A composite containing phosphorus, lithium, iron, sulfur, and carbon as constituent elements wherein lithium sulfide (Li.sub.2S) is present in an amount of 90 mol % or more, and wherein the crystallite size calculated from the half-width of a diffraction peak based on the (111) plane of Li.sub.2S as determined by X-ray powder diffraction measurement is 80 nm or less. The composite exhibits a high capacity (in particular, a high discharge capacity) useful as an electrode active material for a lithium-ion secondary battery (in particular, a cathode active material for a lithium-ion secondary battery), without the need for stepwise pre-cycling treatment.

An object of the present invention is to provide a novel sulfur-based positive electrode active material for a lithium-ion secondary battery which is excellent in cyclability and can largely improve a charging and discharging capacity, a positive electrode comprising the positive electrode active material and a lithium-ion secondary battery made using the positive electrode. The sulfur-based positive electrode active material is obtainable by subjecting a starting material comprising a polymer, sulfur and an organometallic compound dispersed in a form of fine particles to heat-treatment under a non-oxidizing atmosphere, wherein the particles of metallic sulfide resulting from sulfurization of the organometallic compound are dispersed in the heat-treated material, and particle size of the metallic sulfide particles is not less than 10 nm and less than 100 nm.

An object of the present invention is to provide a novel sulfur-based positive electrode active material for a lithium-ion secondary battery which is excellent in cyclability and can largely improve a charging and discharging capacity, a positive electrode comprising the positive electrode active material and a lithium-ion secondary battery made using the positive electrode. The sulfur-based positive electrode active material is obtainable by subjecting a starting material comprising a polymer, sulfur and an organometallic compound dispersed in a form of fine particles to heat-treatment under a non-oxidizing atmosphere, wherein the particles of metallic sulfide resulting from sulfurization of the organometallic compound are dispersed in the heat-treated material, and particle size of the metallic sulfide particles is not less than 10 nm and less than 100 nm.

Systems and methods of synthesizing nanoparticles on substrates using rapid, high temperature thermal shock. A method involves depositing micro-sized particles or salt precursors on a substrate, and applying a rapid, high temperature thermal pulse or shock to the micro-sized particles or the salt precursors and the substrate to cause the micro-sized particles or the salt precursors to become nanoparticles on the substrate. A system may include a rotatable member that receives a roll of a substrate sheet having micro-sized particles or salt precursors; a motor that rotates the rotatable member so as to unroll consecutive portions of the substrate sheet from the roll; and a thermal energy source that applies a short, high temperature thermal shock to consecutive portions of the substrate sheet that are unrolled from the roll by rotating the first rotatable member. Some systems and methods produce nanoparticles on existing substrate. The nanoparticles may be metallic, ceramic, inorganic, semiconductor, or compound nanoparticles. The substrate may be a carbon-based substrate, a conducting substrate, or a non-conducting substrate. The high temperature thermal shock process may be enabled by electrical Joule heating, microwave heating, thermal radiative heating, plasma heating, or laser heating.

Provided is a method of producing a sulfur-based active material, the method comprising the steps of: (1) mixing an acrylic resin, sulfur, and an iron compound comprising a divalent or trivalent iron ion to obtain a raw material; and (2) baking the raw material, characterized in that a volume energy density is improved while maintaining a capacity retention rate of the active material that constitutes an electrode of a lithium-ion secondary battery.

Provided is a method of producing a sulfur-based active material, the method comprising the steps of: (1) mixing an acrylic resin, sulfur, and an iron compound comprising a divalent or trivalent iron ion to obtain a raw material; and (2) baking the raw material, characterized in that a volume energy density is improved while maintaining a capacity retention rate of the active material that constitutes an electrode of a lithium-ion secondary battery.

Electrodes are provided comprising a FeS.sub.2 electrocatalytic material, the FeS.sub.2 electrocatalytic material comprising FeS.sub.2 nanostructures in the form of FeS.sub.2 wires, FeS.sub.2 discs, or both, wherein the FeS.sub.2 wires and the FeS.sub.2 discs are hyperthin having a thickness in the range of from about the thickness of a monolayer of FeS.sub.2 molecules to about 20 nm. The FeS.sub.2 nanostructures may be polycrystalline comprising a non-pyrite majority crystalline phase. The FeS.sub.2 nanostructures may be in the form of FeS.sub.2 discs wherein substantially all the FeS.sub.2 discs have at least partially curved edges.

Electrodes are provided comprising a FeS.sub.2 electrocatalytic material, the FeS.sub.2 electrocatalytic material comprising FeS.sub.2 nanostructures in the form of FeS.sub.2 wires, FeS.sub.2 discs, or both, wherein the FeS.sub.2 wires and the FeS.sub.2 discs are hyperthin having a thickness in the range of from about the thickness of a monolayer of FeS.sub.2 molecules to about 20 nm. The FeS.sub.2 nanostructures may be polycrystalline comprising a non-pyrite majority crystalline phase. The FeS.sub.2 nanostructures may be in the form of FeS.sub.2 discs wherein substantially all the FeS.sub.2 discs have at least partially curved edges.

A method of preparing a thermoelectric material comprising an iron-sulfur compound, the method including: 1) weighing, grinding, and mixing an iron salt and a sulfur-containing source to obtain a mixed powder; 2) carrying out a hydrothermal reaction with the mixed powder to obtain a black precipitate; 3) washing the precipitate; 4) drying the precipitate under vacuum to obtain FeS.sub.2 powder; 5) annealing the FeS.sub.2 powder under inert atmosphere to obtain annealed powder, where a heating temperature is from 300 C. to 1000 C., a heating time is from 2 hours to 24 hours, and a flow rate of an inert gas is from 30 mL/min to 200 mL/min; and 6) sintering the annealed powder to obtain a thermoelectric material including an iron-sulfur compound.

A method of preparing a thermoelectric material comprising an iron-sulfur compound, the method including: 1) weighing, grinding, and mixing an iron salt and a sulfur-containing source to obtain a mixed powder; 2) carrying out a hydrothermal reaction with the mixed powder to obtain a black precipitate; 3) washing the precipitate; 4) drying the precipitate under vacuum to obtain FeS.sub.2 powder; 5) annealing the FeS.sub.2 powder under inert atmosphere to obtain annealed powder, where a heating temperature is from 300 C. to 1000 C., a heating time is from 2 hours to 24 hours, and a flow rate of an inert gas is from 30 mL/min to 200 mL/min; and 6) sintering the annealed powder to obtain a thermoelectric material including an iron-sulfur compound.