Core-shell yolk-shell Si@C@Void@C nanohybrids as advanced lithium ion battery anodes with good electronic conductivity and corrosion resistance

Abstract

Yolk-shell [email protected]@C nanostructure has greatly improved the low Li+/electron conductivity and buffered the huge volume variation of Si, whereas the surface corrosion and passivation of the Si yolks in electrolytes still limit the lithium storage capability. Herein, core-shell yolk-shell [email protected]@[email protected] nanohybrids were proposed and successfully prepared for the first time. Compared with [email protected]@C, the newly-proposed structure introduced core-shell [email protected] nanoparticles as the yolks instead. Such extra carbon shell can not only decrease the electrical resistance between Si yolks and hollow carbon shells but also effectively protect Si yolks from electrolyte corrosion, i.e., the formation of Li2SiF6 layers on Si surface confirmed by X-ray diffraction and transmission electron microscopy. As a result, the [email protected]@[email protected] electrodes exhibited remarkably enhanced reversible capacity, cycling stability (∼1366 mA h g−1 after 50 cycles at 500 mA g−1, with a capacity retention of ∼71% with respect to the initial reversible capacity of 1910 mAh g−1 at 100 mA g−1), and rate performance (with a capacity retention of ∼60% at 4000 mA g−1). This work shows the paramount role of the inner carbon shell of [email protected]@[email protected] in limiting the electrolyte corrosion and probably improving the electronic conductivity.