A LiA1Cl₄·3SO₂-NaAlCl₄·2SO₂ binary inorganic electrolyte with improved electrochemical performance for Li-metal batteries

A LiAlCl₄·3SO₂-NaAlCl₄·2SO₂ binary inorganic electrolyte was prepared by using NaAlCl₄·2SO₂ as the functional additive and mixing with LiAlCl₄·3SO₂. The obtained LiAlCl₄·3SO₂-NaAlCl₄·2SO₂ not only has good non-flammability but also exhibits improved electrochemical performance for Li-metal batteries. With the addition of NaAlCl₄·2SO₂, the fabricated Li/Cu cells using mixed inorganic electrolyte display higher average coulombic efficiency and more excellent cycling stability. Through scanning electron microscopy (SEM) characterization, it is demonstrated that the surficial morphology of Li-deposited layer is smoother in LiAlCl₄·3SO₂-NaAlCl₄·2SO₂ binary electrolyte system than pure LiAlCl₄·3SO₂. Furthermore, the fabricated Li/graphite cells using LiAlCl₄·3SO₂-NaAlCl₄·2SO₂ binary electrolyte also show higher specific capacity and better cycling stability than using pure LiAlCl₄·3SO₂ electrolyte as well as the conventional organic electrolyte (1 M LiPF₆ in ethylene carbonate/dimethyl carbonate mixed solvent with 1:1 in volume). Consequently, LiAlCl₄·3SO₂-NaAlCl₄·2SO₂ is proposed to have great potential for the safe and high-performance Li-metal batteries. [Figure not available: see fulltext.].