| 氧化体系对LiFePO4化学脱锂的影响 |
| Influence of Oxidation System on Chemical Delithiation of LiFePO4 |
| 作者 | 单位 | E-mail | | 孙孝飞 | 西安交通大学电子陶瓷与器件教育部重点实验室, 国际电介质研究中心, 西安 710049 | | | 徐友龙 | 西安交通大学电子陶瓷与器件教育部重点实验室, 国际电介质研究中心, 西安 710049 | ylxu@mail.xjtu.edu.cn | | 陈国岗 | 西安交通大学电子陶瓷与器件教育部重点实验室, 国际电介质研究中心, 西安 710049 | | | 李彤 | 西安交通大学电子陶瓷与器件教育部重点实验室, 国际电介质研究中心, 西安 710049 | | | 贾蓂瑞 | 西安交通大学电子陶瓷与器件教育部重点实验室, 国际电介质研究中心, 西安 710049 | | | 李璐 | 西安交通大学电子陶瓷与器件教育部重点实验室, 国际电介质研究中心, 西安 710049 | |
|
| 摘要: 化学脱锂被广泛用于研究锂离子电池活性材料脱锂前后结构与性能的相互关系。本文通过改进的固相烧结法制备了粒径约12.61μm的超大颗粒LiFePO4粉末，分别在乙腈和水溶液体系中采用NO2BF4和K2S2O8作为氧化剂对其进行化学脱锂，探讨了两种氧化体系所得到的FePO4在晶体结构、颗粒形貌和电化学性能等方面的差异。实验结果表明，溶剂亦高度参与了脱锂反应，特别是K2S2O8氧化得到的FePO4中存在大量O-H基团，除未被烘干的H2O外，说明LixFePO4(0≤x≤1)在强氧化性水溶液中可能存在质子嵌入。伴随反应过程中搅拌分散、物质溶解、化学脱锂和质子嵌入等协同作用，使所得FePO4的晶胞体积和颗粒尺寸明显减小，最终导致充放电曲线畸变、阻抗增大和容量降低。虽然低温退火可去除大部分O-H，但是不可逆的结构和形貌改变导致电池性能依然无法与初始LiFePO4相比。与此相反，采用NO2BF4有机溶液体系脱锂得到的FePO4没有发生明显的结构、形貌和性能变化，因而是一种更加可靠的LiFePO4化学脱锂体系。 |
| 关键词: 磷酸铁锂 化学脱锂 质子嵌入 正极材料 锂离子电池 能量存储 |
| 基金项目: 国家自然科学基金(20804030、50902109)、高等学校博士点专项科研基金(20110201130005)资助项目。 |
| Abstract: Chemical delithiation is widely used in literature to study the structure-property-performance relationship of olivine LiFePO4 before/after lithium extraction, but the influence of oxidation system on the structure, morphology and electrochemical performance of the resulted LixFePO4(0≤x<1) is seldom noticed. In this paper, large particle LiFePO4 is synthesized via a modified solid-state reaction method and is chemically delithiated by NO2BF4 in acetonitrile or by K2S2O8 in an aqueous solution. Solvents are found highly involved in chemical delithiation of LiFePO4, and significant O-Hgroups are identified in FePO4 derived by K2S2O8 Moreover, proton insertion into the crystal lattice of LixFePO4 (0≤x≤1) is demonstrated possible in such highly oxidative aqueous solutions. The synergism of dispersion, dissolution, delithiation, and more importantly protonation induces serious structure and morphology change to so-obtained FePO4 and makes the particle size much smaller. Consequently, the specific discharge capacity is dramatically decreased with increased charge transfer impedance, and the charge/discharge curves are transformed to slope-like profiles. Although these protons (including residual water and hydroxyls) could be removed by low temperature annealing, the battery performance can't be fully recovered due to the irreversible structure and morphology change. On the contrary, there is no obvious proton incorporation during chemical delithiation of LiFePO4 by NO2BF4 in organic solutions, which leads to FePO4 with almost invariant structure, morphology and performance comparing to pristine LiFePO4. |
| Keywords: lithium iron phosphate chemical delithiation proton insertion cathode material lithium ion battery energy storage |
| 投稿时间：2013-09-17 修订日期：2013-12-19 |
| 摘要点击次数: 1344 |
| 全文下载次数: 1603 |
| 孙孝飞,徐友龙,陈国岗,李彤,贾蓂瑞,李璐.氧化体系对LiFePO4化学脱锂的影响[J].无机化学学报,2014,30(6):1403-1412. |
| 查看全文 查看/发表评论 下载PDF阅读器 |
| Support information: |
|
|
|
|
|
|
