Protective coatings for lithium metal electrodes and methods of forming the same

An electrochemical cell that cycles lithium ions, wherein the electrochemical cell comprises:

• a lithium metal electrode;
• a separator;
• and
• a protective layer disposed between the electrode and the separator, the protective layer comprising a polymerized matrix having one or more lithium salts dispersed therewithin, the protective layer comprising greater than or equal to about 20 wt. % to less than or equal to about 80 wt. % of the polymerized matrix and greater than or equal to about 40 wt. % to less than or equal to about 60 wt. % of the one or more lithium salts, the polymerized matrix comprising a polymerized cyclic ether, the one or more salts comprising a first salt selected from the group consisting of:
• potassium nitrate (KNO3), cesium nitrate (CsNO3), and combinations thereof and a second salt consisting of cesium phosphate (Cs3PO4).

A method for forming an electrode, the electrode comprising a lithium metal electroactive material layer and a protective layer disposed thereon, the method comprising:

• disposing a solution on or adjacent to a surface of the lithium metal electroactive material layer, the solution comprising:
• a salt dissolved in a solvent mixture,
• the salt comprising a first salt selected from the group consisting of:
• potassium nitrate (KNO3), cesium nitrate (CsNO3), and combinations thereof and a second salt consisting of cesium phosphate (Cs3PO4), and
• the solvent mixture comprising a cyclic ether and one or more organic phosphates represented by:
• where R is a methyl group, an ethyl group, or CH2CF3;
• and
• polymerizing the cyclic ether to form a matrix comprising the polymerized cyclic ether, the salt being dispersed throughout the matrix to form the protective layer, the protective layer comprising greater than or equal to about 20 wt. % to less than or equal to about 80 wt. % of the matrix and greater than or equal to about 40 wt. % to less than or equal to about 60 wt. % of the salt.