The Synergistic Effect of Aramid Nanofibers and Carbon Nanotubes on Micro-Silicon Anodes for Improved Stability and Conductivity.

Despite the continuous development of energy storage, the challenges faced by micro-silicon anode pulverization have yet to be effectively addressed. In this work, the aramid nanofibers (ANFs) are in situ protonated on the surface of silicon micro-particles (SMPs), and also act as surfactants to bundle the carbon nanotubes (CNTs) to form ANF/CNT networks on SMPs (ANF/CNT/SMPs) at the same time. The results demonstrate that the dual-coating not only inhibits expansion and enhances structural stability but also improves conductivity, thereby promoting the cycling stability of micro-silicon anodes. The ANF/CNT/SMP anode shows cycling stability of 454 mAh g-1 at 0.2 A g-1 after 200 cycles. The expansion in thickness of the ANF/CNT/SMP electrode can be reduced by 51.5% after 100 cycles compared with the SMP electrode. The findings provide a novel approach for mitigating expansion in micro-silicon anodes through the combined coating of ANFs and CNTs.

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.