Si@C@MoO2 spherical superstructure to optimize the volume effect and fast diffusion kinetics for lithium storage

Abstract

Although silicon anodes are highly valued for their excellent specific capacity (4200 mAh g^-1 for Li₂₂Si₅), their poor electrical conductivity and significant volume expansion directly lead to rapid capacity degradation during cycling, severely limiting their widespread commercial applications. To overcome these challenges, we propose an innovative combination of self-assembly technology and subsequent carbonization heat treatment to manufacture a Si@C@MoO₂ spherical superstructure. In this unique structure, the well-organized MoO₂ nanocrystals provide abundant active sites to support the efficient repeated insertion and extraction of Li⁺ ions, while the porous carbon matrix significantly enhances the conductivity and efficiently maintains the overall structural stability of the electrode during cycling. As a result, the Si@C@MoO₂ superstructure exhibits superior rate capability and superior cycling stability in LIBs (1400 mAh g^-1 at 1 A g^-1 after 1000 cycles, attenuation rate of 0.06% per cycle) compared to Si/C/MoO₂ (1100 mAh g^-1), Si@C (110 mAh g^-1) and the pure Si anode (60 mAh g^-1). When coupled with LiCoO₂ to form LIB full cells, the anode maintains a capacity of 450 mAh g^-1 over 100 cycles at 1 A g^-1, with an attenuation rate of 0.7% per cycle. In situ electrochemical impedance spectroscopy, ex situ X-ray diffraction, and ex-situ X-ray photoelectron spectroscopy experiments revealed the underlying reasons for the enhanced kinetics of the Si@C@MoO₂ electrode in lithium storage. This approach paves the way for novel multifunctional silicon-based superstructures with potential use as anode materials in energy storage and conversion applications.