Monday, 20 June 2016
Riverside Center (Hyatt Regency)
B. Moeremans, Y. Zheng (Hasselt University), R. F. Duarte (Helmholtz-Zentrum Berlin), D. Deduytsche, C. Detavernier (Ghent University), M. Hahlin (Uppsala University), H. G. Boyen (Hasselt University), A. Hardy, M. K. Van Bael (imomec, imec), and F. U. Renner (IMEC vzw. Division IMOMEC)
Increasing the capacity of Li-ion batteries and making the involved interfaces much more stable is one of the crucial current challenges for sustainable energy use.
1 Silicon anodes promise almost a 10-fold capacity increase with respect to conventional graphite anodes.
2 The continuous degradation of the Solid Electrolyte Interphase (SEI) at the surface of silicon-based anode materials has been recognized as the key problem of these electrodes, currently preventing their commercial introduction.
3 The effect of the addition of additives to the electrolyte has been investigated in the past on graphite anodes, resulting in the use of FEC and VC in commercial lithium-ion batteries. However, due to the severe volume expansion of silicon during battery cycling, the SEI is under much higher stresses compared to graphite. Hence the stabilization of the SEI on silicon is required to improve its battery performance.
Here we present a methodology to specifically introduce polymer species into the SEI. We analyzed the interfacial film using Hard X-ray Photoelectron Spectroscopy (HAXPES), Raman spectroscopy and electrochemical testing. HAXPES enabled us to address the full depth-dependent layer chemistry and allowed us to probe the interface of the solid-electrolyte interphase and the silicon-based electrode. Figure 1a shows the C1s spectrum of the SEI on a silicon based anode after cycling using a standard electrolyte and for Figure 1b an electrolyte with the monomer additive. A detailed analysis gives information on the SEI layer thickness and the distribution of the additive-based polymer formation. In particular Br2p3/2 HAXPES spectra reveal more details on the mechanism. The battery performance of the additives was investigated by coin-cell battery testing and provides a more detailed view into the influence of electrolyte additives on the SEI.
REFERENCES
1. J. B. Goodenough and K.-S. Park, J. Am. Chem. Soc. 135, 1167-1176 (2013).
2. M. N. Obravac and L. Christensen, Electrochemical and Solid-State Letters 7, A93-A96 (2004).
3. B. Philippe, K. Edström et al., Chemistry of Materials 24, 1107-1115 (2012).
