TECHNOLOGY FOCUS - ELECTRICAL POWER AND ENERGY - Preferred Composition: Composite cathode may further comprise:(1) one or more conductive fillers selected from conductive carbons, graphites, active carbon fibers, metal flakes, powders and fibers, electroconductive polymers and electroconductive metal chalcogenides; or(2) binder;(3) electrolyte.Electrolyte comprises one or more materials selected from liquid electrolytes, gel-polymer electrolytes and solid polymer electrolytes.Preferred Method: Solid composite cathode is preferably formed by dispersing or suspending, in liquid medium, an electroactive sulfur-containing material as claimed above, and non-activated carbon nano-fibers; casting the mixture onto a substrate or placing the mixture into a mold; and removing some or all of liquid medium to form a solid or gel-like composite cathode in the shape or form as desired.    TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Composition: Composite cathode preferably comprises non-electroactive metal oxide selected from silica, alumina, silicate and titanium dioxide. Anode comprises one or more materials selected from lithium, lithium-aluminum alloys, lithium-tin alloys, lithium-intercalated carbons and lithium-intercalated graphites. Electroactive S-containing material may comprise elemental S.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Electrolyte: Electrolyte comprises one or more electrolyte solvents selected from N-methyl acetamide, acetonitrile, carbonates, sulfolanes, sulfones, N-alkyl-pyrrolidones, dioxolanes and siloxanes, and one or more ionic electrolyte salts.    TECHNOLOGY FOCUS - POLYMERS - Preferred Polymer: Electroactive sulfur-containing material preferably comprises carbon-sulfur polymer. Polysulfide (I) is preferably covalently bonded by one or both terminal S atoms on a side group to the polymer chain or carbon-sulfur polymer, or it is incorporated by covalent bonds to both of its terminal S atoms into polymer chain of carbon-sulfur polymer. The latter preferably comprises more than 75 wt.% of S. Electrolyte preferably comprises one or more polymers selected from polyethers, polyethylene oxides, polypropylene oxides, polyimides, polyphosphazenes, polyacrylonitriles, polysiloxanes, their derivatives, copolymers or blends; and one or more ionic electrolyte salts. EXAMPLE - Composite cathode containing 60 wt.% of elemental S, 10 wt.% of conductive carbon pigment, 20 wt.% of pre-washed PYROGRAF-III (RTM) carbon nano-fibers, 5 wt.% polyethylene oxide (A) and 5 wt.% of polytetrafluoro-ethylene (B) was prepared by first making 3 wt.% solution of (A) (molecular weight 600,00) in water/isopropanol (1:4 by wt.) by adding 5.0 g of (A) to solution of 32.3 g of deionized water and 129.3 g of isopropanol and mixing for 12 hours, dry grinding of sulfur (60.0 g) and conductive carbon pigment (10.0 g) 4 times for 5 seconds, dry grinding separately carbon nano-fibers for 6 seconds, to provide total of 20 g of ground carbon nano-fibers, and then adding sulfur/pigment mixture to solution of 166.7 g of 3% (A), 188 g of isopropanol and 47 g of water, mixing for 5 minutes, additional mixing for 7 minutes in sonicator, and mechanical stirring during dropwise addition of 8.3 g of emulsion of (B) (60% solids), for 5 minutes, followed by manual addition of carbon nano-fibers (20.0 g) and mixing of formed paste with hand mixer for 7 minutes. The paste was manually spread on aluminum EXMET (RTM) using Rondo roller unit. The loading of S in the paste cathode coating was 2.5-3.1 mg/cm2, with average cathode thickness 204 mum. AA cells were assembled by combining 100 micron lithium foil, 25 micron thick CELGARD 2500 (RTM) separator, and the paste coated cathode into a roll and inserting this roll into AA cell casing, followed by filling with electrolyte solution of 1.0 M LiN(SO2CF3)2 in 5/2/2/1 blend by volume of 1,3-dioxolane/ diglyme/ dimethoxyethane/ sulfolane. All cells were tested with charge and discharge at 100 mA for the first cycle followed by discharge under GSM conditions (charge density average 165 mA) and by charge at 75 mA with a constant time of 14 hours. The average capacity for the 13 cells was 859 mAh after the 1st cycle, 685 mAh after the 5th cycle, and 592 mAh after the 10th cycle. The average specific capacity for 13 cells was 1193 mAh/g after the 1st cycle, 952 mAh/g after the 5th cycle, and 824 mAh/g after the 10th cycle.