Synthesis and electrochemical performance of lithium silicide based alloy anodes for Li–ion oxygen batteries

Abstract

Li–air batteries receive significant attention due to their theoretical energy density values. However, the large implementation of the Li–air batteries is hindered by the use of metallic Li anode which leads to the low coulombic efficiency and safety problems. Therefore, finding alternatives to the metallic Li anodes is extremely important to realize the high energy density Li–air batteries. In this study, Li22Si5 and Li13Si4 alloys are synthesized by the mechanical alloying and their electrochemical performances as the anode material are observed in 1 M LiTFSI-DME:EC (95:5 vol%) electrolyte. XRD analyses following the discharge/charge measurements show that the formation of the charge products (LixSiy phases) is directly affected by the initial alloy anode stoichiometry. The approximate specific energy density of the assembled Li–ion oxygen batteries, which is alternative description of the Li–air batteries when the metallic Li anode is replaced by the alloy anode, is 1840 W h kg−1 under fixed capacity condition (800 mA h g−1) at 100 mA g−1 current density. The working voltage of the cell is at around 2.3 V. This study indicates that the lithium silicide alloy anodes, as the alternatives to the metallic Li anodes, are highly promising to develop Li-ion oxygen batteries with higher coulombic efficiency and lower polarization values.