本文選題：鋰硫電池 + 硫化鋰　； 參考：《浙江大學(xué)》2017年碩士論文

【摘要】：為了適應(yīng)未來社會對經(jīng)濟(jì)、環(huán)保、高效的能源體系要求,研究開發(fā)新型綠色能量存儲材料及器件,已成為各國科學(xué)家們關(guān)注的重點。鋰硫電池因具有理論能量密度高(2674Wh·kg-1和2697Wh.L-1)、成本便宜、環(huán)境友好等優(yōu)勢,成為最具發(fā)展前景的下一代能源存儲體系之一。但是正極材料的電絕緣特性、充放電過程中多硫化物的穿梭效應(yīng)、體積應(yīng)變以及負(fù)極材料鋰易生成枝晶等問題,導(dǎo)致鋰硫電池的循環(huán)穩(wěn)定性和安全性能較差,嚴(yán)重制約了其產(chǎn)業(yè)化進(jìn)程。硫化鋰是硫放電后的終產(chǎn)物,因其本身含有鋰源,可以采用非鋰負(fù)極與其匹配制備全電池,從而提高電池安全性。然而,硫化鋰正極材料同樣存在導(dǎo)電性差和多硫化物溶解穿梭的問題,本文設(shè)計并制備了碳包覆Li2S@C復(fù)合正極材料,并采用納米化策略來進(jìn)一步改善Li2S正極材料導(dǎo)電性能,使得正極材料的電化學(xué)性能得到了大幅改善。主要研究工作如下:(1)以PVP為碳源,利用Li2S和PVP在四氫呋喃溶劑中溶解度的差異,通過調(diào)控溫度蒸發(fā)溶劑,使Li2S和PVP先后析出,之后通過高溫退火的方法將PVP分解碳化,得到碳包覆的Li2S復(fù)合正極材料。該復(fù)合材料表現(xiàn)了較好的電化學(xué)性能,在0.2C充放電時,首次放電容量為865.4mAh·g-1 100次循環(huán)之后,其容量衰退至593.1 mAh·g-1,庫倫效率降至93%。(2)以納米級聚苯乙烯(PS)微球為形核劑,利用溶液蒸發(fā)和化學(xué)氣相沉積(CVD)相結(jié)合的方法制備納米尺度核殼結(jié)構(gòu)的復(fù)合正極材料。因為PS球在高溫下會裂解,所以制備得到的復(fù)合材料殼層內(nèi)部有一定空間余量,可以緩解體積效應(yīng)。復(fù)合正極材料表面CVD沉積的碳?xì)右环矫嫣岣吡嘶钚晕镔|(zhì)Li2S的導(dǎo)電性,另一方面作為阻擋層,可以有效地將充放電過程中產(chǎn)生的多硫化物限制在殼層內(nèi)部,抑制多硫化物的穿梭效應(yīng),提高活性物質(zhì)的利用率,從而提高材料的循環(huán)性能。而納米化的結(jié)構(gòu)設(shè)計有效縮短了鋰離子在正極材料中的擴(kuò)散距離,從而使得整個正極材料的離子和電子傳輸速度得到提高,繼而改善正極材料的倍率性能。在0.2C充放電時,首次放電容量為1121.9mAh·g-1,100次循環(huán)之后,其可逆容量仍可保持為804.2mAh·g-1,容量保持率為71.7%,庫倫效率維持在96%以上。在1C和2C的高測試電流下,其容量仍可以達(dá)到760.7 mAh.g-1和682.9 mAh.g-1。(3)以納米導(dǎo)電炭黑顆粒為形核劑,利用溶液蒸發(fā)和CVD相結(jié)合的方法合成類似雞蛋結(jié)構(gòu)的復(fù)合正極材料nano-Li2S@C,其中納米導(dǎo)電炭黑為蛋黃,Li2S為蛋白,表面包覆層為蛋殼。在納米化設(shè)計和碳包覆協(xié)同作用下,電極顯示了良好的循環(huán)和倍率性能。在0.2C充放電時,首次放電容量為1083.5 mAh·g-1,100次循環(huán)之后,其可逆容量仍可保持為893.6mAh·g-1,容量保持率為82.5%,庫倫效率維持在96%以上。在1C和2C的高測試電流下,其容量仍可以達(dá)到763.5 mAh.g-1 和 625.8 mAh.g-1。
[Abstract]:In order to meet the requirements of economic, environmental protection and efficient energy systems in the future, the research and development of new green energy storage materials and devices has become the focus of attention of scientists all over the world. Lithium-sulfur batteries have the advantages of high theoretical energy density 2674Wh kg-1 and 2697Wh.L-1, low cost and environment-friendly, so they have become one of the most promising next-generation energy storage systems. However, the electrical insulation characteristics of cathode materials, the shuttle effect of polysulfide during charge and discharge, the volume strain and the dendrite formation of lithium in negative electrode materials lead to poor cycle stability and safety performance of lithium sulfur batteries. Seriously restricted its industrialization process. Lithium sulphide is the final product of sulfur discharge. Because it contains lithium source, it can be used to match the non-lithium negative electrode to prepare the whole battery, thus improving the safety of the battery. However, lithium sulphide cathode materials also have the problems of poor conductivity and polysulfide solution shuttling. In this paper, carbon coated Li2S@C composite cathode materials are designed and prepared, and nanocrystalline strategies are adopted to further improve the conductivity of Li2S cathode materials. The electrochemical performance of the cathode material is greatly improved. The main research work is as follows: (1) by using PVP as carbon source and using the difference of solubility of Li2S and PVP in tetrahydrofuran solvent, Li2S and PVP are precipitated successively by adjusting the temperature evaporation solvent, and then the PVP is decomposed and carbonized by high temperature annealing. Carbon coated Li2S composite cathode material was obtained. The composite showed good electrochemical properties. After the first discharge capacity of 865.4mAh g-1 was 100 cycles, the capacity of the composite decreased to 593.1 mAh g -1, and the Coulomb efficiency decreased to 93%. 2) the nanocrystalline polystyrene (PS) microsphere was used as nucleating agent. Nanoscale composite cathode materials with core-shell structure were prepared by the method of solution evaporation and chemical vapor deposition (CVD). Because the PS spheres will be cracked at high temperature, there is a certain amount of space in the composite shell, which can alleviate the volume effect. On the one hand, the carbon shell deposited by CVD on the surface of the composite cathode material improves the conductivity of the active material Li2S, on the other hand, as a barrier layer, the polysulfide produced during charge and discharge can be effectively confined to the inner shell. The shuttle effect of polysulfide was inhibited and the utilization rate of active substances was improved. The nanocrystalline structure design can effectively shorten the diffusion distance of lithium ion in the cathode material, thus improve the ion and electron transmission speed of the whole cathode material, and then improve the rate performance of the cathode material. At 0.2C charge-discharge, after the first discharge capacity was 1121.9mAh g-1100 cycles, the reversible capacity could be maintained as 804.2mAh g-1, the capacity retention rate was 71.7%, and the Coulomb efficiency was above 96%. At high test currents of 1C and 2C, its capacity can still reach 760.7 mAh.g-1 and 682.9 mAh.g-1.3) with nano-conductive carbon black particles as nucleating agent. The composite cathode material nano-Li2S@ C, which is similar to egg structure, was synthesized by the method of solution evaporation and CVD. The nano-conductive carbon black is egg yolk Li2S protein and the surface coating layer is eggshell. Under the synergistic action of nanocrystalline design and carbon coating, the electrode shows good cycling and rate performance. After the first discharge capacity of 1083.5 mAh g-1100 cycles, the reversible capacity of 0.2C charge-discharge can be maintained as 893.6mAh g-1, the capacity retention rate is 82.5, and the Coulomb efficiency is above 96%. Under the high test current of 1C and 2C, its capacity can still reach 763.5 mAh.g-1 and 625.8 mAh.g-1.
【學(xué)位授予單位】：浙江大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TM912

【相似文獻(xiàn)】

相關(guān)會議論文 前1條

1 李亞娟;郭軍;李光;劉素琴;;鋰硫電池放電產(chǎn)物多硫化鋰的理論研究[A];第29屆全國化學(xué)與物理電源學(xué)術(shù)年會論文集[C];2011年

相關(guān)博士學(xué)位論文 前5條

1 馬全新;鋰離子電池富鋰錳基正極材料與電極制備及改性研究[D];哈爾濱工業(yè)大學(xué);2017年

2 冀轉(zhuǎn);過渡金屬六氰配合物作為二次電池正極材料的應(yīng)用研究[D];中國地質(zhì)大學(xué);2017年

3 王星博;鋰離子電池富鋰正極材料的結(jié)構(gòu)表征與電化學(xué)性能研究[D];中國科學(xué)技術(shù)大學(xué);2017年

4 高鵬;鋰離子電池富鋰三元正極材料Li_(1+x)(NiCoMn)_yO_2的合成與性能研究[D];哈爾濱工業(yè)大學(xué);2016年

5 閔秀娟;磷酸釩鋰基正極材料的結(jié)構(gòu)與循環(huán)穩(wěn)定性研究[D];哈爾濱工業(yè)大學(xué);2017年

相關(guān)碩士學(xué)位論文 前10條

1 楊濤;硫化鋰正極材料的制備及電化學(xué)性能[D];浙江大學(xué);2017年

2 解二娟;鋰離子電池LiNi_xCo_yMn_zO_2正極材料的成分、合成工藝和納米銅摻雜研究[D];廣西大學(xué);2017年

3 羅垂意;無鈷鎳基正極材料理論計算與實驗改性研究[D];江西理工大學(xué);2017年

4 王曉艷;釩酸鈉與鐵氰化鐵鈉離子電池正極材料的合成及性能研究[D];合肥工業(yè)大學(xué);2017年

5 孫宇;鋰硫電池正極硫/碳微球復(fù)合材料的制備及改性研究[D];東北師范大學(xué);2017年

6 何林兵;復(fù)合正極材料及其在鋰離子電池中的應(yīng)用[D];浙江大學(xué);2017年

7 荊有澤;新型鋰/二氧化錳電池復(fù)合正極研究[D];天津大學(xué);2016年

8 楊芳凝;鋰離子電池富鋰層狀正極材料的研究[D];天津大學(xué);2016年

9 黃朋飛;富鋰層狀正極材料的制備及其改性研究[D];安徽工業(yè)大學(xué);2017年

10 王緒君;過渡金屬摻雜的鋰電池正極材料研究[D];青島大學(xué);2017年

，

本文編號：1835704