Hierarchical Carbon Shell Compositing Microscale Silicon Skeleton as High-Performance Anodes for Lithium-Ion Batteries

Si is a promising high-capacity anode material; however, its practical implementation is hindered by its huge volume expansion, low initial Coulombic efficiency (ICE), poor cycling life, and high cost. To address these issues, a novel microscale Si skeleton (MSS) material is synthesized, and a dual carbon-hybridized MSS hierarchical architecture composite (MSS@CC@CS) is fabricated by a conformal carbon first coating and nonfilling carbon shell secondary encapsulation. The MSS consisting of interconnected Si nanoskeletons and continuous interpenetrating pores avoids pulverization and accommodates volume expansion, resulting in low electrode swelling. The conformal carbon coating enhances the internal conductivity and structural stability of MSS, and the carbon shell encapsulation further strengthens the structural integrity and greatly improves the ICE of the Si anode. As an anode, MSS@CC@CS shows a high ICE of 90.5%, a high half-cell capacity of 1353.8 mA h g-1 at 0.5 C with 89.8% capacity retention after 800 cycles, and a low electrode swelling of 12.4%. Paired with a commercial NCA cathode after blending graphite to assemble a 3.5 A h cylindrical cell, an energy density of 286.4 W h kg-1 and superior cycle performance with 82.7% capacity retention after 1200 cycles are achieved, showing a great application potential in powering large devices.