Synthesis of LiFePO 4 Nanostructures for Lithium-Ion Batteries by Electrochemical Deposition

Transcription

1 Synthesis of LiFePO 4 Nanostructures for Lithium-Ion Batteries by Electrochemical Deposition Erika Aragon and Alfredo A. Martinez-Morales Southern California Research Initiative for Solar Energy College of Engineering Center for Environmental Research and Technology Department of Chemical and Environmental Engineering University of California, Riverside, 92521

2 Introduction Projected demand for future energy needs cannot be met with today s technology Requires more efficient energy grids Frequent real-time fluctuations; wasted energy Can cost tens of billions of dollars annually Requires utilization of renewable energies Solar Wind Intermittent in nature, require some form of energy storage Pursuit of the plug-in vehicle Can only last a distance of about fifty miles before recharge Be able to reduce carbon footprint, vehicle emissions, improve air quality, and reduce dependence on foreign oil

3 How a Battery Works Main components: Cathode Anode Electrolyte Chemical energy storage Energy depends on strength of chemical reactions Production of metal ions Ion flow through electrolyte Electron flow through external circuit (energy) Figure 1. Schematic of typical lithium-ion battery. Source: DOE Basic Energy Sciences Workshop, 2007.

4 Nanostructures Advantages: Higher charge and discharge rates More thermodynamic stability during charge and discharge cycles Higher energy density/capacity Higher reactivity (more power) Higher material conductivity Current progress: Synthesized nanowires for multiple materials (carbon, copper, etc.) LiFePO 4 thin films 500nm nanoparticles Goal: LiFePO 4 nanowires for batteries Figure 2. Schematic of bulk material, illustrating the heterogeneity of particle size, pore size, and pore structure. Source: DOE Basic Energy Sciences Workshop, Figure 3. Comparison of bulk, thin film, and nanowire structures after cycling. Source: Liu, J. et. al, ChemSusChem 2008.

5 Nanostructures Figure 4. Schematic of proposed lithium-ion battery utilizing synthesized LiFePO 4 nanowires as the cathode electrode. Source: Martinez-Morales, A. A., Battery & Energy Projects, 2011.

6 Electrochemical Deposition Relatively inexpensive, easy to manipulate setup Density Length Radius Experimental parameters: Membrane pore size Temperature Molar ration of precursors ph of electrolyte Reaction time Figure 5. Schematic of typical electrochemical deposition setup. Source: Martinez-Morales, A. A., Battery & Energy Projects, 2011.

7 Electrochemical Deposition Figure 6. Step process of the electrochemical synthesis of carbon coated LiFePO 4 nanowires. Source: Martinez-Morales, A. A., Battery & Energy Projects, 2011.

8 Synthesis with Sonication Produces consistent, higher quality nanowires Advantages of sonication: Creates pores for structure Localized higher temperatures resulting in faster growth Lowers electrical resistance and increases conductivity Results in longer length nanowires [7] [8] [9] [10] Figures 7, 8, 9, and 10. TEM micrographs (7) showing a typical nanorod produced by regular electrochemical deposition. (8) Representing a typical uniform nanorod produced sonoelectrochemically. TEM micrographs of nanorods after 15 min of (9) regular and (10) sonoelectrochemical deposition. Source: Singh, K. V., et. al, Chem. Mater., 2007.

9 Synthesis with Sonication [11] [12] [13] Figures 11, 12, and 13. Effect of ultrasonication on electrodeposition. (11) Growth rate of nanorods for ultrasonication, stirring, and regular processes. (12) Temperature rate of bulk electrolyte for same three processes. (13) Effect on resistance provided to electrodeposition by ultrasonication. Source: Singh, K. V., et. al, Chem. Mater., 2007.

10 Timeline & Future Work Figure 14. Proposed timeline of work to be completed during the year. Source: Martinez-Morales, A. A., Battery & Energy Projects, 2011.

11 Conclusion One-dimensional nanostructures are desirable for enhancing battery performance: Large surface to volume ratio increasing the contact with electrolyte Efficient electron conducting pathways for ions through the electrodes A geometry that can promote facile strain relaxation during operation May one day lead to the creation of battery technology capable of meeting future energy needs

12 Acknowledgements We would like to thank the CCRAA program for funding this project.

13 References Chen, Y., Tarascon, J.-M., and Guery, C. Electroche. Comm. 13, 673 (2011). Executive Summary of the DOE Basic Energy Sciences Workshop. Report of the Basic Energy Sciences Workshop on Electrical Energy Storage (2007). Fergus, J. W. Journal of Power Sources, 195, (2010). Liu, J., Cao, G., Yang, Z., Wang, D., Dubois, D., Zhou, X., Graff, G., Pederson, L., and Zhang, J. ChemSusChem., 1, (2008). Martinez-Morales, A. A. UC Riverside Bourns College of Engineering Battery and Energy Projects, (2011). Scrosati, B. and Garche, J. Journal of Power Sources 195, (2010). Singh, K. V., Martinez-Morales, A. A., Senthil Andavan, G. T., Bozhilov, K. N., and Ozkan, M. Chem. Mater., 19, 2446 (2007).