Rechargeable Alkali Metal Battery Containing a Sodium Salt, Lithium Salt, or Potassium Salt Composite Cathode and Manufacturing Method

Provided is a cathode active material for a rechargeable alkali metal battery, wherein the cathode active material comprises a sodium salt composite comprising a mixture or composite of Fe and at least a sodium salt selected from NaA, wherein x is from 1 to 3, and the anion A is selected from F, Cl, Br, I, PO, SO, CO, SiO, NO, BO, or a combination thereof, wherein a molar ratio of Fe-to-sodium salt is from 1/9 to 9/1. Also provided is a rechargeable alkali metal battery comprising this cathode active material, which is a sodium battery (sodium-ion or sodium metal battery), a lithium battery (lithium-ion or lithium metal battery), or a potassium battery (potassium-ion or potassium metal battery).