Nitrogen—sulfur—carbon nanocomposites and their application as cathode materials in lithium—sulfur batteries
The invention is directed in a first aspect to electron-conducting porous compositions comprising an organic polymer matrix doped with nitrogen atoms and having elemental sulfur dispersed therein, particularly such compositions having an ordered framework structure. The invention is also directed to composites of such S/N-doped electron-conducting porous aromatic framework (PAF) compositions, or composites of an S/N-doped mesoporous carbon composition, which includes the S/N-doped composition in admixture with a binder, and optionally, conductive carbon. The invention is further directed to cathodes for a lithium-sulfur battery in which such composites are incorporated.
1. A composite useful as a cathode for a lithium-sulfur battery, the composite comprising:
(i) an electron-conducting porous composition comprising an organic polymer matrix having an ordered framework structure in which nitrogen atoms are interconnected by phenylene linkers, wherein said ordered framework structure contains micropores in which sulfur is incorporated;
(ii) a binder; and
(iii) conductive carbon in an amount of 10-30% by weight of the composite, wherein said sulfur is incorporated in the micropores of said electron-conducting porous composition in an amount of at least 20% and up to 50% by weight of the electron-conducting porous composition.
2. The composite of claim 1 , wherein the ordered framework structure is comprised of interconnected triphenylamine units.
3. The composite of claim 1 , wherein said binder comprises a fluoropolymer.
4. The composite of claim 3 , wherein the fluoropolymer is comprised of polyvinylidene difluoride.
5. The composite of claim 1 , wherein said conductive carbon comprises carbon black.
6. The composite of claim 1 , wherein the ordered framework structure possesses a surface area of at least 300 m 2 /g.
7. The composite of claim 1 , wherein the ordered framework structure possesses a surface area of at least 300 m 2 /g and up to 2500 m 2 /g.
8. The composite of claim 1 , wherein said sulfur is incorporated in the micropores of said electron-conducting porous composition in an amount of at least 30% and up to 50% by weight of the electron-conducting porous composition.