Improving the lithium storage properties of Fe2O3@C nanoparticles by superoleophilic and superhydrophobic polysiloxane coatings

The remarkable effect of superhydrophobicity and superoleophilicity on the lithium storage properties of Fe2O3@C nanoparticles in lithium ion batteries was investigated for the first time. Fe2O3@C nanoparticles were treated with methyltrichlorosilane to form nanorod-like polysiloxane coatings on their surface. The wettability of the pristine and polysiloxane-coated Fe2O3@C nanoparticles to water as well as electrolytes, and its impact on reversible capacity and cycling performance were comparatively studied. Contact angle measurements revealed that the polysiloxane-coated nanoparticles fast and selectively absorbed electrolytes while completely repelled water, exhibiting superhydrophobic and superoleophilic properties. Electrochemical measurements showed that polysiloxane-coated Fe2O3@C nanoparticles exhibited much higher capacity and better cycleability than the pristine Fe2O3@C counterparts. The improved electrochemical properties are ascribed to the selective wettability of polysiloxane-coated Fe2O3@C nanoparticles to electrolyte and water, which facilitates the formation of a more homogeneous, compact and thinner solid electrolyte interface (SEI) layer on the surface of the treated nanoparticles than that on the pristine counterparts. The presence of polysiloxane coatings also effectively buffer the volume change of Fe2O3 active materials in the process of lithiation and delithiation. The results of this study might provide a novel application of special wettability in the field of power sources as well as an alternative insight into the factors affecting the lithium storage performance of electrode materials.