Li and Li-Al negative electrode characteristics for the lithium secondary battery with a nonflammable SOCl2, Li added, LiCl saturated AlCl3-EMIC molten salt electrolyte

An AlCl3-1-ethyl-3-methylimidazolium chloride (EMIC) melt has a wide electrochemical window, and it is nonflammable with no ignition. We have developed the rocking chair type lithium secondary battery with an AlCl3-EMIC melt containing excess LiCl with a saturated solubility as the nonflammable electrolyte. In this paper, when LiCl was added in the acidic melt (AlCl3 >50 mol %), the solubility of the LiCl and the changes in the physical properties were measured. Moreover, SOCl2 or Li metal was treated to completely remove any small amounts of Al2Cl7-, which was the ionic species for deposited Al, that remained in the melt. As a result, it was confirmed that Al2Cl7- was completely removed based on a cyclic voltammogram (C.V.) using a W electrode. The reversible deposition and dissolution behavior of lithium was indicated from the C.V. for a Li electrode in the SOCl2 containing melt, and it was found that a Li metal would perform as the negative electrode active material.