(Invited) A Study of Si-based Metallic Glass Anodes for Li-ion Batteries
Authors: Kostecki Robert , Cha Hyungyeon , Dopilka Andrew , Haddad Andrew , Larson Jonathan M. , Gu Yueran , Arano Khryslyn , Veith Gabriel M. , Zorba Vassilia 
Published: December 2024

Silicon has been considered a promising low-cost negative electrode material for high-energy lithium-ion batteries due to its high gravimetric (400 Wh kg–1) and volumetric energy density (> 800 Wh L–1), low operating voltage (~0.3 V) and abundance in the Earth crust. During the past decades, development of Si-based negative electrodes has been greatly accelerated by modification of morphology, size, composition, and surface engineering. Accordingly, the cycle life of Si-based cells has improved dramatically over the years and is now approaching performance targets showing > 300 Wh kg–1 even after 1,000 cycles. However, as Si is gradually adopted into commercial batteries, the calendar life of the Si-based cells with high silicon content (>40%) is identified to be insufficient (1-2 years) and thus represents a major roadblock to widespread deployment. Interfacial instability of silicon in organic carbonate carbonate electrolytes and continuous electrolyte decomposition lead to a gradual electroyte consumption and shift of active lithium inventory in the cell. A steady growth of the SEI layer accompanies is linked with active lithium loss, which causes severe cell capacity fade and impedance rise. To prevent such a Si negative electrode and cell degradation mechanism, it is essential to exercise better control over the kinetics of electrolyte reduction and SEI layer formation process.
Among various approaches to improve the interfacial as well as mechanical stability of silicon, embedding metallic inactive phases into amorphous Si matrix was widely studied. Dahn et al. has demonstrated this idea through a series of studies of over 200 different Si-based amorphous alloys1-3. Amorphous Si-alloys suppress two-phase coexistence of the Li-rich and Li-poor phase which leads to lattice mismatch and crack propagation. Thus, amorphous alloy films showed better capacity retention with less swelling and particle collapse. Furthermore, the inactive metal matrix serves as a buffer for the large volume expansion of Si (~280%), thus improving cycle stability without a significant decrease in the volumetric energy density.
In this study we report on the synthesis and evaluation of Silicon-Me amorphous alloys (Me: Ni, Cu, Mn, Ti, Fe) for applications as negative electrodes in high-energy density Li-ion batteries with improved calendar life. Numerous Si-Me metallic glass alloy model electrodes were synthesized, using ultra-fast laser and splat quenching techniques to screen, evaluate, and optimize their electrochemical performance with a focus on the long-term interfacial stability in Li-ion batteries. Si0.85Ni0.15 has emerged as the best performing metallic glass alloy composition and its fabrication was successfully scaled-up with melt spinning technique. The melt-spun Si0.85Ni0.15 thin ribbon was ball-milled into fine powder to be used in conventional composite electrode fabrication for Li-ion batteries. Metallic glass Si0.85Ni0.15 anode showed improved passivation behavior and outperformed a conventional nano-sized Si electrode in both cycle and calendar life tests.
Acknowledgements
This research was supported by the US Department of Energy (DOE)’s Vehicle Technologies Office under the Silicon Consortium Project directed by Brian Cunningham and managed by Anthony Burrell. The work at the Molecular Foundry was supported by the Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy under Contract no. DE-AC02-05CH11231. This research also used resources of the Advanced Light Source, a U.S. DOE Office of Science User Facility under contract no. DE-AC02-05CH11231; in particular, Beamline 2.4 was used. Melt-spinning production rates and metrics are provided from ECO FM Co.

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