Surface Analytical Study Regarding the Solid Electrolyte Interphase Composition of Nanoparticulate SnO2 Anodes for Li-Ion Batteries

This work presents a comparative surface analytical study on the solid electrolyte interphase (SEI) composition influenced by additives in the electrolyte using nanoparticulate SnO2 as anode active material for lithium-ion batteries (LIBs). In particular, lithium bis(trifluoromethanesulfonyl)imide (LiTESI)-based electrolytes in combination with vinylene carbonate (VC) and 1-fluoroethylene carbonate (FEC) as electrolyte additives are used. The SEI composition of the electrodes is investigated at two different aging stages by means of the complementary X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS), providing chemical and molecular information on the topmost surface layers. We are able to show that the additives evolve different influences on the chemical composition of the formed SEI. The use of both additives generally results in an improved cycling stability of the nanoparticulate SnO2 anodes. In consequence, these results open an effective possibility to improve the cycling stability of SnO2-based electrode materials for LIBs by defined tailoring of the electrolyte's SEI composition.