Performance of electrochemically generated Li21Si5 phase for lithium-ion batteries

✍ Scribed by Ji Y. Kwon; Ji Heon Ryu; Seung M. Oh

• Publisher: Elsevier Science
• Year: 2010
• Tongue: English
• Weight: 457 KB
• Volume: 55
• Category: Article
• ISSN: 0013-4686
• DOI: 10.1016/j.electacta.2010.01.054

✦ Synopsis

The nature of Li-Si alloy phases that are generated in electrochemical lithiation is examined as a function of temperature. The electrochemical lithiation is performed at 0.0 V (vs. Li/Li + ) by shortcircuiting an amorphous Si thin-film electrode with a Li metal counter electrode. At 25-85 • C, the well-known Li 15 Si 4 phase (theoretical specific capacity = 3580 mA h g -1 ) forms. At 100-120 • C, however, Li 21 Si 5 (4008 mA h g -1 ) that is known to be the most Li-rich phase in Li-Si system is generated. The crystallization into Li 21 Si 5 is, however, so kinetically slow that it does not appear in the transient cycling experiment. The Li 21 Si 5 phase is converted to amorphous Si upon de-lithiation, but the restoration back to the initial phase is only observed at 100-120 • C after a prolonged lithiation at 0.0 V. The cycleability of this phase is poor due to a successive Li trapping inside the Si matrix, which is caused by the formation of electrically isolated Si islands.