點(diǎn),這些位點(diǎn)能夠有效地吸附帶負(fù)電的多硫根離子,從而減緩了多硫化鋰在電解液中的溶解。
[Abstract]:Lithium-sulfur batteries have attracted much attention due to their high specific capacity, high energy density, rich resources and low cost. However, sulfur cathode also faces many problems, such as poor conductivity of sulfur, "shuttle effect", uncontrollable deposition of lithium polysulfide, and serious volume effect of sulfur. These problems lead to obvious capacity attenuation and low Coulomb efficiency in practical use of lithium-sulfur batteries. In order to solve these problems, this paper starts with the microstructure of the material, combines the surface modification and element doping, respectively, using kapok fiber and egg white as carbon source and template. Aluminum-doped zinc oxide / carbon composites (AZOOC) and nitrogen-doped biological porous carbon composites were synthesized, and their phase composition, morphology, microstructure and electrochemical properties were characterized. The main results are as follows: (1) in chapter 3, AZOOC composites were synthesized using kapok fiber as template and carbon source. The structure and morphology of AZOOC composites were characterized by means of XRDX, XPS, SEM and TEM. The results show that the calcined kapok substrate is micrometer lamellar structure, the surface of which is modified with 15nm to 30nm nanoparticles, and has good crystallinity. (2) in the fourth chapter, the composite materials such as AZOOC and simple sulfur are mixed to prepare the sulfur positive electrode. The electrochemical test results show that the AZO @ C / S electrode exhibits better electrochemical performance than the Zn-Or C / S and Al _ 2O _ 3 @ C / S electrodes. When the current density is 0.1 C, the reversible (3) capacity of the AZO @ C / S electrode remains at 927 mAh g-1 after 100 cycles. When the current density is increased to 0.5 C, the discharge capacity of 300 cycles can be maintained at 544 mAh g-1, and the loss rate of capacity converted to each cycle is 0.039%. Even when the sulfur load reached 6.69 mg cm-2, the battery still had the capacity of 466mAh g-1 after 100th cycle at 0.5C. Such excellent electrochemical properties are mainly attributed to the high conductivity of polar AZO particles, which can effectively suppress the "shuttle effect" and provide the reaction power for the transition of lithium polysulfide. (4) in Chapter 5, Using egg white as carbon source and nitrogen source, N-doped porous carbon material, SEMM-BET, was prepared. The results showed that the carbon material had a good porous structure. After recombination with sulfur, the composite showed good electrochemical performance: the N-C / S electrode with thiourea as the external nitrogen source still had a reversible capacity of nearly 700 mAh g-1 after 200 cycles at 0.1C current density. Capacity retention is 84%, far more than ordinary activated carbon materials. The improvement of battery performance is mainly due to the presence of positively charged active sites in carbon due to nitrogen doping, which can effectively adsorb negatively charged polysulfide ions, thus slowing down the dissolution of lithium polysulfide in electrolyte.
【學(xué)位授予單位】：浙江工業(yè)大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TQ127.11;TB33;TM912

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