Search

Carbon coatings can help to stabilize the electrochemical performance of high-energy anodes using silicon nanoparticles as the active material. In this work, the comparison of the behavior and chemical composition of the Solid Electrolyte Interphase (SEI) was carried out between Si nanoparticles and carbon-coated Si nanoparticles (Si@C). A combination of two complementary analytical techniques, Electrochemical Impedance Spectroscopy and X-ray Photoelectron Spectroscopy (XPS), was used to determine the intrinsic characteristics of the SEI. It was demonstrated that the SEI on Si particles is more resistive than the SEI on the Si@C particles. XPS demonstrated that the interface on the Si particles contains more oxygen when not covered with carbon, which shows that a protective layer of carbon helps to reduce the number of inorganic components, leading to more resistive SEI. The combination of those two analytical techniques is implemented to highlight the features and evolution of interfaces in different battery technologies. [ABSTRACT FROM AUTHOR]

• Optimized solvothermal synthesis of MnF 2 targeting high reaction yield and nanosized particles. • Investigation of ball-milling and electrode formulation to improve electrochemical activity of MnF2 in Li cells. • Aqueous formulation using sodium alginate as binder provides significant improvement of the electrochemical performance. • Alginate-based formulation is an alternative route to ball-milling for augmenting electrochemical activity of metal fluorides. Electrochemical activity of poorly conductive metal fluorides in Li-ion batteries is contingent on their nanostructuration to reduce diffusion lengths and increase reaction kinetics. In that regard, we optimize the synthesis and electrode formulation of MnF 2 to enable sufficient electrochemical activity required to study its electrochemical conversion reaction mechanism. Solvothermal synthesis in a water–ethanol mixture (1:1 Vol.), using Mn acetate and a slight excess of hydrofluoric acid (HF), results in pure phase, nanosized (˜30 nm diameter) rutile-type MnF 2 (P 4 2 /mnm). High energy ball-milling of MnF 2 ‒carbon mixtures leads to an amorphization of MnF 2 and its partial phase transformation to the α-PbO 2 -type structure, without significant improvement of the electrochemical performance. Changing the electrode binder, however, from typical polyvinylidene fluoride (PVDF) to water-soluble Na-alginate, leads to a significant improvement of the reversibility of the electrochemical reaction. We attribute this drastic improvement to the improved adherence and homogeneity of the electrode film prepared with Na-alginate. [ABSTRACT FROM AUTHOR]