Li4Ti5O12负极材料表面包覆SrF2抑制其胀气的机理研究

The spinel Li4Ti5O12 has demonstrated the potential as a good candidate material for negative electrode used in long life lithium ion energy storage and power batteries for its safety and excellent Li-ion intercalation/deintercalation reversibility. However, it is found that the lithium ion batteries using Li4Ti5O12 as anode material are easily being inflated during charge/discharge, which becomes a main obstacle for the large scale application of Li4Ti5O12 by battery manufacturers. In this proposal, the SrF2 uniformly coated Li4Ti5O12 will be obtained via an in situ chemical reaction deposition route. Using the characteristics of SrF2 of hydrofluoric acid corrosion resistant, electrochemical inert and playing a similar role to SEI film growing on the surface of graphite anode material, this proposal will study the mechanism of SrF2-coated layer which covers the surface activity sites and supresses the gas generation of Li4Ti5O12 anode material. Furthermore, this proposal will analyse the relecance between the thickness, uniformity and quality of SrF2-coated layer with the effect for supressing the gas generation of Li4Ti5O12 anode material. It is expected to obtain the basic principle of using SrF2 coating layer to surpress the gas generation of the Li4Ti5O12 andoe material from the above research results, which could accumulate basic datas, provide theoretical guidances for solving the problem of generating gas of Li4Ti5O12 anode material via coating inorganic compound and promoting the application of Li4Ti5O12 anode material.

尖晶石型钛酸锂因具有良好的安全性和循环稳定性，作为长寿命储能及动力锂离子电池负极材料具有潜在的应用前景，然而钛酸锂负极存在的胀气问题成为制约其产业化应用的主要瓶颈之一。本项目拟采用原位化学反应沉积的方法在钛酸锂表面均匀包覆SrF2，利用SrF2耐氢氟酸侵蚀、电化学惰性及可起类似碳负极表面SEI膜效应等特性，研究其屏蔽钛酸锂表面活性点、抑制胀气的机理，分析SrF2包覆层厚度、包覆层均匀性及包覆量等与抑制钛酸锂胀气效果之间的关联。综上研究结果，阐明包覆SrF2抑制钛酸锂负极材料胀气的基本原理，为包覆无机化合物解决钛酸锂胀气、促进钛酸锂推广应用积累基础数据和提供理论指导。

尖晶石型钛酸锂（Li4Ti5O12，LTO）因具有良好的安全性和循环稳定性，作为长寿命储能及动力锂离子电池负极材料应用前景广阔。然而LTO负极材料在实际应用中存在胀气问题，严重影响了LTO电池的电化学性能及使用安全性。本项目采用原位化学共沉淀法成功在LTO微粒表面包覆一层纳米尺寸的SrF2，利用SrF2耐氢氟酸侵蚀、电化学惰性及可起类似碳负极表面SEI膜效应等特性，屏蔽了LTO微粒表面（111）晶面Ti3+/4+催化活性点，阻隔了其与电解液的接触，较好抑制了其作为负极材料使用时的产气行为。此外，研究还表明，SrF2包覆层越均匀越有利于抑制LTO的产气行为，主要因为均匀的SrF2包覆层能够更高效的覆盖LTO微粒表面的催化活性点。但是，研究表明，SrF2包覆层不能太厚，太厚的包覆层会导致LTO比容量下降，倍率性能变差，主要因为SrF2包覆层属于电化学惰性及电绝缘物质，当其太厚时，不仅会挤占电极中LTO活性物质的质量削弱比容量发挥，还会导致LTO电极极化加剧损害其倍率性能。当SrF2包覆层的厚度为10纳米左右、质量在SrF2/LTO复合材料中所占的比例为2%时， SrF2包覆层不但能够较好的屏蔽LTO表面的催化活性点，而且其导致的电极极化不大，此时，LTO的胀气行为被抑制同时还展现出优异的倍率性能。本项目探索出了一条有效解决LTO在实际应用中产气行为的途径，同时总结出了该方法解决LTO产气行为的机理，对于研究LTO负极材料产气行为具有重要的理论意义，同时亦对LTO负极材料的实际应用具有重要的指导意义。含适量SrF2包覆层的SrF2/LTO复合材料作为储能及动力锂离子电池负极材料具有较高的实用价值。