發(fā)布時(shí)間：2018-04-08 07:42

  本文選題：鋰離子電池　切入點(diǎn)：硅顆粒尺寸　出處：《華中師范大學(xué)》2017年碩士論文

【摘要】：能源危機(jī)和環(huán)境污染是人類(lèi)亟待解決的重要問(wèn)題,為此世界各國(guó)都在為此努力,鋰離子電池作為一種新型清潔無(wú)污染能源,備受關(guān)注,成為科技寵兒。人們致力于研究開(kāi)發(fā)容量大,循環(huán)壽命長(zhǎng)和安全性高的新型鋰離子電池,其中關(guān)鍵是電極活性材料。因?yàn)楣璨牧舷鄬?duì)于其他電極材料有較大的理論容量(4200mAhg-l),成為研究熱點(diǎn)。但是硅材料在嵌脫鋰過(guò)程中發(fā)生巨大的體積膨脹,結(jié)構(gòu)受到破壞,出現(xiàn)崩塌、粉化現(xiàn)象,阻礙了電子的傳輸,也容易造成電極短路,最終致使容量發(fā)生巨大損失,減小了循環(huán)壽命。為了解決這些問(wèn)題,人們做出很多努力,采用了很多方法,其中減小硅顆粒尺寸,并設(shè)計(jì)多孔結(jié)構(gòu)是有效手段之一。減小硅顆粒尺寸,可以增加材料的比表面積,減小鋰離子的脫嵌深度,縮短離子的擴(kuò)散路徑,并且削弱充放電時(shí)的電極極化現(xiàn)象;多孔結(jié)構(gòu)的孔隙可以為充放電過(guò)程中的體積變化提供緩沖空間,減小結(jié)構(gòu)破裂。為了實(shí)現(xiàn)硅材料的結(jié)構(gòu)修飾,本文首先利用球磨法減小硅顆粒尺寸,在此基礎(chǔ)上,通過(guò)制備多孔結(jié)構(gòu)來(lái)提高作為鋰離子電池負(fù)極材料的性能。同時(shí)利用物鋰表征手段,研究了材料的組成成分和形貌,通過(guò)電化學(xué)性能測(cè)試,探究了充放電原理和循環(huán)特性。具體研究?jī)?nèi)容如下:一、減小硅顆粒的尺寸。因?yàn)楣桀w粒結(jié)構(gòu)比較脆,首先進(jìn)行手動(dòng)研磨,然后采用機(jī)械球磨。機(jī)械球磨時(shí)間我們?nèi)×?12h、20h、28h三個(gè)時(shí)間點(diǎn),通過(guò)電化學(xué)性能測(cè)試,球磨28h的樣片顆粒大約為1-2um;與200目硅粉相比,容量損失減小,循環(huán)性能改善。這是因?yàn)轭w粒尺寸減小縮短了離子擴(kuò)散路徑,有利于離子傳輸,提高儲(chǔ)鋰特性。二、制備多孔結(jié)構(gòu)的硅材料。利用金屬輔助刻蝕法,在硅顆粒表面刻蝕成多孔結(jié)構(gòu),其中AgN03/HF腐蝕液中的Ag離子在刻蝕過(guò)程中發(fā)生還原反應(yīng),起到催化效應(yīng),AgN03濃度影響材料形貌。其中0.10molL-1的AgN03濃度下制備的樣品循環(huán)性能最佳,容量損失最少。這是因?yàn)槎嗫捉Y(jié)構(gòu)增加了與電解液的接觸,并且孔隙為體積變化提供了緩沖空間,減少了結(jié)構(gòu)破壞和容量損失,有利于儲(chǔ)鋰。
[Abstract]:Energy crisis and environmental pollution are important problems to be solved urgently. For this reason, many countries all over the world are making great efforts to this end. Lithium ion batteries, as a new clean and pollution-free energy, have attracted much attention and become the favorite of science and technology.A new type of lithium ion battery with high capacity, long cycle life and high safety has been developed, among which the key is electrode active material.Because silicon has a large theoretical capacity of 4200mAhg-ln compared with other electrode materials, it has become a research hotspot.However, in the process of intercalation of lithium ion, the silicon material has a huge volume expansion, the structure is destroyed, the structure is destroyed, the phenomenon of collapse and pulverization occurs, which hinders the transmission of electrons, and also easily causes the electrode to short circuit, resulting in a huge loss of capacity.The cycle life is reduced.In order to solve these problems, a lot of efforts have been made and many methods have been adopted. One of the effective methods is to reduce the size of silicon particles and design porous structures.Reducing the size of silicon particles can increase the specific surface area of the material, reduce the depth of deintercalation of lithium ion, shorten the diffusion path of ions, and weaken the polarization phenomenon of the electrode during charge and discharge.The pore of porous structure can provide buffer space for the volume change during charge and discharge, and reduce the structure rupture.In order to realize the structural modification of silicon materials, the size of silicon particles was reduced by ball milling method. On the basis of this, the porous structure was prepared to improve the performance of anode materials for lithium ion batteries.At the same time, the composition and morphology of the material were studied by means of lithium. The principle of charge and discharge and the characteristics of cycle were investigated by electrochemical performance test.The main contents are as follows: first, reduce the size of silicon particles.Because the structure of silicon particles is relatively brittle, the first hand grinding, and then the mechanical ball milling.The mechanical milling time is 12 h ~ 20 h ~ 28 h, and the sample size is about 1 ~ 2 um.Compared with 200 mesh silicon powder, the volume loss is reduced and the cycling performance is improved.This is because the reduction of particle size shortens the ion diffusion path, facilitates ion transport and improves the lithium storage characteristics.Secondly, porous silicon materials are prepared.The porous structure was etched on the surface of silicon particles by metal-assisted etching method. The Ag ion in the AgN03/HF etching solution was reduced during the etching process, which played a catalytic effect on the morphology of the material by the concentration of AgN03.The sample prepared under the AgN03 concentration of 0.10molL-1 has the best cycling performance and the least capacity loss.This is because the porous structure increases the contact with the electrolyte, and the pore provides buffer space for volume change, which reduces the damage of the structure and the loss of capacity, which is favorable for lithium storage.
【學(xué)位授予單位】：華中師范大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類(lèi)號(hào)】：TM912

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本文編號(hào)：1720685