Revealing lithium-silicide phase transformations in nano-structured silicon-based lithium ion batteries via in situ NMR spectroscopy.
Nano-structured silicon anodes are attractive alternatives to graphitic carbons in rechargeable Li-ion batteries, owing to their extremely high capacities. Despite their advantages, numerous issues remain to be addressed, the most basic being to understand the complex kinetics and thermodynamics that control the reactions and structural rearrangements. Elucidating this necessitates real-time in situ metrologies, which are highly challenging, if the whole electrode structure is studied at an atomistic level for multiple cycles under realistic cycling conditions. Here we report that Si nanowires grown on a conducting carbon-fibre support provide a robust model battery system that can be studied by (7)Li in situ NMR spectroscopy. The method allows the (de)alloying reactions of the amorphous silicides to be followed in the 2nd cycle and beyond. In combination with density-functional theory calculations, the results provide insight into the amorphous and amorphous-to-crystalline lithium-silicide transformations, particularly those at low voltages, which are highly relevant to practical cycling strategies.
Department of Engineering, University of Cambridge, 9 JJ Thomson Avenue, Cambridge CB3 0FA, UK.
K
K
Ogata
1] Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, UK [2].
E
E
Salager
Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, UK.
C J
CJ
Kerr
Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, UK.
A E
AE
Fraser
Department of Material Science and Metallurgy, University of Cambridge, Pembroke Street, Cambridge CB2 3QZ, UK.
C
C
Ducati
Cavendish Laboratory, University of Cambridge, 19 JJ Thomson Avenue, Cambridge CB3 0HE, UK.
A J
AJ
Morris
Department of Engineering, University of Cambridge, 9 JJ Thomson Avenue, Cambridge CB3 0FA, UK.
S
S
Hofmann
1] Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, UK [2] Department of Chemistry, Stony Brook University, Stony Brook, New York 11794-3400, USA.
C P
CP
Grey