Low temperature secondary cell with sodium intercalation electrode

A method for providing electrical potential from a molten sodium secondary cell, the method comprising:

• providing a molten sodium secondary cell, comprising:
• a sodium metal negative electrode, which electrochemically oxidizes to release sodium ions during discharge and electrochemically reduces sodium ions to sodium metal during recharging;
• a positive electrode compartment comprising a positive electrode disposed in a molten positive electrolyte comprising NaFSA (sodium bis(fluorosulonyl)amide), wherein the positive electrode comprises a sodium intercalation electrode;
• and
• a sodium ion conductive electrolyte membrane that separates the sodium metal negative electrode from the molten positive electrolyte;
• and
• heating the sodium metal negative electrode to a temperature between about 100° C. and about 150° C. so that the sodium metal negative electrode is molten and in contact with the sodium ion conductive electrolyte membrane and so that the sodium metal negative electrode oxidizes to release the sodium ions and allows the cell to discharge electricity.

A molten sodium secondary cell, comprising:

• a negative electrode compartment comprising a sodium metal negative electrode, which electrochemically oxidizes to release sodium ions during discharge and electrochemically reduces sodium ions to sodium metal during recharging;
• a positive electrode compartment comprising a positive electrode disposed in a molten positive electrolyte comprising NaFSA (sodium bis(fluorosulonyl)amide), wherein the positive electrode comprises a sodium intercalation electrode selected from NaxMnO2, NaxCrO2, NaxNiO and NaxFey(PO4)z, wherein x is between 0 and 4, y is between 0 and 4, and z is between 0 and 4;
• a sodium ion conductive electrolyte membrane comprising a NaSICON-type material that separates the sodium metal negative electrode from the molten positive electrolyte;
• and
• a heat management system to control the operating temperature of the cell,
• wherein the sodium metal negative electrode is molten and in contact with the conductive electrolyte membrane as the cell operates, and wherein the cell functions at an operating temperature between about 110° C. and about 130° C.