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

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 mA g−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.