Effects of intermetallic phases on the electrochemical properties of rapidly-solidified Si-Cr alloys for rechargeable Li-ion batteries

• Published in: Journal of the Korean Physical Society Vol. 69; no. 5; pp. 875 - 879
• Main Authors: Ha, Jeong Ae, Jo, In Joo, Park, Won-Wook, Sohn, Keun Yong
• Format: Journal Article
• Language: English
• Published: Seoul The Korean Physical Society 01.09.2016; Springer Nature B.V; 한국물리학회
• Subjects: Ball milling; Concentration (composition); Intermetallic compounds; Intermetallic phases; Lithium ions; Lithium-ion batteries; Mathematical and Computational Physics; Melt spinning; Particle and Nuclear Physics; Physics; Physics and Astronomy; Rapid solidification; Theoretical; 물리학; Li-ion secondary battery; Si-Cr alloys; Rapid solidification; 81.05.Bx; Anode materials; 81.07.-b; 89.20.Kk; Melt-spun ribbons
• ISSN: 0374-4884; 1976-8524
• DOI: 10.3938/jkps.69.875

The microstructures and the electrochemical properties of rapidly-solidified Si-Cr alloys of various compositions were investigated in order to elucidate the effects of intermetallic phases on the cyclic energy capacity of the materials. Rapidly-solidified ribbons of the alloys were prepared by using a melt-spinning process, which is one of the most efficient rapid-solidification processes. The ribbons were fragmented by using a ball-milling process to produce powders of the alloys. To examine the electrochemical characteristics of the alloys, we mixed each of the alloy powders with Ketjenblack ® , a conductive material, and a binder dissolved in deionized water and used it to form electrodes. The electrolyte used was 1.5-M LiPF 6 dissolved in ethyl carbonate/dimethyl carbonate/fluoroethylene carbonate. The microstructures and the phases of the alloys were analyzed by using scanning electron microscopy, transmission electron microscopy, and X-ray diffraction analyses. The obtained results showed that the microstructures of the rapidly-solidified Si-Cr alloys were composed of Si and CrSi 2 phases. Fine Si particles with diameters of 50 − 100 nm were observed in an eutectic constituent while the sizes of the primary Si and CrSi 2 phases were relatively larger at 500 − 900 nm. The specific energy capacities ( C ) of the Si-Cr alloys decreased linearly with increasing volume fraction ( f ) of the CrSi 2 phase as follows: C = −1,667 f + 1,978 after the 50th cycle. The Columbic efficiency after the 3rd cycle increased slightly with increasing volume fraction of the CrSi 2 phase; this was effective in improving the cycling capacity of the Si particles.