Rational Design of Ion-Conductive Layer on Si Anode Enables Superior-Stable Lithium-Ion Batteries.

Silicon (Si) is considered a promising commercial material for the next-generation of high-energy density lithium-ion battery (LIB) due to its high theoretical capacity. However, the severe volume changes and the poor conductivity hinder the practical application of Si anode. Herein, a novel core-shell heterostructure, Si as the core and V3 O4 @C as the shell (Si@V3 O4 @C), is proposed by a facile solvothermal reaction. Theoretical simulations have shown that the in-situ-formed V3 O4 layer facilitates the rapid Li+ diffusion and lowers the energy barrier of Li transport from the carbon shell to the inner core. The 3D network structure constructed by amorphous carbon can effectively improve electronic conductivity and structural stability. Benefiting from the rationally designed structure, the optimized Si@V3 O4 @C electrode exhibits an excellent cycling stability of 1061.1 mAh g-1 at 0.5 A g-1 over 700 cycles (capacity retention of 70.0%) with an average Coulombic efficiency of 99.3%. In addition, the Si@V3 O4 @C||LiFePO4 full cell shows a superior capacity retention of 78.7% after 130 cycles at 0.5 C. This study opens a novel way for designing high-performance silicon anode for advanced LIBs.

Vanadium-Tailored Silicon Composite with Furthered Ion Diffusion Behaviors for Longevity Lithium-Ion Storage.

As one of the promising anode materials, silicon has attracted much attention due to its high theoretical specific capacity (∼3579 mAh g-1) and suitable lithium alloying voltage (0.1-0.4 V). Nevertheless, the enormous volume expansion (∼300%) in the process of lithium alloying has a great negative effect on its cyclic stability, which seriously restricts the large-scale industrial preparation of silicon anodes. Herein, we design a facile synthesis strategy combining vanadium doping and carbon coating to prepare a silicon-based composite (V-Si@C). The prepared V-Si@C composite does not merely show improved conductivity but also improved electrochemical kinetics, attributed to the enlarged lattice spacing by V doping. Additionally, the superiority of this doping strategy accompanied by microstructure change is embodied in the relieved volume changes during the repeated charging/discharging process. Notably, the initial capacity of the advanced V-Si@C electrode is 904 mAh g-1 (1 A g-1) and still holds at 1216 mAh g-1 even after 600 cycles, showing superior electrochemical performance. This study offers an alternative direction for the large-scale preparation of high-performance silicon-based anodes.