Electrolyte additive, electrolyte and application in magnesium metal secondary battery

The invention belongs to the technical field of batteries, and particularly relates to a functional electrolyte additive containing inorganic chloride, an electrolyte and application of the functional electrolyte additive in a magnesium metal secondary battery. The electrolyte additive is one or more of inorganic chlorides AClx shown in the specification, A is an element in IIIA, IVA or VA main groups, and the value of x is between 2 and 4. According to the invention, an in-situ chemical reaction between one or more specific inorganic metal chlorides in the electrolyte and magnesium metal is utilized to form a compact and stable protective solid electrolyte interface film (SEI film) on the surface of the magnesium metal negative electrode, so that further reaction between an additive, magnesium salt and the magnesium metal negative electrode is slowed down; and the interface compatibility between the electrolyte and the magnesium metal negative electrode is improved, so that the cycle performance of the magnesium metal secondary battery is greatly improved.