镁硫二次电池电解液

Electrolytes for Rechargeable Magnesium-Sulfur Batteries

镁硫二次电池具有安全性好、成本低、能量密度高等特点,其中电解液是目前制约其发展的关键因素。由于硫电极的亲电子特性,格氏试剂及其衍生物系列的传统镁离子电解液无法适用。本文针对有机镁盐+AlCl_3、MgCl_2+有机铝卤盐、MgCl_2+AlCl_3、Mg(TFSI)_2(双三氟甲烷磺酰亚胺基镁)四类电解质溶液体系进行总结和评述。有机镁盐+AlCl_3电解液的镁硫电池表现出较好的电化学性能,MgCl_2+有机铝卤盐电解液体系与硫电极具有良好的兼容性。而使用Mg(TFSI)_2和MgCl_2+AlCl_3电解液时硫电极的比容量不高,且放电平台低。目前所报道的镁硫电池体系的可逆容量衰减都较大,通过加入电解液添加剂等方法可以改善其放电特性和循环稳定性。本文还总结了电解液中活性阳离子结构、阴离子以及电解液添加剂的作用,并展望了镁硫电池电解液体系的研究趋势。

Rechargeable magnesium-sulfur batteries have advantages of good safety,lowcost,and high theoretical energy density. Currently,electrolyte is the key factor to restrict the development of magnesium-sulfur batteries.Generally,traditional Grignard reagents and magnesium ion electrolytes are nucleophilic and incompatible with sulfur. In this paper,the electrolytes for magnesium-sulfur batteries are divided into four categories,containing organomagnesium ＋ AlCl3,MgCl2＋ organoaluminum halide,MgCl2＋ AlCl3 and magnesium bis（ trifluoromethane sulfonyl） imide（ Mg（TFSI）2）. Among them,the organomagnesium ＋ AlCl3 electrolyte is relatively promising for magnesium-sulfur batteries,and HMDS MgCl ＋ AlCl3/THF electrolyte is used to demonstrate a proof of concept for the first rechargeable Mg/S battery. The Mg（TFSI）2or MgCl2＋ AlCl3 based electrolyte for magnesium-sulfur batteries do not contain organic metal salts,and the synthesis methods are simple. However,the batteries using these two kinds of electrolytes exhibit lowspecific capacity and discharge voltage. As for MgCl2＋organoaluminum halide electrolyte,the compatibility with the sulfur electrode has been proved,while the specific capacity,the discharge voltage and other electrochemical properties have not been reported. It is generally believed that the electrolytes for magnesium-sulfur batteries contain monomer Mg,dimeric Mg,trimeric Mg species and other Mg complexes at the same time,and there is a thermodynamically equilibrium among them regulating electrolyte ion conductivity,diffusion coefficient and so on. The effect of anions on the electrolyte ismainly reflected in the anodic stability of electrolytes and the reversibility of Mg deposition-dissolution.Electrolyte additives in the magnesium-sulfur battery electrolyte make a contribution to reduce dissolution of sulfur species and the reoxidation kinetic barrier of low-order Mg PS（ PS is polysulfides）,restrain shuttle effect,and improve the electrolyte conductivity. At last,the research trends of electrolyte for magnesium sulfur batteries are proposed.