Synthesis and Characterization of Li2FeSiO4 As Candidate High-Capacity Li-Ion Battery Cathode Material

Due to the emerging needs of electrical and hybrid electrical vehicle applications, more research effort has been directed towards the next generation Li-ion storage materials, especially on high-capacity cathode materials. In this context, lithium transition metal silicates Li₂MSiO₄ (M = Fe, Mn, Co, etc.) ^1-5 are drawing increasingly more attention thanks to their high theoretical capacity due to the two lithium-ion extraction per formula unit. However lack of phase purity control during synthesis and phase transition reactions during delithiation/lithiation have imposed obstacles to their study and further development. Hereby, we investigate a novel dual step organic-assisted hydrothermal-annealing approach to obtain different lithium iron silicate polymorphs (monoclinic, orthorhombic, and mixed) for subsequent electrochemical evaluation and probing of their phase transition behavior. During the hydrothermal synthesis step, organic additives are used to control nanocrystal growth, which upon annealing lead to in-situ coating with nitrogen-doped carbon. The silicates are characterized by various techniques including XRD, FE-SEM, TEM, XPS, Raman spectroscopy, and XANES and demonstrate different structures and morphologies with various synthesis conditions, including annealing temperature, pH etc., which critically impact on their electrochemical properties.

References

1. Nyten, A., Abouimrane, A., Armand, M., Gustafsson, T. & Thomas, J. O. Electrochemical performance of Li₂FeSiO₄ as a new Li-battery cathode material. Electrochem Commun 7, 156-160, (2005).

2. Nishimura, S. I. et al. Structure of Li₂FeSiO₄. J Am Chem Soc 130, 13212-13213, (2008).

3.Boulineau, A. et al. Polymorphism and structural defects in Li₂FeSiO₄. Dalton Trans 39, 6310-6316, (2010).

4. Eames, C., Armstrong, A. R., Bruce, P. G. & Islam, M. S. Insights into Changes in Voltage and Structure of Li₂FeSiO₄ Polymorphs for Lithium-Ion Batteries. Chem Mater 24, 2155-2161, (2012)

5. R.J. Gummow, Y. He / Journal of Power Sources 253 (2014) 315-331, Recent progress in the development of Li2MnSiO4 cathode materials