Vertical Graphene Sheet-Encapsulated Silicon Nanoparticles for Anodes of Polymer-Based All-Solid-State Batteries

Substituting Li metal with silicon (Si) as the anode, owing to its high capacity, presents significant promise in polymer-based all-solid-state batteries (ASSBs) for mitigating lithium dendrite formation. However, Si anodes suffer from poor conductivity, substantial volume expansion during cycling, and unfavorable interfacial stability with solid-state electrolytes, resulting in severe capacity degradation and rendering them unsuitable for direct application. Herein, we report that vertical graphene sheets are grown on Si nanoparticles (Si@VG) by thermal chemical vapor deposition for the operation of polymer-based ASSBs. Flexible vertical graphene sheets not only form a 3D conductive network to enhance the electrical connectivity of the whole electrode but also attain a better contact with the solid polymer electrolyte for reducing the interface impedance. As the anode for ASSBs, the reversible capacity of Si@VG remains 444.9 mAh g^-1 after 200 cycles at 0.5 A g^-1, which exhibits significant improvement relative to Si. In addition, it can be observed from electrochemical impedance spectroscopy that the interfacial impedance between the anode and the solid polymer electrolyte significantly decreases. This study can provide valuable insights for other research endeavors aimed at addressing the interfacial challenges in ASSBs.