Electrochemical performance and surface chemistry of nanoparticle Si@SiO2 Li-ion battery anode in LiPF6-based electrolyte

• Si@SiO2 nanoparticles were synthesized by plasma chemical method.
• Chemical interaction between Si@SiO2 and LiPF6 was discovered.
• A layer of solid products LiF, LiPO3, and P forms on Si@SiO2 surface before SEI formation.
• This layer influences the electrochemical behavior of Si@SiO2 in the LiPF6-based electrolyte.
• Degradation of Si@SiO2-based anode upon long-term cycling is mainly caused by LiF formation.

Nanoparticles with a core-shell structure of Si@SiO2 with an average size of about 50 nm were obtained by plasma chemical synthesis through the decomposition of monosilane. Electrochemical impedance spectroscopy (EIS) was used to study the behavior of anodes based on the composite Si@SiO2 during the cyclic charge/discharge. Based on the results of Si@SiO2 anodes studies by scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) in conjunction with thermodynamic modeling (TM), assumptions were made about chemical and electrochemical processes occurring during prolonged cycling in the electrolyte 1 M LiPF6 in ethylene carbonate/diethyl carbonate (1:1 v/v).

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