Enhancing the Utilization Efficiency of Cathode Materials in the Li Ion Batteries
Funded by U.S. Department of Defense
Project Summary
This SBIR Phase I project was to develop and demonstrate a new class of nanoparticle-sized cathode composites based on nanostructured Lithium phosphate of LiMPO4 (M = Mn, Co) with a focus on the development of LiMnFePO4/C nanocomposite. This class of materials is expected to offer better performance over currently used cathode materials (e.g. LiFePO4 or LiCoO2), including higher voltages, larger capacities, better stability, and therefore is attractive for use in Li-ion cells for applications in both military systems (such as land vehicles, aircraft and other weapon platforms) and commercial systems (such as portable electronics and hybrid electric vehicles).
The research conducted in Phase I, which includes material design, synthesis, prototyping, and characterization, has well demonstrated the technical feasibility of the LiMnFePO4/C nanocomposite. This new cathode material utilizes the combinative effects of Fe doping, nano-particle and carbon coating. The key technical issues related to material processing for the production of LiMnFePO4/C nanocomposites were well addressed, and preliminary characterization in order to evaluate electrochemical performance has been conducted. The electrochemical results indicated that with this nanocomposite, a specific capacity similar with those reported in latest literature has been achieved, which is up to 167 mAh/g approaching the theoretical value of 171 mAh/g. The material synthesized also shows the excellent rate capability and cycling performance. In addition, the material can be produced through a cost-effective scalable process based on a modified solid state reaction process, while the investigation reported in literature that demonstrates good properties nearly all based on other complicated expensive processes.
Besides the investigation on LiMnFePO4/C, we also carried out the investigations of LiCoFePO4/C nanocomposite. In spite that we have successfully synthesize the materials with desirable microstructure, the capacity of LiCoFePO4/C, 110 mAh/g is still considerably lower than that expected, for instance, 140 mAh/g. In addition, in order to successfully use LiCoFePO4/C, we also need to develop new electrolyte or modify the conventionally used electrolyte. Therefore our focus is move toward the development of LiMnFePO4/C nanocomposite.
In the end of this Phase I project, our preliminary research has also pointed to a new material processing approach for the cost-effective production of LiMnFePO4/C nanocomposite. Consequently, the investigative study carried out in Phase I has established a solid technical basis for Phase II of the project, which will focus on process optimization, scaling up, and system demonstration. In addition, the Phase I research also gives the direction for future material optimization, for instance, to achieve better low temperature performance and high rate capability.