Constructing robust and freestanding MXene/Si@C core-shell nanofibers via coaxial electrospinning for high performance Li-ion batteries

Silicon (Si) is a promising anode for Lithum-ion batteries (LIBs) due to its high theoretical capacity (4200 mA h g(-1)). However, low initial Coulombic efficiency (ICE) and utilization efficiency due to volume expansion and poor conductivity hinder the practical application of Si. Herein, a facile coaxial electrospinning method is adopted to fabricate core-shell MXene/Si@C nanofibers, which have a number of unique structure advantages in improving the performance of Si particles. MXene nanosheets as a conductive substrate effectively bridge the Si particles and carbon shell to form the conductive network of the MXene/Si@C nanofibers, which is beneficial for fast charge transfer and facile lithium ion migration. The robust carbon shell and MXene nanosheets offer double accommodation for huge Si volume expansion during charge/discharge, maintaining the structural stability of the electrodes. Moreover, abundant functional group defects associated with the carbon shell and MXene synergistically contribute the additional capacitive capacity. Therefore, the obtained MXene/Si@C nanofibers as a freestanding anode for LIBs present remarkable electrochemical performance, i.e., a high capacity of 1083 mA h g(-1) at 0.1 A g(-1), an excellent rate performance of 301.1 mA h g(-1) at 2 A g(-1), high Si utilization efficiency up to 86% and a high ICE of over 78.4%. A facile coaxial electrospinning technique to construct the core-shell structure of multiple components has the potential to improve the electrochemical performance and facilitate the practical application of Si.

Automated summary

The study utilized a facile coaxial electrospinning method to fabricate MXene/Si@C nanofibers, addressing the challenges of silicon in lithium-ion batteries. The nanofibers showed structural advantages in improving silicon particle performance, fast charge transfer, and lithium ion migration. Excellent electrochemical performance was achieved in the experiments, laying the foundation for the practical application of silicon.