尖晶石錳酸鋰及其化合物的表面修飾
發(fā)布時(shí)間：2019-02-25 07:41
【摘要】：隨著資源和環(huán)境危機(jī)的加劇，鋰離子電池正極材料受到了更廣泛的關(guān)注，越來越多的研究人員也致力于正極材料的合成和改進(jìn)�？偟膩碚f，正極材料的改進(jìn)主要從兩個(gè)方面著手：一是化學(xué)方法，通過摻雜或表面包覆等手段減小材料和電解液的直接接觸面積，，從而改善電極的放電比容量、倍率性能和循環(huán)性能，尤其是高溫循環(huán)性能；二是物理方法制備混合電極，利用不同種類正極材料的協(xié)同作用穩(wěn)定晶體結(jié)構(gòu)，從而達(dá)到改善電極電化學(xué)性能、結(jié)構(gòu)和熱穩(wěn)定性的目的。本文主要圍繞尖晶石LiNi0.5Mn1.5O4和LiMn2O4兩種材料進(jìn)行改性，主要內(nèi)容包括以下幾個(gè)方面： 第一章：根據(jù)材料中金屬種類的不同對(duì)電池正極材料進(jìn)行了分類，重點(diǎn)介紹了文章中主要涉及到的三種材料（LiNi0.5Mn1.5O4、LiMn2O4和LiNiO2）的合成方法、結(jié)構(gòu)特征、容量衰減因素和存在的問題，并對(duì)三種材料的包覆、摻雜和物理混合等改性研究進(jìn)行了歸納總結(jié)。 第二章：采用二次干燥共沉淀法合成尖晶石LiNi0.5Mn1.5O4，并通過溶膠-凝膠法對(duì)其進(jìn)行表面包覆改性，制備出LiNi0.5Mn1.5O4表面存在均勻LiCoPO4包覆層的正極材料。提出了采用工作電壓與本體材料接近的活性電池材料作為包覆物質(zhì)的概念，通過XRD、SEM、TEM、交流阻抗測(cè)試等手段對(duì)材料進(jìn)行了表征，實(shí)驗(yàn)結(jié)果研究表明，2wt%LiCoPO4包覆層的存在，明顯地改善了電池材料的電化學(xué)性能和熱穩(wěn)定性。 第三章：在前一章實(shí)驗(yàn)內(nèi)容的基礎(chǔ)上改變包覆方法，在前驅(qū)體表面包覆Co3(PO4)2，然后與LiOH H2O混合，經(jīng)過一步燒結(jié)制備出LiCoPO4包覆的LiNi0.5Mn1.5O4，透射電鏡結(jié)果證明了包覆層的存在，而藍(lán)電測(cè)試結(jié)果表明材料經(jīng)包覆改性后性能得到了提高。 第四章：采用溶膠-凝膠法分別制備了層狀結(jié)構(gòu)的LiNiO2和尖晶石結(jié)構(gòu)的LiMn2O4，按照質(zhì)量比為1:9的比例混合制備混合電極。利用XRD等手段證明了電池材料的成功制備，并對(duì)混合、單一電極分別進(jìn)行了電化學(xué)性能測(cè)試。結(jié)果表明，與單一LiMn2O4電極相比，混合電極表現(xiàn)出更高的放電容量，更優(yōu)異的倍率性能和循環(huán)穩(wěn)定性。
[Abstract]:With the aggravation of resource and environment crisis, more and more researchers focus on the synthesis and improvement of cathode materials for lithium-ion batteries. In general, the improvement of cathode materials mainly starts from two aspects: one is chemical method, which reduces the direct contact area between material and electrolyte by doping or surface coating, thereby improving the specific discharge capacity of the electrode. Double rate performance and cycle performance, especially high temperature cycle performance; Secondly, the mixed electrode was prepared by physical method, and the crystal structure was stabilized by the synergistic action of different kinds of cathode materials, so as to improve the electrochemical performance, structure and thermal stability of the electrode. In this paper, two kinds of spinel LiNi0.5Mn1.5O4 and LiMn2O4 were modified. The main contents include the following aspects: chapter 1: the battery cathode materials are classified according to the different kinds of metals in the materials. The synthesis methods, structural characteristics, capacity attenuation factors and existing problems of three kinds of materials (LiNi0.5Mn1.5O4,LiMn2O4 and LiNiO2) are mainly introduced in this paper. The modification studies of doping and physical mixing were summarized. Chapter 2: spinel LiNi0.5Mn1.5O4, was synthesized by secondary drying coprecipitation method and modified by sol-gel method. The cathode material with uniform LiCoPO4 coating on LiNi0.5Mn1.5O4 surface was prepared. The concept of the active battery material which is close to the bulk material is proposed. The material is characterized by means of XRD,SEM,TEM, AC impedance measurement. The experimental results show that the material can be used as the coating material. The existence of 2wt%LiCoPO4 coating obviously improves the electrochemical performance and thermal stability of the battery materials. Chapter 3: on the basis of the experimental contents in the previous chapter, we change the coating method, coating Co3 (PO4) 2 on the surface of the precursor, then mix it with LiOH H2O, and then prepare the LiNi0.5Mn1.5O4, coated with LiCoPO4 by one step sintering. The results of transmission electron microscope (TEM) showed the existence of the coating layer, while the blue electric test showed that the properties of the coating were improved after the coating modification. In chapter 4, the mixed electrode was prepared by sol-gel method with layered LiNiO2 and spinel LiMn2O4, at 1:9 mass ratio. The successful preparation of the battery material was proved by means of XRD, and the electrochemical properties of the mixed electrode and single electrode were tested respectively. The results show that the mixed electrode has higher discharge capacity, better rate performance and better cycle stability than the single LiMn2O4 electrode.
【學(xué)位授予單位】：河南師范大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2014
【分類號(hào)】：TM912;TQ131.11
本文編號(hào)：2429944
[Abstract]:With the aggravation of resource and environment crisis, more and more researchers focus on the synthesis and improvement of cathode materials for lithium-ion batteries. In general, the improvement of cathode materials mainly starts from two aspects: one is chemical method, which reduces the direct contact area between material and electrolyte by doping or surface coating, thereby improving the specific discharge capacity of the electrode. Double rate performance and cycle performance, especially high temperature cycle performance; Secondly, the mixed electrode was prepared by physical method, and the crystal structure was stabilized by the synergistic action of different kinds of cathode materials, so as to improve the electrochemical performance, structure and thermal stability of the electrode. In this paper, two kinds of spinel LiNi0.5Mn1.5O4 and LiMn2O4 were modified. The main contents include the following aspects: chapter 1: the battery cathode materials are classified according to the different kinds of metals in the materials. The synthesis methods, structural characteristics, capacity attenuation factors and existing problems of three kinds of materials (LiNi0.5Mn1.5O4,LiMn2O4 and LiNiO2) are mainly introduced in this paper. The modification studies of doping and physical mixing were summarized. Chapter 2: spinel LiNi0.5Mn1.5O4, was synthesized by secondary drying coprecipitation method and modified by sol-gel method. The cathode material with uniform LiCoPO4 coating on LiNi0.5Mn1.5O4 surface was prepared. The concept of the active battery material which is close to the bulk material is proposed. The material is characterized by means of XRD,SEM,TEM, AC impedance measurement. The experimental results show that the material can be used as the coating material. The existence of 2wt%LiCoPO4 coating obviously improves the electrochemical performance and thermal stability of the battery materials. Chapter 3: on the basis of the experimental contents in the previous chapter, we change the coating method, coating Co3 (PO4) 2 on the surface of the precursor, then mix it with LiOH H2O, and then prepare the LiNi0.5Mn1.5O4, coated with LiCoPO4 by one step sintering. The results of transmission electron microscope (TEM) showed the existence of the coating layer, while the blue electric test showed that the properties of the coating were improved after the coating modification. In chapter 4, the mixed electrode was prepared by sol-gel method with layered LiNiO2 and spinel LiMn2O4, at 1:9 mass ratio. The successful preparation of the battery material was proved by means of XRD, and the electrochemical properties of the mixed electrode and single electrode were tested respectively. The results show that the mixed electrode has higher discharge capacity, better rate performance and better cycle stability than the single LiMn2O4 electrode.
【學(xué)位授予單位】：河南師范大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2014
【分類號(hào)】：TM912;TQ131.11
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