本文選題：鋰離子電池 + 尖晶石錳酸鋰正極材料　； 參考：《湘潭大學(xué)》2014年碩士論文

【摘要】：尖晶石錳酸鋰材料因具有儲量資源豐富、環(huán)境友好、價(jià)格低廉、良好的熱穩(wěn)定性、適宜的充放電平臺、容易制備等優(yōu)點(diǎn)受到越來越多研究者的關(guān)注，成為當(dāng)前最具前景的鋰離子電池正極材料之一。然而，受制于其在高溫（55oC以上）下較差的循環(huán)性能，尖晶石錳酸鋰正極材料尚未得到大規(guī)模的工業(yè)化應(yīng)用。研究表明，導(dǎo)致這一現(xiàn)象的主要原因?yàn)镴ahn-Teller效應(yīng)，電解液中錳的溶解，工業(yè)化生產(chǎn)原料純度較低。針對尖晶石錳酸鋰正極材料的缺點(diǎn)，本文做了以下四點(diǎn)研究：首先使用FeF3·3H2O對尖晶石錳酸鋰合成原料MnSO4·H2O進(jìn)行除雜，制備高純硫酸錳；其次，用高純硫酸錳、硫酸鋁和碳酸鈉為沉淀劑，利用共沉淀法合成具有良好球形形貌的高端尖晶石錳酸鋰；然后，對尖晶石錳酸鋰進(jìn)行Al摻雜改性，利用共沉淀法合成球形尖晶石LiAlxMn2-xO4材料；最后，利用鋯酸鋰包覆對尖晶石錳酸鋰進(jìn)行改性，合成鋯酸鋰包覆的球形尖晶石錳酸鋰材料。主要工作如下： (1)基于FeF3·3H2O中的氟離子可以沉淀溶液中的鈣、鎂離子，鐵離子可以與鉀、鈉離子生成易沉淀的硫酸配鹽，多余的鐵離子水解形成的Fe(OH)3具有顯著的絮凝效果，因此將FeF3·3H2O作為一種新型硫酸錳除雜劑，通過調(diào)整溶液的pH值，使鈣、鎂、鉀、鈉離子先后沉淀，從而分離普通硫酸錳中較難分離的鈣、鎂、鉀、鈉離子。除雜后的高純硫酸錳產(chǎn)品中，鈣、鎂、鉀、鈉離子含量均低于100ppm，鐵離子含量低于10ppm，得到的產(chǎn)品可以達(dá)到電池級或電子級錳基原料生產(chǎn)所需的高純硫酸錳對鈣、鎂、鉀、鈉離子純度的要求。 (2)以高純硫酸錳和碳酸鈉為沉淀劑，氨水為絡(luò)合劑，利用共沉淀法合成了具有良好球形形貌的碳酸錳前驅(qū)體，并對反應(yīng)中的pH值、攪拌速率、溫度、氨的濃度四個條件進(jìn)行了討論。之后將前驅(qū)體與碳酸鋰混合、煅燒，合成了球形度良好的高端尖晶石錳酸鋰。測試結(jié)果表明，合成的高端尖晶石錳酸鋰振實(shí)密度高，首次放電容量和循環(huán)性能均有明顯優(yōu)勢。 (3)以高純硫酸錳、硫酸鋁和碳酸鈉為沉淀劑，氨水為絡(luò)合劑，利用共沉淀法合成了具有良好球形形貌的尖晶石LiAlxMn2-xO4系列材料并對其電化學(xué)性能進(jìn)行了研究。研究表明分子式為LiAl0.06Mn1.94O4的材料具有最好的高溫循環(huán)穩(wěn)定性能。在55oC、1C倍率條件下，該樣品100次充放電后的放電容量仍有113.9mAh g1，容量保持率高達(dá)97.0%。 (4)以鋯酸鋰為包覆層，成功合成了鋯酸鋰包覆的球形尖晶石錳酸鋰。實(shí)驗(yàn)結(jié)果表明基于鋯酸鋰良好的鋰離子傳導(dǎo)性和化學(xué)惰性，以鋯酸鋰為包覆層可有效阻止電解液中HF對錳的溶解，同時不阻礙鋰離子的嵌入/脫出過程。電化學(xué)測試表明包覆量為3wt.%的材料具有最好的常溫和高溫電化學(xué)性能，25oC,1C倍率條件下，首次放電容量為126.7mAh g1，100次充放電后容量保持率為99.0%；55oC,1C倍率條件下，首次放電容量為129.5mAh g1，100次充放電后容量保持率為90.2%，并且電荷轉(zhuǎn)移阻抗Rct值僅為34.2，，均優(yōu)于未包覆錳酸鋰材料。
[Abstract]:Spinel lithium manganese dioxide is one of the most promising cathode materials for lithium ion batteries because of its abundant reserves, friendly environment, low price, good thermal stability, suitable charging and discharging platform and easy preparation. However, it is subject to the poor evidence-based process under high temperature (above 55oC). The study shows that the main cause of this phenomenon is Jahn-Teller effect, the dissolution of manganese in the electrolyte and the low purity of the raw materials in industrial production. The following four points are studied in this paper: first of all, the use of Fe F3. 3H2O is used to prepare high purity manganese sulfate by removing impurities from spinel lithium manganate synthetic material MnSO4 H2O. Secondly, high purity Spinel Manganese manganese oxide with good spherical morphology is synthesized with high purity manganese sulfate, aluminum sulfate and sodium carbonate as precipitants. Then, Al doped spinel lithium manganese acid is modified by Al and co precipitation method is used. Spherical spinel LiAlxMn2-xO4 material; finally, lithium manganese zirconate was used to modify spinel lithium manganate, and lithium zirconate coated spinel lithium manganese dioxide was synthesized. The main work is as follows:
(1) the fluorine ions based on FeF3 / 3H2O can precipitate calcium, magnesium ions in the solution, iron ions can produce precipitate sulphuric acid with potassium and sodium ions, and Fe (OH) 3, formed by the hydrolysis of excess iron ions, has significant flocculation effect. Therefore, FeF3 / 3H2O is used as a new type of manganese sulphate impurity removing agent, and by adjusting the pH value of the solution, calcium, magnesium, potassium is made. Sodium ions are precipitated successively to separate calcium, magnesium, potassium and sodium ions, which are more difficult to separate from ordinary manganese sulfate. In the high purity manganese sulphate products, the content of calcium, magnesium, potassium and sodium ions is lower than 100ppm, and the content of iron ions is lower than 10ppm. The products obtained can reach the high purity manganese sulfate for the production of battery grade or electronic grade manganese base. The requirements for the purity of potassium and sodium ions.
(2) using high pure manganese sulfate and sodium carbonate as precipitant and ammonia as complexing agent, the precursor of manganese carbonate with good spherical morphology was synthesized by coprecipitation method. The pH value, stirring rate, temperature and ammonia concentration in the reaction were discussed. The precursor was mixed with lithium carbonate and calcined, and the high end of the sphericity was synthesized. Spinel lithium manganate. The test results show that the synthetic high end spinel lithium manganese oxide has high density of compaction, and has obvious advantages in the first discharge capacity and cycle performance.
(3) with high purity manganese sulfate, aluminum sulfate and sodium carbonate as precipitant and ammonia as complexing agent, the spinel LiAlxMn2-xO4 series materials with good spherical morphology were synthesized by coprecipitation method and their electrochemical properties were studied. The study shows that the material with molecular formula for LiAl0.06Mn1.94O4 has the best high temperature cycling stability. In 55oC, Under the condition of 1C ratio, the discharge capacity of the sample after 100 charge and discharge is still 113.9mAh G1, and the capacity retention rate is as high as 97.0%.
(4) lithium zirconate coated lithium manganese zirconate was successfully synthesized with lithium zirconate as coating layer. The experimental results show that lithium zirconate is good in lithium ion conductivity and chemical inertness. Lithium zirconate as coating can effectively prevent the dissolution of manganese in the electrolyte, and it does not obstruct the insertion / release process of lithium ion. The electrochemical test shows that lithium ion is not obstructed. The material with a coating amount of 3wt.% has the best electrochemical and high temperature electrochemical properties. Under the condition of 25oC and 1C multiplying, the capacity retention rate of the first discharge capacity of 126.7mAh g1100 is 99%; 55oC and 1C multiplying condition, the initial discharge capacity is 90.2% after 129.5mAh g1100 charge discharge, and the charge transfer impedance Rct is 90.2%. The value is only 34.2, which is better than that of the uncoated lithium manganese material.
【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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