Method of manufacturing a thin film composite solid electrolyte
A method for manufacturing an improved thin film composite solid electrolyte is provided. The method includes spray coating an aqueous suspension of ceramic particles onto a substrate to form a ceramic thin film. The film is sintered to form a porous ceramic structure having an interconnected necked morphology that defines cavities. The cavities are backfilled with an polymer electrolyte, for example a crosslinkable poly(ethylene oxide) (PEO)-based polymer electrolyte. The resulting thin film composite solid electrolyte is highly ionically conductive and mechanically robust with good manufacturability, particularly suitable for, but not limited to lithium metal batteries. The present method represents a departure from conventional mixing-then-casting methods and instead includes the fabrication of a solid electrolyte having a high ceramic volume fraction, high ionic conductivity, low thickness, and good chemical stability with metallic lithium.
1. A method for manufacturing a thin film composite solid electrolyte, said method comprising:
spray coating an aqueous suspension of ceramic particles onto a substrate to form a ceramic thin film while the substrate is heated to a temperature of 70° C. to 150° C., the aqueous suspension including ceramic particles in an amount of under 15 wt. %, the ceramic particles having a mean particle diameter of 0.1 μm to 10 μm;
sintering the ceramic thin film under argon gas at a temperature of 750° C. to 1250° C. for 1 to 5 hours to form a ceramic structure, the ceramic structure having an interconnected necked morphology that defines cavities;
preparing a polymer electrolyte by combining an amine-functional compound and an epoxy-functional compound with a weight ratio of 9:10, wherein the amine-functional compound includes O,O′-Bis(2-aminopropyl) polypropylene glycol-block-polyethylene glycol-block-polypropylene glycol, and wherein the epoxy-functional compound includes poly(ethylene glycol) diglycidyl ether;
dissolving a lithium salt in the polymer electrolyte; and
filling the cavities of the ceramic structure with the polymer electrolyte in a reduced atmosphere by capillary action for 2 to 6 hours and thereafter curing the polymer electrolyte at 70° C. to 130° C. for 4 to 48 hours to form a thin film composite electrolyte having a thickness of less than 50 μm and a ceramic weight fraction of more than 60 wt. %.
2. The method of claim 1 , wherein the ceramic particles are ion-conducting.
3. The method of claim 1 , wherein the polymer electrolyte has lithium stability.
4. The method of claim 1 , wherein the polymer electrolyte is cross-linkable.
5. The method of claim 1 , wherein the step of spray coating the aqueous suspension of ceramic particles onto the substrate is performed using an automatic spraycoater.
6. The method of claim 5 , wherein the step of spray coating comprises a spray nozzle of the automatic spraycoater moving over a preprogramed area of the substrate while the ceramic particles are sprayed from the spray nozzle.
7. The method of claim 6 , wherein the spraycoater makes multiple passes over the preprogramed area over the substrate.