Synergistic engineering of micron-sized porous silicon anodes via Ge doping and liquid metal alloy modification for high-energy-density lithium-ion batteries†

Abstract

In contrast to nanosilicon, micron-sized silicon anodes have gained widespread attention due to their high energy density, favorable processability, and reduced side reactions. However, these anodes are plagued by several significant challenges. They undergo substantial volume changes, and suffer from sluggish lithium-ion transport kinetics and the loss of electrical contact. In this study, micron-sized porous silicon (pSi) obtained through acid etching of an Al₆₀Si₄₀ alloy was utilized as the starting material. A novel approach combining high-energy ball milling and wet chemistry methods was adopted to dope Ge atoms into pSi and modify it with a liquid GaInSn metal (LM) alloy (designated as pSi/Ge@LM). The incorporation of Ge heteroatoms and LM offers multiple benefits. Firstly, it enhances the tap density of pSi. Secondly, it effectively boosts the electron transport performance of the material. Moreover, the excellent metallic properties and liquid fluidity of LM endow it with a unique “self-healing” function. Both the half-cells and full-cells assembled with the pSi/Ge@LM electrode demonstrate outstanding electrochemical performance. Specifically, in the half-cells, when cycled at a current density of 1 A g⁻¹ for 400 times, the pSi/Ge@LM electrode retains a remarkably high specific capacity of 1011 mA h g⁻¹. Even at a high current density of 3 A g⁻¹, it still delivers a reversible capacity of over 900 mA h g⁻¹. It is anticipated that this research will offer novel insights and valuable guidance for the development of high-energy-density micron-sized silicon anodes.