Journal
ACS APPLIED MATERIALS & INTERFACES
Volume 11, Issue 21, Pages 19372-19380Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acsami.9b03931
Keywords
coaxial; half-cell; full-cell; prelithiation; preconditioning; ex situ
Funding
- Science Foundation Ireland (SFI) [16/IA/4629, 11-PI-1148]
- SFI [SFI 16/M-ERA/34I9]
- Irish Research Council through the Government of Ireland Postgraduate Scheme
- Enterprise Ireland [CF20144014]
- Science Foundation Ireland (SFI) [16/IA/4629] Funding Source: Science Foundation Ireland (SFI)
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Herein, we report the formation of core@shell nanowires (NWs) comprised of crystalline germanium NW cores with amorphous silicon shells (Ge@aSi) and their performance as a high capacity Li-ion battery anode material. The Ge NWs were synthesized directly from the current collector in a solvent vapor growth (SVG) system and used as hosts for the deposition of the Si shells via a plasma-enhanced chemical vapor deposition (PECVD) process utilizing an expanding thermal plasma (ETP) source. The secondary deposition allows for the preparation of Ge@aSi core@shell structures with tunable Ge/Si ratios (2:1 and 1:1) and superior gravimetric and areal capacities, relative to pure Ge. The binder-free anodes exhibited discharge capacities of up to 2066 mAh/g and retained capacities of 1455 mAh/g after 150 cycles (for the 1:1 ratio). The 2:1 ratio showed a minimal similar to 5% fade in capacity between the 20th and 150th cycles. Ex situ microscopy revealed a complete restructuring of the active material to an interconnected Si1-xGex morphology due to repeated lithiation and delithiation. In full-cell testing, a prelithiation step counteracted first cycle Li consumption and resulted in a 2-fold improvement to the capacity of the prelithiated cell versus the unconditioned full-cells. Remarkable rate capability was also delivered where capacities of 750 mAh/g were observed at a rate of 10 C.
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