本文選題：鋰電池 + 鋰硫電池�。� 參考：《廈門大學(xué)》2014年碩士論文

【摘要】：鋰硫(Li-S)電池具有成本低廉、環(huán)境友好、能量密度高等優(yōu)點,是一種理想的下一代二次電池�，F(xiàn)有的硫正極及相應(yīng)的鋰硫電池存在電極材料導(dǎo)電性差、電化學(xué)反應(yīng)中間產(chǎn)物多硫化物溶解于電解液而引起的活性物質(zhì)利用率低和循環(huán)壽命短等諸多問題。如何固硫,提高電極材料活性物質(zhì)利用率,如何提高電極材料的電導(dǎo)率,提高循環(huán)穩(wěn)定性,是鋰硫電池研究開發(fā)的重要課題。 硫元素(S)容易與過渡金屬(M)形成穩(wěn)定的金屬硫化物(MS)。利用這一特性,在硫正極材料中加入過渡金屬或者直接利用金屬硫化物作為鋰電池正極材料是一種有效的固硫策略。在金屬硫化物中,硫化亞銅(Cu2S)材料導(dǎo)電性好,與硫化鋰(Li2S)晶體結(jié)構(gòu)極其相似,摩爾體積基本相等,并且其還原產(chǎn)物納米銅的導(dǎo)電性優(yōu)異。因此,硫化亞銅是一種非常具有潛力的鋰電池材料。 本論文研究了硫化亞銅作為鋰電池正極材料的電化學(xué)性能及其反應(yīng)機理,研究工作主要包括以下三個部分： (1)使用商品化的硫化亞銅(Cu2S)作為電極材料,測試了Cu2S半電池的電化學(xué)性能。該電極材料中含有Cu、CuS和Cu2S三種化合物,比容量為335mAh·g-1,200個充放電循環(huán)之后容量保持率為99.5%,具有優(yōu)異的循環(huán)性能。但是該材料在循環(huán)初期階段具有多種放電電壓平臺,不斷循環(huán)過程中電壓平臺發(fā)生變化。為了探討其中的電化學(xué)反應(yīng)機理,本論文利用XRD、XPS和TEM分析手段對硫化亞銅材料的充放電過程進行表征。分析結(jié)果表明,當(dāng)電極材料中含有足夠量的Cu時,如采用銅箔集流體或添加過量銅粉,不同形態(tài)的S元素在充放電循環(huán)過程中全部逐漸轉(zhuǎn)化為Cu2S晶體。此后充放電過程中只有一個單一的電化學(xué)反應(yīng),即Cu2S+Li(?)Li2S+Cu,表現(xiàn)為充放電過程中1.7V和1.85V兩個特別平坦的電壓平臺。 (2)研究了不同粒徑的Cu粉與S粉按不同比例反應(yīng)生成Cu2S的過程。研究發(fā)現(xiàn)當(dāng)銅硫摩爾比為3：1時,納米銅粉和硫粉反應(yīng)生成純度較高的Cu2S,該材料具有優(yōu)異的循環(huán)性能和固硫效果,100個循環(huán)容量保持率為83.3%；當(dāng)銅硫摩爾比為2：1和1：1時,納米銅粉和硫粉反應(yīng)生成物中含有CuS,材料的循環(huán)性能和固硫效果較差,100個循環(huán)容量保持率分別為33.3%和14.5%。 (3)通過采用銅箔集流體并在電極材料中添加銅粉的方式研究了鋰硫電池在充放電過程中Cu和S原位形成的硫化亞銅正極材料的電化學(xué)性能。該復(fù)合材料在0.5C倍率下充放電測試,首圈放電時單位硫質(zhì)量的比容量高達1614.1mAh·g1-,硫的利用率高達91%;在2C倍率下充放電循環(huán),第1000個循環(huán)的容量保持率為96.5%。 通過本論文的研究發(fā)現(xiàn),在鋰硫電池充放電過程中,用金屬Cu固定元素S元素從而在電極上形成導(dǎo)電性高的Cu2S材料,最終得到了一種硫利用率高、循環(huán)穩(wěn)定性及倍率性能優(yōu)異的含硫電極材料,說明Cu2S是一種非常具有潛力的儲能材料。
[Abstract]:Li-S battery is an ideal next-generation secondary battery because of its advantages of low cost, friendly environment and high energy density. The existing sulfur positive electrode and its corresponding lithium-sulfur battery have many problems, such as poor conductivity of electrode materials, low utilization rate of active substances and short cycle life due to the dissolution of polysulfide, an intermediate product of electrochemical reaction, in the electrolyte. How to fix sulfur, improve the utilization ratio of active materials of electrode materials, improve the conductivity of electrode materials and improve the cycle stability is an important subject in the research and development of lithium-sulfur batteries. Sulfur (S) is easy to form stable metal sulfides (MS) with transition metals (M). It is an effective strategy to fix sulfur by adding transition metal to sulfur cathode material or directly using metal sulfide as cathode material for lithium battery. Cuprous sulfide (Cu _ 2S) has good electrical conductivity and is similar to lithium sulfide (Li _ 2S) crystal structure. The molar volume of Cu _ 2S is similar to that of lithium sulfide (Li _ 2S), and the reduction product of Cu _ 2S has excellent electrical conductivity. Therefore, cuprous sulfide is a promising lithium battery material. In this paper, the electrochemical performance and reaction mechanism of cuprous sulfide as cathode materials for lithium batteries were studied. The research work mainly includes the following three parts: (1) the commercial copper sulfide (Cu2S) was used as electrode material. The electrochemical performance of Cu 2S semilayer was tested. The electrode material contains three kinds of compounds, Cu-CuS and Cu2S. The specific capacity of the electrode is 335mAh g-1200 charge-discharge cycles, the capacity retention rate is 99.5, and it has excellent cycling performance. However, the material has a variety of discharge voltage platforms in the initial stage of the cycle, and the voltage platform changes continuously during the cycle. In order to investigate the electrochemical reaction mechanism, the charge-discharge process of cuprous sulfide materials was characterized by XRDX XPS and TEM. The results show that when sufficient amount of Cu is contained in the electrode material, if copper foil is used to collect the fluid or the excess copper powder is added, all the S elements in different forms are transformed into Cu _ 2S crystals during the charging and discharging cycle. After that, there is only one single electrochemical reaction in the charge-discharge process. That is, Cu _ 2S Li (?) Li _ 2S Cu, which is a very flat voltage platform of 1.7V and 1.85V during charge and discharge. (2) the process of Cu _ 2S formation from Cu _ 2O _ 2 powder and S powder in different proportion has been studied. When the molar ratio of copper to sulfur is 3:1, Cu _ 2S with high purity can be obtained by the reaction of nano-copper powder and sulfur powder. The material has excellent cycling performance and sulfur fixation effect, and the retention rate of 100 cycles capacity is 83.3%. When the molar ratio of copper to sulfur is 2:1 and 1:1, Due to the existence of CuS in the reaction product of nano-copper powder and sulfur powder, the recycling performance and sulfur fixation efficiency of the materials are poor, and the retention of 100 cyclic capacity is 33.3% and 14.575% respectively. (3) the copper powder is added to the electrode material by using copper foil to collect fluid and add copper powder to the electrode material. The electrochemical properties of copper sulfide cathode materials formed in situ by Cu and S during charging and discharging of Lithium-Sulphur batteries were studied in this paper. The specific capacity per unit sulfur mass of the composite is as high as 1614.1mAh g _ 1-and the utilization ratio of sulfur is 91g ~ (-1) at the first cycle of discharge, and the capacity retention rate of the 1000th cycle is 96.5% at 2C rate. Through the research in this paper, it is found that in the process of charging and discharging of lithium-sulfur battery, Cu is used to fix the element S to form a high conductivity Cu _ 2S material on the electrode, and a kind of high sulfur utilization ratio is obtained. Cu2S is a potential material for energy storage because of its excellent cycle stability and rate performance.
【學(xué)位授予單位】：廈門大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2014
【分類號】：O614.121;TM912

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