本文選題：二次電池　切入點(diǎn)：負(fù)極　出處：《中國科學(xué)院大學(xué)(中國科學(xué)院物理研究所)》2017年博士論文　論文類型：學(xué)位論文

【摘要】：隨著人們對能源需求的增長和清潔能源的開發(fā),能源儲存和轉(zhuǎn)化越來越受到人們的關(guān)注。二次電池因其具有較高的能量密度和功率密度等優(yōu)點(diǎn),適用于大規(guī)模儲能。鋰離子電池和鈉離子電池是目前二次電池研究發(fā)展的主要研究方向。隨著鋰離子電池在便攜式電子設(shè)備方面的應(yīng)用和在電動汽車方面的推廣,鋰的需求量在不斷增加,再加上地球上鋰資源的有限性和局域性,鋰的價格在不斷上升。由于鈉具有與鋰相似的物理化學(xué)性質(zhì),儲量豐富,成本低廉,因此鈉離子電池在大規(guī)模儲能方面具有可持續(xù)發(fā)展的優(yōu)勢。另一方面,由于鈉離子具有比鋰離子更大的離子半徑(0.97?vs 0.68?),所以部分在鋰離子體系中電化學(xué)性能優(yōu)異的材料不能直接用于鈉離子電池。探索電化學(xué)性能優(yōu)異的電極材料并研究其機(jī)理對推動鈉離子電池的發(fā)展和應(yīng)用具有重要意義。本文研究碳材料和鈦基氧化物作二次電池負(fù)極的電化學(xué)性能,并對其結(jié)構(gòu)進(jìn)行相應(yīng)表征。以不同濃度的Na-BP-DME溶液作為還原劑將不同數(shù)量的鈉離子化學(xué)嵌入進(jìn)高定向熱解石墨(HOPG)中,避免了電化學(xué)嵌鈉時電解液分解沉積對確定樣品中Na:C原子比的干擾。結(jié)合X射線衍射(XRD)、掃描透射電子顯微鏡(STEM)、傅里葉變換紅外(FTIR)光譜和Raman光譜等結(jié)構(gòu)表征分析發(fā)現(xiàn),在醚類溶劑中,鈉離子與溶劑分子共嵌入石墨層間,經(jīng)過一系列階的轉(zhuǎn)變過程,形成三元插層化合物(GIC)。結(jié)合電感耦合等離子體光譜(ICP)和熱重分析,確定出最終形成的一階相產(chǎn)物的組分為Na(DME)2C26。FTIR和Raman光譜證實(shí)了鈉離子、溶劑分子、石墨之間的相互作用。這種相互作用有利于保持嵌入過程中石墨結(jié)構(gòu)的完整,提高實(shí)驗(yàn)電池的循環(huán)穩(wěn)定性。此外,我們還對生成的三元GIC在空氣中的穩(wěn)定性進(jìn)行了研究。將均勻混合的明膠與檸檬酸鎂在600~900℃的惰性氣氛中熱解得到一系列多孔含氮碳材料。檸檬酸鎂熱解形成的MgO作為模板保證了所得介孔碳具有孔徑分布小且均一的特點(diǎn)。含氮介孔碳中的氮原子主要以吡啶氮、吡咯氮和氧化氮的形式存在。石墨化氮的缺失與制備過程中檸檬酸鎂的存在抑制了明膠的熱交聯(lián)過程有關(guān)。電化學(xué)實(shí)驗(yàn)結(jié)果表明,這些碳材料具有良好的電化學(xué)性能,材料的電化學(xué)性能受氮摻雜和孔結(jié)構(gòu)的雙重影響。在700°C下獲得的介孔碳材料在首次循環(huán)中的可逆儲鈉容量達(dá)到360 mAh g-1,且具有良好的循環(huán)穩(wěn)定性和倍率性能。通過溶膠凝膠法(sol-gel)合成了層狀材料A_2TiO_3(A=Li/Na)。Li_2TiO_3和Na_2TiO_3分別具有165和274 mAh g-1的可逆儲鋰容量,循環(huán)穩(wěn)定性較好。結(jié)合XRD和Raman光譜技術(shù)對材料結(jié)構(gòu)進(jìn)行分析發(fā)現(xiàn),充放電過程中Li_2TiO_3的結(jié)構(gòu)能夠可逆地轉(zhuǎn)變,Li+可能進(jìn)入材料四面體間隙位置,并形成有序的排布;Na_2TiO_3在鋰離子電池電解液中會發(fā)生離子交換和結(jié)構(gòu)轉(zhuǎn)變,形成陽離子混排的層狀結(jié)構(gòu),電化學(xué)性能更好。
[Abstract]:With the increasing demand for energy and the development of clean energy, energy storage and conversion have attracted more and more attention. Secondary batteries have the advantages of high energy density and power density. Lithium ion battery and sodium ion battery are the main research direction of secondary battery research and development at present. With the application of lithium ion battery in portable electronic equipment and the popularization of electric vehicle, The increasing demand for lithium, coupled with the limited and localized nature of lithium resources on Earth, has led to a rising price of lithium, because sodium has physical and chemical properties similar to lithium, is rich in reserves and low in cost. Therefore, sodium ion battery has the advantage of sustainable development in large-scale energy storage. On the other hand, because sodium ion has a larger ion radius than lithium ion, 0.97? Vs 0.68? Therefore, some materials with excellent electrochemical performance in lithium ion system can not be directly used in sodium ion batteries. Exploring the electrode materials with excellent electrochemical performance and studying its mechanism are important for promoting the development and application of sodium ion batteries. In this paper, the electrochemical properties of carbon materials and titanium-based oxides used as anode of secondary battery are studied. The structure was characterized by using different concentrations of Na-BP-DME solution as reducing agent to embed different amounts of sodium ion chemistry into highly oriented pyrolytic graphite (HOPG). The interference of electrolytic solution decomposition deposition in determining the atomic ratio of Na:C in the sample was avoided by electrochemical sodium intercalation. The results of X-ray diffraction (XRD), scanning transmission electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy were used to characterize and analyze the structure of the sample. In ether solvents, sodium ions and solvent molecules are intercalated into graphite layers, and a series of transition processes are carried out to form ternary intercalation compounds (GICs), which are combined with inductively coupled plasma spectroscopy (ICP) and thermogravimetric analysis (TGA). Na(DME)2C26.FTIR and Raman spectra show that the interaction among sodium ions, solvent molecules and graphite is beneficial to the integrity of graphite structure in the intercalation process. Improve the cycle stability of the experimental battery. In addition, We also studied the stability of ternary GIC in air. A series of porous nitrogen-containing carbon materials were obtained by pyrolysis of homogeneously mixed gelatin and magnesium citrate in an inert atmosphere of 600,900 鈩，

本文編號：1616450