锂离子电池正极材料LiFePO4的表面碳包覆改性研究进展

Research Progress on the Surface Carbon Coating Modification of LiFePO4 Cathode Material for Lithium Ion Batteries

新能源材料对人类社会未来可持续发展至关重要,磷酸铁锂(LiFePO 4)作为一种锂离子电池正极材料,以污染性低、安全性高、成本低廉等诸多优点而著称,在一定的电流密度下它能够进行锂的可逆脱嵌,完成有序的充放电过程,是一种前景可观的电池正极材料,取得了非常引人瞩目的发展与进步。它的晶型结构属于橄榄石型,结构的体积变化很小,比较稳定,在充放电过程中不易坍塌与变形。然而,电子和离子电导率低是制约磷酸铁锂材料发展的两个致命缺点,低的电导率还会引起其倍率和循环性能的降低。针对这些问题,人们提出了许多改善方法,如掺杂其他元素到铁位和锂位、颗粒纳米化和表面包覆导电物质。而在LiFePO 4正极材料表面进行包覆改性处理以改善其倍率性能和循环寿命是目前应用最广泛且经济可行的方法。碳材料由于具有成本低廉、无毒、无污染、原料丰富和导电性高等特点,被研究者们广泛地用于磷酸铁锂正极材料的包覆。本文主要介绍了LiFePO 4正极材料表面碳包覆修饰改性的研究进展,并对碳源种类的选择、碳化机理和表面化学反应等进行了总结。

New energy materials play an important role for the sustainable development of the human society.Ferrous lithium phosphate(LiFePO 4)as one of the cathode materials of lithium-ion battery,with low-pollution,high safety,low-cost and other some merits can conduct the lithium reversible intercalation and deintercalation and complete the charge and discharge orderly at certain current density,so,it is a promising battery cathode material and has made remarkable development and progress.Its crystal structure is olive type and the change of volume structure is a little and maintains relatively stable,all of which guarantee the collapse and deformation of the structure under the condition of charge and discharge.However,the two deadly drawbacks that hinder the development of LiFePO 4 material are the low electronic and ionic conductivity,which lead to the poor cycling and rate performance of LiFePO 4.Therefore,in response to those questions,many improving methods are given by people,such as dropping other elements on Li and Fe site,nanoparticles and surface coating of conductive materials.Yet,coating modification on the surface of LiFePO 4 cathode material to improve its rate performance and cycle life is the most widely used and economically feasible method.Carbon material is widely used in the coating of lithium iron phosphate because of its low-cost,non-toxic,environment-friendly,rich raw material and high conductivity.This paper mainly introduces the research progress of modified LiFePO 4 cathode materials with surface carbon coating,and the selection of carbon sources,carbonization mechanism and surface chemical reaction are summarized.