【摘要】：尖晶石型LiMn2O4正極材料由于其環(huán)保程度、成本、原料來(lái)源、性能等多方面都具有一定優(yōu)勢(shì)而受到了科研工作者的廣泛關(guān)注。然而,LiMn2O4材料本身存在Li+擴(kuò)散速率小、電子電導(dǎo)率低與循環(huán)性能差等缺陷,其中循環(huán)性能差是限制其應(yīng)用領(lǐng)域和范圍的主要原因。為了進(jìn)一步改善LiMn2O4正極材料的性能,本文在水熱法結(jié)合高溫固相法的基礎(chǔ)上,采用陰陽(yáng)離子協(xié)同摻雜的方法,制備出高性能材料,為促進(jìn)LiMn2O4正極材料在工業(yè)化生產(chǎn)提供一些技術(shù)支持。1.采用水熱法合成由細(xì)長(zhǎng)棒狀結(jié)構(gòu)組成的球形MnO2。然后以MnO2作為前驅(qū)體,采用兩步燒結(jié)方式合成球形形貌的LiMn2O4,研究溫度和Li/Mn對(duì)材料微觀形貌,晶體結(jié)構(gòu)以及電化學(xué)性能的影響,確定最佳煅燒溫度為500℃下煅燒6h,然后在750℃下煅燒18 h。2.通過(guò)掃描電鏡(SEM)對(duì)MnO2進(jìn)行了形貌分析,通過(guò)SEM、X射線衍射分析(XRD)、循環(huán)伏安測(cè)試(CV)和充放電測(cè)試對(duì)LiMn2O4和LiFe0.08Mn1.92O3.9F0.1進(jìn)行了表征。結(jié)果表明Fe、F復(fù)合摻雜的Li Fe0.06Mn1.94O3.88F0.12材料具備規(guī)整的形貌、更穩(wěn)定的晶體結(jié)構(gòu)、良好的循環(huán)性能和倍率性能。0.2 C時(shí)LiFe0.06Mn1.94O3.88F0.12材料的首次放電比容量為133.6 mAh/g,電化學(xué)性能較好,而LiMn2O4僅為128.8 mAh/g。在0.5 C倍率下,LiFe0.06Mn1.94O3.88F0.12材料的首次放電比容量為121.6 mAh/g,而Li Mn2O4僅為117.7mAh/g,循環(huán)80次后,容量保持率分別為83.06%和77.57%。3.以水熱合成的納米球形MnO2作為模板,采用高溫固相法合成球形形貌的LiMn2O4,LiMn1.94Fe0.06O4和LiNa0.06Mn1.94Fe0.06O4,通過(guò)X射線衍射分析(XRD)、SEM、EDS對(duì)三種材料進(jìn)行物理表征。結(jié)果表明Na、Fe復(fù)合摻雜的LiNa0.06Mn1.94Fe0.06O4材料較穩(wěn)定的晶體結(jié)構(gòu)、顆粒尺寸較小(約160nm),摻雜的離子成功進(jìn)入到晶格內(nèi)。在0.5 C倍率下循環(huán)100次后,LiNa0.06Mn1.94Fe0.06O4放電比容量為108.0 mAh/g,而LiMn2O4僅為92.2 m Ah/g,容量保持率分別為74.12%和90.91%,在10 C時(shí),LiNa0.06Mn1.94Fe0.06O4放電比容量比LiMn2O4高34.3mAh/g。進(jìn)一步研究表明,Na、Fe復(fù)合摻雜對(duì)材料的鋰離子擴(kuò)散系數(shù)和電荷轉(zhuǎn)移阻抗有著積極的影響。4.采取Zn單獨(dú)摻雜和Zn、F雙元素復(fù)合摻雜的方式,通過(guò)不同摻雜量的優(yōu)化,得出最佳單一摻雜材料為L(zhǎng)iMn1.97Zn0.03O4,其電化學(xué)性能與之前LiMn2O4材料相比有較明顯的提高,具有更好的電化學(xué)可逆性與結(jié)構(gòu)穩(wěn)定性。LiMn1.97Zn0.03O3.92F0.08具有最佳的循環(huán)穩(wěn)定性和倍率性能,其鋰離子擴(kuò)散系數(shù)高于純LiMn2O4樣品電極以及LiMn1.97Zn0.03O4材料。
[Abstract]:Spinel LiMn2O4 cathode materials have been widely concerned by researchers because of their advantages in environmental protection, cost, source of raw materials and properties. However, LiMn2O4 material has some defects such as low Li diffusion rate, low electronic conductivity and poor cycling performance, among which poor cycling performance is the main reason for limiting its application field and scope. In order to further improve the properties of LiMn2O4 cathode materials, based on hydrothermal method and high temperature solid state method, high performance materials were prepared by co-doping of anions and anions. In order to promote the LiMn2O4 cathode materials in industrial production to provide some technical support. 1. Spherical MNO _ 2 with slender rod structure was synthesized by hydrothermal method. Using MnO2 as precursor, limn _ 2O _ 4 with spherical morphology was synthesized by two-step sintering. The effects of temperature and Li/Mn on the microstructure, crystal structure and electrochemical properties of the material were investigated. The optimum calcination temperature is 500 鈩，

本文編號(hào)：2193024