Colloquium: Iron-Based Compounds as Cathode Materials for Li-Ion Batteries

ABSTRACT

Developing multi-valence transition metal compounds is one path toward high specific capacity/energy cathodes due to the corresponding multiple Li+ ion storage capacities. Iron oxyfluoride (FeOF) is a promising material with high theoretical specific capacity (590 and 885 mAh/g corresponding to 2 and 3 e- process), good safety, low environmental impact, and low cost. However, low electric conductivity and poor reversibility of the (de)lithiation process make FeOF difficult to use as a cathode material. To address these challenges, an approach of incorporating graphene sheets into the nanostructure of FeOF was taken. Comprehensive and systematic studies reveal that the new FeOF/Graphene composite has delivered excellent electrochemical performance: near theoretical specific capacity (590 mAh/g), excellent rate capability, and greatly extended capacity retention (more than 100 cycles with 80% initial capacity at 0.1 C). Furthermore, we conducted in-operando synchrotron XAS and high energy XRD studies that suggest a reversible structure change during cycling. Most interestingly, we observed an astonishing superfast charging phenomenon in this FeOF/Graphene composite, which can deliver 342 mAh/g and 581 Wh/kg with a 100 C (36s) charging rate. Finally, we have applied a similar approach to incorporate graphene sheets into the nanostructure of metal compounds, which has been demonstrated to be effective for addressing the fundamental issues of battery materials and opens a new avenue for developing high-performance battery materials.

BIOGRAPHY

Prof. Xie is a professor at the School of Mechanical Engineering, School of Materials Engineering, Purdue University, and Department of Mechanical and Energy Engineering at the Purdue School of Engineering and Technology, IUPUI. He has published more than 80 journal papers including Nature Energy, Nature Catalysis, Nature Communications, and 2 book chapters, 21 patents (10 issued). His research focuses on nanomaterials, energy storage, catalysis/electrocatalysis, energy conversion, clear energy. He serves as a panelist for ARPAE, Fuel Cell Technology Office, US Department of Energy Office of Technology Transfer, and the Canadian National Science Foundation. He developed electric propulsion systems for Electric Vehicles (EVs) and Hybrid EVs at General Motors Advanced Technology Vehicle Center. Prof. Xie received his PhD in chemistry from Miami University in 1999 and a BS in chemical engineering (emphasis on electrochemical engineering) from Tianjin University, China in 1982.