Solid–Electrolyte Interphase Evolution of Carbon‐Coated Silicon Nanoparticles for Lithium‐Ion Batteries Monitored by Transmission Electron Microscopy and Impedance Spectroscopy. Issue 7 (24th June 2015) - Van Havenbergh, Kristof
Abstract: The main drawbacks of silicon as the most promising anode material for lithium‐ion batteries (theoretical capacity=3572 mAh g −1 ) are lithiation‐induced volume changes and the continuous formation of a solid–electrolyte interphase (SEI) upon cycling. A recent strategy is to focus on the influence of coatings and composite materials. To this end, the evolution of the SEI, as well as an applied carbon coating, on nanosilicon electrodes during the first electrochemical cycles is monitored. Two specific techniques are combined: Transmission Electron Microscopy (TEM) is used to study the surface evolution of the nanoparticles on a very local scale, whereas electrochemical impedance spectroscopy (EIS) provides information on the electrode level. A TEM–EELS fingerprint signal of carbonate structures from the SEI is discovered, which can be used to differentiate between the SEI and a graphitic carbon matrix. Furthermore, the shielding effect of the carbon coating and the thickness evolution of the SEI are described. Abstract : Transmitting battery research: The impact of a thin carbon coating at the surface of Si nanoparticles on the formation and evolution of the solid–electrolyte interphase (SEI). Transmission electron microscopy (TEM) measurements demonstrate a shielding effect of the carbon coating on the native SiO2 layer, whereas electrochemical impedance spectroscopy (EIS) measurements enable the fast monitoring of the SEI formation on the electrode level.