title: Hard X-ray Photoelectron Spectroscopy (HAXPES) Investigation of the Silicon Solid Electrolyte Interphase (SEI) in Lithium-Ion Batteries.
abstract: Binder-free silicon (BF-Si) nanoparticle anodes were cycled with 1.2 M LiPF6 in ethylene carbonate (EC), fluoroethylene carbonate (FEC), or EC with 15% FEC (EC:FEC), extracted from cells and analyzed by Hard X-ray Photoelectron Spectroscopy (HAXPES). All of the electrolytes generate an SEI which is integrated with Si containing species. The EC and EC:FEC electrolytes result in the generation of LixSiOy after the first cycle while LixSiOy is only observed after five cycles for the FEC electrolyte. The SEI initially generated from the EC electrolyte is primarily composed of lithium ethylene dicarbonate (LEDC) and LiF. However, after five cycles, the composition changes, especially near the surface of silicon because of decomposition of the LEDC. The SEI generated from the EC:FEC electrolytes contains LEDC, LiF, and poly(FEC) and small changes are observed upon additional cycling. The SEI generated with the FEC electrolyte contains LiF and poly(FEC) and small changes are observed upon additional cycling. The stability of the SEI correlates with the observed capacity retention of the cells.
authors: Physical Sciences Department, Rhode Island College , Providence Rhode Island 02908, United States.
authors: Benjamin T
authors: BT
authors: Young
authors: David R
authors: DR
authors: Heskett
authors: Cao Cuong
authors: CC
authors: Nguyen
authors: Mengyun
authors: M
authors: Nie
authors: National Institute of Standards and Technology , Gaithersburg, Maryland 20899, United States.
authors: Joseph C
authors: JC
authors: Woicik
authors: Brett L
authors: BL
authors: Lucht
keywords: HAXPES; Silicon anode; XPS; electrolyte additives; ex-situ surface analysis; lithium ion battery; solid electrolyte interface