Designed Formation of Yolk-Shell-Like N-Doped Carbon-Coated Si Nanoparticles by a Facile Method for Lithium-Ion Battery Anodes

Silicon (Si) is considered as a promising anode material for lithium-ion batteries (LIBs) because of its ultrahigh capacity (3579 mA h g^-1, Li₁₅Si₄). However, the irreversible huge volume change during cycling and poor conductivity hinder its practical application. Nanoscale shortens electron and ion transport paths and provides more active sites. To solve these problems, yolk-shell-like N-doped carbon-coated Si nanoparticles (Si@void@NC) were designed and prepared by a simple solution coating method and a high-temperature calcination process. Si@void@NC exhibits two advantages: First, the prepared hollow structure is favorable for buffering the volume expansion. Second, the N-doped carbon layer coating on Si can improve the conductivity and reduce the volume change during cycling. The as-prepared sample exhibits 697.7 mA h g^-1 at 0.2 A g^-1 after 100 cycles and a capacity retention of 475.1 mA h g^-1 at 0.5 A g^-1 after 400 cycles. This strategy of designation and preparation of yolk-shell-like N-doped carbon-coated Si nanoparticles provides a way to construct ideal Si-based composite materials for LIBs.