Slow Stabilization of Si-Li Alloys Formed during Charge and Discharge of a Si-C Mixed Electrode Studied by In Situ Solid-State 7Li Nuclear Magnetic Resonance Spectroscopy. Issue 1 (1st January 2017)

• Record Type: Journal Article
• Authors: Arai, J.; Gotoh, K.; Sayama, R.; Takeda, K.
• Is Part Of: Journal of the Electrochemical Society. Volume 164:Issue 1(2017)
• Page Start: A6334
• Page End: A6340
• Publication Date: 2017-01-01
• Subjects: EIS -- in situ NMR -- Li Battery -- Lithium NMR -- Si anode; Electrochemistry -- Periodicals; 541.3705
• DOI: 10.1149/2.0541701jes
• Languages: English
• ISSNs: 0013-4651

Abstract

Abstract : The charge–discharge behavior of a Si-C mixed electrode (Si:graphite = 20:80 or 30:70 (wt%)) was investigated using in situ solid-state 7 Li nuclear magnetic resonance (NMR) spectroscopy. The spectra revealed the formation of Li-Si alloys and the intercalation of Li into graphite during the charge process and the corresponding reverse process (Li extraction) during discharge. Li was mainly stored as a Li-Si alloy (Li15 Si4 or Li15+δ Si4 ) at high SOC (state of charge) values (above 80% SOC, low cell voltage region) and could be released from the alloy. The cell resistance measured by electrochemical impedance spectroscopy (EIS) increased steeply at high SOC values, revealing that structural changes in the Li-Si alloy may influence the electrode resistance. The NMR peaks observed upon formation of Li15 Si4 or Li15+δ Si4 shifted and decreased gradually, indicating that the Li-Si alloys are not sufficiently stable in the cell.