本文選題：熔鹽法　切入點(diǎn)：鋰離子電池　出處：《武漢理工大學(xué)》2010年博士論文

【摘要】： 鋰離子電池作為清潔高效的能源已經(jīng)廣泛應(yīng)用于照相機(jī)、手機(jī)、筆記本電腦等便攜式移動(dòng)設(shè)備,并逐漸應(yīng)用于電動(dòng)汽車。一直以來,昂貴的價(jià)格制約著鋰離子電池大規(guī)模車用化的發(fā)展。降低鋰離子電池成本的關(guān)鍵是研究開發(fā)價(jià)格低廉的新材料以及采用簡(jiǎn)單易行的低成本制備方法。新材料的開發(fā)到最終應(yīng)用往往需要數(shù)十年的時(shí)間,而制備工藝的優(yōu)化通常能應(yīng)用于多種材料的合成。 熔鹽合成法是一種工藝簡(jiǎn)單的制備多元復(fù)合氧化物的方法,目前已經(jīng)應(yīng)用于個(gè)別電池材料的研究,但研究熔鹽種類有限,缺乏系統(tǒng)性。本論文選擇了層狀結(jié)構(gòu)材料Li(Ni0.5Mn0.5)O2、Li(Ni0.2Mn0.2Co0.6)O2和尖晶石結(jié)構(gòu)LiMn2O4作為研究對(duì)象,系統(tǒng)研究了熔鹽種類以及反應(yīng)條件在熔鹽法合成中對(duì)這些材料結(jié)構(gòu)、形貌和電化學(xué)性能的影響。探索了熔鹽法在合成層狀和尖晶石狀結(jié)構(gòu)材料時(shí),熔鹽的選擇規(guī)律。 在對(duì)Li(Ni0.5M0.5)O2材料的研究中,發(fā)現(xiàn)LiCl熔鹽易造成最終產(chǎn)物的缺鋰。LiNO3和Li2CO3作為熔鹽均能合成出Li(Ni0.5Mn0.5)O2層狀材料。LiNO3作為熔鹽制備的材料循環(huán)穩(wěn)定性好,其放電比容量大于Li2CO3熔鹽制備的材料,但Li2CO3熔鹽制備的材料放電比容量隨循環(huán)有增大的趨勢(shì)。將LiNO3和Li2CO3按不同比例組合所得熔鹽對(duì)制備的Li(Ni0.5Mn0.5)O2形貌影響很大。當(dāng)用0.9LiNO3-0.05Li2CO3作熔鹽時(shí),Li(Ni0.5Mn0.5)O2顆粒尺寸均勻,表面光滑,在恒流模式下充放電,放電比容量為150 mAh g-1,恒流恒壓模式下為200 mAh g-1。 0.9LiNO3-0.05Li2CO3和0.38LiOH-0.62LiNO3均能作為熔鹽制備Li(Ni0.2Mn0.2Co0.6)O2材料,但因?yàn)槿埯}熔點(diǎn)不同,材料顆粒形貌不同,且放電比容量均不高。高溫下的二次熱處理能有效提高材料的放電比容量,以0.38LiOH-0.62LiNO3為熔鹽,經(jīng)二次處理過的Li(Ni0.2Mn0.2Co0.6)O2材料放電比容量達(dá)150 mAh g-1此外,氯化物和硫酸鹽實(shí)驗(yàn)證明不適合制備層狀Li(Ni0.2Mn0.2Co0.6)O2材料。 氯化物在制備尖晶石結(jié)構(gòu)材料時(shí)優(yōu)勢(shì)明顯。0.5NaCl-0.5KCl和0.6LiCl-0.4KCl都能制備出LiMn2O4材料。以0.5NaCl-0.5KCl作為熔鹽制備的LiMn2O4材料具有一次納米顆粒團(tuán)聚成二次微米顆粒的形貌。具有該形貌的LiMn2O4,能達(dá)到124 mAh g-1的放電比容量,且循環(huán)性能優(yōu)異。 最后,在上述材料的研究基礎(chǔ)上,本論文總結(jié)了熔鹽法合成鋰離子電池正極材料的熔鹽選擇規(guī)律以及制備工藝影響。用熔鹽法制備的鋰離子電池材料均具有較好的循環(huán)性能。除氯化物和硫酸鹽外,其它含鋰單組分鹽或者復(fù)合熔鹽均能用于制備層狀結(jié)構(gòu)材料。熔鹽的熔點(diǎn)對(duì)合成材料的形貌影響很大,進(jìn)而影響材料的電化學(xué)性能。氯化物可優(yōu)先選為制備尖晶石結(jié)構(gòu)材料所用熔鹽。熔鹽法合成在高溫(800℃左右)加熱5-6小時(shí)就能制備出結(jié)構(gòu)、形貌和電化學(xué)性能良好的電池材料。
[Abstract]:Lithium-ion batteries have been widely used in portable mobile devices such as cameras, mobile phones, laptops and other portable devices as clean and efficient energy sources, and have gradually been used in electric vehicles. The key to reducing the cost of lithium-ion batteries lies in the research and development of low-cost new materials and the simple and easy low-cost preparation method. It often takes decades to get to the end of the application, The optimization of the preparation process can be used in the synthesis of many materials. The method of molten salt synthesis is a simple method for the preparation of multicomponent composite oxides, which has been applied to the study of individual battery materials, but the kinds of molten salts are limited. In this paper, the layered structure material Li Li Ni 0.5 mn 0. 2 O 2 Li Li Li Ni 0. 2 mn 0. 2 Co 0. 6 O 2 and spinel structure LiMn2O4 were selected as the research objects. The types of molten salts and reaction conditions were systematically studied in the synthesis of these materials by molten salt method. The influence of morphology and electrochemical properties on the selection of molten salts in the synthesis of layered and spinel structure materials by molten salt method was investigated. In the study of Li(Ni0.5M0.5)O2 materials, it was found that the lithium-deficient Li-LiNo3 and Li2CO3 as the molten salts, which were the final products of LiCl, could be used as molten salts to synthesize Li(Ni0.5Mn0.5)O2 layered materials, which had good cycling stability, and their specific discharge capacity was higher than that prepared by Li2CO3 molten salts. However, the specific discharge capacity of the materials prepared by Li2CO3 melts increases with the cycle. The morphology of Li(Ni0.5Mn0.5)O2 is greatly affected by the combination of LiNO3 and Li2CO3 in different proportions. When 0.9LiNO3-0.05Li2CO3 is used as the molten salt, the size of Li(Ni0.5Mn0.5)O2 particles is uniform and the surface is smooth. The specific discharge capacity is 150 mAh g -1 in constant current mode and 200 mAh g -1 in constant current and constant voltage mode. Both 0.9LiNO3-0.05Li2CO3 and 0.38LiOH-0.62LiNO3 can be used as molten salts to prepare Li(Ni0.2Mn0.2Co0.6)O2 materials. However, because of the different melting points, the morphology of the materials is different, and the discharge specific capacity is not high. The secondary heat treatment at high temperature can effectively improve the discharge specific capacity of the materials, with 0.38LiOH-0.62LiNO3 as the molten salt. The specific discharge capacity of the secondary treated Li(Ni0.2Mn0.2Co0.6)O2 material is 150 mAh g ~ (-1). Furthermore, the chloride and sulfate experiments show that it is not suitable for the preparation of layered Li(Ni0.2Mn0.2Co0.6)O2 material. The advantages of chlorides in the preparation of spinel structure materials are obvious. 0.5NaCl-0.5KCl and 0.6LiCl-0.4KCl can both produce LiMn2O4 materials. The LiMn2O4 materials prepared with 0.5NaCl-0.5KCl as molten salt have the morphology of first order agglomeration of nanocrystalline particles into secondary micron particles. Limn _ 2O _ 4 can reach the discharge specific capacity of 124 mAh g ~ (-1). And the cycle performance is excellent. Finally, based on the research of the above materials, In this paper, the selection rule of molten salt and the influence of preparation process on the cathode materials of lithium-ion batteries synthesized by molten salt method are summarized. All the materials prepared by molten salt method have good cycling performance, except for chlorides and sulphates. Other lithium-containing monocomponent salts or composite melts can be used to prepare layered structure materials. The melting point of the molten salt has a great influence on the morphology of the synthesized materials. Chloride can be selected as the preferred molten salt for the preparation of spinel structure materials. The structure, morphology and electrochemical properties of the battery materials can be prepared by molten salt synthesis at about 800 鈩，

本文編號(hào)：1687771