Lithium transition metal silicates Li2M
= Fe, Mn, Co, etc
, well-known for their 2-Li theoretical capacity, draw increasingly more attention. In this text, we propose a hydrothermal method3
to obtain phase-pure nanoscale lithium iron silicate Li2
for probing its electrochemical performance as Li-ion battery cathode. Two types of Li2
crystals are prepared, namely low-temperature monoclinic phase and high-temperature orthorhombic phase and their electrochemical performance is found to be strongly structure-depended. As a result, the electrochemistry-structure relationships are systematically investigated using in-situ
synchrotron XRD/XANES characterizations and first-principles calculations. The results demonstrate that there are obvious phase transitions for the metastable monoclinic Li2
electrode upon cycling4
and the Li ion has poor diffusion kinetics with activation energy of minimum 0.80 eV in both structures. Furthermore the charge compensation mechanism is discussed by XANES and calculations in monoclinic Li2
structure for more than one Li extraction. All of these findings reveal some missing links in our fundamental comprehension of these materials and provide ideas for designing/obtaining improved silicate cathode materials.
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. Gummow, R. J., He, Y., Recent progress in the development of Li2MnSiO4 cathode materials. J. Power Sources, 253, 253, 315-331 (2014).
3. Wei, H.J. et al. Synthesis and Characterization of Li2FeSiO4 as Candidate High-Capacity Li-ion Battery Cathode Material. 227th ECS Meeting, May 24-28 (2015), Chicago, Illinois, USA.
4. Xia Lu, Huijing Wei, Hsien-Chieh Chiu, Raynald Gauvin, Pierre Hovington, Abdelbast Guerfi, Karim Zaghib and George P. Demopoulos, Rate-dependent phase transitions in Li2FeSiO4 cathode nanocrystals, Sci. Re. in revision (2014).