Engineering a Low-Strain Si@TiSi2@NC Composite for High-Performance Lithium-Ion Batteries

The huge volume expansion/contraction of silicon (Si) during the lithium (Li) insertion/extraction process, which can lead to cracking and pulverization, poses a substantial impediment to its practical implementation in lithium-ion batteries (LIBs). The development of low-strain Si-based composite materials is imperative to address the challenges associated with Si anodes. In this study, we have engineered a TiSi₂ interface on the surface of Si particles via a high-temperature calcination process, followed by the introduction of an outermost carbon (C) shell, leading to the construction of a low-strain and highly stable Si@TiSi₂@NC composite. The robust TiSi₂ interface not only enhances electrical and ionic transport but also, more critically, significantly mitigates particle cracking by restraining the stress/strain induced by volumetric variations, thus alleviating pulverization during the lithiation/delithiation process. As a result, the as-fabricated Si@TiSi₂@NC electrode exhibits a high initial reversible capacity (2172.7 mAh g^-1 at 0.2 A g^-1), superior rate performance (1198.4 mAh g^-1 at 2.0 A g^-1), and excellent long-term cycling stability (847.0 mAh g^-1 after 1000 cycles at 2.0 A g^-1). Upon pairing with LiNi_0.6Co_0.2Mn_0.2O₂ (NCM622), the assembled Si@TiSi₂@NC||NCM622 pouch-type full cell exhibits exceptional cycling stability, retaining 90.1% of its capacity after 160 cycles at 0.5 C.