双活性P-Ge化合物作为锂离子电池新型负极材料的基础研究

We for the first time propose to develop a new type anode material which combines two lithium-active components of Ge and P into one compound for lithium ion batteries. Our primary study has shown that such a Ge-P based compound (GeP5) can exhibit a large reversible specific capacity of 2200 mAh/g，which is two times higher than those of other metal phosphides; and at the same time, its initial coulombic efficiency achieves 94%, much higher than the reported values for current high-capacity anode materials and comparable to the level of commercial graphite anode. Besides, it is found systematically investigation on the structural characteristics and physical chemical features of germanium phosphides has not been done yet. In this proposal, we will in-depth investigate this type of double active P-Ge based compounds on their synthesis，structural features，physical chemical properties, and electrochemical performances. In detail，we will synthesize GeP, GeP2, GeP3 and GeP5 by a high energy ball milling method and study their thermo and chemical stability; explore the effect of different P/Ge ratios on the crystallography structure and electronic conductivity through structure simulation and first principal calculation; identify their reaction mechanism during lithium storage by combining electrochemical techniques and multiple physical chemical measurements; promote their electrochemical performances according to their structural and behavior features; and assess their application in a full battery system. The implementation of this project can provide in-depth knowledge support and practical guidance for the development of this new type P-Ge double active material, understanding of their physical and chemical properties, and application of them as anodes in lithium ion batteries.

本项目首次提出将具有储锂活性的Ge和P同时引入到一个化合物中作为锂离子电池的负极材料，前期研究表明磷锗化合物GeP5的可逆比容量达2200mAh/g, 是其它金属磷化物的2倍以上；同时其首次库仑效率达94%，远高于现有大容量负极材料的文献报道值, 达到了商业石墨负极的水平。此外，有关磷锗化合物自身结构及物理化学性质的系统研究目前也未见报道。在本项目中，我们将把这种新型P-Ge双活性材料从GeP5拓展到 GeP、GeP2和GeP3，深入研究不同P/Ge比化合物的合成条件、热稳定性和化学稳定性；通过结构精修和第一原理计算模拟P/Ge比的变化对晶体结构和导电性的影响；通过电化学测试技术结合多方位的表征手段研究其储锂的反应机理，并依据其结构特征及电化学行为特点进行性能优化，对其在全电池中的应用进行评价，为此类双活性材料的开发、物理化学特性的认识及其在锂离子电池中的应用提供理论指导和技术借鉴。

本项目将同时具有储锂活性的Ge和P元素组合到一个物质当中，利用简单的机械球磨法合成了一系列具有不同Ge/P比的层状二元锗磷化合物，完成了对其热稳定性、耐溶剂性、晶体结构、元素价态、导电性等物理化学性质的表征，发现了Ge-P之间可以形成一类宽范围的二元合金固溶体，明确了其保持层状结构的固溶范围和边界条件，通过电化学性能测试表明这一系列不同比例的锗磷合金均可表现出高的电化学活性和良好的充放电可逆性，利用第一原理计算结合同步辐射X射线吸收对其成键特点、价态组成、电化学表现进行了多层次的表征和分析，获得了材料优异电化学性能的作用机制和深层原因。通过粘结剂优化，提升了电极的粘接性和完整性，降低了GePx电极的制造成本和环境影响；通过将GePx与硬碳制成复合电极，降低了电极的整体膨胀率，得到了可以同时提升比容量和库伦效率的硬碳负极；通过静电纺丝将GePx活性颗粒包裹在碳纤维基质中，提升了GePx的热稳定性同时缓解了材料的体积膨胀，延长了电极的循环寿命。探索了GePx在钠离子电池以及全电池中的应用，发现其在钠离子电池中同样显示出超高的储钠活性和可逆性，是一类锂离子/钠离子电池性能双优的负极材料。. 项目的实施不仅开发了一类具有优异储锂、储钠活性的大容量、高可逆性新型GePx合金负极材料，而且获得了GePx二元合金材料电化学性能的规律性认识，提出了这类大容量高可逆合金负极的设计原则，并据此拓展开发了具有类似结构特点和成键性质的其它Ge基材料，如Ge-S，Ge-Se，Ge-Sb-Te等，验证了这种规律认识和设计原则的普适性，为后续发展新型合金负极材料及其组分选择和结构优化提供了理论依据和路线指导。相关工作已申请发明专利3项，在国际知名期刊上发表通讯作者SCI论文12篇，培养硕士和博士研究生多名。