Alkali metal-sulfur batteries having high volumetric and gravimetric energy densities

1. An alkali metal-sulfur battery, comprising:

(a) an anode having an anode active material coated on or in physical contact with an anode current collector wherein said anode active material is in ionic contact with a first electrolyte;

(b) a cathode having (i) a cathode active material slurry suspension comprising a cathode active material and a conductive additive dispersed in a second liquid or gel electrolyte, the same as or different than said first liquid or gel electrolyte, and (ii) a conductive porous structure acting as a 3D cathode current collector selected from conductive polymer-coated fiber foam wherein said conductive porous structure has at least 70% by volume of pores having pore size from 500 nm to 20 μm and wherein said cathode active material slurry suspension is disposed in pores of said conductive porous structure, wherein said cathode active material is selected from sulfur-graphene composite wherein said cathode active material has a thickness or diameter smaller than 7 nm; and

(c) a separator disposed between said anode and said cathode;

wherein a cathode thickness-to-cathode current collector thickness ratio is from 0.8/1 to 1/0.8, and/or said cathode active material constitutes an electrode active material loading greater than 15 mg/cm 2 , and said 3D cathode current collector has a thickness no less than 200 μm.

2. The alkali metal-sulfur battery of claim 1 , wherein said anode current collector contains a porous foamed structure.

3. The alkali metal-sulfur battery of claim 1 , wherein said cathode active material is supported by a functional material or nano-structured material selected from the group consisting of:

(a) a nano-structured or porous disordered carbon material selected from particles of a soft carbon, hard carbon, polymeric carbon or carbonized resin, meso-phase carbon, coke, carbonized pitch, carbon black, activated carbon, nano-cellular carbon foam or partially graphitized carbon;

(b) a nano graphene platelet selected from a single-layer graphene sheet or multi-layer graphene platelet;

(c) a carbon nanotube selected from a single-walled carbon nanotube or multi-walled carbon nanotube;

(d) a carbon nano-fiber, nano-wire, metal oxide nano-wire or fiber, conductive polymer nano-fiber, or a combination thereof;

(e) a carbonyl-containing organic or polymeric molecule;

(f) a functional material containing a carbonyl, carboxylic, or amine group to reversibly capture sulfur;

and combinations thereof.

4. The alkali metal-sulfur battery of claim 1 , wherein said anode active material contains an alkali ion source selected from an alkali metal, an alkali metal alloy, a mixture of alkali metal or alkali metal alloy with an alkali intercalation compound, an alkali element-containing compound, or a combination thereof.

5. The alkali metal-sulfur battery of claim 1 , wherein said first electrolyte is a gel electrolyte or solid-state electrolyte.

6. The alkali metal-sulfur battery of claim 1 , wherein said 3D porous cathode current collector contains a conductive foam structure having a thickness no less than 200 μm, having at least 85% by volume of pores, and/or the cathode active material has a mass loading no less than 20 mg/cm 2 .

7. The alkali metal-sulfur battery of claim 2 , wherein said 3D porous cathode current collector contains a conductive foam structure having a thickness no less than 300 μm, at least 90% by volume of pores, and/or the cathode active material has a mass loading no less than 25 mg/cm 2 .

8. The alkali metal-sulfur battery of claim 1 , wherein said 3D porous cathode current collector contains a conductive foam structure having a thickness no less than 400 μm, having at least 95% by volume of pores, and/or the cathode active material has a mass loading no less than 30 mg/cm 2 .

9. An alkali metal-sulfur battery, comprising:

(A) an anode having an anode active material coated on or in physical contact with an anode current collector wherein said anode active material is in ionic contact with a first electrolyte;

(B) a cathode having (i) a cathode active material slurry suspension comprising a cathode active material dispersed in a second liquid or gel electrolyte, the same as or different than said first liquid or gel electrolyte, and (ii) a conductive porous structure acting as a 3D cathode current collector selected from conductive polymer-coated fiber foam wherein said conductive porous structure has at least 70% by volume of pores and wherein said cathode active material slurry suspension is disposed in pores of said conductive porous structure and does not contain a conductive additive, wherein said cathode active material is selected from sulfur, lithium polysulfide, sodium polysulfide, sulfur-polymer composite, organo-sulfides, sulfur-carbon composite, sulfur-graphene composite, or a combination thereof, wherein there are no dry pockets in said cathode, wherein said cathode active material has a thickness or diameter smaller than 7 nm; and

(C) a separator disposed between said anode and said cathode;

wherein a cathode thickness-to-cathode current collector thickness ratio is from 0.8/1 to 1/0.8, and/or said cathode active material constitutes an electrode active material loading greater than 15 mg/cm 2 , and said 3D cathode current collector has a thickness no less than 200 μm.

10. An alkali metal-sulfur battery, comprising:

A) an anode having an anode active material coated on or in physical contact with an anode current collector wherein said anode active material is in ionic contact with a first electrolyte;

B) a cathode having (i) a cathode active material slurry suspension comprising a cathode active material and an optional conductive additive dispersed in a second liquid or gel electrolyte, the second liquid or gel electrolyte different than said first liquid or gel electrolyte, and (ii) a conductive porous structure acting as a 3D cathode current collector selected conductive polymer-coated fiber foam, wherein said conductive porous structure has at least 70% by volume of pores and wherein said cathode active material slurry suspension is disposed in pores of said conductive porous structure, wherein said cathode active material is selected from the group consisting of sulfur, lithium polysulfide, sodium polysulfide, sulfur-polymer composite, organo-sulfides, sulfur-carbon composite, sulfur-graphene composite, and combinations thereof wherein said cathode active material has a thickness or diameter smaller than 7 nm; and

C) a separator disposed between said anode and said cathode;

wherein a cathode thickness-to-cathode current collector thickness ratio is from 0.8/1 to 1/0.8, and/or said cathode active material constitutes an electrode active material loading greater than 15 mg/cm 2 , and said 3D cathode current collector has a thickness no less than 200 μm.