本文關鍵詞：碳熱還原法制備磷酸鐵鋰及其改性研究　出處：《長沙理工大學》2014年碩士論文　論文類型：學位論文

  更多相關文章： 磷酸鐵 磷酸鐵鋰 碳熱還原法 陽離子摻雜

【摘要】：碳熱還原法(CTR)由高溫固相法衍生而來,且其操作簡單,以三價鐵為鐵源其產物更為均勻而且不需要采用FeC204.H2O因而價格便宜。用于CTR法的鐵源有很多,如Fe(OH)3、Fe2O3、Fe3O4、FePO4以及復合鐵源等。其中,FePO4既能夠提供鐵源也能夠提供磷源,且在FePO4轉變成LiFePO4的過程中二者的結構相似。因此,通過控制FePO4的粒徑和形貌有望實現(xiàn)對LiFePO4的粒徑和形貌的有效調控。本文先通過沉淀法制得FePO4,再以其為原料合成LiFePO4,優(yōu)化了CTR法合成LiFePO4的條件并系統(tǒng)地研究了FePO4制備的條件對其結構和形貌的影響以及對后續(xù)制備的LiFePO4的影響。用XRD、ICP、SEM和TEM表征FePO4和LiFePO4的組成、結構以及形貌,研究其構效規(guī)律。采用藍電、電化學工作站對LiFePO4的充放電特性及其交流阻抗和循環(huán)伏安特性進行測定,研究鋰離子脫嵌動力學。沉淀法制備FePO4。研究了在該方法中反應物、水浴溫度、pH值、濃度、攪拌速度以及添加劑對制備的FePO4粒度、形貌和結晶性的影響。研究表明：采用FeSO4·7H2O-NH4H2PO4為反應物有助于類球形的磷酸鐵的形成。在該體系中,溫度為90℃、pH為1.7左右、攪拌速度采用400r/min、表面活性劑為SDS時能夠得到粒徑為20-80nm且結晶良好、分散均勻的FePO4粉末。CTR法合成LiFePO4。選取Li2CO3、C6H12O6以及FePO4為原料,分別研究了燒結工藝、鋰鐵比、碳用量、分散介質以及前驅體的工藝條件對CTR法制備LiFePO4的影響。研究表明：在Li:Fe為1.02,19wt%的葡萄糖用量,水做分散劑,750℃下燒結12h制備的LiFePO4的首次可逆容量最高,大倍率性能最優(yōu),同時極化小,循環(huán)性能好。該樣品在0.1、0.2和0.5C下的首次放電比容量依次為151、150和144mAh/g。陽離子摻雜改性LiFePO4。首先選取了鎂、釩以及鎳作為摻雜物對最終制備的磷酸鐵鋰的影響進行了探討。其中,選用V2Os為摻雜劑能夠最有效的實現(xiàn)對LiFePO4的放電比容量以及穩(wěn)定性的優(yōu)化。結果表明V的用量為3%的樣品的電’化學性能最優(yōu),0.1C下的首次可逆容量為151 mAh/g,并且循環(huán)100次后沒有明顯的降低。
[Abstract]:Carbothermal reduction method (CTR) is derived from high temperature solid state method and its operation is simple. Taking trivalent iron as Tie Yuan's product is more uniform and it is cheaper to use FeC204.H2O. For example, there are a lot of Tie Yuan used in CTR method, such as FeOHZ3Fe2O3. Fe3O4FePO4 and compound Tie Yuan, among them, FePO4 can not only provide Tie Yuan but also provide phosphorus source. And in the process of FePO4 to LiFePO4, the structure of the two is similar. By controlling the particle size and morphology of FePO4, it is expected to achieve the effective control of the particle size and morphology of LiFePO4. Firstly, FePO4 was prepared by precipitation method. Then LiFePO4 was synthesized by using it as raw material. The conditions for the synthesis of LiFePO4 by CTR method were optimized, and the effects of the conditions of FePO4 preparation on the structure and morphology of FePO4 and on the subsequent LiFePO4 preparation were studied systematically. XRD was used. The composition, structure and morphology of FePO4 and LiFePO4 were characterized by ICP-SEM and TEM. The charge-discharge characteristics, AC impedance and cyclic voltammetry of LiFePO4 were measured by electrochemical workstation. The kinetics of lithium ion deintercalation was studied. FePO _ 4 was prepared by precipitation method. In this method, the reactants, water bath temperature, pH value, concentration, stirring speed and the particle size of FePO4 prepared by additives were studied. The effect of morphology and crystallinity. The results show that FeSO4 路7H _ 2O -NH _ 4H _ 2PO _ 4 is used as reactant to facilitate the formation of spheroidal ferric phosphate. In this system, the temperature is 90 鈩，

本文編號：1407146