Simultaneously manipulating carbon coating layers and void structures in silicon/carbon anode materials via bifunctional templates for lithium-ion batteries

The carbon coating strategies, ameliorating structure instability and reaction kinetics of silicon anodes upon lithiation/delithiation, have been chronically plagued by an electrochemical contradiction between a high specific capacity from a high silicon content and a long cycle life from a high carbon content. Herein, the carbon coating layers and void structures for silicon/carbon composites were simultaneously manipulated through a precisely grown Al2O3 template, which induced a controllable polydopamine polymerization through its mild interfacial interaction with Tris-buffer solution and created abundant void spaces by its residual parts. Particularly, the as-optimized silicon/carbon composite with an ultrahigh silicon content of 89.3 wt% could demonstrate a large initial reversible capacity of 2583 mAh g-1 with an 82.1 % coulombic efficiency at 200 mA g-1, a remarkable cycling durability of 601 mAh g-1 after 990 cycles at 2000 mA g-1, and an excellent rate capability of 887 mAh g-1 at 4000 mA g-1. The uniform void structures could maintain the structural stability/integrity of silicon, boost reaction kinetics across electrode/electrolyte interfaces, and suppress the uncontrollable formation/evolution of solid electrolyte interphases upon cycling. This novel research on synchronously regulating carbon layers and void structures in silicon/carbon composites would enlighten a rational development of highcapacity and long-life silicon anodes.