Carbon Coated Fe3O4 Nanoparticles As Solid Electrolyte Interface for Improving Graphite Anodes in Lithium Ion Battaries

Objective

Lithium ion batteries (LIBs) have attracted much attention over the past 15 years as the energy source of cell phones, laptops, power tools, medical equipment, and entertainment devices. Low self-discharge rate, high energy density, temperature tolerance, and long life-time are the advantages that LIBs offer over any other sort of batteries¹. In addition, a considerable market growth is predicted for LIBs in future as a part of automobile industry where they power Hybrid Electrical Vehicles (HEVs), and Electrical Vehicles (EVs). To achieve the practical values that make LIBs applicable for EVs and HEVs, a lot of developments with the purpose of increasing capacity, safety, and life-time of the batteries have been investigated. Synthesis of new materials for the negative electrode of LIBs is a major component of this development. New anode materials have been synthesized with improved capacity, charge/discharge rates, and safety. However, their volume expansion during lithium intercalation/deintercalation is the major problem of these electrodes, which prevents their commercialization.  

Till date, the commercial anode material for LIBs has been graphite. However, graphite, as anode material for high energy/power density LIBs, suffers from low theoretical capacity and multitude of aging mechanisms. One of the major aging mechanisms is growth of solid electrolyte interface (SEI) layer on graphite, which results in loss of recyclable lithium ions and electrode material. This phenomenon unfavorably affects the life-time of the battery and makes the graphite electrode very vulnerable^2,3. Moreover, capacity loss and degradation of graphite, in used LIBs, disqualifies graphite anodes for recycling as a high quality material during LIBs recycling processes.

The overall research objective of this research is improving graphite electrode’s mechanical and electrochemical properties for LIBs that can deliver higher capacities while decreasing graphite degradation and irreversible capacity. This goal will be accomplished by:

Graphite surface modification by placing a thin layer of carbon coated Fe₃O₄ nanoparticles (NPs) on graphite’s surface as an artificial solid electrolyte interface layer. This method is expected to improve LIBs applications in HEVs and EVs and provide potential graphite recycling opportunities.

Methodology

Fe₃O₄ NPs will be synthesized⁴ and assembled on graphite by a solution-phase self-assembly method⁵. This method involves mixing two immiscible solutions of Fe₃O₄ NPs and graphite under sonication. The graphite/Fe₃O₄ NPs is expected to deliver higher capacity, decrease irreversible capacity during formation stage, and reduce graphite degradation during operating cycles. The electrochemical properties of the proposed electrode will be tested in a coin cell.  These tests will employ cyclic voltammetry as well as constant current galvanic cycling.  This will allow the capacity of the electrode material to be found experimentally as a function of charge/discharge rate, as well as the capacity windows that the electrochemical reactions take place. In order to characterize the electrode material, X-Ray Diffraction (XRD), Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM), and Atomic Frequency Microscopy (AFM) will be utilized.

References

1. Yoshino, A., The Birth of Lithium-Ion Battery. Angewandte Chemie-international Edition, 2012, 51(24), 5798.
2. Agubra, V.; Fergus, J. Lithium Ion Battery Anode Aging Mechanisms. Materials, 2013, 6, 1310.
3. Wang, H. Y.; Wang, F. M. Electrochemical Investigation of an Artificial Solid Electrolyte Interface for Improving the cycl-ability of Lithium Ion Batteries Using an Atomic Layer Deposition. J. Power source, 2013, 233,1.
4. Sun, S.; Zeng, H.; Robinson, D. B. Robinson; Raoux, S.; Rice, P. M.; Wang, S. X., Li, G. Monodisperse Magnetic Nanoparticles for Theranostic Applications. J. Am. Chem. Soc. 2004, 126, 273.
5. Guo, S.; Sun, S. FePt Nanoparticles Assembled on Graphene as Enhanced Catalyst for Oxygen Reduction Reaction. J. Am. Chem. Soc. 2012, 134, 2492.