Constructing cycle-stable Si/TiSi2 composites as anode materials for lithium ion batteries through direct utilization of low-purity Si and Ti-bearing blast furnace slag

Highlights: • Si/TiSi₂ composites were prepared by a facile and low-cost method. • Ti-bearing blast furnace slag and low-purity silicon were used as raw materials. • The TiSi₂ content is easily controlled by adjustment of feed ratio. • Si/TiSi₂ anode materials exhibit enhanced cycle stability in lithium ion battery. -- Abstract: The large volume expansion and poor conductivity leading to the deterioration of electrochemical performance, is a significant challenge for Si-anode materials for practical applications. Previous researches have indicated that introducing a TiSi₂ buffer with high conductivity to form Si/TiSi₂ composites can effectively improve the electrochemical performance of Si anode. However, the facile and low-cost synthesis of Si/TiSi₂ composites remains challenging. In this study, we propose a novel approach to preparing Si/TiSi₂ composites as anode materials for lithium-ion batteries by coupling photovoltaic (PV) silicon waste (simulated using inexpensive low-purity Si (98.8%) in experiments) and metallurgical waste (Ti-bearing blast furnace slag, TBBFS) via a new method combining induction melting and mechanical ball milling. A series of Si/TiSi₂ materials were obtained using different ratios of raw materials and investigated using SEM, TEM, XRD, XPS and electrochemical performance tests. The results show that TiSi₂ not only acts as a buffer for the bulk expansion of Si, but also improves the electrical conductivity; therefore, the Si/TiSi₂ materials exhibit enhanced cycling stability when more TiSi₂ is introduced. The sample prepared using a low-purity Si and TBBFS with a mass ratio of 1:3 delivered a reversible capacity of 530 mAh g⁻¹ after 200 cycles at a charge-discharge current density of 800 mAg⁻¹. This work not only provides a new strategy and technology for introducing TiSi₂ into Si-based anode materials, but also provides a green and sustainable technical route for the high value-added recycling of Ti-bearing blast furnace slag.