Seasonal energy storage technologies based on rechargeable batteries

1. A rechargeable battery, comprising:

a cathode comprising Ni y Fe 1-y and Ni y Fe 1-y X 2 , where 0≤y≤1;

an anode comprising Al and MX deposited onto an aluminum current collector;

a porous separator positioned between the cathode and the anode; and

an electrolyte comprising MAlX 4 , the porous separator impregnated with the electrolyte such that pores of the porous separator are filled with the electrolyte; and

greater than 0 mol % and up to 10 mol % sulfur relative to moles of Ni y Fe 1-y in the cathode, wherein after 2-5 cycles, the sulfur is present as oxidized sulfur species,

wherein M is Na, Li, K, or a combination thereof, and X is CI, Br, I, or a combination thereof,

wherein the anode comprises 50 mol % to 130 mol % MX relative to moles of Ni y Fe 1-y in the cathode, and

wherein the electrolyte is a molten salt electrolyte that is a solid at temperatures less than 50° C.

2. The rechargeable battery of claim 1 , wherein the electrolyte comprises Na a1 Li a2 K a3 AlCl b1 Br b2 I b3 , where:

a1+a2+a3=1, where 0≤a1≤1, 0≤a2≤1, and 0≤a3≤1; and

b1+b2+b3=4, where 0≤b1≤4, 0≤b2≤4, and 0≤b3≤4.

3. The rechargeable battery of claim 1 , wherein:

(i) the electrolyte comprises NaAlCl 4 ; or

(ii) the cathode comprises Ni; or

(iii) both (i) and (ii).

4. The rechargeable battery of claim 1 , wherein the cathode comprises porous nickel granules having an average size of 0.5 mm to 2 mm.

5. The rechargeable battery of claim 1 , further comprising a container containing the cathode, the anode, the porous separator, and the electrolyte, the container comprising:

an upper portion;

a lower portion; and

a compressible gasket between the upper portion and the lower portion.

6. The rechargeable battery of claim 1 , wherein:

(i) the electrolyte comprises NaAlCl 4 ; or

(ii) the cathode comprises NiCl 2 and Ni; or

(iii) the anode comprises Al and NaCl; or

(iv) any combination of (i), (ii), and (iii).

7. A method, comprising:

storing energy in a rechargeable battery by

providing a rechargeable battery comprising a cathode comprising Ni y Fe 1-y and Ni y Fe 1-y X 2 , where 0≤y≤1, an anode comprising Al and MX deposited onto an aluminum current collector, a porous separator positioned between the cathode and the anode, an electrolyte comprising MAlX 4 , the porous separator impregnated with the electrolyte, and greater than 0 mol % and up to 10 mol % sulfur relative to moles of Ni y Fe 1-y in the cathode, wherein after 2-5 cycles, the sulfur is present as oxidized sulfur species, wherein M is Na, Li, K, or a combination thereof, and X is Cl, Br, I, or a combination thereof, wherein the anode comprises 50 mol % to 130 mol % MX relative to moles of Ni y Fe 1-y in the cathode, and wherein the electrolyte is a molten salt electrolyte that is a solid at temperatures less than 50° C.;

heating the electrolyte to a temperature T 1 , wherein the temperature T 1 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 T 1 ; and

allowing the electrolyte to cool to a temperature T 2 , wherein the temperature T 2 is below the melting point of the electrolyte, thereby solidifying the electrolyte and storing energy in the temperature-activated rechargeable battery.

8. The method of claim 7 , wherein charging the rechargeable battery comprises:

supplying a current to the rechargeable battery, wherein the current is sufficient to create an oxidation-reduction reaction in the electrolyte; and

maintaining the current until the oxidation-reduction reaction reaches a desired cut-off voltage.

9. The method of claim 8 , wherein the current is from 1 mA to 5 mA.

10. The method of claim 7 , further comprising:

releasing stored energy from the rechargeable battery by

heating the electrolyte to a temperature T 3 , wherein the temperature T 3 is above a melting point of the electrolyte, thereby melting the electrolyte, and

discharging the rechargeable battery while maintaining the temperature of the electrolyte at or greater than the temperature T 3 , thereby releasing some or all of the stored energy from the temperature-activated rechargeable battery.

11. The method of claim 7 , wherein:

the electrolyte comprises NiAlCl 4 ;

the temperature T 1 is greater than 160° C.; and

the temperature T 2 is less than 150° C.

12. The method of claim 7 , wherein the temperature T 2 is ambient temperature.

13. The method of claim 7 , wherein the rechargeable battery, when maintained at or below the temperature T 2 , has:

(i) a capacity retention of at least 99% of an initial charged capacity after two weeks; or

(ii) a capacity retention of at least 95% of an initial charged capacity after four weeks; or

(iii) both (i) and (ii).

14. 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 Ni y Fe 1-y where 0≤y≤1;

combining the granules with molten MAlX 4 , wherein M is Na, Li, K, or a combination thereof, and X is CI, Br, I, or a combination thereof to provide a Ni y Fe 1-y /MAlX 4 mixture;

placing a porous separator on an upper surface of the Ni y Fe 1-y /MAlX 4 mixture;

placing additional MAlX 4 combined with greater than 0 mol % to 10 mol % sulfur, relative to moles of the Ni y Fe 1-y , on the porous separator;

melting the additional MAlX 4 , thereby impregnating the porous separator with the additional MAlX 4 such that pores of the porous separator are filled with the MAlX 4 ;

placing an aluminum current collector on an upper surface of the porous separator while the MAlX 4 is molten;

cooling the MAlX 4 to solidify the MAlX 4 , wherein the MAlX 4 is a molten salt electrolyte that is a solid at temperatures less than 50° C.;

activating the cathode by

heating the MAlX 4 to a temperature above a melting point of the MAlX 4 , thereby melting the MAlX 4 , and

cycling the rechargeable battery while maintaining the temperature of the electrolyte above the melting point of the MAlX 4 for 2-40 cycles, wherein after 2-5 cycles, the sulfur is present as oxidized sulfur species; and

at least partially charging the rechargeable battery, whereby the cathode further comprises Ni y Fe 1-y X 2 , the anode further comprises Al and MX deposited onto the aluminum current collector, where the anode comprises 50 mol % to 130 mol % MX relative to moles of Ni y Fe 1-y in the cathode.

15. The method of claim 14 , wherein the granules are combined with molten MAlX 4 in a container, the method further comprising:

(i) evacuating gas from the container containing granules and molten MAlX 4 ; or

(ii) applying pressure to the porous separator to remove gas from pores of the porous separator while impregnating the porous separator with the additional MAlX 4 ; or

(iii) both (i) and (ii).

16. The method of claim 14 , further comprising, prior to placing the porous separator on the upper surface of the Ni y Fe 1-y /MAlX 4 mixture:

cooling the Ni y Fe 1-y /MAlX 4 mixture to solidify the molten MAlX 4 ; and

comminuting the Ni y Fe 1-y /MAlX 4 mixture to provide grounds having an average size of 0.1 to 2 mm.