本文選題：鋰硫電池 + 正極材料��； 參考：《湘潭大學(xué)》2014年碩士論文

【摘要】：鋰硫電池被認為是最具開發(fā)潛力的電池體系之一，理論能量密度高達2600Wh/kg。單質(zhì)硫是目前已知比容量最高的正極材料(理論比容量為1675mAh/g)，而且硫在自然界中儲量豐富，成本低廉，同時具有低毒性，環(huán)境友好。但是硫正極在應(yīng)用中存在著致命的缺點：單質(zhì)硫不導(dǎo)電以及電化學(xué)反應(yīng)過程中放電產(chǎn)物溶于電解液，導(dǎo)致活性物質(zhì)利用率低、電極循環(huán)穩(wěn)定性差，嚴重制約了鋰硫電池的發(fā)展。本論文在充分調(diào)研的基礎(chǔ)上，以具有高導(dǎo)電性、高比表面積的泡沫鎳為基體與硫復(fù)合，對硫鎳一體化正極的制備及性能的優(yōu)化展開了系統(tǒng)的研究。本學(xué)位論文的創(chuàng)新性研究成果如下： (1)采用熱蒸法將硫包覆到泡沫鎳基體的多孔結(jié)構(gòu)中，制備硫鎳正極材料。通過SEM、XRD對材料進行結(jié)構(gòu)及成分表征，通過模擬電池的組裝進行電化學(xué)性能測試。結(jié)果表明，正極的三維網(wǎng)絡(luò)結(jié)構(gòu)保持良好，活性物質(zhì)分布均勻，且以硫鎳化合物的形式存在。在前20次循環(huán)內(nèi)，電池內(nèi)部電化學(xué)反應(yīng)良好，但是隨著循環(huán)次數(shù)的進一步增加，活性物質(zhì)會從基體剝離，造成正極結(jié)構(gòu)損傷，容量衰減，庫倫效率偏低。 (2)為了穩(wěn)固正極結(jié)構(gòu)，并發(fā)揮單質(zhì)硫理論比容量高的優(yōu)勢，采用化學(xué)法制備硫鎳正極材料。結(jié)果表明，活性物質(zhì)以單質(zhì)硫的形式均勻包覆在泡沫鎳骨架表面，且有少量大顆粒狀硫附于表層。其首次放比電容量較高，具有典型的充放電平臺，庫倫效率接近100%，經(jīng)100次循環(huán)后容量保持率為75%。但是表層大顆粒硫的脫落會造成循環(huán)使用過程中容量的波動，不利于實際應(yīng)用。 (3)對化學(xué)法制備硫鎳正極材料進行后續(xù)熔硫處理，目的在于消除表層大顆粒硫?qū)ρh(huán)性能的影響。結(jié)果表明，活性物質(zhì)硫高度分散在基體的多孔結(jié)構(gòu)中，增加了電化學(xué)反應(yīng)過程中微反應(yīng)場所，有效抑制放電產(chǎn)物溶解，，循環(huán)可逆性好。經(jīng)不同的倍率充放電循環(huán)110次后容量保持率高達95%。而且隨著循環(huán)的進行，電極的界面阻抗及鋰離子擴散阻抗均明顯下降。 綜上所述，本論文以傳統(tǒng)集流體材料泡沫鎳為基體制備的硫鎳正極材料，即硫鎳一體化正極，可以直接用于電池裝配，無需添加粘結(jié)劑、導(dǎo)電劑和分散溶劑進行制漿、涂布，工藝簡單�；瘜W(xué)-熔硫法制備的一體化正極具有高比表面積的穩(wěn)定結(jié)構(gòu)，極大提高了活性物質(zhì)的利用率，可以有效抑制多硫化物的溶解，電化學(xué)反應(yīng)可逆性良好，為鋰硫電池新型正極材料的設(shè)計提供了實驗依據(jù)。
[Abstract]:Lithium-sulfur batteries are considered as one of the most promising battery systems with theoretical energy density as high as 2600Wh/ kg. Elemental sulfur is the most known cathode material with the highest specific capacity (theoretical specific capacity is 1675mAh/ g / g), and sulfur in nature is rich in reserves, low cost, low toxicity and environmentally friendly. However, sulfur positive electrode has some fatal disadvantages in application: simple sulfur nonconductivity and discharges dissolved in electrolyte during electrochemical reaction, which leads to low utilization of active substances and poor electrode cycle stability, which seriously restricts the development of lithium-sulfur batteries. On the basis of full investigation, the preparation and performance optimization of nickel foam with high conductivity and high specific surface area were studied systematically in this paper. The innovative research results of this dissertation are as follows: 1) the sulfur was coated into the porous structure of the foamed nickel matrix by thermal evaporation to prepare the nickel sulfide cathode material. The structure and composition of the materials were characterized by SEM XRD, and the electrochemical properties were tested by the assembly of simulated batteries. The results show that the positive electrode has a good three-dimensional network structure and a uniform distribution of active substances, and exists in the form of sulfur and nickel compounds. During the first 20 cycles, the electrochemical reaction in the battery was good, but with the further increase of the cycle times, the active substances would be stripped from the matrix, resulting in the damage of the structure of the positive electrode, the capacity attenuation, and the low efficiency of the Coulomb. In order to stabilize the structure of positive electrode and give full play to the advantage of high specific capacity of elemental sulfur theory, nickel sulphide cathode material was prepared by chemical method. The results showed that the active substances were uniformly coated on the surface of the foamed nickel skeleton in the form of elemental sulfur, and a small amount of large granular sulfur was attached to the surface layer. Its first discharge capacity is high, it has a typical charging and discharging platform, the Coulomb efficiency is close to 100, and the capacity retention rate is 75 after 100 cycles. However, the falling off of large particles of sulfur in the surface will cause the fluctuation of capacity in the process of recycling, which is not conducive to practical application. In order to eliminate the influence of large particles of sulfur on the cycling performance of nickel and sulfur cathode materials prepared by chemical method, the sulfur melting treatment is carried out. The results show that the active sulfur is highly dispersed in the porous structure of the matrix, which increases the micro-reaction sites in the electrochemical reaction process, effectively inhibits the dissolving of the discharge products, and has good circulation reversibility. After 110 cycles at different rates of charge and discharge, the capacity retention rate is as high as 95%. The interfacial impedance and lithium ion diffusion impedance of the electrode decreased with the cycle. To sum up, the traditional fluid-collecting material, nickel foam as the substrate, can be directly used in battery assembly without adding binder, conductive agent and dispersing solvent for pulping and coating, which is the integral positive electrode of sulfur and nickel, which can be used in battery assembly directly. The process is simple. The integrative positive electrode prepared by chemical-melting sulfur method has a stable structure with high specific surface area, which greatly improves the utilization ratio of active substances, effectively inhibits the dissolution of polysulfide, and has good reversibility in electrochemical reaction. It provides experimental basis for the design of new cathode materials for lithium-sulfur batteries.
【學(xué)位授予單位】：湘潭大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2014
【分類號】：TM912

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