Fundamental Approach to Capacity Prediction of Si-Alloys as Anode Material for Li-ion Batteries

et al. 2022

J. Electrochem. Soc.

While silicon has a very high theoretical capacity but the stresses produced by volume changes during charge/discharge cycling lead to structural modifications (around 300 %). To overcome this problem, many studies are being conducted to commercialize silicon. Herein, we produced amorphous silicon alloy using a melt-spinning method. Then, through annealing under various temperatures, we gradually recrystallized the silicon phase. Average silicon grain sizes were 70 and 130 nm for silicon alloys annealed at 800 and 873 K, respectively. The initial reversible capacities of silicon alloy-based anodes were 844.3 (800 K) and 865.1 mAh g-1 (873 K), and, after 100 cycles capacity retention rates were found to be 68.5 (800 K) and 40.5 % (873 K). At this stage, to elucidate the effect of grain sizes on cycle life retention rate, we determined mechanical hardness through nanoindentation, and, by measuring volume expansion values between cycles through in-situ dilation, we could identify the relationship between electrochemical property and mechanical hardness of silicon alloy samples depending on recrystallized grain sizes. Thus, by analyzing the mechanical and electrochemical properties of silicon alloys depending on silicon grain sizes, we want to highlight the importance of controlling silicon grain size.

“…Thus, we can expect a good effect in improving the cycle life of LIB. 14,15 Debye-Scherrer Eq. 1 is to determine the average grain size through XRD peak analysis: 16…”

Section: Resultsmentioning

confidence: 99%

Relationship between Mechanical and Electrochemical Property in Silicon Alloy Designed by Grain Size as Anode for Lithium-Ion Batteries

Umirov

et al. 2022

J. Electrochem. Soc.

“…In all three compositions, the weight of Si was fixed at 50%, and only the ratios of titanium and aluminum were adjusted. The theoretical capacities of the samples, which are estimated by the lever rule using the phase diagram [35], are listed in Table 1. The alloys were fabricated into ribbons using the melt-spinning method.…”

Section: Methodsmentioning

confidence: 99%

Optimal Synthesis and Application of a Si–Ti–Al Ternary Alloy as an Anode Material for Lithium-Ion Batteries

Lee

Kim³

et al. 2021

Materials

The development of novel anode materials for high energy density is required. Alloying Si with other metals is a promising approach to utilize the high capacity of Si. In this work, we optimized the composition of a Si–Ti–Al ternary alloy to achieve excellent electrochemical performance in terms of capacity, cyclability, and rate capability. The detailed internal structures of the alloys were characterized through their atomic compositions and diffraction patterns. The lithiation process of the alloy was monitored using real-time scanning electron microscopy, revealing that the mechanical stability of the optimized alloy was strongly enhanced compared to that of the pure silicon material.

“…The high-purity elements of Si (99.9%), Al (99.999%), and Fe (99.9%) were purchased from Taewon Scientific Co. The Si–Al–Fe alloy ribbons were produced under an argon atmosphere by the arc melting of corresponding elements followed by the melt-spinning technique (at the linear velocity of 40 m s –1 ), as described elsewhere. , The composition of the as-prepared alloy was designed as 50, 33, 17 atom % of Si, Al, and Fe, respectively, to obtain a stable melt-spun amorphous alloy in a ribbon form with the thickness of 6–8 μm. Thereafter, the ribbon strips were mechanically crushed by wet milling in an n-hexane solution using a mixer (TSI Co. Ltd., Corona Mix CRM1.5L) for 15 min with the powder to Zr ball ratio of 1:40.…”

Section: Methodsmentioning

confidence: 99%

Pragmatic Approach to Design Silicon Alloy Anode by the Equilibrium Method

Umirov

Seo

ACS Appl. Mater. Interfaces

et al. 2020

Self Cite

Silicon fascinates with incredibly high theoretical energy density as an anode material and considered as a primary candidate to replace well-established graphite. However, further commercialization is hindered by the abnormal volume changes of Si in every single cycle. Silicon embedded in a buffer matrix using the melt-spinning process is a promising approach; however, its metastable nature significantly reduces the microstructure homogeneity, the quality of the composition, and, therefore, the electrochemical performances. Herein, we developed a new approach to design a high-performance Si-alloy with improved microstructure uniformity and electrochemical properties. Namely, annealing at a certain temperature of the melt-spun amorphous alloy ribbon allowed us to evenly distribute Si nanocrystallites in the microstructure with control of average grain size. As a result, the Si-alloy electrode delivers an initial discharge capacity of 900 mAh g–1 and exhibits a high coulombic efficiency of >99% from the second cycle with a capacity retention of ∼98% after 100 cycles. This study provides powerful insights and evidence for the successful application of the proposed approach for commercial purposes.