Coral-shaped AlSi anode materials for Li-ion batteries enabled by THF-based electrolyte

Abstract

This research aims to implement a strategy of using a controlled acidic etching on AlSi alloy particles to partially remove Al and preserve a porous Si framework as anode materials. The etched AlSi materials with different Al/Si weight ratios have been investigated in lithium-ion batteries. Microstructural analysis shows the evolution of the AlSi material during selective wet etching, highlighting the preservation of coral-shaped Si nanostructures with an Al-rich core. Lower Al/Si ratios result in increased surface area and pore volume, which is favorable for improving lithium-ion diffusion and accommodating volume expansion during cycling. Evaluation of electrochemical performance in different electrolytes proves the importance of electrolyte selection for AlSi anodes. The tetrahydrofuran-based (THF-based) electrolyte stabilizes electrochemical reactions, resulting in superior specific capacity, cycle life, and Coulombic efficiency compared to the carbonate-based electrolyte with fluoroethylene carbonate additive. Rate performance analysis shows excellent high-rate capability with stable capacity retention at 3C, particularly in Al53Si47 and Al10Si90 materials. Electrochemical impedance spectroscopy measurements emphasize the critical role of porous structure and electrolytes in sustaining low resistance and enhancing cycle life performance. Selective aluminum etching and the THF-based electrolyte effectively mitigate the breakdown and subsequent reformation of the solid electrolyte interphase, resulting in superior efficiency and extended lifespan.