本文選題：磷酸鐵鋰 + 磷酸鐵�。� 參考：《長沙理工大學(xué)》2011年碩士論文

【摘要】：磷酸鐵鋰晶體結(jié)構(gòu)穩(wěn)定、比容量高、放電平臺平穩(wěn)和循環(huán)壽命長,是鋰離子動力電池的首選正極材料之一。作為動力電池關(guān)鍵材料其存在三個缺陷:一是電導(dǎo)率低,導(dǎo)致材料的比容量和倍率性能都難以發(fā)揮;二是振實密度較低,這在很大程度上面影響了其能量密度上面的發(fā)揮;三是生產(chǎn)過程中單位能耗高,廢氣排放量大。本文針對上述缺陷,設(shè)計了磷酸鐵鋰的改性方案。以三價鐵鹽取代二價鐵鹽為原料,制備前驅(qū)體磷酸鐵,重點研究控制前驅(qū)體的粒度和形貌的方法與碳熱還原制備磷酸鐵鋰的工藝參數(shù)。在上述基礎(chǔ)上對磷酸鐵鋰進(jìn)行二氧化鈦的摻雜改性,以提高其導(dǎo)電率。本文工作可以分為下面四個部分: (1)沉淀法制備球形磷酸鐵。通過研究不同鐵源、水浴溫度和PH對制備過程的影響,選擇氯化鐵和磷酸體系作為反應(yīng)試劑,在高于90℃的條件下,在PH=0.9時可以制備出粒度大小在1~2μm,形貌類球形的磷酸鐵。 (2)表面活性劑輔助形貌控制生長磷酸鐵。以zeta電位為研究依據(jù),分別引入小分子表面活性劑和高聚物表面活性劑。研究表明,小分子SDS(十二烷基硫磺鈉)表面活性劑改性以后,顆粒表面光滑,顆粒呈類球形,有利于提高磷酸鐵鋰的振實密度;高聚物表面活性劑PVP(聚乙烯基吡咯烷)改性磷酸體,顆粒呈片層狀,并存在團(tuán)聚現(xiàn)象。 (3)碳熱還原法制備磷酸鐵鋰。研究了組成、分散劑、還原劑和燒成制度等主要參數(shù)對磷酸鐵鋰結(jié)構(gòu)和性能影響。鋰鐵比為1.02:1,酒精介作分散為質(zhì),葡萄糖為還原劑,在750℃溫度下燒結(jié)12小時為最優(yōu)工藝條件。研究表明,乙炔黑作為碳源,磷酸鐵鋰在0.1C的初始容量可達(dá)到152 mAh/g,但在0.2C時的乙炔黑樣品比容量降至125 mAh/g左右,而葡萄糖樣品卻依然保持130 mAh/g。 (4)二氧化鈦摻雜磷酸鐵鋰復(fù)合材料。在葡萄糖碳熱還原法制備磷酸鐵鋰的基礎(chǔ)上,本文引入二氧化鈦作為摻雜物,研究了不同鈦含量對磷酸鐵鋰晶體結(jié)構(gòu)的影響,優(yōu)化了摻雜二氧化鈦以后的磷酸鐵鋰產(chǎn)物,最終提高了磷酸鐵鋰的初始容量和倍率容量。經(jīng)過優(yōu)化的樣品首次充電容量和放電容量分別達(dá)到了157.9 mAh/g和155.2 mAh/g。1C倍率循環(huán)100次以后,比容量依然達(dá)到130 mAh/g。CV(循環(huán)伏安)和EIS(交流阻抗)測試表明,二氧化鈦摻雜磷酸鐵鋰復(fù)合材料極化和電阻均明顯降低。
[Abstract]:Lithium iron phosphate is one of the preferred cathode materials for lithium-ion power batteries due to its stable structure, high specific capacity, stable discharge platform and long cycle life. As the key material of power battery, there are three defects: one is the low conductivity, the other is that the specific capacity and rate performance of the material are difficult to play, the second is the low vibrational density, which affects the exertion of the energy density to a great extent. Third, the unit energy consumption in the production process is high, the exhaust gas emission is big. In view of the above defects, the modification scheme of lithium iron phosphate was designed in this paper. The precursor ferric phosphate was prepared by replacing divalent ferric salt with trivalent iron salt. The methods of controlling the particle size and morphology of the precursor and the technological parameters of preparing lithium iron phosphate by carbothermal reduction were studied. On the basis of above mentioned above, lithium iron phosphate was doped with titanium dioxide to improve its conductivity. This work can be divided into the following four parts: (1) preparation of spherical iron phosphate by precipitation method. By studying the effects of different Tie Yuan, water bath temperature and PH on the preparation process, ferric chloride and phosphoric acid system were selected as reaction reagents under conditions above 90 鈩，

本文編號：2072947