Seasonal energy storage technologies based on rechargeable batteries

A method, comprising:

• storing energy in a rechargeable battery by
• providing a rechargeable battery comprising a cathode comprising NiyFe1-y where 0≤y≤1, an anode comprising a current collector, a porous separator positioned between the cathode and the anode, and an electrolyte comprising MAlX4, wherein M is Na, Li, K, or a combination thereof, and X is Cl, Br, I, or a combination thereof, the porous separator impregnated with the electrolyte, wherein the electrolyte is a solid at temperatures less than 50° C.;
• heating the electrolyte to a temperature T1, wherein the temperature T1 is above a melting point of the electrolyte, thereby melting the electrolyte;
• charging the temperature-activated rechargeable battery while maintaining the temperature of the electrolyte at or greater than the temperature T1;
• and
• allowing the electrolyte to cool to a temperature T2, wherein the temperature T2 is below the melting point of the electrolyte, thereby solidifying the electrolyte and storing energy in the temperature-activated rechargeable battery.

A method of making a rechargeable battery, the method comprising:

• sintering cathode material particles to remove surface oxidation and produce porous granules, the granules comprising NiyFe1-y where 0≤y≤1;
• combining the granules with molten MAlX4, wherein M is Na, Li, K, or a combination thereof, and X is Cl, Br, I, or a combination thereof to provide a NiyFe1-y/MAlX4 mixture;
• placing a porous separator on an upper surface of the NiyFe1-y/MAlX4 mixture;
• placing additional MAlX4 combined with 0 mol % to 10 mol % sulfur, relative to moles of the NiyFe1-y, on the porous separator;
• melting the additional MAlX4, thereby impregnating the porous separator with the additional MAlX4;
• placing a current collector on an upper surface of the porous separator while the MAlX4 is molten;
• and
• cooling the MAlX4 to solidify the MAlX4.