锂镍氧基化合物的合成与性能表征

论文题目: 锂镍氧基化合物的合成与性能表征

论文类型: 博士论文

论文专业: 材料物理与化学

作者: 钟耀东

导师: 赵新兵

关键词: 锂离子电池,正极材料,锂镍氧化物,热分析,电化学性能,精细分析,红外光谱分析

文献来源: 浙江大学

发表年度: 2005

论文摘要: 锂离子电池因其高能量密度、质轻、体积小可再充电使用达500个循环,在小电池中已逐渐取代传统铅酸电池与镍镉电池,居于市场领先地位。尤其它可做成几微米到大尺寸的电池以供应计算机芯片,通信器材,甚至电动车使用。理论容量高达274mAh/g的正极材料LiNiO2极受研究关注,Delmas等法国学者提出以镁掺杂锂镍氧化物,能有效提高充放电循环稳定性,并于Li+脱嵌时提供支柱作用（pillaring effect）,因之少量掺镁可有效改进LiNiO2之电化学性能。以XRD依据I003/I104峰比值、R-factor(I-（006）+I102)/I101峰比值、I108与I110的峰分裂,探讨在不同煅烧温度、煅烧时间、升温速率、试样压片的压强大小、气氛等变数条件所合成之锂镍镁氧化物LiNi0.95Mg0.05O2。发现以大于210MPa对试样压片,在氧气气氛下经2℃/min升温速率升温至600℃,预烧9～15小时后,再粉碎、压片以2～5℃/min升温至600℃之后以1℃/min升温至750℃恒温20小时,可得I003/I104峰比值1.03～1.09,R-factor(I006+I102)/I101峰比值0.68～0.94,并且有（108）与（110）的分裂峰,同时c/a比值4.915～4.926,属于及R（?）m空间群的锂镍镁氧化合物。以上合成的锂镍镁氧化物LiNi0.95Mg0.05O2容量极不理想,所以选择能提高锂镍氧化物有序度的钴单掺,并与氟或镁共掺(LiNi0.8Co0.2O2,LiNi0.8Co0.2O1.95F0.05,LiNi0.75Co0.2Mg0.05O2)以期改善容量,以固相法两次合成,600℃恒温10小时与750℃恒温15小时煅烧经压片过的试样,XRD显示三者结晶良好,共掺充放电循环性能略好于单掺,锂离子扩散系数不受单掺或共掺影响都约在10-11cm2/sec。比较充放电循环前后的电化学阻抗谱,显示三者在循环后的电荷转移电阻都增大,此为正极材料在充放电循环时,因晶格畸变,引起体积尺寸变化,甚至有材料内部微小裂缝发生,而增加其电荷转移电阻.至于SEI膜电阻的无规律任意变化,则认为是SEI膜本身周而复始的形成、破坏、再形成、再破坏所导致。经红外光谱分析得知,循环时正极材料与电解液作用生成C=O,CH2CH3,C-O,OCO2-等功能团在正极表面,且不因单掺、共掺而有所不同。虽然掺钴后已改善容量,但无论钴单掺,与镁或氟共掺的锂镍氧化物其容量都不高,首次放电不足90mAh/g,其原因可能是固相法两次煅烧,尚不能均匀混合材料组分。所以改采湿化学法的溶胶凝胶,以顺丁烯二酸为络和剂,乙醇或去离子水为溶剂溶解金属硝酸盐,经反应成溶胶凝胶后再煅烧成LiNi0.8Co0.2O2,并以红外光谱分析、扫描电镜、热分析、XRD宏观及精细分析、充放电循环测试。发现以去离子水为溶剂的材料,其形成活化能较低,循环性能较佳,XRD精细分析指出其镍离子占据锂离子位置较少。而以乙醇为溶剂,其形成活化能较高,则透过XRD宏观分析,了解凝胶形成时因金属硝酸盐中的硝酸根离子催化顺丁烯二酸,从而将硝酸镍及硝酸钴还原成金属镍、金属钴,

论文目录:

摘要

Abstract

Chap. 1 Introduction

1.1 Introduction

1.2 Specific energy and energy density

1.3 Working principle and features of lithium-ion battery

1.4 The requirements for designing lithium-ion batteries

1.5 Cathode materials

1.5.1 Introduction

1.5.2 Layered oxides

1.5.3 LiCoO_2

1.5.4 LiNiO_2

1.5.5 LiNi_(1-y)Co_yO_2

1.5.6 LiMn_2O_4

1.5.7 LiNi_(1-y-z)Co_yMn_zO_2

1.5.8 LiFePO_4

1.5.9 Requirements for cathode materials

1.6 Anode materials

1.7 Electrolyte materials

1.7.1 Organic electrolyte liquid

1.7.2 Polymer electrolyte

1.8 Research Approach

Chap. 2 Experimental

2.1 Chemical reagents

2.2 Instruments and characterization

2.2.1 X-ray diffractometer:

2.2.2 Scanning electron microscope (SEM)

2.2.3 Infrared spectrometer

2.2.4 Electrochemical impedance spectrometer

2.2.5 Gravimetric/differential thermal analysis (TG/DTA)

2.2.6 Multi-channel battery tester

2.2.7 Furnace

2.2.8 Glove box

2.2.9 Mold for pelletizing powder

2.2.10 Grinding tools

2.3 Synthesis and experimental procedure

Chap. 3 Solid State Synthesis and Investigation of Mg-doped Lithium Nickelate

3.1 Introduction

3.2 Synthesis

3.3 Results and Discussion

3.3.1 X-ray diffraction pattern of synthesized powder

3.3.2 Comparison of precalcining under oxygen flow to in air

3.3.3 The effect on length of calcine time

3.3.4 The effect of heating rate

3.3.5 Pelletizing pressure effect

3.3.6 Micrograph of scanning electron microscope (SEM)

3.3.7 Electrochemical discharge capacity

3.4 Summary

Chap. 4 Characterization of Solid-State Synthesized Pure and Doped Lithium Nickel cobalt oxides

4.1 Introduction

4.2 Experimental

4.3 Results and discussion

4.3.1 Phase analysis

4.3.2 Infrared Spectroscopy

4.3.3 Cycling-induced microstructural damage

4.3.4 Chemical diffusion coefficient of Li-ion

4.3.5 Electrochemical impedance spectroscopy

4.4 Conclusions

Chap. 5 Characterization of Particulate Sol-Gel Synthesis of Lini_(0.8)Co_(0.2)O_2 via Maleic Acid assistance with different solvents

5.1 Introduction

5.2 Experimental

5.3 Results and Discussion

5.3.1 X-ray diffraction patterns and morphology

5.3.2 Thermal studies

5.3.3 Activation energy of formation of Lini_(0.8)Co_(0.2)O_2 via the reaction of NiO, CoO and Li_2CO_3

5.3.4 Fourier transform infrared spectroscopy

5.3.5 Rietveld refinement

5.3.6 Chemical diffusion coefficients of Li~+ ion

5.3.7 Cyclability

5.4 Conclusions

Chap. 6 Study on the Properties of Lithium Nickel Cobalt Oxide Prepared by Citric Acid as the Chelating Agent

6.1 Introduction

6.2 Synthesis

6.3 Results and Discussion

6.3.1 Fourier transform infrared (FTIR) spectroscopy

6.3.2 X-ray diffraction patterns and morphology

6.3.3 Thermal analysis and activation energy of formation for Lini_(0.8)Co_(0.2)O_2

6.3.4 Rietveld refinement

6.3.5 Chemical diffusion coefficients of Li~+ ion

6.3.6 Cyclability

6.4 Conclusions

Chap. 7 Investigation on the Properties of Lithium Nickel Cobalt Oxide Prepared by Coprecipitation

7.1 Introduction

7.2 Synthesis

7.3 Results and Discussion

7.3.1 XRD and morphology

7.3.2 Fourier infrared spectroscopy (FTIR) of the as-prepared β-(Ni,Co)(OH)_2

7.3.3 Rietveld refinement

7.3.4 Chemical diffusion coefficients of Li~+ ion

7.3.5 Cyclability

7.4 Conclusions

Chap. 8 Miscellaneous

8.1 The correlation of structural parameters with cyclability

8.2 Hydrothermal synthesis

8.2.1 Introduction

8.2.2 Synthesis

8.2.3 Results and Discussion

8.3 Conclusions

Chap. 9 Conclusions

References

Appendix I. Publications

Appendix II. 个人简历

Appendix III. 致谢

发布时间: 2006-05-10

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锂镍氧基化合物的合成与性能表征

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