Thin-film reference electrodes, electrochemical devices including thin-film reference electrodes, and methods of making thin-film reference electrodes

A method of making a reference electrode assembly for an electrochemical cell, the method comprising:

• providing a subassembly comprising a separator layer and a current collector layer coupled to the separator layer, the separator layer being porous and electrically insulating, the current collector layer being electrically conductive;
• providing an electrode ink comprising an electroactive material, a binder, and a solvent;
• creating a reference electrode precursor by spin-coating an electroactive precursor layer directly to a surface of the current collector layer of the subassembly, the electroactive precursor layer covering an area of greater than or equal to about 70% of the entire superficial surface of the surface of the current collector layer, the electroactive precursor layer comprising the electrode ink;
• and
• creating the reference electrode assembly by drying the electroactive precursor layer to remove at least a portion of the solvent, thereby forming an electroactive layer, the electroactive layer being solid and porous, the electroactive layer defining a thickness of greater than or equal to about 0.2 micrometers to less than or equal to about 1 micrometers and a first porosity of greater than or equal to about 40% to less than or equal to about 60%.