论文总字数：19597字

摘 要

橄榄石型磷酸盐LiMPO₄ 正极材料(M=Mn, Fe, Co和Ni)具有良好的热稳定性、成本较低、对环境友好以及高能量密度等优势。但是由于LiMnPO₄本征的电子电导率和离子电导率均较低，导致其电化学活性很低，限制了LiMnPO₄的商业化应用。本文利用微通道反应器合成出纳米前驱体颗粒，再与碳源或者锂源、碳源共同球磨混合，经高温煅烧得到了具备高电化学活性的纳米LiMnPO₄/C正极材料。本文共沉淀法不同的实验室条件进行对比，对前驱体及LiMnPO₄的微观结构、成分、形貌、物相及电化学性能进行分析。探究了LiMnPO₄/C正极材料的微观结构与其电化学性能之间的内在联系。

本文利用微反应器共沉淀制备出纳米前驱体颗粒Mn₃(PO₄)₂。研究发现，碳源、微反应器中反应物流速、固相烧结温度、不同的原料配比都会对制备的正极材料性能产生影响。碳源能够在一定程度上抑制晶粒生长，然而过量的碳会造成锂离子脱嵌困难。当碳源加入量为20 wt%，材料的电化学活性最高。150 ml/min流速制备出LiMnPO₄/C复合材料的电化学性能最优异。研究表明当煅烧温度为650 ℃时，制备出来LiMnPO₄/C正极材料电化学性能良好。而LiMnPO₄/C粒子尺寸对自身的电化学性能也有很大的影响，颗粒尺寸越小，其电化学活性越高。

关键词：锂离子电池 磷酸锰锂 微反应器 电化学性能

Preparation of nano LiMnPO₄/C cathode materials by micro reactor co precipitation method

ABSTRACT

Olivine type phosphate LiMPO₄ cathode materials (M=Mn, Fe, Co and Ni) have good thermal stability, low cost, environmental friendly and high energy density and other advantages. However, due to the low electronic conductivity and ionic conductivity of LiMnPO₄, its electrochemical activity is very low, which limits the commercial application of LiMnPO₄. In this paper, the nano precursor particles were synthesized by micro channel reactor, and then mixed with carbon source or lithium source and carbon source, the LiMnPO₄/C cathode material with high electrochemical activity was obtained by high temperature calcination. In this paper, the microstructure, composition, morphology, phase and electrochemical properties of the precursor and LiMnPO₄ were analyzed by the method of coprecipitation in different laboratory conditions. The intrinsic relationship between the microstructure and electrochemical properties of LiMnPO₄/C cathode materials was explored.

In this paper, the Mn₃ (PO₄) ₂ nanoparticles were prepared by co precipitation of micro reactor. The study found that the carbon source, the reaction speed of the reaction in the micro reactor, the solid phase sintering temperature, the different raw materials ratio will have an impact on the performance of the cathode materials. Carbon source can inhibit grain growth to some extent, however, the excess carbon can cause the difficulty of lithium ion removal. When the carbon source was 20 wt%, the electrochemical activity of the material was the highest. The electrochemical properties of LiMnPO₄/C composites prepared by 150 ml/min flow rate were the best. The research shows that the electrochemical performance of LiMnPO₄/C cathode material is good when the calcination temperature is 650 centigrade. The LiMnPO₄/C particle size has a great influence on its electrochemical properties, the smaller the particle size, the higher its electrochemical activity.

KEYWORD: Li-ion battery；Lithium manganese phosphate；Microreactor；Electrochemical performance

目 录

摘要·······························································I

ABSTRACT···············································II

第一章 文献综述···········································1

1.1 引言·························································1

1.2 LiMnPO₄ 的结构性质··········································1

1.3 LiMnPO₄的制备方法···········································2

1.4 LiMnPO₄电化学性能研究及其改性·······························4

1.5本文所选课题的必要性与主要工作·······························4第二章 试验方法及制备条件·······································5

2.1制备方法·····················································5

2.2 实验变量····················································5

第三章 实验数据分析··············································6

3.1 锂盐浓度····················································6

3.1.1 不同锂盐浓度对前驱体和LiMnPO₄的影响················6

3.2 水浴温度····················································7

3.2.1 不同水浴温度对前驱体和LiMnPO₄的影响················8

3.2.2 电化学性能分析······································10

3.3 表面碳包覆改性研究········································11

3.3.1 物相分析及TEM微观结构分析·························12

3.3.2 电化学性能分析·····································13

3.4 微反应器流速对LiMnPO₄/C的影响····························14

3.4.1 前驱体形貌分析·····································14

3.4.2 物相分析与电化学性能分析···························15

第四章 结论与展望···············································17

参考文献·························································19

致谢······························································22

1. 文献综述
2. 1引言

由于不断增长的市场，便携式电子设备、电动汽车的需求，锂离子电池作为储能系统的先驱已经引起了越来越多的关注。而橄榄石型磷酸盐系正极材料LiMPO₄作为其中的佼佼者，人们认为其为最具开发潜力的锂离子电池正极材料，目前成为了国内外的研究热点^[1-3]。其中，LiFePO₄已被广泛的研究和成功的商业化^[4-7]，相比于已经成功商业化的LiFePO₄，LiMnPO₄有着比LiFePO₄更高的氧化还原电位(4.1 V vs. Li /Li)，这意味着LiMnPO₄有着比LiFePO₄更高的能量密度，存在着巨大的应用前景。然而，受锂脱嵌动力学的影响，LiMnPO₄的电子电导率和离子扩散速率较低，导致其电化学活性很低，再加上充放电过程中较大的体积变化引起的结构不稳定，限制了它的大规模应用^[8-10]。

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